Battery-grade high-purity lithium carbonate purification equipment and preparation process thereof

Abstract

The application provides a battery-grade high-purity lithium carbonate purification device and a preparation process thereof, and relates to the technical field of lithium carbonate preparation. The device comprises a purification box, a purification mechanism and a material turning mechanism. The purification mechanism comprises a first mounting frame mounted on the side wall of the purification box. A purification motor is mounted on the outer wall of the first mounting frame through bolts. A ratchet wheel is connected to the output shaft key groove of the purification motor. A ratchet sleeve is connected to the outer wall of the ratchet wheel. A first pulley is connected to the outer wall key groove of the ratchet sleeve. A mixing frame is connected to the key groove inside the purification box at the shaft center of the ratchet wheel. The mixing frame can drive the refined leaching solution in the purification box to mix with the composite impurity removal agent in all directions and at multiple angles, thereby significantly improving the purity of the primary purified solution. The material turning plate under the mixing frame can completely turn up and scatter the materials attached to the bottom and the wall of the purification box, so that the accumulated materials can fully contact with the complex impurity removal agent, thereby laying a good foundation for the subsequent ion exchange resin impurity removal.

Description

Technical Field

[0001] This invention relates to the field of lithium carbonate preparation, and more particularly to a battery-grade high-purity lithium carbonate purification device and its preparation process. Background Technology

[0002] Battery-grade lithium carbonate, as the core raw material of lithium-ion batteries, has been widely used in various technological fields. With the upgrading of electronic products such as computers, mobile phones, and digital cameras, the battery industry has become the largest consumer of lithium with the greatest potential. Under the boom in the production of new energy vehicles, the battery industry's demand for the quantity and quality of basic lithium salts such as lithium carbonate, lithium hydroxide, lithium fluoride, and lithium chloride is also increasing.

[0003] As a core strategic metal in the fields of new energy and high-end manufacturing, the demand for lithium has grown exponentially with the development of industries such as lithium-ion batteries and new energy vehicles. Lithium carbonate and lithium hydroxide are used as additives in the battery industry for alkaline batteries, which can extend their lifespan and increase their storage capacity. Battery-grade lithium carbonate is the core raw material for producing cathode materials for ternary lithium batteries.

[0004] In the existing technology, during the preparation of the primary purification solution, the mixing uniformity of the composite impurity remover and the refined leachate is poor, resulting in insufficient impurity removal reaction. After adding the complexing impurity remover to the primary purification solution, the existing stirring method can only act on the upper and middle layers of the solution in the purification tank, and cannot reach the materials attached to the bottom and walls of the tank, which affects the purity of the secondary purification solution and is not conducive to the subsequent preparation of high-purity lithium sulfate purification solution.

[0005] Therefore, it is necessary to provide a battery-grade high-purity lithium carbonate purification device and its preparation process to solve the above-mentioned technical problems. Summary of the Invention

[0006] This invention provides a battery-grade high-purity lithium carbonate purification device and its preparation process, which solves the problem in related technologies that the mixing uniformity of the composite impurity remover and the refined leachate is poor during the preparation of the primary purification solution, and that adding a complexing impurity remover to the primary purification solution can easily affect the purity of the secondary purification solution, which is not conducive to the subsequent preparation of high-purity lithium sulfate purification solution.

[0007] To solve the above-mentioned technical problems, the present invention provides a battery-grade high-purity lithium carbonate purification device, including a purification chamber, a purification mechanism, and a material turning mechanism;

[0008] The purification mechanism includes a first mounting bracket installed on the side wall of the purification chamber. A purification motor is bolted to the outer wall of the first mounting bracket. A ratchet is connected to the output shaft of the purification motor via a keyway. A ratchet sleeve is meshed to the outer wall of the ratchet. A first pulley is connected to the outer wall of the ratchet sleeve via a keyway. A mixing frame is connected to the ratchet shaft at a keyway inside the purification chamber.

[0009] The material turning mechanism includes a second mounting frame installed on the side wall of the purification chamber and located on one side of the first mounting frame. A second pulley is rotatably connected inside the second mounting frame. A belt is sleeved on the outer wall of the first pulley and the second pulley. An eccentric plate is connected to the keyway at the center of the second pulley. A guide wheel is rotatably connected to the outer wall of the eccentric plate. A drive rod is rotatably connected inside the purification chamber and located below the mixing rack. A material turning plate and a turning groove plate are respectively fixed at both ends of the drive rod.

[0010] Preferably, both ends of the mixing rack are rotatably connected to the inside of the purification chamber via bearings, and the outer wall of the ratchet sleeve is rotatably connected to the side wall of the purification chamber via bearings.

[0011] Preferably, the guide wheel is embedded in the inner groove of the flipping groove plate, and the outer wall of the guide wheel and the inner wall of the flipping groove plate are in contact with each other.

[0012] Preferably, the drive rod, the eccentric plate, and the second pulley are located on the same axis.

[0013] Preferably, it also includes a moving mechanism and a feeding mechanism;

[0014] The moving mechanism includes a top plate fixed to the top of the purification chamber, a guide rail and a rack fixed to the top of the top plate, a moving plate slidably connected to the upper surface of the top plate and on the opposite side of the guide rail and the rack, a moving motor mounted on the top of the moving plate, a positioning frame fixed to one side of the moving plate, and moving gears and rollers connected to the keyways of the output shafts at both ends of the moving motor.

[0015] The feeding mechanism includes a mounting plate fixed to one side of the moving plate and away from the positioning frame. A storage tank is fixedly installed inside the mounting plate. A rotating frame is rotatably connected inside the storage tank. A second gear and a scraper are fixedly installed at the upper and lower ends of the rotating frame, respectively. A key rod is connected to the shaft of the moving gear via a keyway. A first gear is connected to one end of the key rod, which is located above the second gear, via a keyway.

[0016] Preferably, the moving gear and rack mesh with each other, the outer wall of the roller and the inner wall of the guide rail are in contact with each other, and the two ends of the roller are rotatably connected to the positioning frame.

[0017] Preferably, the first gear and the second gear mesh with each other, and the outer wall of the scraper and the inner wall of the storage tank are in contact with each other.

[0018] Preferably, a telescopic tube is installed on the outer wall of the storage tank, a conical tube is installed at the outer end of the telescopic tube, and a feed pipe is installed on the top of the purification box in the same horizontal direction as the telescopic tube.

[0019] The process for preparing battery-grade high-purity lithium carbonate includes the following steps:

[0020] S1: Concentrate modification pretreatment;

[0021] The lithium feldspar concentrate was mixed evenly with flux, roasted in a muffle furnace, cooled and ground to obtain the modified concentrate.

[0022] S2: Low excess sulfuric acid roasting;

[0023] The modified concentrate was mixed with concentrated H2SO4 and roasted in a rotary roasting furnace. The roasted product was cooled and then ground to obtain roasted mineral powder.

[0024] S3: Constant temperature oscillating water immersion;

[0025] Roasted mineral powder is added to distilled water and leached in a constant temperature oscillating leaching apparatus. After leaching, it is filtered under vacuum to obtain lithium sulfate leachate. The filtrate is filtered through a microfiltration membrane to remove impurities and obtain refined leachate.

[0026] S4: Synergistic purification with compound reagents;

[0027] A composite impurity remover is added to the refined leachate, and after standing and settling, it is filtered to obtain a primary purified solution. A complexing impurity remover is added to the primary purified solution to obtain a secondary purified solution. The secondary purified solution is then adsorbed and purified by an ion exchange resin column to obtain a high-purity lithium sulfate purified solution. The purification process needs to be carried out in a battery-grade high-purity lithium carbonate purification device.

[0028] S5: Lithium-directed enrichment;

[0029] High-purity lithium sulfate purified solution is pumped into a nanofiltration membrane separation system for nanofiltration enrichment to obtain lithium-rich solution. The nanofiltration permeate is then treated by reverse osmosis and recycled to the water leaching process as leachate, thus realizing water resource recycling.

[0030] S6: Hot alkaline washing and multi-stage washing to precipitate lithium carbonate;

[0031] Under heating conditions, a hot saturated Na2CO3 solution was added to the lithium-rich solution, and the mixture was stirred and matured at a constant temperature to obtain a crude lithium carbonate precipitate.

[0032] High-purity lithium carbonate wet product is obtained by three-stage hot alkaline washing of the crude lithium carbonate precipitate. The three-stage washing filtrates are collected separately. The first and second-stage washing filtrates are recycled to the lithium-rich solution concentration process. The third-stage washing filtrate is recycled after distillation to recover ethanol.

[0033] S7: Product crystallization and drying;

[0034] The wet lithium carbonate sample was pre-dried in a vacuum drying oven, then heated to a constant temperature for drying to complete crystallization and shaping. After cooling, a high-purity lithium carbonate product was obtained.

[0035] Compared with related technologies, the battery-grade high-purity lithium carbonate purification equipment and its preparation process provided by this invention have the following beneficial effects:

[0036] The purification unit can improve the mixing uniformity of the primary purification solution preparation, ensuring sufficient impurity removal reaction. The rotation of the mixing rack can drive the purified leachate and composite impurity removal agent in the purification chamber to be stirred and mixed in all directions and from multiple angles, avoiding the problem of uneven local reagent concentration, significantly improving the purity of the primary purification solution, and reducing the load of subsequent complexation impurity removal.

[0037] Secondly, the material-turning plate rotates synchronously below the mixing rack, which can thoroughly turn over and disperse the material attached to the bottom and walls of the purification box, so that the accumulated material can fully contact the complexing and impurity-removing agent, greatly improving the purity of the secondary purification solution, laying a good foundation for the subsequent deep impurity removal by ion exchange resin, and ultimately ensuring the preparation quality of high-purity lithium sulfate purification solution. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0039] Figure 1 The optimal structural schematic diagram provided for this invention;

[0040] Figure 2 for Figure 1 The diagram shows a side view of the structure.

[0041] Figure 3 for Figure 2 The enlarged structural diagram at point A is shown below;

[0042] Figure 4 for Figure 1 The diagram shows a detailed structural schematic of the purification mechanism.

[0043] Figure 5 for Figure 5 The enlarged structural diagram at point B is shown below;

[0044] Figure 6 for Figure 1 The diagram shows a detailed structural schematic of the material turning mechanism.

[0045] Figure 7 for Figure 6 The diagram shows a side view of the structure.

[0046] Figure 8 This is a cross-sectional view of the feeding mechanism provided by the present invention;

[0047] Figure 9 The process flow diagram for preparing battery-grade high-purity lithium carbonate provided by this invention.

[0048] Explanation of icon numbers:

[0049] 1. Purification chamber;

[0050] 2. Purification mechanism; 21. First mounting frame; 22. Purification motor; 23. Ratchet; 24. Ratchet sleeve; 25. First pulley; 26. Belt; 27. Mixing frame;

[0051] 3. Tilting mechanism; 31. Second mounting bracket; 32. Second pulley; 33. Eccentric plate; 34. Guide wheel; 35. Tilting trough plate; 36. Drive rod; 37. Tilting plate.

[0052] 4. Moving mechanism; 41. Top plate; 42. Rack; 43. Guide rail; 44. Moving plate; 45. Moving motor; 46. Positioning frame; 47. Moving gear; 48. Roller.

[0053] 5. Feeding mechanism; 51. Mounting plate; 52. Storage tank; 53. Key rod; 54. First gear; 55. Second gear; 56. Rotating frame; 57. Scraper; 58. Telescopic tube; 59. Conical tube.

[0054] 6. Feed pipe. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0056] This invention provides a battery-grade high-purity lithium carbonate purification device and its preparation process.

[0057] First embodiment:

[0058] Please see Figure 1 , Figures 4 to 7 A battery-grade high-purity lithium carbonate purification device includes a purification chamber 1, a purification mechanism 2, and a material turning mechanism 3;

[0059] The purification mechanism 2 includes a first mounting bracket 21 installed on the side wall of the purification chamber 1. A purification motor 22 is bolted to the outer wall of the first mounting bracket 21. A ratchet 23 is connected to the output shaft of the purification motor 22 via a keyway. A ratchet sleeve 24 is meshed to the outer wall of the ratchet 23. A first pulley 25 is connected to the outer wall of the ratchet sleeve 24 via a keyway. A mixing frame 27 is connected to the axis of the ratchet 23 and located inside the purification chamber 1 via a keyway.

[0060] The material turning mechanism 3 includes a second mounting frame 31 installed on the side wall of the purification box 1 and located on one side of the first mounting frame 21. A second pulley 32 is rotatably connected inside the second mounting frame 31. A belt 26 is sleeved on the outer wall of the first pulley 25 and the second pulley 32. An eccentric plate 33 is connected to the axis of the second pulley 32 via a keyway. A guide wheel 34 is rotatably connected to the outer wall of the eccentric plate 33. A drive rod 36 is rotatably connected inside the purification box 1 and located below the mixing frame 27. A material turning plate 37 and a turning groove plate 35 are respectively fixed at both ends of the drive rod 36.

[0061] Both ends of the mixing rack 27 are rotatably connected to the interior of the purification chamber 1 via bearings, and the outer wall of the ratchet sleeve 24 is rotatably connected to the side wall of the purification chamber 1 via bearings.

[0062] The guide wheel 34 is embedded in the inner groove of the flipping groove plate 35, and the outer wall of the guide wheel 34 and the inner wall of the flipping groove plate 35 are in contact with each other.

[0063] The drive rod 36, the eccentric plate 33, and the second pulley 32 are on the same axis.

[0064] Please see Figure 1 The refined leachate is directly injected into the purification chamber 1. During the purification process, the refined leachate, the compound impurity remover, and the complexing impurity remover all react and work within the purification chamber 1.

[0065] Please see Figure 4 and Figure 5 When the refined leachate and the compound impurity remover are mixed, the user starts the purification motor 22 to rotate clockwise. When it rotates clockwise, it drives the ratchet 23 and the mixing frame 27 to rotate. The rotation of the mixing frame 27 in the purification chamber 1 will fully and evenly mix the refined leachate and the compound impurity remover.

[0066] Since the ratchet 23 rotates clockwise, the clockwise rotation of the ratchet 23 will not control the rotation of the ratchet sleeve 24. Therefore, during the process of purifying the refined leachate and the compound impurity removal agent into a primary purified solution, the turning mechanism 3 will not be controlled to start working.

[0067] Please see Figure 6 and Figure 7 When the refined leachate and the complexing impurity removal agent are mixed, the user needs to control the purification motor 22 to rotate counterclockwise. At this time, the mixing frame 27 can not only rotate, but the ratchet 23 will also control the ratchet sleeve 24 to rotate when it rotates counterclockwise. When the ratchet sleeve 24 rotates, it drives the first pulley 25 and the transmission belt 26 to control the second pulley 32 to drive the eccentric plate 33 so that the guide wheel 34 on the eccentric plate 33 rotates around the axis of the second pulley 32.

[0068] During the rotation of the guide wheel 34 within the tilting tank 35, the tilting tank 35 is controlled by force to rotate in a circular motion. During the tilting process, the transmission drive rod 36 controls the tilting plate 37 to form a fan-shaped tilting motion below the purification box 1 and the mixing rack 27, thereby tilting the precipitate at the bottom of the purification box 1 during the primary purification stage upward to participate in the complexing and impurity removal agent to generate the secondary purification solution.

[0069] In one application scenario, the battery-grade high-purity lithium carbonate purification equipment can be used to purify and extract lithium from crude lithium sulfate solution obtained from lithium extraction from salt lake brine.

[0070] When purifying the crude lithium sulfate solution obtained from lithium extraction from salt lake brine, the crude lithium sulfate solution obtained from lithium extraction from salt lake brine is directly injected into purification tank 1 for purification. The specific purification process is as described above.

[0071] In another application, the battery-grade high-purity lithium carbonate purification equipment can also be used to purify and extract lithium from crude lithium leachate after roasting and leaching lithium ores such as spodumene and lepidolite.

[0072] This embodiment:

[0073] Purification unit 2 can improve the mixing uniformity of the primary purification solution preparation, ensuring sufficient impurity removal reaction. The rotation of mixing rack 27 can drive the purified leachate and composite impurity removal agent in the purification box 1 to be stirred and mixed in all directions and from multiple angles, avoiding the problem of uneven local reagent concentration, significantly improving the purity of the primary purification solution, and reducing the load of subsequent complexation impurity removal.

[0074] Secondly, the material turning plate 37 flips and turns the material simultaneously below the mixing rack 27, which can thoroughly turn up and disperse the material attached to the bottom and walls of the purification box 1, so that the accumulated material can fully contact the complexing impurity removal agent, greatly improve the purity of the secondary purification solution, lay a good foundation for the subsequent deep impurity removal of ion exchange resin, and ultimately ensure the preparation quality of high-purity lithium sulfate purification solution.

[0075] The composite reagent synergistic purification finally yielded a high-purity lithium sulfate purified solution. The purity of the subsequently prepared lithium carbonate can stably reach the battery-grade standard, avoiding problems such as increased internal resistance, decreased cycle life, reduced capacity, and decreased rate performance caused by impurities being introduced into the lithium battery cathode material.

[0076] Second embodiment:

[0077] Please see Figure 2 , Figure 3 and Figure 8 It also includes a moving mechanism 4 and a feeding mechanism 5;

[0078] The moving mechanism 4 includes a top plate 41 fixed to the top of the purification chamber 1. A guide rail 43 and a rack 42 are fixed to the top of the top plate 41. A moving plate 44 is slidably connected to the upper surface of the top plate 41 and located on the opposite side of the guide rail 43 and the rack 42. A moving motor 45 is installed on the top of the moving plate 44. A positioning frame 46 is fixed to one side of the moving plate 44. The output shafts at both ends of the moving motor 45 are connected to moving gears 47 and rollers 48 via keyways.

[0079] The feeding mechanism 5 includes a mounting plate 51 fixed to one side of the moving plate 44 and away from the positioning frame 46. A storage tank 52 is fixedly installed inside the mounting plate 51. A rotating frame 56 is rotatably connected inside the storage tank 52. A second gear 55 and a scraper 57 are fixedly installed at the upper and lower ends of the rotating frame 56, respectively. A key rod 53 is connected to the shaft of the moving gear 47 via a keyway. A first gear 54 is connected to one end of the key rod 53, which is located above the second gear 55, via a keyway.

[0080] The moving gear 47 and the rack 42 mesh with each other, the outer wall of the roller 48 and the inner wall of the guide rail 43 are in contact with each other, and the two ends of the roller 48 are rotatably connected to the positioning frame 46.

[0081] The first gear 54 and the second gear 55 mesh with each other, and the outer wall of the scraper 57 and the inner wall of the storage tank 52 are in contact with each other.

[0082] Please see Figure 2 , Figure 3 and Figure 8 When the composite impurity removal agent is fed, the user starts the moving motor 45 to drive the moving gear 47 and roller 48 to rotate. During the rotation of the moving gear 47, it meshes with the rack 42 to drive the moving plate 44 and the mounting plate 51 to move freely on the purification box 1. At the same time, the roller 48 rotates on the guide rail 43 to assist the moving plate 44 to move on the top plate 41. During the movement, the user can control the feeding mechanism 5 to move back and forth.

[0083] Simultaneously, during the rotation of the moving gear 47, the transmission key rod 53 drives the first gear 54 to mesh with the second gear 55, controlling the rotating frame 56 to rotate within the storage tank 52. The rotating frame 56 can evenly mix the composite impurity remover and the complexing impurity remover within the storage tank 52. During the rotation of the rotating frame 56, the scraper 57 can remove the residue of the composite impurity remover and the complexing impurity remover within the storage tank 52.

[0084] This embodiment:

[0085] The reciprocating mobile auxiliary feeding system allows the composite impurity remover and the complexing impurity remover to be evenly distributed along the length of the purification tank 1, avoiding the problems of local accumulation and uneven dispersion of reagents caused by traditional fixed-point feeding. This ensures that the reagents and the purification solution come into rapid and comprehensive contact, giving full play to the synergistic flocculation and precipitation effects of the composite impurity remover and the deep complexing effect of the complexing impurity remover. Simultaneously, the inner wall is scraped during the reciprocating feeding process, which can promptly remove reagent clumps, impurity precipitates and material residues attached to the inner wall of the storage tank 52, preventing such deposits from dissolving and falling off after long-term accumulation, thus avoiding secondary contamination of the purification solution.

[0086] Third embodiment:

[0087] Please see Figure 2 , Figure 3 and Figure 8 The storage tank 52 is equipped with a telescopic pipe 58 on its outer wall, and a conical pipe 59 is installed at the outer end of the telescopic pipe 58. A feed pipe 6 is installed on the top of the purification box 1 and in the same horizontal direction as the telescopic pipe 58.

[0088] Please see Figure 2 , Figure 3 and Figure 8 During the transition from primary to secondary purification, the storage tank 52 can be moved toward the feed pipe 6. When the cone tube 59 enters the outlet position of the feed pipe 6, the outer wall of the cone tube 59 will be tightly fitted with the inner wall of the outlet of the feed pipe 6, while the telescopic tube 58 is in a contracted state. At this time, the user can supply the complexing impurity removal agent into the storage tank 52 through the feed pipe 6.

[0089] This embodiment:

[0090] The automated and seamless switching of impurity removal reagents ensures the continuity of the process from the preparation of the primary purification solution to the preparation of the secondary purification solution, stabilizes the two-stage impurity removal reaction sequence, and ensures that calcium and magnesium ions and heavy metal impurities are fully and stepwise removed, thus guaranteeing the purity of battery-grade lithium carbonate raw materials and avoiding the impact of impurity residues on the performance of lithium battery cathode materials.

[0091] The automatic switching between the two impurity removal agent feeding channels can prevent external air, dust, and impurities from entering the storage tank 52, avoid introducing secondary pollutants into the system, and reduce the amount of residual composite impurity removal agent mixed into the complexation and impurity removal stage, further improving the cleanliness of the secondary purification solution and meeting the requirements for the preparation of high-purity lithium battery raw materials.

[0092] The process for preparing battery-grade high-purity lithium carbonate includes the following steps:

[0093] S1: Concentrate modification pretreatment;

[0094] The lithium feldspar concentrate and flux were mixed evenly at a mass ratio of 100:(2~5), placed in a muffle furnace and heated to 1050~1100℃ at a heating rate of 5~8℃ / min, and calcined at a constant temperature for 1.5~2h. After cooling, the mixture was ground until the particle size was less than 60μm to obtain the modified concentrate. The flux was a compound of sodium pyrosulfate and calcium fluoride at a mass ratio of 3:1.

[0095] S2: Low excess sulfuric acid roasting;

[0096] The modified concentrate was mixed with concentrated H2SO4 at a liquid-solid ratio of (0.8~1.0):1, with the amount of concentrated H2SO4 added being 105%~110% of the lithium equivalent. The mixture was placed in a rotary roasting furnace and dynamically roasted at 280~300℃ for 45~60 min. After cooling, the roasted product was ground to a particle size of less than 60 μm to obtain roasted ore powder. The dynamic roasting speed was 10~15 r / min to enhance solid-liquid contact.

[0097] S3: Constant temperature oscillating water immersion;

[0098] Roasted mineral powder was added to distilled water, and the solid-liquid ratio was controlled at 1:(8~10) (g / mL). The mixture was placed in a constant temperature shaking leaching apparatus and leached for 40~50 min at 45~50℃ and shaking rate of 200~250 r / min. After leaching, the mixture was vacuum filtered to obtain lithium sulfate leachate. The filtrate was filtered through a microfiltration membrane (0.22μm) to remove impurities and obtain refined leachate.

[0099] S4: Synergistic purification with compound reagents;

[0100] Add a composite impurity removal agent to the refined leachate, react for 30-40 min at 30-40℃ and stirring speed of 200-300 rpm, adjust the pH of the solution to 6.0-6.5, let it stand for 20-30 min to precipitate, and then filter to obtain the first purified solution.

[0101] The composite impurity remover is a compound of CaCO3-kaolin-polyaluminum ferric silicate with a mass ratio of 10:2:1, and the addition amount is 1.0%~1.5% of the mass of the leachate.

[0102] Add a complexing impurity remover to the primary purification solution, adjust the pH to 10.5-11.0, stir and react at 35-40℃ for 20-30 min, let it stand to precipitate for 15-20 min, and then filter to obtain the secondary purification solution. The complexing impurity remover is a compound of anhydrous sodium carbonate and disodium ethylenediaminetetraacetate (EDTA-2Na) in a mass ratio of 8:1, and the amount added is 0.8%-1.2% of the mass of the primary purification solution. The purification should be carried out in a battery-grade high-purity lithium carbonate purification device.

[0103] The pH of the secondary purification solution was adjusted to 7.0-7.5 using 0.5 mol / L dilute H2SO4, and then purified by adsorption using an ion exchange resin column to obtain a high-purity lithium sulfate purified solution. The ion exchange resin was a chelating lithium-selective resin with a flow rate of 1-2 BV / h.

[0104] S5: Lithium-directed enrichment;

[0105] High-purity lithium sulfate purified solution is pumped into a nanofiltration membrane separation system and enriched by nanofiltration under operating pressure of 1.5~2.0MPa and temperature of 30~35℃ to obtain lithium-rich solution with Li concentration ≥15g / L. The nanofiltration permeate is then recycled to the water leaching process as leaching water after reverse osmosis treatment, thus realizing water resource recycling.

[0106] S6: Hot alkaline washing and multi-stage washing to precipitate lithium carbonate;

[0107] The lithium-rich solution was heated to 95-100℃, and a hot saturated Na2CO3 solution with a mass concentration of 20%-30% was added dropwise at a stirring speed of 300-350 rpm. The dropwise acceleration rate was 5-8 mL / min. The reaction continued until no white precipitate was produced in the solution. The mixture was then stirred at a constant temperature for 15-20 min to obtain a crude lithium carbonate precipitate.

[0108] The crude lithium carbonate precipitate was subjected to a three-stage hot alkaline washing process: the first stage washing was performed with a 0.5% dilute Na₂CO₃ solution at 95-100℃, with a liquid-to-solid ratio of 5:1, and the mixture was stirred for 10 min before filtration; the second stage washing was performed with distilled water at 95-100℃, with a liquid-to-solid ratio of 4:1, and the mixture was stirred for 8 min before filtration; the third stage washing was performed with an anhydrous ethanol-water solution at 95-100℃ (ethanol:water = 1:3), with a liquid-to-solid ratio of 3:1, and the mixture was stirred for 5 min before filtration, yielding high-purity wet lithium carbonate. The filtrates from the three stages of washing were collected separately. The filtrates from the first and second stages of washing were recycled to the lithium-rich solution concentration process, while the filtrate from the third stage of washing was recycled after ethanol recovery by distillation.

[0109] S7: Product crystallization and drying;

[0110] The wet lithium carbonate product is placed in a vacuum drying oven and pre-dried for 1 to 1.5 hours at 80 to 90°C and a vacuum of -0.08 to -0.09 MPa. Then, the temperature is raised to 240 to 250°C and dried at a constant temperature for 2 to 2.5 hours to complete the crystallization and shaping. After cooling, a high-purity lithium carbonate product is obtained.

[0111] This process:

[0112] This invention enhances the phase transformation efficiency and reaction contact with sulfuric acid of lepidolite by combining flux modification pretreatment with dynamic rotary calcination. The lithium leaching rate can still reach more than 98%, which is more than 0.7% higher than the prior art, while reducing reagent consumption and energy consumption.

[0113] A synergistic purification process employing composite impurity removers, complexing impurity removers, and lithium-selective ion exchange resins is adopted to achieve deep and simultaneous removal of impurities such as Fe, Al, Mg, and Ca. This avoids the problem of poor synergy in traditional stepwise single-agent impurity removal, and reduces the lithium loss rate during the purification process to below 3%, which is more than 4.64% lower than existing technologies.

[0114] Adding a nanofiltration membrane directional enrichment process to increase the Li concentration to ≥15g / L not only improves the precipitation rate and crystallinity of lithium carbonate, but also enables the recycling of water resources and reduces the energy consumption of subsequent evaporation and concentration.

[0115] The innovative three-stage hot alkaline washing method replaces the traditional single hot water washing, effectively removing residual sodium salt impurities such as Na2SO4 and excess Na2CO3, thereby increasing the purity of lithium carbonate products to ≥99.5%, which is more than 0.3% higher than existing technologies.

[0116] The total lithium recovery rate is increased to over 90%, which is more than 4% higher than the existing technology, and the raw material loss is significantly reduced. The nanofiltration permeate is then reverse osmotically leached, the washing filtrate is circulated and concentrated, and the mother liquor is directionally enriched and reused.

[0117] The parameters of each process step can be flexibly adjusted according to the grade of the lithium feldspar concentrate, making it highly adaptable. Furthermore, it adopts mature industrial equipment such as rotary roasting, constant temperature oscillation leaching, and membrane separation, which makes it easy to achieve industrial scale-up. The operation is simple and has good repeatability.

[0118] Please refer to the reference again. Figures 1 to 9 The working principle of the battery-grade high-purity lithium carbonate purification equipment and its preparation process provided by this invention is as follows:

[0119] Step S1: Start the moving motor 45 to drive the moving gear 47 and roller 48 to rotate. During the rotation of the moving gear 47, it meshes with the rack 42 to drive the moving plate 44 and the mounting plate 51 to move freely on the purification box 1. At the same time, the roller 48 rotates on the guide rail 43 to assist the moving plate 44 to move on the top plate 41. During the movement, the user can control the feeding mechanism 5 to move back and forth.

[0120] Simultaneously, during the rotation of the moving gear 47, the transmission key 53 drives the first gear 54 to mesh with the second gear 55, controlling the rotating frame 56 to rotate within the storage tank 52. The rotating frame 56 can uniformly mix the composite impurity remover and the complexing impurity remover in the storage tank 52. During the rotation of the rotating frame 56, the scraper 57 can remove the residue of the composite impurity remover and the complexing impurity remover in the storage tank 52. The feeding mechanism 5 feeds the composite impurity remover and the complexing impurity remover into the purification box 1.

[0121] In step S2, the refined leachate is directly injected into the purification chamber 1. During the purification process, the refined leachate, the composite impurity remover, and the complexing impurity remover all react and purify within the purification chamber 1.

[0122] When the refined leachate and the compound impurity remover are mixed, the user starts the purification motor 22 to rotate clockwise. When the clockwise rotation is performed, it drives the ratchet 23 and the mixing frame 27 to rotate. The rotation of the mixing frame 27 in the purification chamber 1 will fully and evenly mix the refined leachate and the compound impurity remover.

[0123] When the refined leachate and the complexing impurity removal agent are mixed, the user needs to control the purification motor 22 to rotate counterclockwise. At this time, the mixing frame 27 can not only rotate, but also the ratchet 23 will control the ratchet sleeve 24 to rotate when it rotates counterclockwise. When the ratchet sleeve 24 rotates, it drives the first pulley 25 and the transmission belt 26 to control the second pulley 32 to drive the eccentric plate 33 to make the guide wheel 34 on the eccentric plate 33 rotate around the axis of the second pulley 32.

[0124] During the rotation of the guide wheel 34 within the tilting tank 35, the tilting tank 35 is controlled by force to rotate in a circular motion. During the tilting process, the transmission drive rod 36 controls the tilting plate 37 to form a fan-shaped tilting motion below the purification box 1 and the mixing rack 27, thereby tilting the precipitate at the bottom of the purification box 1 during the primary purification stage upward to participate in the complexing and impurity removal agent to generate the secondary purification solution.

[0125] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made under the concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A battery-grade high-purity lithium carbonate purification device, characterized in that, Includes a purification chamber, purification mechanism, and material turning mechanism; The purification mechanism includes a first mounting bracket installed on the side wall of the purification chamber. A purification motor is bolted to the outer wall of the first mounting bracket. A ratchet is connected to the output shaft of the purification motor via a keyway. A ratchet sleeve is meshed to the outer wall of the ratchet. A first pulley is connected to the outer wall of the ratchet sleeve via a keyway. A mixing frame is connected to the ratchet shaft at a keyway inside the purification chamber. The material turning mechanism includes a second mounting frame installed on the side wall of the purification chamber and located on one side of the first mounting frame. A second pulley is rotatably connected inside the second mounting frame. A belt is sleeved on the outer wall of the first pulley and the second pulley. An eccentric plate is connected to the keyway at the center of the second pulley. A guide wheel is rotatably connected to the outer wall of the eccentric plate. A drive rod is rotatably connected inside the purification chamber and located below the mixing rack. A material turning plate and a turning groove plate are respectively fixed at both ends of the drive rod.

2. The battery-grade high-purity lithium carbonate purification equipment according to claim 1, characterized in that, Both ends of the mixing rack are rotatably connected to the inside of the purification chamber via bearings, and the outer wall of the ratchet sleeve is rotatably connected to the side wall of the purification chamber via bearings.

3. The battery-grade high-purity lithium carbonate purification equipment according to claim 1, characterized in that, The guide wheel is embedded in the inner groove of the flipping groove plate, and the outer wall of the guide wheel and the inner wall of the flipping groove plate are in contact with each other.

4. The battery-grade high-purity lithium carbonate purification equipment according to claim 1, characterized in that, The drive rod, eccentric plate, and second pulley are on the same axis.

5. The battery-grade high-purity lithium carbonate purification equipment according to claim 1, characterized in that, It also includes a moving mechanism and a feeding mechanism; The moving mechanism includes a top plate fixed to the top of the purification chamber, a guide rail and a rack fixed to the top of the top plate, a moving plate slidably connected to the upper surface of the top plate and on the opposite side of the guide rail and the rack, a moving motor mounted on the top of the moving plate, a positioning frame fixed to one side of the moving plate, and moving gears and rollers connected to the keyways of the output shafts at both ends of the moving motor. The feeding mechanism includes a mounting plate fixed to one side of the moving plate and away from the positioning frame. A storage tank is fixedly installed inside the mounting plate. A rotating frame is rotatably connected inside the storage tank. A second gear and a scraper are fixedly installed at the upper and lower ends of the rotating frame, respectively. A key rod is connected to the shaft of the moving gear via a keyway. A first gear is connected to one end of the key rod, which is located above the second gear, via a keyway.

6. The battery-grade high-purity lithium carbonate purification equipment according to claim 5, characterized in that, The moving gear and rack mesh with each other, the outer wall of the roller and the inner wall of the guide rail are in contact with each other, and the two ends of the roller are rotatably connected to the positioning frame.

7. The battery-grade high-purity lithium carbonate purification equipment according to claim 5, characterized in that, The first gear and the second gear mesh with each other, and the outer wall of the scraper and the inner wall of the storage tank are in contact with each other.

8. The battery-grade high-purity lithium carbonate purification equipment according to claim 7, characterized in that, The storage tank is equipped with a telescopic pipe on its outer wall, and a conical pipe is installed at the outer end of the telescopic pipe. A feed pipe is installed at the top of the purification box and in the same horizontal direction as the telescopic pipe.

9. A process for preparing battery-grade high-purity lithium carbonate, characterized in that, Includes the following steps: S1: Concentrate modification pretreatment; The lithium feldspar concentrate was mixed evenly with flux, roasted in a muffle furnace, cooled and ground to obtain the modified concentrate. S2: Low excess sulfuric acid roasting; The modified concentrate was mixed with concentrated H2SO4 and roasted in a rotary roasting furnace. The roasted product was cooled and then ground to obtain roasted mineral powder. S3: Constant temperature oscillating water immersion; Roasted mineral powder is added to distilled water and leached in a constant temperature oscillating leaching apparatus. After leaching, it is vacuum filtered to obtain lithium sulfate leachate. The filtrate is filtered through a microfiltration membrane to remove impurities and obtain refined leachate. S4: Synergistic purification with compound reagents; A composite impurity remover is added to the refined leachate, and after standing and settling, the solution is filtered to obtain a primary purified solution. A complexing impurity remover is added to the primary purified solution to obtain a secondary purified solution. The solution is then purified by adsorption on an ion exchange resin column to obtain a high-purity lithium sulfate purified solution. The purification process is carried out in the battery-grade high-purity lithium carbonate purification equipment as described in any one of claims 1-8. S5: Lithium-directed enrichment; High-purity lithium sulfate purified solution is pumped into a nanofiltration membrane separation system for nanofiltration enrichment to obtain lithium-rich solution. The nanofiltration permeate is then treated by reverse osmosis and recycled to the water leaching process as leachate, thus realizing water resource recycling. S6: Hot alkaline washing and multi-stage washing to precipitate lithium carbonate; Under heating conditions, a hot saturated Na2CO3 solution was added to the lithium-rich solution, and the mixture was stirred and matured at a constant temperature to obtain a crude lithium carbonate precipitate. High-purity lithium carbonate wet product is obtained by three-stage hot alkaline washing of the crude lithium carbonate precipitate. The three-stage washing filtrates are collected separately. The first and second-stage washing filtrates are recycled to the lithium-rich solution concentration process. The third-stage washing filtrate is recycled after distillation to recover ethanol. S7: Product crystallization and drying; The wet lithium carbonate sample was pre-dried in a vacuum drying oven, then heated to a constant temperature for drying to complete crystallization and shaping. After cooling, a high-purity lithium carbonate product was obtained.

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