Lithium carbonate preparation process by alkali purification reactor, secondary spodumene pulp, calcium and magnesium removal and calcium and magnesium removal

Abstract

The application provides an alkaliization and impurity removal reaction kettle and a process for preparing lithium carbonate by secondary pulping and calcium-magnesium removal of spodumene, relates to the technical field of battery-grade lithium carbonate preparation, and comprises an impurity removal kettle, a mounting seat, a stirring mechanism, a driving mechanism and a caustic soda feeding mechanism. The stirring mechanism is arranged in the interior of the impurity removal kettle and is used for mixing high-lithium brine and sodium hydroxide solids and comprises a stirring shaft which is vertically and rotationally connected to the interior of the mounting seat. The scheme finally realizes the forward and reverse rotation of the driving and feeding gear, intermittently opens and closes the sealing plate, realizes the quantitative and batch feeding of caustic soda, the feeding frequency is adaptively changed with the stirring speed, effectively avoids local overheating, bottom sedimentation and lithium co-precipitation loss caused by one-time large amount of caustic soda feeding, simultaneously reduces the floating and splashing of caustic soda, guarantees the rapid dispersion of the caustic soda in the brine, makes magnesium, iron and manganese form hydroxide precipitates which are coarse and easy to filter, and significantly improves the impurity removal efficiency and lithium recovery rate.

Description

Technical Field

[0001] This invention relates to the field of battery-grade lithium carbonate preparation, and more particularly to an alkali-removal reactor and a process for preparing lithium carbonate by secondary pulping of spodumene to remove calcium and magnesium. Background Technology

[0002] Battery-grade lithium carbonate is a key raw material for manufacturing cathode materials for lithium-ion batteries, and its purity directly determines the electrochemical performance, safety, and cycle life of lithium batteries. In the spodumene sulfuric acid process for lithium extraction, calcium and magnesium are the main impurity elements affecting the quality of lithium carbonate products. Calcium ions have similar chemical properties to lithium ions and readily co-precipitate with lithium carbonate or form inclusions during lithium precipitation, leading to a decrease in product purity. Residual magnesium ions reduce the crystal regularity of lithium carbonate and affect the processing performance of subsequent battery materials. Therefore, deep decalcification and magnesium removal of the brine before lithium precipitation can significantly improve the purity and consistency of lithium carbonate, ensuring that the product meets battery-grade standards.

[0003] In the process of preparing battery-grade lithium carbonate using the spodumene sulfuric acid method, during alkalization and impurity removal, caustic soda flakes need to be added to the high-lithium brine to adjust the pH to alkalinity, causing magnesium, iron, and manganese to precipitate as hydroxides. Existing alkalization and impurity removal reactors generally use either a one-time pouring method or continuous feeding via a screw conveyor when adding caustic soda flakes. This is not conducive to intermittent, quantitative, and batch feeding of caustic soda flakes. A large amount of caustic soda added at once causes it to accumulate at the bottom of the reactor, resulting in a concentrated release of heat of dissolution and causing localized overheating. This can not only lead to the co-precipitation loss of lithium but also cause magnesium, iron, and manganese hydroxides to form colloidal particles that are difficult to filter due to localized over-alkaliness. Furthermore, during non-feeding periods, the feeding channel should be isolated from the moisture inside the reactor. High-temperature, high-humidity steam inside the reactor can easily backflow into the hopper, causing the caustic soda flakes to absorb moisture and carbonate on the surface.

[0004] Therefore, it is necessary to provide an alkali removal reactor to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention provides an alkalization and impurity removal reactor, which solves the problem that existing alkalization and impurity removal reactors generally use a one-time pouring or continuous feeding method via screw conveyor when adding caustic soda flakes, which is not convenient for achieving intermittent, quantitative, and batch feeding of caustic soda flakes.

[0006] To solve the above-mentioned technical problems, the alkalization and impurity removal reactor provided by the present invention includes an impurity removal reactor, a mounting base, a stirring mechanism, a driving mechanism, and a caustic soda flake dispensing mechanism;

[0007] The stirring mechanism is located inside the impurity removal vessel and is used to mix high-lithium brine and sodium hydroxide solid, including a stirring shaft that is vertically rotatably connected inside the mounting base;

[0008] The driving mechanism includes a slider slidably connected inside the mounting base. A return spring is fixed inside the mounting base and located in front of the slider. A driving tooth plate is fixed on the top of the slider. A rotating seat is fixed on the back of the driving tooth plate. A rotating wheel is rotatably connected to the inner side of the rotating seat. A first cam is connected to the peripheral side of the stirring shaft via a keyway. The peripheral side of the rotating wheel is in contact with the surface of the first cam.

[0009] The caustic soda flake dispensing mechanism includes two sealing plates slidably connected inside the mounting base. Guide rods are slidably connected inside each of the two sealing plates. The ends of the two guide rods that are separated from each other are fixedly connected to the interior of the mounting base. Compression springs are sleeved on the peripheral sides of the two guide rods and on the separated sides of the two sealing plates. A feeding gear is rotatably connected to the top of the mounting base and at the top of the two sealing plates. The feeding gear meshes with a drive gear plate. Guide posts are fixedly provided on the top of each of the two sealing plates and are located inside the feeding gear.

[0010] Preferably, the feeding gear has an arc-shaped groove inside that cooperates with the two guide posts, and a through hole inside the feeding gear. A feeding tube is installed in the through hole of the feeding gear, and the bottom of the feeding tube contacts the top of the two sealing plates.

[0011] Preferably, the mounting base has a groove inside that cooperates with the slider to allow the slider to slide back and forth. The mounting base also has a groove inside that cooperates with the two sealing plates. When the feeding gear rotates clockwise, the two sealing plates will slide to opposite sides with the cooperation of the guide post and the arc groove.

[0012] Preferably, a hopper striking mechanism is fixedly provided on the top of the drive toothed plate. The hopper striking mechanism includes a drive plate fixedly provided on the top of the drive toothed plate. Connecting rods are rotatably connected to both sides of the drive plate. A rotating bracket is rotatably connected to the front side of the connecting rod. A reciprocating rod is fixedly provided on the top of the rotating bracket. A fixed plate is fixedly provided on the top of the impurity removal vessel. The circumferential side of the reciprocating rod is slidably connected to the inside of the fixed plate. An energy storage spring is sleeved on the circumferential side of the reciprocating rod and located at the bottom of the fixed plate. A striking block is fixedly provided on the top of the reciprocating rod.

[0013] Preferably, the top of the mounting base is rotatably connected to a swing anti-drift mechanism, which includes a driven gear rotatably connected to the top of the mounting base via a rotating shaft. The driven gear meshes with a feeding gear. A swing rod is vertically rotatably connected to the inside of the left side of the mounting base. Synchronous pulleys are fixedly provided at the top of the swing rod and the top of the driven gear. Synchronous belts are sleeved on the peripheral sides of the two synchronous pulleys. A swing plate is fixedly provided at the bottom of the swing rod.

[0014] Preferably, a nitrogen protection mechanism is fixedly provided on the right side of the top of the mounting base. The nitrogen protection mechanism includes two fixed brackets fixedly provided on the right side of the top of the mounting base. An air cylinder is fixedly provided on the top of the two fixed brackets. A reciprocating piston bracket is slidably connected inside the air cylinder. A tension spring is sleeved on the circumferential side of the reciprocating piston bracket and located on the left side of the air cylinder. A transmission wheel is rotatably connected inside the left side of the reciprocating piston bracket. A second cam is connected to the circumferential side of the stirring shaft and located on the top of the first cam via a keyway. The left side of the transmission wheel is in contact with the circumferential side of the second cam.

[0015] Preferably, the stirring mechanism further includes multiple sets of stirring blades fixed to the side of the stirring shaft, a stirring motor for driving the stirring shaft to rotate is provided on the top of the fixed plate, the stirring shaft is rotatably connected to the inside of the fixed plate, a crossbeam is fixedly provided at the bottom of the fixed plate, and the crossbeam is fixedly connected to the inner wall of the impurity removal vessel.

[0016] Preferably, movable plates are rotatably connected to both sides of the fixed plate, multiple mounting brackets are arranged in a ring array on the periphery of the impurity removal vessel, an inlet pipe is connected to the left side of the impurity removal vessel, a discharge pipe is connected to the bottom of the impurity removal vessel, a hopper is provided on the top of the fixed plate, and the hopper is connected to the feeding pipe.

[0017] The process for preparing lithium carbonate by secondary pulping of spodumene to remove calcium and magnesium includes the following steps:

[0018] Step S1, Secondary pulping: Mix calcium carbonate, spodumene leaching brine and acidified clinker to form a pulp, stir and react, then filter to obtain high-lithium brine;

[0019] Step S2, Alkaliization and Impurity Removal: Heat the high-lithium brine, add solid sodium hydroxide to adjust the pH to alkaline, stir the reaction to precipitate magnesium, iron, manganese and other ions;

[0020] Step S3, Deep Calcium Removal (Choose one):

[0021] Method 1, High-Temperature Seed Sodium Carbonate Method: Filter the liquid from step S2, heat the filtrate, and then add calcium carbonate seeds and sodium carbonate solution to react;

[0022] Method 2, Medium-temperature sodium oxalate method: In step S2, the liquid is not filtered, but directly heated and then sodium oxalate solid is added to react.

[0023] Step S4, Filtration: Filter the liquid after the reaction in step S3 to separate the solid and liquid and obtain the pre-lithiation liquid;

[0024] Step S5, Lithium precipitation: Heat the liquid before lithium precipitation, and slowly add sodium carbonate solution to react and form lithium carbonate precipitate;

[0025] Step S6, Separation and Drying: Crude lithium carbonate is obtained by filtration, washed with hot water until qualified, and dried to obtain battery-grade lithium carbonate.

[0026] Compared with related technologies, the alkali removal reactor provided by the present invention has the following beneficial effects:

[0027] The rotation of the stirring shaft drives the first cam to drive the drive tooth plate to reciprocate, which in turn drives the feeding gear to rotate forward and backward, causing the sealing plate to open and close intermittently, realizing the quantitative and batch feeding of caustic soda flakes. The feeding frequency adapts to the stirring speed, effectively avoiding local overheating, sedimentation and agglomeration, and lithium co-precipitation loss caused by a large amount of caustic soda feeding at one time. At the same time, it reduces the floating and splashing of caustic soda flakes, ensuring that the caustic soda is quickly dispersed in the brine, so that magnesium, iron and manganese form large-particle hydroxide precipitates that are easy to filter, significantly improving the impurity removal efficiency and lithium recovery rate.

[0028] During non-feeding periods when the sealing plate is closed, the feeding channel is reliably isolated from the moisture in the impurity removal kettle, preventing the caustic soda flakes from absorbing moisture and carbonating, avoiding a decrease in alkali purity and the formation of fine-particle calcium carbonate, thereby reducing alkali consumption and alleviating the burden of subsequent calcium removal. Attached Figure Description

[0029] 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.

[0030] Figure 1 The optimal structural schematic diagram provided for this invention;

[0031] Figure 2 This is a schematic diagram of the cross-sectional view of the impurity removal vessel provided by the present invention;

[0032] Figure 3 for Figure 2 The diagram shows the structure of the mounting base;

[0033] Figure 4 Schematic diagram of the drive mechanism and caustic soda dispensing mechanism provided by the present invention;

[0034] Figure 5 A schematic diagram showing the state in which the stirring shaft of the present invention drives the first cam to rotate clockwise, and drives the drive gear plate to move forward through the rotating wheel;

[0035] Figure 6 This is a schematic diagram of the hopper striking mechanism provided by the present invention;

[0036] Figure 7A schematic diagram showing the state in which the drive toothed plate drives the convex plate to move forward, causing the drive wheel to drive the rotating bracket and the reciprocating rod to move upward, as provided by the present invention.

[0037] Figure 8 This is a schematic diagram of the swing anti-drift mechanism provided by the present invention;

[0038] Figure 9 A schematic diagram showing the state in which the swing rod drives the swing plate to rotate counterclockwise, as provided by the present invention.

[0039] Figure 10 This is a schematic diagram of the nitrogen protection mechanism provided by the present invention;

[0040] Figure 11 This is a schematic diagram of the stirring mechanism provided by the present invention;

[0041] Figure 12 This is a schematic diagram of the process flow provided by the present invention.

[0042] Explanation of icon numbers:

[0043] 1. Impurity removal kettle; 2. Mounting base;

[0044] 3. Stirring mechanism; 31. Stirring shaft; 32. Stirring paddle; 33. Stirring motor;

[0045] 4. Drive mechanism; 41. Slider; 42. Return spring; 43. Drive gear plate; 44. Rotating seat; 45. Rotary wheel; 46. First cam;

[0046] 5. Caustic soda flake feeding mechanism; 51. Sealing plate; 52. Guide rod; 53. Compression spring; 54. Feeding gear; 55. Guide column;

[0047] 6. Feeding pipe;

[0048] 7. Hopper striking mechanism; 71. Drive plate; 72. Connecting rod; 73. Rotating bracket; 74. Reciprocating rod; 75. Energy storage spring; 76. Striking block;

[0049] 8. Swing anti-drift mechanism; 81. Passive gear; 82. Swing rod; 83. Synchronous pulley; 84. Synchronous belt; 85. Swing plate;

[0050] 9. Nitrogen protection mechanism; 91. Fixed bracket; 92. Air cylinder; 93. Reciprocating piston bracket; 94. Tension spring; 95. Drive wheel; 96. Second cam;

[0051] 10. Fixed plate; 11. Horizontal frame; 12. Movable plate; 13. Mounting bracket; 14. Liquid inlet pipe; 15. Discharge pipe; 16. Hopper. Detailed Implementation

[0052] 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.

[0053] This invention provides an alkali removal reaction vessel.

[0054] First embodiment:

[0055] Please see Figures 1 to 5 An alkalization and impurity removal reactor includes an impurity removal reactor 1, a mounting base 2, a stirring mechanism 3, a driving mechanism 4, and a caustic soda flake dispensing mechanism 5;

[0056] The stirring mechanism 3 is located inside the impurity removal vessel 1 and is used to mix high-lithium brine and sodium hydroxide solid, including a stirring shaft 31 that is vertically rotatably connected inside the mounting base 2;

[0057] The drive mechanism 4 includes a slider 41 slidably connected inside the mounting base 2. A return spring 42 is fixed inside the mounting base 2 and located in front of the slider 41. A drive tooth plate 43 is fixed on the top of the slider 41. A rotating seat 44 is fixed on the back of the drive tooth plate 43. A rotating wheel 45 is rotatably connected to the inner side of the rotating seat 44. A first cam 46 is connected to the peripheral side of the stirring shaft 31 via a keyway. The peripheral side of the rotating wheel 45 is in contact with the surface of the first cam 46.

[0058] The caustic soda dispensing mechanism 5 includes two sealing plates 51 slidably connected inside the mounting base 2. Guide rods 52 are slidably connected inside each of the two sealing plates 51. The ends of the two guide rods 52 that are separated from each other are fixedly connected to the interior of the mounting base 2. Compression springs 53 are sleeved on the peripheral side of each of the two guide rods 52 and on the side of the two sealing plates 51 that are separated from each other. A feeding gear 54 is rotatably connected to the top of the mounting base 2 and on the top of the two sealing plates 51. The feeding gear 54 meshes with a drive gear plate 43. Guide posts 55 are fixedly provided on the top of each of the two sealing plates 51 and are located inside the feeding gear 54.

[0059] The feeding gear 54 has an arc-shaped groove inside that works with the two guide posts 55. The feeding gear 54 also has a through hole inside. A feeding tube 6 is installed inside the through hole of the feeding gear 54. The bottom of the feeding tube 6 is in contact with the top of the two sealing plates 51.

[0060] The mounting base 2 has a sliding groove inside that works with the slider 41 to allow the slider 41 to slide back and forth. The mounting base 2 also has a sliding groove inside that works with the two sealing plates 51. When the feeding gear 54 rotates clockwise, the two sealing plates 51 will slide to the opposite side under the cooperation of the guide post 55 and the arc groove.

[0061] Preferably, a PTFE sealing gasket is installed between the top surface of the sealing plate 51 and the bottom surface of the feeding gear 54, and a dust scraping groove is provided on the sliding surface of the sealing plate 51 to prevent alkali powder from entering the guide rod 52 and the compression spring 53 area.

[0062] Please combine Figure 4 and Figure 5 When the stirring shaft 31 rotates, it will drive the first cam 46 connected by the keyway on the surface to rotate. When the protruding part of the first cam 46 gradually contacts the rotating wheel 45, it will push the rotating wheel 45 to move forward. The rotating wheel 45 moves forward and then drives the drive tooth plate 43 to move forward through the rotating seat 44, so that the slider 41 slides forward inside the mounting seat 2, and the return spring 42 contracts.

[0063] Furthermore, when the drive tooth plate 43 moves forward, it will drive the feeding gear 54 to rotate clockwise. The clockwise rotation of the feeding gear 54, in cooperation with the arc groove and the guide post 55, will drive the two sealing plates 51 to move to the opposite side, thereby opening the through hole in the feeding gear 54, and allowing the caustic soda flakes in the feeding tube 6 to fall into the high lithium brine.

[0064] Furthermore, as the stirring shaft 31 continues to rotate, when the protruding part of the first cam 46 disengages from the rotating wheel 45, under the elastic force of the return spring 42, the slider 41 will drive the drive tooth plate 43 to move backward, so that the rotating wheel 45 always keeps in close contact with the surface of the first cam 46. When the drive tooth plate 43 moves backward, it will drive the feeding gear 54 to rotate counterclockwise. With the cooperation of the arc groove and the guide post 55, the two sealing plates 51 will move to the opposite side, resealing the through hole in the feeding gear 54. As the stirring shaft 31 continues to rotate, the caustic soda flakes will be fed intermittently.

[0065] In this embodiment, the rotation of the stirring shaft 31 drives the first cam 46 to push the drive tooth plate 43 to reciprocate, thereby driving the feeding gear 54 to rotate forward and backward, causing the sealing plate 51 to open and close intermittently, realizing the quantitative and batch feeding of caustic soda flakes. The feeding frequency adapts to the stirring speed, effectively avoiding local overheating, sedimentation and agglomeration, and lithium co-precipitation loss caused by a large amount of caustic soda feeding at one time. At the same time, it reduces the floating and splashing of caustic soda flakes, ensuring that the caustic soda is quickly dispersed in the brine, so that magnesium, iron and manganese form large-particle hydroxide precipitates that are easy to filter, significantly improving the impurity removal efficiency and lithium recovery rate.

[0066] During the non-feeding period when the sealing plate 51 is closed, the feeding channel is reliably isolated from the moisture in the impurity removal kettle 1, preventing the caustic soda flakes from absorbing moisture and carbonating, avoiding a decrease in alkali purity and the formation of fine calcium carbonate particles, thereby reducing alkali consumption and alleviating the subsequent calcium removal burden.

[0067] Second embodiment:

[0068] Please see Figures 6 to 9 The top of the drive toothed plate 43 is fixedly provided with a hopper striking mechanism 7. The hopper striking mechanism 7 includes a drive plate 71 fixedly provided on the top of the drive toothed plate 43. Both sides of the drive plate 71 are rotatably connected with connecting rods 72. The front side of the connecting rods 72 is rotatably connected with a rotating bracket 73. The top of the rotating bracket 73 is fixedly provided with a reciprocating rod 74. The top of the impurity removal vessel 1 is fixedly provided with a fixed plate 10. The circumferential side of the reciprocating rod 74 is slidably connected to the inside of the fixed plate 10. The circumferential side of the reciprocating rod 74 and the bottom of the fixed plate 10 are fitted with an energy storage spring 75. The top of the reciprocating rod 74 is fixedly provided with a striking block 76.

[0069] The top of the mounting base 2 is rotatably connected to a swing anti-drift mechanism 8. The swing anti-drift mechanism 8 includes a driven gear 81 rotatably connected to the top of the mounting base 2 via a rotating shaft. The driven gear 81 meshes with the feeding gear 54. The left side of the mounting base 2 is vertically rotatably connected to a swing rod 82. The top of the swing rod 82 and the top of the driven gear 81 are both fixed with synchronous pulleys 83. The peripheral sides of the two synchronous pulleys 83 are fitted with synchronous belts 84. The bottom end of the swing rod 82 is fixed with a swing plate 85.

[0070] Preferably, the swing plate 85 is located underwater when it is in operation;

[0071] Please combine Figure 6 and Figure 7 When the drive tooth plate 43 moves forward, it will simultaneously drive the top drive plate 71 to move forward. The forward movement of the drive plate 71 will drive the rear side of the connecting rod 72 to move forward, thereby lifting the rotating bracket 73 upward. The upward movement of the rotating bracket 73 will drive the reciprocating rod 74 to move upward, causing the energy storage spring 75 to contract. The upward movement of the reciprocating rod 74 will then drive the striking block 76 to strike the bottom of the hopper 16.

[0072] Furthermore, when the drive tooth plate 43 is reset to the rear, it will simultaneously drive the top drive plate 71 to move backward. Under the elastic force of the energy storage spring 75, the reciprocating rod 74 will drive the striking block 76 to move downward, resetting the position of the striking block 76.

[0073] Please combine Figure 8 and Figure 9When the feeding gear 54 rotates clockwise to add caustic soda flakes into the impurity removal kettle 1, it will simultaneously drive the driven gear 81 to rotate counterclockwise. The counterclockwise rotation of the driven gear 81 will drive the swing rod 82 and the swing plate 85 to rotate counterclockwise through the synchronous pulley 83 and the synchronous belt 84.

[0074] Furthermore, when the feeding gear 54 rotates counterclockwise, it will drive the driven gear 81 to rotate clockwise. With the cooperation of the synchronous belt 84 and the synchronous pulley 83, the clockwise rotation of the driven gear 81 will drive the swing rod 82 and the swing plate 85 to rotate clockwise, thereby resetting the swing plate 85.

[0075] In this embodiment, the reciprocating motion of the drive tooth plate 43 drives the drive plate 71 to periodically lift and rotate the bracket 73. After the reciprocating rod 74 compresses the energy storage spring 75, the striking block 76 intermittently strikes the bottom of the hopper 16, thereby effectively breaking the bridging and rat hole phenomenon of caustic soda flakes, ensuring that caustic soda flakes fall into the feeding pipe 6 continuously and stably, avoiding interruption of feeding or fluctuation of feeding amount due to blockage, thereby improving feeding reliability and reducing manual intervention.

[0076] By rotating the feeding gear 54 in both directions, and with the cooperation of the synchronous pulley 83, synchronous belt 84, and swing rod 82, the submerged swing plate 85 is driven to swing back and forth. At the moment when the caustic soda flakes fall into the liquid surface, a turbulent water flow is generated, which destroys the lifting effect of the brine surface tension on the flat caustic soda flakes, forcing the caustic soda flakes to sink quickly and disperse into the stirring vortex zone. This fundamentally solves the problems of caustic soda flakes floating on the liquid surface, splashing with the liquid flow, and absorbing moisture and carbonation due to long-term suspension. Through the synergistic effect of the two, the caustic soda flakes can be fed into the impurity removal kettle 1 in a stable flow rate and uniform dispersion, avoiding local accumulation and excessively high instantaneous concentration, and ultimately improving the purity and batch stability of battery-grade lithium carbonate.

[0077] Third embodiment:

[0078] Please see Figure 1 , Figure 2 , Figure 10 and Figure 11 A nitrogen protection mechanism 9 is fixedly provided on the right side of the top of the mounting base 2. The nitrogen protection mechanism 9 includes two fixed brackets 91 fixedly provided on the right side of the top of the mounting base 2. An air cylinder 92 is fixedly provided on the top of the two fixed brackets 91. A reciprocating piston bracket 93 is slidably connected inside the air cylinder 92. A tension spring 94 is sleeved on the circumferential side of the reciprocating piston bracket 93 and located on the left side of the air cylinder 92. A transmission wheel 95 is rotatably connected inside the left side of the reciprocating piston bracket 93. A second cam 96 is connected to the circumferential side of the stirring shaft 31 and located on the top of the first cam 46 via a keyway. The left side of the transmission wheel 95 is in contact with the circumferential side of the second cam 96.

[0079] The stirring mechanism 3 also includes multiple sets of stirring paddles 32 fixed to the periphery of the stirring shaft 31. The top of the fixed plate 10 is provided with a stirring motor 33 for driving the stirring shaft 31 to rotate. The stirring shaft 31 is rotatably connected to the inside of the fixed plate 10. The bottom of the fixed plate 10 is fixed with a crossbeam 11, which is fixedly connected to the inner wall of the impurity removal vessel 1.

[0080] Movable plates 12 are rotatably connected to both sides of the fixed plate 10. Multiple mounting brackets 13 are arranged in a ring array on the periphery of the impurity removal vessel 1. The left side of the impurity removal vessel 1 is connected to the liquid inlet pipe 14. The bottom of the impurity removal vessel 1 is connected to the discharge pipe 15. The top of the fixed plate 10 is provided with a hopper 16, which is connected to the feeding pipe 6.

[0081] Preferably, the installation positions of the first cam 46 and the second cam 96 are staggered, and nitrogen gas will start to be injected momentarily before the sealing plate 51 is opened and stop after the sealing plate 51 is closed;

[0082] Preferably, the first cam 46 and the second cam 96 are keyway connected to the stirring shaft 31. When the heat preservation stage is reached, the keyway connection between the first cam 46 and the second cam 96 and the stirring shaft 31 is canceled by opening the movable plate 12, so that the stirring shaft 31 can work independently to stir and preserve the material.

[0083] Preferably, the cylinder 92 is used to store nitrogen. The right side of the cylinder 92 is connected to an outlet pipe, and the top of the cylinder 92 is connected to an inlet pipe. Both the outlet pipe and the inlet pipe are equipped with one-way valves. The outlet position of the outlet pipe is located at the feeding position of the feeding pipe 6. The inlet end of the inlet pipe is equipped with a pressure reducing valve and a filter, and is connected to an external low-pressure nitrogen source.

[0084] Preferably, the vent pipe can be connected to the hopper 16, so that the caustic soda flakes fall loosely at the moment of impact by the striking block 76, and nitrogen is injected simultaneously to form a pneumatic conveying effect to assist in feeding.

[0085] Please combine Figure 10 When the stirring shaft 31 rotates, it will simultaneously drive the second cam 96 to rotate. When the protruding position of the second cam 96 gradually contacts the transmission wheel 95, it will push the reciprocating piston bracket 93 to move to the right through the transmission wheel 95, causing the tension spring 94 to contract. By moving the reciprocating piston bracket 93 to the right, nitrogen gas is transported from the gas cylinder 92 to the feeding position.

[0086] Furthermore, as the stirring shaft 31 continues to rotate, when the protruding position of the second cam 96 gradually disengages from the transmission wheel 95, under the expansion force of the tension spring 94, the reciprocating piston bracket 93 will reset to the left and re-extract nitrogen.

[0087] Please combine Figure 11Start the stirring motor 33. The stirring motor 33 rotates, which drives the stirring shaft 31 to rotate. The rotation of the stirring shaft 31 drives multiple stirring paddles 32 to rotate, thereby mixing the caustic soda flakes and the high-lithium brine.

[0088] In this embodiment, the stirring shaft 31 drives the second cam 96 to push the reciprocating piston bracket 93, causing the gas cylinder 92 to intermittently spray nitrogen. The nitrogen spraying is precisely synchronized with the opening and closing action of the sealing plate 51, forming a local inert gas curtain in the feeding pipe 6 and the material dropping area. This effectively isolates the moisture and carbon dioxide in the reactor, prevents the caustic soda flakes from absorbing moisture and carbonation, maintains the purity of the alkali, and avoids the formation of fine calcium carbonate particles. Nitrogen can also be introduced into the hopper 16 to form a pneumatic conveying during the tapping action, assisting the caustic soda flakes to fall smoothly and preventing blockage. This provides a reliable guarantee for the stable production of high-purity battery-grade lithium carbonate.

[0089] In another application, the alkalization and impurity removal reactor can also be used in the production of powder coatings and plastic masterbatches. It is used for the mixing process before powder coating extrusion and for the addition of additives in the production of plastic masterbatches. Powder or flake additives are prone to bridging in the hopper 16 and floating and flying in the mixer, resulting in uneven dispersion. By knocking to break the bridging, the powder can be made to flow continuously. By adjusting the swing plate 85, the additives can be dispersed into the base material to reduce dust.

[0090] This invention also provides a process for preparing lithium carbonate by secondary pulping of spodumene to remove calcium and magnesium.

[0091] Please see Figure 12 The process for preparing lithium carbonate by secondary pulping of spodumene to remove calcium and magnesium includes the following steps:

[0092] Step S1, Secondary pulping: Mix calcium carbonate, spodumene leaching brine and acidified clinker to form a pulp, stir and react, then filter to obtain high-lithium brine;

[0093] Step S2, Alkaliization and Impurity Removal: Heat the high-lithium brine, add solid sodium hydroxide to adjust the pH to alkaline, stir the reaction to precipitate magnesium, iron, manganese and other ions;

[0094] Step S3, Deep Calcium Removal (Choose one):

[0095] Method 1, High-Temperature Seed Sodium Carbonate Method: Filter the liquid from step S2, heat the filtrate, and then add calcium carbonate seeds and sodium carbonate solution to react;

[0096] Method 2, Medium-temperature sodium oxalate method: In step S2, the liquid is not filtered, but directly heated and then sodium oxalate solid is added to react.

[0097] Step S4, Filtration: Filter the liquid after the reaction in step S3 to separate the solid and liquid and obtain the pre-lithiation liquid;

[0098] Step S5, Lithium precipitation: Heat the liquid before lithium precipitation, and slowly add sodium carbonate solution to react and form lithium carbonate precipitate;

[0099] Step S6, Separation and Drying: Filter to obtain crude lithium carbonate, wash with hot water until qualified, and dry to obtain battery-grade lithium carbonate;

[0100] Preferably, the raw materials required in the steps are: spodumene leaching brine: Li: 10-20 g / L, containing impurity ions such as calcium, magnesium, iron, and manganese; acidified clinker: obtained by mixing spodumene conversion material with concentrated sulfuric acid at a mass ratio of 3-3.3:1 and calcining at 260°C for 30-60 min; sodium hydroxide, sodium carbonate, and sodium oxalate: industrial grade.

[0101] Preferably, in step S1, calcium carbonate, spodumene leaching brine, and acidified clinker are mixed in a mass ratio of 1:6:4-6 to form a slurry. The stirring speed is 250-350 r / min, and the reaction is carried out at room temperature for 30-60 min. The pH of the slurry is controlled at 5.5-7.5. After the reaction is completed, the mixture is filtered to obtain a high-lithium brine with a lithium ion concentration of 25-40 g / L.

[0102] Preferably, in step S1, lithium-containing primary leaching brine is used as the leaching medium, and secondary pulping is carried out with calcium carbonate and acidified clinker. The lithium concentration can be significantly increased under normal temperature and pressure without the need for evaporation concentration or pressure cooking reaction.

[0103] Preferably, in step S2, the high-lithium brine is heated to 65-75°C in a water bath, sodium hydroxide solid is added to adjust the pH to 11.5-12.5, the stirring speed is 250-350 r / min, and the reaction is carried out for 30-60 min to completely precipitate magnesium, iron, manganese and other ions.

[0104] Preferably, in step S3, in method one, the filtrate is heated in a water bath to 90-100°C, the stirring speed is 250-350 r / min, calcium carbonate seed crystals are added, the amount added is 1-5 times the mass of calcium in the brine (can be recycled), a sodium carbonate solution with a concentration of 300-340 g / L is added, the amount is 1.2-3 times the theoretical molar amount required for calcium precipitation, and the reaction is carried out for 30-60 min;

[0105] Preferably, in step S3, method two, the liquid is not filtered, and is directly kept in a water bath at 65-75°C. Sodium oxalate solid is added, and the amount is 1.2-2 times the theoretical molar amount required for calcium precipitation. The reaction time is 30-60 minutes.

[0106] Preferably, step S3, method two, is suitable for situations where the calcium content is low and the filtration performance is good. If necessary, magnesium can be removed by filtration before calcium precipitation.

[0107] Preferably, in step S4, the calcium ion concentration of the solid-liquid separation solution before lithium precipitation is ≤40mg / L and the magnesium ion concentration is ≤10mg / L.

[0108] Preferably, in step S5, the lithium precipitation solution is heated to 90-95°C, and sodium carbonate solution (concentration 300g / L) is slowly added. The reaction is carried out for 1-2 hours to generate Li2CO3 precipitate.

[0109] Preferably, in step S6, the crude lithium carbonate obtained by filtration is washed with hot water until Cl. - SO4 2- The sample passed the test and was dried to obtain battery-grade lithium carbonate (purity ≥ 99.5%).

[0110] In this embodiment, high-lithium brine is obtained by direct concentration through secondary pulping without the need for evaporation and concentration, significantly reducing energy consumption and investment costs. At the same time, it avoids the enrichment of impurity ions during the concentration process, reducing the burden of subsequent purification from the source. To address the problem of poor calcium removal effect and large lithium loss of conventional sodium carbonate at high lithium concentrations, two deep calcium removal routes are provided: high-temperature seeded sodium carbonate method and medium-temperature sodium oxalate method. These methods can effectively eliminate the interference of lithium ions on calcium precipitation, obtain high-purity calcium slag that is easy to filter, ensure that the content of impurities such as calcium and magnesium in the purified liquid strictly meets the raw material requirements of battery-grade lithium carbonate, significantly reduce lithium co-precipitation loss, improve the overall lithium yield, and ultimately stably produce high-purity battery-grade lithium carbonate products that meet the standards.

[0111] Please refer to the reference again. Figures 1 to 11 The working principle of the alkali removal reactor provided by this invention is as follows:

[0112] Step S1: After the stirring motor 33 starts, it drives the stirring shaft 31 and the first cam 46 fixed thereon to rotate. When the protruding part of the first cam 46 gradually contacts the rotating wheel 45, it pushes the rotating wheel 45, the rotating seat 44 and the drive tooth plate 43 to move forward against the return spring 42. After the protruding part of the first cam 46 disengages, the return spring 42 pushes the slider 41 and the drive tooth plate 43 to return to their original position.

[0113] Each time the drive tooth plate 43 completes one back-and-forth reciprocating motion, it drives the feeding gear 54 that meshes with it to complete one clockwise rotation and one counterclockwise rotation. The feeding gear 54 has an arc-shaped groove inside, and the guide post 55 at the top of the two sealing plates 51 is located in the arc-shaped groove. When the feeding gear 54 rotates clockwise, the arc-shaped groove pushes the guide post 55 to make the two sealing plates 51 slide in the direction of separation. The through hole of the feeding gear 54 opens, and the caustic soda flakes pre-stored in the feeding pipe 6 fall into the high-lithium brine of the impurity removal kettle 1 by gravity.

[0114] When the feeding gear 54 rotates counterclockwise, the sealing plate 51 slides in the opposite direction, and the through hole is resealed. As the stirring shaft 31 continues to rotate, the above process is repeated, realizing the intermittent, batch, and quantitative feeding of caustic soda flakes, and the feeding frequency adapts to the stirring speed.

[0115] In step S2, when the drive tooth plate 43 moves forward, it simultaneously drives the top drive plate 71 to move forward. The forward movement of the drive plate 71 drives the rear side of the connecting rod 72 to move forward, thereby lifting the rotating bracket 73 upward. The upward movement of the rotating bracket 73 drives the reciprocating rod 74 to move upward, causing the energy storage spring 75 to contract. The upward movement of the reciprocating rod 74 drives the striking block 76 to strike the bottom of the hopper 16, generating vibration, thereby breaking the bridging or rat hole phenomenon of caustic soda flakes in the hopper 16. When the drive tooth plate 43 returns to its original position, the drive plate 71 drives the rear side of the connecting rod 72 to move backward. Under the elastic force of the energy storage spring 75 and the force of gravity, the reciprocating rod 74 drives the striking block 76 to move downward, completing the reset.

[0116] In step S3, when the feeding gear 54 rotates clockwise to add caustic soda flakes into the impurity removal kettle 1, it will simultaneously drive the driven gear 81 to rotate counterclockwise. The counterclockwise rotation of the driven gear 81 will drive the swing rod 82 and the swing plate 85 to rotate counterclockwise through the synchronous pulley 83 and the synchronous belt 84.

[0117] When the feeding gear 54 rotates counterclockwise, it will drive the driven gear 81 to rotate clockwise. With the cooperation of the synchronous belt 84 and the synchronous pulley 83, the clockwise rotation of the driven gear 81 will drive the swing rod 82 and the swing plate 85 to rotate clockwise, thereby resetting the swing plate 85.

[0118] In step S4, the stirring shaft 31 is equipped with a second cam 96. The second cam 96 rotates with the stirring shaft 31. When the protruding part gradually contacts the transmission wheel 95, it pushes the transmission wheel 95 and the reciprocating piston bracket 93 to move to the right. The nitrogen in the compressed air cylinder 92 is compressed and the tension spring 94 is contracted. At this time, the one-way valve on the air outlet pipe is opened, and the nitrogen is sprayed through the air outlet pipe to the feeding position of the feeding pipe 6 or into the hopper 16.

[0119] When the protruding part of the second cam 96 disengages from the transmission wheel 95, the tension spring 94 pushes the reciprocating piston bracket 93 to reset to the left. At this time, the one-way valve on the air inlet pipe opens, and the air cylinder 92 re-intakes nitrogen. Since the phases of the first cam 46 and the second cam 96 are misaligned, the nitrogen injection starts instantaneously before the sealing plate 51 opens and stops after the sealing plate 51 closes, precisely covering the feeding period. The injected nitrogen forms a local inert gas curtain in the feeding pipe 6 and the material drop area, isolating moisture and carbon dioxide in the reactor and preventing caustic soda flakes from absorbing moisture and carbonizing.

[0120] 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. An alkalization and impurity removal reactor, characterized in that, It includes a purification kettle, mounting base, stirring mechanism, drive mechanism, and caustic soda flake dispensing mechanism; The stirring mechanism is located inside the impurity removal vessel and is used to mix high-lithium brine and sodium hydroxide solid, including a stirring shaft that is vertically rotatably connected inside the mounting base; The driving mechanism includes a slider slidably connected inside the mounting base. A return spring is fixed inside the mounting base and located in front of the slider. A driving tooth plate is fixed on the top of the slider. A rotating seat is fixed on the back of the driving tooth plate. A rotating wheel is rotatably connected to the inner side of the rotating seat. A first cam is connected to the peripheral side of the stirring shaft via a keyway. The peripheral side of the rotating wheel is in contact with the surface of the first cam. The caustic soda flake dispensing mechanism includes two sealing plates slidably connected inside the mounting base. Guide rods are slidably connected inside each of the two sealing plates. The ends of the two guide rods that are separated from each other are fixedly connected to the interior of the mounting base. Compression springs are sleeved on the peripheral sides of the two guide rods and on the separated sides of the two sealing plates. A feeding gear is rotatably connected to the top of the mounting base and at the top of the two sealing plates. The feeding gear meshes with a drive gear plate. Guide posts are fixedly provided on the top of each of the two sealing plates and are located inside the feeding gear.

2. The alkalization and impurity removal reactor according to claim 1, characterized in that, The feeding gear has an arc-shaped groove inside that works with two guide posts. The feeding gear also has a through hole inside, and a feeding tube is installed inside the through hole. The bottom of the feeding tube contacts the top of the two sealing plates.

3. The alkalization and impurity removal reactor according to claim 2, characterized in that, The mounting base has a groove inside that works with the slider to allow the slider to slide back and forth. The mounting base also has a groove inside that works with the two sealing plates. When the feeding gear rotates clockwise, the two sealing plates will slide to opposite sides with the help of the guide post and the arc groove.

4. The alkalization and impurity removal reactor according to claim 2, characterized in that, The top of the drive toothed plate is fixedly provided with a hopper striking mechanism. The hopper striking mechanism includes a drive plate fixedly provided on the top of the drive toothed plate. Both sides of the drive plate are rotatably connected to connecting rods. The front side of the connecting rods is rotatably connected to a rotating bracket. The top of the rotating bracket is fixedly provided with a reciprocating rod. The top of the impurity removal vessel is fixedly provided with a fixed plate. The circumferential side of the reciprocating rod is slidably connected to the inside of the fixed plate. An energy storage spring is sleeved on the circumferential side of the reciprocating rod and located at the bottom of the fixed plate. The top of the reciprocating rod is fixedly provided with a striking block.

5. The alkalization and impurity removal reactor according to claim 1, characterized in that, The top of the mounting base is rotatably connected to a swing anti-drift mechanism. The swing anti-drift mechanism includes a driven gear rotatably connected to the top of the mounting base via a rotating shaft. The driven gear meshes with a feeding gear. A swing rod is vertically rotatably connected to the inside of the left side of the mounting base. Synchronous pulleys are fixedly provided at the top of the swing rod and the top of the driven gear. Synchronous belts are sleeved on the circumferential sides of the two synchronous pulleys. A swing plate is fixedly provided at the bottom end of the swing rod.

6. The alkalization and impurity removal reactor according to claim 1, characterized in that, A nitrogen protection mechanism is fixedly installed on the right side of the top of the mounting base. The nitrogen protection mechanism includes two fixed brackets fixedly installed on the right side of the top of the mounting base. An air cylinder is fixedly installed on the top of the two fixed brackets. A reciprocating piston bracket is slidably connected inside the air cylinder. A tension spring is sleeved on the circumferential side of the reciprocating piston bracket and located on the left side of the air cylinder. A transmission wheel is rotatably connected inside the left side of the reciprocating piston bracket. A second cam is connected to the circumferential side of the stirring shaft and located on the top of the first cam via a keyway. The left side of the transmission wheel is in contact with the circumferential side of the second cam.

7. The alkalization and impurity removal reactor according to claim 4, characterized in that, The stirring mechanism also includes multiple sets of stirring blades fixed to the side of the stirring shaft. The top of the fixed plate is provided with a stirring motor for driving the stirring shaft to rotate. The stirring shaft is rotatably connected to the inside of the fixed plate. The bottom of the fixed plate is fixed with a crossbeam, which is fixedly connected to the inner wall of the impurity removal vessel.

8. The alkalization and impurity removal reactor according to claim 7, characterized in that, Movable plates are rotatably connected to both sides of the fixed plate. Multiple mounting brackets are arranged in a ring array on the periphery of the impurity removal vessel. An inlet pipe is connected to the left side of the impurity removal vessel. A discharge pipe is connected to the bottom of the impurity removal vessel. A hopper is provided on the top of the fixed plate. The hopper is connected to the feeding pipe.

9. A process for preparing lithium carbonate by secondary pulping of spodumene to remove calcium and magnesium, characterized in that, Includes the following steps: Step S1, Secondary pulping: Mix calcium carbonate, spodumene leaching brine and acidified clinker to form a pulp, stir and react, then filter to obtain high-lithium brine; Step S2, Alkaliization and Impurity Removal: Heat the high-lithium brine, add solid sodium hydroxide to adjust the pH to alkaline, stir the reaction to precipitate magnesium, iron, manganese and other ions. The alkaliization and impurity removal should be completed in the alkaliization and impurity removal reactor as described in any one of claims 1-8. Step S3, Deep Calcium Removal (Choose one): Method 1, High-Temperature Seed Sodium Carbonate Method: Filter the liquid from step S2, heat the filtrate, and then add calcium carbonate seeds and sodium carbonate solution to react; Method 2, Medium-temperature sodium oxalate method: In step S2, the liquid is not filtered, but directly heated and then sodium oxalate solid is added to react. Step S4, Filtration: Filter the liquid after the reaction in step S3 to separate the solid and liquid and obtain the pre-lithiation liquid; Step S5, Lithium precipitation: Heat the liquid before lithium precipitation, and slowly add sodium carbonate solution to react and form lithium carbonate precipitate; Step S6, Separation and Drying: Crude lithium carbonate is obtained by filtration, washed with hot water until qualified, and dried to obtain battery-grade lithium carbonate.

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