Flash evaporation device and method for selectively extracting and recovering lithium from ternary positive electrode powder

Abstract

The present application discloses a flash evaporation device and a method for selectively extracting and recovering lithium from ternary positive electrode powder. The flash evaporation device comprises a tank body, a liquid inlet unit and a pressure control unit, wherein a steam line is provided at a top end of the tank body, a liquid discharge outlet is provided at a bottom end of the tank body, one end of the liquid inlet unit extends into the tank body and is provided with a limiting plate, and a side surface of the liquid inlet unit is provided with an air inlet; the pressure control unit is mounted on an outer side of the end of the liquid inlet unit located within the tank body, the pressure control unit comprises a blocking member sleeved over the outside of the liquid inlet unit, a first resilient member is arranged below the blocking member, and a second resilient member is arranged above the blocking member, a bottom end of the blocking member abuts against the first resilient member, and a top end of the blocking member is rotatably connected to the second resilient member. The flash evaporation device and the method for selectively extracting and recovering lithium from ternary positive electrode powder have high flash evaporation efficiency, and can effectively increase the concentration of lithium in leaching solutions.

Description

A flash evaporation treatment device and a selective lithium extraction and recovery method for ternary cathode powder. Technical Field

[0001] This application relates to the field of lithium-ion battery technology, specifically to a flash evaporation treatment device and a method for selective lithium extraction and recovery from ternary cathode powder. Background Technology

[0002] Lithium-ion batteries have excellent properties such as high voltage, high cycle life, high capacity and good thermal stability, and have been widely used. However, after multiple charge-discharge cycles, the active materials of lithium-ion batteries become deactivated and unusable due to structural changes, resulting in a huge number of retired and scrapped lithium-ion batteries.

[0003] Currently, the recycling methods for spent lithium-ion batteries are mainly divided into two types: hydrometallurgical processes and pyrometallurgical processes, with a focus on recovering valuable metal elements. Pyrometallurgical recycling is energy-intensive, polluting, and has poor separation efficiency; hydrometallurgical processes, on the other hand, have advantages such as milder conditions and lower energy consumption. Hydrometallurgical recycling of lithium metal from lithium-ion batteries has been industrialized. The main technical problems encountered in preparing lithium sulfate solution from ternary cathode waste using hydrometallurgical processes are: poor flash evaporation efficiency during the flash evaporation process, inability to prepare high-concentration lithium sulfate solutions, and poor stability. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, one of the purposes of this application is to invent a flash evaporation treatment device with high flash evaporation efficiency.

[0005] The second objective of this application is to invent a method for selective lithium extraction and recovery from ternary cathode powder using the aforementioned flash evaporation treatment equipment.

[0006] One of the objectives of this application is to adopt the following technical solution:

[0007] A flash evaporation treatment device includes a tank, a liquid inlet unit, and a pressure control unit. A steam pipe is provided at the top of the tank, and a drain port is provided at the bottom. One end of the liquid inlet unit extends into the tank and is fitted with a limiting plate. An air inlet is provided on the side of the liquid inlet unit. The pressure control unit is installed outside the liquid inlet unit at one end within the tank. The pressure control unit includes a sealing member sleeved on the outside of the liquid inlet unit, a first elastic member positioned below the sealing member, and a second elastic member positioned above the sealing member. The bottom end of the sealing member abuts against the first elastic member, and the top end of the sealing member is rotatably connected to the second elastic member. The end of the first elastic member away from the sealing member is fixedly connected to the limiting plate. The second elastic member is adapted to extend and retract under the pressure of the gas inside the tank, thereby driving the sealing member to slide along the length of the liquid inlet unit to block or open the air inlet.

[0008] Furthermore, the second elastic element includes a lower-opening cylinder and a sealing plate, the sealing plate being slidably and sealingly disposed within the cylinder, and the top end of the sealing element being rotatably connected to the sealing plate.

[0009] Furthermore, the second elastic element also includes a spring, which is disposed inside the cylinder and its two ends abut against the sealing plate and the inner wall of the cylinder, respectively.

[0010] Furthermore, the second elastic element consists of at least two air springs arranged in a circumferential array with the liquid inlet unit as the center.

[0011] Furthermore, the top of the sealing component is provided with a first mounting groove, and the sealing plate is provided with a second mounting groove at a position corresponding to the first mounting groove. The first mounting groove and the second mounting groove cooperate to form a receiving space, and a plurality of balls are evenly arranged in the receiving space.

[0012] Furthermore, it also includes a cleaning unit, which includes a connecting rod and a cleaning rod disposed inside the tank, and a drive assembly disposed outside the tank and driven by the liquid inlet unit. The liquid inlet unit is adapted to rotate relative to the tank under the drive of the drive assembly. A sliding groove is provided on the side wall of the liquid inlet unit, and the sliding groove extends along the length direction of the liquid inlet unit. A slider that slides in cooperation with the sliding groove is provided on the inner side of the sealing member. One end of the connecting rod is connected to the sealing member, and the other end is connected to the cleaning rod.

[0013] Furthermore, the liquid inlet unit includes a liquid inlet pipe and a rotating sleeve sleeved outside the liquid inlet pipe. The air inlet is opened on the side wall of the rotating sleeve and communicates with the liquid inlet pipe. The top of the rotating sleeve extends out of the tank body and is connected to the drive assembly for transmission. The bottom end of the rotating sleeve is equipped with the limiting plate. The side of the rotating sleeve is provided with the sliding groove. The inner side of the sealing member is provided with a slider adapted to the sliding groove.

[0014] Furthermore, it also includes a reaction vessel, with the end of the liquid inlet unit away from the tank connected to the reaction vessel, a stirring blade rotatably installed inside the reaction vessel, a stirring motor connected to the stirring blades being installed at the top of the reaction vessel, and a heating resistance wire being provided outside the reaction vessel.

[0015] Furthermore, it also includes a steam condenser tower, which is connected to the tank via a steam pipe.

[0016] The second objective of this application adopts the following technical solution:

[0017] A method for selective lithium extraction and recovery from ternary cathode powder includes the aforementioned flash evaporation treatment equipment, and further includes the following steps:

[0018] Mixing steps: Mix ternary cathode powder with water at a solid-liquid ratio of 1:(2.0-5.5) to obtain a ternary cathode solution;

[0019] Pretreatment steps: The ternary cathode solution, additives and dilute sulfuric acid are placed in a pretreatment container for mixing and reaction to obtain a pretreated slurry. The reaction time is 3-5 hours.

[0020] Lithium extraction step: The pretreated slurry after reaction is added to the reactor for selective lithium extraction to obtain a lithium-rich leaching slurry;

[0021] Flash evaporation discharge step: The leachate slurry is transferred from the reactor into the flash evaporation treatment equipment and discharged under positive pressure.

[0022] Oil removal by pressure filtration: The leachate slurry in the flash evaporation equipment is filtered through a filter press to obtain leachate. The leachate is then filtered to remove impurities and enters the oil removal device of the filter press for oil removal and impurity removal to obtain a high-concentration and high-purity lithium sulfate solution.

[0023] Sodium carbonate solution preparation steps: Add pure water to a preparation tank and heat to 60℃~70℃, then add sodium carbonate solid and stir. After stirring evenly, filter to obtain sodium carbonate solution.

[0024] Lithium carbonate preparation steps: Sodium carbonate solution is added to the reaction vessel, and lithium sulfate solution obtained in the pressure degreasing step is slowly sprayed into the reaction vessel in the form of a spray to obtain lithium carbonate. The reaction temperature is 85℃-95℃, the stirring rate is 80rpm-120rpm, and the reaction time is 60min-80min.

[0025] Filtration and drying steps: The lithium carbonate reaction slurry is centrifuged to obtain wet lithium carbonate, which is then washed 2-3 times at 90℃ and transferred to a drying device for drying. The wash water is reused. After drying, the lithium carbonate is subjected to air jet milling, demagnetization, sieving, and packaging to obtain lithium carbonate that meets battery-grade standards. Beneficial effects:

[0026] By extending the liquid inlet unit into the tank and opening the air inlet on the side wall of the liquid inlet unit, and installing a sealing component on the outside of the liquid inlet unit, and setting the first elastic component and the second elastic component at both ends of the sealing component, the sealing component can dynamically adjust the flow rate of the fluid entering the flash evaporation treatment equipment according to the gas pressure inside the tank, so that the gas pressure inside the tank is maintained at a certain level and a certain pressure difference is maintained with the input fluid, thereby ensuring the flash evaporation efficiency. Attached Figure Description

[0027] Figure 1 is a structural schematic diagram of a flash evaporation treatment device according to this application;

[0028] Figure 2 is a cross-sectional view of a flash evaporation treatment device according to this application;

[0029] Figure 3 is a cross-sectional view of a flash tank in a flash treatment device according to this application;

[0030] Figure 4 is an enlarged view of point A in Figure 3;

[0031] Figure 5 is a structural schematic diagram of a cleaning unit of a flash evaporation treatment device according to this application;

[0032] Figure 6 is a flowchart of a selective lithium extraction and recovery method for ternary cathode powder according to this application.

[0033] Reference numerals: 10, tank body; 101, steam pipe; 102, drain port; 20, liquid inlet unit; 201, liquid inlet pipe; 202, rotating sleeve; 2021, air inlet; 2022, chute; 2023, limiting plate; 30, pressure control unit; 301, sealing component; 3011, slider; 302, first elastic component; 303, second elastic component; 3031, cylinder; 3032, sealing plate; 3033, spring; 40, cleaning unit; 401, connecting rod; 402, cleaning rod; 403, reinforcing frame; 404, drive assembly; 50, steam condenser tower; 60, reaction vessel. Detailed Implementation

[0034] The present application will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0035] In the description of this application, it should be understood that the terms "center", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0037] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0038] As shown in Figures 1-5, a flash evaporation treatment device includes a tank 10, a liquid inlet unit 20, and a pressure control unit 30. A steam pipe 101 is provided at the top of the tank 10, and a drain port 102 is provided at the bottom of the tank 10. One end of the liquid inlet unit 20 extends into the tank 10 and is fitted with a limiting plate 2023. An air inlet 2021 is provided on the side of the liquid inlet unit 20. The pressure control unit 30 is installed outside the end of the liquid inlet unit 20 located inside the tank 10. The pressure control unit 30 includes a sealing element 301 sleeved on the outside of the liquid inlet unit 20. A first elastic element 302 is provided below the sealing element 301 and a second elastic element 303 is provided above the sealing element 301. The bottom end of the sealing element 301 abuts against the first elastic element 302, and the top end of the sealing element 301 is rotatably connected to the second elastic element 303. The end of the first elastic element 302 away from the sealing element 301 is fixedly connected to the limiting plate 2023. The second elastic element 303 is adapted to extend and retract under the action of air pressure in the tank 10 to drive the sealing element 301 to slide along the length of the liquid inlet unit 20 to block or open the air inlet 2021.

[0039] In this application, the sealing element 301 can be composed of two sealing units spaced apart, one above the other. During the sealing operation, the sealing unit located at the lower part will move upward under the elastic force of the first elastic element 302 and the second elastic element 303, thereby sealing the air inlet 2021. Of course, in this application, the sealing element 301 can also be a long tube with an open part on the side of the tube that communicates with the air inlet 2021. During the sealing operation, the sealing element 301 moves upward so that the open part is misaligned with the air inlet 2021 to seal the air inlet 2021. During normal operation, the sealing element 301 moves downward so that the open part is aligned and communicates with the air inlet 2021.

[0040] In this scheme, a reaction vessel 60 and a steam condenser tower 50 are also included. The end of the liquid inlet unit 20 away from the tank 10 is connected to the reaction vessel 60. A stirring blade is rotatably installed inside the reaction vessel 60. A stirring motor connected to the stirring blade is installed at the top of the reaction vessel 60. A heating resistance wire is provided outside the reaction vessel 60. The steam condenser tower 50 is connected to the tank through a steam pipe.

[0041] During operation, the pre-prepared slurry enters the reactor. The stirring motor drives the stirring blades to agitate the slurry, while the heating resistance wire heats the reactor. The pre-prepared slurry reacts under heat to increase its lithium content. Simultaneously, the pressure in the reactor increases after heating, and the pre-prepared slurry is forced into the flash evaporation equipment through the inlet unit 20 under the pressure. At this time, the tank 10 is in a non-operating state, and both the first elastic element 302 and the second elastic element 303 are in a compressed state. The lithium sulfate fluid to be flash-evaporated enters the tank 10 through the air inlet 2021. Because the pressure inside the tank 10 is lower than that in the reactor, the pressure of the pre-prepared slurry decreases after entering the tank 10, causing the boiling point of the high-pressure, high-temperature fluid exiting the air inlet 2021 to decrease. Upon entering the tank, the water in the fluid will rapidly vaporize, thereby increasing the lithium content in the fluid. The concentration of lithium sulfate; during the water vaporization process, the pressure inside the tank 10 continuously increases, thereby squeezing the second elastic element 303 to compress it. At the same time, the first elastic element 302 extends, driving the sealing element 301 to slide upward along the length of the liquid inlet unit 20 to block the air inlet 2021. During the process of the sealing element 301 blocking the air inlet 2021, the flow rate of fluid entering the tank 10 continuously decreases, thereby reducing the rate of pressure rise inside the tank 10 until the sealing element 301 completely blocks the air inlet 2021, at which point the gas pressure inside the tank 10 reaches its maximum value. Then, the gas pressure inside the tank 10 decreases as steam and the high-concentration lithium sulfate fluid obtained after flash evaporation are discharged. The second elastic element 303 extends, the first elastic element 302 compresses, and the sealing element 301 opens the air inlet 2021, allowing the fluid to re-enter the tank 10 for flash evaporation treatment.

[0042] In addition, since some lithium is also evaporated during the evaporation process of the slurry, after the steam is discharged from the tank 10, it needs to enter the steam condenser tower 50 and be injected back into the pre-reaction vessel after condensation treatment, i.e., the pretreatment step, to make full use of the lithium.

[0043] Since the evaporation effect of flash evaporation is related to the pressure and temperature inside the flash evaporation equipment, in this application, the liquid inlet unit 20 is extended into the tank 10, the air inlet 2021 is opened on the side wall of the liquid inlet unit 20, and a sealing member 301 is sleeved on the outside of the liquid inlet unit 20. The first elastic member 302 and the second elastic member 303 are used so that the sealing member 301 can dynamically adjust the flow rate of the fluid entering the flash evaporation equipment according to the air pressure inside the tank 10, so that the air pressure inside the tank 10 is maintained at a certain level and a certain pressure difference is maintained with the input fluid, thereby ensuring the flash evaporation effect.

[0044] Specifically, in this embodiment, the second elastic member 303 includes a lower-opening cylindrical body 3031 and a sealing plate 3032. The sealing plate 3032 is slidably and sealingly disposed inside the cylindrical body 3031, and the top end of the sealing member 301 is rotatably connected to the sealing plate 3032.

[0045] Since the sealing plate 3032 is slidably sealed inside the cylinder 3031, a sealed space isolated from the outside is formed inside the cylinder 3031. The sealed space is filled with gas, so that when the gas pressure inside the tank 10 rises, there is a pressure difference between the gas pressure inside the tank 10 and the gas pressure inside the sealed space. The gas inside the tank 10 can squeeze the sealing plate 3032, causing the sealing plate to slide along the axial direction of the cylinder 3031 to contract, thereby allowing the sealing member 301 to move upward to block the air inlet 2021.

[0046] When the air pressure inside the tank 10 drops, the compressed gas in the sealed space can expand to push the sealing plate to slide along the cylinder 3031 axially to extend, so that the sealing member 301 can move downward to open the air inlet 2021.

[0047] Furthermore, this configuration allows for automatic control of the sealing element 301 to block the air inlet 2021 when the second elastic element 303 malfunctions. Specifically, when the second elastic element 303 malfunctions, such as leaking air, the internal space of the second elastic element 303 is directly connected to the tank body 10. At this time, only the spring 3033 of the second elastic element 303 is working. When the second elastic element 303 is in its normal state, the elastic force it generates is produced by the elastic force of the spring 3033 and the deformation of the body of the second elastic element 303. The elastic components are composed of elastic elements, and the elastic force of the first elastic element 302 is equal to the elastic force of the second elastic element 303. Therefore, due to the lack of elastic force generated when the body of the second elastic element 303 is deformed, the elastic force of the first elastic element 302 is greater than that of the second elastic element 303. The first elastic element 302 is extended and the second elastic element 303 is contracted, thereby causing the sealing element 301 to move upward, thereby sealing the air inlet 2021 to prevent the air inlet 2021 from continuously entering liquid, which would cause the pressure inside the tank 10 to become too high and cause it to burst.

[0048] Furthermore, since the top of the sealing element 301 is rotatably connected to the top of the second elastic element 303, after the first elastic element 302 fails, the second elastic element 303 deforms under the action of the air pressure inside the tank 10, which can drive the sealing element 301 to move upward to block the air inlet 2021, so as to prevent the air inlet 2021 from continuously entering liquid, causing the pressure inside the tank 10 to become too high and burst.

[0049] In addition, to ensure the extension and retraction effect of the second elastic element 303, in this embodiment, the second elastic element 303 further includes a spring 3033, the spring 3033 is disposed inside the cylinder 3031 and the two ends of the spring 3033 respectively abut against the sealing plate 3032 and the inner wall of the cylinder 3031.

[0050] To reduce the friction between the sealing member 301 and the second elastic member 303, in this embodiment, the top end of the sealing member 301 is provided with a first mounting groove, and the sealing plate 3032 is provided with a second mounting groove at a position corresponding to the first mounting groove. The first mounting groove and the second mounting groove cooperate to form a receiving space, and a plurality of balls are evenly arranged in the receiving space.

[0051] Of course, in this application, in order to avoid insufficient sealing between the sealing plate 3032 and the cylinder 3031, and the gas in the tank 10 directly entering the cylinder 3031, causing the second elastic element 303 to fail, the second elastic element 303 can be replaced by an air spring assembly with better airtightness in this embodiment. The air spring assembly consists of at least two air springs arranged in a circumferential array with the liquid inlet unit 20 as the center.

[0052] In addition, a detection pipe can be added to the tank 10. The end of the detection pipe is connected to an external recovery device. A rupture disc is installed on the detection pipe. When the air pressure inside the tank 10 exceeds the specified upper limit, the rupture disc will rupture under the pressure of the air pressure inside the tank 10 to release the pressure, thereby preventing the tank 10 from being over-pressurized and exploding.

[0053] In addition, to prevent crystals formed after flash evaporation from adhering to the inner wall of the tank 10, a cleaning unit 40 is also provided inside the tank 10 in this embodiment. The cleaning unit 40 includes a connecting rod 401 and a cleaning rod 402 disposed inside the tank 10, and a driving assembly 404 disposed outside the tank 10 and connected to the liquid inlet unit 20 in a transmission manner. The liquid inlet unit 20 is adapted to rotate relative to the tank 10 under the drive of the driving assembly 404. A sliding groove 2022 is provided on the side wall of the liquid inlet unit 20, and the sliding groove 2022 extends along the length direction of the liquid inlet unit 20. A slider 3011 that slides and engages with the sliding groove 2022 is provided on the inner side of the sealing member 301. One end of the connecting rod 401 is connected to the sealing member 301, and the other end is connected to the cleaning rod 402.

[0054] During operation, the drive assembly 404 drives the liquid inlet unit 20 to rotate, thereby causing the sealing member 301, which is slidably mounted on the liquid inlet unit 20, to rotate. This, in turn, drives the cleaning rod 402 to rotate via the connecting rod 401, cleaning the inner wall of the tank 10 to scrape away crystals on the inner wall of the tank 10. Since the connecting rod 401 is connected to the sealing member 301, as the sealing member 301 drives the connecting rod 401 to rotate, the sealing member 301 will also drive the connecting rod 401 to move up and down. This allows the cleaning rod 402 to move up and down during rotation, agitating the incoming fluid and improving the flash evaporation effect.

[0055] Specifically, in this embodiment, the liquid inlet unit 20 includes a liquid inlet pipe 201 and a rotating sleeve 202 sleeved outside the liquid inlet pipe 201. The air inlet 2021 is opened on the side wall of the rotating sleeve 202 and communicates with the liquid inlet pipe 201. The top end of the rotating sleeve 202 extends out of the tank body 10 and is connected to the drive assembly 404. The bottom end of the rotating sleeve 202 is equipped with the limiting plate 2023. The side of the rotating sleeve 202 is provided with the sliding groove 2022. The inner side of the sealing member 301 is provided with a slider 3011 adapted to the sliding groove 2022.

[0056] In this embodiment, the drive assembly 404 consists of a drive motor and a transmission gear set installed on the top of the tank 10, a drive gear installed on the motor shaft of the drive motor, and a driven gear installed on the top of the rotating sleeve 202. The drive gear is connected to the driven gear through the transmission gear set, so that when the drive motor is working, it can drive the driven gear to rotate through the transmission gear set, thereby driving the rotating sleeve 202 to rotate, and then the cleaning rod 402 is rotated in conjunction with the sealing member 301, thereby cleaning the inner wall of the tank 10.

[0057] In order to facilitate the movement of the sealing component 301 along the length of the rotating sleeve 202, in this embodiment, a bearing can be provided inside the sealing component 301, and the rotating sleeve 202 is sleeved in the bearing, so as to convert the friction between the sealing component 301 and the rotating sleeve 202 from sliding friction to rolling friction, thereby reducing the wear of the rotating sleeve 202 during the movement of the sealing component 301.

[0058] In addition, in order to extend the service life of the first elastic element 302 and the sealing element 301, in this embodiment, the connecting rod 401 and the cleaning rod 402 are made of titanium alloy material, thereby reducing the overall weight of the cleaning unit 40 and thus reducing the impact of the cleaning unit 40 on the first elastic element 302 and the sealing element 301.

[0059] In order to improve the cleaning effect, in this embodiment, multiple cleaning rods 402 and multiple connecting rods 401 are provided, and the connecting rods 401 and the cleaning rods 402 are provided in a one-to-one correspondence. The cleaning unit 40 includes a reinforcing frame 403, which is adapted to connect multiple cleaning rods 402 into one unit.

[0060] As shown in Figure 6, a method for selective lithium extraction and recovery from ternary cathode powder includes the aforementioned flash evaporation equipment and further includes the following steps:

[0061] Mixing steps: Mix ternary cathode powder with water at a solid-liquid ratio of 1:(2.0-5.5) to obtain a ternary cathode solution;

[0062] Pretreatment steps: The ternary cathode solution, additives and dilute sulfuric acid are placed in a pretreatment container for mixing and reaction to obtain a pretreated slurry. The reaction time is 3-5 hours.

[0063] Lithium extraction step: The pretreated slurry after reaction is added to the reactor for selective lithium extraction to obtain a lithium-rich leaching slurry;

[0064] Flash evaporation discharge step: The leachate slurry is transferred from the reactor into the flash evaporation treatment equipment and discharged under positive pressure.

[0065] Oil removal by pressure filtration: The leachate slurry in the flash evaporation equipment is filtered through a filter press to obtain leachate. The leachate is then filtered to remove impurities and enters the oil removal device of the filter press for oil removal and impurity removal to obtain a high-concentration and high-purity lithium sulfate solution.

[0066] Sodium carbonate solution preparation steps: Add pure water to a preparation tank and heat to 60℃~70℃, then add sodium carbonate solid and stir. After stirring evenly, filter to obtain sodium carbonate solution.

[0067] Lithium carbonate preparation steps: Sodium carbonate solution is added to the reaction vessel, and lithium sulfate solution obtained in the pressure degreasing step is slowly sprayed into the reaction vessel in the form of a spray to obtain lithium carbonate. The reaction temperature is 85℃-95℃, the stirring rate is 80rpm-120rpm, and the reaction time is 60min-80min.

[0068] Filtration and drying steps: The lithium carbonate reaction slurry is centrifuged to obtain wet lithium carbonate, which is then washed 2-3 times at 90℃ and transferred to a drying device for drying. The wash water is reused. After drying, the lithium carbonate is subjected to air jet milling, demagnetization, sieving, and packaging to obtain lithium carbonate that meets battery-grade standards.

[0069] The above description, in conjunction with specific embodiments, provides a further detailed explanation of this application. It should not be construed that the specific implementation of this application is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of this application, and all such deductions or substitutions should be considered to fall within the scope of protection defined by the claims submitted in this application.

Claims

1. A flash evaporation treatment device, characterized in that: The device includes a tank, a liquid inlet unit, and a pressure control unit. A steam pipe is located at the top of the tank, and a drain port is located at the bottom. One end of the liquid inlet unit extends into the tank and is fitted with a limiting plate. An air inlet is located on the side of the liquid inlet unit. The pressure control unit is installed outside the liquid inlet unit at one end within the tank. The pressure control unit includes a sealing element sleeved on the outside of the liquid inlet unit, a first elastic element located below the sealing element, and a second elastic element located above the sealing element. The bottom end of the sealing element abuts against the first elastic element, and the top end of the sealing element is rotatably connected to the second elastic element. The end of the first elastic element away from the sealing element is fixedly connected to the limiting plate. The second elastic element is adapted to expand and contract under the pressure of the air inside the tank, thereby driving the sealing element to slide along the length of the liquid inlet unit to block or open the air inlet.

2. The flash evaporation treatment equipment according to claim 1, characterized in that: The second elastic element includes a lower-opening cylinder and a sealing plate. The sealing plate is slidably and sealingly disposed within the cylinder, and the top end of the sealing element is rotatably connected to the sealing plate.

3. The flash evaporation treatment equipment according to claim 2, characterized in that: The second elastic element also includes a spring, which is disposed inside the cylinder and its two ends abut against the sealing plate and the inner wall of the cylinder, respectively.

4. The flash evaporation treatment equipment according to claim 1, characterized in that: The second elastic element consists of at least two air springs arranged in a circular array with the liquid inlet unit as the center.

5. The flash evaporation treatment equipment according to claim 2, characterized in that: The top of the sealing component is provided with a first mounting groove, and the sealing plate is provided with a second mounting groove at a position corresponding to the first mounting groove. The first mounting groove and the second mounting groove cooperate to form a receiving space, and a plurality of balls are evenly arranged in the receiving space.

6. The flash evaporation treatment equipment according to claim 1, characterized in that: It also includes a cleaning unit, which includes a connecting rod and a cleaning rod disposed inside the tank, and a drive assembly disposed outside the tank and connected to the liquid inlet unit. The liquid inlet unit is adapted to rotate relative to the tank under the drive of the drive assembly. The side wall of the liquid inlet unit is provided with a sliding groove that extends along the length of the liquid inlet unit. The inner side of the sealing member is provided with a slider that slides in cooperation with the sliding groove. One end of the connecting rod is connected to the sealing member, and the other end is connected to the cleaning rod.

7. The flash evaporation treatment equipment according to claim 6, characterized in that: The liquid inlet unit includes a liquid inlet pipe and a rotating sleeve sleeved outside the liquid inlet pipe. The air inlet is opened on the side wall of the rotating sleeve and communicates with the liquid inlet pipe. The top of the rotating sleeve extends out of the tank and is connected to the drive assembly for transmission. The bottom of the rotating sleeve is equipped with the limiting plate. The side of the rotating sleeve is provided with the sliding groove. The inner side of the sealing component is provided with a slider adapted to the sliding groove.

8. The flash evaporation treatment equipment according to claim 1, characterized in that: It also includes a reaction vessel, with the end of the liquid inlet unit away from the tank connected to the reaction vessel, a stirring blade rotatably installed inside the reaction vessel, a stirring motor connected to the stirring blades in a driving connection installed at the top of the reaction vessel, and a heating resistance wire installed outside the reaction vessel.

9. The flash evaporation treatment equipment according to claim 1, characterized in that: It also includes a steam condenser tower, which is connected to the tank via a steam pipe.

10. A method for selective lithium extraction and recovery from ternary cathode powder, characterized in that... The flash evaporation treatment equipment according to claims 1-9 further includes the following steps: Mixing steps: Mix ternary cathode powder with water at a solid-liquid ratio of 1:(2.0-5.5) to obtain a ternary cathode solution; Pretreatment steps: The ternary cathode solution, additives and dilute sulfuric acid are placed in a pretreatment container for mixing and reaction to obtain a pretreated slurry. The reaction time is 3-5 hours. Lithium extraction step: The pretreated slurry after reaction is added to the reactor for selective lithium extraction to obtain a lithium-rich leaching slurry; Flash evaporation discharge step: The leachate slurry is transferred from the reactor into the flash evaporation treatment equipment and discharged under positive pressure. Oil removal by pressure filtration: The leachate slurry in the flash evaporation equipment is filtered through a filter press to obtain leachate. The leachate is then filtered to remove impurities and enters the oil removal device of the filter press for oil removal and impurity removal to obtain a high-concentration and high-purity lithium sulfate solution. Sodium carbonate solution preparation steps: Add pure water to a preparation tank and heat to 60℃~70℃, then add sodium carbonate solid and stir. After stirring evenly, filter to obtain sodium carbonate solution. Lithium carbonate preparation steps: Sodium carbonate solution is added to the reaction vessel, and lithium sulfate solution obtained in the pressure degreasing step is slowly sprayed into the reaction vessel in the form of a spray to obtain lithium carbonate. The reaction temperature is 85℃-95℃, the stirring rate is 80rpm-120rpm, and the reaction time is 60min-80min. Filtration and drying steps: The lithium carbonate reaction slurry is centrifuged to obtain wet lithium carbonate, which is then washed 2-3 times at 90℃ and transferred to a drying device for drying. The wash water is reused. After drying, the lithium carbonate is subjected to air jet milling, demagnetization, sieving, and packaging to obtain lithium carbonate that meets battery-grade standards.

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