A positive electrode material fluidized sintering device and a positive electrode material sintering method for dynamic density separation

Abstract

This invention relates to the field of cathode material preparation technology, specifically to a dynamic density-sorting fluidized bed sintering apparatus for cathode materials. The apparatus includes a gas heater and a fluidized bed sintering furnace. The fluidized bed sintering furnace is vertically arranged and comprises a fluidized bed sintering reaction unit, a Venturi unit, and a collection unit arranged sequentially from top to bottom. After the cathode material reaches the sintering standard, due to the increase in density, the cathode material can fall through the Venturi unit into the collection unit for sorting. This arrangement allows for sorting of the cathode material during sintering, ensuring that sintered cathode material particles can leave the fluidized bed sintering reaction unit in a timely manner, reducing the space occupied by the fluidized bed sintering reaction unit, freeing up reaction space for non-compliant particles, and ensuring that the sintering gas can fully contact the non-compliant particles, thereby improving sintering efficiency.

Description

Technical Field

[0001] This invention relates to the field of cathode material preparation technology, specifically to a dynamic density sorting cathode material fluidized bed sintering apparatus and a cathode material sintering method. Background Technology

[0002] Lithium-ion batteries are increasingly widely used in mobile phones, computers, tablets, Bluetooth headsets, power tools, automobiles, energy storage, and other fields. The cathode material, the source of lithium ions and electrons in the battery, is one of the most critical factors determining the battery's energy density, voltage, safety, and cost. Sintering is a crucial step in cathode material preparation; by controlling parameters such as sintering temperature, atmosphere, and time, the structure and performance of the material can be precisely controlled, ultimately affecting the battery's core indicators such as energy density, cycle life, and safety.

[0003] In the existing technology, the sintering of lithium cathode materials generally adopts static furnace (push plate kiln, roller kiln). During the sintering process, the precursor particles are statically stacked in the sagger, which has the following prominent problems: (1) Poor sintering uniformity: Static accumulation of particles leads to uneven heating, excessive local adhesion or incomplete reaction, and product density deviation > 15%; (2) Limited production capacity: The sagger loading capacity is limited, and it is necessary to clean the materials adhering to the wall frequently, resulting in low production efficiency; (3) High energy consumption: The static furnace has low heat transfer efficiency, and the heat of high temperature tail gas is rarely recovered, with an energy consumption ratio of 3.5-4.0 kW・h / kg.

[0004] Therefore, there is an urgent need to invent a dynamic density sorting fluidized bed sintering device and a sintering method for cathode materials to solve the aforementioned technical problems. Summary of the Invention

[0005] One of the objectives of this invention is to provide a fluidized bed sintering apparatus for positive electrode materials with dynamic density sorting, which improves sintering efficiency and ensures uniform heating of the positive electrode material during sintering by performing density sorting simultaneously with the sintering process.

[0006] To solve the above-mentioned technical problems, this application adopts the following technical solution: A fluidized bed sintering apparatus for dynamic density sorting of cathode materials is provided, comprising a gas heater and a fluidized bed sintering furnace. The fluidized bed sintering furnace is vertically arranged and includes, from top to bottom, a fluidized bed sintering reaction unit, a Venturi unit, and a collecting unit. The Venturi unit includes, from top to bottom, an expansion section, a throat section, and a contraction section. The cross-sectional area of ​​the expansion section and the contraction section gradually increases in the direction away from the throat section. The gas heater is provided with an inlet and is connected to the contraction section. The upper end of the collecting unit is connected to the contraction section, and the lower end of the collecting unit is connected to the outlet. The lower end of the fluidized bed sintering reaction unit is connected to the expansion section and is provided with an inlet. The upper end of the fluidized bed sintering reaction unit is connected to a recovery device.

[0007] Furthermore, the contraction section is a circular arc transition structure, and the axial height H and the radius R of the contraction section satisfy: R=H, and the diameter D1 of the inlet end of the contraction section is 3-5 times the diameter d of the throat section; The throat segment is cylindrical in shape, and the formula for calculating the diameter d of the throat segment is: Where Q is the sintering gas flow rate (m³ / s). 3 / s), u t For the critical wind speed u t =1.2-1.5×u mf u mf The critical fluidization velocity is given by the throat segment length L, which is 1-2 times the throat diameter d, and k is a correction factor. The expansion section is tapered: the diameter of the inlet end of the expansion section is equal to the diameter d of the throat section, the diameter D2 of the outlet end of the expansion section is 3.5-5.5 times the diameter d of the throat section, and the diffusion angle α is 75-80°.

[0008] Furthermore, the diameter of the fluidized bed sintering reaction unit is 3.5-5.5 times the diameter d of the throat section, and the height of the fluidized bed sintering reaction unit is 5-8 times the diameter.

[0009] Furthermore, the recycling device includes a cyclone dust collector and a bag filter dust collector. The top of the cyclone dust collector is provided with an air inlet connected to the fluidized bed sintering reaction unit and an air outlet connected to the bag filter dust collector. Both the cyclone dust collector and the bag filter dust collector are provided with a discharge port at their bottoms.

[0010] Furthermore, the recovery device also includes a waste heat boiler, which is located between the cyclone dust collector and the bag filter, and is connected to the air outlet of the cyclone dust collector and the air inlet of the bag filter, respectively.

[0011] Furthermore, a preheating feeding device is also provided, which includes a first fluidized bed collector and a second fluidized bed collector. The second fluidized bed collector is connected to the outlet of the waste heat boiler and the outlet of the bag filter, and is also connected to the first fluidized bed collector. The second fluidized bed collector is also provided with a feed inlet. The first fluidized bed collector is connected to the outlet of the cyclone dust collector and is also connected to the feed inlet of the fluidized bed sintering reaction unit. Both the first fluidized bed collector and the second fluidized bed collector are provided with fluidizing plates to transform the material into a fluidized state.

[0012] Furthermore, a return spray gun is also provided at the feed inlet of the fluidized bed sintering reaction unit.

[0013] Furthermore, a cooling gas distribution plate is provided at the lower end of the material collection unit to achieve controllable cooling of the material.

[0014] Furthermore, the inner walls of the cavities and pipes of the gas heater, the fluidized bed sintering furnace, and the recycling device are all coated with either alumina ceramic or silicon carbide ceramic.

[0015] The second objective of this invention is to provide a cathode material sintering method using a dynamic density sorting cathode material fluidized bed sintering apparatus as described in any one of the above-mentioned claims, comprising the following steps: S1. The precursor raw material is fed into the second fluidized material collector. Fluidized gas is introduced into the second fluidized material collector to make the precursor raw material and the powder material recovered by the waste heat boiler and bag dust collector fluidized and mixed to exchange heat to form the first mixture material, wherein the heating rate of the first mixture material is <5℃ / min. S2. The first mixture is fed into the first fluidized bed collector. Fluidized gas is introduced into the first fluidized bed collector to make the first mixture and the particles recovered by the cyclone dust collector fluidized and mixed to exchange heat to form the second mixture. The temperature of the second mixture rises to 200℃-400℃ when it leaves the first fluidized bed collector. The heating rate of the second mixture is 5℃-10℃ / min. S3. The sintering gas is heated to 700-950℃ by a gas heater, and after being buffered in the aggregate unit, it enters the fluidized bed sintering reaction unit through the Venturi unit, and forms a turbulent fluidized bed in the fluidized bed sintering reaction unit, wherein the apparent gas velocity of the fluidized bed is 0.5-2.0m / s. S4. The second mixture is injected into the fluidized bed sintering furnace through the feed gun and sintered in the fluidized bed circulation. The sintering holding time is 5-15 hours and the particle density increases with the sintering process. S5. After sintering, the particles that meet the density standard enter the collection unit in sequence through the expansion section, throat section and contraction section under the airflow separation action of the Venturi unit. The cooling gas distribution plate in the collection unit introduces room temperature nitrogen or air to cool the sintered particles to ≤80℃. S6. The substandard particles carried by the top exhaust gas of the fluidized bed sintering reaction unit are sequentially fed into the cyclone dust collector, waste heat boiler and bag dust collector for recycling. The recycled particles are fed into the first fluidized bed collector or the second fluidized bed collector and sprayed into the fluidized bed sintering furnace through the feed gun for circulating heating. S7. The gas temperature at the outlet of the cyclone dust collector is 700-900℃. It enters the waste heat boiler to cool down to 150-200℃ to recover heat, and then is discharged after being purified by the bag filter.

[0016] The beneficial effects of this invention are as follows: During the sintering process of the cathode material, as the cathode material particles undergo atomic diffusion and rearrangement at high temperature, forming a stable crystal structure, the density of the sintered cathode material increases. Based on this phenomenon, density sorting can be used to distinguish between sintered particles that meet the standards and those that do not. The fluidized bed sintering furnace provided in this application includes a fluidized bed sintering reaction unit, a Venturi unit, and a material collection unit arranged sequentially from top to bottom. After the sintering gas is heated in the gas heater, it forms a stable gas flow that passes through the Venturi unit and enters the fluidized bed sintering reaction unit. After the material is introduced into the fluidized bed sintering reaction unit, it undergoes... The cathode material is fluidized and sintered under the action of sintering gas. Since the cathode material is in uniform contact with the sintering gas in the fluidized state, the uniform sintering of the cathode material can be guaranteed. After the cathode material reaches the sintering standard, due to the increase in density, the cathode material can fall into the collection unit through the Venturi unit to complete the sorting. This setting allows the cathode material to be sorted during the sintering process, ensuring that the cathode material particles that have reached the sintering standard can leave the fluidized sintering reaction unit in time, reducing the space occupied by the fluidized sintering reaction unit, freeing up the reaction space for the sintering of the particles that have not reached the standard, and ensuring that the sintering gas can fully contact the particles that have not reached the standard, thereby improving the sintering efficiency. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the structure of the present invention; Wherein: 1-Gas heater; 2-Fluorescent sintering furnace; 21-Fluorescent sintering reaction unit; 22-Venturi unit; 221-Expansion section; 222-Throat section; 223-Contraction section; 23-Collection unit; 3-Recovery device; 31-Cyclone dust collector; 32-Bag dust collector; 33-Waste heat boiler; 4-Preheating feeding device; 41-First fluidized bed collector; 42-Second fluidized bed collector; 5-Return spray gun. Detailed Implementation

[0018] The technical solutions of the embodiments of this application 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 this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terminology used in the specification of this application is for the purpose of describing specific embodiments only and is not intended to limit this application.

[0019] The present invention will be further described in detail below with reference to the accompanying drawings, but this is not intended to limit the scope of the invention.

[0020] The applicant has discovered that the existing method for sintering cathode materials involves using a static furnace (pusher kiln, roller kiln) to place a sagger containing the material on a pusher or roller and move it slowly through a long tunnel kiln, passing through the preheating zone, high-temperature reaction zone, and cooling zone in sequence to complete the sintering of the material. This method may cause the material to be statically stacked in the sagger, and the static accumulation of particles leads to uneven heating, local over-adhesion, or incomplete reaction.

[0021] Therefore, some cathode materials are sintered by mixing the material and fuel and passing them into a fluidized bed for sintering. Although this method improves uniformity, it does not solve the problem of controlling the reaction endpoint and cannot identify and separate qualified particles in real time.

[0022] This application achieves material screening during the sintering process by setting a Venturi unit 22 below the fluidized bed sintering reaction unit 21, using sintering gas flow to screen the material. This provides an exit mechanism for the sintered material, allowing the sintered material to leave the fluidized bed sintering reaction unit 21 in a timely manner, while particles that do not meet the sintering standards are circulated and sintered within the fluidized bed sintering reaction unit 21. The material is neither over-sintered nor under-sintered, improving the pass rate of the sintered material. Furthermore, the timely exit of the sintered material from the fluidized bed sintering reaction unit 21 frees up space for the under-sintered material, which is beneficial to improving sintering efficiency.

[0023] like Figure 1 As shown, this application provides a dynamic density sorting positive electrode material fluidized bed sintering equipment, including a gas heater 1 and a fluidized bed sintering furnace 2. The gas heater 1 is used to heat the sintering gas and pass the heated gas into the fluidized bed sintering furnace 2 to sinter the material. The gas heater 1 is provided with an air inlet and a fan is provided at the air inlet. The flow rate of the gas entering the fluidized bed sintering furnace 2 can be adjusted by controlling the fan. The fluidized bed sintering furnace 2 is used to mix the material and the sintering gas for fluidized bed sintering.

[0024] The fluidized bed sintering furnace 2 is vertically arranged and includes a fluidized bed sintering reaction unit 21, a venturi unit 22 and a collection unit 23 arranged from top to bottom. The upper end of the collection unit 23 is connected to the venturi unit 22 and is used to collect the sintered material. The vertical arrangement of the fluidized bed sintering furnace 2 allows the material to move downward under the action of gravity and be spontaneously screened.

[0025] The Venturi unit 22 includes an expansion section 221, a throat section 222, and a contraction section 223 arranged sequentially from top to bottom. The cross-sectional areas of the expansion section 221 and the contraction section 223 gradually increase away from the throat section 222. The gas heater 1 is connected to the contraction section 223. The sintering gas is first introduced into the collection unit 23 for buffering and pressure stabilization, and then enters the contraction section 223 from the upper end of the collection unit 23. The contraction section 223 is used to guide the sintering gas to accelerate smoothly and uniformly, while the fluid velocity in the throat section 222 reaches its maximum, the static pressure drops to its minimum, and the lift on the material is maximized. It is used to determine the critical sorting density along with the sintering gas flow rate. The expansion section 221 gradually reduces the gas velocity and stabilizes the downstream flow field, so that the gas flow enters the fluidized sintering reaction unit 21 and mixes with the material to form a stable fluidized bed.

[0026] The fluidized bed sintering reaction unit 21 is used for fluidized bed sintering of materials. The lower end of the fluidized bed sintering reaction unit 21 is connected to the Venturi unit 22 and is provided with a feed inlet. The material is introduced into the fluidized bed sintering reaction unit 21 through the feed inlet, and the sintering gas is introduced into the fluidized bed sintering reaction unit 21 through the Venturi unit 22. The sintering gas and the material are mixed and sintered at the fluidized bed sintering reaction unit 21.

[0027] After the material is introduced into the fluidized bed sintering reaction unit 21, it is sintered in a fluidized state under the blowing of sintering gas. At this time, the material undergoes atomic diffusion and rearrangement at high temperature to form a stable crystal structure. At the same time, the porosity of the material decreases, which increases the density of the material. As the sintering process proceeds, the density of the material continuously increases, and the lift force of the sintering gas on the material continuously decreases. When the material flows to the Venturi unit 22, the gravity of some of the material is greater than the lift force provided by the sintering gas in the throat section 222. The material falls through the Venturi unit 22 to the collection unit 23, while the remaining material with greater lift is blown back into the fluidized bed sintering reaction unit 21 for sintering. The lower end of the collection unit 23 is connected to the discharge port. The material falling into the collection unit 23 is discharged from the fluidized bed sintering furnace 2 through the discharge port. The upper end of the fluidized bed sintering reaction unit 21 is connected to the recovery device 3. The sintering gas is discharged from the upper end of the fluidized bed sintering reaction unit 21 to the recovery device 3 for heat recovery and recovery of substandard materials.

[0028] Preferably, the gas heater 1 uses a nickel-chromium alloy (Cr20Ni80) resistance wire as the heating element, which can directly heat air, nitrogen or inert gas to above 900°C. Heating with resistance wire eliminates the need for fuel and the absence of ash after combustion, which is beneficial for material recycling and cyclic sintering, and prevents ash accumulation from affecting sintering efficiency.

[0029] Preferably, the shrinkage section 223 has a circular arc transition structure, which is the shape after the circular arc has rotated one revolution. The axial height H and the radius R of the circular arc of the shrinkage section 223 satisfy: R=H, and the diameter D1 of the inlet end of the shrinkage section 223 is 3-5 times the diameter d of the throat section 222. This setting allows the sintering gas to accelerate smoothly along the circular arc surface when it enters the shrinkage section 223 from the collection unit 23, avoiding particle agglomeration caused by local turbulence. The throat section 222 is cylindrical in shape, and the formula for calculating the diameter d of the throat section 222 is: where Q is the sintering gas flow rate (m³ / s). 3 / s), ut is the critical separation velocity ut=1.2-1.5×umf, where umf is the critical fluidization velocity, which is the minimum fluid velocity at which the bed transitions from a "fixed bed" state to a "fluidized bed" state when the fluid flows upward through a particle bed. The length L of the throat section 222 is 1-2 times the throat diameter d to ensure a stable velocity gradient between the gas and solid phases within the throat, achieving density separation; k is a correction coefficient, with a value of 0.8-1.2, which needs to be adjusted according to the material type. For example, when the cathode material is NCM / LCO, k is 1.0-1.2, and when it is LFP / LMO, k is 0.8-1.0. The diameter d of the throat section 222 also needs to be determined based on the target density ρ and critical fluidization velocity umf of the cathode material after sintering. It is necessary to ensure that particles with a density ≥ ρ can overcome the airflow resistance at the throat section 222 and enter the collection unit 23. The expansion section 221 is tapered: the diameter of the inlet end of the expansion section 221 is equal to the diameter d of the throat section 222, the diameter D2 of the outlet end of the expansion section 221 is 3.5-5.5 times the diameter d of the throat section 222, and the diffusion angle α is 75-80°. This configuration allows the high-speed airflow (velocity u) accelerated by the throat section 222 to... t =12-35m / s) and smoothly decelerate in the diffusion section (the outlet flow velocity is reduced to u=1.0-2.0m / s) to avoid fluctuations in the fluidized bed caused by severe turbulence. At the same time, the unqualified particles after sorting are uniformly introduced into the fluidized bed of the fluidized bed sintering furnace 2 to ensure the continuity of particle circulation sintering.

[0030] The aforementioned Venturi unit 22 reduces pressure loss through the arc transition of the contraction section 223, where the pressure loss is ≤5kPa. The precise dimensional design of the throat section 222 achieves a density sorting accuracy of ≥99%, with a sorting deviation of ≤0.05g / cm for particles with a diameter of 2-10μm. 3 The large-angle design of the diffusion section ensures that the airflow is smoothly introduced into the fluidized bed, and the radial velocity deviation of the fluidized sintering reaction unit 21 is ≤5%. The three work together to achieve the integrated function of fluidization power, density sorting and bed stability.

[0031] Preferably, the diameter of the fluidized bed sintering reaction unit 21 is 3.5-5.5 times the diameter d of the throat section 222, and the height of the fluidized bed sintering reaction unit 21 is 5-8 times the diameter. The fluidized bed of the fluidized bed sintering reaction unit 21 is a turbulent fluidized bed, and the apparent gas velocity is controlled at 0.5-2.0 m / s, so that the precursor particles circulate in the furnace ≥ 5 times / h, thus extending the sintering reaction time. The structural parameters of the fluidized bed sintering reaction unit 21 are determined based on fluidized bed theory and the process requirements of the sintering material. More preferably, the dense phase bed region of the fluidized bed sintering reaction unit 21 is located in the lower half of the straight section, and the radial temperature deviation of this part is ≤ 3℃. The free space height of the fluidized bed sintering reaction unit 21 is located in the upper half of the straight section, and the diameter of this part is consistent with that of the dense phase region. The gas velocity gradually decreases due to the increase of porosity, which is the sorting zone for particles entrained in the sintering gas, which can reduce the entrained particles by 10%-50%.

[0032] Preferably, the recycling device 3 includes a cyclone dust collector 31 and a bag filter 32. The top of the cyclone dust collector 31 is provided with an air inlet connected to the fluidized bed sintering reaction unit 21 and an air outlet connected to the bag filter 32. Both the bag filter 32 and the bag filter 32 are provided with discharge ports at their bottoms. When the sintering gas flowing out of the fluidized bed sintering reaction unit 21 passes through the cyclone dust collector 31 and the bag filter 32, the material mixed in the sintering gas is collected and flows out from the discharge port, and re-enters the fluidized bed sintering reaction unit 21 for sintering again. While reusing the material, the heat of the material can also be reused.

[0033] Preferably, the recovery device 3 further includes a waste heat boiler 33, which is located between the cyclone dust collector 31 and the bag filter 32 and is connected to the outlet of the cyclone dust collector 31 and the inlet of the bag filter 32 respectively. When the sintering gas passes through the waste heat boiler 33, the heat is transferred to the boiler and steam is generated, thereby realizing the recovery and utilization of heat.

[0034] Specifically, the steam pressure is 0.7 MPa.

[0035] Preferably, a preheating feeding device 4 is also provided. The preheating feeding device 4 includes a first fluidized bed collector 41 and a second fluidized bed collector 42. The second fluidized bed collector 42 is connected to the outlet of the waste heat boiler 33 and the outlet of the bag filter 32 and is also connected to the first fluidized bed collector 41. The second fluidized bed collector 42 is also provided with a feed inlet. The first fluidized bed collector 41 is connected to the outlet of the cyclone dust collector 31 and is also connected to the feed inlet of the fluidized bed sintering reaction unit 21. Both the first fluidized bed collector 41 and the second fluidized bed collector 42 are provided with fluidizing plates to convert the material into a fluidized state.

[0036] Specifically, the bottom of the second fluidized bed collector 42 is equipped with a fluidizing plate with an opening ratio of 15%-25% and a pore size of 0.5-1mm. The second fluidized bed collector 42 is used to receive two types of materials: one is the recovered powder (temperature 100℃-150℃, accounting for 20%-50% by mass) from the bag filter 32 and the waste heat boiler 33, and the other is the precursor raw material at room temperature (20℃-30℃) (accounting for 30%-70% by mass). Fluidizing gas (nitrogen or air, apparent gas velocity 0.5-5m / s) is introduced through the fluidizing plate to fully mix and exchange heat between the two types of materials in a fluidized state. After mixing, the material temperature rises to 60℃-85℃, completing the initial preheating of the precursor (heating rate ≤5℃ / min), avoiding particle bursting caused by direct contact between room temperature raw material and high temperature environment.

[0037] Specifically, the bottom of the first fluidized bed collector 41 is equipped with a fluidizing plate with an opening ratio of 12%-20% and a pore size of 0.8-1.2mm. The first fluidized bed collector 41 is used to receive two types of materials: one is a mixture from the second fluidized bed collector 42 (temperature 60℃-85℃), and the other is high-temperature recovered powder from the cyclone dust collector 31 (temperature 550℃-850℃, accounting for 10%-20% by mass). By introducing fluidizing gas (nitrogen or air, apparent gas velocity 0.5-5m / s) into the second fluidizing plate, the two types of materials are further mixed and heat exchanged in a fluidized state. After mixing, the material temperature rises to 200℃-400℃ (heating rate 5℃-10℃ / min), realizing deep preheating of the precursor and providing a temperature basis for subsequent high-temperature sintering. Preferably, a return spray gun 5 is also provided at the feed inlet of the fluidized bed sintering reaction unit 21. The vacuum degree of the micro negative pressure area of ​​the return spray gun 5 is -5 to -15 kPa, which is formed by the jet action of compressed gas (nitrogen or air) to ensure stable material conveying and no backflow.

[0038] Preferably, a cooling gas distribution plate is provided at the lower end of the collecting unit 23 to achieve controllable cooling of the material. Specifically, the opening ratio of the cooling gas distribution plate is 8%-12%, and the introduced room temperature gas is nitrogen or air, with a flow rate controlled at 0.05-0.2 m³ / h. 3 / (h・kg of material) ensures a cooling rate of 5-15℃ / min, guaranteeing controlled cooling and preventing material cracking. Preferably, the inner walls of the cavities of the gas heater 1, the fluidized bed sintering furnace 2, and the recovery device 3, as well as the interior of the pipes, are all provided with either an alumina ceramic coating or a silicon carbide ceramic coating. The fluidizing plates of the cooling gas distribution plate, the first fluidizing collector 41, and the second fluidizing collector 42 are made of silicon carbide ceramic or alumina ceramic. Specifically, the alumina lining thickness is 5-10 mm, the ceramic coating thickness is 0.5-2 mm, and the surface roughness Ra≤1.6 μm, to avoid powder adhesion and the introduction of metal impurities.

[0039] The second objective of this invention is to provide a cathode material sintering method using a dynamic density sorting cathode material fluidized bed sintering apparatus according to any one of the above-mentioned methods, comprising the following steps: S1. The precursor raw material is fed into the second fluidized material collector 42. Fluidized gas is introduced into the second fluidized material collector 42 to make the precursor raw material and the powder material recovered by the waste heat boiler and the bag dust collector 32 fluidized mix and heat exchange to form the first mixture material, wherein the heating rate of the first mixture material is <5℃ / min. S2. The first mixture is fed into the first fluidized bed collector 41. Fluidized gas is introduced into the first fluidized bed collector 41 to make the first mixture and the particles recovered by the cyclone dust collector 31 fluidize, mix and exchange heat to form the second mixture. The temperature of the second mixture rises to 200℃-400℃ when it leaves the first fluidized bed collector 41. The heating rate of the second mixture is 5℃-10℃ / min. S3. The sintering gas is heated to 700-950℃ by the gas heater 1, and then buffered by the aggregate unit 23. After passing through the venturi unit 22, it enters the fluidized bed sintering reaction unit 21 and forms a turbulent fluidized bed at the fluidized bed sintering reaction unit 21, wherein the apparent gas velocity of the fluidized bed is 0.5-2.0m / s. S4. The second mixture is sprayed into the fluidized bed sintering furnace 2 through the feed gun and sintered in the fluidized bed circulation. The sintering holding time is 5-15 hours and the particle density increases with the sintering process. S5. After sintering, the particles with the required density are separated by airflow in the Venturi unit 22 and enter the collection unit 23 in sequence through the expansion section 221, the throat section 222 and the contraction section 223. The cooling gas distribution plate in the collection unit 23 is filled with room temperature nitrogen or air to cool the sintered particles to ≤80℃. S6. The substandard particles carried by the top exhaust gas of the fluidized bed sintering reaction unit 21 are sequentially fed into the cyclone dust collector 31, the waste heat boiler 33 and the bag dust collector 32 for recycling. The recycled particles are fed into the first fluidized bed collector 41 or the second fluidized bed collector 42 and sprayed into the fluidized bed sintering furnace 2 through the feed gun for circulating heating. S7. The gas temperature at the outlet of the cyclone dust collector 31 is 700-900℃. It enters the waste heat boiler 33 to cool down to 150-200℃ to recover heat, and then is discharged after being purified by the bag filter 32.

[0040] In the first fluidized bed collector 41 or the second fluidized bed collector 42, the higher temperature recovery material and the lower temperature material are gradually mixed, and the heating rate is the ratio of the time spent in the fluidized bed collector to the heating temperature.

[0041] Implementation Plan 1: Sintering of LFP cathode materials: Equipment parameter settings: Gas heater 1: 150kW power, heats nitrogen to 700℃; Venturi Unit 22: Expansion section 221 cone angle 15°, throat section 222 (discharge pipe) length-to-diameter ratio 6, contraction section 223 cone angle 25°, throat section 222 gas flow velocity 25m / s; Fluidized bed sintering reaction unit 21: apparent gas velocity 0.5-2.0 m / s, holding temperature 700℃, holding time 6h; Two-stage preheating: the second fluidized bed collector 42 heats the precursor feed to 150°C (heating rate 2°C / min), and the first fluidized bed collector 41 heats the powder material from the second fluidized bed collector 42 to 350°C. Return material spray gun 5: slight negative pressure -8kPa, compressed nitrogen pressure 0.4MPa; Cooling gas distribution plate: Nitrogen flow rate 0.1 m³ / s 3 / (h・kg), cooling rate 8℃ / min.

[0042] Operation effect: The LFP precursor (a mixture of FePO4·2H2O and Li2CO3, D50=8μm) was preheated in two stages and then the olivine structure was formed in a fluidized bed sintering furnace 2, resulting in a product tap density of 1.85 g / cm³. 3 (0.9g / cm before sintering) 3 ); After dynamic sorting, qualified products (density ≥ 1.45 g / cm³) 3 ) accounted for 97.8%, with a magnetic foreign matter content of 0.8 ppm; Waste heat recovery generates 90 kg / h of steam, meeting 40% of the heat demand for precursor drying, and reducing energy consumption per ton of product to 220 kWh (compared to 350 kWh for traditional equipment). Battery performance: 1C discharge capacity of 158mAh / g, capacity retention of 94% after 500 cycles, which is better than traditional process products (152mAh / g, 88%).

[0043] Implementation Scheme 2: Sintering of NCM811 cathode material: The following describes the implementation process of the present invention in detail, taking the sintering of NCM811 cathode material as an example: Equipment parameter settings: Gas heater 1: 100kW power, heats nitrogen to 800℃; Venturi Unit 22: Expansion section 221 cone angle 17.5°, throat section 222 (discharge pipe) length-to-diameter ratio 4.5, contraction section 223 cone angle 25°, throat section 222 gas velocity 23.5m / s; Fluidized bed sintering reaction unit 21: inner diameter 1.6m, height 17.5m, fluidization velocity 1.1m / s; Two-stage preheating: the second fluidized bed collector 42 heats the precursor feed to 120°C (heating rate 2°C / min), and the first fluidized bed collector 41 heats the powder material from the second fluidized bed collector 42 to 375°C. Waste heat boiler 33: Steam production capacity 750 kg / h (0.7 MPa saturated steam).

[0044] Operating steps: The precursor (Ni0.8Co0.1Mn0.1(OH)2, moisture 0.3%, D50=5μm) is mixed with Li2CO3 in stoichiometric ratio and then fed into the second fluidized bed collector 42 to be mixed with the fine powder (5%) recovered by the bag filter dust collector 32 and preheated to 300℃. 800℃ air (flow rate 500m³) 3 The material is fed into fluidized bed sintering furnace 2 ( / h) to form a fluidized bed; the preheated material is injected into the bed through a feed lance and held at 800℃ for 7 hours to complete the layered structure sintering, increasing the particle density to 2.75-2.85 g / cm³. 3 ; The qualified particles enter the receiving hopper through the discharge pipe, and room temperature nitrogen gas (flow rate 0.2 m³ / h) is introduced into the cooling gas distribution plate. 3 / h), the material is cooled from 800℃ to 60℃ and discharged through the discharge valve (product qualification rate 96.5%). Substandard particles (density 2.5-2.7 g / cm³) 3 The dust is recovered by cyclone dust collector 31 and bag dust collector 32, with a recovery rate of over 99.5%. It is then sent back to the furnace for further sintering through the first fluidized bed collector 41 and the second fluidized bed collector 42. The exhaust gas recovers heat in waste heat boiler 33, and the by-product steam is used for heating the molten salt preparation tank and system insulation. The exhaust gas is then purified by bag filter 32 before being discharged (dust concentration 8 mg / m³). 3 ).

[0045] In this embodiment, the tap density of the NCM811 product reaches 2.8 g / cm³. 3 The cycle performance (1C, 500 cycles) has a capacity retention rate of 92%, and the overall energy consumption is reduced to 2.8 kW·h / kg, which is 25% lower than that of static sintering.

[0046] The foregoing description illustrates and describes several preferred embodiments of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept by means of the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A fluidized bed sintering apparatus for positive electrode materials with dynamic density sorting, characterized in that: The system includes a gas heater (1) and a fluidized bed sintering furnace (2), which is vertically arranged. The fluidized bed sintering furnace (2) includes a fluidized bed sintering reaction unit (21), a venturi unit (22), and a collection unit (23) arranged from top to bottom. The venturi unit (22) includes an expansion section (221), a throat section (222), and a contraction section (223) arranged from top to bottom. The cross-sectional areas of the expansion section (221) and the contraction section (223) are arranged along the direction away from the gas heater (1) and the venturi unit (223). The throat section (222) gradually expands in direction. The gas heater (1) is provided with an air inlet. The gas heater (1) is connected to the contraction section (223). The upper end of the collecting unit (23) is connected to the contraction section (223). The lower end of the collecting unit (23) is connected to the discharge port. The lower end of the fluidized sintering reaction unit (21) is connected to the expansion section (221) and is provided with a feed inlet. The upper end of the fluidized sintering reaction unit (21) is connected to the recovery device (3).

2. The positive electrode material fluidized bed sintering equipment according to claim 1, characterized in that: The contraction section (223) is a circular arc transition structure. The axial height H and the radius R of the contraction section (223) satisfy: R=H, and the diameter D1 of the inlet end of the contraction section (223) is 3-5 times the diameter d of the throat section (222). The throat segment (222) is cylindrical in shape, and the formula for calculating the diameter d of the throat segment (222) is as follows: Where Q is the sintering gas flow rate (m³ / s). 3 / s), u t For the critical wind speed u t =1.2-1.5×u mf u mf For the critical fluidization velocity, the length L of the throat segment (222) is 1-2 times the throat diameter d, and k is a correction factor. The expansion section (221) is tapered: the diameter of the inlet end of the expansion section (221) is equal to the diameter d of the throat section (222), the diameter D2 of the outlet end of the expansion section (221) is 3.5-5.5 times the diameter d of the throat section (222), and the diffusion angle α is 75-80°.

3. The positive electrode material fluidized bed sintering equipment according to claim 2, characterized in that: The diameter of the fluidized bed sintering reaction unit (21) is 3.5-5.5 times the diameter d of the throat section (222), and the height of the fluidized bed sintering reaction unit (21) is 5-8 times the diameter.

4. The positive electrode material fluidized bed sintering equipment according to claim 1, characterized in that: The recycling device (3) includes a cyclone dust collector (31) and a bag filter (32). The top of the cyclone dust collector (31) is provided with an air inlet connected to the fluidized bed sintering reaction unit (21) and an air outlet connected to the bag filter (32). The bottom of both the cyclone dust collector (31) and the bag filter (32) is provided with a discharge port.

5. The positive electrode material fluidized bed sintering equipment according to claim 4, characterized in that: The recovery device (3) also includes a waste heat boiler (33), which is located between the cyclone dust collector (31) and the bag filter (32) and is connected to the outlet of the cyclone dust collector (31) and the inlet of the bag filter (32) respectively.

6. The positive electrode material fluidized bed sintering equipment according to claim 5, characterized in that: A preheating feed device (4) is also provided. The preheating feed device includes a first fluidized material collector (41) and a second fluidized material collector (42). The second fluidized material collector (42) is connected to the outlet of the waste heat boiler (33) and the outlet of the bag filter (32) and is also connected to the first fluidized material collector (41). The second fluidized material collector (42) is also provided with a feed inlet. The first fluidized material collector (41) is connected to the outlet of the cyclone dust collector (31) and is also connected to the feed inlet of the fluidized sintering reaction unit (21). Both the first fluidized material collector (41) and the second fluidized material collector (42) are provided with fluidizing plates (411) to convert the material into a fluidized state.

7. The positive electrode material fluidized bed sintering equipment according to claim 1, characterized in that: The feed inlet of the fluidized bed sintering reaction unit (21) is also equipped with a return spray gun (5).

8. The positive electrode material fluidized bed sintering equipment according to claim 1, characterized in that: The lower end of the material collection unit (23) is provided with a cooling gas distribution plate to achieve controllable cooling of the material.

9. The positive electrode material fluidized bed sintering equipment according to claim 1, characterized in that: The inner walls of the cavities of the gas heater (1), the fluidized bed sintering furnace (2), and the recycling device (3), as well as the interior of the pipes, are all provided with either an alumina ceramic coating or a silicon carbide ceramic coating.

10. A method for sintering a positive electrode material, characterized in that, The fluidized bed sintering apparatus for positive electrode materials with dynamic density sorting as described in any one of claims 1-9 includes the following steps: S1. The precursor raw material is fed into the second fluidized collector (42). Fluidized gas is introduced into the second fluidized collector (42) to make the precursor raw material and the powder material recovered by the waste heat boiler (33) and the bag filter (32) fluidized and mixed to exchange heat to form the first mixture material, wherein the heating rate of the first mixture material is <5℃ / min. S2. The first mixture is fed into the first fluidized collector (41). Fluidized gas is introduced into the first fluidized collector (41) to make the first mixture and the particles recovered by the cyclone dust collector (31) fluidized and mixed to exchange heat to form the second mixture. The temperature of the second mixture rises to 200℃-400℃ when it leaves the first fluidized collector (41). The heating rate of the second mixture is 5℃-10℃ / min. S3. The sintering gas is heated to 700-950℃ by the gas heater (1), and after being buffered by the aggregate unit (23), it enters the fluidized sintering reaction unit (21) through the Venturi unit (22) and forms a turbulent fluidized bed at the fluidized sintering reaction unit (21), wherein the apparent gas velocity of the fluidized bed is 0.5-2.0m / s; S4. The second mixture is sprayed into the fluidized bed sintering furnace (2) through the feed gun and sintered in the fluidized bed circulation. The sintering holding time is 5-15h and the particle density increases with the sintering process. S5. After sintering, the particles with the required density are separated by the airflow in the Venturi unit (22) and enter the collection unit (23) in sequence through the expansion section (221), throat section (222) and contraction section (223). The cooling gas distribution plate (231) in the collection unit (23) introduces room temperature nitrogen or air to cool the sintered particles to ≤80℃. S6. The substandard particles carried by the top exhaust gas of the fluidized bed sintering reaction unit (21) are sequentially fed into the cyclone dust collector (31), the waste heat boiler (33) and the bag dust collector (32) for recycling. The recycled particles are fed into the first fluidized bed collector (41) or the second fluidized bed collector (42) and sprayed into the fluidized bed sintering furnace (2) through the feed gun for circulating heating. S7. The gas temperature at the outlet of the cyclone dust collector (31) is 700-900℃. It enters the waste heat boiler (33) to cool down to 150-200℃ to recover heat. Then it is purified by the bag filter (32) before being discharged.

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