A closed-circuit circulation airflow pulverizing device for ternary positive electrode materials

Abstract

The utility model discloses a kind of closed circuit circulation airflow pulverizing devices of ternary positive electrode material, belong to electrode material production equipment technical field, including rack and be arranged on the oilless air compressor of rack, cooling dryer, airflow mill host, trapping bin and reflux pipeline, the oilless air compressor, cooling dryer, airflow mill host and trapping bin are sequentially connected by pipeline, the trapping bin is connected with oilless air compressor by reflux pipeline, to constitute closed circuit circulation, the middle part of the reflux pipeline is connected in series with pressure buffer tank, the pressure buffer tank includes airtight tank body, the lower part of the tank body is equipped with the fluid inlet that communicates with reflux pipeline, the upper portion of tank body is equipped with the fluid outlet that communicates with reflux pipeline, and the central axis of fluid inlet and the central axis of fluid outlet are perpendicular to each other;Through the structural coupling of buffer tank structure and integrated pressure detection air supplement device, the problem of closed circuit circulation airflow pulverizing system pressure fluctuation is solved.

Description

Technical Field

[0001] This utility model relates to the technical field of electrode material production equipment, specifically a closed-loop circulating airflow pulverizing device for ternary cathode materials. Background Technology

[0002] Airflow milling technology is a key process for preparing high-purity and ultrafine powder materials. Traditional airflow milling systems are mostly open-circuit designs, meaning that compressed gas is directly discharged into the atmosphere after milling and material conveying. This system has significant drawbacks: First, the compressed gas is used only once, resulting in serious energy waste and high production costs; second, the exhaust gas carries trace amounts of ultrafine powder, causing material loss and dust pollution; third, if an oil-lubricated compressor is used, the exhaust may contain oil, and the system's continuous intake of ambient air introduces moisture and impurities. To avoid oil contamination at the source, high-end production lines generally use oil-free air compressors to meet the high-purity requirements of ternary cathode materials. However, even with oil-free compressors, the open-circuit system's continuous intake of ambient air still introduces moisture and impurities, thus contaminating the extremely purity-sensitive ternary cathode materials.

[0003] To overcome the shortcomings of open-circuit systems, closed-loop recirculating airflow milling systems have emerged. This system connects the collection hopper to the air compressor inlet via a return pipe, forming a closed gas circulation loop. Theoretically, this achieves gas recycling, significantly reducing energy consumption and emissions. However, in-depth research has revealed new technical defects in existing closed-loop systems during actual production: intermittent air replenishment to maintain system pressure, inherent compressor exhaust pulsations, and instantaneous blockage and release of material within the airflow mill all induce high-frequency pressure pulsations and drift within the closed system. This continuous pressure fluctuation directly leads to unstable nozzle flow rate in the airflow mill, causing fluctuations in the milling energy input. Ultimately, this manifests as batch-to-batch variations in the particle size distribution (e.g., D50, Dmax) of ternary cathode materials, failing to meet the stringent requirements for material consistency in high-end lithium batteries.

[0004] Therefore, there is an urgent need for a closed-loop airflow pulverizing device for ternary cathode materials that can effectively suppress pressure fluctuations structurally and provide stable operating conditions for the pulverizing process. Utility Model Content

[0005] The purpose of this invention is to overcome the problem of inconsistent product particle size caused by pressure fluctuations in existing closed-loop circulation systems, and to provide a closed-loop airflow pulverizing device for ternary cathode materials.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows: a closed-loop circulating airflow pulverizing device for ternary cathode materials, comprising a frame and an oil-free air compressor, a cooling dryer, an airflow mill main unit, a collection hopper, and a return pipe mounted on the frame. The oil-free air compressor, cooling dryer, airflow mill main unit, and collection hopper are connected sequentially via pipelines. The collection hopper is connected to the oil-free air compressor via the return pipe, thereby forming a closed loop. A pressure buffer tank is connected in series in the middle of the return pipe. The pressure buffer tank includes a sealed tank body. The lower part of the tank body is provided with a fluid inlet communicating with the return pipe, and the upper part of the tank body is provided with a fluid outlet communicating with the return pipe. The central axis of the fluid inlet and the central axis of the fluid outlet are perpendicular to each other.

[0007] Furthermore, the volume of the pressure buffer tank is 10-30% of the sum of the volumes of the return pipe and all connecting pipes.

[0008] Furthermore, the tank is equipped with a pressure sensor, and the top of the tank is equipped with a gas supply port connected to a gas supply valve. The inlet of the gas supply valve is connected to an inert gas source through a pipeline. The pressure sensor and the gas supply valve are equipped with electrical connection terminals for receiving signals and issuing control commands.

[0009] Furthermore, a gas purification device is also provided on the return pipe before the fluid inlet of the pressure buffer tank.

[0010] Furthermore, the gas purification device is a precision filter.

[0011] Furthermore, the inert gas source is a nitrogen gas source or an argon gas source.

[0012] This utility model provides a closed-loop circulating airflow pulverizing device for ternary cathode materials, which has the following beneficial effects: This invention effectively absorbs and suppresses high-frequency pressure pulsations and slow pressure drifts within the closed-loop circulation by connecting a specific pressure buffer tank with bottom inlet and top outlet and perpendicular inlet and outlet axes in series in the return flow pipeline, and integrating a closed-loop controlled air replenishment system. Combined with an optimized buffer volume ratio, it can significantly stabilize the flow rate and pulverizing energy input of the air jet mill nozzle, thereby improving the consistency of particle size distribution of the ternary cathode material product, while ensuring production purity and system energy efficiency. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the structure of the closed-loop circulating airflow pulverizing device for ternary cathode materials according to this utility model.

[0014] Figure 2 This is a schematic diagram of the pressure buffer tank structure of the closed-loop circulating airflow pulverizing device for ternary cathode materials of this utility model.

[0015] In the diagram, 1 is the frame; 2 is the oil-free air compressor; 3 is the cooling dryer; 4 is the air jet mill main unit; 5 is the collection bin; 6 is the return pipe; 7 is the pressure buffer tank; 8 is the fluid inlet; 9 is the fluid outlet; 10 is the pressure sensor; 11 is the air supply interface; 12 is the inert gas source; and 13 is the gas purification device. Detailed Implementation

[0016] The technical solution of this utility model will be clearly and completely described below with reference to specific embodiments. The described embodiments are merely some, not all, of these embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without inventive effort are within the scope of protection of this utility model.

[0017] like Figure 1 As shown, this utility model provides a closed-loop circulating airflow pulverizing device for ternary cathode materials, including a frame 1 and an oil-free air compressor 2, a cooling dryer 3, an airflow mill main unit 4, a collection hopper 5, and a return pipe 6 mounted on the frame 1. The oil-free air compressor 2, cooling dryer 3, airflow mill main unit 4, and collection hopper 5 are connected sequentially by pipelines. Specifically, the outlet of the oil-free air compressor 2 is connected to the inlet of the cooling dryer 3 via a high-pressure pipeline to remove moisture from the compressed gas and control its temperature. The outlet of the cooling dryer 3 is connected to the inlet of the airflow mill main unit 4 via a pipeline. The outlet of the airflow mill main unit 4 is connected to the inlet of the collection hopper 5 via a feeding pipeline. Qualified powder is drawn into the collection hopper 5, while unqualified material settles back into the airflow mill main unit 4 under centrifugal force. The gas outlet at the top of the collection hopper 5 is connected to the inlet of the oil-free air compressor 2 via the return pipe 6, thus forming a closed-loop circulation system isolated from the external environment. Before the system is started for the first time, the internal air can be replaced with nitrogen through the gas replenishment device, thereby providing an inert gas protective environment for the easily oxidized ternary cathode material.

[0018] A pressure buffer tank 7 is connected in series in the middle of the return pipe 6. The pressure buffer tank 7 includes a sealed tank body. The lower part of the tank body has a fluid inlet 8 communicating with the return pipe 6, and the upper part of the tank body has a fluid outlet 9 communicating with the return pipe 6. The central axis of the fluid inlet 8 and the central axis of the fluid outlet 9 are perpendicular to each other. This embodiment, through its bottom-in, top-out, and vertical flow structure design, forces the airflow from the collection hopper to change its flow direction by 90° after entering at the bottom of the tank body, flowing upward and exiting from the top side. Experimental comparisons have shown that this process can greatly consume the kinetic energy of the airflow, efficiently separate any trace ultrafine powder that may be entrained, and most effectively smooth out high-frequency, large-amplitude pressure pulsations from upstream.

[0019] The pressure buffer tank 7 is equipped with a pressure sensor 10 on its body, and a gas replenishment port 11 is located on the top of the tank, connected to a gas replenishment valve. The inlet of the gas replenishment valve is connected to an inert gas source 12 via a pipeline. The inert gas source 12 is a nitrogen source or an argon source. The pressure sensor 10 and the gas replenishment valve are provided with electrical connection terminals for receiving signals and issuing control commands. These electrical connection terminals are connected to a controller. In this embodiment, the pressure sensor 10, the gas replenishment valve, the inert gas source 12, and the controller together constitute a pressure detection and gas replenishment device.

[0020] Pressure sensor 10 monitors the pressure inside pressure buffer tank 7 in real time, which best represents the average stable pressure of the system. This signal is transmitted to the controller. The controller has a preset target pressure value (e.g., 0.75 MPa) and its allowable fluctuation range (e.g., ±0.02 MPa, approximately ±2.7%). When the system pressure slowly drops to the lower limit due to leakage or other reasons, the controller immediately issues a command to open the gas replenishment valve, replenishing clean nitrogen into the gas phase space at the top of pressure buffer tank 7. Because the gas replenishment point is located in the stable gas chamber of the buffer tank, rather than in a violently disturbed pipeline, the replenished gas can mix smoothly with the gas in the system, avoiding gas replenishment oscillation, thereby achieving accurate and stable recovery of system pressure.

[0021] In this embodiment, the volume of the pressure buffer tank 7 is set to be 10-30% of the sum of the volumes of the return pipe 6 and all connecting pipes. This provides sufficient buffer space for system pressure fluctuations; too small a volume would result in insufficient buffering, while too large a volume would lead to lag in response and increased footprint. It also ensures system compactness and a pressure recovery response speed of 5-6 seconds, achieving a balance between buffering effect and practicality. A gas purification device 13 is also provided on the return pipe 6 before the fluid inlet 8 of the pressure buffer tank 7. This gas purification device 13 is a precision filter (filtration accuracy ≤0.1μm), which can intercept trace amounts of ultrafine powder entrained in the return gas, preventing them from entering the oil-free air compressor 2 or the pressure buffer tank 7, thus protecting the equipment and preventing secondary contamination of materials.

[0022] To verify that this invention can effectively suppress pressure fluctuations, provide stable operating conditions for the pulverizing process, and quantify the bottom-in, top-out, vertically oriented buffer tank structure and its synergistic effect with integrated control, the applicant designed and conducted three sets of comparative experiments. All experiments were based on the same batch of ternary cathode material NCM811 precursor (initial particle size D50 = 15 μm), with the system target pressure set at 0.75 MPa, an oil-free air compressor, a cooling dryer outlet temperature controlled at 25°C, and an air jet mill main unit power of 55 kW. Each experiment was independently repeated three times, and the average value was taken.

[0023] 1. Experiment on the influence of specific structures of pressure buffer tanks on pressure stabilization effect A control group, a comparison group 1, and an experimental group were set up for comparison.

[0024] The control group used an existing closed-loop circulation system, and no pressure buffer tank was installed on the reflux pipe.

[0025] Comparison Group 1 uses an existing closed-loop circulation system with a buffer tank connected in series in the return pipeline. The structure is top-inlet and bottom-outlet, with the central axis of the fluid inlet and outlet parallel.

[0026] The experimental group adopted the design scheme of this utility model, with a buffer tank connected in series in the reflux pipeline, and the buffer tank has a bottom inlet and top outlet structure, with the central axes of the fluid inlet and outlet perpendicular to each other.

[0027] Three systems were run continuously for 2 hours under the same operating conditions, with system pressure monitored and samples taken for analysis. The experimental results showed that the pressure fluctuation range of the control group was 0.08±0.01 MPa, and the D50 coefficient of variation was 3.8±0.3%; the pressure fluctuation range of control group 1 decreased to 0.05±0.01 MPa, and the D50 coefficient of variation was 2.5±0.2%; while the pressure fluctuation range of the experimental group was only 0.02±0.005 MPa, and the D50 coefficient of variation was as low as 1.1±0.1%. The above experimental data were obtained by averaging three tests for each group.

[0028] Therefore, it is evident that the specific buffer tank structure of this invention is most effective in suppressing pressure pulsations and improving product particle size consistency. Its pressure fluctuation amplitude is only 25% of the control group, and its product consistency (D50CV) is more than 56% better than control group 1 (parallel axis structure). This strongly demonstrates the non-obvious technical advantages of the perpendicular inlet and outlet axes in generating turbulence and efficiently dissipating kinetic energy.

[0029] 2. Experiment on the Influence of Pressure Buffer Tank Volume Ratio on Buffering Effect and System Practicality To verify the rationality of the buffer tank volume ratio, the overall performance of the device under different volume ratios was tested.

[0030] The buffer tank volume of control group 2 was 5% (less than 10%) of the total volume of the backflow pipe and all connecting pipes. The buffer tank volume of experimental group 1 was 15% (in the range of 10-30%).

[0031] The buffer tank volume ratio of Experimental Group 2 was 25% (in the range of 10-30%).

[0032] The buffer tank volume ratio of control group 3 is 35% (greater than 30%).

[0033] The comparative experiments showed that, due to insufficient buffer volume, control group 2 experienced pressure fluctuations of 0.04±0.008 MPa and a system response time of 8±1 s, with only a 5% increase in device footprint. Experimental group 1 experienced pressure fluctuations of 0.02±0.005 MPa and a system response time of 5±1 s, with a 12% increase in device footprint. Experimental group 2 experienced pressure fluctuations of 0.018±0.005 MPa and a system response time of 6±1 s, with a 20% increase in device footprint. Although the pressure fluctuation of control group 3 decreased to 0.017±0.005 MPa, the system response time increased to 12±2 s, resulting in a 35% increase in device footprint.

[0034] In summary, when the volume ratio is between 10% and 30%, the system can achieve excellent pressure buffering while maintaining rapid dynamic response. A ratio below 10% results in insufficient buffering, while a ratio above 30% leads to a significantly slower response and uneconomical equipment size, demonstrating the necessity and ingenuity of this volume ratio limitation.

[0035] 3. Experiment on the effect of gas replenishment method on pressure stability and particle size uniformity This study verifies the synergistic advantages of integrating pressure detection and air replenishment devices onto an optimized buffer tank (such as this invention) compared to implementing air replenishment on a conventional buffer tank or pipeline. A control group and an experimental group were set up for comparison. The control group used a conventional buffer tank with top inlet and bottom outlet and parallel axes. The air replenishment valve and pressure sensor were installed on this tank and connected to a controller to achieve closed-loop control. The experimental group used the air replenishment scheme of this invention, which replenishes air through the top of the buffer tank, and works in conjunction with the pressure sensor, controller, and air replenishment valve to form a closed-loop control.

[0036] Simulated pressure shocks were applied during stable system operation, and the pressure overshoot and system recovery time during the gas replenishment process were recorded. The experimental comparison showed that the control group had a gas replenishment pressure overshoot of 0.025±0.006MPa and a pressure recovery time of 9±2s during the gas replenishment process; while the experimental group had a gas replenishment pressure overshoot of 0.010±0.002MPa and a pressure recovery time shortened to 4±1s.

[0037] Tests have shown that, under the same control strategy, integrating the pressure detection and air replenishment device into the optimized buffer tank of this invention results in a significantly better synergistic pressure stabilization effect than integrating it into a conventional buffer tank or pipeline.

[0038] In summary, this invention effectively solves the problem of pressure fluctuation in closed-loop airflow pulverization systems by structurally coupling a specific pressure buffer tank structure with a bottom-inlet, top-outlet, and vertically aligned axis with an integrated pressure detection and gas replenishment device. This significantly improves the consistency of particle size distribution in ternary cathode materials while ensuring material purity and system usability.

[0039] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention.

[0040] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A closed-loop circulating airflow pulverizing device for ternary cathode materials, comprising a frame (1) and an oil-free air compressor (2), a cooling dryer (3), an airflow mill main unit (4), a collection bin (5), and a return pipe (6) mounted on the frame (1), wherein the oil-free air compressor (2), the cooling dryer (3), the airflow mill main unit (4), and the collection bin (5) are connected sequentially by pipelines, and the collection bin (5) is connected to the oil-free air compressor (2) through the return pipe (6), thereby forming a closed loop, characterized in that: A pressure buffer tank (7) is connected in series in the middle of the return pipe (6). The pressure buffer tank (7) includes a sealed tank body. The lower part of the tank body is provided with a fluid inlet (8) that communicates with the return pipe (6), and the upper part of the tank body is provided with a fluid outlet (9) that communicates with the return pipe (6). The central axis of the fluid inlet (8) and the central axis of the fluid outlet (9) are perpendicular to each other.

2. The closed-loop circulating airflow pulverizing device for ternary cathode materials according to claim 1, characterized in that: The volume of the pressure buffer tank (7) is 10-30% of the sum of the volumes of the return pipe (6) and all connecting pipes.

3. The closed-loop circulating airflow pulverizing device for ternary cathode materials according to claim 1, characterized in that: The tank is equipped with a pressure sensor (10), and the top of the tank is equipped with a gas supply port (11) and a gas supply valve. The inlet of the gas supply valve is connected to an inert gas source (12) through a pipeline. The pressure sensor (10) and the gas supply valve are equipped with electrical connection terminals for receiving signals and issuing control commands.

4. The closed-loop circulating airflow pulverizing device for ternary cathode materials according to claim 1, characterized in that: A gas purification device (13) is also provided on the return pipe (6) before the fluid inlet (8) of the pressure buffer tank (7).

5. The closed-loop circulating airflow pulverizing device for ternary cathode materials according to claim 4, characterized in that: The gas purification device (13) is a precision filter.

6. The closed-loop circulating airflow pulverizing device for ternary cathode materials according to claim 3, characterized in that: The inert gas source (12) is a nitrogen gas source or an argon gas source.

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