Equipment and process method for continuously producing lithium iron phosphate

Abstract

The invention discloses equipment and a process method for continuously producing lithium iron phosphate, the equipment comprises a feeding device, a riding wheel mechanism, a driving mechanism, a kiln cylinder and a discharging device, the kiln cylinder is provided with a heating section and a cooling section, and a hot air distribution ring and a cold air distribution ring are respectively arranged in a transition area between the heating section and the cooling section at intervals; the hot air distribution ring is communicated with hot air at the tail end of the kiln barrel, the cold air distribution ring is communicated with cold air at the head end of the kiln barrel, and the hot air distribution ring and the cold air distribution ring blow air in opposite directions respectively, so that a local under-pressure zone is formed in the transition area, direct mixing of hot air and cold air is blocked, and thermal crosstalk is reduced. Temperature field distribution in the rotary kiln is optimized, the cooling capacity is improved, system energy consumption is reduced, the overall heat utilization efficiency is improved, meanwhile, multi-point monitoring is carried out, visual deformation is displayed through the three-dimensional reproduction technology, a deformation threshold value is set for early warning, and real-time, non-contact and intelligent monitoring of the states of key components is achieved.

Description

Technical Field

[0001] This invention relates to a lithium iron phosphate production technology, and in particular to an equipment and process for continuous production of lithium iron phosphate. Background Technology

[0002] Lithium iron phosphate (LFP) is an electrode material for lithium-ion battery systems, primarily used in various lithium-ion battery systems. It boasts high specific capacity, good thermal stability, superior safety performance, and excellent cycle performance, making it considered an ideal electrode material for lithium-ion battery systems. The production process of LFP involves feeding, premixing, grinding, spray drying, kiln, air jet milling, batch mixing, sieving, and packaging. During LFP production, the kiln section requires sintering at high temperatures, with the kiln interior operating under high temperature and pressure.

[0003] The existing kilns used for lithium iron phosphate production have the following shortcomings: 1. Problems of uneven temperature field and low thermal efficiency in high-temperature kilns: Traditional rotary kilns have strong thermal crosstalk between the heating and cooling sections. The cooling section easily absorbs heat from the heating section, resulting in low cooling efficiency and increased energy consumption.

[0004] 2. Problem of poor reliability of dynamic sealing at high temperatures: Lithium iron phosphate requires an inert atmosphere to be maintained at nearly 1000°C during calcination. Existing sealing technologies (such as labyrinth, flake, and graphite seals) are difficult to achieve long-term "zero leakage" under high-temperature rotation conditions. Air intrusion will lead to Fe²⁺ oxidation, which will seriously affect product performance.

[0005] 3. Lack of equipment health monitoring during long-term operation: When ultra-long kilns operate at high temperatures, uneven wear of the support roller system is likely to occur, and the kiln material may undergo creep deformation. Current technology lacks online, real-time, and non-contact monitoring methods for these critical components, resulting in delayed fault detection, safety hazards, and high maintenance costs. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the shortcomings of existing calibration technology and provide a reasonable, energy-efficient, well-sealed, and accurately monitored continuous production equipment and process for lithium iron phosphate.

[0007] The technical solution of this invention is: A continuous lithium iron phosphate production apparatus includes a feeding device, a roller support mechanism, a drive mechanism, a kiln, and a discharging device. The kiln has a heating section and a cooling section. A hot gas distribution ring and a cold gas distribution ring are respectively arranged at intervals in the transition area between the heating section and the cooling section. The hot gas distribution ring is connected to the hot gas at the tail end of the kiln, and the cold gas distribution ring is connected to the cold gas at the head end of the kiln. The hot gas distribution ring and the cold gas distribution ring blow air in opposite directions, so that the transition area forms a local undervoltage zone, which prevents the direct mixing of hot gas and cold gas and reduces thermal crosstalk.

[0008] Furthermore, the hot gas distribution ring is evenly distributed with injection heads along its circumference, and the injection heads are inclined and all face the kiln tail axis.

[0009] Furthermore, the cold air distribution ring is evenly distributed with injection heads along its circumference, and the injection heads are inclined and all face the kiln head axis.

[0010] Furthermore: a heating mechanism is provided around the heating section. The heating mechanism includes a heating cover and a heater. The heating cover can cover the kiln cylinder. The heater is located inside the heating cover. Radial monitoring mechanisms are provided at intervals on the heating cover. The radial monitoring mechanism includes a radial laser rangefinder and a controller. The data information monitored by the radial laser rangefinder is transmitted to the control center or personal information terminal through the controller.

[0011] Furthermore, a cooling mechanism is provided around the cooling section. The cooling mechanism includes a cooling cover and a cooling water pipe. The cooling cover can cover the kiln cylinder, and the cooling water pipe is located inside the cooling cover.

[0012] Furthermore, heat dissipation nails are spaced apart on the kiln cylinder, the heat dissipation nails penetrate the kiln cylinder and their inner ends are rigidly connected to the internal lifting plates, and the outer ends of the heat dissipation nails are arranged alternately with the cooling water pipes to increase the heat exchange area.

[0013] Furthermore, the roller support mechanism includes a tire, a support roller, and a support roller frame. A roller laser rangefinder is installed on the support roller frame to monitor the wear of the support roller at any time.

[0014] Furthermore: the first end of the kiln cylinder is connected to the discharge pipe section through a corrugated pipe, the discharge pipe section is rotatably connected to the support frame of the discharge device through a slewing bearing, a wear-resistant ring is fitted on the discharge pipe section, a water-cooling cavity is fitted on the wear-resistant ring, two lip-shaped sealing rings are spaced apart between the discharge pipe section and the wear-resistant ring, and a lubricating oil cavity is located between the two lip-shaped sealing rings.

[0015] A method for continuously producing lithium iron phosphate using the aforementioned equipment includes the following steps: a. Start the drive mechanism to make the kiln cylinder rotate, and at the same time start the heating mechanism and the cooling mechanism to make the kiln cylinder form a heating section and a cooling section; b. The material enters the kiln through the feeding device. Under the action of the internal spiral blades, the material moves from the tail end to the head end of the kiln. During the movement, the material is turned up by the internal lifting plates, which can fully heat or cool it. Nitrogen enters the kiln from the inlet and outlet and maintains a slight positive pressure to ensure an inert atmosphere. c. The hot air distribution ring and the cold air distribution ring blow air in opposite directions, so that the transition area forms a local underpressure zone, which blocks the direct mixing of hot air and cold air and reduces thermal crosstalk. d. The material undergoes high-temperature sintering and low-temperature cooling, and is finally discharged by the discharge device. e. Use a laser rangefinder to monitor the axial wear of the support rollers across the entire range, and use an infrared rangefinder to detect the deformation of the high-temperature kiln body in real time. Display the deformation intuitively through three-dimensional reproduction technology, set a deformation threshold for early warning, and realize real-time, non-contact, and intelligent monitoring of the status of key components.

[0016] Furthermore, an air supply device is provided at the discharge device, the air supply device including a fan, which can supply gas into the kiln.

[0017] The beneficial effects of this invention are: 1. The present invention uses a reverse blowing / drawing hot and cold air ring to form an airflow isolation zone in the cold and hot transition zone, which effectively suppresses thermal crosstalk and improves cooling efficiency and energy utilization.

[0018] 2. This invention constructs a zero-leakage sealing system with multiple safeguards: It adopts a composite structure of "multi-lip seal + reverse lip seal + grease sealing cavity" and integrates water cooling and air pressure linkage compensation mechanism. It ensures the long-term reliability of high-temperature dynamic sealing from three dimensions: physical isolation, temperature control and dynamic pressure regulation, and achieves true "zero leakage".

[0019] 3. This invention utilizes multi-point monitoring to achieve real-time, accurate, and non-contact monitoring of roller wear and kiln body creep. It can provide early warning of potential faults, avoid major safety accidents caused by roller damage or kiln body breakage, extend equipment service life, reduce maintenance costs, and improve production continuity.

[0020] 4. The present invention provides heat-conducting nails that penetrate the thickness of the kiln wall in the cooling section and are rigidly connected to the internal lifting plates, which greatly enhances the heat conduction efficiency from the material side to the cooling water side (outside the kiln).

[0021] 5. This invention optimizes the temperature field distribution inside the kiln, improves cooling capacity, reduces system energy consumption, enhances overall heat utilization efficiency, is easy to promote and implement, and has good economic benefits. Attached Figure Description

[0022] Figure 1 This is a structural diagram of an equipment for the continuous production of lithium iron phosphate. Figure 2 for Figure 1 Enlarged view of the intermediate cooling section; Figure 3 for Figure 1 Enlarged view of the intermediate heating section; Figure 4 for Figure 3 Side view of the heating section shown; Figure 5 for Figure 1 Enlarged view of the center support roller mechanism; Figure 6 for Figure 5 Side view of the roller mechanism shown; Figure 7 for Figure 1 Diagram of the sealing structure of the kiln body and the discharge mechanism; Figure 8 for Figure 1 Structural diagram of the central gas ring. Detailed Implementation

[0023] Example 1: See Figure 1 -- Figure 8 In the diagram, 1-feeding device, 2-roller support mechanism, 3-kiln cylinder, 4-heating mechanism, 5-radial monitoring mechanism, 6-hot gas distribution ring, 7-cold gas distribution ring, 8-cooling mechanism, 9-cooling water pipe, 10-heat dissipation nail, 11-discharge device, 12-air supply device, 13-slewing bearing, 14-wear-resistant ring, 15-water-cooled cavity, 16-lubricating oil cavity, 17-lip seal ring, 18-bellows, 19-discharge pipe section, 21-tire, 22-support roller, 23-support wheel frame, 24-roller laser rangefinder, 51-radial laser rangefinder, 61-annular cavity, 62-rotary joint, 63-connecting pipe, 64-nozzle, 65-air inlet pipe.

[0024] A continuous lithium iron phosphate production device includes a feeding device 1, a roller support mechanism 2, a drive mechanism, a kiln 3, and a discharging device 11. The kiln 3 is provided with a heating section and a cooling section. A hot gas distribution ring 6 and a cold gas distribution ring 7 are respectively arranged at intervals in the transition area between the heating section and the cooling section. The hot gas distribution ring 7 is connected to the hot gas at the tail end of the kiln, and the cold gas distribution ring 7 is connected to the cold gas at the head end of the kiln. The hot gas distribution ring 6 and the cold gas distribution ring 7 blow air in opposite directions, so that a local underpressure zone is formed in the transition area, which prevents the direct mixing of hot gas and cold gas, reduces thermal crosstalk, and improves the overall thermal utilization efficiency.

[0025] Preferred configuration: Injector heads are evenly distributed along the circumference of the hot gas distribution ring 6, with the nozzles angled and facing the kiln tail axis. Injector heads are also evenly distributed along the circumference of the cold gas distribution ring 7, with the nozzles angled and facing the kiln head axis.

[0026] Figure 8 The diagram shows the structure of the gas distribution ring. Its main structural features are an air inlet pipe 65 and an annular cavity 61. The annular cavity 61 is evenly distributed with nozzles 64. The air inlet pipe 65 is fixed inside the kiln 3 by a cross. One end of the air inlet pipe 65 is connected to one end of a connecting pipe 63 through a rotary joint 62. The other end of the connecting pipe 63 is connected to the inner cavity of the annular cavity 61. The other end of the air inlet pipe 65 is connected to the gas at the beginning or end of the kiln 3. Under the action of the fan, the air inlet pipe 65 inputs gas into the annular cavity 61 and sprays it out through the nozzles 64.

[0027] Preferred solution: A heating mechanism 4 is provided around the heating section. The heating mechanism 4 includes a heating cover and a heater. The heating cover can cover the kiln cylinder 3. The heater is located inside the heating cover (not shown in the figure, this is prior art and will not be described in detail). Radial monitoring mechanisms 5 are provided at intervals on the heating cover. The radial monitoring mechanism 5 includes a radial laser rangefinder 51 and a controller. The data information monitored by the radial laser rangefinder is transmitted to the control center or personal information terminal through the controller.

[0028] Specifically: Above the middle of the heating section of the kiln, a set of radial laser rangefinders 51 are installed at equal intervals along the axial direction (the exact number depends on the length of the heating section; it could be 3, 5, or other types, etc.). These rangefinders, in conjunction with a rotary encoder, periodically scan the rotating kiln body to acquire radial distance data, i.e., the radial deformation of the kiln body. The kiln body outline is generated using 3D point cloud reconstruction technology, and its radial deformation trend is analyzed in real time, enabling early warning of creep and providing data support for predictive maintenance.

[0029] Preferred solution: A cooling mechanism 8 is provided on the periphery of the cooling section. The cooling mechanism 8 includes a cooling cover and cooling water pipes 9. The cooling cover can cover the kiln cylinder 3, and the cooling water pipes 9 are located in the cooling cover and are spaced apart.

[0030] Heat dissipation nails 10 are spaced apart on the kiln cylinder 3. The heat dissipation nails 10 penetrate the kiln cylinder 3 and are rigidly connected to the internal lifting plate at their inner ends. The outer ends of the heat dissipation nails 10 are arranged alternately with the cooling water pipes 9 to increase the heat exchange area.

[0031] Preferred solution: The roller support mechanism 2 includes a tire 21, a support roller 22 and a support roller frame 23. A roller support laser rangefinder 24 is installed on the support roller frame 23 to monitor the wear of the support roller 22 at any time.

[0032] Specifically, 4-6 laser rangefinders 24 are evenly spaced along the axial direction of each roller, working in conjunction with a rotary encoder to measure the diameter change of the roller surface at different axial positions in real time, accurately detecting the wear at each point. When the wear at any point exceeds a threshold (e.g., 0.5mm), the system automatically alarms and performs maintenance to correct the wear.

[0033] Preferred solution: The first end of the kiln cylinder 3 is connected to the discharge pipe section 19 through the corrugated pipe 18. The discharge pipe section 19 is rotatably connected to the support frame of the discharge device 11 through the slewing bearing 13. A wear-resistant ring 14 is fitted on the discharge pipe section 19, and a water-cooling cavity 15 is fitted on the wear-resistant ring 14. Two lip seals 17 are spaced apart between the discharge pipe section 19 and the wear-resistant ring 14, and a lubricating oil cavity 16 is located between the two lip seals 17.

[0034] Specifically: a multi-lip seal structure is used near the kiln body end; a reverse lip seal structure is set at the end away from the kiln body, and grease is added between them, forming a closed lubricating oil cavity 16. By periodically adding grease from the oil cup, external air can be completely isolated; at the same time, a branch line is introduced to lubricate the rotary bearing 13. All lip seals are integrated with a water-cooling cavity 15, which circulates cooling water to reduce the sealing operating temperature and prevent high-temperature aging. The bellows 18 absorbs kiln vibration and ensures sealing reliability. The internal air pressure monitoring system monitors the sealing cavity pressure in real time. Once it falls below the set value (e.g., 0.1MPa), the nitrogen inlet pressure is adjusted to dynamically maintain a slight positive pressure, ensuring that external air cannot enter the kiln body and achieving an oxygen-free reaction environment, i.e., "zero leakage".

[0035] A method for continuous production of lithium iron phosphate includes the following steps: a. Start the drive mechanism to make the kiln cylinder 3 rotate, and at the same time start the heating mechanism 4 and the cooling mechanism 8 to make the kiln cylinder 3 form a heating section and a cooling section; b. The material enters the kiln cylinder 3 through the feeding device 1. Under the action of the internal spiral blades, the material moves from the tail end to the head end of the kiln cylinder. During the movement, the material is turned up by the internal lifting plates, which can fully heat or cool it. Nitrogen enters the kiln cylinder from the inlet and outlet and maintains a slight positive pressure to ensure an inert atmosphere. c. The hot air distribution ring 6 and the cold air distribution ring 7 blow air in opposite directions, creating a local underpressure zone in the transition area, which blocks the direct mixing of hot air and cold air and reduces thermal crosstalk. d. The material undergoes high-temperature sintering and low-temperature cooling, and is finally discharged by the discharge device 11; e. The laser rangefinder 24 is used to monitor the axial wear of the support roller 22 in its entire range. At the same time, the infrared rangefinder 51 is used to detect the deformation of the high-temperature kiln body in real time. The deformation is displayed intuitively through three-dimensional reproduction technology, and a deformation threshold is set for early warning, so as to realize real-time, non-contact and intelligent monitoring of the status of key components.

[0036] Preferred solution: An air supply device 12 is installed at the discharge device 11. The air supply device 12 includes a fan and can supply gas into the kiln 3.

[0037] This project's composite sealing structure, combining water cooling and pneumatic pressure linkage, completely solves the leakage problem of high-temperature dynamic sealing. It ensures an oxygen-free environment inside the kiln, effectively preventing Fe²⁺ oxidation and significantly improving the quality and batch-to-batch consistency of lithium iron phosphate products.

[0038] Example 2: This example is basically the same as Example 1, and the similarities will not be repeated. The difference is that the structure of the air distribution ring is different. In this example, the air inlet pipe of the air distribution ring is located outside the kiln cylinder, and one end of the air inlet pipe is connected to the annular cavity, and the other end of the air inlet pipe is connected to the first or last end of the kiln cylinder. A fan is installed on the air inlet pipe.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications made based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A continuous production apparatus for lithium iron phosphate, comprising a feeding device, a roller support mechanism, a drive mechanism, a kiln, and a discharging device, characterized in that: The kiln is provided with a heating section and a cooling section. The transition area between the heating section and the cooling section is provided with a hot gas distribution ring and a cold gas distribution ring at intervals. The hot gas distribution ring is connected to the hot gas at the tail end of the kiln, and the cold gas distribution ring is connected to the cold gas at the head end of the kiln. The hot gas distribution ring and the cold gas distribution ring blow air in opposite directions, so that the transition area forms a local underpressure zone, which prevents the direct mixing of hot gas and cold gas and reduces thermal crosstalk.

2. The equipment for continuous production of lithium iron phosphate according to claim 1, characterized in that: The hot gas distribution ring is evenly distributed with injection heads along its circumference. The injection heads are inclined and all face the kiln tail axis.

3. The equipment for continuous production of lithium iron phosphate according to claim 1, characterized in that: The cold air distribution ring is evenly distributed with spray heads along its circumference. The spray heads are inclined and all face the kiln head axis.

4. The equipment for continuous production of lithium iron phosphate according to claim 1, characterized in that: A heating mechanism is provided around the heating section. The heating mechanism includes a heating cover and a heater. The heating cover can cover the kiln cylinder. The heater is located inside the heating cover. Radial monitoring mechanisms are arranged at intervals on the heating cover. The radial monitoring mechanism includes a radial laser rangefinder and a controller. The data information monitored by the radial laser rangefinder is transmitted to the control center or personal information terminal through the controller.

5. The equipment for continuous production of lithium iron phosphate according to claim 1, characterized in that: A cooling mechanism is provided around the cooling section. The cooling mechanism includes a cooling cover and cooling water pipes. The cooling cover can cover the kiln cylinder, and the cooling water pipes are located inside the cooling cover.

6. The equipment for continuous production of lithium iron phosphate according to claim 5, characterized in that: The kiln cylinder is provided with heat dissipation nails at intervals. The heat dissipation nails penetrate the kiln cylinder and are rigidly connected to the internal lifting plates at their inner ends. The outer ends of the heat dissipation nails are arranged alternately with the cooling water pipes to increase the heat exchange area.

7. The equipment for continuous production of lithium iron phosphate according to claim 1, characterized in that: The roller support mechanism includes a tire, a support roller, and a support roller frame. A roller laser rangefinder is installed on the support roller frame to monitor the wear of the support roller at any time.

8. The equipment for continuous production of lithium iron phosphate according to claim 1, characterized in that: The first end of the kiln cylinder is connected to the discharge pipe section through a corrugated pipe. The discharge pipe section is rotatably connected to the support frame of the discharge device through a slewing bearing. A wear-resistant ring is fitted on the discharge pipe section, and a water-cooling cavity is fitted on the wear-resistant ring. Two lip-shaped sealing rings are spaced apart between the discharge pipe section and the wear-resistant ring, and a lubricating oil cavity is located between the two lip-shaped sealing rings.

9. A method for continuously producing lithium iron phosphate using the apparatus for continuous production of lithium iron phosphate according to any one of claims 1-8, comprising the following steps: a. Start the drive mechanism to make the kiln cylinder rotate, and at the same time start the heating mechanism and the cooling mechanism to make the kiln cylinder form a heating section and a cooling section; b. The material enters the kiln through the feeding device. Under the action of the internal spiral blades, the material moves from the tail end to the head end of the kiln. During the movement, the material is turned up by the internal lifting plates, which can fully heat or cool it. Nitrogen enters the kiln from the inlet and outlet and maintains a slight positive pressure to ensure an inert atmosphere. c. The hot air distribution ring and the cold air distribution ring blow air in opposite directions, so that the transition area forms a local underpressure zone, which blocks the direct mixing of hot air and cold air and reduces thermal crosstalk. d. The material undergoes high-temperature sintering and low-temperature cooling, and is finally discharged by the discharge device. e. Use a laser rangefinder to monitor the axial wear of the support rollers across the entire range, and use an infrared rangefinder to detect the deformation of the high-temperature kiln body in real time. Display the deformation intuitively through three-dimensional reproduction technology, set a deformation threshold for early warning, and realize real-time, non-contact, and intelligent monitoring of the status of key components.

10. The process for continuous production of lithium iron phosphate according to claim 9, characterized in that: An air supply device is provided at the discharge device, and the air supply device includes a fan that can supply gas into the kiln.

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