Vacuum reaction furnace for lithium hexafluorophosphate production

Abstract

The application belongs to the field of lithium hexafluorophosphate production, in particular to a vacuum reaction furnace for lithium hexafluorophosphate production, which comprises a horizontal vacuum furnace, the inside of the horizontal vacuum furnace is provided with a rotatable inner stirring frame, the inner stirring frame is attached to the inner wall of the horizontal vacuum furnace, and a feeding door for feeding and discharging is installed on the top of the horizontal vacuum furnace. Through such a setting, an integrated preparation process of lithium hexafluorophosphate synthesis and purification reaction is realized, air and moisture pollution caused by raw material transfer during the synthesis and purification reaction process is eliminated, the post-processing process is increased, the quality is reduced, and other problems are solved. At the same time, the switchable negative pressure absorption system makes the treatment of the purification and synthesis stages adapt smoothly, realizes the possibility of common operation, reduces the transfer, post-processing and other process steps, and improves the production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of lithium hexafluorophosphate production, specifically a vacuum reactor for lithium hexafluorophosphate production. Background Technology

[0002] Lithium hexafluorophosphate is the core material of lithium battery electrolyte, accounting for more than 40% of the electrolyte cost. Its mainstream production processes are the hydrogen fluoride solvent method and the gas-solid reaction method. The hydrogen fluoride solvent method uses a large amount of hydrogen fluoride solvent, which is more corrosive and requires low-temperature reaction, resulting in high energy consumption. The gas-solid reaction method eliminates the solvent, making it simpler, but it has high equipment requirements.

[0003] The gas-solid reaction method involves adding lithium fluoride powder to a vacuum reactor, evacuating and displacing it to remove moisture, heating it, and then introducing phosphorus pentafluoride gas to react and produce crude lithium hexafluorophosphate. Subsequently, the temperature is raised and a high vacuum is drawn to remove impurities such as hydrogen fluoride and moisture, resulting in a battery-grade product with a purity of 99.9%. The entire process is strictly anhydrous and oxygen-free, with key indicators: hydrogen fluoride <50ppm and moisture <20ppm. The product decomposes upon contact with water and must be sealed and packaged in a dry environment.

[0004] In the traditional lithium hexafluorophosphate production process, the synthesis and purification stages require different equipment. This is because the synthesis stage requires a vigorous stirring mechanism to break up the powder, while the purification stage only requires slight agitation of the crystals without damaging them. At the same time, the waste gas generated in the synthesis stage contains a large amount of phosphorus pentafluoride and hydrogen fluoride. Even when phosphorus pentafluoride comes into contact with trace amounts of water, it will form hydrofluoric acid, which is highly corrosive. Therefore, it is necessary to completely isolate moisture. However, due to the large content of phosphorus pentafluoride and hydrofluoric acid in the synthesis stage, it is impossible to remove them by adsorption and filtration methods. They can only be discharged into specialized treatment equipment. On the other hand, the purification stage requires continuous vacuuming, making it difficult to treat the two gases in a unified manner.

[0005] Therefore, the present invention provides a vacuum reactor for the production of lithium hexafluorophosphate. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0007] The technical solution adopted by the present invention to solve its technical problem is as follows: The present invention provides a vacuum reactor for the production of lithium hexafluorophosphate, including a horizontal vacuum furnace. The interior of the horizontal vacuum furnace is provided with a rotatable internal stirring rack, which is attached to the inner wall of the horizontal vacuum furnace. The top of the horizontal vacuum furnace is equipped with a feeding door for feeding and discharging materials. The top of the horizontal vacuum furnace is also equipped with a connecting valve for releasing gas. The horizontal vacuum furnace is equipped with a negative pressure pipe one and a negative pressure pipe two for vacuuming. This setup enables an integrated preparation process for lithium hexafluorophosphate synthesis and purification, eliminating air and moisture pollution caused by raw material transfer during synthesis and purification, thus preventing increased post-processing and reduced quality. A single negative pressure pipe is used to handle large quantities of air, water vapor, phosphorus pentafluoride, and hydrogen fluoride. Corrosion-resistant pipes are used for this single negative pressure pipe, which is connected to an external recovery buffer tank to temporarily store gases containing large amounts of phosphorus pentafluoride and hydrogen fluoride, and then recover them using dedicated equipment. In the purification stage, a second negative pressure pipe is used, connected to an external cold trap and adsorption core device. Since continuous negative pressure adsorption is required during purification, such a large volume of air cannot be stored in storage devices. After adsorption by the cold trap and adsorption core, the hydrogen fluoride and phosphorus pentafluoride in the purified gas are largely absorbed, and subsequent air only needs to be directly connected to an alkaline scrubbing tower to meet emission standards. This switchable negative pressure absorption system allows for seamless adaptation between purification and synthesis stages, enabling collaborative operation and reducing transfer and post-processing steps, thereby improving production efficiency.

[0008] Preferably, the inner stirring rack includes a connecting side plate and a transmission side plate, which are fixedly connected by multiple wall-mounted brackets. Multiple scrapers that adhere to the inner wall of the horizontal vacuum furnace are connected to the outer side of each wall-mounted bracket. Multiple spray holes are provided on the outer side of the inner stirring rack. This structural design allows the inner stirring rack to effectively disperse the raw material powder using the wall-mounted brackets during rotation, ensuring thorough mixing of the powder and gas phase and guaranteeing a smooth synthesis process. Simultaneously, at slow speeds, it allows the crystal to flip, enabling the crystal to slowly release internal impurities under high temperature and negative pressure. The scrapers can be made of an elastic material and must be corrosion-resistant. The elastic scrapers adhere to the horizontal vacuum furnace wall. The vacuum furnace can scrape off residues adhering to the inner wall of the furnace, including phosphorus pentafluoride and hydrogen fluoride. The nozzles can spray gas along the moving direction of the inner stirring rack. The gas flow can be nitrogen, which, like the replacement gas, can further clean the deposits on the furnace wall. Combined with the nitrogen replacement process, it allows for better transfer of the gas phase and small particles. During the scraping stage, negative pressure tubes are still used for absorption, absorbing the small particles and powder generated during scraping. This ensures that only clean crude crystals remain in the furnace during the purification process, further reducing the content of residues in the purification stage, reducing the workload of the cold trap and adsorption core, and ensuring the smooth preparation of the purified product.

[0009] Preferably, a connecting pipe is fixedly connected to one end of the connecting side plate, and a connector that rotates and engages with the connecting pipe is provided on the outside of the horizontal vacuum furnace. A gas supply box is installed at the bottom of the connector, and a drive box connected to the transmission side plate is installed at the other end of the horizontal vacuum furnace. Through the connection of the connecting pipe and the connector, the inner stirring rack can complete the gas transmission work during rotation. The drive box is used to control the rotation speed of the inner stirring rack.

[0010] Preferably, one side of the wall-mounted frame is equipped with a rotatable adjustable baffle. The end of the adjustable baffle is in contact with the inner wall of the horizontal vacuum furnace. Both ends of the wall-mounted frame are provided with inclined side grooves. During the synthesis stage, it is necessary to ensure that the gas phase and powder are fully mixed. Traditional stirring methods generally result in a lower degree of mixing. During the synthesis stage, the adjustable baffle is controlled to expand outward. As the wall-mounted frame moves to the bottom, it will collect some of the powder. The powder is located in the cavity formed by the furnace wall, the edge of the wall-mounted frame, and the adjustable baffle. The cavity is open at both ends, and the powder will continuously flow out from both ends. As the wall-mounted frame rotates to the top, the powder will fall from top to bottom under the action of gravity, thereby fully mixing with the gas phase. With this setting, the powder as raw material is continuously dispersed in the horizontal vacuum furnace and fills the furnace. It can be mixed with the gas phase without dead corners, reducing problems such as uneven mixing and inefficient heating caused by powder accumulation. It also eliminates the need for a high-speed rotating inner stirring rack to achieve a relatively thorough mixing effect.

[0011] Preferably, the wall-mounted rack has multiple sliding slots on the side away from the horizontal vacuum furnace. A vibrating block is slidably engaged in the sliding slot, and an elastic element is provided at the bottom of the vibrating block and the sliding slot. After the synthesis stage, there will still be a lot of powder deposits on the surface of the inner stirring rack. During the jetting stage, the input airflow is changed to intermittent, which will not affect the cleaning of the jet. At the same time, the slot is connected to the airflow. When the airflow is input, it will push the vibrating block outward, generating impact vibration. When the airflow stops, it will return to its position under the action of the elastic element. With this setting, the inner stirring rack will continuously vibrate and shake off its own deposits during the synthesis and purification stages, and be discharged with the airflow, further ensuring the purification level of the furnace space during the purification stage.

[0012] Preferably, the outer side of the wall-mounted frame is equipped with a drive shaft for controlling the rotation of the adjustable cup plate. The adjustable cup plate includes a lower plate and a rotatable upper flap. The lower plate is fixed to the drive shaft. The opposite sides of the lower plate and the upper flap plate both have adsorption functions. During the purification stage, the crystals cannot be vigorously stirred, not only because vigorous stirring will cause the crystals to break and reduce the quality of the finished product, but also because the collision will cause the temperature to rise and the crystals to decompose. The best solution is theoretically to spread all the crystals flat, but there is not enough space. With the adjustable cup plate that can be viewed from above, when the adjustable cup plate is at its highest position, it unfolds itself, so that the outermost end of the unfolded part is in contact with the furnace wall, and as it moves downward, it transfers part of the crystals to its own surface. Under the adsorption effect, the crystals are adsorbed and spread flat on the unfolded surface, and it rotates with the adjustable cup plate for one revolution. When the adjustable cup plate rotates one revolution and inserts into the crystals again, the adsorption function is turned off, and the adsorption is turned on again in a short time. At this time, another batch of crystals can be adsorbed. After multiple wall-mounted frames repeat the above function, the crystals can be basically spread flat at a suitable temperature, and impurities can be discharged to the outside, which not only improves the purification efficiency, but also improves the quality of the finished product.

[0013] Preferably, the lower plate and the upper flip plate each have absorption holes covering the entire surface on their opposite sides, and a filter screen is laid on the opposite sides of the lower plate and the upper flip plate. The lower plate and the upper flip plate are rotatably connected by a pivot at their ends. The mesh size of the filter screen needs to be much smaller than the diameter of the crystal to ensure that the crystal is always adsorbed on the filter screen. The end of the connecting pipe is also connected to two different air pressure systems, which can be used for nitrogen input and low-concentration waste gas discharge, and undergo the adsorption process of cold trapping and adsorption core.

[0014] Preferably, a lifter is installed on the top surface of the lower plate near the drive shaft, and an adsorption sticker for adhering to the horizontal vacuum furnace is installed on the top surface of the upper plate. When the adjusting plate moves to the top, the lifter is used to lift the upper plate upwards. This can be done using an electric cylinder or other ejection device, allowing the surface of the upper plate to adhere to the furnace wall. The adsorption sticker is then used for adsorption and fixation. The adsorption sticker can be magnetically fixed, requiring only that a portion of the horizontal vacuum furnace is made of a non-magnetizable metal material. The maximum operating temperature of the horizontal vacuum furnace does not exceed 200 degrees Celsius, which will not cause the magnetic attraction to completely fail, thus achieving the adsorption and fixation effect.

[0015] Preferably, the lower plate is provided with a flat winding module inside, and the end of the winding module is connected to a winding rope. The winding rope is fixed to the upper flip plate. After purification, the winding module retracts the winding rope, thereby retracting and closing the upper flip plate.

[0016] Preferably, the horizontal vacuum furnace is wrapped with a heat-conducting oil jacket, and an oil pressure box is provided on the outside of the horizontal vacuum furnace. The oil pressure box and the heat-conducting oil jacket are connected by two circulation pipes. The end of the second negative pressure pipe is connected to an isolation box. Hot oil can be introduced into the heat-conducting oil jacket through the circulation pipes. Compared with steam heating, oil heating is more efficient and suitable for purification processes with strict temperature requirements. The isolation box can be equipped with a cold trap and adsorption device to complete the adsorption process of small impurities in the waste gas.

[0017] The beneficial effects of this invention are as follows: 1. The vacuum reactor for lithium hexafluorophosphate production described in this invention achieves an integrated preparation process for lithium hexafluorophosphate synthesis and purification reactions, eliminating problems such as air and moisture pollution caused by raw material transfer during synthesis and purification, leading to increased post-processing and reduced quality. A negative pressure pipe is used to handle large quantities of air, water vapor, phosphorus pentafluoride, and hydrogen fluoride. This negative pressure pipe is made of corrosion-resistant material and is connected to an external recovery buffer tank to temporarily store gases containing large amounts of phosphorus pentafluoride and hydrogen fluoride, which are then uniformly recovered using specialized equipment. In the purification stage, a negative pressure tube is used, connected to an external cold trap and adsorption core device. Because negative pressure adsorption needs to be generated continuously during the purification stage, such a large volume of air cannot be stored in storage equipment. After adsorption by the cold trap and adsorption core, the hydrogen fluoride and phosphorus pentafluoride contained in the gas in the purification stage have been basically absorbed. The subsequent air only needs to be directly connected to the alkaline scrubbing tower to meet the emission standards. This switchable negative pressure absorption system allows for smooth adaptation between the purification and synthesis stages, enabling joint operation and reducing transfer and post-treatment steps, thereby improving production efficiency.

[0018] 2. The vacuum reactor for lithium hexafluorophosphate production described in this invention, through the structural design of the internal stirring rack, can effectively disperse the raw material powder by utilizing the wall-mounted rack during its rotation, ensuring thorough mixing of the powder and gas phase and guaranteeing the smooth progress of the synthesis process. Simultaneously, in a slow-speed state, it can also allow the crystal exchange door to tumble, allowing the crystal to slowly release internal impurities under high temperature and negative pressure. The scraper can be made of an elastic material and must be corrosion-resistant. The elastic scraper, in contact with the horizontal vacuum furnace, can scrape off residues adhering to the furnace wall, including phosphorus pentafluoride, hydrogen fluoride, etc. The nozzle can spray gas along the moving direction of the internal stirring rack. The gas flow can be nitrogen, similar to the replacement gas, which not only further cleans the deposits on the furnace wall but also, combined with the nitrogen replacement process, allows for better transfer of the gas phase and small particles. During the scraping stage, negative pressure tubes are still used for absorption, absorbing the small particles generated during scraping along with the powder, ensuring that only clean crude crystals remain in the furnace during the purification process. This further reduces the content of residues during the purification stage, reduces the workload of the cold trap and adsorption core, and ensures the smooth preparation of the purified product. Attached Figure Description

[0019] The invention will now be further described with reference to the accompanying drawings.

[0020] Figure 1 This is a perspective view of the present invention; Figure 2 This is a cross-sectional view of the horizontal vacuum furnace of the present invention; Figure 3 This is a perspective view of the internal stirring rack of the present invention; Figure 4 This is a cross-sectional view of the internal stirring rack of the present invention; Figure 5 This is a perspective view of the wall-mounted frame and transmission side plate of the present invention; Figure 6 This is a perspective view of the adjusting flap of the present invention; Figure 7 This is a perspective view of the upper flip plate and the lower mounting plate of the present invention; In the diagram: 1. Horizontal vacuum furnace; 2. Heat transfer oil jacket; 3. Gas supply box; 4. Connector; 5. Negative pressure pipe one; 6. Negative pressure pipe two; 7. Isolation box; 8. Feeding door; 9. Connecting valve; 10. Circulation pipe; 11. Hydraulic pressure box; 12. Inner stirring rack; 13. Wall-mounted rack; 14. Connecting side plate; 15. Transmission side plate; 16. Drive box; 17. Scraper; 18. Adjusting baffle; 19. Connecting pipe; 20. Spray hole; 21. Vibrating block; 22. Side cutting groove; 23. Adsorption patch; 24. Drive shaft; 25. Lower plate; 26. Upper flap; 27. Rotating shaft; 28. Lifter; 29. ​​Winding rope; 30. Filter screen. Detailed Implementation

[0021] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0022] like Figures 1 to 7 As shown in the embodiment of the present invention, a vacuum reactor for the production of lithium hexafluorophosphate includes a horizontal vacuum furnace 1. The interior of the horizontal vacuum furnace 1 is provided with a rotatable inner stirring rack 12, which is attached to the inner wall of the horizontal vacuum furnace 1. The top of the horizontal vacuum furnace 1 is equipped with a feeding door 8 for feeding and discharging materials. The top of the horizontal vacuum furnace 1 is also equipped with a connecting valve 9 for releasing gas. The horizontal vacuum furnace 1 is equipped with a negative pressure pipe 5 and a negative pressure pipe 6 for vacuuming. Before use, check the equipment's sealing and ensure all valves are closed. After the check, prepare for the synthesis reaction by opening the feeding door 8 and adding lithium fluoride powder. Then close the feeding door 8 and use the negative pressure pipe 5 to evacuate the inside. Once the internal vacuum level is reached, transfer nitrogen gas through the connecting valve 9 and evacuate again. Repeat this process several times before proceeding to the next step. This step is to ensure that the moisture and air inside the furnace are completely evacuated and replaced, ensuring the smooth progress of the subsequent reaction. Fill the furnace with phosphorus pentafluoride gas through the connecting valve 9 while controlling the internal stirring rack 12 to quickly stir the lithium fluoride powder, allowing the powder and gas to mix thoroughly. Maintain the horizontal vacuum furnace 1 at 80 to 112 degrees Celsius for four to eight hours, and monitor the reaction conversion rate at all times. After the reaction is complete, close the connecting valve 9 and stop the gas supply. The phosphorus pentafluoride gas supply process involves rapid gas supply at the beginning, constant supply during the reaction stage, adjusting the supply rate according to the conversion rate, and gradually stopping the supply at the end stage to ensure the normal progress of the reaction. At this point, crude lithium hexafluorophosphate crystals, formed by the reaction of phosphorus pentafluoride and lithium fluoride, will be produced in the furnace. Unreacted lithium fluoride, unreacted phosphorus pentafluoride gas, byproducts (trace amounts of hydrogen fluoride and phosphorus trifluoride oxyfluoride), and adsorbed impurities (moisture, metal ions, etc.) will also be present. To ensure the smooth progress of subsequent purification reactions, negative pressure is applied again using the negative pressure tube 5 to remove phosphorus pentafluoride gas and other gaseous impurities. Simultaneously, the nitrogen replacement method described above is repeated multiple times to ensure complete removal of phosphorus pentafluoride and other gaseous phases before proceeding with the purification process. Since crystals have already formed, the rotation speed of the inner stirrer 12 is slowed down, gently agitating the crystals instead of violently breaking up the powder as in the synthesis reaction. The horizontal vacuum furnace 1 is then heated to 120-180 degrees Celsius. Between 100°C and 120°C, negative pressure tube 5 is sealed simultaneously, and negative pressure tube 6 is used for operation. Negative pressure tube 6 begins continuous negative pressure extraction to maintain an internal vacuum of 2 to 10 Pa. Under high temperature and low speed agitation, the impurities inside and on the surface of the crystal are the same as those remaining in the furnace during the synthesis stage. However, these impurities are combined with the crystal and are difficult to precipitate easily. They need to be combined with high temperature and agitation to be slowly discharged, thus improving the quality of the crude crystal. The purification reaction is maintained for 4 to 12 hours, and the hydrogen fluoride and moisture content are monitored online. The endpoint is determined when the hydrogen fluoride content is less than 50 ppm (parts per million) and the moisture content is less than 50 ppm. At this point, purification is stopped, and after the sample test is qualified, the crystal can be taken out to complete the purification. It can be processed in the bottom of the horizontal vacuum furnace. The equipment has an outlet, or the material can be removed from the top of the feeding gate 8 using an absorption device. This method reduces contact between the equipment's internal and external environments, minimizing contamination. This design enables an integrated preparation process for lithium hexafluorophosphate synthesis and purification, eliminating air and moisture pollution caused by raw material transfer during synthesis and purification, which leads to increased post-processing and reduced quality. Negative pressure pipe 5 is used to handle large quantities of air, water vapor, phosphorus pentafluoride, and hydrogen fluoride. Corrosion-resistant pipes are used for negative pressure pipe 5, which is connected to an external recovery buffer tank to temporarily store gases containing large amounts of phosphorus pentafluoride and hydrogen fluoride, and then uniformly recover them using specialized equipment. In the purification stage, negative pressure pipe 6 is used, and an external... The cold trap and adsorption core equipment is designed to continuously generate negative pressure adsorption during the purification stage. Such a large volume of air cannot be stored in storage devices. After adsorption by the cold trap and adsorption core, the hydrogen fluoride and phosphorus pentafluoride contained in the purified gas are essentially absorbed. Subsequent air can directly meet emission standards by connecting it to an alkaline scrubbing tower. Furthermore, treating waste gas containing large amounts of phosphorus pentafluoride through adsorption and cold trapping would be extremely costly, overloading the cold trap and adsorption equipment before the purification reaction. Therefore, these processes must be carried out separately. This switchable negative pressure absorption system allows for seamless adaptation between the purification and synthesis stages, enabling simultaneous operation and reducing transfer and post-treatment steps, thereby improving production efficiency.

[0023] The inner stirring rack 12 includes a connecting side plate 14 and a transmission side plate 15. The connecting side plate 14 and the transmission side plate 15 are fixedly connected by multiple wall-mounted brackets 13. Multiple scrapers 17 that are attached to the inner wall of the horizontal vacuum furnace 1 are connected to the outside of the wall-mounted brackets 13. Multiple spray holes 20 are opened on the outside of the inner stirring rack 12. During operation, the internal stirring rack 12's structure, while rotating, effectively utilizes the wall-mounted rack 13 to disperse the raw material powder, ensuring thorough mixing of the powder and gas phase and guaranteeing a smooth synthesis process. Simultaneously, at slow speeds, it allows the crystal exchange door to tumble, enabling the crystal to slowly release internal impurities under high temperature and negative pressure. The scraper 17, made of an elastic material and possessing corrosion resistance, adheres to the horizontal vacuum furnace 1, scraping away residues adhering to the furnace wall, including phosphorus pentafluoride and hydrogen fluoride. The nozzle 20 sprays airflow along the moving direction of the internal stirring rack 12. The airflow can be nitrogen, similar to the replacement gas, further cleaning the furnace wall deposits. Combined with the nitrogen replacement process, it allows for better transfer of the gas phase and small particles. During the scraping stage, the negative pressure tube 5 is still used for absorption, absorbing the small particles generated during scraping along with the powder, ensuring that only clean crude crystals remain in the furnace during purification. This further reduces the residue content during purification, decreases the workload of the cold trap and adsorption core, and ensures the smooth preparation of the purified product.

[0024] One end of the connecting side plate 14 is fixedly connected to a connecting pipe 19. The outer side of the horizontal vacuum furnace 1 is provided with a connector 4 that is rotatably engaged with the connecting pipe 19. A gas supply box 3 is installed at the bottom of the connector 4. The other end of the horizontal vacuum furnace 1 is equipped with a drive box 16 connected to the transmission side plate 15. During operation, the inner stirring rack 12 can complete the gas transmission work during rotation through the connection of the connecting pipe 19 and the connector 4. The drive box 16 is used to control the rotation speed of the inner stirring rack 12.

[0025] The wall-mounted frame 13 is equipped with a rotating adjustable pocket 18 on one side. The end of the adjustable pocket 18 is attached to the inner wall of the horizontal vacuum furnace 1. Inclined side grooves 22 are provided at both ends of the wall-mounted frame 13. During operation, it is necessary to ensure thorough mixing of the gas phase and powder in the synthesis stage. Traditional stirring methods generally result in only moderate mixing. In the synthesis stage, the control adjustment baffle 18 expands outward. As the wall-mounted frame 13 moves to the bottom, it scoops up some of the powder. The powder is located in the cavity formed by the furnace wall, the edge of the wall-mounted frame 13, and the adjustment baffle 18. The cavity is open at both ends, and the powder continuously flows out from both ends. As the wall-mounted frame 13 rotates to the top, the powder falls from top to bottom under the action of gravity, thus fully mixing with the gas phase. Through this setting, the powder, as raw material, is continuously dispersed in the horizontal vacuum furnace 1 and fills the furnace. It can mix with the gas phase without dead corners, reducing problems such as uneven mixing and inefficient heating caused by powder accumulation. It also eliminates the need for a high-speed rotating inner stirring frame 12 to achieve a relatively thorough mixing effect.

[0026] The wall-mounted frame 13 has multiple sliding slots on the side away from the horizontal vacuum furnace 1. A vibration block 21 is slidably engaged in the sliding slot, and elastic elements are provided at the bottom of the vibration block 21 and the sliding slot. During operation, after the synthesis stage, a significant amount of powder residue remains on the surface of the inner stirring rack 12. During the jetting stage of the nozzle 20, the incoming airflow is changed to intermittent, which does not affect the cleaning of the nozzle 20. At the same time, the slot is connected to the airflow. When the airflow is input, it will push the vibrating block 21 outward, generating impact vibration. When the airflow stops, it will return to its original position under the action of the elastic element. With this setting, the inner stirring rack 12 continuously vibrates and shakes off its own residue during the synthesis and purification stages, and it is discharged with the airflow, further ensuring the purification level of the furnace space during the purification stage.

[0027] The outer side of the wall-mounted bracket 13 is equipped with a drive shaft 24 for controlling the rotation of the adjustable pocket plate 18. The adjustable pocket plate 18 includes a lower plate 25 and a rotatable upper flap 26. The lower plate 25 is fixedly connected to the drive shaft 24. The opposite sides of the lower plate 25 and the upper flap 26 both have an adsorption function. During the purification process, the crystals should not be vigorously stirred, not only because vigorous stirring can cause crystal breakage and reduce the quality of the finished product, but also because collisions can cause the temperature to rise and the crystals to decompose. Theoretically, the best solution is to spread all the crystals flat, but there is not enough space. By using the adjustable cup 18, which can be viewed from above, when the adjustable cup 18 is at its highest position, it unfolds itself, so that the outermost part of the unfolded cup fits against the furnace wall, and as it moves downward, it transfers part of the crystals to its surface. Under the action of adsorption, the crystals are adsorbed and spread flat on the unfolded surface, and then rotate with the adjustable cup 18 for one revolution. When the adjustable cup 18 rotates one revolution and inserts into the crystals again, the adsorption function is turned off, and then the adsorption is turned on again after a short time. At this time, another batch of crystals can be adsorbed. After multiple wall-mounted racks 13 repeat the above function, the crystals can be kept in a basically flat state at a suitable temperature, and impurities can be discharged to the outside. This not only improves the purification efficiency, but also improves the quality of the finished product.

[0028] The lower plate 25 and the upper flip plate 26 are provided with absorption holes covering the entire surface on their opposite sides. The lower plate 25 and the upper flip plate 26 are provided with filter screens 30 on their opposite sides. The lower plate 25 and the upper flip plate 26 are rotatably connected by a pivot 27 at their ends. During operation, the mesh size of the filter screen 30 needs to be much smaller than the diameter of the crystal to ensure that the crystal is directly adsorbed on the filter screen 30. The end of the connecting pipe 19 is also connected to two different air pressure systems, which can be used for nitrogen input and low-concentration waste gas discharge, and undergo the adsorption work of cold trapping and adsorption core.

[0029] A lifter 28 is installed on the top surface of the lower plate 25 near the drive shaft 24, and an adsorption sticker 23 for attaching to the horizontal vacuum furnace 1 is installed on the top surface of the upper plate 26. During operation, when the adjusting plate 18 is moved to the top, the lifting device 28 is used to lift the upper flap 26 upwards. This can be used for lifting devices such as electric cylinders, allowing the surface of the upper flap 26 to adhere to the furnace wall. The adsorption sticker 23 is used for adsorption and fixation. The adsorption sticker 23 can be magnetically fixed. It is only necessary to use a non-magnetizable metal material in part of the horizontal vacuum furnace 1. The maximum operating temperature of the horizontal vacuum furnace 1 does not exceed 200 degrees Celsius, which will not cause the magnetic attraction to completely fail, thus achieving the adsorption and fixation effect.

[0030] The lower plate 25 is provided with a flat winding module inside, and the end of the winding module is connected to a winding rope 29, which is fixedly connected to the upper flip plate 26. During operation, after purification is completed, the winding module retracts the winding cable 29, thereby retracting and closing the upper flip plate 26.

[0031] The horizontal vacuum furnace 1 is wrapped with a heat transfer oil jacket 2 on the outside. An oil pressure box 11 is provided on the outside of the horizontal vacuum furnace 1. The oil pressure box 11 and the heat transfer oil jacket 2 are connected by two circulation pipes 10. The end of the negative pressure pipe 6 is connected to an isolation box 7. During operation, the hydraulic pressure box 11 can introduce hot oil into the hot oil jacket 2 through the circulation pipe 10. Compared with steam heating, oil heating is more efficient and suitable for purification processes with stringent temperature requirements. The isolation box 7 can be equipped with built-in cooling and adsorption equipment to complete the adsorption process of small amounts of impurities in the exhaust gas.

[0032] Before operation, check the equipment's sealing and ensure all valves are closed. After inspection, prepare for the synthesis reaction by opening the feeding door 8 and adding lithium fluoride powder. Then close the feeding door 8 and use the negative pressure pipe 5 to evacuate the interior. Once the internal vacuum level is reached, introduce nitrogen gas through the connecting valve 9 and evacuate again. Repeat this process multiple times before proceeding to the next step. This step ensures that moisture and air inside the furnace are completely removed and replaced, guaranteeing a smooth reaction. Simultaneously, fill the furnace with phosphorus pentafluoride gas through the connecting valve 9 while rapidly stirring the lithium fluoride powder using the internal stirring rack 12 to ensure thorough mixing of the powder and gas. Maintain the horizontal vacuum furnace 1 at 80-120 degrees Celsius for 4-8 hours, constantly monitoring the reaction conversion rate. After the reaction is complete, close the connecting valve 9 and stop the gas supply. The phosphorus pentafluoride gas supply process involves rapid initial supply, constant supply during the reaction phase, adjusting the supply rate according to the conversion rate, and gradually stopping the supply at the end stage to ensure the normal progress of the reaction. At this point, crude lithium hexafluorophosphate crystals, formed by the reaction of phosphorus pentafluoride and lithium fluoride, will be produced in the furnace. Unreacted lithium fluoride, unreacted phosphorus pentafluoride gas, byproducts (trace amounts of hydrogen fluoride and phosphorus trifluoride oxyfluoride), and adsorbed impurities (moisture, metal ions, etc.) will also be present. To ensure the smooth progress of subsequent purification reactions, negative pressure is applied again using the negative pressure tube 5 to remove phosphorus pentafluoride gas and other gaseous impurities. Simultaneously, the nitrogen replacement method described above is repeated multiple times to ensure complete removal of phosphorus pentafluoride and other gaseous phases before proceeding with the purification process. Since crystals have already formed, the rotation speed of the inner stirrer 12 is slowed down, gently agitating the crystals instead of violently breaking up the powder as in the synthesis reaction. The horizontal vacuum furnace 1 is then heated to 120-180 degrees Celsius. Between 100°C and 120°C, negative pressure tube 5 is sealed simultaneously, and negative pressure tube 6 is used for operation. Negative pressure tube 6 begins continuous negative pressure extraction to maintain an internal vacuum of 2 to 10 Pa. Under high temperature and low speed agitation, the impurities inside and on the surface of the crystal are the same as those remaining in the furnace during the synthesis stage. However, these impurities are combined with the crystal and are difficult to precipitate easily. They need to be combined with high temperature and agitation to be slowly discharged, thus improving the quality of the crude crystal. The purification reaction is maintained for 4 to 12 hours, and the hydrogen fluoride and moisture content are monitored online. The endpoint is determined when the hydrogen fluoride content is less than 50 ppm (parts per million) and the moisture content is less than 50 ppm. At this point, purification is stopped, and after the sample test is qualified, the crystal can be taken out to complete the purification. It can be processed in the bottom of the horizontal vacuum furnace. The equipment has an outlet, or the material can be removed from the top of the feeding gate 8 using an absorption device. This method reduces contact between the equipment's internal and external environments, minimizing contamination. This design enables an integrated preparation process for lithium hexafluorophosphate synthesis and purification, eliminating air and moisture pollution caused by raw material transfer during synthesis and purification, which leads to increased post-processing and reduced quality. Negative pressure pipe 5 is used to handle large quantities of air, water vapor, phosphorus pentafluoride, and hydrogen fluoride. Corrosion-resistant pipes are used for negative pressure pipe 5, which is connected to an external recovery buffer tank to temporarily store gases containing large amounts of phosphorus pentafluoride and hydrogen fluoride, and then uniformly recover them using specialized equipment. In the purification stage, negative pressure pipe 6 is used, and an external... The cold trap and adsorption core equipment is designed to continuously generate negative pressure adsorption during the purification stage. Such a large volume of air cannot be stored in storage devices. After adsorption by the cold trap and adsorption core, the hydrogen fluoride and phosphorus pentafluoride contained in the purified gas are essentially absorbed. Subsequent air can directly meet emission standards by connecting it to an alkaline scrubbing tower. Furthermore, treating waste gas containing large amounts of phosphorus pentafluoride through adsorption and cold trapping would be extremely costly, overloading the cold trap and adsorption equipment before the purification reaction. Therefore, these processes must be carried out separately. This switchable negative pressure absorption system allows for seamless adaptation between the purification and synthesis stages, enabling simultaneous operation and reducing transfer and post-treatment steps, thereby improving production efficiency.

[0033] The internal stirring rack 12 is designed to effectively disperse the raw material powder using the wall-mounted rack 13 during its rotation, ensuring thorough mixing of the powder and gas phase and facilitating the smooth progress of the synthesis process. Simultaneously, at slower speeds, it allows the crystal exchange gate to tumble, enabling the crystal to slowly release internal impurities under high temperature and negative pressure. The scraper 17, made of an elastic and corrosion-resistant material, adheres to the horizontal vacuum furnace 1 and removes residues adhering to the furnace wall, including phosphorus pentafluoride and hydrogen fluoride. The nozzle 20 sprays airflow along the moving direction of the internal stirring rack 12. This airflow, which can be nitrogen, is similar to the replacement gas, further cleaning the furnace wall and, combined with the nitrogen replacement process, allowing for better transfer of the gas phase and small particles. During the scraping stage, the negative pressure tube 5 is used for absorption, absorbing the small particles along with the powder, ensuring that only clean crude crystals remain in the furnace during purification. This further reduces the residue content during purification, decreases the workload of the cold trap and adsorption core, and ensures the smooth preparation of the purified product.

[0034] During operation, the inner stirring rack 12 can complete the gas transmission work through the connection of the connecting pipe 19 and the connector 4. The drive box 16 is used to control the rotation speed of the inner stirring rack 12.

[0035] During the synthesis stage, it is necessary to ensure thorough mixing of the gas phase and the powder. Traditional stirring methods generally result in only moderate mixing. During the synthesis stage, the control adjustment baffle 18 expands outward. As the wall-mounted frame 13 moves to the bottom, it scoops up some of the powder. The powder is located in the cavity formed by the furnace wall, the edge of the wall-mounted frame 13, and the adjustment baffle 18. The cavity is open at both ends, and the powder continuously flows out from both ends. As the wall-mounted frame 13 rotates to the top, the powder falls from top to bottom under the action of gravity, thus fully mixing with the gas phase. Through this setting, the powder, as the raw material, is continuously dispersed in the horizontal vacuum furnace 1 and fills the furnace. It can mix with the gas phase without dead corners, reducing problems such as uneven mixing and inefficient heating caused by powder accumulation. It also eliminates the need for a high-speed rotating inner stirring frame 12 to achieve a relatively thorough mixing effect.

[0036] After the synthesis stage, a lot of powder will remain on the surface of the inner stirring rack 12. During the jetting stage of the nozzle 20, the incoming airflow is changed to intermittent, which will not affect the cleaning of the nozzle 20. At the same time, the slot is connected to the airflow. When the airflow is input, it will push the vibrating block 21 outward, generating impact vibration. When the airflow stops, it will return to its original position under the action of the elastic element. With this setting, the inner stirring rack 12 will continuously vibrate and shake off its own deposits during the synthesis and purification stages, and these deposits will be discharged with the airflow, further ensuring the purification level of the furnace space during the purification stage.

[0037] During the purification stage, the crystals should not be vigorously stirred, not only because vigorous stirring will cause the crystals to break and reduce the quality of the finished product, but also because the collision will cause the temperature to rise and the crystals to decompose. The best solution in theory is to spread all the crystals flat, but there is not enough space. By using the adjustable cup 18, which can be viewed from above, when the adjustable cup 18 is at its top, it unfolds itself so that the outermost part of the unfolded part is in contact with the furnace wall, and as it moves downward, it transfers part of the crystals to its surface. Under the adsorption effect, the crystals are adsorbed and spread flat on the unfolded surface, and then rotate with the adjustable cup 18 for one revolution. When the adjustable cup 18 rotates one revolution and is inserted into the crystals again, the adsorption function is turned off, and then the adsorption is turned on again after a short time. At this time, another batch of crystals can be adsorbed. After multiple wall-mounted racks 13 repeat the above function, the crystals can be kept in a basically flat state at a suitable temperature, and impurities can be discharged to the outside. This not only improves the purification efficiency, but also improves the quality of the finished product.

[0038] The mesh size of the filter screen 30 needs to be much smaller than the diameter of the crystal to ensure that the crystal is directly adsorbed on the filter screen 30. The end of the connecting pipe 19 is also connected to two different air pressure systems, which can be used for nitrogen input and low-concentration waste gas discharge, and undergo the adsorption work of cold trapping and adsorption core.

[0039] When the adjusting plate 18 is moved to the top, the lifting device 28 is used to lift the upper flap 26 upwards. This can be done by lifting devices such as electric cylinders, so that the surface of the upper flap 26 is in contact with the furnace wall. The adsorption sticker 23 is used for adsorption and fixation. The adsorption sticker 23 can be magnetically fixed. It is only necessary to use a non-magnetizable metal material in part of the horizontal vacuum furnace 1. The maximum operating temperature of the horizontal vacuum furnace 1 does not exceed 200 degrees Celsius, which will not cause the magnetic attraction to completely fail, thus achieving the adsorption and fixation effect.

[0040] After purification is complete, the winding module retracts the winding cable 29, thereby retracting and closing the upper flip plate 26.

[0041] The hydraulic pressure box 11 can introduce hot oil into the hot oil jacket 2 through the circulation pipe 10. Compared with steam heating, oil heating is more efficient and suitable for purification processes with strict temperature requirements. The isolation box 7 can be equipped with a built-in cooling and adsorption device to complete the adsorption process of small amounts of impurities in the waste gas.

[0042] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A vacuum reactor for the production of lithium hexafluorophosphate, characterized in that: The system includes a horizontal vacuum furnace, which has a rotatable internal stirring rack that fits against the inner wall of the furnace. The top of the furnace is equipped with a feeding door for feeding and discharging materials, and a connecting valve for releasing gas is also installed on the top of the furnace. The furnace also contains two negative pressure pipes for vacuuming: a first negative pressure pipe and a second negative pressure pipe.

2. The vacuum reactor for producing lithium hexafluorophosphate according to claim 1, characterized in that: The inner stirring frame includes a connecting side plate and a transmission side plate, which are fixedly connected by multiple wall-mounted brackets. Multiple scrapers that fit against the inner wall of the horizontal vacuum furnace are connected to the outer side of the wall-mounted brackets, and multiple spray holes are opened on the outer side of the inner stirring frame.

3. The vacuum reactor for producing lithium hexafluorophosphate according to claim 2, characterized in that: One end of the connecting side plate is fixedly connected to a connecting pipe, and the outside of the horizontal vacuum furnace is provided with a connector that rotates and engages with the connecting pipe. A gas supply box is installed at the bottom of the connector, and a drive box connected to the transmission side plate is installed at the other end of the horizontal vacuum furnace.

4. The vacuum reactor for producing lithium hexafluorophosphate according to claim 3, characterized in that: One side of the wall-mounted frame is equipped with a rotatable adjustment pocket, the end of which is in contact with the inner wall of the horizontal vacuum furnace, and both ends of the wall-mounted frame are provided with inclined side grooves.

5. A vacuum reactor for producing lithium hexafluorophosphate according to claim 4, characterized in that: The wall-mounted frame has multiple sliding slots on the side away from the horizontal vacuum furnace. A vibration block is slidably engaged in the sliding slot, and an elastic element is provided at the bottom of the vibration block and the sliding slot.

6. A vacuum reactor for producing lithium hexafluorophosphate according to claim 5, characterized in that: The outer side of the wall-mounted bracket is equipped with a drive shaft for controlling the rotation of the adjustable pocket plate. The adjustable pocket plate includes a lower plate and a rotatable upper flap plate. The lower plate is fixedly connected to the drive shaft, and the opposite sides of the lower plate and the upper flap plate both have an adsorption function.

7. A vacuum reactor for producing lithium hexafluorophosphate according to claim 6, characterized in that: The lower plate and the upper flip plate are both provided with absorption holes covering the entire surface on their opposite sides. The lower plate and the upper flip plate are provided with filter screens on their opposite sides. The lower plate and the upper flip plate are rotatably connected by a pivot at their ends.

8. The vacuum reactor for producing lithium hexafluorophosphate according to claim 7, characterized in that: A lifter is installed on the top surface of the lower plate near the drive shaft, and an adsorption sticker for attaching to the horizontal vacuum furnace is installed on the top surface of the upper plate.

9. A vacuum reactor for producing lithium hexafluorophosphate according to claim 8, characterized in that: The lower plate has a flat winding module inside, and the end of the winding module is connected to a winding rope, which is fixed to the upper flip plate.

10. A vacuum reactor for producing lithium hexafluorophosphate according to claim 9, characterized in that: The horizontal vacuum furnace is wrapped with a heat transfer oil jacket on the outside, and an oil pressure box is provided on the outside of the horizontal vacuum furnace. The oil pressure box and the heat transfer oil jacket are connected by two circulation pipes, and the end of the second negative pressure pipe is connected to an isolation box.

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