Separation and purification device for lithium hexafluorophosphate production tail gas

Abstract

The utility model relates to the technical field of tail gas recovery equipment, in particular to a lithium hexafluorophosphate production tail gas separation and purification device which comprises a rectifying tower, a condenser, a reboiler, a hydrogen chloride recovery tank, a hydrogen fluoride recovery tank and a flash tank, the rectifying tower is provided with a first gas outlet end and a first liquid inlet end, and the first gas inlet end, the condenser, the flash tank and the first liquid inlet end are sequentially communicated; the condenser is provided with a first purified gas discharge end, the flash tank is provided with a second purified gas discharge end, and the first purified gas discharge end and the second purified gas discharge end are communicated with the hydrogen chloride recovery tank; the rectifying tower is provided with a first liquid outlet end and a first gas inlet end, and the first liquid outlet end, the reboiler and the first gas inlet end are communicated in sequence; the reboiler is provided with a first purified liquid discharge end, and the first purified liquid discharge end is communicated with the hydrogen fluoride recovery tank. The lithium hexafluorophosphate production tail gas separation and purification device provided by the utility model is favorable for reducing the energy consumption and improving the operation safety.

Description

Technical Field

[0001] This utility model relates to the technical field of tail gas recovery equipment, and in particular to a separation and purification device for tail gas produced from lithium hexafluorophosphate. Background Technology

[0002] Currently, lithium hexafluorophosphate is typically produced using a wet process. The production steps are as follows: phosphorus pentachloride reacts with anhydrous hydrogen fluoride to produce the intermediate products pentafluorophosphate and hydrogen chloride; the pentafluorophosphate then reacts with lithium fluoride dissolved in a hydrogen fluoride solution to produce lithium hexafluorophosphate. The entire reaction takes place in anhydrous hydrogen fluoride solution, where hydrogen fluoride acts as both a precursor and a solvent, thus requiring its excessive use. During the lithium hexafluorophosphate production process, the vigorous reaction during the feeding process causes a large amount of hydrogen fluoride to volatilize, which, along with the byproduct hydrogen chloride, is emitted from the reactor, forming the lithium hexafluorophosphate production tail gas.

[0003] The current conventional process for treating the tail gas from lithium hexafluorophosphate production involves installing a -30°C condenser at the reactor outlet to condense and recycle a portion of the hydrogen fluoride. The remaining uncondensed hydrogen fluoride and hydrogen chloride are then absorbed by water spray to obtain a mixed acid solution. The key problem with this tail gas treatment process is the low efficiency of the -30°C condensation, which fails to efficiently recover hydrogen fluoride, resulting in significant waste of hydrogen fluoride and only yielding a mixed waste liquid of hydrogen fluoride and hydrogen chloride, which requires further treatment.

[0004] To overcome the aforementioned shortcomings, the industry has developed the following process for treating the tail gas from lithium hexafluorophosphate production: the compressed and cooled tail gas is further cooled to separate it into gas and condensate, followed by distillation purification to achieve efficient separation of hydrogen fluoride and hydrogen chloride. However, this process relies on compressor pressurization, leading to a significant increase in energy consumption, and the system operates at high pressure throughout, posing substantial safety hazards. Utility Model Content

[0005] The purpose of this invention is to propose a separation and purification device for lithium hexafluorophosphate production tail gas. Under normal pressure, the device can achieve efficient separation of hydrogen fluoride and hydrogen chloride through the cooperation of a condenser, a reboiler and a flash tank. This not only helps to reduce energy consumption but also improves operational safety, thus overcoming the shortcomings of the prior art.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A separation and purification device for tail gas from lithium hexafluorophosphate production includes a distillation column, a condenser, a reboiler, a hydrogen chloride recovery tank, a hydrogen fluoride recovery tank, and a flash tank.

[0008] The distillation column has a first feed end in the middle for feeding the tail gas from lithium hexafluorophosphate production. The distillation column is used to separate the tail gas from lithium hexafluorophosphate production into a gas phase enriched with hydrogen chloride and a liquid phase enriched with hydrogen fluoride.

[0009] The upper part of the distillation column is provided with a first gas outlet and a first liquid inlet. The first gas inlet, the condenser, the flash tank and the first liquid inlet are connected in sequence by a pipeline. The condenser is used to condense the hydrogen chloride-enriched gas phase into hydrogen chloride gas and primary condensate. The flash tank is used to vaporize the primary condensate into hydrogen chloride gas and secondary condensate. The first liquid inlet is used to return the secondary condensate to the distillation column.

[0010] The condenser has a first purified gas outlet end, and the flash tank has a second purified gas outlet end. The first purified gas outlet end and the second purified gas outlet end are both connected to the hydrogen chloride recovery tank through pipelines. The hydrogen chloride recovery tank is used to recover the hydrogen chloride gas discharged from the first purified gas outlet end and the second purified gas outlet end.

[0011] The lower part of the distillation column is provided with a first liquid outlet and a first gas inlet. The first liquid outlet, the reboiler, and the first gas inlet are connected in sequence by a pipeline. The reboiler is used to evaporate the liquid at the bottom of the column into hydrogen chloride gas and hydrogen fluoride liquid. The first gas inlet is used to reflux the hydrogen chloride gas back to the distillation column.

[0012] The reboiler has a first purified liquid outlet, which is connected to the hydrogen fluoride recovery tank; the hydrogen fluoride recovery tank is used to recover the hydrogen fluoride liquid discharged from the first purified liquid outlet.

[0013] Furthermore, the first purified gas outlet is located at the top of the condenser, and the second purified gas outlet is located at the top of the flash tank.

[0014] Furthermore, a second liquid inlet is provided in the middle of the flash tank, and a second liquid outlet is provided at the bottom of the flash tank. The second liquid inlet is connected to the primary condensate output end of the condenser, and the second liquid outlet is connected to the first liquid inlet.

[0015] Furthermore, the number of flash tanks is at least two, and the two flash tanks are connected in parallel.

[0016] Furthermore, the number of reboilers is at least two, and the two reboilers are connected in parallel.

[0017] Furthermore, it also includes a liquid nitrogen tube, the liquid nitrogen output end of which is connected to the liquid nitrogen input end of the condenser;

[0018] The liquid nitrogen tube is equipped with a liquid nitrogen regulating valve, which is used to open and close the liquid nitrogen tube.

[0019] Furthermore, it also includes a pressure gauge, which is installed on the top of the condenser and is used to monitor the liquid nitrogen pressure in the condenser. The pressure gauge is electrically connected to the liquid nitrogen regulating valve.

[0020] Furthermore, it also includes a temperature sensor and a temperature display, the temperature sensor being located inside the condenser and used to monitor the temperature of liquid nitrogen in the condenser;

[0021] The temperature display is mounted on the top of the condenser and is electrically connected to the temperature sensor.

[0022] Furthermore, it also includes a nitrogen recovery device, which is connected to the nitrogen output terminal of the condenser, and the nitrogen recovery device is used to collect the nitrogen discharged from the nitrogen output terminal.

[0023] Furthermore, it also includes a tailpipe, the inlet end of which is connected to the tail gas outlet of the lithium hexafluorophosphate production unit, and the outlet end of which is connected to the first feed end.

[0024] The feed pipe is equipped with an exhaust gas regulating valve, which is used to open and close the exhaust gas pipe.

[0025] The technical solution provided by this utility model can include the following beneficial effects:

[0026] 1. Since the boiling point of hydrogen fluoride gas is 19.5℃ and the boiling point of hydrogen chloride gas is -85.05℃, the distillation column can separate the tail gas from the lithium hexafluorophosphate production process into a gas phase enriched with hydrogen chloride and a liquid phase enriched with hydrogen fluoride. The hydrogen chloride-enriched gas phase enters the condenser, and under the cooling effect of the condenser, most of the uncondensed hydrogen chloride gas in the hydrogen chloride-enriched gas phase enters the hydrogen chloride recovery tank through the first purified gas outlet for recovery, thereby achieving the recovery of high-purity hydrogen chloride gas. Simultaneously, the condensed primary condensate vaporizes in the flash tank, separating the residual hydrogen chloride gas in the primary condensate and allowing it to enter the hydrogen chloride recovery tank through the second purified gas outlet for further recovery, further improving the purity of the recovered hydrogen chloride.

[0027] 2. The liquid remaining after the primary condensate is vaporized in the flash tank to remove residual hydrogen chloride gas is the secondary condensate. The secondary condensate is refluxed into the distillation column through the first inlet and undergoes heat and mass exchange with the hydrogen chloride-enriched gas phase in the distillation column to obtain hydrogen fluoride gas and exchange liquid. The hydrogen fluoride gas obtained from the heat and mass exchange flows upward, while the exchange liquid continues to flow downward and mixes with the hydrogen fluoride-enriched liquid to form the bottom liquid (i.e., the bottom liquid is a mixture of the hydrogen fluoride-enriched liquid, the hydrogen chloride-enriched gas phase, and the secondary condensate obtained after heat exchange). The bottom liquid enters the reboiler through the first outlet, and the reboiler evaporates the bottom liquid into hydrogen chloride gas and hydrogen fluoride liquid. The hydrogen chloride gas in the bottom liquid returns to the distillation column through the first inlet, while the hydrogen fluoride liquid enters the hydrogen fluoride recovery tank through the first purified liquid outlet to obtain high-purity hydrogen fluoride, thereby achieving efficient separation of hydrogen fluoride and hydrogen chloride.

[0028] 3. The separation operation of this technical solution can achieve efficient separation of hydrogen fluoride and hydrogen chloride under normal pressure through the cooperation of condenser, reboiler and flash tank. No compressor is required, which helps to improve the safety of operation while reducing energy consumption. Attached Figure Description

[0029] Figure 1 This is a simplified structural diagram of a separation and purification device for tail gas from lithium hexafluorophosphate production, according to this utility model.

[0030] The components include: a distillation column 1, a first feed end 11, a first gas outlet 12, a first liquid inlet 13, a first liquid outlet 14, a first gas inlet 15, a condenser 2, a first purified gas outlet 21, a reboiler 3, a first purified liquid outlet 31, a hydrogen chloride recovery tank 4, a hydrogen fluoride recovery tank 5, a flash tank 6, a second purified gas outlet 61, a liquid nitrogen pipe 7, a liquid nitrogen regulating valve 71, a pressure gauge 8, a nitrogen recycling device 9, a tail gas pipe 10, and a tail gas regulating valve 101. Detailed Implementation

[0031] This technical solution provides a separation and purification device for lithium hexafluorophosphate production tail gas, including a distillation column 1, a condenser 2, a reboiler 3, a hydrogen chloride recovery tank 4, a hydrogen fluoride recovery tank 5, and a flash tank 6.

[0032] The distillation column 1 has a first feed end 11 in the middle for feeding the tail gas of lithium hexafluorophosphate production. The distillation column 1 is used to separate the tail gas of lithium hexafluorophosphate production to be purified into a gas phase enriched with hydrogen chloride and a liquid phase enriched with hydrogen fluoride.

[0033] The upper part of the distillation column 1 is provided with a first gas outlet 12 and a first liquid inlet 13. The first gas inlet 12, the condenser 2, the flash tank 6 and the first liquid inlet 13 are connected in sequence by a pipeline. The condenser 2 is used to condense the gas phase enriched with hydrogen chloride into hydrogen chloride gas and primary condensate. The flash tank 6 is used to vaporize the primary condensate into hydrogen chloride gas and secondary condensate. The first liquid inlet 13 is used to return the secondary condensate to the distillation column 1.

[0034] The condenser 2 has a first purified gas outlet 21, and the flash tank 6 has a second purified gas outlet 61. The first purified gas outlet 21 and the second purified gas outlet 61 are both connected to the hydrogen chloride recovery tank 4 through pipelines. The hydrogen chloride recovery tank 4 is used to recover the hydrogen chloride gas discharged from the first purified gas outlet 21 and the second purified gas outlet 61.

[0035] The lower part of the distillation column 1 is provided with a first liquid outlet 14 and a first gas inlet 15. The first liquid outlet 14, the reboiler 3 and the first gas inlet 15 are connected in sequence through a pipeline. The reboiler 3 is used to evaporate the liquid at the bottom of the column into hydrogen chloride gas and hydrogen fluoride liquid. The first gas inlet 15 is used to reflux the hydrogen chloride gas back to the distillation column 1.

[0036] The reboiler 3 has a first purified liquid outlet 31, which is connected to the hydrogen fluoride recovery tank 5. The hydrogen fluoride recovery tank 5 is used to recover the hydrogen fluoride liquid discharged from the first purified liquid outlet 31.

[0037] To address the technical problems of high energy consumption and insufficient safety in lithium hexafluorophosphate (LiPF6) production tail gas, this technical solution proposes a separation and purification device for LiPF6 production tail gas, such as... Figure 1 As shown, by operating under normal pressure, the efficient separation of hydrogen chloride and hydrogen fluoride in the tail gas of lithium hexafluorophosphate production is achieved without the need for a compressor. This overcomes the drawbacks of significantly increased energy consumption and high safety hazards caused by compressor pressurization, and improves operational safety while reducing energy consumption.

[0038] Specifically, the separation and purification device of this technical solution includes a distillation column 1, a condenser 2, a reboiler 3, a hydrogen chloride recovery tank 4, a hydrogen fluoride recovery tank 5, and a flash tank 6. The distillation column 1 has a first feed end 11, which feeds the lithium hexafluorophosphate production tail gas to be purified into the distillation column 1. Since the boiling point of hydrogen fluoride gas is 19.5℃ and the boiling point of hydrogen chloride gas is -85.05℃, the distillation column 1 can separate the lithium hexafluorophosphate production tail gas to be purified into a gas phase enriched with hydrogen chloride and a liquid phase enriched with hydrogen fluoride. The gas phase enriched with hydrogen chloride enters the condenser 2, and under the cooling effect of the condenser 2, most of the uncondensed hydrogen chloride gas in the gas phase enriched with hydrogen chloride enters the hydrogen chloride recovery tank 4 through the first purified gas outlet 21 for recovery, thereby achieving the recovery of high-purity hydrogen chloride gas. Meanwhile, the condensed primary condensate is vaporized in the flash tank 6, separating the residual hydrogen chloride gas in the primary condensate and allowing it to enter the hydrogen chloride recovery tank 4 through the second purified gas outlet 61 for recovery, further improving the purity of the recovered hydrogen chloride.

[0039] Furthermore, the liquid remaining after the primary condensate is vaporized in the flash tank 6 to remove residual hydrogen chloride gas becomes the secondary condensate. The secondary condensate is refluxed into the distillation column 1 through the first inlet 13 and undergoes heat and mass exchange with the hydrogen chloride-enriched gas phase in the distillation column 1 to obtain hydrogen fluoride gas and exchange liquid. The hydrogen fluoride gas obtained from the heat and mass exchange flows upward, while the exchange liquid continues to flow downward and mixes with the hydrogen fluoride-enriched liquid to form the bottom liquid (i.e., the bottom liquid is a mixture of the hydrogen fluoride-enriched liquid and the hydrogen chloride-enriched gas phase and the secondary condensate obtained after heat exchange). The bottom liquid enters the reboiler 3 through the first outlet 14, and the reboiler 3 evaporates the bottom liquid into hydrogen chloride gas and hydrogen fluoride liquid. The hydrogen chloride gas in the bottom liquid returns to the distillation column 1 through the first inlet 15, while the hydrogen fluoride liquid enters the hydrogen fluoride recovery tank 5 through the first purified liquid outlet 31 to obtain high-purity hydrogen fluoride, thereby achieving efficient separation of hydrogen fluoride and hydrogen chloride. Furthermore, the above separation operation can achieve efficient separation of hydrogen fluoride and hydrogen chloride under normal pressure through the cooperation of condenser, reboiler and flash tank, without the need for compressor, which helps to improve operational safety while reducing energy consumption.

[0040] It should be noted that the distillation column in this technical solution is a commonly used distillation column in the prior art. The specific structure will not be described in detail here. Its manufacturer can be Shanghai Sensong Pressure Vessel, model MS-HF-50. The specific manufacturer and model are not limited here.

[0041] To further explain, the first purified gas outlet 21 is located at the top of the condenser 2, and the second purified gas outlet 61 is located at the top of the flash tank 6.

[0042] Hydrogen chloride gas, due to its low density, naturally rises to the top of each component. Through the above-mentioned arrangement, the amount of liquid entrained in the hydrogen chloride gas can be reduced, resulting in higher purity of the recovered hydrogen chloride gas.

[0043] To further explain, the flash tank 6 has a second liquid inlet in the middle and a second liquid outlet in the bottom. The second liquid inlet is connected to the primary condensate output of the condenser, and the second liquid outlet is connected to the first liquid inlet 13.

[0044] With the above settings, the primary condensate enters from the middle of the flash tank 6, and the primary condensate has sufficient space and time to vaporize and separate within the flash tank 6. This extends the gas-liquid separation path and time, which is beneficial for improving separation efficiency, reducing the amount of liquid entrained in the hydrogen chloride gas, and resulting in higher purity of the recovered hydrogen chloride gas.

[0045] To further explain, the number of flash tanks 6 is at least two, and the two flash tanks 6 are connected in parallel.

[0046] By setting up two flash tanks 6 in parallel, the other flash tank 6 can be used if one of them fails, further increasing the reliability of the device.

[0047] To further explain, the number of reboilers 3 is at least two, and the two reboilers 3 are connected in parallel.

[0048] By setting up two reboilers 3, if one reboiler 3 fails, the other reboiler can continue to operate, maintaining the basic functions of the equipment and greatly reducing the risk of production interruption due to equipment failure. In addition, by setting up two reboilers 3, the operating status can be flexibly adjusted according to actual working conditions. If the tail gas processing volume is large, both reboilers 3 can be operated simultaneously; if the tail gas processing volume is small, only one needs to be operated, increasing the flexibility of the equipment.

[0049] Further explanation: It also includes a liquid nitrogen tube 7, the liquid nitrogen output end of which is connected to the liquid nitrogen input end of the condenser 2;

[0050] The liquid nitrogen tube 7 is equipped with a liquid nitrogen regulating valve 71, which is used to open and close the liquid nitrogen tube 7.

[0051] Compared to traditional cooling media (such as cooling water, chilled brine, etc.), liquid nitrogen can provide a lower cooling temperature. Therefore, this technical solution uses liquid nitrogen as a cold source in the condenser 2 by setting up a liquid nitrogen pipe 7, so that the gas phase enriched with hydrogen chloride can be condensed more quickly and completely in the condenser, thereby improving the condensation efficiency and the recovery rate of hydrogen chloride gas.

[0052] Furthermore, by setting a liquid nitrogen regulating valve 71 on the liquid nitrogen pipe 7, the flow rate of liquid nitrogen is controlled by the liquid nitrogen regulating valve 71, thereby making the condensation temperature of the condenser 2 controllable.

[0053] Further explanation includes a pressure gauge 8, which is installed on the top of the condenser 2. The pressure gauge 8 is used to monitor the liquid nitrogen pressure in the condenser 2, and the pressure gauge 8 is electrically connected to the liquid nitrogen regulating valve 71.

[0054] By monitoring the pressure of liquid nitrogen in condenser 2 using pressure gauge 8, operators can precisely adjust the liquid nitrogen flow rate using liquid nitrogen regulating valve 71 based on pressure changes. For example, if pressure gauge 8 shows a high pressure, there may be excessive liquid nitrogen supply; in this case, the opening of liquid nitrogen regulating valve 71 can be reduced to decrease the liquid nitrogen flow rate. Conversely, if the pressure is low, there may be insufficient liquid nitrogen supply; the opening of liquid nitrogen regulating valve 71 can be increased to increase the liquid nitrogen flow rate. This precise adjustment ensures that condenser 2 is always in optimal cooling condition, improving the efficiency and quality of exhaust gas separation and purification.

[0055] Further explanation: It also includes a temperature sensor and a temperature display. The temperature sensor is located inside the condenser 2 and is used to monitor the temperature of liquid nitrogen in the condenser 2.

[0056] The temperature display is mounted on the top of the condenser 2 and is electrically connected to the temperature sensor.

[0057] By installing a temperature sensor (not shown in the diagram) and a temperature display (not shown in the diagram), the temperature sensor can continuously monitor the temperature of liquid nitrogen in condenser 2 and transmit the temperature signal to the temperature display in real time. This allows operators to monitor the temperature changes of the liquid nitrogen at any time and promptly detect abnormal temperature fluctuations. If the liquid nitrogen temperature suddenly rises, it may indicate a condenser malfunction or insufficient liquid nitrogen supply. Operators can then take immediate action to avoid affecting production safety and product quality.

[0058] Further explanation: It also includes a nitrogen recovery device 9, which is connected to the nitrogen output terminal of the condenser 2. The nitrogen recovery device 9 is used to collect the nitrogen discharged from the nitrogen output terminal.

[0059] The nitrogen recycling device 9 is used to collect the nitrogen discharged from the nitrogen output end. The recovered nitrogen is then heated to near the outdoor temperature and its pressure is adjusted before being recycled back to the nitrogen pipeline network in the workshop for processes such as nitrogen pressing, nitrogen replacement, nitrogen purging, and nitrogen sealing.

[0060] It should be noted that, in order to ensure the cooling effect of condenser 2 on the hydrogen chloride-enriched gas phase, liquid nitrogen needs to be continuously supplied as a cold source. After liquid nitrogen vaporizes, its volume expands rapidly. If it is not discharged in time through the nitrogen outlet, the following effects will occur: (1) It will cause a sudden increase in pressure inside the condenser, which may exceed the pressure limit of the equipment and cause safety hazards; (2) Nitrogen accumulation will form a gas film thermal resistance, which will significantly reduce the heat exchange efficiency; (3) Over-cooling will cause the temperature of hydrogen chloride in the hydrogen chloride-enriched gas phase to be lower than its freezing point (-114℃) and freeze, causing pipeline blockage. Therefore, this technical solution needs to effectively discharge and recover the nitrogen obtained after liquid nitrogen vaporization through the nitrogen recycling device 9 in order to maintain the stability of system pressure, ensure heat exchange efficiency and avoid the risk of hydrogen chloride solidification.

[0061] Further explanation: It also includes a tail gas pipe 10, the inlet end of which is connected to the tail gas outlet of the lithium hexafluorophosphate production unit, and the outlet end of which is connected to the first feed end 11.

[0062] The feed pipe 10 is equipped with an exhaust gas regulating valve 101, which is used to open and close the exhaust gas pipe 10.

[0063] By setting the tail gas regulating valve 101, the opening of the tail gas pipe 10 can be precisely adjusted according to actual needs, thereby controlling the flow rate of tail gas entering the separation and purification device. For example, in the early stage of production, when the amount of tail gas generated is small, the valve opening can be appropriately reduced to prevent excessive air or other impurities from entering the device with the tail gas; while during peak production periods, when the amount of tail gas increases, the valve opening can be increased to ensure that the tail gas can enter the device for treatment in a timely and sufficient manner, thus ensuring the continuity and stability of production.

[0064] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0065] In the description of this utility model, it should be understood that the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this utility model. The directional terms "inner" and "outer" refer to the inner and outer contours of each component itself.

[0066] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0067] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this utility model.

[0068] The technical principles of this utility model have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of this utility model and should not be construed as limiting the scope of protection of this utility model in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of this utility model without any inventive effort, and these embodiments will all fall within the scope of protection of this utility model.

Claims

1. A separation and purification device for tail gas from lithium hexafluorophosphate production, characterized in that: This includes a distillation column, condenser, reboiler, hydrogen chloride recovery tank, hydrogen fluoride recovery tank, and flash tank; The distillation column has a first feed end in the middle for feeding the tail gas from lithium hexafluorophosphate production. The distillation column is used to separate the tail gas from lithium hexafluorophosphate production into a gas phase enriched with hydrogen chloride and a liquid phase enriched with hydrogen fluoride. The upper part of the distillation column is provided with a first gas outlet and a first liquid inlet. The first gas outlet, the condenser, the flash tank and the first liquid inlet are connected in sequence by a pipeline. The condenser is used to condense the hydrogen chloride-enriched gas phase into hydrogen chloride gas and primary condensate. The flash tank is used to vaporize the primary condensate into hydrogen chloride gas and secondary condensate. The first liquid inlet is used to return the secondary condensate to the distillation column. The condenser has a first purified gas outlet end, and the flash tank has a second purified gas outlet end. The first purified gas outlet end and the second purified gas outlet end are both connected to the hydrogen chloride recovery tank through pipelines. The hydrogen chloride recovery tank is used to recover the hydrogen chloride gas discharged from the first purified gas outlet end and the second purified gas outlet end. The lower part of the distillation column is provided with a first liquid outlet and a first gas inlet. The first liquid outlet, the reboiler, and the first gas inlet are connected in sequence by a pipeline. The reboiler is used to evaporate the liquid at the bottom of the column into hydrogen chloride gas and hydrogen fluoride liquid. The first gas inlet is used to reflux the hydrogen chloride gas back to the distillation column. The reboiler has a first purified liquid outlet, which is connected to the hydrogen fluoride recovery tank; the hydrogen fluoride recovery tank is used to recover the hydrogen fluoride liquid discharged from the first purified liquid outlet.

2. The separation and purification device for lithium hexafluorophosphate production tail gas according to claim 1, characterized in that: The first purified gas outlet is located at the top of the condenser, and the second purified gas outlet is located at the top of the flash tank.

3. The separation and purification device for lithium hexafluorophosphate production tail gas according to claim 1, characterized in that: The flash tank has a second liquid inlet in the middle and a second liquid outlet at the bottom. The second liquid inlet is connected to the primary condensate output of the condenser, and the second liquid outlet is connected to the first liquid inlet.

4. The separation and purification device for lithium hexafluorophosphate production tail gas according to claim 1, characterized in that: The number of flash tanks is at least two, and the two flash tanks are connected in parallel.

5. The separation and purification device for lithium hexafluorophosphate production tail gas according to claim 1, characterized in that: The number of reboilers is at least two, and the two reboilers are connected in parallel.

6. The separation and purification device for lithium hexafluorophosphate production tail gas according to claim 1, characterized in that: It also includes a liquid nitrogen tube, the liquid nitrogen output end of which is connected to the liquid nitrogen input end of the condenser; The liquid nitrogen tube is equipped with a liquid nitrogen regulating valve, which is used to open and close the liquid nitrogen tube.

7. The separation and purification device for lithium hexafluorophosphate production tail gas according to claim 6, characterized in that: It also includes a pressure gauge, which is installed on the top of the condenser and is used to monitor the liquid nitrogen pressure in the condenser. The pressure gauge is electrically connected to the liquid nitrogen regulating valve.

8. The separation and purification device for lithium hexafluorophosphate production tail gas according to claim 1, characterized in that: It also includes a temperature sensor and a temperature display, wherein the temperature sensor is located inside the condenser and is used to monitor the temperature of liquid nitrogen in the condenser; The temperature display is mounted on the top of the condenser and is electrically connected to the temperature sensor.

9. The separation and purification device for lithium hexafluorophosphate production tail gas according to claim 1, characterized in that: It also includes a nitrogen recovery device, which is connected to the nitrogen output terminal of the condenser. The nitrogen recovery device is used to collect the nitrogen discharged from the nitrogen output terminal.

10. The separation and purification device for lithium hexafluorophosphate production tail gas according to claim 1, characterized in that: It also includes a tail gas pipe, the inlet end of which is connected to the tail gas outlet of the lithium hexafluorophosphate production unit, and the outlet end of which is connected to the first feed end. The exhaust pipe is equipped with an exhaust gas regulating valve, which is used to open and close the exhaust pipe.

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