Lithium hexafluorophosphate tail gas treatment system

Abstract

The utility model relates to a lithium hexafluorophosphate tail gas treatment system. The lithium hexafluorophosphate tail gas treatment system comprises a reaction kettle, a first condenser, a second condenser, a compressor, a first gas-liquid separator, a second gas-liquid separator, a packed tower, a hydrogen fluoride storage tank, a phosphorus pentafluoride storage tank and a hydrogen chloride storage tank, an outlet of the first condenser is communicated with an inlet of the first gas-liquid separator through a second connecting pipe, a gas outlet of the first gas-liquid separator is communicated with an inlet of the compressor through a third connecting pipe, and a liquid outlet of the first gas-liquid separator is communicated with the hydrogen fluoride storage tank through a fourth connecting pipe; an inlet of the second condenser is communicated with an outlet of the compressor through a fifth connecting pipe, an outlet of the second condenser is communicated with an inlet of the second gas-liquid separator through a sixth connecting pipe, and a gas outlet of the second gas-liquid separator is communicated with an inlet of the packed tower through a seventh connecting pipe; a liquid outlet of the second gas-liquid separator is communicated with a phosphorus pentafluoride storage tank through an eighth connecting pipe, and a liquid outlet of the packed tower is communicated with a hydrogen chloride storage tank through a ninth connecting pipe.

Description

Technical Field

[0001] The utility model belongs to the technical field of lithium hexafluorophosphate production equipment, and particularly relates to a lithium hexafluorophosphate tail gas treatment system. Background Technique

[0002] As the most widely commercialized lithium ion battery electrolyte, lithium hexafluorophosphate has good ionic conductivity and electrochemical stability, and has become the core raw material for producing lithium ion battery electrolyte, accounting for about 43% of the total cost of electrolyte. With the rapid development of the new energy industry, its market demand has increased sharply, and the development prospect is good.

[0003] At present, the main domestic and foreign preparation processes of lithium hexafluorophosphate include hydrofluoric acid solvent method, gas-solid reaction method, organic solvent method, ion exchange method, etc. Among them, the hydrofluoric acid solvent method is the most important industrial production method at present. The process is to dissolve lithium fluoride in anhydrous hydrogen fluoride to prepare a lithium fluoride solution, and then introduce phosphorus pentafluoride gas into the solution for gas-liquid reaction to generate lithium hexafluorophosphate. It has the advantages of fast reaction speed, easy reaction control, high product conversion rate, relatively few side reactions, and high product purity.

[0004] The preparation of lithium hexafluorophosphate by the hydrofluoric acid solvent method mainly involves the reaction of phosphorus pentachloride and anhydrous hydrogen fluoride to generate phosphorus pentafluoride gas, which is then introduced into a LiF·HF solution formed by dissolving lithium fluoride in anhydrous hydrogen fluoride for reaction to obtain a synthesis solution, and then the product is obtained through cooling crystallization, separation and drying. During the preparation of phosphorus pentafluoride, due to the intense exothermic reaction, a large amount of anhydrous hydrogen fluoride volatilizes, accompanied by nitrogen as an inert protective gas. After the reaction, the gas mixture enters the hydrofluoric acid solution containing lithium fluoride through a filter and a condenser for reaction. During this process, a large amount of phosphorus pentafluoride reacts with lithium fluoride and is consumed. A large amount of hydrogen chloride gas, protective gas nitrogen, and a small amount of unreacted hydrogen fluoride and phosphorus pentafluoride gas generated by the reaction escape together as process tail gas. Most of the existing industrial common tail gas treatment methods first condense to remove most of the hydrogen fluoride gas, and then absorb the tail gas through a filler to remove hydrogen chloride and phosphorus pentafluoride that are difficult to condense under normal pressure, and by-product dilute hydrofluoric acid containing fluorine. The existing tail gas treatment methods have the following problems: ① The separation of fluorine and chlorine resources in the tail gas is not thorough, resulting in dilute hydrofluoric acid containing fluorine obtained during subsequent tail gas absorption, which is mostly used in the industry for the preparation of anhydrous calcium chloride, but the process is complex and the treatment cost is high. ② Excessive phosphorus pentafluoride gas in the synthesis stage is not recovered by effective means, but is dissolved in dilute hydrofluoric acid containing fluorine through tail gas absorption, which not only causes waste of fluorine and phosphorus resources, but also affects the reuse of dilute hydrofluoric acid containing fluorine. Content of the Utility Model

[0005] In order to solve the above technical problems, the utility model provides a lithium hexafluorophosphate tail gas treatment system.

[0006] The technical solution of a lithium hexafluorophosphate tail gas treatment system of the present utility model is as follows:

[0007] A lithium hexafluorophosphate tail gas treatment system includes a reaction kettle, a first condenser, a second condenser, a compressor, a first gas-liquid separator, a second gas-liquid separator, a packing tower, a hydrogen fluoride storage tank, a phosphorus pentafluoride storage tank, and a hydrogen chloride storage tank. The inlet of the first condenser is communicated with the reaction kettle through a first connecting pipe, the outlet of the first condenser is communicated with the inlet of the first gas-liquid separator through a second connecting pipe, the gas outlet of the first gas-liquid separator is communicated with the inlet of the compressor through a third connecting pipe, the liquid outlet of the first gas-liquid separator is communicated with the hydrogen fluoride storage tank through a fourth connecting pipe, the inlet of the second condenser is communicated with the outlet of the compressor through a fifth connecting pipe, the outlet of the second condenser is communicated with the inlet of the second gas-liquid separator through a sixth connecting pipe, the gas outlet of the second gas-liquid separator is communicated with the inlet of the packing tower through a seventh connecting pipe, the liquid outlet of the second gas-liquid separator is communicated with the phosphorus pentafluoride storage tank through an eighth connecting pipe, and the liquid outlet of the packing tower is communicated with the hydrogen chloride storage tank through a ninth connecting pipe.

[0008] Further, a tenth connecting pipe is connected to the seventh connecting pipe through a three-way joint, and the end of the tenth connecting pipe extends into the reaction kettle.

[0009] Further, the lower end of the tenth connecting pipe extends into the reaction kettle near the bottom.

[0010] Further, a spray pipe is provided on the packing tower, a nozzle is provided at the end of the spray pipe, a reflux pipe is provided on the lower side of the packing tower, and a cooling structure is provided between the spray pipe and the reflux pipe.

[0011] Further, the cooling structure includes a third condenser and a circulation pump. The inlet of the circulation pump is communicated with the packing tower through an eleventh connecting pipe, the outlet of the circulation pump is communicated with the inlet of the third condenser through a twelfth connecting pipe, and the outlet of the third condenser is communicated with the spray pipe through a thirteenth connecting pipe.

[0012] The present utility model provides a lithium hexafluorophosphate tail gas treatment system, and its beneficial effects are as follows:

[0013] When the lithium hexafluorophosphate tail gas treatment system of the present utility model is in use, the lithium hexafluorophosphate tail gas (HCl, N 2 , HF, PF 5 mixed gas) generated by the reaction kettle enters the first condenser through the first connecting pipe. The first condenser condenses the mixed gas, and the HF in the mixed gas becomes liquid. The mixed gas and the HF liquid enter the first gas-liquid separator through the second connecting pipe, and the HF liquid enters the hydrogen fluoride storage tank through the fourth connecting pipe. The lithium hexafluorophosphate tail gas (HCl, N 2 , PF5 The mixed gas) enters the compressor through the third connecting pipe for pressurization, so that the boiling points of phosphorus pentachloride and hydrogen chloride are both raised above -35°C. In the industrial production of lithium hexafluorophosphate, a refrigerant of -45°C is generally used. The pressurized mixed gas enters the second condenser through the fifth connecting pipe, and the second condenser can condense it by cooling. Most of the phosphorus pentafluoride gas and part of the hydrogen chloride gas can be removed by pressurized condensation. The phosphorus pentafluoride-free liquid enters the phosphorus pentafluoride-free storage tank through the eighth connecting pipe. However, since hydrogen chloride accounts for a high proportion in the tail gas and cannot be completely liquefied, and the critical temperature of nitrogen is -147.05°C, the main components in the lithium hexafluorophosphate tail gas are finally nitrogen, hydrogen chloride, trace amounts of phosphorus pentafluoride and hydrogen fluoride gas. The lithium hexafluorophosphate tail gas enters the reaction kettle through the tenth connecting pipe for gas-liquid stirring. The main component of the treated lithium hexafluorophosphate tail gas is hydrogen chloride. The lithium hexafluorophosphate tail gas enters the packed tower through the seventh connecting pipe, and water is used to absorb hydrogen chloride to obtain a hydrogen chloride solution. The hydrogen chloride solution enters the hydrogen chloride storage tank through the ninth connecting pipe. For the absorption medium circulating in the system, as the absorption process progresses, the heat of solution increases more and more, and the increase in the temperature of the absorption liquid is inevitable, which will reduce the absorption effect. In order to increase the absorption effect, the absorption circulating water can be cooled to maintain a high absorption capacity of the whole system. The lithium hexafluorophosphate tail gas treatment system of the present utility model studies the tail gas treatment technology generated in the process of producing lithium hexafluorophosphate by the hydrofluoric acid solvent method, and determines a clean, green and efficient recovery process: hydrogen fluoride is removed by conventional condensation, and then phosphorus pentafluoride is removed by compression condensation. The low-temperature tail gas with the main components of nitrogen and hydrogen chloride is recycled to production, and finally hydrogen chloride and other trace polluting gases are removed by water absorption to make the waste gas meet the specified emission standards. The whole treatment process is practical and feasible, which not only effectively reduces environmental pollution, but also significantly reduces the industrial production cost of lithium hexafluorophosphate, and has good economic benefits. Description of the Drawings

[0014] Figure 1 is the process structure diagram of the lithium hexafluorophosphate tail gas treatment system of the present utility model;

[0015] In the figure: 1. Reaction kettle; 2. First condenser; 3. Second condenser; 4. Third condenser; 5. First gas-liquid separator; 6. Second gas-liquid separator; 7. Circulation pump; 8. Compressor; 9. Packed tower; 10. Hydrogen fluoride storage tank; 11. Phosphorus pentafluoride-free storage tank; 12. Hydrogen chloride storage tank; 13. First connecting pipe; 14. Second connecting pipe; 15. Third connecting pipe; 16. Fourth connecting pipe; 17. Fifth connecting pipe; 18. Sixth connecting pipe; 19. Seventh connecting pipe; 20. Eighth connecting pipe; 21. Ninth connecting pipe; 22. Tenth connecting pipe; 23. Eleventh connecting pipe; 24. Twelfth connecting pipe; 25. Thirteenth connecting pipe; 26. Spray pipe. Detailed Embodiments

[0016] The present utility model will be further described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0017] A specific embodiment of the lithium hexafluorophosphate tail gas treatment system of the present utility model is as Figure 1 shown, including a reaction kettle 1, a first condenser 2, a second condenser 3, a compressor 8, a first gas-liquid separator 5, a second gas-liquid separator 6, a packed tower 9, a hydrogen fluoride storage tank 10, a phosphorus pentafluoride storage tank 11, and a hydrogen chloride storage tank 12. The inlet of the first condenser 2 is connected to the reaction kettle 1 through a first connecting pipe 13, the outlet of the first condenser 2 is connected to the inlet of the first gas-liquid separator 5 through a second connecting pipe 14, the gas outlet of the first gas-liquid separator 5 is connected to the inlet of the compressor 8 through a third connecting pipe 15, the liquid outlet of the first gas-liquid separator 5 is connected to the hydrogen fluoride storage tank 10 through a fourth connecting pipe 16, the inlet of the second condenser 3 is connected to the outlet of the compressor 8 through a fifth connecting pipe 17, the outlet of the second condenser 3 is connected to the inlet of the second gas-liquid separator 6 through a sixth connecting pipe 18, the gas outlet of the second gas-liquid separator 6 is connected to the inlet of the packed tower 9 through a seventh connecting pipe 19, the liquid outlet of the second gas-liquid separator 6 is connected to the phosphorus pentafluoride-free storage tank through an eighth connecting pipe 20, and the liquid outlet of the packed tower 9 is connected to the hydrogen chloride storage tank 12 through a ninth connecting pipe 21.

[0018] A tenth connecting pipe 22 is connected to the seventh connecting pipe 19 through a tee joint, and the end of the tenth connecting pipe 22 extends into the reaction kettle 1. The lower end of the tenth connecting pipe 22 extends into the reaction kettle 1 near the bottom. A spray pipe 26 is provided on the packed tower 9, a nozzle is provided at the end of the spray pipe 26, a reflux pipe is provided on the lower side of the packed tower 9, and a cooling structure is provided between the spray pipe 26 and the reflux pipe. The cooling structure includes a third condenser 4 and a circulation pump 7. The inlet of the circulation pump 7 is connected to the packed tower 9 through an eleventh connecting pipe 23, the outlet of the circulation pump 7 is connected to the inlet of the third condenser 4 through a twelfth connecting pipe 24, and the outlet of the third condenser 4 is connected to the spray pipe 26 through a thirteenth connecting pipe 25.

[0019] When the lithium hexafluorophosphate tail gas treatment system of the present utility model is in use, the lithium hexafluorophosphate tail gas (HCl, N 2 , HF, PF 5 mixed gas) generated by the reaction kettle 1 enters the first condenser 2 through the first connecting pipe 13. The first condenser 2 condenses the mixed gas. The HF in the mixed gas becomes liquid. The mixed gas and the HF liquid enter the first gas-liquid separator 5 through the second connecting pipe 14. The HF liquid enters the hydrogen fluoride storage tank 10 through the fourth connecting pipe 16. The lithium hexafluorophosphate tail gas (HCl, N 2 , PF 5The mixed gas) enters the compressor 8 through the third connecting pipe 15 for pressurization, so that the boiling points of phosphorus pentachloride and hydrogen chloride are both raised above -35°C. In the industrial production of lithium hexafluorophosphate, a refrigerant of -45°C is generally used. The pressurized mixed gas enters the second condenser 3 through the fifth connecting pipe 17, and can be condensed by cooling in the second condenser 3. Most of the phosphorus pentafluoride gas and part of the hydrogen chloride gas can be removed by pressurized condensation. The phosphorus pentafluoride-free liquid enters the phosphorus pentafluoride-free storage tank through the eighth connecting pipe 20. However, since hydrogen chloride accounts for a high proportion in the tail gas and cannot be completely liquefied, and the critical temperature of nitrogen is -147.05°C, the main components in the final lithium hexafluorophosphate tail gas are nitrogen, hydrogen chloride, trace amounts of phosphorus pentafluoride and hydrogen fluoride gases. The lithium hexafluorophosphate tail gas enters the reaction kettle 1 through the tenth connecting pipe 22 for gas-liquid stirring. The main component of the treated lithium hexafluorophosphate tail gas is hydrogen chloride. The lithium hexafluorophosphate tail gas enters the packed tower 9 through the seventh connecting pipe 19, and hydrogen chloride is absorbed with water to obtain a hydrogen chloride solution. The hydrogen chloride solution enters the hydrogen chloride storage tank 12 through the ninth connecting pipe 21. For the absorption medium circulating in the system, as the absorption process proceeds, more and more heat of solution is generated, and the increase in the temperature of the absorption liquid is inevitable, which will reduce the absorption effect. In order to enhance the absorption effect, the absorption circulating water can be cooled to maintain a high absorption capacity of the whole system. The lithium hexafluorophosphate tail gas treatment system of the present invention studies the tail gas treatment technology generated in the process of producing lithium hexafluorophosphate by the hydrofluoric acid solvent method, and determines a clean, green and efficient recovery process: removing hydrogen fluoride by conventional condensation, then removing phosphorus pentafluoride by compression condensation, recycling the low-temperature tail gas with the main components of nitrogen and hydrogen chloride to production, and finally absorbing hydrogen chloride and other trace polluting gases with water to make the waste gas meet the specified emission standards. The whole treatment process is practical and feasible, not only effectively reducing environmental pollution, but also significantly reducing the industrial production cost of lithium hexafluorophosphate, and having good economic benefits.

[0020] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A lithium hexafluorophosphate tail gas treatment system, characterized in that: The invention comprises a reactor, a first condenser, a second condenser, a compressor, a first gas-liquid separator, a second gas-liquid separator, a packing tower, a hydrogen fluoride storage tank, a phosphorus pentafluoride storage tank and a hydrogen chloride storage tank, wherein the inlet of the first condenser is connected to the reactor through a first connecting pipe, the outlet of the first condenser is connected to the inlet of the first gas-liquid separator through a second connecting pipe, the gas outlet of the first gas-liquid separator is connected to the inlet of the compressor through a third connecting pipe, the liquid outlet of the first gas-liquid separator is connected to the hydrogen fluoride storage tank through a fourth connecting pipe, the inlet of the second condenser is connected to the outlet of the compressor through a fifth connecting pipe, the outlet of the second condenser is connected to the inlet of the second gas-liquid separator through a sixth connecting pipe, the gas outlet of the second gas-liquid separator is connected to the inlet of the packing tower through a seventh connecting pipe, the liquid outlet of the second gas-liquid separator is connected to the phosphorus pentafluoride storage tank through an eighth connecting pipe, and the liquid outlet of the packing tower is connected to the hydrogen chloride storage tank through a ninth connecting pipe.

2. The lithium hexafluorophosphate tail gas treatment system according to claim 1, characterized in that: The seventh connecting pipe is connected to a tenth connecting pipe via a three-way joint, and an end of the tenth connecting pipe extends into the interior of the reaction kettle.

3. The lithium hexafluorophosphate tail gas treatment system according to claim 2, characterized in that: The lower end of the tenth connecting pipe extends into the reactor close to the bottom.

4. The lithium hexafluorophosphate tail gas treatment system according to claim 1, characterized in that: The packing tower is provided with a spray pipe, the end of the spray pipe is provided with a nozzle, the lower side of the packing tower is provided with a reflux pipe, and a cooling structure is provided between the spray pipe and the reflux pipe.

5. The lithium hexafluorophosphate tail gas treatment system according to claim 4, characterized in that: The cooling structure includes a third condenser and a circulation pump, the inlet of the circulation pump is connected to the packing tower through an eleventh connecting pipe, the outlet of the circulation pump is connected to the inlet of the third condenser through a twelfth connecting pipe, and the outlet of the third condenser is connected to the spray pipe through a thirteenth connecting pipe.

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