Multifunctional air separation device for preparing liquid oxygen by using liquid oxygen self-pressurization evaporator to liquefy air and nitrogen and using liquid nitrogen to flow backwards

Abstract

The invention discloses a multifunctional air separation device for preparing liquid oxygen by liquefying air and nitrogen through a liquid oxygen self-pressurization evaporator and pouring liquid nitrogen backwards. Comprising an air filtering and compressing system, a pre-cooling system, an air purifying unit, a main heat exchanger, a liquid oxygen evaporator, a low-pressure expansion machine, a rectifying tower, a liquid air and liquid nitrogen subcooler, a high-purity oxygen tower, an argon extracting system, a medium-pressure nitrogen pipe network, a liquid oxygen pipe network, a nitrogen liquefier, a heat exchanger I and a gas-liquid separator, the output of the liquid oxygen evaporator is provided with a pressure oxygen pipeline, the pressure oxygen pipeline exchanges heat through the main heat exchanger and then is output and stored, the output of the bottom of the liquid oxygen evaporator is provided with a product liquid oxygen pipeline, the medium-pressure nitrogen pipe network is output to the nitrogen liquefier through the heat exchanger I, the input of the liquid oxygen pipe network is connected with the nitrogen liquefier, and the nitrogen liquefier is connected with the gas-liquid separator. The hydrogen-free argon production process and the oxygen external compression mode are adopted, the liquid oxygen self-pressurization function is achieved, air and nitrogen are liquefied, and the multifunctional characteristic is achieved.

Description

Technical Field

[0001] This invention relates to the field of air separation technology, specifically to a multifunctional air separation device that uses a liquid oxygen self-pressurizing evaporator to liquefy air and nitrogen, and liquid nitrogen backfilling to produce liquid oxygen. Background Technology

[0002] In industrial production, air separation units are key equipment for obtaining industrial gases such as oxygen, nitrogen, and argon, and are widely used in many industries including metallurgy, chemical engineering, energy, and medicine. With the rapid development of industry, increasingly higher requirements are being placed on the purity and output of industrial gases, as well as the energy consumption and safety of the production process.

[0003] Currently, traditional air separation units have certain limitations in product production, with relatively simple functions, capable of producing only a few types of gaseous or liquid products, making it difficult to meet diverse industrial needs. For example, some small and medium-sized air separation units mainly produce oxygen and nitrogen, unable to simultaneously and stably produce high-value-added products such as high-purity oxygen, liquid argon, and liquid nitrogen, thus limiting their application scope. Furthermore, existing units have low integration levels and poor coordination between systems, resulting in low overall operating efficiency. They also fall short in fulfilling the functions of liquefying air and nitrogen, making it difficult to efficiently obtain liquid products.

[0004] In the gas separation process of air separation units, argon, as an important rare gas, has a boiling point between oxygen and nitrogen, making it difficult to separate directly from air. A specialized argon extraction system is required. Traditional argon extraction processes often employ hydrogenation for oxygen removal, where hydrogen is added to crude argon, causing the oxygen to react with the hydrogen in the presence of a catalyst to produce water. The water is then removed by drying to obtain pure argon. However, this process has significant drawbacks: firstly, hydrogen is a flammable and explosive gas, increasing the system's safety risks and requiring extremely high standards for explosion-proof and leak-proof equipment design; secondly, the hydrogenation reaction requires an additional hydrogen supply system and catalyst bed, increasing process complexity and equipment investment. It also presents problems such as incomplete reaction leading to limited argon purity and the need for further processing. Furthermore, the reaction process consumes energy, reducing the overall energy efficiency of the system.

[0005] Traditional internal oxygen compression technology involves compressing liquid oxygen inside a cold box. Under high pressure, liquid oxygen is prone to reacting with contaminants that may be present in the cold box, posing a relatively high safety hazard.

[0006] Traditional air separation devices have significant shortcomings in terms of cooling balance, pressure regulation, and energy consumption control. Insufficient cooling can easily lead to a decrease in distillation efficiency. The oxygen pressure increase relies on a high-power compressor, which also results in high energy consumption. At the same time, they are limited in terms of the flexibility and diversity of product extraction, making it difficult to produce gas products of various purities simultaneously and efficiently. Furthermore, their energy recovery and utilization are not perfect, resulting in energy waste.

[0007] Based on a deep understanding of the shortcomings of existing technologies, and through innovative designs in process flow, equipment structure, and other aspects, a more advanced and reliable technical solution has been developed for the industrial gas production field, promoting the industry to a higher level of development. Therefore, a multifunctional air separation unit has been developed that uses a liquid oxygen self-pressurizing evaporator to liquefy air and nitrogen and liquid nitrogen backfilling to produce liquid oxygen. Summary of the Invention

[0008] To address the problems mentioned in the background section, this invention provides a multifunctional air separation unit that uses a liquid oxygen self-pressurized evaporator to liquefy air and nitrogen, and liquid nitrogen backfilling to produce liquid oxygen.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a multifunctional air separation unit that uses a liquid oxygen self-pressurizing evaporator to liquefy air and nitrogen and liquid nitrogen backfilling to produce liquid oxygen, comprising an air filtration and compression system, a precooling system, an air purification unit, a main heat exchanger, a liquid oxygen evaporator, a low-pressure expander, a distillation column, a liquid air and liquid nitrogen subcooler, a high-purity oxygen tower, an argon extraction system, a medium-pressure nitrogen pipeline network, a liquid oxygen pipeline network, a nitrogen liquefaction unit, a heat exchanger I, and a gas-liquid separator; The air filtration and compression system, precooling system, and air purification unit are connected in sequence. The distillation column includes an upper column, a lower column, and a main condenser-evaporator. The air purification unit outputs an air pipeline. The air pipeline reaches the lower column after heat exchange in the main heat exchanger. The air pipeline outputs a liquid oxygen evaporator. The liquid oxygen evaporator outputs liquid air to the lower and upper columns. Liquid oxygen is output from the bottom of the upper column and enters the liquid oxygen evaporator. The liquid oxygen evaporator outputs a pressurized oxygen pipeline. The pressurized oxygen is output and stored after heat exchange in the main heat exchanger. The bottom of the liquid oxygen evaporator outputs a product liquid oxygen pipeline. The bottom of the upper column has an atmospheric pressure product oxygen pipeline. The atmospheric pressure product oxygen is output and stored via the main heat exchanger. The air pipeline output connects to a low-pressure expander. The inlet pipeline of the low-pressure expander has a central extraction pipeline and a bottom extraction pipeline respectively installed within the main heat exchanger. After expansion, the air from the low-pressure expander enters the upper column. After preliminary distillation in the lower column, oxygen-enriched liquid air is obtained at the bottom. The top of the lower column is equipped with a pressurized nitrogen pipeline and a pure liquid nitrogen pipeline. The pressurized nitrogen pipeline is discharged and stored after heat exchange in the main heat exchanger. The oxygen-enriched liquid air and pure liquid nitrogen pipelines are discharged and enter the upper column via a liquid air-liquid nitrogen subcooler. The pure oxygen tower is equipped with a high-purity oxygen tower evaporator. The output of the pressure nitrogen pipeline is connected to the high-purity oxygen tower evaporator. The output of the high-purity oxygen tower evaporator is connected to the upper tower. Oxygen obtained at the top of the high-purity oxygen tower is sent back to the lower part of the lower tower. The bottom of the high-purity oxygen tower is equipped with a product high-purity liquid oxygen pipeline. The middle part of the upper tower is connected to the argon extraction system. The lower tower is equipped with a replenishing liquid nitrogen pipeline. The top of the upper tower is equipped with a low-pressure nitrogen pipeline. The low-pressure nitrogen pipeline is output and stored after passing through a liquid air-liquid nitrogen subcooler and a main heat exchanger. The argon extraction system includes a crude argon tower I, a crude argon tower II, and a refined argon tower connected in sequence, with the middle of the upper tower connected to the crude argon tower I; The medium-pressure nitrogen pipeline is output to the nitrogen liquefaction unit via heat exchanger I. The liquid oxygen pipeline is connected to the nitrogen liquefaction unit. The nitrogen liquefaction unit is connected to the gas-liquid separator. The medium-pressure nitrogen from the medium-pressure nitrogen pipeline and the oxygen from the nitrogen liquefaction unit exchange heat through heat exchanger I and are liquefied and output through the nitrogen liquefaction unit. The output of the gas-liquid separator is then connected to the low-pressure nitrogen pipeline. The liquid oxygen from the liquid oxygen pipeline exchanges heat with the nitrogen entering the nitrogen liquefaction unit and is vaporized. It then exchanges heat with the medium-pressure nitrogen from the medium-pressure nitrogen pipeline in heat exchanger I and is output and stored.

[0010] In a preferred embodiment of the present invention, the air filtration and compression system includes a self-cleaning air filter and an air turbine compressor. The self-cleaning air filter is connected to the air turbine compressor. The output of the air turbine compressor is connected to a precooling system. The output of the air turbine compressor is provided with a circulating heat exchange path. The top output of the argon tower is provided with a circulating pipeline. The circulating pipeline reaches the air purification unit after passing through a liquid air-liquid nitrogen subcooler and a main heat exchanger. A heat exchanger II is provided between the circulating pipeline and the circulating heat exchange path.

[0011] In a preferred embodiment of the present invention, the air purification unit includes a molecular sieve adsorber I and a molecular sieve adsorber II, wherein the molecular sieve adsorber I and the molecular sieve adsorber II are connected, and an electric heater and a silencer are respectively connected to the molecular sieve adsorber I and the molecular sieve adsorber II.

[0012] As a preferred embodiment of the present invention, pneumatic valves I are provided on the pipelines from the liquid oxygen evaporator to the lower and upper towers, respectively.

[0013] In a preferred embodiment of the present invention, the low-pressure expander is connected to a booster compressor, the air pipeline output is connected to the booster compressor, the booster compressor is connected to a cooler, and the cooler output passes through the main heat exchanger to the low-pressure expander.

[0014] As a preferred embodiment of the present invention, a waste nitrogen pipeline is provided at the upper part of the upper tower. The waste nitrogen pipeline enters the air purification unit and the precooling system respectively after being reheated by the liquid air-liquid nitrogen subcooler and the main heat exchanger.

[0015] As a preferred embodiment of the present invention, the atmospheric pressure product oxygen pipeline is connected to the pressure oxygen pipeline, and a pneumatic valve II is provided on the pipeline between the atmospheric pressure product oxygen pipeline and the pressure oxygen pipeline.

[0016] As a preferred embodiment of the present invention, a pneumatic valve III is provided on the bottom extraction pipeline.

[0017] In a preferred embodiment of the present invention, the bottom of the crude argon tower I is refluxed to the upper tower, the top output of the crude argon tower I is connected to the crude argon tower II, the lower output of the crude argon tower I is connected to the high-purity oxygen tower, the top of the crude argon tower II is refluxed to the upper tower, liquid air is fed into the crude argon tower II after passing through a liquid air-liquid nitrogen subcooler, a crude argon condenser is installed on the crude argon tower II, the output of the crude argon condenser reaches the middle of the refined argon tower, a refined argon condenser and a refined argon evaporator are installed on the refined argon tower, the top of the refined argon tower is refluxed to the upper tower, the output of the pressure nitrogen pipeline is connected to the refined argon evaporator, the output of the refined argon evaporator is refluxed to the upper tower, and a liquid argon pipeline is installed at the bottom output of the refined argon tower.

[0018] As a preferred embodiment of the present invention, the crude argon tower II is provided with a reflux liquid path, which enters the crude argon tower I by being pressurized by a circulating pressure pump.

[0019] By adopting the above technical solution, the advantages of the present invention compared with the prior art are: 1. Air first enters the air filtration and compression system to remove impurities and compress it. Then it enters the pre-cooling system for pre-cooling. Afterwards, it enters the air purification unit to further remove moisture, carbon dioxide, and other impurities. The air treated by the purification unit is divided into two parts: one part enters the main heat exchanger via an air pipeline and reaches the lower column; the other part is output to the liquid oxygen evaporator and reaches the lower column. Simultaneously, another part of the air output enters the low-pressure expander, expands, and then enters the upper column for distillation. The lower column provides cooling. Air undergoes preliminary distillation in the lower column, yielding oxygen-enriched liquid air at the bottom. The top of the lower column outputs pressurized nitrogen and pure liquid nitrogen via pressurized nitrogen and pure liquid nitrogen lines, respectively. The pressurized nitrogen is stored in a cold box after heat exchange in the main heat exchanger. The oxygen-enriched liquid air and pure liquid nitrogen are subcooled by the liquid air / liquid nitrogen subcooler before entering the upper column for further distillation. The liquid oxygen output from the bottom of the upper column enters the liquid oxygen evaporator. The evaporated oxygen is then stored in a cold box after heat exchange in the main heat exchanger via a pressurized oxygen line. The product liquid oxygen output from the bottom of the liquid oxygen evaporator is processed through a product... Liquid oxygen is discharged from the pipeline and stored in the liquid oxygen storage tank. Low-pressure nitrogen from the top of the upper column is discharged and stored in the cold box after passing through a liquid air-liquid nitrogen subcooler and the main heat exchanger. Part of the nitrogen discharged from the pressure nitrogen pipeline enters the high-purity oxygen tower evaporator to provide cooling for the high-purity oxygen tower. The nitrogen after heat exchange enters the upper column, where it processes the material from the lower part of the crude argon tower I. The oxygen obtained at its top is sent back to the lower part of the lower tower, and high-purity liquid oxygen is discharged from its bottom. In the argon extraction system, the argon fraction from the middle of the upper tower enters the crude argon tower I and undergoes further distillation through the crude argon tower II and the refined argon tower. Liquid argon is extracted, and medium-pressure nitrogen from the medium-pressure nitrogen pipeline enters the nitrogen liquefaction unit after passing through heat exchanger I. It exchanges heat with liquid oxygen from the liquid oxygen pipeline. After being liquefied, the medium-pressure nitrogen is output and stored through the nitrogen liquefaction unit. Liquid oxygen is vaporized after exchanging heat with nitrogen and then enters heat exchanger I to exchange heat with medium-pressure nitrogen from the medium-pressure nitrogen pipeline. Finally, oxygen is output and stored. The entire system has a high degree of integration and the entire process has the function of liquefying air and nitrogen. It can simultaneously produce oxygen, nitrogen, liquid oxygen, high-purity oxygen, liquid argon, and liquid nitrogen products. It has the characteristics of multiple functions, and the products have high purity and stable quality. 2. The process of this invention adopts a hydrogen-free distillation process to produce argon, which eliminates the need for hydrogen gas, thus eliminating the safety hazards caused by hydrogen gas. At the same time, it can produce high-purity argon gas products, which can meet the requirements of high-end industries for argon gas purity. 3. By using liquid nitrogen backfilling, the cooling capacity is replenished in a timely manner through the liquid nitrogen replenishment pipeline in the lower column, which ensures the stable operation of the distillation process, improves the product yield and purity, and improves the start-up characteristics and adaptability to variable loads of the unit. 4. The system adopts an external oxygen compression method. The oxygen is stored in the cold box after heat exchange in the main heat exchanger, while the compression equipment of this system is not in the cold box. This facilitates maintenance, reduces safety risks, and the liquid oxygen evaporator has a self-pressurization function, which can flexibly adjust the oxygen pressure, reduce the energy consumption of external compression, and thus improve the efficiency of external compression to meet the gas demand of different scenarios. 5. The layout of each system is reasonable. Through the main heat exchanger, liquid air and liquid nitrogen subcooler, heat exchanger I, heat exchanger II and cooler, heat exchange can be fully carried out, which improves energy utilization efficiency and reduces the energy consumption of the device. 6. The main heat exchanger is equipped with a middle extraction pipeline and a bottom extraction pipeline through the inlet pipeline of the low-pressure expander. The temperature can be regulated by adjusting the work process of the gas in the expander. The inlet and outlet temperatures can be flexibly controlled to meet the needs of different working conditions. 7. The system consists of a medium-pressure nitrogen pipeline network, a liquid oxygen pipeline network, a nitrogen liquefaction unit, and a gas-liquid separator. It uses a liquid oxygen backflow method to liquefy nitrogen and obtain liquid nitrogen products. The nitrogen produced by the gas-liquid separator is connected in parallel to the low-pressure nitrogen pipeline to form an auxiliary system. It has a high degree of integration with the main system, allows for flexible allocation of nitrogen production, and has good energy cascade utilization efficiency. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram illustrating the system principle of the present invention; In the diagram: 1. Main heat exchanger; 2. Liquid oxygen evaporator; 3. Low-pressure expander; 4. Distillation column; 5. Liquid air / liquid nitrogen subcooler; 6. High-purity oxygen tower; 7. Medium-pressure nitrogen pipeline; 8. Liquid oxygen pipeline; 9. Nitrogen liquefaction unit; 10. Heat exchanger I; 11. Gas-liquid separator; 12. Upper tower; 13. Lower tower; 14. Main condenser / evaporator; 15. Air pipeline; 16. Pressurized oxygen pipeline; 17. Product liquid oxygen pipeline; 18. Atmospheric pressure product oxygen pipeline; 19. Intermediate extraction pipeline; 20. Bottom extraction pipeline; 21. Pressurized nitrogen pipeline; 22. Pure liquid nitrogen pipeline; 23. High-purity oxygen tower evaporator; 24. Product high-purity liquid oxygen pipeline; 25. Make-up liquid nitrogen pipeline; 26. Low-pressure nitrogen pipeline. 27. Crude Argon Tower I; 28. Crude Argon Tower II; 29. ​​Refined Argon Tower; 30. Air-cooled Tower; 31. Water-cooled Tower; 32. Self-cleaning Air Filter; 33. Air Turbine Compressor; 34. Circulating Heat Exchange Circuit; 35. Circulating Pipeline; 36. Heat Exchanger II; 37. Molecular Sieve Adsorber I; 38. Molecular Sieve Adsorber II; 39. Electric Heater; 40. Silencer; 41. Pneumatic Valve I; 42. Booster; 43. Cooler; 44. Sludge Nitrogen Gas Pipeline; 45. Pneumatic Valve II; 46. Pneumatic Valve III; 47. Crude Argon Condenser; 48. Refined Argon Condenser; 49. Refined Argon Evaporator; 50. Liquid Argon Pipeline; 51. Reflux Liquid Circuit; 52. Circulating Pump. 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] Please see Figure 1 The present invention provides a technical solution: a multifunctional air separation unit that uses a liquid oxygen self-pressurizing evaporator to liquefy air and nitrogen and liquid nitrogen backfill to produce liquid oxygen, including an air filtration and compression system, a precooling system, an air purification unit, a main heat exchanger 1, a liquid oxygen evaporator 2, a low-pressure expander 3, a distillation column 4, a liquid air and liquid nitrogen subcooler 5, a high-purity oxygen tower 6, an argon extraction system, a medium-pressure nitrogen pipeline network 7, a liquid oxygen pipeline network 8, a nitrogen liquefaction unit 9, a heat exchanger 110, and a gas-liquid separator 11; An air filtration and compression system, a precooling system, and an air purification unit are connected in sequence. The distillation column 4 includes an upper column 12, a lower column 13, and a main condenser-evaporator 14. The air purification unit outputs an air pipeline 15. The air pipeline 15 reaches the lower column 13 after heat exchange in the main heat exchanger 1. The output of the air pipeline 15 is connected to the liquid oxygen evaporator 2. The liquid oxygen evaporator 2 outputs liquid air to the lower column 13 and the upper column 12. Liquid oxygen is output from the bottom of the upper column 12 and enters the liquid oxygen evaporator 2. The liquid oxygen evaporator 2 outputs a pressurized oxygen pipeline 16. The pressurized oxygen pipeline 16 is output and stored after heat exchange in the main heat exchanger 1. The bottom of the liquid oxygen evaporator 2 outputs a product liquid oxygen pipeline 17. The bottom of the upper column 12 is equipped with an atmospheric pressure product oxygen pipeline 18. The atmospheric pressure product oxygen pipeline 18 is output and stored through the main heat exchanger 1. Air line 15 outputs to low-pressure expander 3. The inlet line of low-pressure expander 3 has a central extraction line 19 and a bottom extraction line 20 respectively installed in the main heat exchanger 1. After expansion by low-pressure expander 3, the air enters the upper column 12. After preliminary distillation in the lower column 13, oxygen-enriched liquid air is obtained at the bottom of the lower column 13. The top of the lower column 13 has a pressurized nitrogen line 21 and a pure liquid nitrogen line 22. The pressurized nitrogen line 21 is discharged and stored after heat exchange in the main heat exchanger 1. The oxygen-enriched liquid air and pure liquid nitrogen lines 22 are discharged and enter the upper column 12 through the liquid air / liquid nitrogen subcooler 5. The pure oxygen tower 6 is equipped with a high-purity oxygen tower evaporator 23. The output of the pressure nitrogen pipeline 21 is connected to the high-purity oxygen tower evaporator 23. The output of the high-purity oxygen tower evaporator 23 is connected to the upper tower 12. The oxygen obtained at the top of the high-purity oxygen tower 6 is sent back to the lower part of the lower tower 13. The bottom output of the high-purity oxygen tower 6 is equipped with a high-purity liquid oxygen pipeline 24. The middle part of the upper tower 12 is connected to the argon extraction system. The lower tower 13 is equipped with a replenishing liquid nitrogen pipeline 25. The top of the upper tower 12 is equipped with a low-pressure nitrogen pipeline 26. The low-pressure nitrogen pipeline 26 is output and stored after passing through the liquid air-liquid nitrogen subcooler 5 and the main heat exchanger 1. The argon extraction system includes crude argon tower I27, crude argon tower II28 and refined argon tower 29 connected in sequence, with crude argon tower I27 connected in the middle of the upper tower 12; The medium-pressure nitrogen pipeline 7 is output to the nitrogen liquefaction unit 9 via heat exchanger I10. The liquid oxygen pipeline 8 is connected to the nitrogen liquefaction unit 9. The nitrogen liquefaction unit 9 is connected to the gas-liquid separator 11. The medium-pressure nitrogen from the medium-pressure nitrogen pipeline 7 and the oxygen from the nitrogen liquefaction unit 9 exchange heat through heat exchanger I10 and are liquefied and output through the nitrogen liquefaction unit 11. The output of the gas-liquid separator 11 is connected to the low-pressure nitrogen pipeline 26. The liquid oxygen from the liquid oxygen pipeline 8 exchanges heat with the nitrogen entering the nitrogen liquefaction unit 11 and is vaporized. It then enters the heat exchanger I10 and exchanges heat with the medium-pressure nitrogen from the medium-pressure nitrogen pipeline 7 before being output and stored.

[0023] In this implementation scheme, the specific process flow is as follows: Air first enters the air filtration and compression system to remove impurities and compress the air, then enters the precooling system for precooling, and then enters the air purification unit to further remove impurities such as moisture and carbon dioxide. After being treated by the air purification unit, part of the air enters the lower column 13 through the air pipeline 15 and is heat-exchanged by the main heat exchanger 1, while the other part is output through the air pipeline 15 to the liquid oxygen evaporator 2 and then to the lower column 13. At the same time, another part of the air output from the air pipeline 15 enters the low-pressure expander 3, and after expansion, enters the upper column 12 to provide cooling for the distillation column 4. The lower column 13 performs preliminary distillation on the air, and oxygen-enriched air is obtained at the bottom. Liquid air is discharged from the top of the lower column 13 via pressurized nitrogen line 21 and pure liquid nitrogen line 22, respectively. Pressurized nitrogen line 21 is discharged after heat exchange in the main heat exchanger 1 and stored in a cold box. Oxygen-enriched liquid air and pure liquid nitrogen are subcooled by liquid air-liquid nitrogen subcooler 5 and then enter the upper column 12 for further distillation. Liquid oxygen from the bottom of the upper column 12 enters the liquid oxygen evaporator 2. The evaporated oxygen is discharged via pressurized oxygen line 16 into the main heat exchanger 1 and then stored in a cold box. Product liquid oxygen from the bottom of the liquid oxygen evaporator 2 is discharged through product liquid oxygen line 17 and stored in a liquid oxygen storage tank. Low-pressure nitrogen from the top of the upper column 12 is discharged via liquid air-liquid nitrogen subcooler 5 and the main heat exchanger 1 and stored in a cold box. Part of the nitrogen output from column 27 enters the high-purity oxygen tower evaporator 23 to provide cooling for column 6. After heat exchange, the nitrogen enters the upper column 12. Column 6 processes the material from the lower part of the crude argon tower I27. The oxygen obtained at the top is sent back to the lower part of the lower column 13, and high-purity liquid oxygen is output from the bottom. In the argon extraction system, the argon fraction in the middle of the upper column 12 enters the crude argon tower I27 and undergoes rectification in the crude argon tower II28 and the refined argon tower 29 to extract liquid argon. The medium-pressure nitrogen from the medium-pressure nitrogen pipeline 7 enters the nitrogen liquefaction unit 9 after passing through heat exchanger I10, where it exchanges heat with the liquid oxygen input from the liquid oxygen pipeline 8. After being liquefied, the medium-pressure nitrogen is output and stored through the nitrogen liquefaction unit 9. After heat exchange and vaporization with nitrogen, the liquid oxygen enters the heat exchanger I1. The system exchanges heat with medium-pressure nitrogen in medium-pressure nitrogen pipeline 7, and then outputs oxygen for storage. The entire system has a high degree of integration and the entire process has the function of liquefying air and nitrogen. It can simultaneously produce oxygen, nitrogen, liquid oxygen, high-purity oxygen, liquid argon, and liquid nitrogen products, which are multifunctional and have high product purity and stable quality. The process of this invention adopts a hydrogen-free distillation process, which eliminates the need for hydrogen and eliminates the safety hazards caused by hydrogen. At the same time, it can produce high-purity argon products, which meet the requirements of high-end industries for argon purity. The liquid nitrogen backfill method is used to replenish the cooling capacity in time through the liquid nitrogen replenishment pipeline of the lower tower 13, which ensures the stable operation of the distillation process, improves the product yield and purity, and improves the start-up characteristics and load adaptability of the device.The system employs external oxygen compression, with oxygen being exchanged and stored in a cold box after being output from the main heat exchanger 1. The compression equipment itself is not located within the cold box, facilitating maintenance and reducing safety risks. The liquid oxygen evaporator 2 features a self-pressurizing function, allowing for flexible adjustment of oxygen pressure and reducing energy consumption from external compression, thereby improving its efficiency and meeting gas demand in various scenarios. The system layout is rational, with the main heat exchanger 1, liquid air / liquid nitrogen subcooler 5, heat exchanger I10, heat exchanger II36, and cooler 43 ensuring sufficient heat exchange, improving energy utilization efficiency and reducing overall energy consumption. The low-pressure expander 3 further enhances the system's performance. The inlet pipeline is equipped with a medium-extraction pipeline 19 and a bottom-extraction pipeline 20 within the main heat exchanger 1. Its core principle is to regulate temperature by adjusting the work process of the gas within the expander, allowing for flexible control of the inlet and outlet temperatures to meet different operating conditions. The system comprises a medium-pressure nitrogen pipeline network 7, a liquid oxygen pipeline network 8, a nitrogen liquefier 9, and a gas-liquid separator 11. Using a liquid oxygen backflow method, nitrogen is liquefied to obtain liquid nitrogen. The nitrogen produced by the gas-liquid separator 11 is connected in parallel to the low-pressure nitrogen pipeline 26, forming an auxiliary system. This system has a high degree of integration with the main system, allowing for flexible allocation of nitrogen production and excellent energy cascade utilization efficiency.

[0024] Specifically, the precooling system includes an air-cooled tower 30 and a water-cooled tower 31. The installation and connection structure of the air-cooled tower 30 and the water-cooled tower 31 is conventional existing technology, resulting in good air precooling effect. The liquid oxygen evaporator 2 uses a self-pressurizing element, requiring no external power and relying on the gas pressure generated during its own evaporation process to achieve pressurization. After a series of rectification and separation processes in the crude argon tower I27, crude argon tower II28, and refined argon tower 29, high-purity liquid argon is enriched at the bottom of the refined argon tower 29.

[0025] As a preferred embodiment of the present invention, the air filtration and compression system includes a self-cleaning air filter 32 and an air turbine compressor 33. The self-cleaning air filter 32 is connected to the air turbine compressor 33. The output of the air turbine compressor 33 is connected to the precooling system. The output of the air turbine compressor 33 is provided with a circulating heat exchange path 34. The top output of the argon tower 29 is provided with a circulating pipeline 35. The circulating pipeline 35 reaches the air purification unit after passing through the liquid air-liquid nitrogen subcooler 5 and the main heat exchanger 1. A heat exchanger II 36 is provided between the circulating pipeline 35 and the circulating heat exchange path 34.

[0026] In this embodiment, the self-cleaning air filter 32 filters dust, particulate matter, and other impurities from the raw material air to prevent impurities from entering. The air turbine compressor 33 compresses the filtered air to the pressure required by the process, providing power for the pre-cooling, purification, and distillation separation of the air. The setting of the circulating heat exchange path 34 can reduce the temperature of the compressed air in advance, reduce the load on the subsequent pre-cooling system, and improve energy utilization efficiency. After being reheated by the liquid air-liquid nitrogen subcooler 5 and the main heat exchanger 1 through the circulating pipeline 35, the compressed air is sent to the air purification unit. Its core function is to recover cold energy and provide a cold source, reducing the system's demand for external cold energy and reducing energy consumption.

[0027] As a further preferred embodiment of the present invention, the air purification unit includes a molecular sieve adsorber I37 and a molecular sieve adsorber II38, with molecular sieve adsorber I37 and molecular sieve adsorber II38 connected together, and each of the molecular sieve adsorber I37 and molecular sieve adsorber II38 is respectively connected to an electric heater 39 and a silencer 40.

[0028] In this embodiment, molecular sieve adsorber I37 and molecular sieve adsorber II38 operate alternately to remove impurities such as carbon dioxide, moisture, and hydrocarbons in the air purification unit. Electric heater 39 can heat the regeneration gas to facilitate subsequent impurity removal, and silencer 40 can reduce operating noise.

[0029] As a preferred embodiment of the present invention, pneumatic valves I41 are provided on the pipelines from the liquid oxygen evaporator 2 to the lower tower 13 and the upper tower 12 respectively.

[0030] In this embodiment, the flow rate can be flexibly adjusted according to actual needs by setting the pneumatic valve I41.

[0031] As a further preferred embodiment of the present invention, the low-pressure expander 3 is connected to a booster 42, the air pipeline 15 is connected to the booster 42, the booster 42 is connected to a cooler 43, and the output of the cooler 43 goes to the low-pressure expander 3 after passing through the main heat exchanger 1.

[0032] In this embodiment, the above-described structure can effectively provide a cold source for the distillation column.

[0033] As a preferred embodiment of the present invention, the upper part of the upper tower 12 is provided with a waste nitrogen pipeline 44, which enters the air purification unit and the precooling system respectively after being reheated by the liquid air-liquid nitrogen subcooler 5 and the main heat exchanger 1.

[0034] In this embodiment, the waste nitrogen pipeline 44 can recover the cold energy of the waste nitrogen and supply the regeneration gas source, realizing the energy recycling of the air separation unit and improving the system energy efficiency. Specifically, the waste nitrogen pipeline 44 is connected to the circulation pipeline 35.

[0035] As a preferred embodiment of the present invention, the atmospheric pressure product oxygen pipeline 18 is connected to the pressure oxygen pipeline 16, and a pneumatic valve II45 is provided on the pipeline between the atmospheric pressure product oxygen pipeline 18 and the pressure oxygen pipeline 16.

[0036] In this embodiment, the above structure can effectively integrate the oxygen output channel, enabling the integration of oxygen at different pressure levels in the same output system, reducing the cost of laying independent pipelines, simplifying the system structure, and allowing for precise control of flow and pressure through the pneumatic valve II45 to adapt to the needs of switching operating conditions.

[0037] As a preferred embodiment of the present invention, a pneumatic valve III46 is provided on the bottom extraction pipeline 20.

[0038] In this embodiment, the pneumatic valve III46 can be used to precisely control the pumping volume and achieve closed-loop temperature control. The bottom pumping pipeline 20 and the middle pumping pipeline 19 are equipped with pneumatic valve III46. By staged pumping and flow rate regulation, the expansion path and enthalpy drop distribution of the gas in the expander are changed, thereby precisely controlling the temperature of the expanded gas.

[0039] Further, as a preferred embodiment of the present invention, the bottom of the crude argon tower I27 is refluxed to the upper tower 12, the top output of the crude argon tower I27 is connected to the crude argon tower II28, the lower output of the crude argon tower I27 is connected to the high-purity oxygen tower 6, the top of the crude argon tower II28 is refluxed to the upper tower 12, liquid air is fed into the crude argon tower II28 after passing through the liquid air-liquid nitrogen subcooler 5, a crude argon condenser 47 is provided on the crude argon tower II28, the output of the crude argon condenser 47 reaches the middle of the refined argon tower 29, a refined argon condenser 48 and a refined argon evaporator 49 are provided on the refined argon tower 29, the top of the refined argon tower 29 is refluxed to the upper tower 12, the output of the pressure nitrogen pipeline 21 is connected to the refined argon evaporator 49, the output of the refined argon evaporator 49 is refluxed to the upper tower 12, and a liquid argon pipeline 50 is provided at the bottom output of the refined argon tower 29.

[0040] In this embodiment, the bottom reflux connection of the crude argon column I27 is connected to the upper column 12. The oxygen component of the crude argon column I27 returns to the upper column 12 and can participate in the rectification of the upper column 12. By adjusting the bottom reflux liquid volume, the rectification conditions in the crude argon column I27 can be flexibly controlled. The material output from the bottom of the crude argon column I27 contains a certain amount of oxygen and other components such as argon. This part of the material is introduced into the high-purity oxygen column 6. The high-purity oxygen column 6 can further purify the oxygen in it through its own rectification and evaporation operations. The top reflux connection of the crude argon column II28 is connected to... Connected to column 12, it can serve as reflux liquid for the rectification of column 12, participating in the rectification process. Simultaneously, it achieves a rational distribution of cooling capacity. The liquid air, after passing through the liquid air-liquid nitrogen subcooler 5, has its temperature further reduced. At this point, it is fed into crude argon column II28 as a cold source, promoting the rectification process within II28. The output from crude argon condenser 48 reaches the middle of the refined argon column 39. Under the mass and heat transfer of rising vapor and descending liquid within the refined argon column 39, nitrogen, with a lower boiling point than argon, gradually evaporates from the liquid phase. The rising vapor moves upwards, while argon gradually accumulates at the bottom of the column. The top of the argon refining column 29 is connected to the upper column 12 via reflux. The liquid refluxed to the upper column 12 can participate in the rectification process of the upper column 12, realizing the recycling of materials. At the same time, the cooling capacity it carries can also supplement the cooling capacity consumed in the rectification process of the upper column 12, improving the energy efficiency of the entire unit. The output of the pressure nitrogen pipeline 21 is connected to the argon refining evaporator 49. The output of the argon refining evaporator 49 is refluxed to the upper column 12, providing a heat source for the argon refining column 29. Inside the argon refining evaporator 49, nitrogen is cooled by liquid argon. Liquid nitrogen is condensed, while liquid argon absorbs heat and evaporates into argon gas, which is then used as the rising gas in distillation column 4 to participate in distillation. The liquid nitrogen output from the argon evaporator 49 is returned to the upper column 12. On the one hand, this realizes the circulation of materials, as the liquid nitrogen returning to the upper column 12 can participate in the distillation process of the upper column, which helps to improve the distillation efficiency of the upper column 12. On the other hand, this process is also an energy exchange process, using the heat of pressurized nitrogen gas to evaporate liquid argon, realizing the rational use of energy and reducing additional energy consumption. The liquid argon pipeline 50 can obtain high-purity liquid argon products.

[0041] As a further preferred embodiment of the present invention, the crude argon tower II28 is provided with a reflux liquid path 51, which is pressurized by a circulating pressure pump 52 and enters the crude argon tower I27.

[0042] In this embodiment, the reflux through the reflux liquid path 51 can increase the recovered cold capacity of the upper column 12, and the circulating pressure pump 52 plays a role in circulating pressurization.

[0043] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0044] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multifunctional air separation unit that uses a liquid oxygen self-pressurized evaporator to liquefy air and nitrogen, and liquid nitrogen backflow to produce liquid oxygen, characterized in that: It includes an air filtration and compression system, a precooling system, an air purification unit, a main heat exchanger, a liquid oxygen evaporator, a low-pressure expander, a distillation column, a liquid air and liquid nitrogen subcooler, a high-purity oxygen tower, an argon extraction system, a medium-pressure nitrogen pipeline network, a liquid oxygen pipeline network, a nitrogen liquefaction unit, heat exchanger I, and a gas-liquid separator; The air filtration and compression system, precooling system, and air purification unit are connected in sequence. The distillation column includes an upper column, a lower column, and a main condenser-evaporator. The air purification unit outputs an air pipeline. The air pipeline reaches the lower column after heat exchange in the main heat exchanger. The air pipeline outputs a liquid oxygen evaporator. The liquid oxygen evaporator outputs liquid air to the lower and upper columns. Liquid oxygen is output from the bottom of the upper column and enters the liquid oxygen evaporator. The liquid oxygen evaporator outputs a pressurized oxygen pipeline. The pressurized oxygen is output and stored after heat exchange in the main heat exchanger. The bottom of the liquid oxygen evaporator outputs a product liquid oxygen pipeline. The bottom of the upper column has an atmospheric pressure product oxygen pipeline. The atmospheric pressure product oxygen is output and stored via the main heat exchanger. The air pipeline output connects to a low-pressure expander. The inlet pipeline of the low-pressure expander has a central extraction pipeline and a bottom extraction pipeline respectively installed within the main heat exchanger. After expansion, the air from the low-pressure expander enters the upper column. After preliminary distillation in the lower column, oxygen-enriched liquid air is obtained at the bottom. The top of the lower column is equipped with a pressurized nitrogen pipeline and a pure liquid nitrogen pipeline. The pressurized nitrogen pipeline is discharged and stored after heat exchange in the main heat exchanger. The oxygen-enriched liquid air and pure liquid nitrogen pipelines are discharged and enter the upper column via a liquid air-liquid nitrogen subcooler. The pure oxygen tower is equipped with a high-purity oxygen tower evaporator. The output of the pressure nitrogen pipeline is connected to the high-purity oxygen tower evaporator. The output of the high-purity oxygen tower evaporator is connected to the upper tower. Oxygen obtained at the top of the high-purity oxygen tower is sent back to the lower part of the lower tower. The bottom of the high-purity oxygen tower is equipped with a product high-purity liquid oxygen pipeline. The middle part of the upper tower is connected to the argon extraction system. The lower tower is equipped with a replenishing liquid nitrogen pipeline. The top of the upper tower is equipped with a low-pressure nitrogen pipeline. The low-pressure nitrogen pipeline is output and stored after passing through a liquid air-liquid nitrogen subcooler and a main heat exchanger. The argon extraction system includes a crude argon tower I, a crude argon tower II, and a refined argon tower connected in sequence, with the middle of the upper tower connected to the crude argon tower I; The medium-pressure nitrogen pipeline is output to the nitrogen liquefaction unit via heat exchanger I. The liquid oxygen pipeline is connected to the nitrogen liquefaction unit. The nitrogen liquefaction unit is connected to the gas-liquid separator. The medium-pressure nitrogen from the medium-pressure nitrogen pipeline and the oxygen from the nitrogen liquefaction unit exchange heat through heat exchanger I and are liquefied and output through the nitrogen liquefaction unit. The output of the gas-liquid separator is then connected to the low-pressure nitrogen pipeline. The liquid oxygen from the liquid oxygen pipeline exchanges heat with the nitrogen entering the nitrogen liquefaction unit and is vaporized. It then exchanges heat with the medium-pressure nitrogen from the medium-pressure nitrogen pipeline in heat exchanger I and is output and stored.

2. The multifunctional air separation unit according to claim 1, which uses a liquid oxygen self-pressurized evaporator to liquefy air and nitrogen and liquid nitrogen backflow to produce liquid oxygen, is characterized in that: The air filtration and compression system includes a self-cleaning air filter and an air turbine compressor. The self-cleaning air filter is connected to the air turbine compressor. The output of the air turbine compressor is connected to the precooling system. The output of the air turbine compressor is provided with a circulating heat exchange path. The top output of the argon tower is provided with a circulating pipeline. The circulating pipeline reaches the air purification unit after passing through a liquid air-liquid nitrogen subcooler and a main heat exchanger. A heat exchanger II is provided between the circulating pipeline and the circulating heat exchange path.

3. A multifunctional air separation unit according to claim 1, which uses a liquid oxygen self-pressurized evaporator to liquefy air and nitrogen and liquid nitrogen backflow to produce liquid oxygen, is characterized in that: The air purification unit includes a molecular sieve adsorber I and a molecular sieve adsorber II. Molecular sieve adsorber I and molecular sieve adsorber II are connected together, and an electric heater and a silencer are respectively connected to molecular sieve adsorber I and molecular sieve adsorber II.

4. A multifunctional air separation unit according to claim 1, which uses a liquid oxygen self-pressurized evaporator to liquefy air and nitrogen and liquid nitrogen backflow to produce liquid oxygen, is characterized in that: Pneumatic valves I are installed on the pipelines that supply the liquid oxygen evaporator to the lower and upper towers, respectively.

5. A multifunctional air separation unit according to claim 1, which uses a liquid oxygen self-pressurized evaporator to liquefy air and nitrogen and liquid nitrogen backflow to produce liquid oxygen, is characterized in that: The low-pressure expander is connected to a booster compressor, the air pipeline output is connected to the booster compressor, the booster compressor is connected to a cooler, and the cooler output goes to the low-pressure expander after passing through the main heat exchanger.

6. A multifunctional air separation unit according to claim 1, which uses a liquid oxygen self-pressurized evaporator to liquefy air and nitrogen and liquid nitrogen backflow to produce liquid oxygen, is characterized in that: The upper part of the upper tower is equipped with a waste nitrogen pipeline. After being reheated by the liquid air-liquid nitrogen subcooler and the main heat exchanger, the waste nitrogen pipeline enters the air purification unit and the precooling system respectively.

7. A multifunctional air separation unit according to claim 1, which uses a liquid oxygen self-pressurized evaporator to liquefy air and nitrogen and liquid nitrogen backflow to produce liquid oxygen, is characterized in that: The atmospheric pressure product oxygen pipeline output is connected to the pressure oxygen pipeline, and a pneumatic valve II is installed on the pipeline between the atmospheric pressure product oxygen pipeline and the pressure oxygen pipeline.

8. A multifunctional air separation unit according to claim 1, which uses a liquid oxygen self-pressurized evaporator to liquefy air and nitrogen and liquid nitrogen backflow to produce liquid oxygen, is characterized in that: A pneumatic valve III is installed on the bottom extraction pipeline.

9. A multifunctional air separation unit according to claim 1, which uses a liquid oxygen self-pressurized evaporator to liquefy air and nitrogen and liquid nitrogen backflow to produce liquid oxygen, characterized in that: The bottom of the crude argon tower I is connected to the upper tower via reflux. The top output of the crude argon tower I is connected to the crude argon tower II. The lower output of the crude argon tower I is connected to the high-purity oxygen tower. The top of the crude argon tower II is connected to the upper tower via reflux. Liquid air is fed into the crude argon tower II after passing through a liquid air-liquid nitrogen subcooler. A crude argon condenser is installed on the crude argon tower II. The output of the crude argon condenser reaches the middle of the refined argon tower. A refined argon condenser and a refined argon evaporator are installed on the refined argon tower. The top of the refined argon tower is connected to the upper tower via reflux. The output of the pressurized nitrogen pipeline is connected to the refined argon evaporator. The output of the refined argon evaporator is refluxed back to the upper tower. A liquid argon pipeline is installed at the bottom output of the refined argon tower.

10. A multifunctional air separation unit according to claim 1, which uses a liquid oxygen self-pressurized evaporator to liquefy air and nitrogen and liquid nitrogen backflow to produce liquid oxygen, characterized in that: The crude argon tower II is equipped with a reflux liquid path, which is pressurized by a circulating pump and enters the crude argon tower I.

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