System for preparing ultrapure nitrogen and ultrapure oxygen through air separation

Abstract

The utility model provides a system for preparing ultra-pure nitrogen and ultra-pure oxygen through air separation, relates to the technical field of air separation, and solves the technical problems that the existing nitrogen purification process for preparing high-purity gas through air separation is relatively tedious in steps and relatively low in yield. The device comprises an air filtration system, an air compression system, an air precooling system and an air purification system, and further comprises an air rectification system used for rectifying gas, the air rectification system comprises a lower tower used for carrying out primary rectification, an upper tower used for carrying out secondary rectification and an ultra-pure nitrogen tower communicated with the lower tower and the upper tower, and the ultra-pure nitrogen tower is provided with an ultra-pure nitrogen evaporator for evaporating liquid nitrogen discharged from the top of the lower tower and an ultra-pure nitrogen condenser for condensing and evaporating nitrogen. According to the multi-stage rectification device, the purity of nitrogen and oxygen can be effectively improved through a multi-stage rectification process, including serial use of the lower tower, the upper tower and the ultra-pure nitrogen tower.

Description

Technical Field

[0001] The utility model relates to the technical field of air separation, and in particular, to a system for preparing ultra-pure nitrogen and ultra-pure oxygen by air separation. Background Technique

[0002] Air separation technology is a common method for industrially preparing high-purity gases (such as ultra-pure nitrogen and ultra-pure oxygen). This technology is mainly based on the different boiling points of the components in air for separation. The basic principle of air separation is to use the cryogenic distillation method, that is, after liquefying air, it is separated in a distillation column according to the boiling point differences of the gas components. The boiling point of nitrogen is -195.8 °C, while the boiling point of oxygen is -183 °C, so the separation of the two can be achieved by adjusting the distillation temperature.

[0003] First, it is necessary to purify the air to remove moisture, carbon dioxide and other impurities, and then liquefy it by compression and cooling. In this process, equipment such as expanders and heat exchangers are usually used to lower the temperature of the air and increase its pressure. The liquefied air is introduced into the distillation column. Multiple trays or packings are arranged at different heights in the column. As the liquid rises and the vapor descends in the column, components with different boiling points are gradually separated. High-purity nitrogen is obtained at the top of the column, while relatively pure oxygen is collected at the bottom of the column. To obtain higher-purity nitrogen or oxygen, further purification steps are required. For example, an adsorbent bed can be used to remove residual moisture and other impurities, or membrane separation technology can be used to further improve the purity.

[0004] For example, a device and method for simultaneously producing oxygen-rich gas and high-purity nitrogen with low energy consumption proposed in the patent with the publication number CN106989567A includes an air compression system, an air precooling system, a molecular sieve purification system, a turbo-expander, a main heat exchanger, a distillation column and a subcooler. While producing high-purity nitrogen, it can also produce oxygen-rich gases with different purities, which can be directly used for subsequent production, reducing the duplication of equipment construction and investment and lowering the production cost. The device finally obtains nitrogen with a relatively high purity in the upper column after distillation separation, but its nitrogen purification process steps are relatively cumbersome and the yield is low. Summary of the Utility Model

[0005] The purpose of the utility model is to provide a system for preparing ultra-pure nitrogen and ultra-pure oxygen by air separation, so as to solve the technical problems that the nitrogen purification process steps of the existing air separation for preparing high-purity gas are relatively cumbersome and the yield is low.

[0006] The embodiments of the utility model are realized by the following technical solutions:

[0007] A system for preparing ultra-pure nitrogen and ultra-pure oxygen by air separation, comprising an air filtration system, an air compression system, an air precooling system and an air purification system, and further comprising an air rectification system for rectifying gases. The air rectification system includes a lower column for performing the first rectification, an upper column for performing the secondary rectification, and an ultra-pure nitrogen column connecting the lower column and the upper column. The ultra-pure nitrogen column is provided with an ultra-pure nitrogen evaporator for evaporating the liquid nitrogen discharged from the top of the lower column and an ultra-pure nitrogen condenser for condensing the evaporated nitrogen.

[0008] Preferably, it further includes a high-purity oxygen column for further rectifying the oxygen at the bottom of the upper column. The high-purity oxygen column includes an ultra-pure oxygen condenser for condensing the ascending gas and a high-purity oxygen evaporator for evaporating the high-purity oxygen. The ultra-pure oxygen evaporator is connected to the lower column to use part of the nitrogen as a heat source to heat the oxygen, and is connected to the upper column to recover the heated liquid nitrogen.

[0009] Preferably, the ultra-pure nitrogen column is further provided with a throttling pipeline for throttling part of the condensed liquid nitrogen to the upper column.

[0010] Preferably, the lower column is further provided with a first reflux pipeline for refluxing the liquid nitrogen discharged from the top to the upper column and a second reflux pipeline for refluxing the oxygen-rich liquid air discharged from the bottom to the upper column. The first reflux pipeline is further provided with a connecting pipe for connecting to the ultra-pure nitrogen column.

[0011] Preferably, the air rectification system further includes a main condenser-evaporator connecting the upper column and the lower column for condensing the nitrogen at the top of the lower column and partially feeding it into the upper column.

[0012] Preferably, the air rectification system further includes a residue evaporator connecting the lower column and the ultra-pure nitrogen column for treating the residue liquid.

[0013] Preferably, the air filtration system includes air filters of several stages for filtering dust and mechanical impurities. The air compression system includes a centrifugal air compressor for compressing air to 0.57 Mpa.

[0014] Preferably, the air precooling system includes an air cooling tower for cooling the high-temperature compressed air and a circulating cooling water system for supplying cooling to the air cooling tower. The circulating cooling water system includes a cooling water filter for filtering the cooling water and a cooling water pump for supplying the cooling water.

[0015] Preferably, the air purification system includes a first adsorber and a second adsorber for adsorbing and removing moisture and carbon dioxide. The first adsorber and the second adsorber are respectively provided with a first heater and a second heater for regenerating them.

[0016] Preferably, the air purification system further includes a nitrogen vent silencer for venting the contaminated nitrogen from the first heater and the second heater.

[0017] Preferably, the cold energy of the above device is mainly provided by the turboexpander system. The nitrogen reheated by the main heat exchanger is combined with the nitrogen supplemented by the nitrogen feeder and then enters the circulating nitrogen compressor for boosting. After boosting, it is divided into two parts: one part directly enters the main heat exchanger, is cooled to about -7°C in the main heat exchanger, and then is drawn out and sent to the expansion end of the thermal expander for expansion refrigeration. After expansion, the gas returns to the main heat exchanger for reheating and then returns to the inlet of the circulating nitrogen compressor; the other part first enters the boosting ends of the thermal and cold turboexpanders in series for boosting, then enters the main heat exchanger. A small part is liquefied and drawn out from the cold end of the main heat exchanger and sent to the lower column to participate in rectification. The rest is cooled to about -95°C in the main heat exchanger and then drawn out and sent to the expansion end of the cold expander for expansion refrigeration. After expansion, the gas returns to the main heat exchanger for reheating and then returns to the inlet of the circulating nitrogen compressor.

[0018] With this technical solution, through a multi-stage rectification process, including the series use of the lower column, the upper column, and the ultra-pure nitrogen column, the system can effectively improve the purity of nitrogen and oxygen and produce ultra-pure nitrogen and ultra-pure oxygen. The system design includes special equipment such as ultra-pure nitrogen evaporators and condensers, as well as reflux pipes and residual liquid evaporators. These designs help optimize the entire process flow and improve the separation efficiency. By setting up throttle pipes and reflux pipes, the system can make full use of existing resources, such as throttling the condensed liquid nitrogen to the required column and refluxing the liquid nitrogen in the lower column and oxygen-rich liquid air to the upper column, thereby improving the utilization rate of raw materials. The system reduces additional energy consumption through effective heat management and material circulation, such as recovering heat through the main condenser-evaporator and treating residual liquid through the residual liquid evaporator to reduce energy waste. The entire system integrates multiple links such as air filtration, compression, precooling, purification, and rectification, which is convenient for operation and management, and at the same time ensures the continuity and stability of the entire production process. The system design allows adjustment according to different production requirements. For example, by adjusting the operation of the reflux pipe and the throttle pipe, it can adapt to different production scales and purity requirements. Through an efficient separation and purification process, the generation of harmful by-products is reduced. At the same time, the system design considers the recycling of cooling water, reducing the impact on the environment;

[0019] In the high-purity oxygen column, the oxygen purity is ≥99.9999%, and at the top of the upper column, the liquid oxygen purity is ≥99.6%. Different purity oxygen products can be obtained according to the specific production plan requirements, improving production flexibility.

[0020] The technical solution of the embodiment of the present utility model has at least the following advantages and beneficial effects:

[0021] 1. The utility model can effectively improve the purity of nitrogen and oxygen through a multi-stage rectification process, including the series use of a lower column, an upper column, and an ultra-pure nitrogen column.

[0022] 2. Through effective thermal management and material recycling, the utility model reduces additional energy consumption. For example, heat is recovered through the main condenser-evaporator, and residual liquid is treated through the residual liquid evaporator to reduce energy waste.

[0023] 3. The utility model allows adjustment according to different production requirements. For example, by adjusting the operation of the reflux pipeline and the throttle pipeline, it can adapt to different production scales and purity requirements. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present utility model, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a schematic diagram of the overall structure of a system for air separation to prepare ultra-pure nitrogen and ultra-pure oxygen provided in Embodiment 1 of the present utility model.

[0026] Figure 2 It is a schematic diagram of the air rectification system structure of a system for air separation to prepare ultra-pure nitrogen and ultra-pure oxygen provided in Embodiment 1 of the present utility model.

[0027] Figure 3 It is a schematic diagram of the air filtration system and the air filtration system structure of a system for air separation to prepare ultra-pure nitrogen and ultra-pure oxygen provided in Embodiment 2 of the present utility model.

[0028] Figure 4 It is a schematic diagram of the air precooling system structure of a system for air separation to prepare ultra-pure nitrogen and ultra-pure oxygen provided in Embodiment 2 of the present utility model.

[0029] Figure 5 It is a schematic diagram of the air purification system structure of a system for air separation to prepare ultra-pure nitrogen and ultra-pure oxygen provided in Embodiment 2 of the present utility model.

[0030] Icons: 1. Air filtration system; 2. Air compression system; 3. Air precooling system; 4. Air purification system; 5. Air rectification system; 51. Lower column; 52. Upper column; 53. Ultra-pure nitrogen column; 54. Main condenser-evaporator; 55. Ultra-pure nitrogen condenser; 56. Ultra-pure nitrogen evaporator; 57. Residual liquid evaporator; 411. First adsorber; 412. Second adsorber; 421. First heater; 422. Second heater; 43. Waste nitrogen vent silencer; 31. Air cooling tower; 32. Cooling water pump; 33. Cooling water filter. Detailed implementation manners

[0031] To make the objectives, technical solutions and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are some but not all of the embodiments of the present utility model. Usually, the components of the embodiments of the present utility model described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present utility model provided in the accompanying drawings is not intended to limit the scope of the claimed present utility model, but merely represents the selected embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0033] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0034] In the description of the present utility model, it should be noted that if terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship when the product of this application is usually placed. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present utility model.

[0035] In the description of the present utility model, it should also be noted that unless otherwise clearly specified and defined, if the terms "set", "installed", "connected", and "connected" appear, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific situations.

[0036] Embodiment 1

[0037] A system for preparing ultra-pure nitrogen and ultra-pure oxygen by air separation includes an air filtration system 1, an air compression system 2, an air precooling system 3, and an air purification system 4. It also includes an air rectification system 5 for rectifying gases. The air rectification system 5 includes a lower column 51 for the first rectification, an upper column 52 for the second rectification, and an ultra-pure nitrogen column 53 connecting the lower column 51 and the upper column 52. The ultra-pure nitrogen column 53 is provided with an ultra-pure nitrogen evaporator 56 for evaporating the liquid nitrogen discharged from the top of the lower column 51 and an ultra-pure nitrogen condenser 55 for condensing the evaporated nitrogen.

[0038] In this embodiment, the ultra-pure nitrogen column 53 is also provided with a throttling pipeline for throttling a part of the condensed liquid nitrogen to the upper column 52.

[0039] In this embodiment, the lower column 51 is also provided with a first reflux pipeline for refluxing the liquid nitrogen discharged from the top to the upper column 52 and a second reflux pipeline for refluxing the oxygen-rich liquid air discharged from the bottom to the upper column 52. The first reflux pipeline is also provided with a connecting pipe for connecting to the ultra-pure nitrogen column 53.

[0040] In this embodiment, the air rectification system 5 further includes a main condenser-evaporator 54 connecting the upper column 52 and the lower column 51 for condensing the nitrogen at the top of the lower column 51 and partially sending it to the upper column 52.

[0041] In this embodiment, the air rectification system 5 further includes a residual liquid evaporator 57 connecting the lower column 51 and the ultra-pure nitrogen column 53 for treating the residual liquid.

[0042] Working principle and technical solution:

[0043] Through a multi-stage rectification process, including the serial use of a lower column 51, an upper column 52, and an ultra-pure nitrogen column 53, the system can effectively improve the purity of nitrogen and oxygen, and produce ultra-pure nitrogen and ultra-pure oxygen. The system design includes dedicated equipment such as an ultra-pure nitrogen evaporator 56 and a condenser, as well as reflux pipelines and a residue evaporator 57. These designs help optimize the entire technological process and improve the separation efficiency. By setting up throttle pipelines and reflux pipelines, the system can make full use of existing resources, such as throttling condensed liquid nitrogen to the required column, and refluxing the liquid nitrogen and oxygen-rich liquid air in the lower column 51 to the upper column 52, thereby improving the utilization rate of raw materials. Through effective thermal management and material circulation, the system reduces additional energy consumption, such as recovering heat through the main condenser-evaporator 54 and treating residues through the residue evaporator 57 to reduce energy waste.

[0044] Embodiment 2

[0045] The difference between this embodiment and Embodiment 1 is only that, in this embodiment, the air filtration system 1 includes several stages of air filters for filtering dust and mechanical impurities; the air compression system 2 includes a centrifugal air compressor for compressing and pressurizing air to 0.57 Mpa.

[0046] In this embodiment, the air pre-cooling system 3 includes an air cooling tower 31 for cooling the high-temperature compressed air and a circulating cooling water system for supplying cooling to the air cooling tower 31. The circulating cooling water system includes a cooling water filter 33 for filtering cooling water and a cooling water pump 32 for supplying cooling water.

[0047] In this embodiment, the air pre-cooling system further includes a buffer tank 34 for preventing gas pollution.

[0048] In this embodiment, the air purification system 4 includes a first adsorber 411 and a second adsorber 412 for adsorbing and removing moisture and carbon dioxide. The first adsorber 411 and the second adsorber 412 are also respectively provided with a first heater 421 and a second heater 422 for regenerating them.

[0049] In this embodiment, the air purification system 4 further includes a waste nitrogen vent silencer 43 for venting waste nitrogen from the first heater 421 and the second heater 422.

[0050] The above are only the preferred embodiments of the present utility model and are not used to limit the present utility model. For those skilled in the art, the present utility model can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A system for preparing ultra-pure nitrogen and ultra-pure oxygen by air separation, comprising an air filtration system (1), an air compression system (2), an air precooling system (3) and an air purification system (4), characterized in that: It further includes an air rectification system (5) for rectifying gas. The air rectification system (5) includes a lower column (51) for the first rectification, an upper column (52) for the secondary rectification, and an ultra-pure nitrogen column (53) connecting the lower column (51) and the upper column (52). The ultra-pure nitrogen column (53) is provided with an ultra-pure nitrogen evaporator (56) for evaporating the liquid nitrogen discharged from the top of the lower column (51) and an ultra-pure nitrogen condenser (55) for condensing the evaporated nitrogen.

2. The system for preparing ultra-pure nitrogen and ultra-pure oxygen by air separation according to claim 1, wherein: It further includes a high-purity oxygen column (7) for further rectifying the oxygen at the bottom of the upper column (52). The high-purity oxygen column (7) includes an ultra-pure oxygen condenser (71) for condensing the rising gas and a high-purity oxygen evaporator (72) for evaporating high-purity oxygen. The high-purity oxygen evaporator (72) is connected to the lower column (51) to use part of the nitrogen as a heat source to heat the oxygen, and is connected to the upper column (52) to recover the heated liquid nitrogen.

3. The system for preparing ultra-pure nitrogen and ultra-pure oxygen by air separation according to claim 1, wherein: The ultra-pure nitrogen column (53) is further provided with a throttling pipeline for throttling part of the condensed liquid nitrogen to the upper column (52).

4. A system for preparing ultra-pure nitrogen and ultra-pure oxygen by air separation according to any one of claims 1-3, characterized in that: The lower column (51) is further provided with a first reflux pipeline for refluxing the liquid nitrogen discharged from the top to the upper column (52) and a second reflux pipeline for refluxing the oxygen-rich liquid air discharged from the bottom to the upper column (52). The first reflux pipeline is also provided with a connecting pipe for connecting to the ultra-pure nitrogen column (53).

5. A system for preparing ultra-pure nitrogen and ultra-pure oxygen by air separation according to any one of claims 1-3, characterized in that: The air rectification system (5) further includes a main condenser-evaporator (54) connecting the upper column (52) and the lower column (51) for condensing the nitrogen at the top of the lower column (51) and partially feeding it into the upper column (52).

6. A system for preparing ultra-pure nitrogen and ultra-pure oxygen by air separation according to any one of claims 1-3, characterized in that: The air rectification system (5) further includes a residual liquid evaporator (57) connecting the lower column (51) and the ultra-pure nitrogen column (53) for treating the residual liquid.

7. A system for preparing ultra-pure nitrogen and ultra-pure oxygen by air separation according to any one of claims 1-3, characterized in that: The air filtration system (1) includes air filters of several stages for filtering dust and mechanical impurities. The air compression system (2) includes a centrifugal air compressor for compressing air to 0.57 Mpa.

8. A system for preparing ultra-pure nitrogen and ultra-pure oxygen by air separation according to any one of claims 1-3, characterized in that: The air pre-cooling system (3) includes an air cooling tower (31) for cooling the high-temperature compressed air and a circulating cooling water system for supplying cooling to the air cooling tower (31). The circulating cooling water system includes a cooling water filter (33) for filtering the cooling water and a cooling water pump (32) for supplying the cooling water.

9. A system for preparing ultra-pure nitrogen and ultra-pure oxygen by air separation according to any one of claims 1-3, characterized in that: The air purification system (4) includes a first adsorber (411) and a second adsorber (412) for adsorbing and removing moisture and carbon dioxide. The first adsorber (411) and the second adsorber (412) are respectively provided with a first heater (421) and a second heater (422) for regenerating them.

10. The system for preparing ultra-pure nitrogen and ultra-pure oxygen by air separation according to claim 9, wherein: The air purification system (4) further includes a waste nitrogen vent silencer (43) for venting waste nitrogen from the first heater (421) and the second heater (422).

Images