Neon-helium recovery system for air separation plant

Abstract

This utility model relates to the field of air separation and discloses a neon-helium recovery system for an air separation unit. The system includes a non-condensable gas discharge port on both the main condenser-evaporator and the fine argon evaporator. The distillation column has a feed inlet, a reflux inlet, a bottom liquid phase outlet, and a top gas phase outlet. The condensation equipment has a condensation-side inlet, a condensation-side non-condensable gas outlet, a cold source inlet, and a cold source outlet. Both non-condensable gas discharge ports are connected to the feed inlet, the reflux inlet is connected to the condensation-side liquid phase outlet, and the top gas phase outlet is connected to the condensation-side inlet. The neon-helium feed gas discharged from the non-condensable gas discharge ports of the main condenser-evaporator and the fine argon evaporator enters the condensation equipment via the distillation column and is finally discharged as crude neon-helium product from the condensation-side non-condensable gas outlet, thus achieving neon-helium recovery from the air. This system, through the collection of multiple neon-helium recovery pipelines, significantly improves the extraction rate of neon-helium and prevents neon-helium from entering other products.

Description

Technical Field

[0001] This utility model relates to the field of air separation, specifically to a neon-helium recovery system for air separation units. Background Technology

[0002] An air separation unit is a device that uses air as raw material, transforms it into a liquid state through compression and deep freezing, and then separates the liquid air into components through distillation to produce gases such as oxygen, nitrogen, and argon. It is widely used in traditional metallurgy and chemical industries. Air distillation utilizes the different volatility of the various components of air—that is, the different vapor pressures of each component at the same temperature—by subjecting the liquid air to multiple partial evaporations and condensations, thereby achieving the separation of the components.

[0003] The main condenser-evaporator of the air separation unit is used for the separation of oxygen and nitrogen. However, neon and helium have extremely low boiling points, much lower than those of nitrogen and oxygen, and cannot be condensed at the main condenser temperature, thus accumulating as non-condensable gases. Since neon and helium also have industrial value, they need to be extracted as well. However, the current conventional operation is to directly release this portion of non-condensable gases into the atmosphere. Even if some air separation units add a neon-helium recovery system, they still use a single feedstock import, resulting in a low neon-helium extraction rate. Utility Model Content

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a neon-helium recovery system for air separation units. By collecting through multiple neon-helium recovery pipelines, the system maximizes the recovery of neon-helium from the air and prevents neon-helium from entering other products.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is as follows: a neon-helium recovery system for an air separation unit, comprising a main condenser-evaporator, a lower column, a fine argon evaporator, a distillation column, and a condensation device. The main condenser-evaporator is provided with a non-condensable gas discharge port one, the lower column is provided with a reflux inlet, the fine argon evaporator is provided with a non-condensable gas discharge port two, the distillation column is provided with a feed inlet, a reflux inlet, a bottom liquid phase outlet, and a top gas phase outlet, and the condensation device is provided with a condensation-side inlet, a condensation-side non-condensable gas outlet, a condensation-side liquid phase outlet, a cold source inlet, and a cold source outlet. Both the first and second non-condensable gas discharge ports are connected to the feed port, the reflux port is connected to the liquid phase outlet on the condensing side, the liquid phase outlet at the bottom of the tower is connected to the reflux inlet, the gas phase outlet at the top of the tower is connected to the condensing side inlet, and the crude neon-helium product is discharged through the non-condensable gas outlet on the condensing side. The air separation unit is also equipped with a subcooled liquid nitrogen pipeline and a low-pressure nitrogen pipeline, and the cold source inlet is connected to the subcooled liquid nitrogen pipeline, and the cold source outlet is connected to the low-pressure nitrogen pipeline.

[0006] Optionally, the main condenser-evaporator is further provided with a liquid nitrogen reflux port, a separation section is provided at the liquid nitrogen reflux port, and the feed inlet of the distillation column is also connected to the separation section.

[0007] Optionally, the top of the lower tower is provided with a packing section, and the packing section is located between the gas phase rising channel of the lower tower and the gas phase inlet of the main condenser-evaporator.

[0008] Optionally, it also includes an upper tower, which has a side-line extraction port at the position corresponding to the argon enrichment zone, and the side-line extraction port is connected to the feed inlet of the fine argon evaporator.

[0009] Optionally, a crude argon extraction unit is provided between the side-line extraction port and the feed inlet.

[0010] Optionally, a liquid level sensor is provided on the outside of the distillation column, and the liquid level sensor is connected to the liquid phase outlet at the bottom of the column.

[0011] Optionally, the inner diameter of the separation section is the same as the inner diameter of the pipe at the liquid nitrogen reflux port.

[0012] Optionally, a storage tank for storing crude neon-helium products is provided on the outside of the condensation equipment, and the storage tank is connected to the non-condensable gas outlet on the condensation side.

[0013] Compared with the prior art, the beneficial effects of this utility model are as follows: (1) In this utility model, the neon-helium raw material gas discharged from the non-condensable gas discharge port of the main condenser evaporator and the fine argon evaporator is distilled by the distillation tower and then enters the condensation equipment. Finally, the crude neon-helium product is discharged from the non-condensable gas outlet on the condensation side, thereby realizing the recovery of neon-helium in the air. This system significantly improves the extraction rate of neon-helium through the collection of multiple neon-helium recovery pipelines and avoids neon-helium entering other products. (2) In this utility model, the liquid nitrogen condensed by the main condenser evaporator can be returned to the lower tower or the external distillation tower through the liquid nitrogen return port as a cold source. A separation section is set at the liquid nitrogen return port to separate the trace amounts of neon and helium entrained in the liquid nitrogen again, thereby improving the neon and helium recovery rate. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the neon-helium recovery system for an air separation unit in an embodiment of this utility model; Among them, 1. Main condenser-evaporator; 101. Non-condensable gas discharge port 1; 102. Liquid nitrogen reflux port; 2. Upper tower; 201. Side line opening; 3. Lower tower; 301. Reflux inlet; 302. Packing section; 4. Argon evaporator; 401. Feed inlet; 402. Non-condensable gas discharge port 2; 5. Condensation equipment; 501. Condensation side inlet; 502. Condensation side liquid phase outlet; 503. Condensation side non-condensable gas outlet; 504. Cold source inlet; 505. Cold source outlet; 6. Distillation column; 601. Feed inlet; 602. Reflux inlet; 603. Top vapor outlet; 604. Bottom liquid outlet; 7. Crude argon extraction unit. Detailed Implementation

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. These drawings are simplified schematic diagrams, which are only used to illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0016] Example 1, as Figure 1 As shown, a neon-helium recovery system for an air separation unit includes a main condenser-evaporator 1, an upper column 2, a lower column 3, a fine argon evaporator 4, a distillation column 6, and a condensation device 5. The main condenser-evaporator 1 and the fine argon evaporator 4 discharge non-condensable gases containing neon and helium. The non-condensable gases containing neon and helium are separated by passing through the distillation column 6 and the condensation device 5 in sequence to generate crude neon-helium products.

[0017] The non-condensable gas discharge port 101 on the main condenser evaporator 1 and the non-condensable gas discharge port 402 on the refined argon evaporator 4 are both connected to the feed port 601 of the distillation column 6. The top gas phase outlet 603 of the distillation column 6 is connected to the condensation side inlet 501 of the condensation equipment 5. The condensation side non-condensable gas outlet 503 of the condensation equipment 5 is the crude neon-helium product outlet, that is, the crude neon-helium product is discharged through the condensation side non-condensable gas outlet 503. The condensation side liquid phase outlet 502 of the condensation equipment 5 is connected to the reflux port 602 of the distillation column 6. The bottom liquid phase outlet 604 of the distillation column 6 is connected to the reflux inlet 301 of the lower column 3. The subcooled liquid nitrogen pipeline of the air separation unit is connected to the cold source inlet 504 of the condensation equipment 5. The cold source outlet 505 of the condensation equipment 5 is connected to the low-pressure nitrogen pipeline of the air separation unit.

[0018] Specifically, the neon-helium feedstock gas is collected from multiple recovery pipelines, such as the non-condensable gas discharged from the main condenser evaporator 1 and the fine argon evaporator 4, to maximize the recovery of neon-helium from the air. After being refined by the distillation column 6, the neon-helium feedstock gas enters the condensation equipment 5, and finally the crude neon-helium product is discharged from the non-condensable gas outlet on the condensation side, thereby realizing the recovery of neon-helium from the air and improving the extraction rate of crude neon-helium.

[0019] As described above, the main condenser-evaporator 1 is installed between the lower part of the upper tower 2 and the upper part of the lower tower 3. Its shell is connected to the bottom of the upper tower 2 and the top of the lower tower 3. The gaseous nitrogen (high pressure) at the top of the lower tower 3 enters the nitrogen-side channel of the main condenser-evaporator 1, and the liquid oxygen (low pressure) at the bottom of the upper tower 2 enters the oxygen-side channel of the main condenser-evaporator 1. After heat exchange, the liquid nitrogen flows back to the lower tower 3, and the gaseous oxygen rises to the upper tower 2, completing the circulation of materials and heat.

[0020] The subcooled liquid nitrogen pipeline is a dedicated pipeline for transporting subcooled liquid nitrogen (liquid nitrogen in a metastable state with a temperature lower than saturated liquid nitrogen). It serves as the cold source supply channel for condenser 5 in the neon-helium recovery system. Its function is to precisely deliver the subcooled liquid nitrogen from the subcooler outlet to the cold source inlet of condenser 5, providing a low-temperature cold source for the deep separation of neon, helium, and nitrogen. The low-pressure nitrogen pipeline is a pipeline for transporting low-pressure gaseous nitrogen. Its function is to recover the nitrogen evaporated on the cold source side of condenser 5, achieving material circulation.

[0021] Specifically, the raw gas from the non-condensable gas discharge port 101 of the main condenser evaporator 1 and the non-condensable gas discharge port 402 of the refined argon evaporator 4 enters the distillation column 6 through the feed port 601. After distillation, the crude neon-helium non-condensable gas enters the condensation side of the condenser 5 from the top gas phase outlet 603. Under the action of the condenser 5, the nitrogen is condensed into liquid nitrogen. The liquid nitrogen is returned to the distillation column 6 as reflux liquid from the condenser liquid phase outlet and reflux port 602. The liquid nitrogen generated at the bottom of the distillation column 6 is returned to the lower column 3 of the air separation unit through the bottom liquid phase outlet 604.

[0022] In this process, some of the liquid nitrogen in the air separation unit is subcooled to form subcooled liquid nitrogen, which serves as the cold source for the condenser 5. It enters the condenser 5 from the cold source inlet 504, and the nitrogen gas formed after evaporation through heat exchange returns to the low-pressure nitrogen pipeline of the air separation unit through the cold source outlet 505.

[0023] Furthermore, a liquid level sensor is installed on the outside of the distillation column 6, and the liquid level sensor is connected to the liquid phase outlet 604 at the bottom of the column.

[0024] Distillation column 6 is used for the initial separation of neon, helium, and nitrogen. The liquid nitrogen accumulated at the bottom of the column needs to be partially refluxed back to the lower column 3, and partially used as the descending liquid in its own distillation. The function of the liquid level sensor is to ensure that the liquid level is maintained within the set range. If the liquid level is too low, the amount of liquid nitrogen refluxed to the lower column 3 will be insufficient, affecting the nitrogen circulation in the lower column 3. If the liquid level is too high, it will submerge the packing layer inside the column, hindering the mass transfer of the rising gas phase (nitrogen and neon / helium) and reducing the neon / helium enrichment efficiency.

[0025] In addition, a storage tank is provided on the outside of the condensing equipment 5. The storage tank is connected to the non-condensable gas outlet 503 on the condensing side. That is, the crude neon-helium product enters the storage tank through the non-condensable gas outlet 503 on the condensing side of the condensing equipment 5 and is stored in the tank.

[0026] Example 2, as Figure 1 As shown in Example 1, in the main condenser-evaporator 1, liquid nitrogen may carry trace amounts of neon and helium gas during the condensation process. Because these neon and helium gases have extremely low boiling points, they are difficult to completely dissolve in the liquid nitrogen and will be mixed in the liquid nitrogen as tiny bubbles, flowing back to the lower column 3 or the distillation column 6 with the liquid nitrogen. Therefore, a separation section for gas-liquid separation is provided in the liquid nitrogen reflux pipeline of the main condenser-evaporator 1. This separation section is located at the liquid nitrogen reflux port 102, and the feed port 601 of the distillation column 6 is also connected to the bypass of the separation section.

[0027] The baffles (or sieves) inside the separation section can change the flow direction of liquid nitrogen (such as by multiple turns). By utilizing the density difference between neon-helium bubbles and liquid nitrogen, the bubbles are detached from the liquid flow under the action of inertial force and buoyancy, and gather at the top of the separation section. The inner diameter of the separation section is usually consistent with that of the return pipeline, but the length is designed to be 3-5 times the diameter of the pipeline to provide sufficient time and space for the bubbles to rise and prevent them from being carried away by the liquid.

[0028] The collected neon and helium gas re-enters the main neon and helium recovery process (such as distillation column 6) through the gas-phase bypass at the top of the separation section, while the purified liquid nitrogen continues to flow along the reflux pipeline. This design avoids trace amounts of neon and helium flowing back to the bottom of lower column 3 or distillation column 6 with the liquid nitrogen, thus significantly improving the neon and helium recovery rate (if it enters lower column 3, it will re-enter the main reflux with the nitrogen, forming an ineffective cycle; if it enters the bottom of distillation column 6, it will be carried back to the main air separation process by the liquid nitrogen, resulting in loss). At the same time, the neon and helium content in the liquid nitrogen reflux entering distillation column 6 is reduced, which can reduce the separation load of subsequent distillation units.

[0029] Furthermore, the top of the lower tower 3 is provided with a packing section 302, which is a gas-liquid mass transfer enhancement structure (such as corrugated packing, wire mesh packing, etc.), located between the gas phase rising channel of the lower tower 3 and the gas phase inlet of the main condenser evaporator 1. Its function is to enhance the separation of nitrogen and neon-helium mixture at the top of the lower tower 3, providing a higher purity light component gas source for subsequent neon-helium recovery.

[0030] Example 3, as Figure 1 As shown, based on Examples 1 and 2, the crude argon feedstock of the fine argon evaporator 4 is derived from the argon-enriched mixed gas generated during the oxygen-nitrogen distillation process of the air separation system, and needs to be pretreated by the crude argon extraction unit 7.

[0031] Utilizing the boiling point differences of oxygen, nitrogen, and argon, preliminary separation is achieved in the upper column 2 through multi-stage gas-liquid mass transfer. Oxygen (liquid oxygen), with the highest boiling point, is enriched at the bottom of the column and evaporated as an oxygen product or participates in subsequent recycling; nitrogen (gaseous nitrogen), with the lowest boiling point, is enriched at the top of the column and discharged as a nitrogen product; argon, with a boiling point between the two, forms an argon enrichment zone in a specific area in the middle of the upper column 2.

[0032] A side-stream extraction port 201 is provided in the upper column 2 corresponding to the argon enrichment zone, and the side-stream extraction port 201 is connected to the feed inlet 401 of the fine argon evaporator 4. In order to extract argon, a side-stream extraction port 201 is opened in the argon enrichment zone of the upper column 2, and the argon enrichment mixture is extracted through a dedicated pipeline to obtain the crude argon raw material for subsequent crude argon purification.

[0033] As described above, the crude argon extraction unit 7 is located between the side line extraction port 201 and the feed inlet 401 of the fine argon evaporator 4. The argon-enriched mixed gas extracted from the side line of the upper tower 2 has too high oxygen and nitrogen impurity content, which will affect the purity of the fine argon and cannot be directly introduced into the fine argon evaporator 4. Therefore, it needs to be pretreated by denitrification and deoxygenation through the crude argon extraction unit 7 to finally obtain crude argon that meets the feed requirements of the fine argon evaporator 4. The crude argon extraction unit 7 includes a crude argon I tower and a crude argon II tower.

[0034] Nitrogen removal in crude argon I column: Argon-enriched mixed gas enters the middle and lower part of crude argon I column and comes into countercurrent contact with liquid nitrogen / liquid air refluxed from the top of the column. Nitrogen with a lower boiling point in the mixed gas is more easily vaporized and discharged with the nitrogen gas at the top of the column (returned to the upper column 2 or used as low-pressure nitrogen gas). Argon and oxygen flow downwards and form argon-rich and oxygen-rich liquid at the bottom of crude argon I column.

[0035] Deoxygenation of crude argon II column: The argon-rich and oxygen-rich liquid at the bottom of crude argon I column enters crude argon II column, and a small amount of pure hydrogen is introduced into the column at the same time. The reaction occurs in the catalytic reaction section (filled with palladium catalyst) set in the column. Hydrogen and oxygen react with the catalyst to generate water, which is removed by condensation or drying unit. The deoxygenated gas phase is further distilled at the top of crude argon II column to remove residual trace nitrogen, and finally, high-purity crude argon is obtained at the bottom of the column.

[0036] In summary, this utility model proposes a neon-helium recovery system for an air separation unit. The system involves adding a packing section 302 to the top of the lower column 3 of the air separation unit, a separation section at the liquid nitrogen reflux port 102 of the main condenser-evaporator 1, and a feed gas from the non-condensable gas discharge port of the argon evaporator 4. After distillation in the distillation column 6, the feed gas enters the condensation side of the condensation equipment 5. The crude neon-helium non-condensable gas exits the cold box as crude argon product, and the liquid nitrogen returns to the distillation column 6 as reflux liquid. The liquid nitrogen at the bottom of the distillation column 6 is refluxed back to the lower column 3 of the air separation unit. After subcooling, the liquid nitrogen in the air separation unit serves as the cold source for the condensation equipment 5, and the evaporated nitrogen returns to the low-pressure nitrogen pipeline of the air separation unit.

[0037] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0038] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0039] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0040] Based on the preferred embodiments of this utility model described above, those skilled in the art can make various changes and modifications without departing from the technical concept of this utility model. The technical scope of this utility model is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A neon-helium recovery system for an air separation unit, characterized in that: The system includes a main condenser-evaporator, a lower column, a refined argon evaporator, a distillation column, and a condensation device. The main condenser-evaporator is equipped with a non-condensable gas discharge port one, the lower column is equipped with a reflux inlet, the refined argon evaporator is equipped with a non-condensable gas discharge port two, the distillation column is equipped with a feed inlet, a reflux inlet, a bottom liquid phase outlet, and a top gas phase outlet, and the condensation device is equipped with a condensation-side inlet, a condensation-side non-condensable gas outlet, a condensation-side liquid phase outlet, a cold source inlet, and a cold source outlet. Both the first and second non-condensable gas discharge ports are connected to the feed port, the reflux port is connected to the liquid phase outlet on the condensing side, the liquid phase outlet at the bottom of the tower is connected to the reflux inlet, the gas phase outlet at the top of the tower is connected to the condensing side inlet, and the crude neon-helium product is discharged through the non-condensable gas outlet on the condensing side. The air separation unit is also equipped with a subcooled liquid nitrogen pipeline and a low-pressure nitrogen pipeline, and the cold source inlet is connected to the subcooled liquid nitrogen pipeline, and the cold source outlet is connected to the low-pressure nitrogen pipeline.

2. The neon-helium recovery system for an air separation unit according to claim 1, characterized in that: The main condenser-evaporator is also equipped with a liquid nitrogen reflux port, and a separation section is provided at the liquid nitrogen reflux port. The feed inlet of the distillation column is also connected to the separation section.

3. The neon-helium recovery system for an air separation unit according to claim 1, characterized in that: The top of the lower tower is provided with a packing section, and the packing section is located between the gas phase rising channel of the lower tower and the gas phase inlet of the main condenser evaporator.

4. The neon-helium recovery system for an air separation unit according to claim 1, characterized in that: It also includes an upper tower, which has a side-line extraction port at the position corresponding to the argon enrichment zone, and the side-line extraction port is connected to the feed inlet of the fine argon evaporator.

5. The neon-helium recovery system for an air separation unit according to claim 4, characterized in that: A crude argon extraction unit is provided between the side-line extraction port and the feed inlet.

6. The neon-helium recovery system for an air separation unit according to claim 1, characterized in that: A liquid level sensor is installed on the outside of the distillation column, and the liquid level sensor is connected to the liquid outlet at the bottom of the column.

7. The neon-helium recovery system for an air separation unit according to claim 2, characterized in that: The inner diameter of the separation section is the same as the inner diameter of the pipe at the liquid nitrogen reflux port.

8. The neon-helium recovery system for an air separation unit according to any one of claims 1-7, characterized in that: The condensation equipment is provided with a storage tank for storing crude neon and helium products on its outer side, and the storage tank is connected to the non-condensable gas outlet on the condensation side.

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