A natural gas helium extraction system coupled with the waste heat of an air separation plant

Abstract

The utility model discloses a kind of natural gas helium extraction systems of coupling utilization air separation device waste heat, comprising filter, first heat exchanger, catalytic dehydrogenation device, demisting tower, decarbonization drying device, second heat exchanger, membrane separation device, third heat exchanger, fourth heat exchanger, rectifying tower and refining device sequentially connected, the input end of filter is connected with natural gas inlet pipeline, the output end of refining device is connected with high-purity helium outlet pipeline, LNG condensate input pipeline is connected between third heat exchanger and rectifying tower, refrigerant input pipeline is connected between fourth heat exchanger and air separation device, membrane separation device is connected with helium extraction tail gas outlet pipeline, third heat exchanger is connected with helium extraction tail gas outlet pipeline by cold flow liquid outlet pipeline, the system can reduce the natural gas processing capacity of cryogenic separation unit by combining membrane separation method and cryogenic method to extract helium, reduce investment and operating cost, while the required cold capacity of cryogenic separation unit is provided by the surplus liquid nitrogen product generated by existing air separation device in factory area, system does not need additional cold energy supplement, reduce energy consumption.

Description

Technical Field

[0001] This utility model belongs to the field of natural gas helium extraction technology, specifically relating to a natural gas helium extraction system that couples with the residual cooling of an air separation unit. Background Technology

[0002] Helium is a vital resource for national security and the development of high-tech industries, with wide applications in defense, aerospace, semiconductor manufacturing, and medicine. The concentration of helium in the air is low, making it difficult to utilize as a resource. Extracting helium from natural gas is currently the only viable method for helium resource utilization. Cryogenic extraction from natural gas is currently the main method for industrial helium extraction, but this method is costly, requires a large area, and consumes a lot of energy. Membrane permeation separation has advantages such as high selectivity, low cost, low energy consumption, and high operational flexibility. However, relying solely on membrane separation technology makes it difficult to simultaneously achieve high recovery rates and high purity, and it also involves high investment costs.

[0003] While combining membrane separation with cryogenic separation can reduce the energy consumption of cryogenic separation, it still requires a separate refrigeration system, resulting in additional energy consumption and carbon emissions. Air separation units have surplus liquid nitrogen products containing a large amount of high-grade cold energy; conventional methods of utilizing liquid nitrogen (heating and vaporizing it for use as sealing gas, purging gas, etc.) would lead to a waste of this cold energy. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this utility model is to provide a natural gas helium extraction system that couples and utilizes the residual cooling of an air separation unit, which can solve the problems of high cost, large footprint, and high energy consumption in the existing natural gas helium extraction technology.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A natural gas helium extraction system that utilizes the residual cooling of an air separation unit includes a purification unit, a membrane separation unit, a cryogenic separation unit, and a refining unit connected in sequence. The purification unit includes a filter, a catalytic dehydrogenation unit, a demister, and a decarbonization drying unit; the membrane separation unit includes a membrane separation unit; and the cryogenic separation unit includes a distillation column. The filter has an input end connected to a natural gas inlet pipe, an output end connected to the input end of a catalytic dehydrogenation unit via a first gas pipe, a top output end of the catalytic dehydrogenation unit connected to the input end of a demister via a second gas pipe, a top output end of the demister connected to the input end of a decarbonization and drying unit via a third gas pipe, an output end of the decarbonization and drying unit connected to the input end of a membrane separation unit via a fourth gas pipe, an output end of the membrane separation unit connected to the input end of a distillation column via a fifth gas pipe, a top output end of the distillation column connected to the input end of a purification unit via a sixth gas pipe, and an output end of the purification unit connected to a high-purity helium outlet pipe.

[0006] This utility model also includes the following technical features: The first ventilation pipe is equipped with a first heat exchanger for preheating natural gas to create conditions for subsequent catalytic dehydrogenation.

[0007] The upper part of the catalytic dehydrogenation device is connected to one end of an oxygen inlet pipe, the other end of which is connected to the oxygen outlet of the air separation unit, and the bottom of the catalytic dehydrogenation device is connected to a reaction liquid discharge pipe.

[0008] The bottom of the demister is connected to a sewage pipe.

[0009] The fourth gas duct is equipped with a second heat exchanger for heating the natural gas after decarbonization and drying.

[0010] The cryogenic separation unit also includes a third heat exchanger and a fourth heat exchanger, which are sequentially installed on the fifth ventilation pipe. The cold flow channel inlet of the third heat exchanger is connected to the LNG condensate outlet at the bottom of the distillation column by an LNG condensate input pipe. One end of the refrigerant input pipe is connected to the cold flow channel inlet of the fourth heat exchanger, and the other end of the refrigerant input pipe is connected to the liquid nitrogen outlet of the air separation unit. A nitrogen outlet pipe is connected to the cold flow channel outlet of the fourth heat exchanger.

[0011] The membrane separation device is provided with a non-permeable gas outlet at the bottom, and a helium extraction tail gas outlet pipe is connected to the non-permeable gas outlet. A cold liquid outlet pipe is connected between the cold flow channel outlet of the third heat exchanger and the helium extraction tail gas outlet pipe.

[0012] Compared with the prior art, this utility model has the following technical effects: This utility model discloses a natural gas helium extraction system that utilizes a combination of a membrane separation unit and a cryogenic separation unit. Natural gas is pre-purified in the membrane separation unit and then highly purified in the cryogenic separation unit. The membrane separation unit reduces the natural gas throughput of the cryogenic separation unit, decreases energy consumption, improves the overall efficiency of the helium extraction process, and lowers investment and operating costs. The crude helium gas after membrane separation is cooled and liquefied in the cryogenic separation unit through a third and fourth heat exchanger before entering a distillation column for precise separation of gas components and further purification of helium. The cryogenically separated helium undergoes final purification in a refining unit to obtain high-purity helium. The oxygen used in the catalytic dehydrogenation unit and the cooling capacity required by the cryogenic separation unit can be provided by surplus products from the existing air separation unit in the plant, eliminating the need for additional cooling and reducing energy consumption. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the helium extraction system of this utility model.

[0014] The meanings of the labels in the diagram are as follows: 1. Filter; 2. Catalytic dehydrogenation unit; 3. Demisting tower; 4. Decarbonization and drying unit; 5. Membrane separation unit; 6. Distillation tower; 7. Refining unit; 8. Natural gas inlet pipeline; 9. First gas inlet pipeline; 10. Second gas inlet pipeline; 11. Third gas inlet pipeline; 12. Fourth gas inlet pipeline; 13. Fifth gas inlet pipeline; 14. Sixth gas inlet pipeline; 15. High-purity helium outlet pipeline; 16. First heat exchanger; 17. Oxygen inlet pipeline; 18. Reaction liquid outlet pipeline; 19. Sewage pipe; 20. Second heat exchanger; 21. Third heat exchanger; 22. Fourth heat exchanger; 23. LNG condensate inlet pipeline; 24. Refrigerant inlet pipeline; 25. Nitrogen outlet pipeline; 26. Helium extraction tail gas outlet pipeline; 27. Cold liquid outlet pipeline.

[0015] The specific content of this utility model will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0016] Following the above technical solution, the following are specific embodiments of this utility model. It should be noted that this utility model is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solution of this application fall within the protection scope of this utility model.

[0017] In this utility model, unless otherwise stated, directional terms such as "upper", "lower", "left", and "right" are generally defined based on the drawing in the corresponding figure; "inner" and "outer" refer to the inner and outer contours of the corresponding components; and "longitudinal", "transverse", and "vertical" refer to the directions marked in the figure.

[0018] Example: This embodiment presents a natural gas helium extraction system that couples with the waste cooling of an air separation unit, such as... Figure 1 As shown, it includes a purification unit, a membrane separation unit, a cryogenic separation unit, and a refining device 7 connected in sequence; The purification unit includes a filter 1, a catalytic dehydrogenation device 2, a demister 3, and a decarbonization and drying device 4; the membrane separation unit includes a membrane separation device 5; and the cryogenic separation unit includes a distillation column 6. The input end of filter 1 is connected to a natural gas inlet pipe 8. The output end of filter 1 is connected to the input end of catalytic dehydrogenation unit 2 via a first ventilation pipe 9. The top output end of catalytic dehydrogenation unit 2 is connected to the input end of demister 3 via a second ventilation pipe 10. The top output end of demister 3 is connected to the input end of decarbonization drying unit 4 via a third ventilation pipe 11. The output end of decarbonization drying unit 4 is connected to the input end of membrane separation unit 5 via a fourth ventilation pipe 12. The output end of membrane separation unit 5 is connected to the input end of distillation column 6 via a fifth ventilation pipe 13. The top output end of distillation column 6 is connected to the input end of purification unit 7 via a sixth ventilation pipe 14. The output end of purification unit 7 is connected to a high-purity helium outlet pipe 15.

[0019] In use, the various components can be assembled into a skid-mounted form, resulting in a compact structure that saves space and on-site installation work. Natural gas is supplied to the entire system through the natural gas intake pipe 8. The natural gas is first purified in the purification unit, where filter 1 removes solid impurities and particulate matter to prevent these impurities from entering subsequent equipment and causing blockages or damage. The filtered natural gas enters the catalytic dehydrogenation unit 2 through the first gas inlet pipe 9. In this embodiment, one end of the oxygen intake pipe 17 is connected to the upper part of the catalytic dehydrogenation unit 2, and the other end of the oxygen intake pipe 17 is connected to the oxygen outlet of the air separation unit in the plant area. The oxygen enters the catalytic dehydrogenation unit 2 and reacts with hydrogen in the natural gas to produce water dehydrogenation. The resulting liquid is discharged from the system through the reaction liquid discharge pipe 18 at the bottom of the catalytic dehydrogenation unit 2. The demister tower 3 removes mist droplets carried in the natural gas, preventing... To prevent droplets from entering subsequent equipment and affecting the separation effect, the natural gas is then decarbonized and dried by the decarbonization and drying unit 4 to remove acidic gases such as carbon dioxide and dry it to remove moisture, preventing it from freezing or clogging the flow channel during subsequent low-temperature processes. The natural gas purified by the purification unit is fed into the membrane separation unit 5 of the membrane separation unit through the fourth gas pipe 12 for crude purification. Utilizing the selective permeability of the membrane, helium is separated from the natural gas. The resulting crude helium gas enters the distillation column 6 in the cryogenic separation unit through the fifth gas pipe 13. Utilizing the difference in boiling points between the components in the crude helium gas, helium is separated from other components in the distillation column 6, further increasing the helium concentration. The cryogenically separated helium gas enters the refining unit 7 through the sixth gas pipe 14 for final refining to remove residual trace impurities. The purified high-purity helium gas is led out through the high-purity helium outlet pipe 15.

[0020] As a preferred embodiment, the first gas pipeline 9 is equipped with a first heat exchanger 16 for preheating natural gas to create conditions for subsequent catalytic dehydrogenation.

[0021] As a preferred embodiment, the bottom of the defogging tower 3 is connected to a drain pipe 19 to discharge the mist droplets from the system.

[0022] As a preferred embodiment, a second heat exchanger 20 for heating the natural gas after decarbonization and drying is installed on the fourth gas pipe 12 in this embodiment, which increases the temperature of the natural gas entering the membrane separation unit and is beneficial to improving the helium extraction efficiency of the membrane separation unit.

[0023] As a preferred embodiment, the cryogenic separation unit in this embodiment further includes a third heat exchanger 21 and a fourth heat exchanger 22, which are sequentially installed on the fifth ventilation pipe 13. The inlet of the cold flow channel of the third heat exchanger 21 is connected to the LNG condensate outlet at the bottom of the distillation column 6 by an LNG condensate input pipe 23. The cold energy carried by the LNG condensate can perform the first step of cooling on the crude helium gas, making full use of the energy generated in the entire system and reducing costs. One end of the refrigerant input pipe 24 is connected to the inlet of the cold flow channel of the fourth heat exchanger 22. The other end of the refrigerant input pipe 24 is connected to the liquid nitrogen outlet of the air separation unit in the plant area. The surplus liquid nitrogen product generated by the existing air separation unit in the plant area can be directly used in this system without the need for additional cold energy, thus reducing energy consumption and costs. A nitrogen outlet pipe 25 is connected to the outlet of the cold flow channel of the fourth heat exchanger 22.

[0024] As a preferred embodiment, the membrane separation device in this embodiment is provided with a non-permeable gas outlet at the bottom, and a helium extraction tail gas outlet pipe 26 is connected to the non-permeable gas outlet. A cold liquid outlet pipe 27 is connected between the cold flow channel outlet of the third heat exchanger 21 and the helium extraction tail gas outlet pipe 26. The non-permeable gas from the membrane separation device 5 and the natural gas from the cryogenic separation unit can be pressurized and returned to the natural gas pipeline network or sent to the fuel gas pipeline network.

[0025] This natural gas helium extraction system pre-purifies natural gas in a membrane separation unit, followed by high-purification in a cryogenic separation unit. The membrane separation unit 5 reduces the natural gas throughput of the cryogenic separation unit, decreases energy consumption, improves the overall efficiency of the helium extraction process, and lowers investment and operating costs. The crude helium gas is cooled and liquefied in the cryogenic separation unit through the third heat exchanger 21 and the fourth heat exchanger 22 before entering the distillation column 6 for distillation, achieving precise separation of gas components and further purifying the helium. The cryogenically separated helium undergoes final purification in the refining unit 7 to obtain high-purity helium.

Claims

1. A natural gas helium extraction system that couples with the waste cooling of an air separation unit, characterized in that, It includes a purification unit, a membrane separation unit, a cryogenic separation unit and a refining device connected in sequence (7); The purification unit includes a filter (1), a catalytic dehydrogenation device (2), a demisting tower (3) and a decarbonization drying device (4); the membrane separation unit includes a membrane separation device (5); and the cryogenic separation unit includes a distillation tower (6). The filter (1) is connected to a natural gas inlet pipe (8) at its input end. The filter (1) is connected to the input end of the catalytic dehydrogenation device (2) via a first gas inlet pipe (9). The top output end of the catalytic dehydrogenation device (2) is connected to the input end of the demister (3) via a second gas inlet pipe (10). The top output end of the demister (3) is connected to the input end of the decarbonization drying device (4) via a third gas inlet pipe (11). The output end of the decarbonization drying device (4) is connected to the input end of the membrane separation device (5) via a fourth gas inlet pipe (12). The output end of the membrane separation device (5) is connected to the input end of the distillation column (6) via a fifth gas inlet pipe (13). The top output end of the distillation column (6) is connected to the input end of the purification device (7) via a sixth gas inlet pipe (14). The output end of the purification device (7) is connected to a high-purity helium outlet pipe (15).

2. The natural gas helium extraction system utilizing waste cooling from an air separation unit as described in claim 1, characterized in that, The first gas duct (9) is equipped with a first heat exchanger (16) for preheating natural gas to create conditions for subsequent catalytic dehydrogenation.

3. The natural gas helium extraction system utilizing waste cooling from an air separation unit as described in claim 1, characterized in that, The upper part of the catalytic dehydrogenation device (2) is connected to one end of an oxygen inlet pipe (17), the other end of which is connected to the oxygen outlet of the air separation unit, and the bottom of the catalytic dehydrogenation device (2) is connected to a reaction liquid discharge pipe (18).

4. The natural gas helium extraction system utilizing waste cooling from an air separation unit as described in claim 1, characterized in that, The bottom of the demister (3) is connected to a sewage pipe (19).

5. The natural gas helium extraction system utilizing waste cooling from an air separation unit as described in claim 1, characterized in that, The fourth gas duct (12) is equipped with a second heat exchanger (20) for heating the natural gas after decarbonization and drying.

6. The natural gas helium extraction system utilizing waste cooling from an air separation unit as described in claim 1, characterized in that, The cryogenic separation unit also includes a third heat exchanger (21) and a fourth heat exchanger (22), which are installed sequentially on the fifth ventilation pipe (13). The cold flow channel inlet of the third heat exchanger (21) is connected to the LNG condensate outlet at the bottom of the distillation column (6) by an LNG condensate input pipe (23). The cold flow channel inlet of the fourth heat exchanger (22) is connected to one end of a refrigerant input pipe (24), and the other end of the refrigerant input pipe (24) is connected to the liquid nitrogen outlet of the air separation unit. The cold flow channel outlet of the fourth heat exchanger (22) is connected to a nitrogen outlet pipe (25).

7. The natural gas helium extraction system utilizing waste cooling from an air separation unit as described in claim 6, characterized in that, The membrane separation device is provided with a non-permeable gas outlet at the bottom, and a helium extraction tail gas outlet pipe (26) is connected to the non-permeable gas outlet. A cold liquid outlet pipe (27) is connected between the cold flow channel outlet of the third heat exchanger (21) and the helium extraction tail gas outlet pipe (26).

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