A combined system of an air separation unit and a hydrogen liquefaction precooling unit coupled with LNG cold energy

Abstract

The present invention provides a combined system of an air separation device and a hydrogen liquefaction precooling device coupled with LNG cold energy, belonging to the field of nitrogen cycle refrigeration. The system comprises: a hydrogen liquefaction precooling device, the hydrogen liquefaction precooling device comprising a hydrogen liquefaction precooling cold box, a raw hydrogen pipeline passing through the hydrogen liquefaction precooling cold box; an air separation device, the air separation device comprising an air rectification tower, a main heat exchange unit and a nitrogen refrigeration unit, the air rectification tower being provided with a product nitrogen pipeline, a first nitrogen pipeline and a second nitrogen pipeline, the nitrogen component separated in the air rectification unit entering the hydrogen liquefaction precooling cold box through the product nitrogen pipeline, providing cooling capacity for the hydrogen liquefaction precooling cold box, reducing the temperature of the raw hydrogen in the hydrogen liquefaction process, completing the precooling stage of the raw hydrogen, effectively reducing the power consumption of the air separation device and the hydrogen liquefaction device, saving the number of refrigeration equipment, reducing equipment investment, reducing cooling energy loss and improving energy utilization.

Description

Technical Field

[0001] The present invention belongs to the field of nitrogen cycle refrigeration, and more specifically, relates to a combined system of an air separation device coupled with LNG cold energy and a hydrogen liquefaction precooling device. Background Art

[0002] As the global energy system gradually shifts from fossil fuels to clean energy, hydrogen energy has garnered widespread attention due to its high energy density and pollution-free nature. The establishment of a supply chain is a crucial component in the development of hydrogen energy technology, and hydrogen storage and transportation technologies are essential for its large-scale utilization. Compared to gaseous hydrogen, liquid hydrogen has a higher energy density and lower storage pressure, offering significant transportation advantages. Therefore, the development of liquid hydrogen production technology is of great significance to the development of hydrogen energy technology.

[0003] With the promotion of hydrogen energy technology, liquid hydrogen technology has gradually received attention. However, in the liquid hydrogen production process, the existing technology's cold energy consumption and equipment investment require a large amount of capital investment. Therefore, the high cost restricts the promotion of liquid hydrogen technology. Summary of the Invention

[0004] The purpose of the present invention is to address the deficiencies in the prior art and provide a combined system of an air separation unit and a hydrogen liquefaction pre-cooling unit that couples LNG cold energy. The present invention allows the nitrogen component separated in the air distillation unit to enter the hydrogen liquefaction pre-cooling cold box to provide cooling capacity for the hydrogen liquefaction pre-cooling cold box, effectively reducing the power consumption of the air separation unit and the hydrogen liquefaction unit, while saving the number of refrigeration equipment, and solving the problem that in the liquid hydrogen production process, the existing technology requires a large amount of capital investment in cold energy consumption and equipment investment. Therefore, the high cost restricts the promotion of liquid hydrogen technology.

[0005] To achieve the above objectives, the present invention provides a combined system of an air separation unit coupled with LNG cold energy and a hydrogen liquefaction precooling unit, the system comprising:

[0006] A hydrogen liquefaction precooling device, comprising a hydrogen liquefaction precooling cold box, through which the raw hydrogen pipeline passes;

[0007] An air separation unit, comprising an air rectification tower, a main heat exchange unit, and a nitrogen refrigeration unit, wherein a feed air pipeline passes through the main heat exchange unit and is connected to the air rectification tower, and the air rectification tower is provided with a product nitrogen pipeline, a first nitrogen pipeline, and a second nitrogen pipeline;

[0008] The first outlet of the main heat exchange unit is connected to the first inlet of the nitrogen refrigeration unit through a first pipeline, and the first outlet of the nitrogen refrigeration unit is connected to the first inlet of the main heat exchange unit through a second pipeline;

[0009] The first nitrogen pipeline of the air rectification tower passes through the main heat exchange unit and is connected to the first pipeline, the second nitrogen pipeline of the air rectification tower is connected to the second inlet of the main heat exchange unit, and the second outlet of the main heat exchange unit is connected to the third nitrogen pipeline;

[0010] The product nitrogen pipeline or the third nitrogen pipeline is connected to the hydrogen liquefaction pre-cooling cold box.

[0011] Optionally, a gas-liquid separator is provided on the second pipeline, the gas phase outlet of the gas-liquid separator is connected to the main heat exchange unit through a nitrogen branch pipeline, and the liquid phase outlet of the gas-liquid separator is connected to the main heat exchange unit through a liquid nitrogen branch pipeline.

[0012] Optionally, the main heat exchange unit includes an air pre-cooling heat exchanger, a main heat exchanger and a product heat exchanger;

[0013] The raw air pipeline passes through the air pre-cooling heat exchanger and the main heat exchanger;

[0014] The first nitrogen pipeline and the nitrogen branch pipeline both pass through the main heat exchanger and are connected to the first pipeline;

[0015] The second nitrogen pipeline of the air rectification tower passes through the product heat exchanger and is connected to the third nitrogen pipeline. The third nitrogen pipeline passes through the hydrogen liquefaction pre-cooling cold box and is connected to the first pipeline.

[0016] The liquid nitrogen branch pipeline passes through the product heat exchanger and the main heat exchanger and is connected to the first pipeline.

[0017] Optionally, the nitrogen refrigeration unit comprises a nitrogen refrigeration heat exchanger, a plurality of nitrogen compressors and an external refrigerant pipeline;

[0018] The external refrigerant pipeline passes through the nitrogen refrigeration heat exchanger and is connected to the LNG receiving station, and the external refrigerant pipeline is used to transport LNG to provide cooling capacity for the nitrogen refrigeration heat exchanger;

[0019] The first pipeline passes through the nitrogen refrigeration heat exchanger and is connected to the second pipeline. The multiple nitrogen compressors are arranged in sequence and connected to the first pipeline. The portion of the first pipeline located between two adjacent nitrogen compressors passes through the nitrogen refrigeration heat exchanger.

[0020] Optionally, the system further comprises a first intermediate heat exchange medium heat absorption pipeline and a second intermediate heat exchange medium heat absorption pipeline, and the nitrogen refrigeration unit further comprises an intermediate heat exchanger;

[0021] The external refrigerant pipeline and the second intermediate heat exchange medium heat absorption pipeline both pass through the intermediate heat exchanger, the first intermediate heat exchange medium heat absorption pipeline passes through the air pre-cooling heat exchanger, and the two ends of the first intermediate heat exchange medium heat absorption pipeline are respectively connected to the two ends of the second intermediate heat exchange medium heat absorption pipeline.

[0022] Optionally, the product nitrogen pipeline is connected to the liquid nitrogen outlet or the first nitrogen outlet of the air rectification tower 102, and the product nitrogen pipeline passes through the hydrogen liquefaction pre-cooling cold box and is connected to the first pipeline.

[0023] Optionally, when the product nitrogen pipeline is connected to the first nitrogen outlet of the air distillation tower, the hydrogen liquefaction precooling device also includes a precooling refrigerant pipeline, which passes through the hydrogen liquefaction precooling cold box and is connected to the LNG receiving station. The precooling refrigerant pipeline is used to transport LNG to provide cooling capacity for the hydrogen liquefaction precooling cold box.

[0024] Optionally, when the third nitrogen pipeline is connected to the hydrogen liquefaction pre-cooling cold box, the hydrogen liquefaction pre-cooling device further includes a circulating refrigerant pre-cooling pipeline, and the circulating refrigerant pre-cooling pipeline passes through the hydrogen liquefaction pre-cooling cold box.

[0025] Optionally, a throttle valve is connected to the second pipeline.

[0026] Optionally, both the product nitrogen pipeline and the third nitrogen pipeline are connected with a throttle valve, and the throttle valve is used for throttling and reducing pressure.

[0027] The present invention provides a combined system of an air separation device coupled with LNG cold energy and a hydrogen liquefaction precooling device, which has the following beneficial effects:

[0028] In this system, the air distillation tower unit is connected to a product nitrogen pipeline. The nitrogen components separated in the air distillation unit, such as liquid nitrogen or low-pressure nitrogen, enter the hydrogen liquefaction pre-cooling cold box through the product nitrogen pipeline to provide cooling capacity for the hydrogen liquefaction pre-cooling cold box. At the same time, the air distillation tower is also connected to a second nitrogen pipeline. The nitrogen separated by the air distillation tower passes through the main heat exchange unit, absorbs cooling capacity to produce liquid nitrogen, and provides cooling capacity for the hydrogen liquefaction pre-cooling cold box through a third nitrogen pipeline. In turn, the temperature of the raw hydrogen in the hydrogen liquefaction process is reduced, completing the pre-cooling stage of the raw hydrogen, effectively reducing the power consumption of the air separation unit and the hydrogen liquefaction unit, while saving the number of refrigeration equipment, reducing equipment investment, and reducing the amount of cooling energy loss, thereby improving energy utilization.

[0029] This system is particularly suitable for use in LNG receiving stations. It uses external refrigerant pipelines to transport LNG to provide cooling for nitrogen refrigeration heat exchangers, thereby realizing the recovery and utilization of LNG cold energy. At the same time, it reduces the operating costs of air separation units and hydrogen liquefaction units, reduces the cost of liquid hydrogen production, and is conducive to the promotion of hydrogen liquefaction technology.

[0030] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0032] Figure 1 A schematic diagram of a combined system of an air separation device coupled with LNG cold energy and a hydrogen liquefaction pre-cooling device according to a first embodiment of the present invention is shown.

[0033] Figure 2 A schematic diagram of a combined system of an air separation device coupled with LNG cold energy and a hydrogen liquefaction pre-cooling device according to a second embodiment of the present invention is shown.

[0034] Figure 3 A schematic diagram of a combined system of an air separation device coupled with LNG cold energy and a hydrogen liquefaction pre-cooling device according to a third embodiment of the present invention is shown.

[0035] Figure 4 A schematic diagram of a main heat exchange unit according to embodiment one, two or three of the present invention is shown.

[0036] Figure 5 A schematic diagram of a nitrogen refrigeration unit according to Embodiment 1, 2 or 3 of the present invention is shown.

[0037] Description of reference numerals:

[0038] 101. Hydrogen liquefaction pre-cooling cold box; 102. Air distillation unit; 103. Main heat exchange unit; 104. Nitrogen refrigeration unit; 105. Gas-liquid separator;

[0039] 201. Air pre-cooling heat exchanger; 202. Main heat exchanger; 203. Product heat exchanger; 204. Intermediate heat exchanger; 205. Nitrogen refrigeration heat exchanger; 206. Nitrogen compressor;

[0040] 401. First nitrogen pipeline; 402. Raw air pipeline; 403. Nitrogen branch pipeline; 404. Liquid nitrogen branch pipeline; 405. First intermediate heat exchange medium heat absorption pipeline; 406. Second nitrogen pipeline; 407. First pipeline; 408. External refrigerant pipeline; 409. Second intermediate heat exchange medium heat absorption pipeline; 410. Raw hydrogen pipeline; 412. Supplementary pre-cooling refrigerant pipeline; 413. Circulating refrigerant pre-cooling pipeline; 414. Product nitrogen pipeline; 415. Second pipeline; 416. Third nitrogen pipeline. DETAILED DESCRIPTION

[0041] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Instead, these embodiments are provided to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art. Example

[0042] like Figure 1 、 Figure 4 and Figure 5 As shown, the present invention provides a combined system of an air separation device coupled with LNG cold energy and a hydrogen liquefaction precooling device, the system comprising:

[0043] A hydrogen liquefaction precooling device includes a hydrogen liquefaction precooling cold box 101, and a raw hydrogen pipeline 410 passes through the hydrogen liquefaction precooling cold box 101;

[0044] An air separation unit includes an air rectification tower 102, a main heat exchange unit 103, and a nitrogen refrigeration unit 104. A feed air pipeline 402 passes through the main heat exchange unit 103 and is connected to the air rectification tower 102. The air rectification tower 102 is provided with a product nitrogen pipeline 414 and a first nitrogen pipeline 401.

[0045] The first outlet of the main heat exchange unit 103 is connected to the first inlet of the nitrogen refrigeration unit 104 via the first pipeline 407 , and the first outlet of the nitrogen refrigeration unit 104 is connected to the first inlet of the main heat exchange unit 103 via the second pipeline 415 ;

[0046] The first nitrogen pipeline 401 of the air rectification tower 102 passes through the main heat exchange unit 103 and is connected to the first pipeline 407 , and the liquid nitrogen outlet of the air rectification tower 102 is connected to the product nitrogen pipeline 414 ;

[0047] The product nitrogen pipeline 414 passes through the hydrogen liquefaction pre-cooling cold box 101 and is connected to the first pipeline 407 .

[0048] A gas-liquid separator 105 is provided on the second pipeline 415 . The gas phase outlet of the gas-liquid separator 105 is connected to the main heat exchange unit 103 via a nitrogen branch pipeline 403 , and the liquid phase outlet of the gas-liquid separator 105 is connected to the main heat exchange unit 103 via a liquid nitrogen branch pipeline 404 .

[0049] Specifically, the hydrogen liquefaction pre-cooling cold box 101 is used to provide cooling capacity for the raw hydrogen in the hydrogen liquefaction process to complete the pre-cooling stage. The air distillation tower 102 is used to complete the separation of air. The main heat exchange unit 103 is used to provide cooling capacity for the air distillation tower 102 and the raw air. The nitrogen refrigeration unit 104 is used to complete the refrigeration of nitrogen to produce low-temperature nitrogen. The gas-liquid separator 105 is used to complete the separation of nitrogen and liquid nitrogen. The first nitrogen pipeline 401 is a low-pressure nitrogen pipeline.

[0050] Before using the raw air, it must first be purified and the temperature is 25°C. The raw air is purified to obtain clean air, which does not contain impurities, water vapor, etc. At the same time, the raw air is also compressed, water-cooled and pressurized. Then, after purification, pressurization and water cooling, the raw air at room temperature has a pressure of 0.8 MPa(A) and a temperature of 25°C.

[0051] The product nitrogen pipeline 414 is placed in the pre-cooling cold box 101. The inlet of the product nitrogen pipeline 414 is connected to the liquid nitrogen outlet of the air distillation tower 102 and is used to transport liquid nitrogen from the air distillation tower 102. The outlet of the product nitrogen pipeline 414 is connected to the inlet of the first pipeline 407. The liquid nitrogen releases cold energy in the pre-cooling cold box 101, and the temperature rises to 20°C. After being converted into nitrogen, it enters the nitrogen refrigeration unit 104 to obtain cold energy. The raw hydrogen pipeline 410 is placed in the pre-cooling cold box 101 and is used to transport raw hydrogen. After the raw hydrogen absorbs cold energy, its temperature drops to -198°C.

[0052] In this embodiment, the main heat exchange unit 103 includes an air pre-cooling heat exchanger 201, a main heat exchanger 202 and a product heat exchanger 203;

[0053] The raw air line 402 passes through the air pre-cooling heat exchanger 201 and the main heat exchanger 202;

[0054] The first nitrogen pipeline 401 and the nitrogen branch pipeline 403 both pass through the main heat exchanger 202 and are connected to the first pipeline 407;

[0055] The liquid nitrogen branch line 404 passes through the product heat exchanger 203 and the main heat exchanger 202 and is connected to the first line 407 .

[0056] Specifically, the raw air pipeline 402 is placed in the air pre-cooling heat exchanger 201 and the main heat exchanger 202 in sequence, and is used to transport the raw air to absorb cold energy, and is finally connected to the raw air inlet of the air rectification tower 102. The raw air outlet temperature of the air pre-cooling heat exchanger 201 is -8°C, and the temperature is reduced to -171°C after passing through the main heat exchanger 202.

[0057] The liquid nitrogen branch line 404 is placed in the product heat exchanger 203 and the main heat exchanger 202 in sequence, and is used to transport liquid nitrogen from the gas-liquid separator 105. The liquid nitrogen releases cold energy in the product heat exchanger 203 and the main heat exchanger 202.

[0058] The first nitrogen pipeline 401 and the nitrogen branch pipeline 403 are placed in the main heat exchanger 202 and are used to transport low-temperature nitrogen from the gas-liquid separator 105 and the low-temperature nitrogen from the air distillation tower 102 respectively, providing cooling capacity in the main heat exchanger 202.

[0059] In this embodiment, the system further includes a first intermediate heat exchange medium heat absorption pipeline 405 and a second intermediate heat exchange medium heat absorption pipeline 409, and the nitrogen refrigeration unit includes an intermediate heat exchanger 204, a nitrogen refrigeration heat exchanger 205, a plurality of nitrogen compressors 208 and an external refrigerant pipeline 408;

[0060] The external refrigerant line 408 passes through the nitrogen refrigeration heat exchanger 205 and is connected to the LNG receiving station. The external refrigerant line 408 is used to transport LNG to provide cooling for the nitrogen refrigeration heat exchanger 205.

[0061] The first pipeline 407 passes through the nitrogen refrigeration heat exchanger 205 and is connected to the second pipeline 415. A plurality of nitrogen compressors 208 are arranged in sequence and connected to the first pipeline 407. The portion of the first pipeline 407 between two adjacent nitrogen compressors 208 passes through the nitrogen refrigeration heat exchanger 205.

[0062] The external refrigerant pipeline 408 and the second intermediate heat exchange medium heat absorption pipeline 409 both pass through the intermediate heat exchanger 204, the first intermediate heat exchange medium heat absorption pipeline 405 passes through the air pre-cooling heat exchanger 201, and both ends of the first intermediate heat exchange medium heat absorption pipeline 405 are respectively connected to both ends of the second intermediate heat exchange medium heat absorption pipeline 409;

[0063] The number of nitrogen compressors 206 is three;

[0064] A throttle valve is connected to the second pipeline 415 .

[0065] Specifically, the external refrigerant line 408 is placed in the nitrogen refrigeration heat exchanger 205 and the intermediate heat exchanger 204 in sequence to transport LNG and release cold energy. The LNG inlet temperature of the external refrigerant line 408 is -160°C. After heat exchange in the nitrogen refrigeration heat exchanger 205, the temperature is reduced to -87°C. The temperature at the outlet of the external refrigerant line 408 is increased to 6°C. It can be connected to the natural gas transmission system to transmit the reheated natural gas.

[0066] According to the flow direction of the logistics, the first pipeline 407 is successively placed in the first-stage nitrogen compressor 206, the nitrogen refrigeration heat exchanger 205, the second-stage nitrogen compressor 206, the nitrogen refrigeration heat exchanger 205, the third-stage nitrogen compressor 206, and the nitrogen refrigeration heat exchanger 205, for transporting nitrogen. The nitrogen is pressurized and cooled three times. At the inlet of the first pipeline 407, the nitrogen temperature is 8°C and the pressure is 0.38 MPa (A). After pressurization and cooling, the temperature is -158°C and the pressure is 6.4 MPa (A). A throttle valve is set at the outlet of the second pipeline 415. After throttling and pressure reduction, the temperature is -184°C.

[0067] The first intermediate heat exchange medium heat absorption pipeline 405 and the second intermediate heat exchange medium heat absorption pipeline 409 form a loop pipeline. The second intermediate heat exchange medium heat absorption pipeline 409 passes through the intermediate heat exchanger 204 and is used to transport ethylene glycol to absorb cold energy. The first intermediate heat exchange medium heat absorption pipeline 405 passes through the first air pre-cooling heat exchanger 201 and is used to transport ethylene glycol to release cold energy and reduce the temperature of the raw air.

[0068] In this embodiment, a throttle valve is connected to the product nitrogen pipeline 414, and the throttle valve is used for throttling and reducing pressure. Example

[0069] like Figure 2 、 Figure 4 and Figure 5 As shown, the difference between the second embodiment and the first embodiment is that: a combined system of an air separation device coupled with LNG cold energy and a hydrogen liquefaction precooling device, the system comprising:

[0070] A hydrogen liquefaction precooling device includes a hydrogen liquefaction precooling cold box 101, and a raw hydrogen pipeline 410 passes through the hydrogen liquefaction precooling cold box 101;

[0071] An air separation unit includes an air rectification tower 102, a main heat exchange unit 103, and a nitrogen refrigeration unit 104. A feed air pipeline 402 passes through the main heat exchange unit 103 and is connected to the air rectification tower 102. The air rectification tower 102 is provided with a product nitrogen pipeline 414 and a first nitrogen pipeline 401.

[0072] The first outlet of the main heat exchange unit 103 is connected to the first inlet of the nitrogen refrigeration unit 104 via the first pipeline 407 , and the first outlet of the nitrogen refrigeration unit is connected to the first inlet of the main heat exchange unit 103 via the second pipeline 415 ;

[0073] The first nitrogen pipeline 401 of the air rectification tower 102 passes through the main heat exchange unit 103 and is connected to the first pipeline 407 . The first nitrogen outlet of the air rectification tower 102 is connected to the product nitrogen pipeline 414 .

[0074] The product nitrogen pipeline 414 passes through the hydrogen liquefaction pre-cooling cold box 101 and is connected to the first pipeline 407 .

[0075] Specifically, the product nitrogen pipeline 414 is placed in the pre-cooling cold box 101, and the inlet of the product nitrogen pipeline 414 is connected to the first nitrogen outlet of the air distillation tower 102 for conveying low-pressure nitrogen from the air distillation tower 102. The outlet of the product nitrogen pipeline 414 is connected to the inlet of the first pipeline 407. The low-pressure nitrogen releases cold energy in the pre-cooling cold box 101 and enters the nitrogen refrigeration unit 104 to obtain cold energy. The raw hydrogen pipeline 410 is placed in the pre-cooling cold box 101 for conveying raw hydrogen. After the raw hydrogen absorbs cold energy, its temperature decreases.

[0076] In this embodiment, the hydrogen liquefaction precooling device also includes a precooling refrigerant pipeline 412, which passes through the hydrogen liquefaction precooling cold box 101 and is connected to the LNG receiving station. The precooling refrigerant pipeline 412 is used to transport LNG to provide cooling for the hydrogen liquefaction precooling cold box 101.

[0077] Specifically, the supplementary pre-cooling refrigerant pipeline 412 is used to transport LNG to provide cooling capacity for the hydrogen liquefaction pre-cooling cold box 101. The inlet temperature of LNG in the hydrogen liquefaction pre-cooling cold box 101 is -160°C and the outlet temperature is 10°C, thereby realizing the recovery and utilization of LNG cold energy. Example

[0078] like Figure 3 、 Figure 4 and Figure 5 As shown, the difference between the third embodiment and the first embodiment is that: a combined system of an air separation device coupled with LNG cold energy and a hydrogen liquefaction precooling device, the system comprising:

[0079] A hydrogen liquefaction precooling device includes a hydrogen liquefaction precooling cold box 101, and a raw hydrogen pipeline 410 passes through the hydrogen liquefaction precooling cold box 101;

[0080] An air separation unit includes an air rectification tower 102, a main heat exchange unit 103, and a nitrogen refrigeration unit 104. A feed air pipeline 402 passes through the main heat exchange unit 103 and is connected to the air rectification tower 102. The air rectification tower 102 is provided with a first nitrogen pipeline 401 and a second nitrogen pipeline 406.

[0081] The first outlet of the main heat exchange unit 103 is connected to the first inlet of the nitrogen refrigeration unit 104 via the first pipeline 407 , and the first outlet of the nitrogen refrigeration unit 104 is connected to the first inlet of the main heat exchange unit 103 via the second pipeline 415 ;

[0082] The first nitrogen pipeline 401 of the air rectification tower 102 passes through the main heat exchange unit 103 and is connected to the first pipeline 407. The second nitrogen pipeline 406 of the air rectification tower 102 is connected to the second inlet of the main heat exchange unit 103. The second outlet of the main heat exchange unit 103 is connected to the third nitrogen pipeline 416.

[0083] The third nitrogen pipeline 416 is connected to the hydrogen liquefaction pre-cooling cold box 101;

[0084] The third nitrogen pipeline 416 is connected to a throttle valve for throttling and reducing pressure;

[0085] The second nitrogen pipeline 406 of the air rectification tower 102 passes through the product heat exchanger 203 and is connected to the third nitrogen pipeline 416 . The third nitrogen pipeline 416 passes through the hydrogen liquefaction pre-cooling cold box 101 and is connected to the first pipeline 407 .

[0086] Specifically, the second nitrogen pipeline 406 is a high-pressure nitrogen pipeline. The second nitrogen pipeline 406 is placed in the product heat exchanger 203 of the main heat exchange unit 103. The nitrogen absorbs cold energy to produce liquid nitrogen. Part of the liquid nitrogen is exported as a product, and the other part is connected to the third nitrogen pipeline 416 and enters the hydrogen liquefaction pre-cooling cold box 101 to provide cold energy. The third nitrogen pipeline 416 is provided with a throttle valve. After passing through the throttle valve, the pressure and temperature of the liquid nitrogen are reduced to -203°C, and the temperature leaving the pre-cooling cold box is 10°C.

[0087] The hydrogen liquefaction precooling device further includes a circulating refrigerant precooling pipeline 413 , which passes through the hydrogen liquefaction precooling cold box 101 .

[0088] Specifically, the circulating refrigerant pre-cooling pipeline 413 is used to transport the circulating refrigerant in the hydrogen liquefaction process to complete pre-cooling. The circulating refrigerant is circulated in the hydrogen liquefaction process to provide cooling capacity for the raw hydrogen.

[0089] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A combined system of an air separation unit coupled with LNG cold energy and a hydrogen liquefaction pre-cooling unit, characterized in that: The system includes: A hydrogen liquefaction precooling device, comprising a hydrogen liquefaction precooling cold box, through which the raw hydrogen pipeline passes; An air separation unit, comprising an air rectification tower, a main heat exchange unit, and a nitrogen refrigeration unit, wherein a feed air pipeline passes through the main heat exchange unit and is connected to the air rectification tower, and the air rectification tower is provided with a product nitrogen pipeline, a first nitrogen pipeline, and a second nitrogen pipeline; The first outlet of the main heat exchange unit is connected to the first inlet of the nitrogen refrigeration unit through a first pipeline, and the first outlet of the nitrogen refrigeration unit is connected to the first inlet of the main heat exchange unit through a second pipeline; The first nitrogen pipeline of the air rectification tower passes through the main heat exchange unit and is connected to the first pipeline, the second nitrogen pipeline of the air rectification tower is connected to the second inlet of the main heat exchange unit, and the second outlet of the main heat exchange unit is connected to the third nitrogen pipeline; The product nitrogen pipeline or the third nitrogen pipeline is connected to the hydrogen liquefaction pre-cooling cold box; A gas-liquid separator is provided on the second pipeline, the gas phase outlet of the gas-liquid separator is connected to the main heat exchange unit through a nitrogen branch pipeline, and the liquid phase outlet of the gas-liquid separator is connected to the main heat exchange unit through a liquid nitrogen branch pipeline; The main heat exchange unit includes an air pre-cooling heat exchanger, a main heat exchanger and a product heat exchanger; The raw air pipeline passes through the air pre-cooling heat exchanger and the main heat exchanger; The first nitrogen pipeline and the nitrogen branch pipeline both pass through the main heat exchanger and are connected to the first pipeline; The second nitrogen pipeline of the air rectification tower passes through the product heat exchanger and is connected to the third nitrogen pipeline, and the third nitrogen pipeline passes through the hydrogen liquefaction pre-cooling cold box and is connected to the first pipeline; The liquid nitrogen branch pipeline passes through the product heat exchanger and the main heat exchanger and is connected to the first pipeline.

2. The combined system of an air separation unit coupled with LNG cold energy and a hydrogen liquefaction pre-cooling unit according to claim 1 is characterized in that: The nitrogen refrigeration unit includes a nitrogen refrigeration heat exchanger, a plurality of nitrogen compressors and an external refrigerant pipeline; The external refrigerant pipeline passes through the nitrogen refrigeration heat exchanger and is connected to the LNG receiving station, and the external refrigerant pipeline is used to transport LNG to provide cooling capacity for the nitrogen refrigeration heat exchanger; The first pipeline passes through the nitrogen refrigeration heat exchanger and is connected to the second pipeline. The multiple nitrogen compressors are arranged in sequence and connected to the first pipeline. The portion of the first pipeline located between two adjacent nitrogen compressors passes through the nitrogen refrigeration heat exchanger.

3. The combined system of an air separation unit coupled with LNG cold energy and a hydrogen liquefaction pre-cooling unit according to claim 2 is characterized in that: The system further comprises a first intermediate heat exchange medium heat absorbing pipeline and a second intermediate heat exchange medium heat absorbing pipeline, and the nitrogen refrigeration unit further comprises an intermediate heat exchanger; The external refrigerant pipeline and the second intermediate heat exchange medium heat absorption pipeline both pass through the intermediate heat exchanger, the first intermediate heat exchange medium heat absorption pipeline passes through the air pre-cooling heat exchanger, and the two ends of the first intermediate heat exchange medium heat absorption pipeline are respectively connected to the two ends of the second intermediate heat exchange medium heat absorption pipeline.

4. The combined system of an air separation unit coupled with LNG cold energy and a hydrogen liquefaction pre-cooling unit according to claim 1 is characterized in that: The product nitrogen pipeline is connected to the liquid nitrogen outlet or the first nitrogen outlet of the air rectification tower, and the product nitrogen pipeline passes through the hydrogen liquefaction pre-cooling cold box and is connected to the first pipeline.

5. The combined system of an air separation unit coupled with LNG cold energy and a hydrogen liquefaction pre-cooling unit according to claim 4 is characterized in that: When the product nitrogen pipeline is connected to the first nitrogen outlet of the air distillation tower, the hydrogen liquefaction precooling device also includes a precooling refrigerant pipeline, which passes through the hydrogen liquefaction precooling cold box and is connected to the LNG receiving station. The precooling refrigerant pipeline is used to transport LNG to provide cooling capacity for the hydrogen liquefaction precooling cold box.

6. The combined system of an air separation unit coupled with LNG cold energy and a hydrogen liquefaction pre-cooling unit according to claim 1 is characterized in that: When the third nitrogen pipeline is connected to the hydrogen liquefaction pre-cooling cold box, the hydrogen liquefaction pre-cooling device further includes a circulating refrigerant pre-cooling pipeline, and the circulating refrigerant pre-cooling pipeline passes through the hydrogen liquefaction pre-cooling cold box.

7. The combined system of an air separation unit coupled with LNG cold energy and a hydrogen liquefaction pre-cooling unit according to claim 1 is characterized in that: The second pipeline is connected with a throttle valve.

8. The combined system of an air separation unit coupled with LNG cold energy and a hydrogen liquefaction pre-cooling unit according to claim 2 is characterized in that: The product nitrogen pipeline and the third nitrogen pipeline are both connected with a throttle valve.

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