A combined system of air separation unit and hydrogen liquefaction pre-cooling unit that comprehensively utilizes LNG cold energy

Abstract

The present invention provides a combined system of an air separation device and a hydrogen liquefaction precooling device for comprehensively utilizing LNG cold energy, and relates to the field of nitrogen cycle refrigeration. The system comprises: a hydrogen liquefaction precooling device, wherein the hydrogen liquefaction precooling device comprises a hydrogen liquefaction precooling cold box and a hydrogen liquefaction cryogenic cold box. A raw hydrogen pipeline passes through the hydrogen liquefaction precooling cold box and the hydrogen liquefaction cryogenic cold box in sequence. A supplementary precooling refrigerant pipeline is connected to the hydrogen liquefaction precooling cold box 101. Liquid nitrogen separated in an air rectification unit, liquid nitrogen separated by a gas-liquid separator, or liquid nitrogen output by a main heat exchange unit enters the hydrogen liquefaction precooling cold box, providing cooling capacity for the hydrogen liquefaction precooling cold box, thereby 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 and a hydrogen liquefaction precooling device for comprehensively utilizing LNG cold energy. 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 comprehensively utilizes LNG cold energy. In the present invention, liquid nitrogen separated in the air distillation unit, liquid nitrogen separated in the gas-liquid separator, or liquid nitrogen output from the main heat exchange unit enters 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 consumption of cold energy and equipment investment of the existing technology require a large amount of capital 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 and a hydrogen liquefaction precooling unit for comprehensively utilizing LNG cold energy, the system comprising:

[0006] A hydrogen liquefaction precooling device, comprising a hydrogen liquefaction precooling cold box and a hydrogen liquefaction cryogenic cold box, wherein the raw hydrogen pipeline passes through the hydrogen liquefaction precooling cold box and the hydrogen liquefaction cryogenic cold box in sequence, and the hydrogen liquefaction precooling cold box is connected to a supplementary precooling refrigerant pipeline;

[0007] An air separation device, comprising an air rectification tower, a main heat exchange unit, a nitrogen refrigeration unit, and a gas-liquid separator, wherein a feed air pipeline passes through the main heat exchange unit and is connected to the air rectification tower, and a first liquid nitrogen pipeline is provided on the air rectification tower;

[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, the first outlet of the nitrogen refrigeration unit is connected to the gas-liquid separator through a second pipeline, the liquid nitrogen outlet of the gas-liquid separator is connected to the first inlet of the main heat exchange unit through a liquid nitrogen branch pipeline, and the liquid nitrogen branch pipeline is connected to a second liquid nitrogen 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 a third liquid nitrogen pipeline;

[0010] The first liquid nitrogen pipeline, the second liquid nitrogen pipeline, or the third liquid nitrogen pipeline is connected to the hydrogen liquefaction cryogenic cold box.

[0011] Optionally, the main heat exchange unit includes an air pre-cooling heat exchanger, a main heat exchanger and a product heat exchanger;

[0012] The raw air pipeline passes through the air pre-cooling heat exchanger and the main heat exchanger;

[0013] The first nitrogen pipeline passes through the main heat exchanger;

[0014] The liquid nitrogen branch pipeline passes through the product heat exchanger and the main heat exchanger and is connected to the first pipeline;

[0015] The second nitrogen pipeline passes through the product heat exchanger and is connected to the third liquid nitrogen pipeline.

[0016] Optionally, the nitrogen refrigeration unit comprises a nitrogen refrigeration heat exchanger, a plurality of nitrogen compressors and an external refrigerant pipeline;

[0017] 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;

[0018] 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.

[0019] 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;

[0020] 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.

[0021] Optionally, the gas phase outlet of the gas-liquid separator is connected to a nitrogen branch pipeline, and the nitrogen branch pipeline passes through the main heat exchanger and is connected to the first pipeline.

[0022] Optionally, the first liquid nitrogen pipeline passes through the hydrogen liquefaction cryogenic cold box and is connected to the outlet of the second pipeline, and a throttle valve is provided on the first liquid nitrogen pipeline at a position between the cryogenic hydrogen liquefaction cryogenic cold box and the second pipeline.

[0023] Optionally, the second liquid nitrogen pipeline passes through the hydrogen liquefaction cryogenic cold box and is connected to the inlet of the first nitrogen pipeline.

[0024] Optionally, the third liquid nitrogen pipeline passes through the hydrogen liquefaction cryogenic cold box and is connected to the outlet of the second pipeline, and a throttle valve is provided on the first liquid nitrogen pipeline at a position between the cryogenic hydrogen liquefaction cryogenic cold box and the second pipeline.

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

[0026] The present invention provides a combined system of an air separation device and a hydrogen liquefaction precooling device that comprehensively utilizes LNG cold energy, and its beneficial effects are:

[0027] In the system, a first liquid nitrogen pipeline is provided on the air rectification tower, a liquid nitrogen branch pipeline is connected to a second liquid nitrogen pipeline, and a third liquid nitrogen pipeline is connected to the second outlet of the main heat exchange unit. Liquid nitrogen separated in the air rectification unit, liquid nitrogen separated in the gas-liquid separator, or liquid nitrogen output from the main heat exchange unit enters a hydrogen liquefaction pre-cooling cold box, providing cooling capacity for the hydrogen liquefaction pre-cooling cold box, thereby reducing the temperature of the raw hydrogen in the hydrogen liquefaction process, completing the pre-cooling stage of the raw hydrogen, effectively reducing the power consumption of the air separation unit and the hydrogen liquefaction unit, saving the number of refrigeration equipment, reducing equipment investment, reducing cooling energy loss, and improving energy utilization.

[0028] 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.

[0029] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] 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.

[0031] Figure 1 A schematic diagram of a combined system of an air separation unit and a hydrogen liquefaction pre-cooling unit for comprehensively utilizing LNG cold energy according to a first embodiment of the present invention is shown.

[0032] Figure 2 A schematic diagram of a combined system of an air separation device and a hydrogen liquefaction pre-cooling device for comprehensively utilizing LNG cold energy according to a second embodiment of the present invention is shown.

[0033] Figure 3 A schematic diagram of a combined system of an air separation unit and a hydrogen liquefaction pre-cooling unit for comprehensively utilizing LNG cold energy according to a third embodiment of the present invention is shown.

[0034] Figure 4 A schematic diagram of a main heat exchange unit according to embodiment one, two or three of the present invention is shown.

[0035] Figure 5 A schematic diagram of a nitrogen refrigeration unit according to Embodiment 1, 2 or 3 of the present invention is shown.

[0036] Description of reference numerals:

[0037] 101. Hydrogen liquefaction pre-cooling cold box; 102. Hydrogen liquefaction cryogenic cold box; 103. Air distillation tower; 104. Main heat exchange unit; 105. Nitrogen refrigeration unit; 106. Gas-liquid separator;

[0038] 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;

[0039] 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; 411, third liquid nitrogen pipeline; 412, supplementary pre-cooling refrigerant pipeline; 413, first liquid nitrogen pipeline; 414, second pipeline; 415, second liquid nitrogen pipeline. DETAILED DESCRIPTION

[0040] 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

[0041] like Figure 1 、 Figure 4 and Figure 5 As shown, the present invention provides a combined system of an air separation device and a hydrogen liquefaction precooling device for comprehensively utilizing LNG cold energy, the system comprising:

[0042] A hydrogen liquefaction precooling device includes a hydrogen liquefaction precooling cold box 101 and a hydrogen liquefaction cryogenic cold box 102. The raw hydrogen pipeline 410 passes through the hydrogen liquefaction precooling cold box 101 and the hydrogen liquefaction cryogenic cold box 102 in sequence. The hydrogen liquefaction precooling cold box 101 is connected to a supplementary precooling refrigerant pipeline 412.

[0043] An air separation unit includes an air rectification tower 103, a main heat exchange unit 104, a nitrogen refrigeration unit 105, and a gas-liquid separator 106. The raw air pipeline 402 passes through the main heat exchange unit 104 and is connected to the air rectification tower 103.

[0044] The first outlet of the main heat exchange unit 104 is connected to the first inlet of the nitrogen refrigeration unit 105 via a first pipeline 407. The first outlet of the nitrogen refrigeration unit is connected to the gas-liquid separator 106 via a second pipeline 414. The liquid nitrogen outlet of the gas-liquid separator 106 is connected to the first inlet of the main heat exchange unit 104 via a liquid nitrogen branch pipeline 404. The liquid nitrogen branch pipeline 404 is connected to a second liquid nitrogen pipeline 415.

[0045] The first nitrogen pipeline 401 of the air rectification tower 103 passes through the main heat exchange unit 104 and is connected to the first pipeline 407;

[0046] The second liquid nitrogen pipeline 415 is connected to the hydrogen liquefaction cryogenic cold box 102;

[0047] The second liquid nitrogen pipeline 415 passes through the hydrogen liquefaction cryogenic cold box 102 and is connected to the inlet of the first nitrogen pipeline 401 .

[0048] 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 105 is used to complete the refrigeration of nitrogen to produce low-temperature nitrogen, and the gas-liquid separator 106 is used to complete the separation of nitrogen and liquid nitrogen;

[0049] 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.

[0050] The second liquid nitrogen pipeline 415 is placed in the hydrogen liquefaction cryogenic cold box 102. The inlet of the second liquid nitrogen pipeline 415 is connected to the liquid nitrogen outlet of the gas-liquid separator 106 for transporting liquid nitrogen from the gas-liquid separator 106. The outlet of the second liquid nitrogen pipeline 415 is connected to the inlet of the first nitrogen pipeline 401. The liquid nitrogen releases cold energy in the hydrogen liquefaction cryogenic cold box 102, and the temperature rises to -163°C. It continues to enter the main heat exchange unit 104 as a refrigeration refrigerant. The supplementary pre-cooling refrigerant pipeline 412 is placed in the hydrogen liquefaction pre-cooling cold box 101 and transports LNG to provide cold energy for the hydrogen liquefaction pre-cooling cold box 101. The temperature of the LNG at the inlet of the supplementary pre-cooling refrigerant pipeline 412 is -160°C, and the temperature after heat exchange is 14°C.

[0051] The raw hydrogen pipeline 410 is placed in both the hydrogen liquefaction pre-cooling cold box 101 and the hydrogen liquefaction cryogenic cold box 102 for transporting raw hydrogen. After the raw hydrogen absorbs cold energy in the hydrogen liquefaction pre-cooling cold box 101, its temperature drops to -153°C. After absorbing cold energy in the hydrogen liquefaction cryogenic cold box 102, its temperature drops to -193°C.

[0052] In this embodiment, the main heat exchange unit 104 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 passes through the main heat exchanger 202;

[0055] The liquid nitrogen branch line 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 103. The raw air outlet temperature of the air pre-cooling heat exchanger 201 is -5°C, and the temperature is reduced to -171°C after passing through the main heat exchanger 202.

[0057] The liquid nitrogen branch line 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 106. The liquid nitrogen releases cold energy in the product heat exchanger 203 and the main heat exchanger 202.

[0058] The first nitrogen pipeline 401 is a low-pressure nitrogen pipeline, which is placed in the main heat exchanger 202 and is used to transport low-temperature nitrogen from the air distillation tower 102 to provide cooling 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 105 includes an intermediate heat exchanger 204 , a nitrogen refrigeration heat exchanger 205 , a plurality of nitrogen compressors 206 , 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 capacity for the nitrogen refrigeration heat exchanger.

[0061] The first pipeline 407 passes through the nitrogen refrigeration heat exchanger 205 and is connected to the second pipeline 414. The plurality of nitrogen compressors 206 are arranged in sequence and connected to the first pipeline 407. The portion of the first pipeline 407 between two adjacent nitrogen compressors 206 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 414 .

[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 -90°C. The temperature at the outlet of the external refrigerant line 408 is increased to 10°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 -10°C and the pressure is 0.40 MPa (A). After pressurization and cooling, the temperature is -158°C and the pressure is 7.2 MPa (A). A throttle valve is set at the outlet of the second pipeline 414. After throttling and pressure reduction, the temperature is -188°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 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, the gas phase outlet of the gas-liquid separator 106 is connected to a nitrogen branch pipeline 403 . The nitrogen branch pipeline 403 passes through the main heat exchanger 202 and is connected to the first pipeline 407 .

[0069] Specifically, the nitrogen branch line 403 is placed in the main heat exchanger 202 for conveying low-temperature nitrogen from the nitrogen refrigeration unit 105 to provide cooling in the main heat exchanger 202 . Example

[0070] 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 and a hydrogen liquefaction precooling device for comprehensively utilizing LNG cold energy, the system comprising:

[0071] A hydrogen liquefaction precooling device includes a hydrogen liquefaction precooling cold box 101 and a hydrogen liquefaction cryogenic cold box 102. The raw hydrogen pipeline 410 passes through the hydrogen liquefaction precooling cold box 101 and the hydrogen liquefaction cryogenic cold box 102 in sequence. The hydrogen liquefaction precooling cold box 101 is connected to a supplementary precooling refrigerant pipeline 412.

[0072] An air separation device includes an air rectification tower 103, a main heat exchange unit 104, a nitrogen refrigeration unit 105, and a gas-liquid separator 106. The raw air pipeline 402 passes through the main heat exchange unit 104 and is connected to the air rectification tower 103. The air rectification tower 103 is provided with a first liquid nitrogen pipeline 413.

[0073] The first outlet of the main heat exchange unit 104 is connected to the first inlet of the nitrogen refrigeration unit 105 through the first pipeline 407, the first outlet of the nitrogen refrigeration unit is connected to the gas-liquid separator 106 through the second pipeline 414, and the liquid nitrogen outlet of the gas-liquid separator 106 is connected to the first inlet of the main heat exchange unit 104 through the liquid nitrogen branch pipeline 404.

[0074] The first nitrogen pipeline 401 of the air rectification tower 103 passes through the main heat exchange unit 104 and is connected to the first pipeline 407;

[0075] The first liquid nitrogen pipeline 413 is connected to the hydrogen liquefaction cryogenic cold box 102;

[0076] The first liquid nitrogen pipeline 413 passes through the hydrogen liquefaction cryogenic cold box 102 and is connected to the outlet of the second pipeline 414 . A throttle valve is provided on the first liquid nitrogen pipeline 413 between the cryogenic hydrogen liquefaction cryogenic cold box 102 and the second pipeline 414 .

[0077] Specifically, the inlet of the first liquid nitrogen pipeline 413 is connected to the liquid nitrogen outlet of the air distillation tower 102, and is used to transport liquid nitrogen into the hydrogen liquefaction cryogenic cold box 102 to provide cooling capacity for the hydrogen liquefaction cryogenic cold box 102. The outlet of the first liquid nitrogen pipeline 413 is connected to the outlet of the second pipeline 414. A throttle valve is provided in the first liquid nitrogen pipeline 413 and located between the cryogenic hydrogen liquefaction cryogenic cold box 102 and the second pipeline 414. The low-temperature nitrogen from the hydrogen liquefaction cryogenic cold box 102 is further cooled after throttling, and is used as the refrigerant of the main heat exchange unit 104 after entering the gas-liquid separator 106. 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 and a hydrogen liquefaction precooling device for comprehensively utilizing LNG cold energy, the system comprising:

[0079] A hydrogen liquefaction precooling device includes a hydrogen liquefaction precooling cold box 101 and a hydrogen liquefaction cryogenic cold box 102. The raw hydrogen pipeline 410 passes through the hydrogen liquefaction precooling cold box 101 and the hydrogen liquefaction cryogenic cold box 102 in sequence. The hydrogen liquefaction precooling cold box 101 is connected to a supplementary precooling refrigerant pipeline 412.

[0080] An air separation unit includes an air rectification tower 103, a main heat exchange unit 104, a nitrogen refrigeration unit 105, and a gas-liquid separator 106. The raw air pipeline 402 passes through the main heat exchange unit 104 and is connected to the air rectification tower 103.

[0081] The first outlet of the main heat exchange unit 104 is connected to the first inlet of the nitrogen refrigeration unit 105 through the first pipeline 407, the first outlet of the nitrogen refrigeration unit is connected to the gas-liquid separator 106 through the second pipeline 414, and the liquid nitrogen outlet of the gas-liquid separator 106 is connected to the first inlet of the main heat exchange unit 104 through the liquid nitrogen branch pipeline 404.

[0082] The first nitrogen pipeline 401 of the air rectification tower 103 passes through the main heat exchange unit 104 and is connected to the first pipeline 407. The second nitrogen pipeline 406 of the air rectification tower 103 is connected to the second inlet of the main heat exchange unit 104. The second outlet of the main heat exchange unit 104 is connected to the third liquid nitrogen pipeline 411.

[0083] The third liquid nitrogen pipeline 411 is connected to the hydrogen liquefaction cryogenic cold box 102;

[0084] The second nitrogen pipeline 406 passes through the product heat exchanger 203 and is connected to the third liquid nitrogen pipeline 411;

[0085] The third liquid nitrogen pipeline 411 passes through the hydrogen liquefaction cryogenic cold box 102 and is connected to the outlet of the second pipeline 414 . A throttle valve is provided on the first liquid nitrogen pipeline 413 between the cryogenic hydrogen liquefaction cryogenic cold box 102 and the second pipeline 414 .

[0086] Specifically, the second nitrogen pipeline 406 is placed in the product heat exchanger 203 of the main heat exchange unit 103, and generates liquid nitrogen after absorbing cold energy and enters the third liquid nitrogen pipeline 411. Since the third liquid nitrogen pipeline 411 passes through the hydrogen liquefaction cryogenic cold box 102, it provides cold energy for the cryogenic hydrogen liquefaction cryogenic cold box 102. The outlet of the third liquid nitrogen pipeline 411 is connected to the outlet of the second pipeline 414. A throttle valve is provided in the first liquid nitrogen pipeline 413 and located between the cryogenic hydrogen liquefaction cryogenic cold box 102 and the second pipeline 414. The low-temperature nitrogen from the cryogenic hydrogen liquefaction cryogenic cold box 102 is further reduced in temperature after throttling, and is used as the refrigerant of the main heat exchange unit 104 after entering the gas-liquid separator 106.

[0087] 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 and a hydrogen liquefaction pre-cooling unit for comprehensive utilization of LNG cold energy, characterized in that: The system includes: A hydrogen liquefaction precooling device, comprising a hydrogen liquefaction precooling cold box and a hydrogen liquefaction cryogenic cold box, wherein the raw hydrogen pipeline passes through the hydrogen liquefaction precooling cold box and the hydrogen liquefaction cryogenic cold box in sequence, and the hydrogen liquefaction precooling cold box is connected to a supplementary precooling refrigerant pipeline; An air separation device, the air separation device comprising an air rectification tower, a main heat exchange unit, a nitrogen refrigeration unit and a gas-liquid separator, wherein a feed air pipeline passes through the main heat exchange unit and is connected to the air rectification tower, a first liquid nitrogen pipeline is provided on the air rectification tower, and the nitrogen refrigeration unit comprises a nitrogen refrigeration heat exchanger, multiple nitrogen compressors and an external refrigerant 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, the first outlet of the nitrogen refrigeration unit is connected to the gas-liquid separator through a second pipeline, the liquid nitrogen outlet of the gas-liquid separator is connected to the first inlet of the main heat exchange unit through a liquid nitrogen branch pipeline, and the liquid nitrogen branch pipeline is connected to a second liquid nitrogen 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 a third liquid nitrogen pipeline; The first liquid nitrogen pipeline, the second liquid nitrogen pipeline, or the third liquid nitrogen pipeline is connected to the hydrogen liquefaction cryogenic cold box; 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 passes through the main heat exchanger; The liquid nitrogen branch pipeline passes through the product heat exchanger and the main heat exchanger and is connected to the first pipeline; The second nitrogen pipeline passes through the product heat exchanger and is connected to the third liquid nitrogen pipeline; a first intermediate heat exchange medium heat absorbing pipeline and a second intermediate heat exchange medium heat absorbing pipeline, the nitrogen refrigeration unit further comprising 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 both ends of the first intermediate heat exchange medium heat absorption pipeline are respectively connected to both ends of the second intermediate heat exchange medium heat absorption pipeline; The gas phase outlet of the gas-liquid separator is connected to a nitrogen branch pipeline, and the nitrogen branch pipeline passes through the main heat exchanger and is connected to the first pipeline.

2. The combined system of an air separation unit and a hydrogen liquefaction pre-cooling unit for comprehensive utilization of LNG cold energy according to claim 1 is characterized in that: 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 and a hydrogen liquefaction pre-cooling unit for comprehensive utilization of LNG cold energy according to claim 1 is characterized in that: The first liquid nitrogen pipeline passes through the hydrogen liquefaction cryogenic cold box and is connected to the outlet of the second pipeline. A throttle valve is provided on the first liquid nitrogen pipeline at a position between the cryogenic hydrogen liquefaction cryogenic cold box and the second pipeline.

4. The combined system of an air separation unit and a hydrogen liquefaction pre-cooling unit for comprehensive utilization of LNG cold energy according to claim 1 is characterized in that: The second liquid nitrogen pipeline passes through the hydrogen liquefaction cryogenic cold box and is connected to the inlet of the first nitrogen pipeline.

5. The combined system of an air separation unit and a hydrogen liquefaction pre-cooling unit for comprehensive utilization of LNG cold energy according to claim 1 is characterized in that: The third liquid nitrogen pipeline passes through the hydrogen liquefaction cryogenic cold box and is connected to the outlet of the second pipeline. The first liquid nitrogen pipeline is provided with a throttle valve at a position between the cryogenic hydrogen liquefaction cryogenic cold box and the second pipeline.

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

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