A combined air separation and hydrogen liquefaction pre-cooling system based on nitrogen cycle refrigeration

Abstract

The present invention provides an air separation and hydrogen liquefaction pre-cooling combined system based on nitrogen circulation refrigeration, belonging to the field of nitrogen circulation refrigeration. The system comprises: a hydrogen liquefaction pre-cooling device, the hydrogen liquefaction pre-cooling device comprising a hydrogen liquefaction pre-cooling cold box, wherein a raw hydrogen pipeline is arranged in the hydrogen liquefaction pre-cooling 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 raw air pipeline passing through the main heat exchange unit and connected to the air rectification tower; the air rectification tower is used to complete air separation, and the low-temperature nitrogen generated by the air rectification tower is transported into a circulation pipeline formed by the main heat exchange unit and the nitrogen refrigeration unit, thereby 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 cold 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 an air separation and hydrogen liquefaction pre-cooling combined system based on nitrogen cycle refrigeration. 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 an air separation and hydrogen liquefaction pre-cooling combined system based on nitrogen circulation refrigeration. The present invention adopts a nitrogen refrigeration unit to process high-temperature, low-pressure nitrogen to produce low-temperature nitrogen and liquid nitrogen, while providing cooling capacity for the main heat exchange unit and 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] In order to achieve the above object, the present invention provides an air separation and hydrogen liquefaction pre-cooling combined system based on nitrogen cycle refrigeration, the system comprising:

[0006] A hydrogen liquefaction precooling device, comprising a hydrogen liquefaction precooling cold box, wherein a raw hydrogen pipeline is provided in the hydrogen liquefaction precooling cold box;

[0007] An air separation unit, the 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;

[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 a second pipeline, and the nitrogen pipeline in the air rectification tower passes through the main heat exchange unit and is connected to the first pipeline;

[0009] When the second pipeline is directly connected to the main heat exchange unit, the second pipeline is connected to the first inlet and the second inlet of the main heat exchange unit through the third pipeline and the fourth pipeline respectively, a first nitrogen circulation pipeline branch is provided on the second pipeline, a product liquid nitrogen pipeline is provided on the second outlet of the main heat exchange unit, and the product liquid nitrogen pipeline is connected to the second nitrogen circulation pipeline branch;

[0010] When 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 liquid nitrogen branch pipeline is connected to a third nitrogen circulation pipeline branch, and the nitrogen branch pipeline is connected to a fourth nitrogen circulation pipeline branch;

[0011] The first nitrogen circulation pipeline branch, the second nitrogen circulation pipeline branch, the third nitrogen circulation pipeline branch or the fourth nitrogen circulation pipeline branch is connected to the hydrogen liquefaction pre-cooling cold box.

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

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

[0014] The nitrogen pipeline in the tower passes through the first product heat exchanger and the first main heat exchanger;

[0015] The third pipeline passes through the first main heat exchanger and is connected to the first pipeline;

[0016] The fourth pipeline passes through the first product heat exchanger and is connected to the product liquid nitrogen pipeline;

[0017] The first nitrogen circulation pipeline branch or the second nitrogen circulation pipeline branch passes through the hydrogen liquefaction pre-cooling cold box and is connected to the first pipeline.

[0018] Optionally, the main heat exchange unit includes a second air pre-cooling heat exchanger, a second main heat exchanger and a second product heat exchanger;

[0019] The raw air pipeline passes through the second air pre-cooling heat exchanger and the second main heat exchanger;

[0020] The nitrogen pipeline in the tower and the nitrogen branch pipeline both pass through the second main heat exchanger and are connected to the first pipeline;

[0021] The first product pipeline in the air rectification tower passes through the second product heat exchanger and is connected to the first pipeline;

[0022] The liquid nitrogen branch pipeline passes through the second product heat exchanger and the second main heat exchanger and is connected to the first pipeline;

[0023] The third nitrogen circulation pipeline branch or the fourth nitrogen circulation pipeline branch passes through the hydrogen liquefaction pre-cooling cold box and is connected to the first pipeline.

[0024] Optionally, the nitrogen refrigeration unit comprises a nitrogen refrigeration heat exchanger, a plurality of nitrogen compressors and an external refrigerant pipeline;

[0025] 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;

[0026] 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.

[0027] 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;

[0028] 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 first air precooling heat exchanger or the second air precooling 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.

[0029] Optionally, the hydrogen liquefaction precooling device further includes a circulating refrigerant precooling pipeline, and the circulating refrigerant precooling pipeline passes through the hydrogen liquefaction precooling cold box.

[0030] Optionally, when the fourth nitrogen circulation pipeline branch is connected to the hydrogen liquefaction pre-cooling box, the hydrogen liquefaction pre-cooling device also includes a pre-cooling refrigerant pipeline, which passes through the hydrogen liquefaction pre-cooling box and is connected to the LNG receiving station. The pre-cooling refrigerant pipeline is used to transport LNG to provide cooling capacity for the hydrogen liquefaction pre-cooling box.

[0031] Optionally, the first product pipeline and the second product pipeline in the air rectification tower both pass through the first product heat exchanger.

[0032] Optionally, the dirty nitrogen pipeline in the air rectification tower passes through the first product heat exchanger and the first main heat exchanger in sequence and is connected to the first pipeline.

[0033] Optionally, a throttle valve is connected to the second pipeline.

[0034] The present invention provides an air separation and hydrogen liquefaction pre-cooling combined system based on nitrogen cycle refrigeration, which has the following beneficial effects:

[0035] 1. In the present invention, an air distillation tower is used to separate air. The low-temperature nitrogen generated by the air distillation tower is transported to a circulation pipeline formed by a main heat exchange unit, a nitrogen refrigeration unit, and a gas-liquid separator. The nitrogen refrigeration unit is used to process the high-temperature, low-pressure nitrogen to produce low-temperature nitrogen and liquid nitrogen. At the same time, it provides cooling capacity for the main heat exchange unit and the hydrogen liquefaction pre-cooling cold box, lowering 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, and reducing the amount of cooling energy loss, thereby improving energy utilization.

[0036] 2. The present invention is particularly suitable for application 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.

[0037] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] 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.

[0039] Figure 1 A schematic diagram of an air separation and hydrogen liquefaction pre-cooling combined system based on nitrogen cycle refrigeration according to embodiment 1 of the present invention is shown.

[0040] Figure 2 A schematic diagram of an air separation and hydrogen liquefaction pre-cooling combined system based on nitrogen cycle refrigeration according to a second embodiment of the present invention is shown.

[0041] Figure 3 A schematic diagram of an air separation and hydrogen liquefaction pre-cooling combined system based on nitrogen cycle refrigeration according to embodiment 3 of the present invention is shown.

[0042] Figure 4 A schematic diagram of an air separation and hydrogen liquefaction pre-cooling combined system based on nitrogen cycle refrigeration according to a fourth embodiment of the present invention is shown.

[0043] Figure 5 A schematic diagram of a main heat exchange unit according to embodiment 1 or 2 of the present invention is shown.

[0044] Figure 6 A schematic diagram of another main heat exchange unit according to the third or fourth embodiment of the present invention is shown.

[0045] Figure 7 A schematic diagram of a nitrogen refrigeration unit according to embodiment one, two, three or four of the present invention is shown.

[0046] Description of reference numerals:

[0047] 101. Hydrogen liquefaction pre-cooling cold box; 102. Air distillation tower; 103. Main heat exchange unit; 104. Nitrogen refrigeration unit; 105. Gas-liquid separator;

[0048] 201, air pre-cooling heat exchanger; 202, first main heat exchanger; 203, first product heat exchanger; 204, intermediate heat exchanger; 205, nitrogen refrigeration heat exchanger; 206, nitrogen compressor; 207, second air pre-cooling heat exchanger; 208, second main heat exchanger; 209, second product heat exchanger;

[0049] 401. Nitrogen pipeline in the tower; 402. Raw air pipeline; 403. Nitrogen branch pipeline; 404. Liquid nitrogen branch pipeline; 405. First intermediate heat exchange medium heat absorption pipeline; 406. First product pipeline in the tower; 407. First pipeline; 408. External refrigerant pipeline; 409. Second intermediate heat exchange medium heat absorption pipeline; 410. Raw hydrogen pipeline; 412. Pre-cooling refrigerant pipeline; 413. Pre-cooling circulating refrigerant pipeline; 414. Second product pipeline in the tower; 415. Product liquid nitrogen pipeline; 416. Low-temperature dirty nitrogen pipeline in the tower; 417. Third pipeline; 418. Fourth pipeline; 419. Second pipeline; 420. First nitrogen circulation pipeline branch; 421. Second nitrogen circulation pipeline branch; 422. Third nitrogen circulation pipeline branch; 423. Fourth nitrogen circulation pipeline branch. DETAILED DESCRIPTION

[0050] 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.

[0051] Example 1

[0052] like Figure 1 、 Figure 5 and Figure 7 As shown, the present invention provides an air separation and hydrogen liquefaction pre-cooling combined system based on nitrogen cycle refrigeration, the system comprising:

[0053] A hydrogen liquefaction precooling device, comprising a hydrogen liquefaction precooling cold box 101, wherein a raw hydrogen pipeline 410 is provided in the hydrogen liquefaction precooling cold box 101;

[0054] An air separation unit includes an air rectification tower 102, a main heat exchange unit 103, and a nitrogen refrigeration unit 104. The feed air pipeline 402 passes through the main heat exchange unit 103 and is connected to the air rectification tower 102.

[0055] The first outlet of the main heat exchange unit 103 is connected to the first inlet of the nitrogen refrigeration unit 104 via a first pipeline 407. The first outlet of the nitrogen refrigeration unit 104 is connected to a second pipeline 419. The nitrogen pipeline 401 in the air rectification tower 102 passes through the main heat exchange unit 103 and is connected to the first pipeline 407.

[0056] The second pipeline 419 is directly connected to the main heat exchange unit 103. The second pipeline 419 is connected to the first inlet and the second inlet of the main heat exchange unit 103 through the third pipeline 417 and the fourth pipeline 418 respectively. The second pipeline 419 is provided with a first nitrogen circulation pipeline branch 420. The second outlet of the main heat exchange unit 103 is provided with a product liquid nitrogen pipeline 415.

[0057] The first nitrogen circulation pipeline branch 420 is connected to the hydrogen liquefaction pre-cooling cold box 101;

[0058] The first nitrogen circulation pipeline branch 420 passes through the hydrogen liquefaction pre-cooling cold box 101 and is connected to the first pipeline 407 .

[0059] Specifically, the hydrogen liquefaction pre-cooling cold box 101 is used to provide cooling 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 air separation, the main heat exchange unit 103 is used to provide cooling for the air distillation tower 102 and the raw air, and the nitrogen refrigeration unit 104 is used to complete the refrigeration of nitrogen to produce low-temperature nitrogen;

[0060] 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 0.8MPa(A) and a temperature of 25°C.

[0061] The first nitrogen circulation pipeline branch 420 is placed in the pre-cooling cold box 101. The inlet of the first nitrogen circulation pipeline branch 420 is connected to the second pipeline 419 and is used to transport low-temperature nitrogen from the nitrogen refrigeration unit 104. The outlet of the first nitrogen circulation pipeline branch 420 is connected to the first pipeline 407. The low-temperature nitrogen releases cold energy in the hydrogen liquefaction pre-cooling cold box 101, and the temperature rises to 17°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 the cold energy, its temperature drops to -183°C.

[0062] In this embodiment, the main heat exchange unit 103 includes a first air pre-cooling heat exchanger 201, a first main heat exchanger 202 and a first product heat exchanger 203;

[0063] The raw air pipeline 402 passes through the first air pre-cooling heat exchanger 201 and the first main heat exchanger 202;

[0064] The nitrogen pipeline 401 in the tower passes through the first product heat exchanger 203 and the first main heat exchanger 202;

[0065] The third pipeline 417 passes through the first main heat exchanger 202 and is connected to the first pipeline 407;

[0066] The fourth pipeline 418 passes through the first product heat exchanger 203 and is connected to the product liquid nitrogen pipeline 415;

[0067] The first nitrogen circulation pipeline branch 420 passes through the hydrogen liquefaction pre-cooling cold box 101 and is connected to the first pipeline 407;

[0068] The first product pipeline 406 and the second product pipeline 414 of the air rectification tower 102 both pass through the first product heat exchanger 203;

[0069] The contaminated nitrogen pipeline 416 in the air rectification tower 102 passes through the first product heat exchanger 203 and the first main heat exchanger 202 in sequence and is connected to the first pipeline 407 .

[0070] Specifically, the raw air pipeline 402 is placed in the first air pre-cooling heat exchanger 201 and the first main heat exchanger 202, 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 -5°C, and the temperature drops to -171°C after passing through the first main heat exchanger 202.

[0071] The nitrogen pipeline 401 in the tower and the waste nitrogen pipeline 416 in the tower are successively placed in the first product heat exchanger 203 and the first main heat exchanger 202, and are used to transport low-temperature nitrogen and low-temperature waste nitrogen from the air distillation tower 102, and release cold energy in the first product heat exchanger 203 and the first main heat exchanger 202. The waste nitrogen is a mixture of nitrogen, argon and oxygen rich in nitrogen;

[0072] The third pipeline 417 is placed in the first main heat exchanger 202, and the inlet of the third pipeline 417 is connected to the second pipeline 419, and is used to transport the low-temperature nitrogen of the nitrogen refrigeration unit 104 into the first main heat exchanger 202 to provide cooling capacity. The first pipeline 406 of the tower product and the second pipeline 414 of the tower product are both placed in the first product heat exchanger 203, and the inlets of the first pipeline 406 of the tower product and the second pipeline 414 of the tower product are both connected to the air distillation tower 102, and are used to transport liquid oxygen and liquid air into the first product exchanger. The heat exchanger 203 absorbs cold energy to generate liquid oxygen product for delivery and cryogenic liquid air for entry into the air rectification column 102. The fourth pipeline 418 is placed in the product heat exchanger 203. The inlet of the fourth pipeline 418 is connected to the outlet of the second pipeline 419. The outlet of the fourth pipeline 418 is connected to the product liquid nitrogen pipeline 415. The fourth pipeline 418 is used to transport cryogenic nitrogen from the nitrogen refrigeration unit 104 into the first product heat exchanger 203 to absorb cold energy, further reduce the temperature, generate product liquid nitrogen, and deliver it through the outlet of the product liquid nitrogen pipeline 415.

[0073] In this embodiment, the nitrogen refrigeration unit 104 includes a nitrogen refrigeration heat exchanger 205 , a plurality of nitrogen compressors 206 , and an external refrigerant line 408 ;

[0074] The external refrigerant pipeline 408 passes through the nitrogen refrigeration heat exchanger 205 and is connected to the LNG receiving station. The external refrigerant pipeline 408 is used to transport LNG to provide cooling for the nitrogen refrigeration heat exchanger 205.

[0075] The first pipeline 407 passes through the nitrogen refrigeration heat exchanger 205 and is connected to the second pipeline 419. 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.

[0076] The number of the nitrogen compressors 206 is three;

[0077] A throttle valve is connected to the second pipeline 419 .

[0078] Specifically, the external refrigerant line 408 is placed in the nitrogen refrigeration heat exchanger 205 to transport LNG and release cold energy. The temperature of the LNG at the inlet of the external refrigerant line 408 is -160°C. After heat exchange in the nitrogen refrigeration heat exchanger 205, the temperature is -87°C. The temperature at the outlet of the external refrigerant line 408 is increased to 0°C. It can be connected to the natural gas transmission system to transmit the reheated natural gas.

[0079] According to the direction of logistics flow, 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. After three pressurization and cooling, the nitrogen temperature at the inlet of the first pipeline 407 is 0°C and the pressure is 0.38 MPa(A). After pressurization and cooling, the temperature is -155°C and the pressure is 5.8 MPa(A). A throttle valve is set at the outlet of the second pipeline 419. After throttling and pressure reduction, the temperature drops to -180°C.

[0080] In this embodiment, the system further includes a first intermediate heat exchange medium heat absorbing pipeline 405 and a second intermediate heat exchange medium heat absorbing pipeline 409 , and the nitrogen refrigeration unit 104 further includes an intermediate heat exchanger 204 ;

[0081] 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 first air pre-cooling heat exchanger 201, and the two ends of the first intermediate heat exchange medium heat absorption pipeline 405 are respectively connected to the two ends of the second intermediate heat exchange medium heat absorption pipeline 409.

[0082] Specifically, 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 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 to transport ethylene glycol to release cold energy and reduce the temperature of the raw air.

[0083] In this embodiment, the hydrogen liquefaction precooling device further includes a circulating refrigerant precooling pipeline 413 , and the circulating refrigerant precooling pipeline 413 passes through the hydrogen liquefaction precooling cold box 101 .

[0084] Specifically, the hydrogen liquefaction pre-cooling cold box 101 also provides cooling capacity for the circulating refrigerant in the hydrogen liquefaction process, wherein the circulating refrigerant is circulated in the hydrogen liquefaction process to provide cooling capacity for the raw hydrogen.

[0085] Example 2

[0086] like Figure 2 、 Figure 5 and Figure 7 As shown, the difference between Example 2 and Example 1 is that: an air separation and hydrogen liquefaction pre-cooling combined system based on nitrogen cycle refrigeration, the system includes:

[0087] A hydrogen liquefaction precooling device, comprising a hydrogen liquefaction precooling cold box 101, wherein a raw hydrogen pipeline 410 is provided in the hydrogen liquefaction precooling cold box 101;

[0088] An air separation unit includes an air rectification tower 102, a main heat exchange unit 103, and a nitrogen refrigeration unit 104. The feed air pipeline 402 passes through the main heat exchange unit 103 and is connected to the air rectification tower 102.

[0089] The first outlet of the main heat exchange unit 103 is connected to the first inlet of the nitrogen refrigeration unit 104 via a first pipeline 407. The first outlet of the nitrogen refrigeration unit 104 is connected to a second pipeline 419. The nitrogen pipeline 401 in the air rectification tower 102 passes through the main heat exchange unit 103 and is connected to the first pipeline 407.

[0090] The second pipeline 419 is directly connected to the main heat exchange unit 103. The second pipeline 419 is connected to the first inlet and the second inlet of the main heat exchange unit 103 through the third pipeline 417 and the fourth pipeline 418 respectively. The second outlet of the main heat exchange unit 103 is provided with a product liquid nitrogen pipeline 415, and the product liquid nitrogen pipeline 415 is connected to the second nitrogen circulation pipeline branch 421.

[0091] The second nitrogen circulation pipeline branch 421 is connected to the hydrogen liquefaction pre-cooling cold box 101;

[0092] The second nitrogen circulation pipeline branch 421 passes through the hydrogen liquefaction pre-cooling cold box 101 and is connected to the first pipeline 407 .

[0093] Specifically, the inlet of the second nitrogen circulation pipeline branch 421 is connected to the outlet of the product liquid nitrogen pipeline 415, which is used to transport liquid nitrogen into the hydrogen liquefaction pre-cooling cold box 101 to provide cooling capacity for the hydrogen liquefaction pre-cooling cold box 101. 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 the cooling capacity, the temperature of the raw hydrogen decreases.

[0094] Example 3

[0095] like Figure 3 、 Figure 6 and Figure 7 As shown, the present invention provides an air separation and hydrogen liquefaction pre-cooling combined system based on nitrogen cycle refrigeration, the system comprising:

[0096] A hydrogen liquefaction precooling device, comprising a hydrogen liquefaction precooling cold box 101, wherein a raw hydrogen pipeline 410 is provided in the hydrogen liquefaction precooling cold box 101;

[0097] An air separation unit includes an air rectification tower 102, a main heat exchange unit 103, and a nitrogen refrigeration unit 104. The feed air pipeline 402 passes through the main heat exchange unit 103 and is connected to the air rectification tower 102.

[0098] The first outlet of the main heat exchange unit 103 is connected to the first inlet of the nitrogen refrigeration unit 104 via a first pipeline 407. The first outlet of the nitrogen refrigeration unit 104 is connected to a second pipeline 419. The nitrogen pipeline 401 in the air rectification tower 102 passes through the main heat exchange unit 103 and is connected to the first pipeline 407.

[0099] The second pipeline 419 is provided with a gas-liquid separator 105. 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. 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. The liquid nitrogen branch pipeline 404 is connected to a third nitrogen circulation pipeline branch 422.

[0100] The third nitrogen circulation pipeline branch 422 is connected to the hydrogen liquefaction pre-cooling cold box 101;

[0101] The third nitrogen circulation pipeline branch 422 passes through the hydrogen liquefaction pre-cooling cold box 101 and is connected to the first pipeline 407 .

[0102] 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, and the gas-liquid separator 105 is used to complete the separation of nitrogen and liquid nitrogen;

[0103] 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 0.8MPa(A) and a temperature of 25°C.

[0104] The third nitrogen circulation pipeline branch 422 is placed in the pre-cooling cold box 101. The inlet of the third nitrogen circulation pipeline branch 422 is connected to the liquid nitrogen branch pipeline 404 and is used to transport liquid nitrogen from the gas-liquid separator 105. The outlet of the third nitrogen circulation pipeline branch 422 is connected to the first pipeline 407. The liquid nitrogen releases cold energy in the hydrogen liquefaction pre-cooling cold box 101, and the temperature rises to -8°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 the cold energy, the temperature drops to -191°C.

[0105] In this embodiment, the main heat exchange unit 103 includes a second air pre-cooling heat exchanger 207, a second main heat exchanger 208, and a second product heat exchanger 209;

[0106] The raw air line 402 passes through the second air pre-cooling heat exchanger 207 and the second main heat exchanger 208;

[0107] The nitrogen pipeline 401 and the nitrogen branch pipeline 403 in the tower both pass through the second main heat exchanger 103 and are connected to the first pipeline 407;

[0108] The first product pipeline 406 of the air rectification tower 102 passes through the second product heat exchanger 209 and is connected to the first pipeline 407;

[0109] The liquid nitrogen branch line 404 passes through the second product heat exchanger 209 and the second main heat exchanger 208 and is connected to the first line 407;

[0110] Specifically, the raw air pipeline 402 is placed in the second air pre-cooling heat exchanger 207 and the second main heat exchanger 208 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 has a temperature of -5°C at the outlet of the air pre-cooling heat exchanger 201, and is reduced to -171°C after passing through the second main heat exchanger 208.

[0111] The liquid nitrogen branch line 404 is placed in the second product heat exchanger 209 and the second main heat exchanger 208 in sequence, and is used to transport liquid nitrogen from the gas-liquid separator 105 and release cold energy in the second product heat exchanger 209 and the second main heat exchanger 208. The first tower product line 406 is placed in the second product heat exchanger 209. The inlet of the first tower product line 406 is connected to the air rectification column 102. It is used to transport liquid oxygen into the second product heat exchanger 209 to absorb cold energy and further deep-cool it to produce liquid oxygen product, which is then delivered through the outlet of the first tower product line 406.

[0112] The nitrogen pipeline 401 and the nitrogen branch pipeline 403 in the tower are both placed in the second main heat exchanger 208, and are used to transport low-temperature nitrogen from the gas-liquid separator 105 and low-temperature nitrogen from the air distillation tower 102 respectively, providing cooling capacity in the second main heat exchanger 208.

[0113] In this embodiment, the nitrogen refrigeration unit 104 includes a nitrogen refrigeration heat exchanger 205 , a plurality of nitrogen compressors, and an external refrigerant line 408 ;

[0114] The external refrigerant pipeline 408 passes through the nitrogen refrigeration heat exchanger 205 and is connected to the LNG receiving station. The external refrigerant pipeline 408 is used to transport LNG to provide cooling for the nitrogen refrigeration heat exchanger 205.

[0115] The first pipeline 407 passes through the nitrogen refrigeration heat exchanger 205 and is connected to the second pipeline 419. 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 passes through the nitrogen refrigeration heat exchanger 205.

[0116] The number of the nitrogen compressors 206 is three;

[0117] A throttle valve is connected to the second pipeline 419 .

[0118] 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 0°C. The LNG can be connected to the natural gas transmission system to transmit the reheated natural gas.

[0119] According to the direction of logistics flow, 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. After three pressurization and cooling, the nitrogen temperature at the inlet of the first pipeline 407 is -10°C and the pressure is 0.38 MPa(A). After pressurization and cooling, the temperature is -155°C and the pressure is 5.8 MPa(A). A throttle valve is set at the outlet of the second pipeline 419. After throttling and pressure reduction, the temperature drops to -180°C.

[0120] In this embodiment, the system further includes a first intermediate heat exchange medium heat absorbing pipeline 405 and a second intermediate heat exchange medium heat absorbing pipeline 409 , and the nitrogen refrigeration unit 104 further includes an intermediate heat exchanger 204 ;

[0121] 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 second air pre-cooling heat exchanger 207, and the two ends of the first intermediate heat exchange medium heat absorption pipeline 405 are respectively connected to the two ends of the second intermediate heat exchange medium heat absorption pipeline 409.

[0122] Specifically, 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 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 to transport ethylene glycol to release cold energy and reduce the temperature of the raw air.

[0123] Example 4

[0124] like Figure 4 、 Figure 6 and Figure 7 As shown, the difference between the fourth embodiment and the third embodiment is:

[0125] A combined air separation and hydrogen liquefaction precooling system based on nitrogen cycle refrigeration, the system comprising: a hydrogen liquefaction precooling device, the hydrogen liquefaction precooling device comprising a hydrogen liquefaction precooling cold box 101, a raw hydrogen pipeline 410 being provided in the hydrogen liquefaction precooling cold box 101;

[0126] An air separation unit includes an air rectification tower 102, a main heat exchange unit 103, and a nitrogen refrigeration unit 104. The feed air pipeline 402 passes through the main heat exchange unit 103 and is connected to the air rectification tower 102.

[0127] The first outlet of the main heat exchange unit 103 is connected to the first inlet of the nitrogen refrigeration unit 104 via a first pipeline 407. The first outlet of the nitrogen refrigeration unit 104 is connected to a second pipeline 419. The nitrogen pipeline 401 in the air rectification tower 102 passes through the main heat exchange unit 103 and is connected to the first pipeline 407.

[0128] The second pipeline 419 is provided with a gas-liquid separator 105. 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. 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. The nitrogen branch pipeline 403 is connected to a fourth nitrogen circulation pipeline branch 423.

[0129] The fourth nitrogen circulation pipeline branch 423 is connected to the hydrogen liquefaction pre-cooling cold box 101;

[0130] The fourth nitrogen circulation pipeline branch 423 passes through the hydrogen liquefaction pre-cooling cold box 101 and is connected to the first pipeline 407 .

[0131] Specifically, the fourth nitrogen circulation pipeline branch 423 is placed in the pre-cooling cold box 101, and the inlet of the fourth nitrogen circulation pipeline branch 423 is connected to the nitrogen branch pipeline 403, and is used to transport low-temperature nitrogen from the gas-liquid separator 105 into the pre-cooling cold box 101 to provide cooling for the pre-cooling cold box 101. 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 cooling, the temperature drops.

[0132] 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.

[0133] Specifically, the inlet temperature of LNG in the hydrogen liquefaction pre-cooling cold box is -160°C, and the outlet temperature is 10°C, realizing the recovery and utilization of LNG cold energy.

[0134] 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 air separation and hydrogen liquefaction pre-cooling system based on nitrogen cycle refrigeration, characterized in that: The system includes: A hydrogen liquefaction precooling device, comprising a hydrogen liquefaction precooling cold box, wherein a raw hydrogen pipeline is provided in the hydrogen liquefaction precooling cold box; An air separation unit, the 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; 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 a second pipeline, and the nitrogen pipeline in the air rectification tower passes through the main heat exchange unit and is connected to the first pipeline; When the second pipeline is directly connected to the main heat exchange unit, the second pipeline is connected to the first inlet and the second inlet of the main heat exchange unit through the third pipeline and the fourth pipeline respectively, a first nitrogen circulation pipeline branch is provided on the second pipeline, a product liquid nitrogen pipeline is provided on the second outlet of the main heat exchange unit, and the product liquid nitrogen pipeline is connected to the second nitrogen circulation pipeline branch; When 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 liquid nitrogen branch pipeline is connected to a third nitrogen circulation pipeline branch, and the nitrogen branch pipeline is connected to a fourth nitrogen circulation pipeline branch; The first nitrogen circulation pipeline branch, the second nitrogen circulation pipeline branch, the third nitrogen circulation pipeline branch, or the fourth nitrogen circulation pipeline branch is connected to the hydrogen liquefaction pre-cooling cold box; 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 plurality of 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. It also includes a first intermediate heat exchange medium heat absorption pipeline and a second intermediate heat exchange medium heat absorption pipeline, and the nitrogen refrigeration unit also includes 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 first air precooling heat exchanger or the second air precooling 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.

2. The combined air separation and hydrogen liquefaction pre-cooling system based on nitrogen cycle refrigeration according to claim 1 is characterized in that: The main heat exchange unit includes a first air pre-cooling heat exchanger, a first main heat exchanger and a first product heat exchanger; The raw air pipeline passes through the first air pre-cooling heat exchanger and the first main heat exchanger; The nitrogen pipeline in the tower passes through the first product heat exchanger and the first main heat exchanger; The third pipeline passes through the first main heat exchanger and is connected to the first pipeline; The fourth pipeline passes through the first product heat exchanger and is connected to the product liquid nitrogen pipeline; The first nitrogen circulation pipeline branch or the second nitrogen circulation pipeline branch passes through the hydrogen liquefaction pre-cooling cold box and is connected to the first pipeline.

3. The combined air separation and hydrogen liquefaction pre-cooling system based on nitrogen cycle refrigeration according to claim 1 is characterized in that: The main heat exchange unit includes a second air pre-cooling heat exchanger, a second main heat exchanger and a second product heat exchanger; The raw air pipeline passes through the second air pre-cooling heat exchanger and the second main heat exchanger; The nitrogen pipeline in the tower and the nitrogen branch pipeline both pass through the second main heat exchanger and are connected to the first pipeline; The first product pipeline in the air rectification tower passes through the second product heat exchanger and is connected to the first pipeline; The liquid nitrogen branch pipeline passes through the second product heat exchanger and the second main heat exchanger and is connected to the first pipeline; The third nitrogen circulation pipeline branch or the fourth nitrogen circulation pipeline branch passes through the hydrogen liquefaction pre-cooling cold box and is connected to the first pipeline.

4. The combined air separation and hydrogen liquefaction pre-cooling system based on nitrogen cycle refrigeration according to claim 2 is characterized in that: The hydrogen liquefaction precooling device further includes a circulating refrigerant precooling pipeline, and the circulating refrigerant precooling pipeline passes through the hydrogen liquefaction precooling cold box.

5. The combined air separation and hydrogen liquefaction pre-cooling system based on nitrogen cycle refrigeration according to claim 3 is characterized in that: When the fourth nitrogen circulation pipeline branch is connected to the hydrogen liquefaction pre-cooling cold box, the hydrogen liquefaction pre-cooling device also includes a pre-cooling refrigerant pipeline, which passes through the hydrogen liquefaction pre-cooling cold box and is connected to the LNG receiving station. The pre-cooling refrigerant pipeline is used to transport LNG to provide cooling capacity for the hydrogen liquefaction pre-cooling cold box.

6. The combined air separation and hydrogen liquefaction pre-cooling system based on nitrogen cycle refrigeration according to claim 2 is characterized in that: The first product pipeline and the second product pipeline in the air rectification tower both pass through the first product heat exchanger.

7. The combined air separation and hydrogen liquefaction pre-cooling system based on nitrogen cycle refrigeration according to claim 2 is characterized in that: The dirty nitrogen pipeline in the air rectification tower passes through the first product heat exchanger and the first main heat exchanger in sequence and is connected to the first pipeline.

8. The combined air separation and hydrogen liquefaction pre-cooling system based on nitrogen cycle refrigeration according to claim 1 is characterized in that: The second pipeline is connected with a throttle valve.

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