Liquid hydrogen production device and working method thereof

Abstract

The invention discloses a liquid hydrogen production device and a working method thereof.The liquid hydrogen production device comprises a first heat exchanger, a pipe mechanism, a conversion mechanism, a cooling mechanism and a valve bank, a second cooling medium inlet, a first inlet and a first outlet are formed in the first heat exchanger, and the pipe mechanism comprises a first cooling pipe; and the first cooling pipes are connected with the first heat exchanger. The valve set comprises a second throttling valve, the second throttling valve is installed on a first cooling pipe, the first cooling pipe is communicated with a first outlet and a second cooling medium inlet, and circulating hydrogen entering the first heat exchanger from the first inlet exchanges heat with circulating hydrogen cooled and depressurized through the cooling mechanism. And the first cooling medium flows into the first cooling pipe from the first outlet, is throttled by the second throttling valve and enters the first heat exchanger from the second cooling medium inlet. The raw material hydrogen is cooled through the mode that expansion continuous refrigeration of the cooling mechanism cooperates with high-pressure throttling refrigeration, energy is saved, and meanwhile the product hydrogen with the parahydrogen content reaching 97% is produced.

Description

Technical Field

[0001] This application relates to the field of liquid hydrogen production technology, and in particular to liquid hydrogen production equipment and its operating methods. Background Technology

[0002] Hydrogen energy is considered one of the clean energy sources due to its pollution-free characteristics; however, the utilization of hydrogen energy requires solving a series of problems such as production, storage, and transportation.

[0003] For example, the produced compressed feedstock hydrogen needs to undergo pretreatment, conversion of ortho and parahydrogen, and cooling to convert it into liquid hydrogen for storage and transportation. However, the hydrogen molecule contains two spin isomers, ortho and parahydrogen, with a ratio of approximately 3:1 at room temperature. As the hydrogen temperature decreases, the higher-energy orthohydrogen spontaneously converts to the lower-energy parahydrogen, releasing heat. During the storage and transportation of liquid hydrogen, unconverted orthohydrogen spontaneously converts to parahydrogen, releasing heat, while the liquid hydrogen is heated and converted into a gaseous phase, causing it to evaporate from storage tanks and transport vehicles, resulting in economic losses.

[0004] To minimize losses, existing liquid hydrogen production facilities sequentially pass hydrogen through multiple ortho- and para-hydrogen converters during production to produce hydrogen with a para-hydrogen content of up to 95%. To produce liquid hydrogen with an even higher para-hydrogen content, the raw hydrogen needs to be cooled to an even lower temperature. This necessitates lowering the temperature of the cooling medium exchanging heat with the raw hydrogen, significantly increasing the energy consumption of the entire production system and hindering the widespread adoption and use of hydrogen energy. Summary of the Invention

[0005] To address the aforementioned technical problems and achieve at least one advantage of this application, this application provides a liquid hydrogen production apparatus, the liquid hydrogen production apparatus comprising:

[0006] The first heat exchanger has a raw material inlet, a product hydrogen outlet, a first cooling medium inlet, a second cooling medium inlet, a first inlet, and a first outlet. High-pressure raw material hydrogen enters the first heat exchanger through the raw material inlet, and high-pressure circulating hydrogen enters the first heat exchanger from the first cooling medium inlet and the first inlet, respectively.

[0007] The pipe mechanism includes a first pipe group, a second pipe group, and a first cooling pipe, wherein the first pipe group, the second pipe group, and the first cooling pipe are all connected to the first heat exchanger;

[0008] The conversion mechanism includes a plurality of first intermediate hydrogen converters, which are installed on the first tube group. The raw material hydrogen undergoes intermediate hydrogen conversion in the first intermediate hydrogen converter to produce high-pressure product hydrogen. The high-pressure product hydrogen is discharged from the product hydrogen outlet.

[0009] The cooling mechanism includes multiple expanders, which are installed in the second tube group. The circulating hydrogen gas output from the second tube group flows through the multiple expanders in sequence and returns to the first heat exchanger.

[0010] The valve assembly includes a second throttle valve installed on the first cooling pipe. The first cooling pipe is connected to the first outlet and the second cooling medium inlet. Circulating hydrogen gas discharged from the first outlet flows back to the first heat exchanger through the second throttle valve from the second cooling medium inlet.

[0011] According to one embodiment of this application, the conversion mechanism includes four first secondary hydrogen converters, which are sequentially defined as a first converter, a second converter, a third converter, and a fourth converter. The first pipe group includes a first inlet pipe, a first outlet pipe, a second inlet pipe, a second outlet pipe, a third inlet pipe, a third outlet pipe, a fourth inlet pipe, and a fourth outlet pipe.

[0012] The first inlet pipe and the first outlet pipe are both connected to the first converter and the first heat exchanger. The raw material hydrogen enters the first heat exchanger from the raw material inlet and undergoes a first heat exchange with the cooling medium. Then, it flows to the first converter through the first outlet pipe. The raw material hydrogen undergoes a positive and negative hydrogen conversion in the first converter. After that, it enters the first heat exchanger through the first inlet pipe to undergo a second heat exchange with the cooling medium.

[0013] The second inlet pipe and the second outlet pipe are both connected to the second converter and the first heat exchanger. The raw material hydrogen gas, after undergoing a second heat exchange in the first heat exchanger, flows to the second converter through the second outlet pipe, and then enters the first heat exchanger through the second inlet pipe to undergo a third heat exchange with the cooling medium.

[0014] The third inlet pipe and the third outlet pipe are both connected to the third converter and the first heat exchanger. After the raw material hydrogen undergoes a third heat exchange in the first heat exchanger, it flows through the third outlet pipe to the third converter, and then enters the first heat exchanger through the third inlet pipe to undergo a fourth heat exchange with the cooling medium.

[0015] The fourth inlet pipe and the fourth outlet pipe are both connected to the fourth converter and the first heat exchanger. After the raw material hydrogen undergoes the fourth heat exchange in the first heat exchanger, it flows to the fourth converter through the fourth outlet pipe. After being converted into high-pressure product hydrogen, it enters the first heat exchanger through the fourth inlet pipe to undergo the fifth heat exchange with the cooling medium.

[0016] According to one embodiment of this application, the first heat exchanger forms a first cooling medium outlet, the cooling mechanism includes three expanders, which are sequentially defined as a first expander, a second expander, and a third expander, and the second tube group includes a first output tube, a first input tube, a second output tube, a second input tube, a third output tube, and a third input tube;

[0017] The first output pipe and the first input pipe are both connected to the first expander and the first heat exchanger. The circulating hydrogen entering the first heat exchanger from the first cooling medium inlet undergoes a first heat exchange with the raw material hydrogen and then flows into the first expander through the first output pipe. After that, it flows back to the first heat exchanger through the first input pipe to undergo a second heat exchange with the raw material hydrogen.

[0018] The second output pipe and the second input pipe are both connected to the second expander and the first heat exchanger. The circulating hydrogen gas, after undergoing the second heat exchange in the first heat exchanger, is introduced into the second expander through the second output pipe, and then flows back to the first heat exchanger through the second input pipe to undergo the third heat exchange with the raw material hydrogen gas.

[0019] The third output pipe and the third input pipe are both connected to the third expander and the first heat exchanger. The circulating hydrogen gas, after undergoing the third heat exchange in the first heat exchanger, is introduced into the third expander through the third output pipe, and then flows back to the first heat exchanger through the third input pipe to undergo the fourth heat exchange with the raw material hydrogen gas. After the fourth heat exchange, it is discharged from the first cooling medium outlet.

[0020] According to one embodiment of this application, the liquid hydrogen production equipment further includes a first liquefaction tank, the valve group includes a first throttle valve, and the pipe assembly includes a third pipe assembly, which includes a first exhaust pipe, a first liquid discharge pipe, and a second exhaust pipe. The first exhaust pipe is connected to the product hydrogen outlet and the first liquefaction tank. The first throttle valve is installed on the first exhaust pipe. High-pressure product hydrogen discharged from the product hydrogen outlet enters the first liquefaction tank after being throttled by the first throttle valve through the first exhaust pipe. Under the throttling action of the first throttle valve, the high-pressure product hydrogen is converted into medium-pressure liquid hydrogen and... Medium-pressure product hydrogen is discharged from the first liquefaction tank via the first drain pipe. The first heat exchanger also forms a first reflux port. The second exhaust pipe is connected to the first reflux port and the first liquefaction tank. The medium-pressure product hydrogen in the first liquefaction tank enters the first heat exchanger via the second exhaust pipe. The medium-pressure product hydrogen entering the first heat exchanger from the first reflux port serves as a cooling medium for heat exchange with the raw material hydrogen. The medium-pressure product hydrogen after heat exchange with the raw material hydrogen serves as a source of circulating hydrogen and is discharged from the first cooling medium outlet.

[0021] According to one embodiment of this application, the third pipe assembly further includes a second drain pipe, the valve assembly includes a third throttle valve, one end of the second drain pipe is connected to a pipe laid between the first outlet and the second throttle valve, and the other end is connected to the first liquefaction tank.

[0022] According to one embodiment of this application, the liquid hydrogen production equipment further includes a second intermediate hydrogen converter, which is installed on the pipeline flowing from the first outlet to the first liquefaction tank. The circulating hydrogen flowing into the first liquefaction tank through the second drain pipe undergoes intermediate hydrogen conversion in the second intermediate hydrogen converter.

[0023] According to one embodiment of this application, the liquid hydrogen production equipment further includes a subcooling mechanism, which includes a subcooler and a second liquefaction tank. The subcooler is installed inside the second liquefaction tank. A first drain pipe is connected to the subcooler and the first liquefaction tank. Medium-pressure liquid hydrogen flowing out of the first liquefaction tank flows into the subcooler through the first drain pipe. The pipe mechanism further includes a fourth pipe assembly, which includes a third drain pipe and a return pipe. The third drain pipe is connected to the subcooler and a storage tank for storing liquid hydrogen. Part of the liquid hydrogen discharged from the subcooler enters the storage tank through the third drain pipe. The return pipe is connected to the third drain pipe and the second liquefaction tank. The valve assembly further includes a fourth throttle valve, which is installed on the return pipe. Part of the liquid hydrogen discharged from the subcooler is input into the second liquefaction tank through the return pipe and the fourth throttle valve.

[0024] According to one embodiment of this application, the fourth pipe assembly further includes a third exhaust pipe. The first heat exchanger forms a second inlet and a second outlet. The third exhaust pipe is connected to the second liquefaction tank and the second inlet. The low-pressure product hydrogen gas vaporized from the liquid hydrogen in the second liquefaction tank flows out through the third exhaust pipe and enters the first heat exchanger through the second inlet, and then exits from the second outlet.

[0025] According to one embodiment of this application, the first heat exchanger includes a third inlet, the fourth tube group further includes a second cooling tube, the second cooling tube is connected to the third drain pipe and the third inlet, the valve group further includes a fifth throttle valve, the fifth throttle valve is installed on the second cooling tube, and a portion of the liquid hydrogen flowing out from the subcooler flows into the first heat exchanger from the second cooling tube through the fifth throttle valve, and then is discharged from the second outlet.

[0026] To address the aforementioned technical problems and achieve at least one advantage of this application, this application provides a method for operating a liquid hydrogen production apparatus according to any of the above embodiments, comprising:

[0027] The raw material hydrogen enters the first heat exchanger through the raw material inlet. A stream of circulating hydrogen entering the first heat exchanger exchanges heat with the raw material hydrogen entering the first heat exchanger and another stream of circulating hydrogen entering the first heat exchanger.

[0028] After heat exchange, the raw material hydrogen is discharged from the first heat exchanger and enters the first positive and negative hydrogen converter through a pipeline, and then flows back to the first heat exchanger through a pipeline. The raw material hydrogen undergoes positive and negative hydrogen conversion in the first positive and negative hydrogen converter to produce high-pressure product hydrogen. The high-pressure product hydrogen is discharged from the product hydrogen outlet.

[0029] The circulating hydrogen, heated by exchanging heat with the raw material hydrogen, flows into the cooling mechanism and, after its temperature is reduced, flows back to the first heat exchanger. The circulating hydrogen, after exchanging heat with the circulating hydrogen flowing through the cooling mechanism, flows out of the first heat exchanger and, after being throttled by the second throttle valve through the pipeline, returns to the first heat exchanger and exchanges heat with the raw material hydrogen.

[0030] The liquid hydrogen production apparatus and its operating method provided in this application have the following technical advantages compared with the prior art:

[0031] 1. This application sets up multiple expanders and throttling valves connected in series. The expanders continuously refrigerate in conjunction with high-pressure throttling refrigeration to cool the raw material hydrogen, thereby achieving energy saving while producing product hydrogen with a secondary hydrogen content of up to 97%.

[0032] 2. This application adopts a method of transporting medium-pressure product hydrogen after gas-liquid separation to the first heat exchange device through a pipeline, so that the cold energy of the unliquefied product hydrogen can be recovered and utilized, further reducing the energy consumption of the liquid hydrogen production system.

[0033] 3. This application adds unliquefied product hydrogen back into the production line as recycled hydrogen, and converts a portion of the recycled hydrogen into liquid hydrogen, thereby increasing the output of liquid hydrogen.

[0034] 4. This application also includes a subcooling mechanism to further cool the liquid hydrogen introduced into the storage tank, so that the temperature of the liquid hydrogen introduced into the storage tank is much lower than the temperature of the liquid hydrogen corresponding to the equilibrium of 97% secondary hydrogen content. This can reduce evaporation caused by slight temperature rise during storage and transportation, and improve efficiency.

[0035] 5. This application uses high-pressure throttling refrigeration to cool down part of the supercooled liquid hydrogen. After cooling down, the supercooled liquid hydrogen is used as a cooling medium to exchange heat with the raw material hydrogen. In this application, multiple cooling media with different temperature ranges are used to exchange heat with the raw material hydrogen. While meeting the heat exchange requirements of the raw material hydrogen, the raw material hydrogen can be reduced to a lower temperature and energy consumption can be saved. Attached Figure Description

[0036] Figure 1A schematic diagram of the liquid hydrogen production system described in this application is shown.

[0037] Figure 2 A schematic diagram of the liquid hydrogen production apparatus described in this application is shown.

[0038] Figure 3 It shows Figure 2 A schematic diagram of the structure of part A.

[0039] Figure Labels

[0040] 10. First heat exchanger; 1001. Raw material inlet; 1002. Product hydrogen outlet; 1003. First cooling medium inlet; 1004. First cooling medium outlet; 1005. First reflux port; 1006. Second cooling medium inlet; 1007. Second cooling medium outlet; 1008. First inlet; 1009. First outlet; 1011. Second inlet; 1012. Second outlet; 1013. Third inlet.

[0041] 20. Conversion mechanism; 21. First neutral hydrogen converter; 211. First converter; 212. Second converter; 213. Third converter; 214. Fourth converter.

[0042] 30. Cooling mechanism; 31. Expander; 311. First expander; 312. Second expander; 313. Third expander.

[0043] 40. Pipe assembly; 41. First pipe group; 411. First air inlet pipe; 412. First air outlet pipe; 413. Second air inlet pipe; 414. Second air outlet pipe; 415. Third air inlet pipe; 416. Third air outlet pipe; 417. Fourth air inlet pipe; 418. Fourth air outlet pipe; 42. Second pipe group; 421. First output pipe; 422. First input pipe; 423. Second output pipe; 424. Second input pipe; 425. Third output pipe; 426. Third input pipe; 43. Third pipe group; 431. First exhaust pipe; 432. First drain pipe; 433. Second exhaust pipe; 434. Second drain pipe; 44. First cooling pipe; 45. Fourth pipe group; 451. Third drain pipe; 452. Return pipe; 453. Third exhaust pipe; 454. Second cooling pipe.

[0044] 50. First liquefaction tank.

[0045] 60. Valve assembly; 61. First throttle valve; 63. Third throttle valve; 64. Fourth throttle valve; 65. Fifth throttle valve.

[0046] 70. Second neutral hydrogen converter.

[0047] 80. Subcooling mechanism; 81. Subcooler; 82. Second liquefaction tank.

[0048] 90. Hydrogen precooling equipment; 91. Second heat exchanger; 9101. First inlet; 9102. First outlet; 9103. Second inlet; 9104. Second outlet; 9105. Third inlet; 9106. Third outlet; 92. Pressurization mechanism; 93. Nitrogen cooling mechanism. Detailed Implementation

[0049] The following description is intended to disclose this application and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of this application defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of this application.

[0050] Those skilled in the art should understand that, in the disclosure of this application, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limitations on this application.

[0051] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0052] refer to Figures 1 to 3 A preferred embodiment of the liquid hydrogen production system according to this application will be described in detail below. The liquid hydrogen production system includes a liquid hydrogen production apparatus, which includes a first heat exchanger 10, a conversion mechanism 20, a cooling mechanism 30, and a pipe mechanism 40.

[0053] The first heat exchanger 10 has a raw material inlet 1001, a product hydrogen outlet 1002, a first cooling medium inlet 1003, and a first cooling medium outlet 1004. High-pressure raw material hydrogen enters the first heat exchanger 10 through the raw material inlet 1001, and high-pressure circulating hydrogen, as a cooling medium, enters the first heat exchanger 10 through the first cooling medium inlet 1003. The raw material hydrogen and the cooling medium exchange heat within the first heat exchanger 10. After heat exchange, the temperature of the raw material hydrogen decreases while the temperature of the cooling medium increases.

[0054] The pipe assembly 40 includes a first pipe group 41 and a second pipe group 42, both of which are connected to the first heat exchanger 10. The conversion mechanism 20 is installed in the first pipe group 41, and the cooling mechanism 30 is installed in the second pipe group 42. Raw material hydrogen discharged from the first heat exchanger 10 enters the conversion mechanism 20 through the first pipe group 41, where it undergoes a conversion from positive hydrogen to secondary hydrogen after being cooled by heat exchange with the cooling medium. This reduces the positive hydrogen content in the raw material hydrogen and produces high-pressure product hydrogen. Notably, the secondary hydrogen content in the product hydrogen is not less than 97%. The high-pressure product hydrogen produced by the conversion mechanism 20 flows back to the first heat exchanger 10 through the first pipe group 41 and is then discharged from the product hydrogen outlet 1002. The circulating hydrogen gas discharged from the first heat exchanger 10 enters the cooling mechanism 30 through the second tube group 42. The high-pressure circulating hydrogen gas expands and does work in the cooling mechanism 30 to reduce its own temperature and pressure. The medium-pressure low-temperature circulating hydrogen gas produced from the cooling mechanism 30 flows back to the first heat exchanger 10 through the second tube group 42 and is then discharged from the first cooling medium outlet 1004.

[0055] Understandably, after the circulating hydrogen exchanges heat with the raw material hydrogen in the first heat exchanger 10, its temperature rises. The heat exchange efficiency between the heated circulating hydrogen and the raw material hydrogen decreases, causing the conversion of the positive hydrogen to the secondary hydrogen in the raw material hydrogen to stagnate. Therefore, the circulating hydrogen, which has been heated by exchanging heat with the raw material hydrogen, flows from the first heat exchanger 10 to the cooling mechanism 30 and then flows back to the first heat exchanger 10 after cooling, so as to continue exchanging heat with the raw material hydrogen. This provides sufficient cooling capacity for the raw material hydrogen, ensuring that its temperature can continue to drop, allowing the positive hydrogen in the raw material hydrogen to continue to convert to the secondary hydrogen, thereby increasing the secondary hydrogen content in the high-pressure product hydrogen discharged from the product hydrogen outlet 1002.

[0056] Preferably, the conversion mechanism 20 includes a plurality of first positive and negative hydrogen converters 21, which are installed on the first tube group 41 and connected to the first heat exchanger 10 through the first tube group 41. The raw material hydrogen flows from the first heat exchanger 10 to any of the first positive and negative hydrogen converters 21 and then flows back to the first heat exchanger 10, so that the raw material hydrogen output from the first tube group 41 flows sequentially through the plurality of first positive and negative hydrogen converters 21. In this way, the raw material hydrogen undergoes positive hydrogen to negative hydrogen conversion successively in each of the first positive and negative hydrogen converters 21, gradually increasing the negative hydrogen content in the raw material hydrogen to produce high-pressure product hydrogen with a negative hydrogen content of not less than 97%. This ensures that the negative hydrogen content in the liquid hydrogen liquefied from the product hydrogen is also not less than 97%, thereby reducing losses during storage and transportation of liquid hydrogen and improving economic efficiency.

[0057] In one specific embodiment, the conversion mechanism 20 includes four first neutral hydrogen converters 21, which are sequentially defined as first converter 211, second converter 212, third converter 213, and fourth converter 214. The first pipe assembly 41 includes a first inlet pipe 411, a first outlet pipe 412, a second inlet pipe 413, a second outlet pipe 414, a third inlet pipe 415, a third outlet pipe 416, a fourth inlet pipe 417, and a fourth outlet pipe 418.

[0058] The first inlet pipe 411 and the first outlet pipe 412 are both connected to the first converter 211 and the first heat exchanger 10. The raw material hydrogen entering the first heat exchanger 10 from the raw material inlet 1001 undergoes a first heat exchange with the cooling medium and then flows through the first outlet pipe 412 to the first converter 211. The raw material hydrogen undergoes a positive and negative hydrogen conversion in the first converter 211, and then enters the first heat exchanger 10 through the first inlet pipe 411. This allows the raw material hydrogen to return to the first heat exchanger 10 after the first positive and negative hydrogen conversion in the first converter 211 for a second heat exchange with the cooling medium and further cooling, so that the positive hydrogen in the raw material hydrogen can continue to convert to negative hydrogen. The temperature of the raw material hydrogen flowing through the first outlet pipe 412 is -212±2℃.

[0059] The second inlet pipe 413 and the second outlet pipe 414 are both connected to the second converter 212 and the first heat exchanger 10. After undergoing a second heat exchange in the first heat exchanger 10, the raw material hydrogen flows through the second outlet pipe 414 to the second converter 212. The raw material hydrogen continues to undergo ortho- and para-hydrogen conversion in the second converter 212, and then enters the first heat exchanger 10 through the second inlet pipe 413. This allows the raw material hydrogen to return to the first heat exchanger 10 after undergoing a second ortho- and para-hydrogen conversion in the second converter 212 for a third heat exchange with the cooling medium and further cooling, so that the ortho-hydrogen in the raw material hydrogen can continue to convert to para-hydrogen. The temperature of the raw material hydrogen flowing through the second outlet pipe 414 is -229℃±2℃.

[0060] The third inlet pipe 415 and the third outlet pipe 416 are both connected to the third converter 213 and the first heat exchanger 10. After undergoing a third heat exchange in the first heat exchanger 10, the raw material hydrogen flows through the third outlet pipe 416 to the third converter 213. The raw material hydrogen continues to undergo ortho- and para-hydrogen conversion in the third converter 213, and then enters the first heat exchanger 10 through the third inlet pipe 415. This allows the raw material hydrogen to return to the first heat exchanger 10 after the third ortho- and para-hydrogen conversion in the third converter 213 for a fourth heat exchange with the cooling medium and further cooling, so that the ortho-hydrogen in the raw material hydrogen can continue to convert to para-hydrogen. The temperature of the raw material hydrogen flowing through the third outlet pipe 416 is -235℃±2℃.

[0061] The fourth inlet pipe 417 and the fourth outlet pipe 418 are both connected to the fourth converter 214 and the first heat exchanger 10. The raw material hydrogen, after undergoing its fourth heat exchange in the first heat exchanger 10, flows through the fourth outlet pipe 418 to the fourth converter 214. In the fourth converter 214, the raw material hydrogen continues to undergo ortho- and para-hydrogen conversion. The high-pressure raw material hydrogen undergoes four ortho- and para-hydrogen conversions to become high-pressure product hydrogen. This high-pressure product hydrogen then enters the first heat exchanger 10 through the fourth inlet pipe 417, allowing the raw material hydrogen to return to the first heat exchanger 10 after its fourth ortho- and para-hydrogen conversion in the fourth converter 214 for a fifth heat exchange with the cooling medium. The heat-exchanged product hydrogen is then discharged from the product hydrogen outlet 1002. The temperature of the product hydrogen discharged from the product hydrogen outlet 1002 is maintained at -244℃ ± 2℃, and the temperature of the raw material hydrogen flowing through the fourth outlet pipe 418 is also -244℃ ± 2℃. Understandably, the product hydrogen produced from the fourth converter 214 is input into the first heat exchanger 10 through the fourth inlet pipe 417 to exchange heat with the cooling medium to maintain its own temperature, so as to facilitate subsequent liquefaction.

[0062] In the above embodiment, the raw material hydrogen undergoes multiple cooling processes, resulting in its temperature being reduced to four different temperature ranges. After each temperature range is reached within the first heat exchanger 10, the raw material hydrogen is output from the first heat exchanger 10 and input into the corresponding first neutral hydrogen converter 21. Within the corresponding first neutral hydrogen converter 21, the raw material hydrogen breaks through the neutral hydrogen content equilibrium reached in the previous converter, causing some of the neutral hydrogen in the raw material hydrogen to convert to neutral hydrogen, thereby producing product hydrogen.

[0063] Preferably, the cooling mechanism 30 includes a plurality of expanders 31, which are installed in the second tube group 42 and are all connected to the first heat exchanger 10. Circulating hydrogen flows from the first heat exchanger 10 to any of the first positive and negative hydrogen converters 21 and then back to the first heat exchanger 10, so that the circulating hydrogen output from the second tube group 42 flows sequentially through the plurality of expanders 31 and expands within each expander 31 to do work, thereby reducing its own temperature and pressure. This allows the circulating hydrogen flowing out of the expanders 31 and into the first heat exchanger 10 to continue providing cooling for the raw material hydrogen, thus allowing the temperature of the raw material hydrogen to continue to decrease.

[0064] In one embodiment, the cooling mechanism 30 includes three expanders 31, which are sequentially defined as a first expander 311, a second expander 312, and a third expander 313. The second tube group 42 includes a first output tube 421, a first input tube 422, a second output tube 423, a second input tube 424, a third output tube 425, and a third input tube 426.

[0065] Both the first output pipe 421 and the first input pipe 422 are connected to the first expander 311 and the first heat exchanger 10. Circulating hydrogen entering the first heat exchanger 10 from the first cooling medium inlet 1003 undergoes a first heat exchange with the raw material hydrogen and then flows into the first expander 311 through the first output pipe 421. The circulating hydrogen expands and performs work within the first expander 311, thereby reducing its pressure and temperature. It then flows back to the first heat exchanger 10 through the first input pipe 422, allowing the circulating hydrogen to undergo a second heat exchange with the raw material hydrogen.

[0066] The second output pipe 423 and the second input pipe 424 are both connected to the second expander 312 and the first heat exchanger 10. After the second heat exchange in the first heat exchanger 10, the circulating hydrogen gas is introduced into the second expander 312 through the second output pipe 423. The circulating hydrogen gas expands and does work in the second expander 312, thereby reducing its pressure and temperature. Then, it flows back to the first heat exchanger 10 through the second input pipe 424 to undergo a third heat exchange with the raw material hydrogen gas.

[0067] The third output pipe 425 and the third input pipe 426 are both connected to the third expander 313 and the first heat exchanger 10. The circulating hydrogen, after undergoing a third heat exchange in the first heat exchanger 10, is introduced into the third expander 313 through the third output pipe 425. The circulating hydrogen expands and performs work within the third expander 313, thereby reducing its pressure and temperature. Because the circulating hydrogen undergoes three expansions, the high-pressure circulating hydrogen is converted into medium-pressure circulating hydrogen. The medium-pressure circulating hydrogen flows back to the first heat exchanger 10 through the third input pipe 426 and undergoes a fourth heat exchange with the raw material hydrogen. After the fourth heat exchange, the medium-pressure circulating hydrogen is discharged from the first cooling medium outlet 1004. The temperature of the circulating hydrogen flowing through the first cooling medium inlet 1003 is -156℃±4℃; the temperature of the circulating hydrogen flowing through the third input pipe 426 is -245℃±2℃.

[0068] refer to Figure 1 It is worth mentioning that the first cooling medium outlet 1004 is connected to the hydrogen precooling device 90 of the liquid hydrogen production system via a pipeline. Specifically, the hydrogen precooling device 90 includes a second heat exchanger 91, a pressurizing mechanism 92, and a nitrogen cooling mechanism 93. The second heat exchanger 91 forms a first inlet 9101, a first outlet 9102, a second inlet 9103, and a second outlet 9104. The first cooling medium outlet 1004 is connected to the first inlet 9101 via a pipeline, and the second outlet 9104 is connected to the first cooling medium inlet 1003 via a pipeline. The first outlet 9102 is connected to the second inlet 9103 via a pipeline, and the pressurizing mechanism 92 is installed on the pipeline connecting the first outlet 9102 and the second inlet 9103. The nitrogen cooling mechanism 93 is connected to the second heat exchanger 91 via a pipeline. The circulating hydrogen gas discharged from the first cooling medium outlet 1004 passes through the second heat exchanger 91 and enters the pressurization mechanism 92 through the first outlet 9102. The pressurization mechanism 92 is used to increase the gas pressure. The high-pressure circulating hydrogen gas discharged from the pressurization mechanism 92 enters the second heat exchanger 91 through the second inlet 9103 and exchanges heat with the subcooled nitrogen gas flowing into the second heat exchanger 91 from the nitrogen cooling mechanism 93 to cool down. The cooled high-pressure circulating hydrogen gas is then output through the second outlet 9104 to the first cooling medium inlet 1003 for recycling, avoiding waste of hydrogen resources.

[0069] As an example, the pressurization mechanism 92 is implemented as a compressor, and the nitrogen cooling mechanism 93 is implemented including a compressor and an expansion device connected in series with the compressor.

[0070] Furthermore, the liquid hydrogen production equipment also includes a first liquefaction tank 50 and a valve group 60.

[0071] The valve assembly 60 includes a first throttle valve 61. The pipe assembly 40 includes a third pipe assembly 43, which includes a first exhaust pipe 431, a first drain pipe 432, and a second exhaust pipe 433. The first exhaust pipe 431 is connected to the product hydrogen outlet 1002 and the first liquefaction tank 50, and the first throttle valve 61 is installed on the first exhaust pipe 431. High-pressure product hydrogen discharged from the product hydrogen outlet 1002 enters the first liquefaction tank 50 after being throttled by the first throttle valve 61 through the first exhaust pipe 431. The high-pressure product hydrogen is depressurized and cooled by the throttling effect of the first throttle valve 61, causing the high-pressure product hydrogen to be converted into medium-pressure liquid hydrogen and medium-pressure product hydrogen. The first drain pipe 432 is connected to the first liquefaction tank 50, and the medium-pressure liquid hydrogen is discharged from the first liquefaction tank 50 through the first drain pipe 432. The first heat exchanger 10 also forms a first reflux port 1005. The second exhaust pipe 433 is connected to the first reflux port 1005 and the first liquefaction tank 50. The medium-pressure product hydrogen in the first liquefaction tank 50 enters the first heat exchanger 10 through the second exhaust pipe 433. The medium-pressure product hydrogen entering the first heat exchanger 10 from the first reflux port 1005 serves as a cooling medium to exchange heat with the raw material hydrogen, thereby recovering the cooling capacity of the medium-pressure product hydrogen and reducing the energy consumption of the hydrogen pre-cooling device 90. The medium-pressure product hydrogen after heat exchange with the raw material hydrogen serves as the gas source for circulating hydrogen and is discharged from the first cooling medium outlet 1004. After being pressurized and cooled, it enters the liquid hydrogen production equipment for internal circulation from the first cooling medium inlet 1003, avoiding the waste of hydrogen energy. The temperature of the medium-pressure liquid hydrogen flowing through the first drain pipe 432 is -246℃±2℃.

[0072] Preferably, the first heat exchanger 10 forms a second cooling medium inlet 1006, a second cooling medium outlet 1007, a first inlet 1008, and a first outlet 1009. The pipe structure 40 further includes a first cooling pipe 44, and the valve group 60 includes a second throttle valve 62, which is installed on the first cooling pipe 44. The first cooling pipe 44 is connected to the first outlet 1009 and the second cooling medium inlet 1006. High-pressure circulating hydrogen is divided into two streams: one enters the first heat exchanger 10 from the first cooling medium inlet 1003, and the other enters the first heat exchanger 10 from the first inlet 1008. The circulating hydrogen entering the first heat exchanger 10 from the first inlet 1008 exchanges heat with the circulating hydrogen that has been cooled and depressurized by the expander 31 to cool down, and then flows from the first outlet 1009 into the first cooling pipe 44, where it is throttled by the second throttle valve 62 and enters the first heat exchanger 10 from the second cooling medium inlet 1006. After cooling, the high-pressure circulating hydrogen is reduced to medium pressure by the throttling effect of the second throttle valve 62 and continues to cool. It then enters the first heat exchanger 10 from the second cooling medium inlet 1006, making the circulating hydrogen entering the first heat exchanger 10 from the second cooling medium inlet 1006 a cooler medium. After exchanging heat with the raw material hydrogen, it is discharged from the second cooling medium outlet 1007. The second cooling medium outlet 1007 is connected via a pipe to the pipe connecting the first cooling medium outlet 1004 and the outlet of the third expander 313. The medium-pressure circulating hydrogen discharged from the second cooling medium outlet 1007 and the medium-pressure circulating hydrogen discharged from the third expander 313 converge and exchange heat with the raw material hydrogen within the first heat exchanger 10.

[0073] Preferably, the second cooling medium outlet 1007 is connected to the third input pipe 426 via a pipe, so that the circulating hydrogen discharged from the second cooling medium outlet 1007 enters from the upstream of the flow path formed between the outlet of the third expander 313 and the first cooling medium outlet 1004, thereby extending the flow path of the circulating hydrogen discharged from the second cooling medium outlet 1007 and entering the first heat exchanger 10, ensuring that the circulating hydrogen undergoes sufficient heat exchange, and thus reducing the energy consumption of the hydrogen precooling device 90.

[0074] The temperature of the circulating hydrogen flowing through the first outlet 1009 is -244℃±2℃; the temperature of the circulating hydrogen flowing through the second cooling medium inlet 1006 is -246℃±2℃. It can be understood that the circulating hydrogen entering the first heat exchanger 10 from the second cooling medium inlet 1006 can achieve a lower temperature than the circulating hydrogen entering the first heat exchanger 10 from the third input pipe 426 simply due to the throttling effect of the second throttling valve 62. Compared to lowering the temperature of the circulating hydrogen discharged from the second outlet 9104, the solution adopted in this application can reduce the load on the nitrogen cooling mechanism 93, and the hydrogen returning to the hydrogen pre-cooling device 90 from the first cooling medium outlet 1004 is at medium pressure. This reduces the load on the pressurization mechanism 92, thereby achieving energy savings.

[0075] As an example, the temperature of the circulating hydrogen flowing through the second cooling medium inlet 1006 is -156℃±4℃; the temperature of the product hydrogen flowing through the second cooling medium outlet 1007 is -245℃±2℃.

[0076] Preferably, the third pipe assembly 43 further includes a second drain pipe 434, and the valve assembly 60 includes a third throttle valve 63. One end of the second drain pipe 434 is connected to a pipe laid between the first outlet 1009 and the second throttle valve 62, and the other end is connected to the first liquefaction tank 50. That is, the high-pressure circulating hydrogen discharged from the first outlet 1009 is divided into two streams: one stream flows to the first heat exchanger 10 through the second throttle valve 62, and the other stream enters the first liquefaction tank 50 from the second drain pipe 434 through the third throttle valve 63. The high-pressure circulating hydrogen is depressurized and cooled by the throttling effect of the third throttle valve 63, causing the high-pressure circulating hydrogen to be converted into medium-pressure liquid hydrogen and medium-pressure circulating hydrogen. The medium-pressure circulating hydrogen is discharged from the second exhaust pipe 433, and the medium-pressure liquid hydrogen is discharged from the first drain pipe 432. Since the circulating hydrogen originates from the product hydrogen, and part of the circulating hydrogen is liquefied into liquid hydrogen in this process, the production of liquid hydrogen is increased. In addition, the product hydrogen as circulating hydrogen has been converted by the conversion mechanism 20 beforehand. Therefore, the secondary hydrogen content in the circulating hydrogen entering the first liquefaction tank 50 from the second drain pipe 434 is not less than 97%. Therefore, the circulating hydrogen flowing to the second drain pipe 434 does not need to be pre-treated by the conversion mechanism 20. Thus, the processing capacity of the conversion mechanism 20 for raw material hydrogen can be increased, thereby increasing the liquid hydrogen output of the liquid hydrogen production equipment.

[0077] Preferably, the liquid hydrogen production equipment further includes a second neutral hydrogen converter 70, which is installed on the pipeline flowing from the first outlet 1009 to the first liquefaction tank 50 to ensure that the neutral hydrogen content in the circulating hydrogen flowing into the first liquefaction tank 50 through the second drain pipe 434 is not less than 97%.

[0078] refer to Figure 2 and Figure 3 Furthermore, the liquid hydrogen production equipment also includes a subcooling mechanism 80, which includes a subcooler 81 and a second liquefaction tank 82, with the subcooler 81 installed inside the second liquefaction tank 82. A first drain pipe 432 connects the subcooler 81 and the first liquefaction tank 80, allowing medium-pressure liquid hydrogen flowing from the first liquefaction tank 50 to flow into the subcooler 81 via the first drain pipe 432. The pipe mechanism 40 also includes a fourth pipe assembly 45, which includes a third drain pipe 451 and a return pipe 452. The third drain pipe 451 connects the subcooler 81 and a storage tank for storing liquid hydrogen. A portion of the liquid hydrogen discharged from the subcooler 81 enters the storage tank via the third drain pipe 451 for storage. The return pipe 452 is connected to the third drain pipe 451 and the second liquefaction tank 82. The valve group 60 also includes a fourth throttle valve 64, which is installed on the return pipe 452. A portion of the liquid hydrogen discharged from the subcooler 81 enters the second liquefaction tank 82 through the return pipe 452 and the fourth throttle valve 64. The portion of liquid hydrogen discharged from the subcooler 81 is throttled by the fourth throttle valve 64 before entering the second liquefaction tank 82, causing the medium-pressure liquid hydrogen to drop to a low pressure and cool down, serving as a cooling medium to exchange heat with the medium-pressure liquid hydrogen entering the subcooler 81, further reducing the temperature of the medium-pressure liquid hydrogen. For example, the temperature of the low-pressure liquid hydrogen entering the second liquefaction tank 82 is -251℃ ± 2℃. It is understandable that the temperature of the medium-pressure liquid hydrogen discharged from the supercooler 81 is much lower than the temperature of the medium-pressure liquid hydrogen corresponding to the equilibrium of 97% secondary hydrogen content. In this way, the losses caused by the slight temperature rise during storage and transportation can be reduced.

[0079] The liquid hydrogen entering the second liquefaction tank 82 is cooled and depressurized through the fourth throttle valve 64, eliminating the need for external cold supply and further reducing the energy consumption of the entire liquid hydrogen production system.

[0080] Preferably, the fourth pipe assembly 45 further includes a third exhaust pipe 453, which is connected to the second liquefaction tank 82, and the low-pressure product hydrogen gas generated by the vaporization of low-pressure liquid hydrogen in the second liquefaction tank 82 flows out through the third exhaust pipe 453.

[0081] Preferably, the first heat exchanger 10 has a second inlet 1011 and a second outlet 1012. The third exhaust pipe 453 is connected to the second inlet 1011. Low-pressure product hydrogen flowing out from the third exhaust pipe 453 enters the first heat exchanger 10 through the second inlet 1011 and then exits from the second outlet 1012. The low-pressure product hydrogen entering the first heat exchanger 10 exchanges heat with the raw material hydrogen, thereby recovering the cooling capacity of the low-pressure product hydrogen and further reducing the energy consumption of the nitrogen cooling mechanism 93.

[0082] The second heat exchanger 91 also forms a third inlet 9105 and a third outlet 9106. The second outlet 1012 is connected to the third inlet 9105 through a pipe so that the low-pressure product hydrogen discharged from the second outlet 1012 enters the second heat exchanger 91 as a cooling medium. The third outlet 9106 is connected to the pressurization mechanism 92 through a pipe. After heat exchange, the low-pressure product hydrogen is increased to high pressure by the pressurization mechanism 92 and then enters the second heat exchanger 91 from the second inlet 9103, and is added to the liquid hydrogen production device as circulating hydrogen.

[0083] The first heat exchanger 10 includes a third inlet 1013, and the fourth tube group 45 further includes a second cooling tube 454, which is connected to the third drain pipe 451 and the third inlet 1013. The valve group 60 further includes a fifth throttle valve 65, which is installed on the second cooling tube 454. Part of the liquid hydrogen flowing out from the subcooler 81 flows into the first heat exchanger 10 from the second cooling tube 454 through the fifth throttle valve 65. The medium-pressure liquid hydrogen is reduced to low pressure and cooled by the throttling effect of the fifth throttle valve 65, so that the low-pressure liquid hydrogen enters the first heat exchanger 10 as a cooling medium. The low-pressure liquid hydrogen entering the first heat exchanger 10 exchanges heat with the raw material hydrogen, so that the minimum temperature of the raw material hydrogen can reach -244℃±2℃. After exchanging heat with the raw material hydrogen, it is discharged from the second outlet 1012. As an example, the temperature of the low-pressure liquid hydrogen entering the first heat exchanger 10 is 252.3±2℃.

[0084] The cooling medium entering the first heat exchanger 10 from the third inlet 1013 and the cooling medium entering the first heat exchanger 10 from the second cooling medium inlet 1006 have different temperature ranges to meet the different cooling requirements of the raw hydrogen during the cooling process. Furthermore, the cooling capacity provided by the cooling medium entering the first heat exchanger 10 from the third inlet 1013 and the cooling capacity provided by the cooling medium entering the first heat exchanger 10 from the second cooling medium inlet 1006 can meet the fourth and fifth cooling requirements of the raw hydrogen, thus allowing the conversion of the raw hydrogen to ortho- and para-hydrogen to continue. By recovering cold energy and throttling and depressurizing to reduce the load on the nitrogen cooling mechanism 93, the energy consumption of the entire liquid hydrogen production system is reduced.

[0085] This application also provides a method for operating the liquid hydrogen production apparatus, including the following steps:

[0086] The raw material hydrogen enters the first heat exchanger 10, and a stream of circulating hydrogen entering the first heat exchanger 10 exchanges heat with the raw material hydrogen entering the first heat exchanger 10 and another stream of circulating hydrogen entering the first heat exchanger 10.

[0087] After heat exchange, the raw material hydrogen is discharged from the first heat exchanger 10 and enters the first intermediate hydrogen converter 21 through a pipeline, and then flows back to the first heat exchanger 10 through a pipeline to continue heat exchange, repeating the cycle multiple times. The raw material hydrogen undergoes intermediate hydrogen conversion in the first intermediate hydrogen converter 21 to produce high-pressure product hydrogen, which is discharged from the product hydrogen outlet 1002.

[0088] The circulating hydrogen, which is heated by exchanging heat with the raw material hydrogen, flows into the cooling mechanism 30 and flows back to the first heat exchanger 10 after the temperature is reduced, so as to continue heat exchange.

[0089] The circulating hydrogen, after exchanging heat with the circulating hydrogen flowing through the cooling mechanism 30, flows out of the first heat exchanger 10 and returns to the first heat exchanger 10 after being throttled by the second throttle valve 62, so as to serve as a cooling medium for heat exchange with the raw material hydrogen.

[0090] Preferably, the product hydrogen discharged from the product hydrogen outlet 1002 is throttled through the pipeline by the first throttle valve 61 to obtain medium-pressure liquid hydrogen and medium-pressure product hydrogen, and flows into the first liquefaction tank 50. The medium-pressure product hydrogen entering the first heat exchanger 10 from the first return port 1005 serves as a cooling medium to exchange heat with the raw material hydrogen. The medium-pressure product hydrogen after heat exchange with the raw material hydrogen serves as a gas source for circulating hydrogen and is discharged from the first cooling medium outlet 1004 to recover part of the cold energy.

[0091] Preferably, a portion of the circulating hydrogen, after exchanging heat with the circulating hydrogen flowing through the cooling mechanism 30, flows from the pipeline through the third throttle valve 63 into the first liquefaction tank 50, so that a portion of the circulating hydrogen is liquefied under the throttling effect of the third throttle valve 63, thereby increasing the output of liquid hydrogen.

[0092] In one embodiment, a portion of the circulating hydrogen, after exchanging heat with the circulating hydrogen flowing through the cooling mechanism 30, flows from the pipeline through the second ortho-parahydrogen converter 70 and then through the third throttle valve 63 into the first liquefaction tank 50, to ensure the parahydrogen content entering the first liquefaction tank 50.

[0093] Furthermore, the hydrogen discharged from the first liquefaction tank 50 flows through a pipeline to the first heat exchanger 10 to recover the cooling capacity.

[0094] Preferably, the liquid hydrogen discharged from the first liquefaction tank 50 enters the subcooler 81, and a portion of the liquid hydrogen discharged from the subcooler 81 is depressurized and cooled down and then used as a cooling medium to cool the liquid hydrogen entering the subcooler 81, so that the liquid hydrogen is cooled down to a lower temperature to prevent the secondary hydrogen content from decreasing due to temperature fluctuations.

[0095] Furthermore, a portion of the liquid hydrogen discharged from the subcooler 81 is depressurized and cooled before being input into the first heat exchanger 10 as a cooling medium to meet the heat exchange requirements of the raw material hydrogen.

[0096] Those skilled in the art should understand that the embodiments of this application described above and shown in the accompanying drawings are merely examples and do not limit the scope of this application. The advantages of this application have been fully and effectively implemented. The functional and structural principles of this application have been demonstrated and explained in the embodiments, and any variations or modifications can be made to the implementation of this application without departing from the stated principles.

Claims

1. A liquid hydrogen production apparatus, characterized in that, The liquid hydrogen production unit includes: The first heat exchanger has a raw material inlet, a product hydrogen outlet, a first cooling medium inlet, a second cooling medium inlet, a first inlet, and a first outlet. High-pressure raw material hydrogen enters the first heat exchanger through the raw material inlet, and high-pressure circulating hydrogen enters the first heat exchanger from the first cooling medium inlet and the first inlet, respectively. The pipe mechanism includes a first pipe group, a second pipe group, and a first cooling pipe, wherein the first pipe group, the second pipe group, and the first cooling pipe are all connected to the first heat exchanger; The conversion mechanism includes a plurality of first intermediate hydrogen converters, which are installed on the first tube group. The raw material hydrogen undergoes intermediate hydrogen conversion in the first intermediate hydrogen converter to produce high-pressure product hydrogen. The high-pressure product hydrogen is discharged from the product hydrogen outlet. The cooling mechanism includes multiple expanders, which are installed in the second tube group. The circulating hydrogen gas output from the second tube group flows through the multiple expanders in sequence and returns to the first heat exchanger. The valve assembly includes a second throttle valve installed on the first cooling pipe. The first cooling pipe is connected to the first outlet and the second cooling medium inlet. Circulating hydrogen gas discharged from the first outlet flows back to the first heat exchanger through the second throttle valve from the second cooling medium inlet.

2. The liquid hydrogen production apparatus according to claim 1, characterized in that, The conversion mechanism includes four first secondary hydrogen converters, which are sequentially defined as first converter, second converter, third converter and fourth converter. The first pipe group includes a first inlet pipe, a first outlet pipe, a second inlet pipe, a second outlet pipe, a third inlet pipe, a third outlet pipe, a fourth inlet pipe and a fourth outlet pipe. The first inlet pipe and the first outlet pipe are both connected to the first converter and the first heat exchanger. The raw material hydrogen enters the first heat exchanger from the raw material inlet and undergoes a first heat exchange with the cooling medium. Then, it flows to the first converter through the first outlet pipe. The raw material hydrogen undergoes a positive and negative hydrogen conversion in the first converter. After that, it enters the first heat exchanger through the first inlet pipe to undergo a second heat exchange with the cooling medium. The second inlet pipe and the second outlet pipe are both connected to the second converter and the first heat exchanger. The raw material hydrogen gas, after undergoing a second heat exchange in the first heat exchanger, flows to the second converter through the second outlet pipe, and then enters the first heat exchanger through the second inlet pipe to undergo a third heat exchange with the cooling medium. The third inlet pipe and the third outlet pipe are both connected to the third converter and the first heat exchanger. After the raw material hydrogen undergoes a third heat exchange in the first heat exchanger, it flows through the third outlet pipe to the third converter, and then enters the first heat exchanger through the third inlet pipe to undergo a fourth heat exchange with the cooling medium. The fourth inlet pipe and the fourth outlet pipe are both connected to the fourth converter and the first heat exchanger. After the raw material hydrogen undergoes the fourth heat exchange in the first heat exchanger, it flows to the fourth converter through the fourth outlet pipe. After being converted into high-pressure product hydrogen, it enters the first heat exchanger through the fourth inlet pipe to undergo the fifth heat exchange with the cooling medium.

3. The liquid hydrogen production apparatus according to claim 2, characterized in that, The first heat exchanger forms a first cooling medium outlet, the cooling mechanism includes three expanders, which are sequentially defined as a first expander, a second expander, and a third expander, and the second tube group includes a first output tube, a first input tube, a second output tube, a second input tube, a third output tube, and a third input tube; The first output pipe and the first input pipe are both connected to the first expander and the first heat exchanger. The circulating hydrogen entering the first heat exchanger from the first cooling medium inlet undergoes a first heat exchange with the raw material hydrogen and then flows into the first expander through the first output pipe. After that, it flows back to the first heat exchanger through the first input pipe to undergo a second heat exchange with the raw material hydrogen. The second output pipe and the second input pipe are both connected to the second expander and the first heat exchanger. The circulating hydrogen gas, after undergoing the second heat exchange in the first heat exchanger, is introduced into the second expander through the second output pipe, and then flows back to the first heat exchanger through the second input pipe to undergo the third heat exchange with the raw material hydrogen gas. The third output pipe and the third input pipe are both connected to the third expander and the first heat exchanger. The circulating hydrogen gas, after undergoing the third heat exchange in the first heat exchanger, is introduced into the third expander through the third output pipe, and then flows back to the first heat exchanger through the third input pipe to undergo the fourth heat exchange with the raw material hydrogen gas. After the fourth heat exchange, it is discharged from the first cooling medium outlet.

4. The liquid hydrogen production apparatus according to claim 3, characterized in that, The liquid hydrogen production equipment also includes a first liquefaction tank. The valve assembly includes a first throttle valve, and the pipe assembly includes a third pipe assembly. The third pipe assembly includes a first exhaust pipe, a first drain pipe, and a second exhaust pipe. The first exhaust pipe is connected to the product hydrogen outlet and the first liquefaction tank. The first throttle valve is installed on the first exhaust pipe. High-pressure product hydrogen discharged from the product hydrogen outlet enters the first liquefaction tank after being throttled by the first throttle valve through the first exhaust pipe. Under the throttling action of the first throttle valve, the high-pressure product hydrogen is converted into medium-pressure liquid hydrogen and medium-pressure product hydrogen. Hydrogen gas is supplied through the first drain pipe connected to the first liquefaction tank. Medium-pressure liquid hydrogen is discharged from the first liquefaction tank through the first drain pipe. The first heat exchanger also forms a first reflux port. The second exhaust pipe is connected to the first reflux port and the first liquefaction tank. Medium-pressure product hydrogen gas in the first liquefaction tank enters the first heat exchanger through the second exhaust pipe. The medium-pressure product hydrogen gas entering the first heat exchanger from the first reflux port serves as a cooling medium for heat exchange with the raw material hydrogen gas. The medium-pressure product hydrogen gas after heat exchange with the raw material hydrogen gas serves as a gas source for circulating hydrogen gas and is discharged from the first cooling medium outlet.

5. The liquid hydrogen production apparatus according to claim 4, characterized in that, The third pipe assembly also includes a second drain pipe, and the valve assembly includes a third throttle valve. One end of the second drain pipe is connected to a pipe laid between the first outlet and the second throttle valve, and the other end is connected to the first liquefaction tank.

6. The liquid hydrogen production apparatus according to claim 5, characterized in that, The liquid hydrogen production equipment also includes a second intermediate hydrogen converter, which is installed on the pipeline flowing from the first outlet to the first liquefaction tank. The circulating hydrogen that flows into the first liquefaction tank through the second drain pipe undergoes intermediate hydrogen conversion in the second intermediate hydrogen converter.

7. The liquid hydrogen production apparatus according to any one of claims 4 to 6, characterized in that, The liquid hydrogen production equipment also includes a subcooling mechanism, which comprises a subcooler and a second liquefaction tank. The subcooler is installed inside the second liquefaction tank. A first drain pipe is connected to the subcooler and the first liquefaction tank. Medium-pressure liquid hydrogen flowing out of the first liquefaction tank flows into the subcooler through the first drain pipe. The pipe mechanism also includes a fourth pipe assembly, which comprises a third drain pipe and a return pipe. The third drain pipe is connected to the subcooler and a storage tank for storing liquid hydrogen. Part of the liquid hydrogen discharged from the subcooler enters the storage tank through the third drain pipe. The return pipe is connected to the third drain pipe and the second liquefaction tank. The valve assembly also includes a fourth throttle valve, which is installed on the return pipe. Part of the liquid hydrogen discharged from the subcooler enters the second liquefaction tank through the return pipe and the fourth throttle valve.

8. The liquid hydrogen production apparatus according to claim 7, characterized in that, The fourth tube assembly also includes a third exhaust pipe. The first heat exchanger forms a second inlet and a second outlet. The third exhaust pipe is connected to the second liquefaction tank and the second inlet. The low-pressure product hydrogen gas vaporized from the liquid hydrogen in the second liquefaction tank flows out through the third exhaust pipe and enters the first heat exchanger through the second inlet, and then exits from the second outlet.

9. The liquid hydrogen production apparatus according to claim 8, characterized in that, The first heat exchanger includes a third inlet, and the fourth tube group also includes a second cooling tube connected to the third drain pipe and the third inlet. The valve group also includes a fifth throttle valve installed on the second cooling tube. Part of the liquid hydrogen flowing out of the subcooler flows into the first heat exchanger from the second cooling tube through the fifth throttle valve, and then exits from the second outlet.

10. The method of operating the liquid hydrogen production apparatus according to any one of claims 1 to 9, characterized in that, include: The raw material hydrogen enters the first heat exchanger through the raw material inlet. A stream of circulating hydrogen entering the first heat exchanger exchanges heat with the raw material hydrogen entering the first heat exchanger and another stream of circulating hydrogen entering the first heat exchanger. After heat exchange, the raw material hydrogen is discharged from the first heat exchanger and enters the first positive and negative hydrogen converter through a pipeline, and then flows back to the first heat exchanger through a pipeline. The raw material hydrogen undergoes positive and negative hydrogen conversion in the first positive and negative hydrogen converter to produce high-pressure product hydrogen. The high-pressure product hydrogen is discharged from the product hydrogen outlet. The circulating hydrogen, heated by exchanging heat with the raw material hydrogen, flows into the cooling mechanism and, after its temperature is reduced, flows back to the first heat exchanger. The circulating hydrogen, after exchanging heat with the circulating hydrogen flowing through the cooling mechanism, flows out of the first heat exchanger and, after being throttled by the second throttle valve through the pipeline, returns to the first heat exchanger and exchanges heat with the raw material hydrogen.

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