Liquid hydrogen preparation system and method for processing boil-off gas

Abstract

The present invention provides a liquid hydrogen preparation system and method for processing boil-off gas, relating to the field of liquid hydrogen preparation. The system comprises: a pressure regulating unit, a pre-cooling unit, and a refrigeration unit, which are sequentially arranged along an airflow direction, wherein a raw hydrogen inlet is provided at an input end of the pressure regulating unit; a separation unit, which is connected to an output end of the refrigeration unit and is used to separate liquid hydrogen from hydrogen; a storage unit, which is connected to the separation unit and is used to store liquid hydrogen; and a boil-off gas pressurization processing unit, wherein an input end of the boil-off gas pressurization processing unit is connected to the separation unit and the storage unit, and an output end of the evaporator processing unit is connected to a flow pipeline of the refrigeration unit. Regasified hydrogen and non-liquefied hydrogen can be pressurized and returned to the refrigeration unit for liquefaction treatment, thereby achieving an overall liquefaction rate of the raw hydrogen of 100%. At the same time, sealed recovery of the regasified hydrogen and non-liquefied hydrogen is achieved, thereby reducing safety risks and preventing energy waste.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid hydrogen preparation, and more specifically, relates to a liquid hydrogen preparation system and method for processing boil-off gas. Background Art

[0002] As the global energy system gradually shifts from complex energies to clean energy, hydrogen energy, with its high energy density and pollution-free nature, has garnered widespread attention. 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] The key to promoting liquid hydrogen technology lies in reducing production costs. Hydrogen has a pressure of 101.325 kPa at normal pressure and a boiling point of -252.77°C. Currently, during the liquid hydrogen preparation process, unliquefied raw hydrogen will be produced at the end of the process. At the same time, the storage facilities of the product liquid hydrogen will inevitably produce regasified gas. If these two parts of gas (collectively referred to as boil-off gas) are not processed, it will bring huge energy waste and safety risks. Summary of the Invention

[0004] The purpose of the present invention is to address the deficiencies in the prior art and provide a liquid hydrogen production system and method for processing boil-off gas. In this system, unliquefied hydrogen and regasified hydrogen (collectively referred to as boil-off gas) enter a boil-off gas pressurization treatment unit together, are pressurized, and then return to the liquid hydrogen production process for liquefaction, thereby solving the problems of huge energy waste and safety risks.

[0005] In order to achieve the above object, the present invention provides a liquid hydrogen production system for processing boil-off gas, the system comprising:

[0006] A pressure regulating unit, a pre-cooling unit and a refrigeration unit are sequentially arranged along the airflow direction, and a raw hydrogen inlet is provided at the input end of the pressure regulating unit;

[0007] a separation unit connected to an output end of the refrigeration unit and configured to separate liquid hydrogen from hydrogen gas;

[0008] a storage unit, connected to the separation unit and configured to store liquid hydrogen;

[0009] A boil-off gas pressurization processing unit, wherein the input end of the boil-off gas pressurization processing unit is connected to the separation unit and the storage unit, and the output end of the evaporator processing unit is connected to the flow pipeline of the refrigeration unit, and is used to pressurize the regasified hydrogen in the storage unit and the non-liquefied hydrogen in the separation unit and return them to the refrigeration unit.

[0010] Optionally, the pressure regulating unit includes a hydrogen compressor and a pressure regulating pipeline, the output end of the pressure regulating pipeline is connected to the pre-cooling unit, and the hydrogen compressor is arranged on the pressure regulating pipeline.

[0011] Optionally, the pre-cooling unit includes a first pre-cooling cold box, a second pre-cooling cold box and a connecting pipeline, the two ends of the connecting pipeline are respectively connected to the pressure regulating unit and the refrigeration unit, the first pre-cooling cold box and the second pre-cooling cold box are connected to the connecting pipeline in sequence along the air flow direction, and the first pre-cooling cold box and the second pre-cooling cold box are used to load the first pre-cooling refrigerant and the second pre-cooling refrigerant, respectively.

[0012] Optionally, the refrigeration unit includes:

[0013] A refrigeration component connected between the pre-cooling unit and the separation unit;

[0014] A circulating pressure-reducing low-temperature component, which is connected to the refrigeration component and is used for pressure reduction and refrigeration of high-pressure circulating hydrogen;

[0015] A low-temperature compression component is connected to the circulating pressure-reducing low-temperature component and is used to compress low-pressure circulating hydrogen into high-pressure circulating hydrogen and perform a temperature reduction process.

[0016] Optionally, the refrigeration assembly includes a plurality of refrigeration cold boxes, which are arranged in sequence along the airflow direction, and the refrigeration cold boxes are connected to refrigeration pipelines;

[0017] The input end of the refrigeration pipeline at the head end is connected to the pre-cooling unit, the output end of the refrigeration pipeline at the tail end is connected to the separation unit, and adjacent refrigeration pipelines are connected;

[0018] A recooling pipeline is provided between some adjacent refrigeration pipelines, the output end of the front refrigeration pipeline of the adjacent refrigeration pipeline is connected to the input end of the matched recooling pipeline, the input end of the rear refrigeration pipeline of the adjacent refrigeration pipeline is connected to the output end of the matched recooling pipeline, and the recooling pipeline between the adjacent refrigeration pipelines is provided in the refrigeration cold box connected to the rear refrigeration pipeline;

[0019] The recooling pipeline is connected to a para-hydrogen converter, and the refrigeration pipeline at the head end and close to the precooling unit is also provided with a para-hydrogen converter;

[0020] Some of the refrigeration pipelines are connected with raw hydrogen throttling parts.

[0021] Optionally, the circulating pressure-reducing low-temperature component includes a high-pressure circulating hydrogen pipeline, a first low-pressure circulating hydrogen pipeline, a second low-pressure circulating hydrogen pipeline, a circulating hydrogen separator and a circulating hydrogen throttling device. The high-pressure circulating hydrogen pipeline, the first low-pressure circulating hydrogen pipeline and the second low-pressure circulating hydrogen pipeline are all connected to the remaining refrigeration cold boxes except the terminal refrigeration cold box. The input end of the high-pressure circulating hydrogen pipeline is connected to the output end of the low-temperature compression assembly, the output end of the high-pressure circulating hydrogen pipeline is connected to the inlet of the circulating hydrogen separator, the liquid phase outlet and the gas phase outlet of the circulating hydrogen separator are both connected to the input end of the second low-pressure circulating hydrogen pipeline, the pipeline between the liquid phase outlet of the circulating hydrogen separator and the input end of the second low-pressure circulating hydrogen pipeline passes through the terminal refrigeration cold box, and the circulating hydrogen throttling device is arranged on the high-pressure circulating hydrogen pipeline and close to the circulating hydrogen separator.

[0022] One end of a plurality of branch pipelines is connected to the high-pressure circulating hydrogen pipeline, the other ends of the plurality of branch pipelines are connected to the first low-pressure circulating hydrogen pipeline, and a circulating hydrogen expander is provided on each of the plurality of branch pipelines.

[0023] Optionally, the low-temperature compression component includes a circulating hydrogen compressor, high- and low-pressure circulating hydrogen precooling pipelines and a circulating hydrogen precooling box. The input end and the output end of the high- and low-pressure circulating hydrogen precooling pipelines are respectively connected to the input end and the output end of the circulating pressure-reducing low-temperature component. The circulating hydrogen compressor and the circulating hydrogen precooling box are arranged in sequence on the high- and low-pressure circulating hydrogen precooling pipelines along the air flow direction. The circulating hydrogen precooling box is used to load refrigerant.

[0024] Optionally, the evaporated gas pressurization treatment unit includes an ejector booster, which includes an ejector hydrogen inlet, a high-pressure hydrogen inlet and a mixed hydrogen outlet. The ejector hydrogen inlet is connected to the gas phase outlet of the separation unit and the regasified hydrogen outlet of the storage unit, the high-pressure hydrogen inlet is connected to the high-pressure position of the hydrogen pipeline of the refrigeration component, and the mixed hydrogen outlet is connected to the low-pressure position of the hydrogen pipeline of the refrigeration component.

[0025] The present invention provides a method for preparing liquid hydrogen by treating boil-off gas, utilizing the above-mentioned system for preparing liquid hydrogen by treating boil-off gas, the method comprising:

[0026] Step 1: Inputting the raw hydrogen into the pressure regulating unit for pressurization to obtain high-pressure raw hydrogen;

[0027] Step 2: Input the high-pressure raw hydrogen into the pre-cooling unit to absorb cold energy and perform pre-cooling;

[0028] Step 3: The pre-cooled high-pressure raw hydrogen gas is fed into a refrigeration unit for refrigeration, cooling, and decompression to produce liquid hydrogen and unliquefied hydrogen gas;

[0029] Step 4: Input the liquid hydrogen and the unliquefied hydrogen into a separation unit for separation, and store the liquid hydrogen;

[0030] Step 5: The separated unliquefied hydrogen and the regasified hydrogen of the liquid hydrogen are input into the boil-off gas pressurization processing unit, and after pressurization, they are returned to the refrigeration unit, and steps 3 to 5 are repeated to continue participating in the liquid hydrogen preparation process.

[0031] Optionally, the first low-pressure circulating hydrogen is combined with the second low-pressure circulating hydrogen and enters the circulating hydrogen compressor at a low temperature to generate high-pressure circulating hydrogen;

[0032] The high-pressure circulating hydrogen is input into the circulating hydrogen pre-cooling box to absorb the cold energy and reduce the temperature;

[0033] The cooled high-pressure circulating hydrogen passes through the refrigeration component and then enters the circulating hydrogen throttling component and the circulating hydrogen separation component in sequence to produce circulating liquid hydrogen;

[0034] When the circulating liquid hydrogen passes through the refrigeration component in reverse, it absorbs heat and then flows into the first low-pressure circulating hydrogen;

[0035] The second low-pressure circulating hydrogen led from the high-pressure circulating hydrogen pipeline merges with the first low-pressure circulating hydrogen.

[0036] The present invention provides a liquid hydrogen production system and method for processing boil-off gas, which has the following beneficial effects:

[0037] 1. To meet the needs of large-scale liquid hydrogen production (usually more than 30 tons of liquid hydrogen per day), the system is sequentially equipped with a pressure regulating unit, a pre-cooling unit, and a refrigeration unit along the airflow direction. The raw hydrogen passes through the pressure regulating unit, the pre-cooling unit, and the refrigeration unit in sequence to produce liquid hydrogen and non-liquefied hydrogen. The liquid hydrogen and the non-liquefied hydrogen are separated in the separation unit. The separated liquid hydrogen will flow into the storage unit for storage. At this time, the non-liquefied hydrogen and the regasified hydrogen in the storage unit enter the boil-off gas pressurization treatment unit for treatment. The regasified hydrogen and the non-liquefied hydrogen are pressurized and returned to the refrigeration unit for liquefaction treatment, so that the overall liquefaction rate of the raw hydrogen reaches 100%. At the same time, the regasified hydrogen and the non-liquefied hydrogen are recovered in a closed manner, reducing safety risks and preventing energy waste.

[0038] 2. The system's cryogenic compression component is connected to the circulating pressure-reducing cryogenic component. After the first low-pressure circulating hydrogen and the second low-pressure circulating hydrogen merge, they enter the cryogenic compression component at a low temperature to form high-pressure circulating hydrogen, which greatly reduces the power consumption of the cryogenic pressure component.

[0039] 3. This method utilizes a liquid hydrogen preparation system that processes boil-off gas, which not only improves the overall liquefaction rate but also greatly reduces the power consumption of cryogenic compression components, contributing to the promotion of liquid hydrogen preparation technology.

[0040] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] 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.

[0042] Figure 1 A schematic structural diagram of a liquid hydrogen production system for processing boil-off gas according to an embodiment of the present invention is shown.

[0043] Figure 2 A schematic flow chart of a method for preparing liquid hydrogen by treating boil-off gas according to an embodiment of the present invention is shown.

[0044] 1. Pressure regulating unit; 2. Pre-cooling unit; 3. Separation unit; 4. Storage unit; 5. Evaporation gas pressurization treatment unit; 6. Hydrogen compressor; 7. Pressure regulating pipeline; 8. First pre-cooling cold box; 9. Second pre-cooling cold box; 10. Connecting pipeline; 11. Refrigeration component; 12. Cyclic pressure reduction low-temperature component; 13. Low-temperature compression component; 14. First refrigeration cold box; 15. Second refrigeration cold box; 16. Third refrigeration cold box; 17. Fourth refrigeration cold box; 18. Fifth refrigeration cold box; 19. First refrigeration pipeline; 20. Second refrigeration pipeline; 21. Third refrigeration pipeline; 22. Fourth refrigeration pipeline; 23. Fifth refrigeration pipeline; 24. First recooling pipeline; 25. Second recooling pipeline; 26. The third recooling pipeline; 27, the normal-parahydrogen converter; 28, the raw hydrogen throttling device; 29, the first pre-cooling refrigerant pre-cooling pipeline; 30, the high-pressure circulating hydrogen pipeline; 31, the first low-pressure circulating hydrogen pipeline; 32, the second low-pressure circulating hydrogen pipeline; 33, the circulating hydrogen separator; 34, the circulating hydrogen throttling device; 35, the fourth recooling pipeline; 36, the fifth recooling pipeline; 37, the sixth recooling pipeline; 38, the circulating hydrogen expander; 39, the circulating hydrogen compressor; 40, the high- and low-pressure circulating hydrogen pre-cooling pipelines; 41, the sixth refrigeration cold box; 42, the seventh refrigeration cold box; 43, the ejector booster; 44, the second pre-cooling refrigerant pre-cooling pipeline; 45, the first refrigeration refrigerant refrigeration pipeline; 46, the second refrigeration refrigerant refrigeration pipeline. DETAILED DESCRIPTION

[0045] 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.

[0046] like Figure 1As shown, the present invention provides a liquid hydrogen production system for processing boil-off gas, the system comprising:

[0047] The pressure regulating unit 1, the pre-cooling unit 2 and the refrigeration unit are sequentially arranged along the airflow direction, and the input end of the pressure regulating unit 1 is provided with a raw hydrogen inlet;

[0048] A separation unit 3 is connected to the output end of the refrigeration unit and is used to separate liquid hydrogen from hydrogen gas;

[0049] Storage unit 4, which is connected to separation unit 3 and is used to store liquid hydrogen;

[0050] The boil-off gas pressurization processing unit 5 has an input end connected to the separation unit 3 and the storage unit 4, and an output end of the evaporator processing unit 5 is connected to the flow pipeline of the refrigeration unit, and is used to pressurize the regasified hydrogen in the storage unit 4 and the non-liquefied hydrogen in the separation unit and return them to the refrigeration unit.

[0051] Specifically, the system is sequentially provided with a pressure regulating unit 1, a pre-cooling unit 2 and a refrigeration unit along the airflow direction. The raw hydrogen is pressure-regulated by the pressure regulating unit 1, and then passes through the pre-cooling unit 2 and the refrigeration unit to produce liquid hydrogen and non-liquefied hydrogen. The liquid hydrogen and the non-liquefied hydrogen are separated by the separation unit 3. The separated liquid hydrogen will flow into the storage unit 4 for storage. At this time, the non-liquefied hydrogen and the regasified hydrogen in the storage unit (collectively referred to as boil-off gas) enter the boil-off gas pressurization treatment unit 5 for treatment. The regasified hydrogen and the non-liquefied hydrogen are pressurized and returned to the refrigeration unit for liquefaction treatment, so that the overall liquefaction rate of the raw hydrogen reaches 100%. At the same time, the regasified hydrogen and the non-liquefied hydrogen are hermetically recovered, reducing safety risks and preventing energy waste.

[0052] Optionally, the pressure regulating unit 1 includes a hydrogen compressor 6 and a pressure regulating pipeline 7 , the output end of the pressure regulating pipeline 7 is connected to the pre-cooling unit 2 , and the hydrogen compressor 6 is arranged on the pressure regulating pipeline 7 .

[0053] Specifically, the raw hydrogen is transported to the hydrogen compressor 6 through the pressure regulating pipeline 7. The hydrogen compressor 6 is used to adjust the pressure of the raw hydrogen to obtain high-pressure raw hydrogen. The high-pressure raw hydrogen is 2.0 to 3.5 MPa (A). The raw hydrogen is purified hydrogen.

[0054] Optionally, the precooling unit 2 includes a first precooling cold box 8, a second precooling cold box 9 and a connecting pipe 10, both ends of the connecting pipe 10 are respectively connected to the pressure regulating unit 1 and the refrigeration unit, the first precooling cold box 8 and the second precooling cold box 9 are connected to the connecting pipe 10 in sequence along the air flow direction, and the first precooling cold box 8 and the second precooling cold box 9 are respectively used to load the first precooling refrigerant and the second precooling refrigerant.

[0055] Optionally, the precooling unit 2 also includes a first precooling refrigerant precooling pipeline 30 and a second precooling refrigerant precooling pipeline 44, the first precooling refrigerant precooling pipeline 30 is connected to the first precooling cold box 8, and is used to input the first precooling refrigerant into the first precooling cold box 8, and the second precooling refrigerant precooling pipeline 44 is connected to the first precooling cold box 8 and the second precooling cold box 9, and is used to input the second precooling refrigerant into the second precooling cold box 8 and the first precooling cold box 9 in sequence.

[0056] Specifically, the first pre-cooling refrigerant and the second pre-cooling refrigerant provide cooling capacity for the first pre-cooling cold box 8 and the second pre-cooling cold box 9 respectively. When the raw hydrogen passes through the connecting pipeline 10, it absorbs cooling capacity and the temperature drops to 80K, completing the pre-cooling stage of the raw hydrogen. LNG and supercooled nitrogen are the first pre-cooling agent, and liquid nitrogen is the second pre-cooling agent.

[0057] Optionally, the refrigeration unit comprises:

[0058] Refrigeration component 11, refrigeration component 11 is connected between pre-cooling unit 2 and separation unit 3;

[0059] The circulating pressure-reducing low-temperature component 12 is connected to the refrigeration component 11 and is used for reducing the pressure of high-pressure circulating hydrogen;

[0060] The low-temperature compression component 13 is connected to the circulating pressure-reducing low-temperature component 12 and is used to compress the low-pressure circulating hydrogen into high-pressure circulating hydrogen and perform a temperature reduction process.

[0061] Optionally, the refrigeration assembly 11 includes a plurality of refrigeration cold boxes, which are arranged in sequence along the airflow direction, and refrigeration pipelines are connected to the refrigeration cold boxes;

[0062] The input end of the refrigeration pipeline at the head end is connected to the pre-cooling unit 2, the output end of the refrigeration pipeline at the tail end is connected to the separation unit, and adjacent refrigeration pipelines are connected;

[0063] A recooling pipeline is provided between some adjacent refrigeration pipelines, the output end of the front refrigeration pipeline of the adjacent refrigeration pipeline is connected to the input end of the matching recooling pipeline, the input end of the rear refrigeration pipeline of the adjacent refrigeration pipeline is connected to the output end of the matching recooling pipeline, and the recooling pipeline between the adjacent refrigeration pipelines is arranged in the refrigeration cold box connected to the rear refrigeration pipeline;

[0064] The recooling pipeline is connected to a para-hydrogen converter 27, and a para-hydrogen converter 27 is also provided on the refrigeration pipeline at the head end and near the precooling unit 2;

[0065] A raw hydrogen throttling element 28 is connected to part of the refrigeration pipeline.

[0066] Optionally, the refrigeration assembly 11 includes a first refrigeration cold box 14, a second refrigeration cold box 15, a third refrigeration cold box 16, a fourth refrigeration cold box 17 and a fifth refrigeration cold box 18, which are respectively connected to a first refrigeration pipeline 19, a second refrigeration pipeline 20, a third refrigeration pipeline 21, a fourth refrigeration pipeline 22 and a fifth refrigeration pipeline 23;

[0067] The first refrigeration cold box 14 is further connected to a first recooling pipeline 24, the input end of the first refrigeration pipeline 19 is connected to the precooling unit 2, the output end of the first refrigeration pipeline 19 is connected to the input end of the first recooling pipeline 24, the output end of the first recooling pipeline 24 is connected to the input end of the second refrigeration pipeline 20, and the output end of the second refrigeration pipeline 20 is connected to the input end of the third refrigeration pipeline 21;

[0068] The fourth refrigeration cold box 17 is further connected to a second recooling pipeline 25, the output end of the third refrigeration pipeline 21 is connected to the input end of the second recooling pipeline 25, and the output end of the second recooling pipeline 25 is connected to the input end of the fourth refrigeration pipeline 22;

[0069] The fifth refrigeration cold box 18 is further connected to a third recooling pipeline 26, the output end of the fourth refrigeration pipeline 22 is connected to the input end of the third recooling pipeline 26, the output end of the third recooling pipeline 26 is connected to the input end of the fifth refrigeration pipeline 23, and the output end of the fifth refrigeration pipeline 23 is connected to the separation unit 3;

[0070] The first recooling pipeline 24, the second recooling pipeline 25 and the third recooling pipeline 26 are all connected to a para-hydrogen converter 27. The first refrigeration pipeline 19 is also provided with a para-hydrogen converter 27 between the precooling unit 2 and the first refrigeration cold box 14.

[0071] A raw hydrogen throttle 28 is provided on the third refrigeration pipeline 21 and between the third refrigeration cold box 16 and the fourth refrigeration cold box 17 . A raw hydrogen throttle 28 is also provided on the fifth refrigeration pipeline 23 and between the fifth refrigeration cold box 18 and the separation unit 3 .

[0072] Specifically, after the raw hydrogen completes the pre-cooling stage, it first enters the positive-para-hydrogen converter 27 on the first refrigeration pipeline 19. The catalyst is filled in the positive-para-hydrogen converter 27. Under the action of the catalyst, the first-level positive-para-hydrogen conversion is completed. During the positive-para-hydrogen conversion process, the raw hydrogen absorbs the conversion heat and the temperature rises; then the raw hydrogen enters the first refrigeration cold box 14 and the second refrigeration cold box 15 in sequence, and the temperature decreases after absorbing the cold. Then, the raw hydrogen enters the positive-para-hydrogen converter 27 on the first recooling pipeline 24 to complete the secondary positive-para-hydrogen conversion. The raw hydrogen that completes the secondary positive-para-hydrogen conversion returns to the second refrigeration box 15 again, absorbs the cold and reduces the temperature. Then, according to the flow direction, the raw hydrogen enters the third refrigeration cold box 16, the fourth refrigeration cold box 17, the positive-para-hydrogen converter 27 on the second recooling pipeline 21, the fourth refrigeration cold box 17, the fifth refrigeration cold box 16, the The cold box 18, the normal-parahydrogen converter 27 on the third recooling line 25, and the fifth refrigeration cold box 18 continuously absorb cold energy in the cold box, reduce the temperature, and complete the third and fourth stage normal-parahydrogen conversion. The raw hydrogen temperature leaving the fifth refrigeration cold box 18 is 25K and the parahydrogen ratio is 98.7%. In the above process, after leaving the third refrigeration cold box 16, the raw hydrogen enters the raw hydrogen throttle 28 on the third refrigeration line 21, completes the primary throttling, and the pressure drops to 0.5-1.0 MPa (A), producing medium-pressure raw hydrogen. After leaving the fifth refrigeration cold box 18, the raw hydrogen enters the raw hydrogen throttle 28 on the fifth refrigeration line 16, completes the final throttling, and the pressure drops to 0.1-0.12 MPa (A), which is 0.12 MPa (A) in this embodiment. At the same time, the temperature drops to 20.8K, producing 89.4v1% liquid hydrogen.

[0073] Optionally, the circulating decompression low-temperature component 13 includes a high-pressure circulating hydrogen pipeline 30, a first low-pressure circulating hydrogen pipeline 31, a second low-pressure circulating hydrogen pipeline 32, a circulating hydrogen separator 33 and a circulating hydrogen throttling device 34. The high-pressure circulating hydrogen pipeline 30, the first low-pressure circulating hydrogen pipeline 31 and the second low-pressure circulating hydrogen pipeline 32 are all connected to the remaining refrigeration cold boxes except the terminal refrigeration cold box. The input end of the high-pressure circulating hydrogen pipeline 30 is connected to the output end of the low-temperature compression component 13, the output end of the high-pressure circulating hydrogen pipeline 30 is connected to the inlet of the circulating hydrogen separator 33, the liquid phase outlet and the gas phase outlet of the circulating hydrogen separator 33 are both connected to the input end of the second low-pressure circulating hydrogen pipeline 32, the pipeline between the liquid phase outlet of the circulating hydrogen separator 33 and the input end of the second low-pressure circulating hydrogen pipeline 32 passes through the terminal refrigeration cold box, and the circulating hydrogen throttling device 34 is arranged on the high-pressure circulating hydrogen pipeline 30 and close to the circulating hydrogen separator 33.

[0074] One end of a plurality of branch pipelines is connected to the high-pressure circulating hydrogen pipeline 30 , and the other ends of the plurality of branch pipelines are connected to the first low-pressure circulating hydrogen pipeline 31 . A circulating hydrogen expander 38 is provided on each of the plurality of branch pipelines.

[0075] Optionally, the first refrigeration cold box 14, the second refrigeration cold box 15, the third refrigeration cold box 16, and the fourth refrigeration cold box 17 are sequentially connected to the high-pressure circulating hydrogen pipeline 30 along the airflow direction, the fourth refrigeration cold box 17, the third refrigeration cold box 16, the second refrigeration cold box 15 and the first refrigeration cold box 14 are sequentially connected to the first low-pressure circulating hydrogen pipeline 31 and are also sequentially connected to the second low-pressure circulating hydrogen pipeline 32 along the airflow direction, the input end of the high-pressure circulating hydrogen pipeline 30 is connected to the output end of the low-temperature compression assembly 13, the output end of the high-pressure circulating hydrogen pipeline 30 is connected to the inlet of the circulating hydrogen separator 33, the liquid phase outlet and the gas phase outlet of the circulating hydrogen separator 33 are both connected to the input end of the second low-pressure circulating hydrogen pipeline 32, the pipeline between the liquid phase outlet of the circulating hydrogen separator 33 and the input end of the second low-pressure circulating hydrogen pipeline 32 passes through the fifth refrigeration cold box 18, and the circulating hydrogen throttling device 34 is provided on the high-pressure circulating hydrogen pipeline 30 and is located at the fourth refrigeration cold box 17 and the circulating hydrogen separator 33, one end of a fourth recooling pipeline 35 is connected to the high-pressure circulating hydrogen pipeline 30 and is located between the second refrigeration cold box 15 and the third refrigeration cold box 16, and the other end of the fourth recooling pipeline 35 is connected to the input end of the first low-pressure circulating hydrogen pipeline 31, and one end of a fifth recooling pipeline 36 is connected to the high-pressure circulating hydrogen pipeline 30 and is located between the first refrigeration cold box 14 and the second refrigeration cold box 15, the other end of the fifth recooling pipeline 36 is connected to the first low-pressure circulating hydrogen pipeline 31 and is located between the fourth refrigeration cold box 17 and the fifth refrigeration cold box 18, the input end of the high-pressure circulating hydrogen pipeline 30 is connected to the sixth recooling pipeline 37, and the output end of the sixth recooling pipeline 37 is connected to the first low-pressure circulating hydrogen pipeline 31 and is located between the second refrigeration cold box 15 and the third refrigeration cold box 16, and a circulating hydrogen expander 38 is provided on the fourth recooling pipeline 35, the fifth recooling pipeline 36 and the sixth recooling pipeline 37.

[0076] Specifically, hydrogen is used as the circulating refrigeration refrigerant, and the pressures of the first low-pressure circulating hydrogen and the second low-pressure circulating hydrogen are both 0.1-0.2 MPa(A), and in this embodiment, 0.15 MPa(A), so as to correspondingly reduce the pressure of the high-pressure circulating hydrogen, thereby reducing equipment and pipeline investment. The high-pressure circulating hydrogen pressure is 1.8-2.4 MPa(A), and in this embodiment, 1.8 MPa(A); the first low-pressure circulating hydrogen, the second low-pressure circulating hydrogen, and the high-pressure circulating hydrogen constitute a hydrogen refrigeration cycle;

[0077] After being output from the cryogenic compression assembly 13, the high-pressure circulating hydrogen enters the high-pressure circulating hydrogen pipeline 30 for transporting the high-pressure circulating hydrogen. The input end of the high-pressure circulating hydrogen pipeline 30 is connected to the output end of the cryogenic compression assembly 13. The high-pressure circulating hydrogen pipeline 30 is also provided with a circulating hydrogen throttling device 34 for completing the pressure reduction and refrigeration of the high-pressure circulating hydrogen to produce circulating liquid hydrogen. The liquid phase outlet of the circulating hydrogen separator 33 is connected to the input end of the second low-pressure circulating hydrogen pipeline 32. The pipeline between the liquid phase outlet of the circulating hydrogen separator 33 and the input end of the second low-pressure circulating hydrogen pipeline 32 passes through the fifth refrigeration cold box 18. The circulating liquid hydrogen absorbs heat and then flows into the second low-pressure circulating hydrogen.

[0078] The fourth refrigeration cold box 17, the third refrigeration cold box 16, the second refrigeration cold box 15 and the first refrigeration cold box 14 are connected to the first low-pressure circulating hydrogen pipeline 31 in sequence along the air flow direction and are also connected to the second low-pressure circulating pipeline 32 in sequence, providing cooling capacity for the fourth refrigeration cold box 17, the third refrigeration cold box 16, the second refrigeration cold box 15 and the first refrigeration cold box 14.

[0079] Optionally, the low-temperature compression component 13 includes a circulating hydrogen compressor 39, high- and low-pressure circulating hydrogen precooling pipelines 40 and a circulating hydrogen precooling box. The input end and the output end of the high- and low-pressure circulating hydrogen precooling pipelines 40 are respectively connected to the input end and the output end of the circulating pressure-reducing low-temperature component 12. The circulating hydrogen compressor 39 and the circulating hydrogen precooling box are arranged in sequence on the high- and low-pressure circulating hydrogen precooling pipelines 40 along the air flow direction. The circulating hydrogen precooling box is used to load the refrigerant.

[0080] Optionally, the circulating hydrogen pre-cooling box includes a sixth refrigeration box 41 and a seventh refrigeration box 42, the input end and the output end of the high and low pressure circulating hydrogen pre-cooling pipeline 40 are respectively connected to the input end and the output end of the circulating pressure reduction low temperature component 12, the circulating hydrogen compressor 39, the sixth refrigeration box 41 and the seventh refrigeration box 42 are arranged in sequence on the high and low pressure circulating hydrogen pre-cooling pipeline 40 along the air flow direction, and the sixth refrigeration box 41 and the seventh refrigeration box 42 are used to load the first refrigerant and the second refrigerant, respectively.

[0081] Optionally, the low-temperature compression assembly also includes a first refrigeration refrigerant refrigeration pipeline and a second refrigeration refrigerant refrigeration pipeline, the first refrigeration refrigerant refrigeration pipeline 45 is connected to the sixth refrigeration cold box 41, for inputting the first refrigeration refrigerant into the sixth refrigeration cold box 41, the second refrigeration refrigerant refrigeration pipeline 46 is connected to the seventh refrigeration cold box 42, for inputting the first refrigeration refrigerant into the sixth refrigeration cold box 41, and the output end of the second refrigeration refrigerant refrigeration pipeline 46 is connected to the second pre-cooling refrigerant pre-cooling pipeline 44 at a position between the first pre-cooling cold box 8 and the second pre-cooling cold box 9.

[0082] Specifically, the first low-pressure circulating hydrogen and the second low-pressure circulating hydrogen are combined and enter the circulating hydrogen compressor 39 in a low-temperature state to produce high-pressure circulating hydrogen. The inlet temperature of the circulating hydrogen compressor 39 is 70-130K, and is 86K in this embodiment. Correspondingly, the high-pressure circulating hydrogen leaving the circulating hydrogen compressor 39 enters the sixth refrigeration cold box 41 and the seventh refrigeration cold box 42 in turn to absorb cold energy, and the temperature drops to 92K. LNG is used as the first refrigerant to provide cold energy in the sixth refrigeration cold box 41, and liquid nitrogen is used as the second refrigerant to provide cold energy in the seventh refrigeration cold box 42.

[0083] Optionally, the evaporated gas pressurization treatment unit 5 includes an ejector booster 43, which includes an ejector hydrogen inlet, a high-pressure hydrogen inlet and a mixed hydrogen outlet. The ejector hydrogen inlet is connected to the gas phase outlet of the separation unit 3 and the regasified hydrogen outlet of the storage unit 4, the high-pressure hydrogen inlet is connected to the high-pressure position of the hydrogen pipeline of the refrigeration component 11, and the mixed hydrogen outlet is connected to the low-pressure position of the hydrogen pipeline of the refrigeration component 11.

[0084] Specifically, after the final stage of throttling, liquid hydrogen and unliquefied hydrogen are generated. The liquid hydrogen and unliquefied hydrogen enter the separation unit 3. After separation, a liquid hydrogen product is obtained. The liquid hydrogen product enters the storage unit 4. The unliquefied hydrogen and regasified hydrogen (collectively referred to as boil-off gas) generated in the separation unit 3 and the storage unit 4 are introduced into the ejector booster 43, pressurized, and merged with the medium-pressure raw hydrogen gas before entering the fourth refrigeration cold box 17.

[0085] An ejector booster 43 is used to treat the boil-off gas, and the ejector booster 43 adopts a first-stage ejection. In coordination, the pressure of the raw hydrogen is adjusted by the pressure regulating unit 1 to 2.4 MPa(A). The raw hydrogen throttle 28 on the third refrigeration line 21 is used to adjust the raw hydrogen pressure again to 0.7 MPa(A). The ejector booster 43 draws a portion of the high-pressure raw hydrogen from the second refrigeration line 20 as a power source, and the unliquefied hydrogen and regasified hydrogen (collectively referred to as boil-off gas) are used as the ejected gas. The two exchange energy in the ejector booster 43. After the pressure of the unliquefied hydrogen and regasified hydrogen (collectively referred to as boil-off gas) increases, they merge with the raw hydrogen leaving the raw hydrogen throttle 28 on the third refrigeration line 21 and enter the fourth refrigeration cold box 17 together to continue participating in the liquid hydrogen preparation process.

[0086] Optionally, the ejector booster 43 is a first-stage ejector, and the ejector booster 43 is composed of an expansion chamber, a mixing chamber, and a diffusion chamber. The regasified hydrogen gas outlet of the storage unit 4 is provided with a pressure detection device and a first regulating valve;

[0087] Specifically, the first regulating valve and the pressure detection device form a chain mechanism to control the discharge flow rate of the regasified hydrogen outlet.

[0088] Optionally, the inlets and outlets of the first pre-cooling cold box 8, the second pre-cooling cold box 9, the first refrigeration cold box 14, the second refrigeration cold box 15, the third refrigeration cold box 16, the fourth refrigeration cold box 17, the fifth refrigeration cold box 18, the sixth refrigeration cold box 41 and the seventh refrigeration cold box 42 are all provided with a first temperature detection instrument, and the inlet of the circulating hydrogen expander is provided with a flow detection instrument and a second regulating valve;

[0089] Specifically, the first temperature detection instrument, the flow detection instrument and the second regulating valve form a chain mechanism for adjusting the inlet and outlet temperatures of the first refrigeration cold box 14, the second refrigeration cold box 15, the third refrigeration cold box 16 and the fourth refrigeration cold box 17 by controlling the flow in and out of the circulating hydrogen expander.

[0090] Optionally, the ortho-para-hydrogen converter 27 is placed in an insulated box, including a converter cavity, a para-hydrogen content analyzer, and a second temperature detection instrument. The ortho-para-hydrogen converter 27 is filled with a catalyst to complete the ortho-para-hydrogen conversion of the raw hydrogen.

[0091] like Figure 2 As shown, the present invention provides a method for producing liquid hydrogen by treating boil-off gas, using the above-mentioned system for producing liquid hydrogen by treating boil-off gas, the method comprising:

[0092] Step 1: Input the raw hydrogen into the pressure regulating unit 1 for pressurization to obtain high-pressure raw hydrogen;

[0093] Step 2: The high-pressure raw hydrogen is fed into the pre-cooling unit 2 to absorb the cold energy and perform pre-cooling;

[0094] Step 3: The pre-cooled high-pressure raw hydrogen gas is fed into a refrigeration unit for refrigeration, cooling, and decompression to produce liquid hydrogen and unliquefied hydrogen gas;

[0095] Step 4: Input the liquid hydrogen and the unliquefied hydrogen into the separation unit 3 for separation, and store the liquid hydrogen;

[0096] Step 5: The separated unliquefied hydrogen and the regasified hydrogen of the liquid hydrogen are input into the boil-off gas pressurization processing unit 5, and after pressurization, they are returned to the refrigeration unit, and steps 3 to 5 are repeated to continue participating in the liquid hydrogen preparation process.

[0097] Optionally, the first low-pressure circulating hydrogen is combined with the second low-pressure circulating hydrogen and enters the circulating hydrogen compressor 39 at a low temperature to generate high-pressure circulating hydrogen;

[0098] The high-pressure circulating hydrogen is input into the circulating hydrogen pre-cooling box to absorb the cold energy and the temperature is reduced to 92K;

[0099] After the temperature has been reduced, the high-pressure circulating hydrogen passes through the refrigeration component 11 and then enters the circulating hydrogen throttling element 34 and the circulating hydrogen separation element 33 in sequence to produce circulating liquid hydrogen.

[0100] When the circulating liquid hydrogen passes through the refrigeration component 11 in the reverse direction, it absorbs heat and then flows into the first low-pressure circulating hydrogen;

[0101] The second low-pressure circulating hydrogen led from the high-pressure circulating hydrogen pipeline merges with the first low-pressure circulating hydrogen.

[0102] In summary, when the method for preparing liquid hydrogen by treating boil-off gas provided by the present invention is implemented, the liquid hydrogen preparation system for treating boil-off gas described above is used, and a single treatment is taken as an example: the raw hydrogen is transported to the hydrogen compressor 6 through the pressure regulating pipeline 7, and the hydrogen compressor 6 is used to regulate the pressure of the raw hydrogen to obtain high-pressure raw hydrogen. The high-pressure raw hydrogen is 2.0-3.5 MPa (A), and then the raw hydrogen passes through the first pre-cooling cold box 8 and the second pre-cooling cold box 9 to absorb the cold energy and reduce the temperature to 80K, completing the pre-cooling stage of the raw hydrogen. After the raw hydrogen completes the pre-cooling stage, it first enters the positive pressure on the first refrigeration pipeline 19. The para-hydrogen converter 27 is filled with a catalyst, and the first-level para-hydrogen conversion is completed under the action of the catalyst. During the para-hydrogen conversion process, the raw hydrogen absorbs the conversion heat and the temperature rises. Then the raw hydrogen enters the first refrigeration cold box 14 and the second refrigeration cold box 15 in sequence, and the temperature decreases after absorbing the cold. Then the raw hydrogen enters the para-hydrogen converter 27 on the first recooling line 24 to complete the second-level para-hydrogen conversion. The raw hydrogen that completes the second-level para-hydrogen conversion returns to the second refrigeration box 15 again, and the temperature decreases after absorbing the cold. Then, according to the flow direction, the raw hydrogen enters The third refrigeration cold box 16, the fourth refrigeration cold box 17, the normal-para-hydrogen converter 27 on the second recooling line 21, the fourth refrigeration cold box 17, the fifth refrigeration cold box 18, the normal-para-hydrogen converter 27 on the third recooling line 25, and the fifth refrigeration cold box 18 continuously absorb cold energy in the cold box, reduce the temperature, and complete the third and fourth stages of normal-para-hydrogen conversion. The raw hydrogen temperature leaving the fifth refrigeration cold box 18 is 25K and the para-hydrogen ratio is 98.7%. In the above process, after leaving the third refrigeration cold box 16, the raw hydrogen enters the raw hydrogen throttling device 28 on the third refrigeration line 21 to complete the primary throttling. The pressure is reduced to 0.5-1.0 MPa(A), producing medium-pressure raw hydrogen. After leaving the fifth refrigeration cold box 18, the raw hydrogen enters the raw hydrogen throttling device 28 on the fifth refrigeration pipeline 16, completing the final throttling, and the pressure is reduced to 0.12 MPa(A). At the same time, the temperature is reduced to 20.8K, producing 89.4% liquid hydrogen. At the same time, hydrogen is used as the circulating refrigerant. The pressure of the first low-pressure circulating hydrogen and the second low-pressure circulating hydrogen are both 0.15 MPa(A), so as to reduce the high-pressure circulating hydrogen pressure accordingly, thereby reducing equipment and pipeline investment. The high-pressure circulating hydrogen pressure is 1.8MPa(A), the first low-pressure circulating hydrogen merges with the second low-pressure circulating hydrogen and enters the circulating hydrogen compressor 39 in a low-temperature state to produce high-pressure circulating hydrogen. In coordination, the high-pressure circulating hydrogen leaving the circulating hydrogen compressor 39 enters the sixth refrigeration cold box 41 and the seventh refrigeration cold box 42 in turn to absorb cold energy, and the temperature drops to 92K, and then enters the high-pressure circulating hydrogen pipeline 30. The input end of the high-pressure circulating hydrogen pipeline 30 is connected to the output end of the low-temperature compression assembly 13, and a circulating hydrogen throttling device 34 is also provided on the high-pressure circulating hydrogen pipeline 30 to complete the cycle. The high-pressure circulating hydrogen is depressurized and refrigerated to produce circulating liquid hydrogen. The circulating liquid hydrogen enters the second low-pressure circulating hydrogen pipeline 32 to liquefy and absorb heat. The second low-pressure circulating hydrogen generated is merged with the first low-pressure circulating hydrogen and enters the circulating hydrogen compressor 39 at a low temperature. Then, the above-mentioned cycle process is repeated. Since the fourth refrigeration cold box 17, the third refrigeration cold box 16, the second refrigeration cold box 15 and the first refrigeration cold box 14 are sequentially connected to the first low-pressure circulating hydrogen pipeline 31 and are also sequentially connected to the second low-pressure circulating pipeline 32 along the air flow direction, Provide cooling capacity for the fourth refrigeration cold box 17, the third refrigeration cold box 16, the second refrigeration cold box 15 and the first refrigeration cold box 14; this embodiment also uses an ejector booster 43 to process the unliquefied hydrogen and the regasified hydrogen (collectively referred to as boil-off gas). The ejector booster 43 adopts a first-stage ejector. In coordination, the pressure regulating unit 1 is used to regulate the pressure of the raw hydrogen to make the raw hydrogen pressure 2.4 MPa (A). The raw hydrogen throttling member 28 on the third refrigeration pipeline 21 is used to regulate the pressure of the raw hydrogen again. The raw hydrogen The gas pressure drops to 0.7 MPa(A). The ejector booster 43 draws a portion of the high-pressure raw hydrogen from the second refrigeration line 20 as a power source, while the unliquefied hydrogen and regasified hydrogen (collectively referred to as boil-off gas) serve as the ejected gas. Energy is exchanged within the ejector booster 43. After their pressure increases, the unliquefied hydrogen and regasified hydrogen (collectively referred to as boil-off gas) merge with the raw hydrogen leaving the raw hydrogen throttle 28 on the third refrigeration line 21 and enter the fourth refrigeration cold box 17 to continue participating in the liquid hydrogen production process.

[0103] The present invention uses hydrogen as a circulating refrigeration refrigerant, which greatly reduces production and operating costs. The unliquefied hydrogen and regasified hydrogen (collectively referred to as boil-off gas) generated during the separation and storage process are processed by an ejector booster 43, so that the overall liquefaction rate of the raw hydrogen reaches 100%. At the same time, the unliquefied hydrogen and regasified hydrogen (collectively referred to as boil-off gas) are hermetically recovered, reducing safety risks. The ejector booster 43 has a simple structure, low cost, and easy operation and maintenance, which reduces initial investment and operating costs. In the present invention, the first low-pressure circulating hydrogen and the second low-pressure circulating hydrogen are combined and enter the circulating hydrogen compressor 39 in a low-temperature state, which greatly reduces the power consumption of the circulating hydrogen compressor 39 and the energy consumption of liquid hydrogen production. The liquid hydrogen production method proposed in the present invention has low energy consumption and a high overall liquefaction rate, which is conducive to the promotion of liquid hydrogen production technology.

[0104] 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 liquid hydrogen production system for processing boil-off gas, characterized in that: The system includes: A pressure regulating unit, a pre-cooling unit and a refrigeration unit are sequentially arranged along the airflow direction, and a raw hydrogen inlet is provided at the input end of the pressure regulating unit; a separation unit connected to an output end of the refrigeration unit and configured to separate liquid hydrogen from hydrogen gas; a storage unit, connected to the separation unit and configured to store liquid hydrogen; a boil-off gas pressurization processing unit, wherein the input end of the boil-off gas pressurization processing unit is connected to the separation unit and the storage unit, and the output end of the boil-off gas pressurization processing unit is connected to the flow pipeline of the refrigeration unit, and is used to pressurize the regasified hydrogen in the storage unit and the non-liquefied hydrogen in the separation unit and return them to the refrigeration unit; The refrigeration unit comprises: A refrigeration component connected between the pre-cooling unit and the separation unit; A circulating pressure-reducing low-temperature component, which is connected to the refrigeration component and is used for pressure reduction and refrigeration of high-pressure circulating hydrogen; A low-temperature compression assembly, connected to the circulating pressure-reducing low-temperature assembly, for compressing low-pressure circulating hydrogen into high-pressure circulating hydrogen and performing a temperature reduction process; The boil-off gas pressurization processing unit includes an ejector supercharger, which includes an ejector hydrogen inlet, a high-pressure hydrogen inlet and a mixed hydrogen outlet. The ejector hydrogen inlet is connected to the gas phase outlet of the separation unit and the regasified hydrogen outlet of the storage unit, the high-pressure hydrogen inlet is connected to the high-pressure position of the hydrogen pipeline of the refrigeration component, and the mixed hydrogen outlet is connected to the low-pressure position of the hydrogen pipeline of the refrigeration component.

2. The liquid hydrogen production system for processing boil-off gas according to claim 1, characterized in that: The pressure regulating unit includes a hydrogen compressor and a pressure regulating pipeline. The output end of the pressure regulating pipeline is connected to the pre-cooling unit, and the hydrogen compressor is arranged on the pressure regulating pipeline.

3. The liquid hydrogen production system for processing boil-off gas according to claim 1, characterized in that: The pre-cooling unit includes a first pre-cooling cold box, a second pre-cooling cold box and a connecting pipeline, the two ends of the connecting pipeline are respectively connected to the pressure regulating unit and the refrigeration unit, the first pre-cooling cold box and the second pre-cooling cold box are sequentially connected to the connecting pipeline along the air flow direction, and the first pre-cooling cold box and the second pre-cooling cold box are respectively used to load the first pre-cooling refrigerant and the second pre-cooling refrigerant.

4. The liquid hydrogen production system for processing boil-off gas according to claim 1, characterized in that: The refrigeration assembly includes a plurality of refrigeration cold boxes, which are arranged in sequence along the airflow direction, and the refrigeration cold boxes are connected to refrigeration pipelines; The input end of the refrigeration pipeline at the head end is connected to the pre-cooling unit, the output end of the refrigeration pipeline at the tail end is connected to the separation unit, and adjacent refrigeration pipelines are connected; A recooling pipeline is provided between some adjacent refrigeration pipelines, the output end of the front refrigeration pipeline of the adjacent refrigeration pipeline is connected to the input end of the matched recooling pipeline, the input end of the rear refrigeration pipeline of the adjacent refrigeration pipeline is connected to the output end of the matched recooling pipeline, and the recooling pipeline between the adjacent refrigeration pipelines is connected to the refrigeration cold box connected to the rear refrigeration pipeline; The recooling pipeline is connected to a para-hydrogen converter, and the refrigeration pipeline at the head end and close to the precooling unit is also provided with a para-hydrogen converter; Some of the refrigeration pipelines are connected with raw hydrogen throttling parts.

5. The liquid hydrogen production system for processing boil-off gas according to claim 4, characterized in that: The circulating pressure-reducing low-temperature component includes a high-pressure circulating hydrogen pipeline, a first low-pressure circulating hydrogen pipeline, a second low-pressure circulating hydrogen pipeline, a circulating hydrogen separator and a circulating hydrogen throttling device. The high-pressure circulating hydrogen pipeline, the first low-pressure circulating hydrogen pipeline and the second low-pressure circulating hydrogen pipeline are all connected to the remaining refrigeration cold boxes except the terminal refrigeration cold box. The input end of the high-pressure circulating hydrogen pipeline is connected to the output end of the low-temperature compression assembly, the output end of the high-pressure circulating hydrogen pipeline is connected to the inlet of the circulating hydrogen separator, the liquid phase outlet and the gas phase outlet of the circulating hydrogen separator are both connected to the input end of the second low-pressure circulating hydrogen pipeline, the pipeline between the liquid phase outlet of the circulating hydrogen separator and the input end of the second low-pressure circulating hydrogen pipeline passes through the terminal refrigeration cold box, and the circulating hydrogen throttling device is arranged on the high-pressure circulating hydrogen pipeline and close to the circulating hydrogen separator. One end of a plurality of branch pipelines is connected to the high-pressure circulating hydrogen pipeline, the other ends of the plurality of branch pipelines are connected to the first low-pressure circulating hydrogen pipeline, and a circulating hydrogen expander is provided on each of the plurality of branch pipelines.

6. The liquid hydrogen production system for processing boil-off gas according to claim 1, characterized in that: The low-temperature compression component includes a circulating hydrogen compressor, high- and low-pressure circulating hydrogen pre-cooling pipelines and a circulating hydrogen pre-cooling box. The input end and the output end of the high- and low-pressure circulating hydrogen pre-cooling pipelines are respectively connected to the input end and the output end of the circulating pressure-reducing low-temperature component. The circulating hydrogen compressor and the circulating hydrogen pre-cooling box are sequentially arranged on the high- and low-pressure circulating hydrogen pre-cooling pipelines along the air flow direction. The circulating hydrogen pre-cooling box is used to load refrigerant.

7. A method for producing liquid hydrogen by treating boil-off gas, using the system for producing liquid hydrogen by treating boil-off gas according to any one of claims 1 to 6, characterized in that: The method includes: Step 1: Inputting the raw hydrogen into the pressure regulating unit for pressurization to obtain high-pressure raw hydrogen; Step 2: Input the high-pressure raw hydrogen into the pre-cooling unit to absorb cold energy and perform pre-cooling; Step 3: The pre-cooled high-pressure raw hydrogen gas is fed into a refrigeration unit for refrigeration, cooling, and decompression to produce liquid hydrogen and unliquefied hydrogen gas; Step 4: Input the liquid hydrogen and the unliquefied hydrogen into a separation unit for separation, and store the liquid hydrogen; Step 5: The separated unliquefied hydrogen and the regasified hydrogen of the liquid hydrogen are input into the boil-off gas pressurization processing unit, and after pressurization, they are returned to the refrigeration unit, and steps 3 to 5 are repeated to continue participating in the liquid hydrogen preparation process.

8. The method for producing liquid hydrogen by treating boil-off gas according to claim 7, wherein: The first low-pressure circulating hydrogen and the second low-pressure circulating hydrogen merge and enter the circulating hydrogen compressor at a low temperature to generate high-pressure circulating hydrogen; The high-pressure circulating hydrogen is input into the circulating hydrogen pre-cooling box to absorb the cold energy and reduce the temperature; The cooled high-pressure circulating hydrogen passes through the refrigeration component and then enters the circulating hydrogen throttling component and the circulating hydrogen separation component in sequence to produce circulating liquid hydrogen; When the circulating liquid hydrogen passes through the refrigeration component in reverse, it absorbs heat and then flows into the first low-pressure circulating hydrogen; The second low-pressure circulating hydrogen led from the high-pressure circulating hydrogen pipeline merges with the first low-pressure circulating hydrogen.

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