BOG recycling system and method for liquid hydrogen refueling station

Abstract

The invention discloses a BOG recycling system for a liquid hydrogen refueling station, and relates to the technical field of liquid hydrogen refueling. Comprising a liquid hydrogen storage tank, a liquid hydrogen pump, a liquid hydrogen tank car, a liquid nitrogen tank, a gas-liquid separator, a condenser, a metal hydride hydrogen storage tank, a water tank, an inlet buffer tank, a hydrogen compressor, an outlet buffer tank, a hydrogenation machine, a hydrogen storage bottle set, a BOG pressurization pipeline, a liquid hydrogen filling pipeline, a circulation pipeline and a hydrogen recovery pipeline. According to the system, low-temperature hydrogen stored in the liquid hydrogen storage tank is used for liquefying nitrogen generated by pre-cooling to achieve circulation of liquid nitrogen, the metal hydride hydrogen storage tank is used for separating the nitrogen and the hydrogen generated by pre-cooling, meanwhile, the hydrogen releasing cold energy and the hydrogen generated by pre-cooling are conveyed to the hydrogen compressor, the hydrogen compressor is used for pressurizing, and the hydrogen is stored in the liquid hydrogen storage tank. The BOG enters a gas storage cylinder group to be stored or hydrogenated for a hydrogen energy automobile, so that the utilization efficiency of the hydrogen is improved, zero emission of the BOG is realized, and energy is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid hydrogen refueling, and in particular to a BOG recovery and utilization system and method for a liquid hydrogen refueling station. Background Art

[0002] According to the storage status of hydrogen in the station, hydrogen refueling stations can be divided into two categories: gas hydrogen refueling stations and liquid hydrogen refueling stations. Among them, liquid hydrogen refueling stations have obvious advantages over gas hydrogen refueling stations in terms of energy density, floor space, transportation efficiency, safety risks, etc., and are regarded as the mainstream development direction of hydrogen refueling stations in my country in the future.

[0003] Due to the low temperature characteristics of liquid hydrogen, a certain amount of evaporated hydrogen (BOG) will inevitably be produced in the operation of the liquid hydrogen refueling station. The main sources of BOG are two aspects: First, since the temperature of liquid hydrogen is much lower than the ambient temperature, external heat will be transmitted into the container through the container wall during storage, causing the liquid hydrogen to vaporize and produce BOG, which will increase the pressure inside the container. BOG needs to be discharged to avoid excessive pressure on the liquid hydrogen storage tank; second, the loss of equipment such as liquid hydrogen tank trucks and liquid hydrogen pipelines during precooling and filling. If BOG is discharged into the atmosphere through a centralized emission system, it will not only pose certain safety hazards and cause pollution to the atmospheric environment, but also consume a large amount of precious hydrogen resources, seriously reducing the economic efficiency of the liquid hydrogen refueling station; and if BOG is recovered and liquefied, multiple cooling steps are required to reduce its temperature to 20K. In this process, sufficient cold energy needs to be provided, and the energy consumption is not economical. For this reason, a BOG recovery and utilization system and method for liquid hydrogen refueling stations are proposed. Summary of the invention

[0004] The purpose of the present invention is to solve the problems in the prior art and to propose a BOG recovery and utilization system and method for a liquid hydrogen refueling station.

[0005] A BOG recycling system for a liquid hydrogen refueling station, comprising a liquid hydrogen storage tank, a liquid hydrogen pump, a liquid hydrogen tank truck, a liquid nitrogen tank, a gas-liquid separator, a condenser, a metal hydride hydrogen storage tank, a water tank, an inlet buffer tank, a hydrogen compressor, an outlet buffer tank, a hydrogenator, a hydrogen storage bottle group, a BOG booster pipeline, a liquid hydrogen filling pipeline, a circulation pipeline and a hydrogen recovery pipeline;

[0006] The BOG booster pipeline is sequentially connected to a liquid hydrogen storage tank, a first stop valve, a condenser, an inlet buffer tank, a hydrogen compressor and an outlet buffer tank, and the outlet of the outlet buffer tank is connected to a hydrogenator and a hydrogen storage bottle group through a second stop valve and a third stop valve respectively;

[0007] The liquid hydrogen filling pipeline is sequentially connected to a liquid hydrogen storage tank, a first liquid hydrogen stop valve, a liquid hydrogen pump, a second liquid hydrogen stop valve and a liquid hydrogen tank truck;

[0008] The circulation pipeline is connected to the liquid hydrogen tank truck, the fourth stop valve, the fifth stop valve, the metal hydride hydrogen storage tank, the condenser, the gas-liquid separator, and the liquid nitrogen tank in sequence, and is connected to the liquid hydrogen filling pipeline through the sixth stop valve. The connection between the circulation pipeline and the liquid hydrogen filling pipeline is located between the first liquid hydrogen stop valve and the liquid hydrogen pump;

[0009] The circulation pipeline and the hydrogen recovery pipeline are connected through a metal hydride hydrogen storage tank, the hydrogen recovery pipeline is connected to the BOG booster pipeline, and the connection point is located between the condenser and the inlet buffer tank;

[0010] The pipeline on the circulation pipeline and located at the inlet of the fifth stop valve is connected to a hydrogen collection pipeline and a BOG boosting pipeline. A seventh stop valve is provided on the hydrogen collection pipeline. The connection between the hydrogen collection pipeline and the BOG boosting pipeline is located between the first stop valve and the condenser.

[0011] Preferably, the gas phase outlet of the gas-liquid separator is connected to a reflux pipeline, and the reflux pipeline is connected to the inlet of the condenser on the circulation pipeline through a ninth stop valve.

[0012] Preferably, the inlet of the metal hydride hydrogen storage tank is connected to the circulation pipeline, and the outlet of the metal hydride hydrogen storage tank is divided into two branches, one branch is connected to the hydrogen recovery pipeline through the eighth stop valve, and the other branch is connected to the condenser inlet.

[0013] Preferably, the water tank is connected to the metal hydride hydrogen storage tank through an eleventh stop valve, the outlet pipeline of the metal hydride hydrogen storage tank and the inlet pipeline of the fifth stop valve are connected with a jump pipeline, and the jump pipeline is provided with a tenth stop valve.

[0014] Preferably, the liquid hydrogen storage tank, liquid nitrogen tank, metal hydride hydrogen storage tank, water tank, hydrogen storage bottle group, liquid hydrogen filling pipeline and circulation pipeline are all provided with insulation materials on the outside.

[0015] Preferably, the condenser adopts a low-temperature plate-fin heat exchanger.

[0016] Preferably, the hydrogen compressor is a diaphragm compressor, and the liquid hydrogen pump is a liquid hydrogen centrifugal pump.

[0017] Preferably, the hydrogen storage bottle group is provided with multiple groups, which are respectively used to store hydrogen with high pressure of 70MPa, medium pressure of 35MPa, and low pressure of 25MPa.

[0018] A method for recycling BOG at a liquid hydrogen refueling station, based on the above recycling system, comprises the following steps:

[0019] S1, startup phase: open the first stop valve, open the second stop valve and the third stop valve respectively, start the hydrogen compressor, the low-temperature hydrogen from the liquid hydrogen storage tank enters the BOG booster pipeline, releases cold in the condenser, and then enters the hydrogen compressor for boosting through the inlet buffer tank. After boosting, part of the high-pressure hydrogen is sent to the hydrogenator through the second stop valve for hydrogenation of hydrogen-powered vehicles, and the other part is sent to the hydrogen storage bottle group for storage through the third stop valve;

[0020] S2, liquid nitrogen precooling stage: open the sixth stop valve, the second liquid hydrogen stop valve, the fourth stop valve, the tenth stop valve, and the ninth stop valve, start the gas-liquid separator, and the liquid nitrogen in the liquid nitrogen tank enters the liquid hydrogen filling pipeline through the sixth stop valve, and precools the liquid hydrogen pump and the liquid hydrogen tank truck to convert the liquid nitrogen into nitrogen gas;

[0021] The nitrogen enters the condenser through the fourth stop valve and the tenth stop valve in turn to absorb cold energy and be converted into liquid nitrogen, and then enters the gas-liquid separator. Under the action of the gas-liquid separator, the unliquefied nitrogen returns to the condenser through the reflux pipeline to absorb cold energy, and the liquid nitrogen enters the liquid nitrogen tank. This process is repeated until the temperature of the liquid hydrogen pump and the liquid hydrogen tank truck drops to the temperature of liquid nitrogen. At this time, the initial pre-cooling stage is completed, and the sixth stop valve and the tenth stop valve are closed;

[0022] S3, liquid hydrogen precooling stage: open the first liquid hydrogen stop valve, the fifth stop valve, and the eleventh stop valve, start the liquid hydrogen pump, and the liquid hydrogen in the liquid hydrogen storage tank enters the liquid hydrogen tank truck through the liquid hydrogen filling pipeline, and is precooled to convert the liquid hydrogen into hydrogen gas;

[0023] The mixed gas generated by precooling enters the metal hydride hydrogen storage tank through the fourth stop valve and the fifth stop valve in sequence. The water tank delivers cold water to the metal hydride hydrogen storage tank through the eleventh stop valve to absorb the heat released when the metal hydride hydrogen storage tank stores hydrogen, and then returns to the water tank. The hydrogen in the mixed gas is absorbed by the metal hydride hydrogen storage tank, and the nitrogen enters the condenser through the circulation pipeline to absorb cold energy, and then enters the gas-liquid separator. The unliquefied nitrogen returns to the condenser through the reflux pipeline to absorb cold energy, and the liquid nitrogen enters the liquid nitrogen tank for storage;

[0024] Continue the above process until the gas purity and temperature in the liquid hydrogen tank truck meet the requirements, then stop the gas-liquid separator and the liquid hydrogen pump, close the fifth stop valve and the ninth stop valve, open the eighth stop valve, and the water that has absorbed heat enters the metal hydride hydrogen storage tank through the eleventh stop valve to meet the heat absorption requirements when the metal hydride hydrogen storage tank releases hydrogen. The hydrogen enters the BOG booster pipeline through the hydrogen recovery pipeline. After the boosting, a part of the high-pressure hydrogen is sent to the hydrogenator through the second stop valve to hydrogenate the hydrogen-powered vehicle, and the other part is sent to the hydrogen storage bottle group for storage through the third stop valve. Continue the above process until there is no hydrogen stored in the metal hydride hydrogen storage tank, and close the eighth stop valve and the eleventh stop valve;

[0025] S4, liquid hydrogen filling stage: open the seventh stop valve, start the liquid hydrogen pump, the liquid hydrogen in the liquid hydrogen storage tank enters the liquid hydrogen tank truck through the liquid hydrogen filling pipeline, the hydrogen generated by the filling enters the BOG booster pipeline through the fourth stop valve and the seventh stop valve, and then goes to the condenser to release the cold and then pressurize and store. When the liquid hydrogen inside the liquid hydrogen tank truck reaches the set liquid level, the filling is completed, and then the liquid hydrogen pump is stopped, and the first liquid hydrogen stop valve, the second liquid hydrogen stop valve, the fourth stop valve, the seventh stop valve, the second stop valve, and the third stop valve are closed.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] The system of the present invention utilizes low-temperature hydrogen stored in a liquid hydrogen storage tank to liquefy nitrogen generated by precooling, thereby realizing the circulation of liquid nitrogen. The system also utilizes a metal hydride hydrogen storage tank to separate nitrogen and hydrogen generated by precooling. Meanwhile, the hydrogen after the cold is released and the hydrogen generated by precooling are transported to a hydrogen compressor, pressurized by the hydrogen compressor, and then enter a gas storage cylinder group for storage or hydrogenation for hydrogen-powered vehicles, thereby improving the utilization efficiency of hydrogen, realizing zero BOG emission, and saving energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the BOG recovery and utilization system of the liquid hydrogen refueling station in the present invention.

[0029] In the figure: 1 liquid hydrogen storage tank, 2 liquid hydrogen pump, 3 liquid hydrogen tank truck, 4 liquid nitrogen tank, 5 gas-liquid separator, 6 condenser, 7 metal hydride hydrogen storage tank, 8 water tank, 9 inlet buffer tank, 10 hydrogen compressor, 11 outlet buffer tank, 12 hydrogenator, 13 hydrogen storage bottle group, 14 first stop valve, 15 first liquid hydrogen stop valve, 16 second liquid hydrogen stop valve, 17 fourth stop valve, 18 fifth stop valve, 19 tenth stop valve, 20 ninth stop valve, 21 sixth stop valve, 22 seventh stop valve, 23 eighth stop valve, 24 eleventh stop valve, 25 second stop valve, 26 third stop valve, 27 BOG booster pipeline, 28 liquid hydrogen filling pipeline, 29 circulation pipeline, 30 hydrogen recovery pipeline, 31 reflux pipeline. DETAILED DESCRIPTION

[0030] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0031] Reference Figure 1As shown, a BOG recycling system for a liquid hydrogen refueling station includes a liquid hydrogen storage tank 1, a liquid hydrogen pump 2, a liquid hydrogen tank truck 3, a liquid nitrogen tank 4, a gas-liquid separator 5, a condenser 6, a metal hydride hydrogen storage tank 7, a water tank 8, an inlet buffer tank 9, a hydrogen compressor 10, an outlet buffer tank 11, a hydrogenator 12, a hydrogen storage bottle group 13, a BOG booster pipeline 27, a liquid hydrogen filling pipeline 28, a circulation pipeline 29 and a hydrogen recovery pipeline 30;

[0032] The BOG boosting pipeline 27 is sequentially connected to the liquid hydrogen storage tank 1, the first stop valve 14, the condenser 6, the inlet buffer tank 9, the hydrogen compressor 10 and the outlet buffer tank 11. The BOG boosting pipeline 27 is used to release the coldness of the low-temperature hydrogen in the liquid hydrogen storage tank 1 in the condenser 6 and then enter the hydrogen compressor 10 for pressurization. The outlet of the outlet buffer tank 11 is connected to the hydrogenator 12 and the hydrogen storage bottle group 13 through the second stop valve 25 and the third stop valve 26 respectively. The BOG boosting pipeline 27 is used for the low-temperature hydrogen in the liquid hydrogen storage tank 1 to enter the hydrogen compressor 10 for pressurization after releasing the coldness in the condenser 6, and then send it to the hydrogen storage bottle group 13 or the hydrogenator 12 after pressurization;

[0033] The liquid hydrogen filling pipeline 28 is connected to the liquid hydrogen storage tank 1, the first liquid hydrogen stop valve 15, the liquid hydrogen pump 2, the second liquid hydrogen stop valve 16 and the liquid hydrogen tank truck 3 in sequence, and the liquid hydrogen filling pipeline 28 is used to transport liquid hydrogen from the liquid hydrogen storage tank 1 to the liquid hydrogen tank truck 3;

[0034] The circulation pipeline 29 is connected to the liquid hydrogen tank truck 3, the fourth stop valve 17, the fifth stop valve 18, the metal hydride hydrogen storage tank 7, the condenser 6, the gas-liquid separator 5, and the liquid nitrogen tank 4 in sequence, and is connected to the liquid hydrogen filling pipeline 28 through the sixth stop valve 21 to realize the circulation liquefaction of nitrogen. The connection point between the circulation pipeline 29 and the liquid hydrogen filling pipeline 28 is located between the first liquid hydrogen stop valve 15 and the liquid hydrogen pump 2;

[0035] The circulation pipeline 29 and the hydrogen recovery pipeline 30 are connected through the metal hydride hydrogen storage tank 7, and the hydrogen recovery pipeline 30 is connected to the BOG boosting pipeline 27, and the connection is located between the condenser 6 and the inlet buffer tank 9, so that the hydrogen enters the BOG boosting pipeline 27 through the hydrogen recovery pipeline 30 for boosting, and is sent to the hydrogen storage bottle group 13 or the hydrogenator 12 after boosting;

[0036] The pipeline on the circulation pipeline 29 and located at the inlet of the fifth stop valve 18 is connected to a hydrogen collection pipeline and a BOG boosting pipeline 27 , and a seventh stop valve 22 is provided on the hydrogen collection pipeline. The connection between the hydrogen collection pipeline and the BOG boosting pipeline 27 is located between the first stop valve 14 and the condenser 6 .

[0037] In this embodiment, the gas phase outlet of the gas-liquid separator 5 is connected to a reflux pipeline 31, and the reflux pipeline is connected to the inlet of the condenser 6 on the circulation pipeline 29 through the ninth stop valve 20 to achieve secondary circulation of the unliquefied nitrogen.

[0038] In this embodiment, the inlet of the metal hydride hydrogen storage tank 7 is connected to the circulation pipeline 29, and the outlet of the metal hydride hydrogen storage tank 7 is divided into two branches, one branch is connected to the hydrogen recovery pipeline 30 through the eighth stop valve 23 to recover the hydrogen generated by precooling, and the other branch is connected to the inlet of the condenser 6 to deliquefy the nitrogen, and the nitrogen and hydrogen are separated from the two branches.

[0039] In this embodiment, the water tank 8 is connected to the metal hydride hydrogen storage tank 7 through the eleventh stop valve 24. When the metal hydride hydrogen storage tank 7 absorbs hydrogen, the water tank 8 passes cold water into the metal hydride hydrogen storage tank 7 through the eleventh stop valve 24 to absorb heat; when releasing hydrogen, water that has absorbed heat is passed in to meet the heat absorption requirement of the metal hydride hydrogen storage tank 7. The outlet pipeline of the metal hydride hydrogen storage tank 7 and the inlet pipeline of the fifth stop valve 18 are connected with a jump pipeline, and the tenth stop valve 19 is provided on the jump pipeline.

[0040] In this embodiment, liquid hydrogen is an extremely low-temperature liquid, and its thermal insulation management during storage and transportation is very important. In order to maintain the low temperature state of liquid hydrogen during transportation and reduce heat loss, the liquid hydrogen storage tank 1, liquid nitrogen tank 4, metal hydride hydrogen storage tank 7, water tank 8, hydrogen storage bottle group 13, liquid hydrogen filling pipeline 28 and circulation pipeline 29 are all provided with insulation materials on the outside to effectively prevent heat loss.

[0041] In this embodiment, the condenser 6 adopts a low-temperature plate-fin heat exchanger. The low-temperature plate-fin heat exchanger is small in size and light in weight. Its compact structure makes the heat exchange surface area large, which can effectively improve the heat exchange efficiency.

[0042] In this embodiment, the hydrogen compressor 10 is a diaphragm compressor, which can achieve a high compression ratio and has good sealing performance, and is suitable for applications with high gas purity requirements. The liquid hydrogen pump 2 is a liquid hydrogen centrifugal pump.

[0043] In this embodiment, the hydrogen storage bottle group 13 is provided with multiple groups, which are respectively used to store hydrogen with a high pressure of 70MPa, a medium pressure of 35MPa, and a low pressure of 25MPa.

[0044] The present invention also proposes a BOG recycling method for a liquid hydrogen refueling station, based on the above recycling system, comprising the following steps:

[0045] S1, startup phase: open the first stop valve 14, open the second stop valve 25 and the third stop valve 26 respectively, start the hydrogen compressor 10, the low-temperature hydrogen from the liquid hydrogen storage tank 1 enters the BOG booster pipeline 27, releases cold in the condenser 6, and then enters the hydrogen compressor 10 for boosting through the inlet buffer tank 9. After boosting, a part of the high-pressure hydrogen is sent to the hydrogenator 12 through the second stop valve 25 for hydrogenation of the hydrogen energy vehicle, and the other part is sent to the hydrogen storage bottle group 13 for storage through the third stop valve 26;

[0046] S2, liquid nitrogen precooling stage: open the sixth stop valve 21, the second liquid hydrogen stop valve 16, the fourth stop valve 17, the tenth stop valve 19, and the ninth stop valve 20, start the gas-liquid separator 5, and the liquid nitrogen in the liquid nitrogen tank 4 enters the liquid hydrogen filling pipeline 28 through the sixth stop valve 21, and preliminarily precools the liquid hydrogen pump 2 and the liquid hydrogen tank truck 3, so that the liquid nitrogen is converted into nitrogen gas;

[0047] The nitrogen enters the condenser through the fourth stop valve 17 and the tenth stop valve 19 in sequence to absorb cold energy and be converted into liquid nitrogen, and then enters the gas-liquid separator 5. Under the action of the gas-liquid separator 5, the unliquefied nitrogen returns to the condenser 6 through the reflux pipeline 31 to absorb cold energy, and the liquid nitrogen enters the liquid nitrogen tank 4. This process is repeated until the temperature of the liquid hydrogen pump 2 and the liquid hydrogen tank truck 3 drops to the temperature of liquid nitrogen. At this time, the preliminary precooling stage is completed, and the sixth stop valve 21 and the tenth stop valve 19 are closed;

[0048] S3, liquid hydrogen precooling stage: open the first liquid hydrogen stop valve 15, the fifth stop valve 18, and the eleventh stop valve 24, start the liquid hydrogen pump 2, and the liquid hydrogen in the liquid hydrogen storage tank 1 enters the liquid hydrogen tank truck 3 through the liquid hydrogen filling pipeline 28, and is precooled to convert the liquid hydrogen into hydrogen gas;

[0049] The mixed gas generated by precooling enters the metal hydride hydrogen storage tank 7 through the fourth stop valve 17 and the fifth stop valve 18 in sequence, and the water tank 8 delivers cold water to the metal hydride hydrogen storage tank 7 through the eleventh stop valve 24 to absorb the heat released when the metal hydride hydrogen storage tank 7 stores hydrogen, and then returns to the water tank. The hydrogen in the mixed gas is absorbed by the metal hydride hydrogen storage tank 7, and the nitrogen enters the condenser 6 through the circulation pipeline 29 to absorb cold energy, and then enters the gas-liquid separator 5. The unliquefied nitrogen returns to the condenser 6 through the reflux pipeline 31 to absorb cold energy, and the liquid nitrogen enters the liquid nitrogen tank 4 for storage;

[0050] Continue the above process until the gas purity and temperature in the liquid hydrogen tank truck 3 meet the requirements, then stop the gas-liquid separator 5 and the liquid hydrogen pump 2, close the fifth stop valve 18 and the ninth stop valve 20, open the eighth stop valve 23, and the water after absorbing heat enters the metal hydride hydrogen storage tank 7 through the eleventh stop valve 24, meeting the heat absorption requirement when the metal hydride hydrogen storage tank 7 releases hydrogen. The hydrogen enters the BOG booster pipeline 27 through the hydrogen recovery pipeline 30. After the boosting, a part of the high-pressure hydrogen is sent to the hydrogenator 12 through the second stop valve 25 to hydrogenate the hydrogen energy vehicle, and the other part is sent to the hydrogen storage bottle group 13 for storage through the third stop valve 26. Continue the above process until there is no hydrogen stored in the metal hydride hydrogen storage tank 7, and close the eighth stop valve 23 and the eleventh stop valve 24;

[0051] S4, liquid hydrogen filling stage: open the seventh stop valve 22, start the liquid hydrogen pump 2, the liquid hydrogen in the liquid hydrogen storage tank 1 enters the liquid hydrogen tank car 3 through the liquid hydrogen filling pipeline 28, the hydrogen generated by the filling enters the BOG booster pipeline through the fourth stop valve 17 and the seventh stop valve 22, and then goes to the condenser 6 to release the cold and then pressurize and store. When the liquid hydrogen inside the liquid hydrogen tank car 3 reaches the set liquid level, the filling is completed, and then the liquid hydrogen pump 2 is stopped, and the first liquid hydrogen stop valve 15, the second liquid hydrogen stop valve 16, the fourth stop valve 17, the seventh stop valve 22, the second stop valve 25, and the third stop valve 26 are closed.

[0052] In summary, the BOG recycling system provided by the present invention utilizes low-temperature BOG to liquefy the nitrogen generated during the precooling process to realize the circulation of nitrogen; and utilizes the metal hydride hydrogen storage tank 7 to separate the nitrogen and hydrogen generated during the precooling process, and at the same time, transports the hydrogen to the hydrogen compressor 10, pressurizes the hydrogen compressor 10, enters the gas storage cylinder group 13 for storage or hydrogenation for hydrogen-powered vehicles, thereby improving the utilization efficiency of hydrogen.

[0053] It is known from common technical knowledge that the present invention can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are included in the present invention.

Claims

1. A BOG recovery and utilization system for a liquid hydrogen refueling station, characterized in that: It comprises a liquid hydrogen storage tank (1), a liquid hydrogen pump (2), a liquid hydrogen tank truck (3), a liquid nitrogen tank (4), a gas-liquid separator (5), a condenser (6), a metal hydride hydrogen storage tank (7), a water tank (8), an inlet buffer tank (9), a hydrogen compressor (10), an outlet buffer tank (11), a hydrogenator (12), a hydrogen storage bottle group (13), a BOG booster pipeline (27), a liquid hydrogen filling pipeline (28), a circulation pipeline (29) and a hydrogen recovery pipeline (30); The BOG boosting pipeline (27) is sequentially connected to a liquid hydrogen storage tank (1), a first stop valve (14), a condenser (6), an inlet buffer tank (9), a hydrogen compressor (10) and an outlet buffer tank (11); the outlet of the outlet buffer tank (11) is connected to a hydrogenator (12) and a hydrogen storage bottle group (13) via a second stop valve (25) and a third stop valve (26), respectively; The liquid hydrogen filling pipeline (28) is sequentially connected to a liquid hydrogen storage tank (1), a first liquid hydrogen stop valve (15), a liquid hydrogen pump (2), a second liquid hydrogen stop valve (16) and a liquid hydrogen tank truck (3); The circulation pipeline (29) is connected to the liquid hydrogen tank truck (3), the fourth stop valve (17), the fifth stop valve (18), the metal hydride hydrogen storage tank (7), the condenser (6), the gas-liquid separator (5), and the liquid nitrogen tank (4) in sequence, and is connected to the liquid hydrogen filling pipeline (28) through the sixth stop valve (21); the connection point between the circulation pipeline (29) and the liquid hydrogen filling pipeline (28) is located between the first liquid hydrogen stop valve (15) and the liquid hydrogen pump (2); The circulation pipeline (29) and the hydrogen recovery pipeline (30) are connected via a metal hydride hydrogen storage tank (7); the hydrogen recovery pipeline (30) is connected to the BOG boosting pipeline (27), and the connection point is located between the condenser (6) and the inlet buffer tank (9); A pipeline on the circulation pipeline (29) and located at the inlet of the fifth stop valve (18) is connected to a hydrogen collection pipeline and a BOG boosting pipeline (27), a seventh stop valve (22) is provided on the hydrogen collection pipeline, and a connection point between the hydrogen collection pipeline and the BOG boosting pipeline (27) is located between the first stop valve (14) and the condenser (6).

2. A BOG recovery and utilization system for a liquid hydrogen refueling station according to claim 1, characterized in that: The gas phase outlet of the gas-liquid separator (5) is connected to a reflux pipeline (31), and the reflux pipeline is connected to the inlet of the condenser (6) on the circulation pipeline (29) through a ninth stop valve (20).

3. A BOG recovery and utilization system for a liquid hydrogen refueling station according to claim 1, characterized in that: The inlet of the metal hydride hydrogen storage tank (7) is connected to the circulation pipeline (29), and the outlet of the metal hydride hydrogen storage tank (7) is divided into two branches, one branch is connected to the hydrogen recovery pipeline (30) through the eighth stop valve (23), and the other branch is connected to the inlet of the condenser (6).

4. A BOG recovery and utilization system for a liquid hydrogen refueling station according to claim 1, characterized in that: The water tank (8) is connected to the metal hydride hydrogen storage tank (7) via an eleventh stop valve (24); the outlet pipeline of the metal hydride hydrogen storage tank (7) and the inlet pipeline of the fifth stop valve (18) are connected to a jump pipeline, and the jump pipeline is provided with a tenth stop valve (19).

5. The BOG recycling system for a liquid hydrogen refueling station according to claim 1, characterized in that: The liquid hydrogen storage tank (1), the liquid nitrogen tank (4), the metal hydride hydrogen storage tank (7), the water tank (8), the hydrogen storage bottle group (13), the liquid hydrogen filling pipeline (28) and the circulation pipeline (29) are all provided with insulation materials on the outside.

6. A BOG recovery and utilization system for a liquid hydrogen refueling station according to claim 1, characterized in that: The condenser (6) is a low-temperature plate-fin heat exchanger.

7. The BOG recovery and utilization system of a liquid hydrogen refueling station according to claim 1, characterized in that: The hydrogen compressor (10) is a diaphragm compressor, and the liquid hydrogen pump (2) is a liquid hydrogen centrifugal pump.

8. The BOG recovery and utilization system of a liquid hydrogen refueling station according to claim 1, characterized in that: The hydrogen storage bottle group (13) is provided with a plurality of groups, which are respectively used to store hydrogen with a high pressure of 70 MPa, a medium pressure of 35 MPa, and a low pressure of 25 MPa.

9. A method for recycling BOG in a liquid hydrogen refueling station, based on the recycling system according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, startup phase: open the first stop valve (14), open the second stop valve (25) and the third stop valve (26) respectively, start the hydrogen compressor (10), the low-temperature hydrogen from the liquid hydrogen storage tank (1) enters the BOG booster pipeline (27), releases cold energy in the condenser (6), and then enters the hydrogen compressor (10) through the inlet buffer tank (9) for boosting. After boosting, a part of the high-pressure hydrogen is sent to the hydrogenator (12) through the second stop valve (25) to hydrogenate the hydrogen-powered vehicle, and the other part is sent to the hydrogen storage bottle group (13) for storage through the third stop valve (26); S2, liquid nitrogen precooling stage: open the sixth stop valve (21), the second liquid hydrogen stop valve (16), the fourth stop valve (17), the tenth stop valve (19), and the ninth stop valve (20), start the gas-liquid separator (5), and the liquid nitrogen in the liquid nitrogen tank (4) enters the liquid hydrogen filling pipeline (28) through the sixth stop valve (21), and preliminarily precools the liquid hydrogen pump (2) and the liquid hydrogen tank truck (3), so that the liquid nitrogen is converted into nitrogen gas; The nitrogen passes through the fourth stop valve (17) and the tenth stop valve (19) in sequence and enters the condenser to absorb cold energy and is converted into liquid nitrogen, and then enters the gas-liquid separator (5). Under the action of the gas-liquid separator (5), the unliquefied nitrogen returns to the condenser (6) through the reflux pipeline (31) to absorb cold energy, and the liquid nitrogen enters the liquid nitrogen tank (4). This process is repeated until the temperature of the liquid hydrogen pump (2) and the liquid hydrogen tank truck (3) drops to the temperature of liquid nitrogen. At this time, the initial pre-cooling stage is completed, and the sixth stop valve (21) and the tenth stop valve (19) are closed; S3, liquid hydrogen precooling stage: the first liquid hydrogen stop valve (15), the fifth stop valve (18), and the eleventh stop valve (24) are opened, and the liquid hydrogen pump (2) is started. The liquid hydrogen in the liquid hydrogen storage tank (1) enters the liquid hydrogen tank truck (3) through the liquid hydrogen filling pipeline (28) and is precooled to convert the liquid hydrogen into hydrogen gas; The mixed gas generated by precooling enters the metal hydride hydrogen storage tank (7) through the fourth stop valve (17) and the fifth stop valve (18) in sequence. The water tank (8) delivers cold water to the metal hydride hydrogen storage tank (7) through the eleventh stop valve (24) to absorb the heat released when the metal hydride hydrogen storage tank (7) stores hydrogen. The mixed gas then returns to the water tank. The hydrogen in the mixed gas is absorbed by the metal hydride hydrogen storage tank (7). The nitrogen enters the condenser (6) through the circulation pipeline (29) to absorb cold energy. The mixed gas then enters the gas-liquid separator (5). The unliquefied nitrogen returns to the condenser (6) through the reflux pipeline (31) to absorb cold energy. The liquid nitrogen enters the liquid nitrogen tank (4) for storage. The above process is continued until the gas purity and temperature in the liquid hydrogen tank truck (3) meet the requirements, then the gas-liquid separator (5) and the liquid hydrogen pump (2) are stopped, the fifth stop valve (18) and the ninth stop valve (20) are closed, and the eighth stop valve (23) is opened. The water that has absorbed heat enters the metal hydride hydrogen storage tank (7) through the eleventh stop valve (24), meeting the heat absorption requirement when the metal hydride hydrogen storage tank (7) releases hydrogen. The hydrogen enters the BOG booster pipeline (27) through the hydrogen recovery pipeline (30). After the boosting, a part of the high-pressure hydrogen is sent to the hydrogenator (12) through the second stop valve (25) to hydrogenate the hydrogen-powered vehicle, and the other part is sent to the hydrogen storage bottle group (13) for storage through the third stop valve (26). The above process is continued until there is no hydrogen stored in the metal hydride hydrogen storage tank (7), and the eighth stop valve (23) and the eleventh stop valve (24) are closed; S4, liquid hydrogen filling stage: open the seventh stop valve (22), start the liquid hydrogen pump (2), the liquid hydrogen in the liquid hydrogen storage tank (1) enters the liquid hydrogen tank car (3) through the liquid hydrogen filling pipeline (28), the hydrogen generated by the filling enters the BOG booster pipeline through the fourth stop valve (17) and the seventh stop valve (22), and then goes to the condenser (6) to release the cold and then is pressurized and stored. When the liquid hydrogen inside the liquid hydrogen tank car (3) reaches the set liquid level, the filling is completed, and then the liquid hydrogen pump (2) is stopped, and the first liquid hydrogen stop valve (15), the second liquid hydrogen stop valve (16), the fourth stop valve (17), the seventh stop valve (22), the second stop valve (25), and the third stop valve (26) are closed.

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