BOG recycling system and method for liquid hydrogen refueling station

Abstract

Disclosed are a BOG recycling system and method for a liquid hydrogen refueling station. In the system, a self-evaporating steam cooling screen module comprises a liquid hydrogen storage tank for storing low-temperature liquid hydrogen, a first valve for controlling BOG release, a steam cooling screen using the liquid hydrogen storage tank, a liquid hydrogen pipeline steam cooling screen, a liquid hydrogen BOG recovery tank for storing BOG, and a second valve for providing a stable hydrogen source for a fuel cell. A hydrogen fuel cell of a fuel cell cogeneration module is connected behind the second valve, and a storage battery is charged through a DC chopper. A liquid hydrogen booster pump pressurizes liquid hydrogen and presses it into an air-temperature vaporizer, and the liquid hydrogen is vaporized and heated by atmospheric heat. A fuel cell waste heat thermostat uses waste heat of the hydrogen fuel cell to heat and adjust the temperature of the low-temperature hydrogen. The storage battery supplies energy to the electric heating thermostat to heat and adjust the temperature of the low-temperature hydrogen. The temperature-adjusted high-pressure hydrogen enters a cascade liquid hydrogen buffer tank, and is mixed with liquid hydrogen through a fifth valve in front of the hydrogenator and then enters the hydrogenator after temperature adjustment.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid hydrogen refueling stations, and in particular to a BOG recycling system and method of a liquid hydrogen refueling station. Background Art

[0002] 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 the storage process, causing the liquid hydrogen to vaporize and produce liquid hydrogen flash gas (BOG), which in turn causes the pressure inside the container to increase. BOG must be discharged to avoid excessive pressure in the liquid hydrogen storage tank.

[0003] Due to the limitations of current insulation technology and the special property of liquid hydrogen with extremely small latent heat of vaporization, liquid hydrogen is easier to vaporize than other liquid cryogenic products. Liquid hydrogen refueling stations generally have the problem of large-scale BOG emissions, which not only wastes BOG and its cooling capacity, but also poses a safety hazard to the hydrogen refueling station.

[0004] BOG has an important impact on the comprehensive energy utilization rate of liquid hydrogen refueling stations, so the efficient treatment of liquid hydrogen BOG has far-reaching application value. However, the main treatment methods for BOG at present are reliquefaction recovery and heating and recompression recovery. Since the boiling point of hydrogen is extremely low at normal pressure (20.369K), the energy consumption of hydrogen reliquefaction and heating and recompression is extremely large, and the coldness of BOG itself is treated as a "cold load", resulting in the current low energy utilization rate of treating liquid hydrogen BOG. ​​For example, the prior art first treats the coldness of BOG as a cold load for electrical heating, and then compresses and recovers BOG, adding two high-energy-consuming equipment, the electric heater and the hydrogen compressor. The BOG treatment method is extremely inefficient and fails to utilize the coldness of BOG. ​​Therefore, it has become an inevitable trend to find a new type of BOG zero-emission clean utilization method with high efficiency, low energy consumption and high reliability.

[0005] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention proposes a BOG recovery and utilization system and method for a liquid hydrogen refueling station, which is self-sufficient, has extremely low energy consumption, and efficiently utilizes liquid hydrogen BOG and its cooling capacity.

[0007] The object of the present invention is achieved through the following technical scheme: a BOG recovery and utilization system of a liquid hydrogen refueling station includes a self-evaporating steam cooling screen module, a fuel cell cogeneration module and a staged filling module, wherein:

[0008] The self-evaporating steam cooling screen module comprises:

[0009] Liquid hydrogen storage tank, used to store liquid hydrogen under normal pressure;

[0010] A liquid hydrogen tank steam cooling screen, which is connected to the liquid hydrogen tank to convert BOG cold energy into a cold source for the insulation layer;

[0011] A first valve, which is provided on the steam cooling screen of the liquid hydrogen storage tank to control the BOG flow from the liquid hydrogen storage tank;

[0012] a liquid hydrogen pipeline connected to the liquid hydrogen storage tank;

[0013] A liquid hydrogen pipeline steam cooling screen, which is wound around the liquid hydrogen pipeline and connected to the liquid hydrogen storage tank steam cooling screen to introduce BOG;

[0014] A liquid hydrogen BOG recovery tank connected to the liquid hydrogen pipeline steam cooling screen to collect the BOG;

[0015] The liquid hydrogen storage tank, the first valve, the liquid hydrogen storage tank steam cooling screen, the liquid hydrogen pipeline steam cooling screen, and the liquid hydrogen BOG recovery tank are sequentially connected to form a self-evaporation steam cooling screen module;

[0016] The fuel cell cogeneration module comprises:

[0017] A hydrogen fuel cell connected to the liquid hydrogen BOG recovery tank;

[0018] A DC chopper connected to the hydrogen fuel cell;

[0019] a storage battery connected to the DC chopper;

[0020] A fuel cell waste heat thermostat, which is connected to the hydrogen fuel cell to utilize the waste heat of the fuel cell to heat and regulate the temperature of hydrogen, and the hydrogen fuel cell and the fuel cell waste heat thermostat form a circulation loop for utilizing the waste heat of the fuel cell;

[0021] An electric heating thermostat, which uses electric energy to heat and adjust the temperature of hydrogen so that the outlet hydrogen temperature is a first temperature, the electric heating thermostat is connected in parallel with the fuel cell waste heat thermostat, and the hydrogen fuel cell, the DC chopper, the battery, and the electric heating thermostat form a circulation loop for utilizing the electric energy of the fuel cell;

[0022] An air-temperature vaporizer, which utilizes the heat of the atmospheric environment to vaporize and heat the liquid hydrogen, and the air-temperature vaporizer is connected to the liquid hydrogen storage tank;

[0023] A fuel cell cogeneration module is formed by a hydrogen fuel cell, a DC chopper, a battery, an air-temperature vaporizer, a fuel cell waste heat thermostat, and an electric heating thermostat;

[0024] The graded filling module comprises:

[0025] Cascade hydrogen buffer tanks, which fill hydrogen with different pressures into hydrogen storage tanks in multiple times by means of successive pressurization;

[0026] a hydrogenator connected to the liquid hydrogen storage tank to inject high-pressure hydrogen into the hydrogen storage tank and maintain the inlet hydrogen at a second temperature;

[0027] The cascade hydrogen buffer tank and the hydrogen filling machine are connected in sequence through the circuit to form a staged filling module.

[0028] In the BOG recovery and utilization system of the liquid hydrogen refueling station, the second valve is arranged between the liquid hydrogen BOG recovery tank and the hydrogen fuel cell, the third valve is arranged between the air-temperature vaporizer and the fuel cell waste heat thermostat, the fourth valve is arranged between the air-temperature vaporizer and the electric heating thermostat, and the fifth valve is arranged between the air-temperature vaporizer and the hydrogen refueling machine.

[0029] In the BOG recycling system of the liquid hydrogen refueling station, the outer wall of the liquid hydrogen storage tank is provided with a spray-type polyester foam layer and a variable density multi-layer thermal insulation layer close to the tank wall, a vacuum interlayer is provided between the spray-type polyester foam layer and the variable density multi-layer thermal insulation layer, and the self-evaporating steam cooling screen of the liquid hydrogen storage tank is arranged in the vacuum interlayer by winding.

[0030] In the BOG recovery and utilization system of the liquid hydrogen refueling station, the first temperature is 5°C and the second temperature is -40°C.

[0031] In the BOG recovery and utilization system of the liquid hydrogen refueling station, the hydrogen pipeline self-evaporation steam cooling screen is arranged in the vacuum interlayer outside the liquid hydrogen pipeline, and the BOG flow direction therein is opposite to the liquid hydrogen flow direction.

[0032] In the BOG recovery and utilization system of the liquid hydrogen refueling station, a liquid hydrogen booster pump is provided between the air-temperature vaporizer and the liquid hydrogen pipeline, and its rated pressure is 90 MPa.

[0033] In the BOG recycling system of the liquid hydrogen refueling station, the rated temperature of the hydrogen at the outlet of the air-temperature vaporizer is -160°C. In the electric heating mode, only the electric heating thermostat works, the fourth valve is opened, and the third valve is closed. The rated temperature of the hydrogen at the thermostat outlet is 5°C by adjusting the power of the electric heating thermostat.

[0034] In the BOG recovery and utilization system of the liquid hydrogen refueling station, in the waste heat utilization mode, the fuel cell waste heat thermostat and the electric heating thermostat work simultaneously, and the rated temperature of the hydrogen at the outlets of the two thermostats is achieved to be 5° C. by adjusting the openings of the third valve and the fourth valve.

[0035] In the BOG recycling system of the liquid hydrogen refueling station, the cascade hydrogen buffer tank uses three-level pressure buffering, the rated pressure of the first-level buffer tank is 45MPa, the rated pressure of the second-level buffer tank is 65MPa, and the rated pressure of the third-level buffer tank is 90Mpa. When filling, the first-level buffer tank is used first. When the pressure reaches 40MPa, the second-level buffer tank is enabled to fill to 60MPa, and finally the third-level buffer tank is enabled to fill to 70MPa.

[0036] The method for utilizing the BOG recovery and utilization system of the liquid hydrogen refueling station comprises the following steps:

[0037] In the electric heating mode, the first valve, the fourth valve and the fifth valve are opened, the second valve and the third valve are closed, the self-evaporation steam cooling screen module is operated, the air-temperature vaporizer is operated, the hydrogen fuel cell and the DC chopper are not operated, the battery supplies power to the electric heating thermostat, and the fuel cell waste heat thermostat is not operated;

[0038] The system starts to run, the first valve is opened, BOG enters the self-evaporation steam cooling screen of the liquid hydrogen storage tank and the self-evaporation steam cooling screen of the liquid hydrogen pipeline under the action of the pressure difference, and finally enters the liquid hydrogen BOG recovery tank, the second valve and the third valve are closed, the battery is discharged, the fourth valve is opened, the electric heating thermostat works, and the outlet hydrogen temperature is adjusted to be constant at the first temperature by adjusting the power of the electric heating, and the inlet hydrogen temperature of the hydrogenator is maintained at the second temperature by adjusting the opening of the fifth valve;

[0039] In the waste heat utilization mode, the first to fifth valves are opened, the self-evaporating steam cooling screen module is in operation, the air-temperature vaporizer is working, the hydrogen fuel cell and the DC chopper are in operation, the battery is charged, the fuel cell waste heat thermostat and the electric heating thermostat are working at the same time, and the liquid hydrogen BOG recovery tank provides continuous hydrogen for the hydrogen fuel cell. The first valve is closed, the second valve is opened, the fuel cell starts to work, and the generated electric energy is used to charge the battery through the DC chopper. The generated waste heat provides thermal energy for the fuel cell waste heat thermostat to achieve fuel cell cogeneration. The third valve and the fourth valve are opened, the electric heating thermostat is working, and by adjusting the opening of the two valves, the flow rate of the inlet section of the two thermostats is controlled, the outlet hydrogen temperature is adjusted, and the outlet hydrogen temperature is kept constant. The inlet hydrogen temperature of the hydrogenator is maintained at the second temperature by adjusting the opening of the fifth valve.

[0040] Compared with the prior art, the present invention has the following advantages: The present invention has high utilization rate of liquid hydrogen BOG cold energy. The present invention can make full use of BOG cold energy through dual cold energy utilization of liquid hydrogen storage tank steam cooling screen and liquid hydrogen pipeline steam cooling screen. The liquid hydrogen pipeline steam cooling screen uses a countercurrent structure to further utilize the liquid hydrogen BOG cold energy. The thermal insulation performance of the system is greatly improved. The self-evaporating steam cooling screen greatly enhances the thermal insulation performance of the liquid hydrogen storage tank and the transportation pipeline, thereby reducing the total evaporation loss of the hydrogen station system. The liquid hydrogen steam cooling screen uses a winding structure, which can increase the heat exchange area between BOG and liquid hydrogen in the pipeline. The countercurrent structure is used to further improve the heat transfer efficiency and reduce the heat leakage of the system. The energy utilization rate of liquid hydrogen BOG is high. The present invention uses liquid hydrogen BOG for fuel cell power generation, and makes full use of the waste heat of the fuel cell when it is working. At the same time, it uses electrical energy and thermal energy to provide energy for hydrogen heating and temperature adjustment, realizes fuel cell cogeneration, reduces the external energy consumption of the system, and realizes the internal BOG energy utilization of the system. The hydrogen outlet temperature is precisely controlled. Through the coordinated work of the fuel cell waste heat thermostat and the electric heating thermostat, the temperature of the hydrogen at the thermostat outlet can be accurately controlled, and the hydrogen temperature can be further accurately controlled through two-phase mixing at the hydrogen filling machine outlet. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0042] In the attached picture:

[0043] Figure 1 is a schematic diagram of the structure of a system according to an embodiment of the present invention;

[0044] Figure 2 It is a structural schematic diagram of a self-evaporating steam cooling screen module according to an embodiment of the present invention.

[0045] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0046] The following will refer to the attached Figure 1 to Figure 2Specific embodiments of the present invention are described in more detail. Although specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0047] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0048] To facilitate understanding of the embodiments of the present invention, further explanation will be given below by taking specific embodiments as examples in conjunction with the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0049] For a better understanding, Figure 1 to Figure 2 As shown, a BOG recovery and utilization system of a liquid hydrogen refueling station includes a self-evaporating steam cooling screen module, a fuel cell cogeneration module, and a staged filling module.

[0050] The self-evaporating steam cooling screen module comprises:

[0051] Liquid hydrogen storage tank 1, used to store extremely low temperature liquid hydrogen under normal pressure,

[0052] The first valve 2 is used to control the BOG flow in the liquid hydrogen storage tank.

[0053] The liquid hydrogen tank steam cooling screen 3 is used to convert the BOG cold energy into a cold source for the insulation layer, and utilize the low-temperature BOG sensible heat to remove heat leakage, reduce the temperature of the insulation layer, and reduce the daily evaporation rate.

[0054] Liquid hydrogen pipeline steam cooling screen 4 uses the residual cooling capacity of low-temperature BOG to reduce the temperature of the pipeline insulation layer and reduce the heat leakage of the pipeline.

[0055] Liquid hydrogen BOG recovery tank 5 is used to collect BOG to achieve continuous supply of hydrogen source for fuel cells.

[0056] The second valve 6 is used to achieve a stable hydrogen source supply for the hydrogen fuel cell.

[0057] The liquid hydrogen storage tank 1, the first valve 2, the liquid hydrogen storage tank steam cooling screen 3, the liquid hydrogen pipeline steam cooling screen 4, and the liquid hydrogen BOG recovery tank 5 are sequentially connected through pipelines to form a self-evaporation steam cooling screen module;

[0058] The fuel cell cogeneration module comprises:

[0059] Hydrogen fuel cell7, a device that converts the chemical energy of hydrogen into electrical and thermal energy.

[0060] The DC chopper 8 converts the DC power with a fixed voltage value into a DC power supply device with a variable voltage value.

[0061] Battery 9, a device for storing the electrical energy generated by the fuel cell

[0062] The air temperature vaporizer 11 utilizes the heat from the atmospheric environment to vaporize and heat the liquid hydrogen.

[0063] The fuel cell waste heat thermostat 14 uses the waste heat of the fuel cell to heat and regulate the temperature of the low-temperature hydrogen.

[0064] The electric heating thermostat 15 uses electric energy to heat and regulate the temperature of the low-temperature hydrogen.

[0065] The third valve 12 and the fourth valve 13 are used to adjust the flow of the two thermostats and adjust the outlet hydrogen temperature.

[0066] The hydrogen fuel cell 7 and the fuel cell waste heat thermostat 14 form a circulation loop for utilizing the waste heat of the fuel cell. The hydrogen fuel cell 7, the DC chopper 8, the storage battery 9, and the electric heating thermostat 15 form a circulation loop for utilizing the electric energy of the fuel cell. The hydrogen fuel cell 7, the DC chopper 8, the storage battery 9, the air-temperature vaporizer 11, the third valve 12, the fourth valve 13, the fuel cell waste heat thermostat 14, and the electric heating thermostat 15 form a fuel cell cogeneration module.

[0067] The graded filling module comprises:

[0068] The fifth valve 16 is used to adjust the final filling temperature.

[0069] The cascade hydrogen buffer tank 17 fills hydrogen with different pressures into the vehicle-mounted hydrogen storage tank in multiple times in a step-by-step pressurization manner to reduce the heat generated during filling, thereby increasing the filling rate and reducing the filling safety risk.

[0070] A hydrogen filling machine 18 is a device for injecting high-pressure hydrogen into a vehicle-mounted hydrogen storage tank,

[0071] The cascade hydrogen buffer tank 17, the temperature regulating valve 16 and the hydrogenator 18 are connected in sequence through a circuit to form a staged filling module.

[0072] The self-evaporating steam cooling screen 4 of the liquid hydrogen pipeline is placed in the vacuum interlayer 24 outside the liquid hydrogen pipeline and adopts a countercurrent structure in which the flow direction of BOG is opposite to that of liquid hydrogen to further fully utilize the coldness of BOG. ​​The outside is wrapped with thermal insulation cotton 23.

[0073] In one embodiment, the outer wall of the liquid hydrogen storage tank 1 is wrapped by a spray polyester foam layer 19, the spray polyester foam layer 19 wraps the first variable density multilayer insulation layer 20, the first variable density multilayer insulation layer 20 is provided with a second variable density multilayer insulation layer 21, and the first variable density multilayer insulation layer 20 is provided with a second variable density multilayer insulation layer 21, and a vacuum layer is provided between them. The top of the liquid hydrogen storage tank 1 is connected to the liquid hydrogen pipeline steam cooling screen 3 through the first valve 2, and the liquid hydrogen pipeline steam cooling screen 3 is wound around the first variable density multilayer insulation layer 20 in the vacuum layer and then led out from the second variable density multilayer insulation layer 21. Preferably, the first variable density multilayer insulation layer 20 and the second variable density multilayer insulation layer 21 are three-stage, and a low-density insulation layer of 7 layers / cm is used on the low-temperature side, with a total of 10 layers, which effectively reduces heat leakage in the form of heat conduction, a medium-density insulation layer of 11 layers / cm is used in the middle, with a total of 20 layers, and a high-density insulation layer of 21 layers / cm is used on the high-temperature side, with a total of 20 layers, which effectively reduces heat leakage in the form of radiation. The equivalent thermal conductivity of the spray polyester foam 19 combined with the first variable density multilayer thermal insulation layer 20 and the second variable density multilayer thermal insulation layer 21 is calculated to be only 10 -3 W·m -1 ·K -1 On this basis, the self-evaporating steam cooling screen 3 can further reduce the heat leakage by 30% to 50% depending on the placement position.

[0074] In one embodiment, the rated pressure of the liquid hydrogen booster pump outlet is 90 MPa.

[0075] In one embodiment, the liquid hydrogen pipeline is provided with a pipeline insulation layer 23 and a pipeline vacuum interlayer 24 is provided therebetween. In one embodiment, the liquid hydrogen pipeline steam cooling screen 4 penetrates into the above-mentioned pipeline insulation layer 23, wraps around the liquid hydrogen pipeline in the pipeline vacuum interlayer 24, and then passes through the pipeline insulation layer 23.

[0076] In one embodiment, the rated temperature of hydrogen at the outlet of the air-temperature vaporizer 11 is -160°C. In the electric heating mode, only the electric heating thermostat works, the fourth valve 13 is opened, the third valve 12 is closed, and the rated temperature of hydrogen at the thermostat outlet is 5°C by adjusting the power of the electric heating thermostat 15. In the waste heat utilization mode, the fuel cell waste heat thermostat 14 and the electric heating thermostat 15 work simultaneously, and the rated temperature of hydrogen at the outlets of the two thermostats is 5°C by adjusting the opening of the third valve 12 and the fourth valve 13.

[0077] In one embodiment, a fifth valve 16 is provided before the inlet of the hydrogen filling machine, where low-temperature liquid hydrogen is mixed with hydrogen gas, and the temperature during hydrogenation is adjusted to about -40°C to avoid excessively high temperature during filling. This helps to increase the filling rate on the one hand, and protect the on-board liquid hydrogen storage tank on the other hand, extending its service life.

[0078] In one embodiment, the cascade hydrogen buffer tank in the staged filling module uses three-level pressure buffering, the rated pressure of the first-level buffer tank is 45MPa, the rated pressure of the second-level buffer tank is 65MPa, and the rated pressure of the third-level buffer tank is 90MPa. When filling, the first-level buffer tank is used first, and when the pressure of the vehicle storage pipe reaches 40MPa, the second-level buffer tank is used to fill the vehicle storage pipe to 60MPa, and finally the third-level buffer tank is used to fill the vehicle storage pipe to 70MPa.

[0079] In one embodiment, the self-evaporating steam cooling screen module includes a liquid hydrogen storage tank 1 for storing low-temperature liquid hydrogen, a first valve 2 for controlling BOG release, a liquid hydrogen storage tank steam cooling screen 3 for enhancing thermal insulation performance by using BOG cold, a liquid hydrogen pipeline steam cooling screen 4 for reducing pipeline heat leakage, a liquid hydrogen BOG recovery tank 5 for storing BOG, and a second valve 6 for providing a stable hydrogen source for the fuel cell. The second valve 6 is connected to a hydrogen fuel cell 7 of a fuel cell cogeneration module, and a battery 9 is charged by a DC chopper 8. A liquid hydrogen booster pump 10 presses the liquid hydrogen into an air-temperature vaporizer 11 after pressurizing the liquid hydrogen, and the liquid hydrogen is vaporized and heated by atmospheric heat. A fuel cell waste heat thermostat 14 uses the waste heat of the hydrogen fuel cell 7 to heat and adjust the temperature of the low-temperature hydrogen. The battery 9 supplies energy to an electric heating thermostat 15 to heat and adjust the temperature of the low-temperature hydrogen. The high-pressure hydrogen after temperature adjustment enters a cascade liquid hydrogen buffer tank 17, and enters a hydrogenator 18 after being mixed with liquid hydrogen through a fifth valve 16 before the hydrogenator and temperature adjustment.

[0080] The operation modes of the BOG comprehensive utilization system of the liquid hydrogen refueling station include an electric heating mode when the fuel cell is not working, and a waste heat utilization mode when the fuel cell is working, which are specifically as follows:

[0081] In the electric heating mode,

[0082] The first valve, the fourth valve 13 and the fifth valve 16 are opened, the second valve 6 and the third valve 12 are closed, the self-evaporation steam cooling screen module operates, the hydrogen fuel cell 7 and the DC chopper 8 do not operate, the battery 9 supplies power to the electric heating thermostat 14, the air-temperature vaporizer 11 operates, the fuel cell waste heat thermostat 14 does not operate, and only the electric heating thermostat 14 operates.

[0083] At this time, the whole system just starts to run, the first valve 2 is opened, and BOG enters the liquid hydrogen storage tank self-evaporation steam cooling screen 3 and the liquid hydrogen pipeline self-evaporation steam cooling screen 4 under the action of pressure difference, and finally enters the liquid hydrogen BOG recovery tank 5. At this time, the pressure of the liquid hydrogen BOG recovery tank is low and cannot provide continuous hydrogen for the hydrogen fuel cell 7. The second valve 6 and the third valve 12 are closed, the battery 9 supplies power to the electric heating thermostat 14, and only the electric heating thermostat is used to work. The fourth valve 13 is opened, and the outlet hydrogen temperature is adjusted by adjusting the power of the thermostat to achieve a constant outlet hydrogen temperature. The hydrogen temperature at the inlet of the hydrogenator is maintained at -40°C by adjusting the opening of the fifth valve 16.

[0084] The waste heat utilization mode,

[0085] All five valves 2, 6, 12, 13 and 16 are opened, the self-evaporative steam cooling screen module is in operation, the hydrogen fuel cell 7 and the DC chopper are in operation 8, the battery is charged 9, and the fuel cell waste heat thermostat 14 and the electric heating thermostat 15 work simultaneously.

[0086] At this time, the liquid hydrogen BOG recovery tank 5 reaches a certain pressure and can provide continuous hydrogen for the hydrogen fuel cell 7. The first valve 2 is closed, the second valve 6 is opened, the fuel cell starts to work, and the generated electric energy is used to charge the battery 9 through the DC chopper 8. The generated waste heat provides thermal energy for the fuel cell waste heat thermostat 14 through a thermal cycle to achieve cogeneration of heat and power for the fuel cell. The electric heating thermostat works, opens the third valve and the fourth valve, and controls the flow of the inlet sections of the two vaporizers by adjusting the opening of the two valves, adjusts the outlet hydrogen temperature, and achieves a constant outlet hydrogen temperature. The inlet hydrogen temperature of the hydrogenator is maintained at -40°C by fine-tuning the opening of the fifth valve 16.

[0087] like Figure 2 As shown, in the electric heating mode, the first valve 2 is opened and the second valve 6 is closed. At this time, the whole system just starts to run, the liquid hydrogen in the liquid hydrogen storage tank will evaporate slowly, and the BOG enters the storage tank self-evaporating steam cooling screen 3 under the action of the pressure difference, and then enters the pipeline self-evaporating steam cooling screen 4. The cold energy of the BOG is used for system insulation and then enters the liquid hydrogen BOG recovery tank 5. At this time, the pressure of the liquid hydrogen BOG recovery tank 5 gradually increases.

[0088] When in heat utilization mode, at this time, the liquid hydrogen BOG recovery tank reaches a certain pressure, which can provide continuous hydrogen for the hydrogen fuel cell. The first valve and the second valve are opened to provide a constant flow of room temperature hydrogen to the fuel cell. The fuel cell starts to work, and the generated electricity is used to charge the battery through the DC chopper. The waste heat generated provides thermal energy for the fuel cell waste heat thermostat, realizing the cogeneration of fuel cell heat and power.

[0089] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields, and the above specific embodiments are only illustrative and instructive, rather than restrictive. A person of ordinary skill in the art can also make many forms under the guidance of this specification and without departing from the scope of protection of the claims of the present invention, all of which belong to the protection of the present invention.

Claims

1. A BOG recycling system for a liquid hydrogen refueling station, characterized in that: It includes a self-evaporating steam cooling screen module, a fuel cell cogeneration module and a staged filling module, wherein: The self-evaporating steam cooling screen module comprises: Liquid hydrogen storage tank, used to store liquid hydrogen under normal pressure; A liquid hydrogen tank steam cooling screen, which is connected to the liquid hydrogen tank to convert BOG cold energy into a cold source for the insulation layer; A first valve, which is provided on the steam cooling screen of the liquid hydrogen storage tank to control the BOG flow from the liquid hydrogen storage tank; a liquid hydrogen pipeline connected to the liquid hydrogen storage tank; A liquid hydrogen pipeline steam cooling screen, which is wound around the liquid hydrogen pipeline and connected to the liquid hydrogen storage tank steam cooling screen to introduce BOG; A liquid hydrogen BOG recovery tank connected to the liquid hydrogen pipeline steam cooling screen to collect the BOG; The liquid hydrogen storage tank, the first valve, the liquid hydrogen storage tank steam cooling screen, the liquid hydrogen pipeline steam cooling screen, and the liquid hydrogen BOG recovery tank are sequentially connected to form a self-evaporation steam cooling screen module; The fuel cell cogeneration module comprises: A hydrogen fuel cell connected to the liquid hydrogen BOG recovery tank; A DC chopper connected to the hydrogen fuel cell; a battery connected to the DC chopper; A fuel cell waste heat thermostat, which is connected to the hydrogen fuel cell to utilize the waste heat of the fuel cell to heat and regulate the temperature of hydrogen, and the hydrogen fuel cell and the fuel cell waste heat thermostat form a circulation loop for utilizing the waste heat of the fuel cell; An electric heating thermostat, which uses electric energy to heat and adjust the temperature of hydrogen so that the outlet hydrogen temperature is a first temperature, the electric heating thermostat is connected in parallel with the fuel cell waste heat thermostat, and the hydrogen fuel cell, the DC chopper, the battery, and the electric heating thermostat form a circulation loop for utilizing the electric energy of the fuel cell; An air-temperature vaporizer, which utilizes the heat of the atmospheric environment to vaporize and heat the liquid hydrogen, and the air-temperature vaporizer is connected to the liquid hydrogen storage tank; A fuel cell cogeneration module is formed by a hydrogen fuel cell, a DC chopper, a battery, an air-temperature vaporizer, a fuel cell waste heat thermostat, and an electric heating thermostat; The graded filling module comprises: Cascade hydrogen buffer tanks, which fill hydrogen with different pressures into hydrogen storage tanks in multiple times by means of successive pressurization; a hydrogenator connected to the liquid hydrogen storage tank to inject high-pressure hydrogen into the hydrogen storage tank and maintain the inlet hydrogen at a second temperature; The cascade hydrogen buffer tank and the hydrogen filling machine are connected in sequence through the circuit to form a staged filling module.

2. The BOG recycling system of the liquid hydrogen refueling station according to claim 1, characterized in that: The second valve is arranged between the liquid hydrogen BOG recovery tank and the hydrogen fuel cell, the third valve is arranged between the air-temperature vaporizer and the fuel cell waste heat thermostat, the fourth valve is arranged between the air-temperature vaporizer and the electric heating thermostat, and the fifth valve is arranged between the air-temperature vaporizer and the hydrogenator.

3. The BOG recycling system of the liquid hydrogen refueling station according to claim 1, characterized in that: The outer wall of the liquid hydrogen storage tank is provided with a spray-type polyester foam layer and a variable density multi-layer thermal insulation layer close to the tank wall, a vacuum interlayer is provided between the spray-type polyester foam layer and the variable density multi-layer thermal insulation layer, and the liquid hydrogen storage tank steam cooling screen is arranged in the vacuum interlayer by winding.

4. The BOG recycling system of the liquid hydrogen refueling station according to claim 1, characterized in that: The first temperature is 5°C and the second temperature is -40°C.

5. The BOG recycling system of the liquid hydrogen refueling station according to claim 1, characterized in that: The liquid hydrogen pipeline steam cooling screen is placed in the vacuum interlayer outside the liquid hydrogen pipeline and the BOG flow direction therein is opposite to the liquid hydrogen flow direction.

6. The BOG recycling system of the liquid hydrogen refueling station according to claim 1, characterized in that: A liquid hydrogen booster pump is provided between the air-temperature vaporizer and the liquid hydrogen pipeline, and its rated pressure is 90 MPa.

7. The BOG recycling system of the liquid hydrogen refueling station according to claim 2, characterized in that: The rated temperature of hydrogen at the outlet of the air-temperature vaporizer is -160°C. In the electric heating mode, only the electric heating thermostat works, the fourth valve is opened, and the third valve is closed. The rated temperature of hydrogen at the thermostat outlet is 5°C by adjusting the power of the electric heating thermostat.

8. The BOG recycling system of the liquid hydrogen refueling station according to claim 2, characterized in that: In the waste heat utilization mode, the fuel cell waste heat thermostat and the electric heating thermostat work simultaneously, and the rated temperature of the hydrogen at the outlets of the two thermostats is achieved to be 5°C by adjusting the opening of the third valve and the fourth valve.

9. The BOG recycling system of the liquid hydrogen refueling station according to claim 1, characterized in that: The cascade hydrogen buffer tank uses three-level pressure buffering. The rated pressure of the first-level buffer tank is 45MPa, the rated pressure of the second-level buffer tank is 65MPa, and the rated pressure of the third-level buffer tank is 90Mpa. When filling, the first-level buffer tank is used first. When the pressure reaches 40MPa, the second-level buffer tank is enabled to fill to 60MPa, and finally the third-level buffer tank is enabled to fill to 70MPa.

10. The method for utilizing the BOG recovery and utilization system of a liquid hydrogen refueling station according to any one of claims 2 to 9, characterized in that: It includes the following steps, In the electric heating mode, the first valve, the fourth valve and the fifth valve are opened, the second valve and the third valve are closed, the self-evaporation steam cooling screen module is operated, the air-temperature vaporizer is operated, the hydrogen fuel cell and the DC chopper are not operated, the battery supplies power to the electric heating thermostat, and the fuel cell waste heat thermostat is not operated; The system starts to run, the first valve is opened, BOG enters the steam cooling screen of the liquid hydrogen storage tank and the steam cooling screen of the liquid hydrogen pipeline under the action of the pressure difference, and finally enters the liquid hydrogen BOG recovery tank, the second valve and the third valve are closed, the battery is discharged, the fourth valve is opened, the electric heating thermostat works, and the outlet hydrogen temperature is adjusted to be constant at the first temperature by adjusting the power of the electric heating, and the inlet hydrogen temperature of the hydrogenator is maintained at the second temperature by adjusting the opening of the fifth valve; In the waste heat utilization mode, the first to fifth valves are opened, the self-evaporating steam cooling screen module is in operation, the air-temperature vaporizer is working, the hydrogen fuel cell and the DC chopper are in operation, the battery is charged, the fuel cell waste heat thermostat and the electric heating thermostat are working at the same time, and the liquid hydrogen BOG recovery tank provides continuous hydrogen for the hydrogen fuel cell. The first valve is closed, the second valve is opened, the hydrogen fuel cell starts to work, and the generated electric energy is used to charge the battery through the DC chopper. The generated waste heat provides thermal energy for the fuel cell waste heat thermostat to achieve fuel cell cogeneration. The third valve and the fourth valve are opened, the electric heating thermostat is working, and by adjusting the opening of the two valves, the flow rate of the inlet section of the two thermostats is controlled, the outlet hydrogen temperature is adjusted, and the outlet hydrogen temperature is kept constant. The inlet hydrogen temperature of the hydrogen refueling machine is maintained at the second temperature by adjusting the opening of the fifth valve.

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