A device for reducing the evaporation rate of liquid hydrogen tanks in ships

Abstract

The present application relates to the field of liquid hydrogen transportation on ships, and discloses a device for reducing the evaporation rate of a ship's liquid hydrogen tank. The device is arranged based on a liquid hydrogen tank and an LNG tank, and includes a cooling coil arranged outside the liquid hydrogen tank. The inlet of the cooling coil is connected to the liquid hydrogen tank and the LNG tank, and the outlet of the cooling coil is connected to the LNG tank and the outside of the device. The device includes a cooling path one: hydrogen boil-off gas enters the cooling coil from the liquid hydrogen tank to cool the liquid hydrogen tank, and then flows out of the device outside; cooling path two: LNG boil-off gas enters the cooling coil from the LNG tank to cool the liquid hydrogen tank, and then flows out of the device outside or flows back to the LNG tank; cooling path three: LNG liquid enters the cooling coil from the LNG tank to cool the liquid hydrogen tank, and then flows out of the device outside or flows back to the LNG tank. The device of the present application effectively reduces the evaporation rate of cargo in the liquid hydrogen tank, fully utilizes hydrogen boil-off gas and LNG cold energy, and greatly reduces the transportation cost and fuel cost of liquid hydrogen transport ships.

Description

Technical Field

[0001] The present application relates to the field of liquid hydrogen transportation on ships, and more specifically, to a device for reducing the evaporation rate of liquid hydrogen tanks on ships. Background Art

[0002] Hydrogen is a readily available, green, low-carbon, and widely used secondary energy source. Liquid hydrogen tankers can efficiently transport hydrogen. Liquid hydrogen has a temperature as low as -253°C. During transportation, the temperature difference between liquid hydrogen cargo and the ambient temperature is significant, causing it to evaporate and potentially cause losses. Therefore, effectively reducing the evaporation rate in liquid hydrogen tanks is crucial.

[0003] There are two main ways to reduce the evaporation rate of liquid hydrogen tanks in the existing technology: one is to reduce the evaporation rate by designing the liquid hydrogen tank body and the insulation layer structure. However, due to the limitations of the insulation material performance, facing the extremely low temperature of liquid hydrogen, conventional insulation material coating methods have been difficult to further reduce the evaporation rate. Usually, vacuum insulation or a combination of vacuum insulation + insulation material coating is selected; the other is to change the temperature field distribution outside the liquid hydrogen tank, increase the external low-temperature medium for cooling, and reduce the temperature difference between the liquid hydrogen tank and the external environment, thereby reducing the evaporation rate. The more commonly used method is to inject liquid nitrogen to isolate it from the external environment. This method requires long-term consumption of a large amount of liquid nitrogen, which is a huge challenge to the source and cost of liquid nitrogen supply on ships.

[0004] Chinese patent publication number CN117662974A discloses a vapor cooling system and operating method for large shipboard liquid hydrogen tanks. The system dynamically switches the vapor cooling screen operating mode in real time based on the marine ambient temperature and the actual operating conditions of the liquid hydrogen tank. In low-heat-leakage scenarios, the system operates in a two-stage series passive vapor cooling screen mode, while in high-heat-leakage scenarios, the system operates in an active-passive combination vapor cooling screen mode. This effectively extends the liquid hydrogen storage period while saving refrigeration energy. However, this method relies solely on passive cooling by hydrogen evaporated gas, which has limited effectiveness. Operating the active-passive combination vapor cooling screen mode requires an active refrigeration system and the manufacture of a specialized cold shielding layer, resulting in a complex and costly system.

[0005] Among the above measures, whether liquid nitrogen is used for cold preservation or active refrigeration of hydrogen evaporated gas, a large amount of cryogenic medium or refrigeration energy consumption is involved. The ship power station is small and it is difficult to store liquid nitrogen medium, so the application in the ship field is very difficult and inconvenient.

[0006] Therefore, how to develop a device that can effectively reduce the evaporation rate of the ship's liquid hydrogen tank based on the existing conditions of liquid hydrogen transport ships is of great significance to the development of the field of ship liquid hydrogen transportation. Summary of the Invention

[0007] For liquid hydrogen transport ships, the sea transportation cycle is long and the evaporation of liquid hydrogen cargo cannot be ignored. Therefore, the purpose of the invention of this application is to provide a device with simple structure, low cost and good refrigeration effect to reduce the evaporation rate of the liquid hydrogen tank.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides a device for reducing the evaporation rate of a liquid hydrogen tank of a ship, which adopts the following technical solution:

[0009] The first invention provides a device for reducing the evaporation rate of a liquid hydrogen tank on a ship. The device is installed based on the liquid hydrogen tank and LNG tank of a liquid hydrogen transport ship, and includes two or more groups of cooling coils installed outside the liquid hydrogen tank. The inlet of the cooling coil is connected to the liquid hydrogen tank and the LNG tank, and the outlet of the cooling coil is connected to the LNG tank and the outside of the device.

[0010] The device is provided with three cooling paths for cooling the liquid hydrogen cabin, including:

[0011] Cooling path 1: Hydrogen evaporated gas enters the cooling coil from the liquid hydrogen tank to cool the liquid hydrogen tank, and then flows out of the device from the cooling coil outlet;

[0012] Cooling path 2: LNG evaporated gas enters the cooling coil from the LNG tank to cool the liquid hydrogen tank, and then flows out of the device from the cooling coil outlet or flows back into the LNG tank;

[0013] Cooling path three: LNG liquid enters the cooling coil from the LNG tank to cool the liquid hydrogen tank, and then flows out of the device from the cooling coil outlet or flows back to the LNG tank.

[0014] Furthermore, the liquid hydrogen tank includes an inner wall and an outer wall of the liquid hydrogen tank, the interlayer between the inner wall and the outer wall of the liquid hydrogen tank adopts a vacuum insulation form, and an insulating coating material is provided on the outer side of the outer wall of the liquid hydrogen tank.

[0015] Furthermore, the cooling coil is arranged close to the outer wall of the liquid hydrogen tank, and the cooling coil includes an upper cooling coil and a lower cooling coil, and the upper cooling coil and the lower cooling coil are respectively arranged at the upper part and the lower part of the liquid hydrogen tank.

[0016] Furthermore, multiple groups of control valves for hydrogen boil-off gas are provided at the inlet of the cooling coil, including a hydrogen lower cooling coil inlet control valve, a hydrogen upper cooling coil inlet control valve and a hydrogen boil-off gas main valve connected to the liquid hydrogen tank, which are used to control the opening and closing of the hydrogen boil-off gas supply to control the working process of the cooling path one.

[0017] Furthermore, the LNG tank includes an LNG tank inner wall and an LNG tank insulation layer, and multiple groups of control valves for LNG are also provided at the inlet of the cooling coil, including an LNG lower cooling coil inlet control valve, an LNG upper cooling coil inlet control valve and an LNG boil-off gas main valve provided at the inlet of the cooling coil, which are used to control the opening and closing of the LNG boil-off gas supply to control the working process of the cooling passage two.

[0018] Furthermore, the LNG tank includes an LNG tank inner wall and an LNG tank insulation layer, and multiple groups of control valves for LNG are also provided at the inlet of the cooling coil, including an LNG lower cooling coil inlet control valve, an LNG upper cooling coil inlet control valve and an LNG liquid main valve provided at the inlet of the cooling coil, which are used to control the opening and closing of the LNG liquid supply to control the working process of the cooling passage three.

[0019] Furthermore, a temperature sensor is provided at the outlet of the cooling coil for monitoring the temperature state of the cooling coil outlet and adjusting the control valve group according to temperature changes, and a cooling coil outlet control valve is also provided at the outlet of the cooling coil.

[0020] Furthermore, an LNG reflux pressure relief valve is provided on the passage connecting the cooling coil outlet and the LNG tank, for opening or closing the reflux passage of LNG liquid or LNG evaporated gas.

[0021] Furthermore, the device also includes a heating device, a compressor and an air supply valve; the heating device, the compressor and the air supply valve are all arranged on the passage connecting the outlet of the cooling coil and the outside of the device, the heating device is used to heat the evaporated gas at the outlet of the cooling coil to room temperature, so that it is convenient for subsequent hydrogen or natural gas users to use it as fuel; the compressor is used to pressurize room-temperature hydrogen or natural gas or a mixture of the two for use by hydrogen or natural gas users; the air supply valve is used to supply room-temperature hydrogen or natural gas or a mixture of the two without pressurization for use by hydrogen or natural gas users.

[0022] In a second aspect, the present application provides a working method of the device described in the first aspect, including the following three working states:

[0023] Working state 1: When the ship uses hydrogen as fuel, the hydrogen boil-off gas is used to reduce the evaporation rate of the liquid hydrogen tank. After passing through the hydrogen boil-off gas main valve, the hydrogen boil-off gas passes through the hydrogen lower cooling coil inlet control valve and the hydrogen upper cooling coil inlet control valve respectively, and enters the upper cooling coil and the lower cooling coil, thereby achieving cooling of the liquid hydrogen tank;

[0024] Working state 2: When the ship uses LNG boil-off gas as ship fuel, the LNG boil-off gas is used to reduce the evaporation rate of the liquid hydrogen tank. After passing through the LNG boil-off gas main valve, the LNG boil-off gas passes through the LNG lower cooling coil inlet control valve and the LNG upper cooling coil inlet control valve respectively, and enters the upper cooling coil and the lower cooling coil, thereby achieving cooling of the liquid hydrogen tank;

[0025] Working state three: When the ship does not use hydrogen or LNG boil-off gas as fuel, and regardless of whether the ship uses LNG liquid as fuel, LNG liquid can be directly extracted to reduce the evaporation rate of the liquid hydrogen tank. An LNG pump is installed in the LNG tank to pump out the LNG liquid. After the LNG liquid passes through the LNG liquid main valve, it passes through the LNG lower cooling coil inlet control valve and the LNG upper cooling coil inlet control valve respectively, and then enters the upper cooling coil and the lower cooling coil, thereby achieving cooling of the liquid hydrogen tank.

[0026] Compared with the prior art, the device of the present invention has the following beneficial effects:

[0027] 1. Make full use of the cold energy of hydrogen and LNG fuel in liquid hydrogen carriers, and take cooling measures for liquid hydrogen tanks by utilizing the evaporated gas generated during the transportation of liquid hydrogen by liquid hydrogen carriers, or LNG liquid, or LNG evaporated gas as a cooling source. By using cooling coils wrapped around the metal outer wall of the vacuum liquid hydrogen tank, the temperature of the metal outer wall of the liquid hydrogen tank is reduced, thereby reducing the temperature difference between the inner and outer walls of the liquid hydrogen tank, significantly reducing heat leakage from the external environment, and reducing the evaporation rate of liquid hydrogen cargo and cargo losses. Compared with the devices for reducing the evaporation rate of liquid hydrogen tanks in the prior art, this device does not require the use of other cryogenic working fluids such as liquid nitrogen or a dedicated hydrogen refrigeration system, and can fully utilize the cold energy of the ship's cryogenic fuel. The implementation method is simple and the implementation cost is low.

[0028] 2. By dividing the boil-off gas cooling coil into an upper cooling coil and a lower cooling coil, the cooling coils are placed in close contact with the metal outer wall of the vacuum liquid hydrogen tank. Leveraging the excellent thermal conductivity of the metal outer wall, a small number of cooling coils can cool the entire metal outer wall, forming a complete cryogenic layer. When cooling energy is insufficient, air is supplied to the lower cooling coil first, ensuring effective cooling of the liquid hydrogen cargo at the bottom of the tank and reducing the generation of hydrogen boil-off gas.

[0029] 3. The device of the invention combines the characteristics of ship fuel use and is compatible with three cooling methods: liquid hydrogen boil-off gas, LNG liquid, and LNG boil-off gas. Through the flow adjustment of the outlet temperature sensor and the control valve, it can achieve three different levels of liquid hydrogen tank evaporation rate reduction effects:

[0030] (1) During the cooling period using LNG boil-off gas, the temperature difference between the inner and outer walls of the liquid hydrogen tank is controlled between 150 and 200°C.

[0031] (2) During the use of LNG liquid cooling, the temperature difference between the inner and outer walls of the liquid hydrogen tank is controlled between 90 and 150°C.

[0032] (3) During the cooling period using liquid hydrogen boil-off gas, the temperature difference between the inner and outer walls of the liquid hydrogen tank is controlled between 50 and 150°C.

[0033] 4. The present invention uses the same type of compressor to extract hydrogen boil-off gas and LNG boil-off gas, avoiding the need to equip two independent sets of hydrogen compressors and LNG boil-off gas compressors. At the same time, it can also mix hydrogen fuel and LNG fuel in a certain proportion and extract the mixed gas as fuel, so that the same type of compressor can simultaneously control the liquid hydrogen tank pressure and the LNG tank pressure, greatly reducing the compressor equipment configuration cost and having a fuel mixing function.

[0034] 5. When the ship is not sailing or using hydrogen or LNG fuel for other reasons, the LNG pump can be used to directly extract LNG to cool the outer wall of the vacuum jacketed liquid hydrogen tank, and the cooled LNG liquid and evaporated gas can be returned to the LNG tank, realizing active cooling of the liquid hydrogen tank to reduce the evaporation rate without wasting LNG fuel.

[0035] In summary, the use of the above measures can effectively reduce the evaporation rate of liquid hydrogen cargo in the liquid hydrogen tank of the liquid hydrogen carrier, reduce the cost of compressor equipment, and make full use of hydrogen boil-off gas and LNG cold energy, saving the heat energy required for the ship to heat hydrogen boil-off gas or LNG, reducing the amount of cargo transportation losses caused by hydrogen boil-off gas as fuel, and greatly reducing the transportation cost and fuel cost of liquid hydrogen carriers. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 : Schematic diagram of the device for reducing the evaporation rate of the liquid hydrogen tank of a ship in this embodiment.

[0037] Reference numerals: 1, inner wall of liquid hydrogen tank; 2, outer wall of liquid hydrogen tank; 3, thermal insulation coating material; 4, upper cooling coil; 5, lower cooling coil; 6, hydrogen boil-off gas main valve; 7, hydrogen lower cooling coil inlet control valve; 8, hydrogen upper cooling coil inlet control valve; 9, hydrogen boil-off gas main pipeline control valve; 10, cooling coil outlet temperature sensor; 11, boil-off gas main pipeline temperature sensor; 12, heater; 13, gas compressor; 14, gas supply valve; 15, LNG tank interior Wall; 16. LNG tank insulation layer; 17. LNG pump; 18. LNG boil-off gas main valve; 19. LNG reflux valve; 20. LNG liquid main valve; 21. LNG lower cooling coil inlet control valve; 22. LNG upper cooling coil inlet control valve; 23. LNG boil-off gas main pipeline control valve; 24. LNG direct utilization control valve; 25. LNG boil-off gas direct utilization control valve; 26. Cooling coil outlet control valve, 27. LNG reflux pressure relief valve. DETAILED DESCRIPTION

[0038] The structure and effects of the present application are further described in detail below with reference to the embodiments. It is understood that the specific embodiments described herein are merely for explaining the present invention, and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only show portions, not all, of the structure relevant to the present invention.

[0039] Example

[0040] A device for reducing the evaporation rate of liquid hydrogen tanks in ships, referring to Figure 1 The device is based on the liquid hydrogen tank and LNG tank of the liquid hydrogen transport ship. The liquid hydrogen tank is used to load liquid hydrogen cargo on the liquid hydrogen transport ship and use hydrogen evaporated gas as ship fuel; the LNG tank is used to store or transport LNG and use LNG as ship fuel.

[0041] Reference Figure 1 The liquid hydrogen tank includes an inner wall 1 and an outer wall 2. The outer wall 2 is made of a metal material that is resistant to low temperatures and has good thermal conductivity. The interlayer between the inner and outer walls 1 and 2 is insulated by vacuum evacuation. If necessary, the vacuum interlayer can be filled with insulation material. An insulating coating 3 is provided on the outside of the tank. This insulating coating 3 can be made of an insulating material such as polyurethane foam or polystyrene. It is wrapped around the outer wall 2 to enhance the tank's thermal insulation performance.

[0042] Reference Figure 1 A cooling coil is provided between the outer wall 2 of the liquid hydrogen tank and the insulation layer, and the cooling coil is arranged in close proximity to the outer wall 2 of the liquid hydrogen tank. In a feasible embodiment, the cooling coil can be divided into two or more groups. In this embodiment, two groups are used as an example for explanation, i.e., the cooling coil includes an upper cooling coil 4 and a lower cooling coil 5. The upper cooling coil 4 and the lower cooling coil 5 are arranged at the upper and lower parts of the liquid hydrogen tank, respectively. The cooling coil cools the outer wall 2 of the liquid hydrogen tank, and the insulation coating material 3 entirely covers the cooling coil and the outer wall 2 of the liquid hydrogen tank. It is worth noting that the cooling coil does not need to wrap around the entire liquid hydrogen tank. It only needs to cover a partial area of ​​the liquid hydrogen tank according to the design and calculation requirements, and the outer wall 2 of the liquid hydrogen tank is cooled as a whole by utilizing the fast thermal conductivity of the metal of the outer wall 2 of the liquid hydrogen tank.

[0043] Reference Figure 1 At the inlet of the cooling coil, multiple groups of control valves for hydrogen boil-off gas are provided, including a hydrogen lower cooling coil inlet control valve 7, a hydrogen upper cooling coil inlet control valve 8 and a hydrogen boil-off gas main valve 6 connected to the liquid hydrogen tank, which are used to control the opening and closing of the hydrogen boil-off gas supply, and further adjust and control the temperature, pressure and flow of each group of cooling coils.

[0044] In one working state (when the ship uses hydrogen as ship fuel, hydrogen boil-off gas is preferentially used to reduce the evaporation rate of the liquid hydrogen tank), the hydrogen boil-off gas passes through the hydrogen boil-off gas main valve 6, and then passes through the hydrogen lower cooling coil inlet control valve 7 and the hydrogen upper cooling coil inlet control valve 8 respectively, and enters the upper cooling coil 4 and the lower cooling coil 5, thereby achieving cooling of the liquid hydrogen tank.

[0045] Reference Figure 1 The LNG tank includes an LNG tank inner wall 15 and an LNG tank insulation layer 16. The LNG tank insulation layer 16 can be vacuum insulation or an insulating coating material. The cooling coil inlet is also equipped with multiple control valves for LNG. These include a lower LNG cooling coil inlet control valve 21, an upper LNG cooling coil inlet control valve 22, and an LNG boil-off gas master valve 18. These control valves are used to control the opening and closing of the LNG boil-off gas supply and further regulate the temperature, pressure, and flow rate of each cooling coil group. If the LNG boil-off gas needs to be directly utilized, it can be directly used through the LNG boil-off gas direct utilization control valve 25.

[0046] In one working state (when the ship uses LNG boil-off gas as ship fuel, LNG boil-off gas is preferentially used to reduce the evaporation rate of the liquid hydrogen tank), the LNG boil-off gas passes through the LNG boil-off gas main valve 18, and then passes through the LNG lower cooling coil inlet control valve 21 and the LNG upper cooling coil inlet control valve 22 respectively, and enters the upper cooling coil 4 and the lower cooling coil 5, thereby achieving cooling of the liquid hydrogen tank.

[0047] Reference Figure 1 A temperature sensor 10 is also connected to the cooling coil outlet to monitor the outlet temperature, allowing the valve group to adjust based on temperature changes. The temperature sensor 10 is connected to the cooling coil outlet control valve 26, which adjusts the flow rate of each cooling group based on the outlet temperature sensor 10 to improve cooling efficiency.

[0048] Reference Figure 1 The LNG tank is also provided with an LNG pump 17 and an LNG liquid main valve 20 connected to the LNG pump 17 .

[0049] In one working state (when the ship does not use hydrogen or LNG boil-off gas as fuel, and regardless of whether the ship uses LNG liquid as fuel, LNG liquid can be directly extracted to reduce the evaporation rate of the liquid hydrogen tank), the LNG pump 17 can pump out LNG liquid. After the LNG liquid passes through the LNG liquid main valve 20, it can pass through the LNG lower cooling coil inlet control valve 21 and the LNG upper cooling coil inlet control valve 22 respectively, and enter the upper cooling coil 4 and the lower cooling coil 5, thereby achieving cooling of the liquid hydrogen tank.

[0050] Reference Figure 1 To reduce the risk of overpressure, an LNG return pressure relief valve 27 is connected to the cooling coil outlet control valve 26. This valve actively relieves overpressure caused by the cooling and vaporization of LNG liquid. Alternatively, it can be fully opened to directly return LNG liquid. LNG boil-off or LNG liquid returning through LNG return valve 27 passes through LNG return valve 19 and returns to the LNG tank.

[0051] Reference Figure 1 The device also includes a heating device 12, a compressor 13, and a gas supply valve 14. The heating device 12 is used to heat the evaporated gas at the outlet of the cooling coil to room temperature, so that it can be used as fuel by subsequent hydrogen or natural gas users. Furthermore, the compressor 13 is used to pressurize the room-temperature hydrogen or natural gas, or a mixture of the two, for use by hydrogen or natural gas users; the gas supply valve 14 is used to supply the room-temperature hydrogen or natural gas, or a mixture of the two, to hydrogen or natural gas users without pressurization.

[0052] The operating principle of the device for reducing the evaporation rate of the ship's liquid hydrogen tank in this embodiment is:

[0053] The ship uses hydrogen or LNG as fuel. Regardless of the fuel used, this device will give priority to using the cold energy of the fuel to reduce the evaporation rate of the liquid hydrogen tank; even when the ship is not using hydrogen or natural gas as fuel, LNG can be directly extracted to cool the outer wall of the liquid hydrogen tank, and the cooled LNG and its evaporated gas can be returned to the LNG fuel tank, thereby actively reducing the evaporation rate of the liquid hydrogen tank.

[0054] When hydrogen is used as a ship fuel, open the control valves 7 and 8 corresponding to the hydrogen boil-off gas to the cooling coils 4 and 5. Prioritize opening the lower cooling coil inlet and outlet control valve 7 to ensure that the lower outer wall of the liquid hydrogen tank is cooled first. If the outlet temperature of the lower cooling coil is low, open the upper cooling coil inlet and outlet control valve 8 to further cool the upper outer wall of the liquid hydrogen tank. When the hydrogen boil-off gas has sufficient cooling energy, open the hydrogen boil-off gas main pipeline control valve 9 to directly use the hydrogen boil-off gas as fuel.

[0055] When using LNG as a ship's fuel, open the LNG liquid phase main valve 20 and the control valves 21 and 22 corresponding to the LNG cooling coils 4 and 5. Prioritize opening the lower cooling coil inlet and outlet control valve 21 to ensure that the lower outer wall of the liquid hydrogen tank is cooled first. If the outlet temperature of the lower cooling coil is low, open the upper cooling coil inlet and outlet control valve 22 to further cool the upper outer wall of the liquid hydrogen tank. When sufficient LNG cooling energy is available, open the LNG boil-off gas main pipeline control valve 23 to directly utilize the LNG boil-off gas as fuel.

[0056] When using LNG fuel tank boil-off gas as ship fuel, open the LNG boil-off gas main valve 18 and the control valves 21 and 22 corresponding to the boil-off gas to the cooling coils 4 and 5. Prioritize opening the lower cooling coil inlet and outlet control valve 21 to ensure that the lower outer wall of the liquid hydrogen tank is cooled first. If the outlet temperature of the lower cooling coil is low, open the upper cooling coil inlet and outlet control valve 22 to further cool the upper outer wall of the liquid hydrogen tank. When the LNG boil-off gas has sufficient cooling energy, open the main pipeline control valve to directly use the LNG boil-off gas as fuel. When there are no LNG fuel users, open the LNG return valve 19 to return the cooled LNG and its boil-off gas to the LNG fuel tank, thereby actively reducing the evaporation rate of the liquid hydrogen tank.

[0057] The compressor automatically adapts to the above three working conditions. It can extract hydrogen boil-off gas, LNG boil-off gas, boil-off gas generated after LNG cools the liquid hydrogen tank, and mix hydrogen and LNG boil-off gas in a certain proportion to extract the mixed gas.

[0058] For some users that can use low-pressure hydrogen or natural gas as fuel, such as boilers, gas combustion devices, fuel cells, etc., they can directly provide hydrogen, natural gas or a mixture of the two as fuel through the gas supply valve without using a compressor for boosting.

[0059] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A device for reducing the evaporation rate of a liquid hydrogen tank in a ship, wherein the device is arranged based on the liquid hydrogen tank and LNG tank of a liquid hydrogen transport ship, and is characterized in that: It includes two or more groups of cooling coils arranged outside the liquid hydrogen tank, wherein the inlet of the cooling coils is connected to the liquid hydrogen tank and the LNG tank, and the outlet of the cooling coils is connected to the LNG tank and the outside of the device; The device is provided with three cooling paths for cooling the liquid hydrogen cabin, including: Cooling path 1: Hydrogen evaporated gas enters the cooling coil from the liquid hydrogen tank to cool the liquid hydrogen tank, and then flows out of the device from the cooling coil outlet; Cooling path 2: LNG evaporated gas enters the cooling coil from the LNG tank to cool the liquid hydrogen tank, and then flows out of the device from the cooling coil outlet or flows back into the LNG tank; Cooling path three: LNG liquid enters the cooling coil from the LNG tank to cool the liquid hydrogen tank, and then flows out of the device from the cooling coil outlet or flows back into the LNG tank; The cooling coil includes an upper cooling coil and a lower cooling coil, and the upper cooling coil and the lower cooling coil are respectively arranged at the upper part and the lower part of the liquid hydrogen tank; The cooling coil inlet is provided with multiple control valves for hydrogen boil-off gas, including a hydrogen lower cooling coil inlet control valve, a hydrogen upper cooling coil inlet control valve, and a hydrogen boil-off gas main valve connected to the liquid hydrogen tank, which are used to control the opening and closing of the hydrogen boil-off gas supply to control the working process of the cooling path 1; The LNG tank includes an LNG tank inner wall and an LNG tank insulation layer. The cooling coil inlet is also provided with multiple control valves for LNG, including an LNG lower cooling coil inlet control valve, an LNG upper cooling coil inlet control valve, and an LNG boil-off gas main valve provided at the cooling coil inlet, for controlling the opening and closing of the LNG boil-off gas supply to control the working process of the cooling path 2. The LNG tank is also provided with an LNG pump and an LNG liquid main valve connected to the LNG pump, which is used to control the opening and closing of the LNG liquid supply to control the working process of the cooling path three; The device includes the following three working states: Working state 1: When the ship uses hydrogen as fuel, the hydrogen boil-off gas is used to reduce the evaporation rate of the liquid hydrogen tank. After passing through the hydrogen boil-off gas main valve, the hydrogen boil-off gas passes through the hydrogen lower cooling coil inlet control valve and the hydrogen upper cooling coil inlet control valve respectively, and enters the upper cooling coil and the lower cooling coil, thereby achieving cooling of the liquid hydrogen tank; Working state 2: When the ship uses LNG boil-off gas as ship fuel, the LNG boil-off gas is used to reduce the evaporation rate of the liquid hydrogen tank. After passing through the LNG boil-off gas main valve, the LNG boil-off gas passes through the LNG lower cooling coil inlet control valve and the LNG upper cooling coil inlet control valve respectively, and enters the upper cooling coil and the lower cooling coil, thereby achieving cooling of the liquid hydrogen tank; Working state three: When the ship does not use hydrogen or LNG boil-off gas as fuel, and regardless of whether the ship uses LNG liquid as fuel, LNG liquid can be directly extracted to reduce the evaporation rate of the liquid hydrogen tank. An LNG pump is installed in the LNG tank to pump out LNG liquid. After passing through the LNG liquid main valve, the LNG liquid passes through the LNG lower cooling coil inlet control valve and the LNG upper cooling coil inlet control valve respectively, and enters the upper cooling coil and the lower cooling coil, thereby achieving cooling of the liquid hydrogen tank.

2. The device according to claim 1, characterized in that The liquid hydrogen tank includes an inner wall and an outer wall of the liquid hydrogen tank. The outer wall of the liquid hydrogen tank is made of a low-temperature resistant metal material with good heat conduction effect. The interlayer between the inner wall and the outer wall of the liquid hydrogen tank adopts a vacuum insulation form, and an insulating coating material is provided on the outside of the outer wall of the liquid hydrogen tank.

3. The device according to claim 1, characterized in that A temperature sensor is provided at the outlet of the cooling coil for monitoring the temperature state of the cooling coil outlet and adjusting the control valve group according to temperature changes. A cooling coil outlet control valve is also provided at the outlet of the cooling coil.

4. The device according to claim 3, characterized in that An LNG reflux pressure relief valve is also provided on the passage connecting the cooling coil outlet and the LNG tank, for opening or closing the reflux passage of LNG liquid or LNG evaporated gas.

5. The device according to claim 1, characterized in that The device also includes a heating device, a compressor and an air supply valve; the heating device, the compressor and the air supply valve are all arranged on the passage connecting the outlet of the cooling coil and the outside of the device. The heating device is used to heat the evaporated gas at the outlet of the cooling coil to room temperature, so that it can be used as fuel by subsequent hydrogen or natural gas users; the compressor is used to pressurize room-temperature hydrogen or natural gas or a mixture of the two for use by hydrogen or natural gas users; the air supply valve is used to supply room-temperature hydrogen or natural gas or a mixture of the two without pressurization for use by hydrogen or natural gas users.

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