Device for liquefying boil-off gas of LNG (Liquefied Natural Gas) cabin and liquid ammonia cabin by utilizing ship liquid hydrogen cold energy

Abstract

The invention relates to the field of ship transportation, and discloses a device for liquefying boil-off gas of an LNG cabin and a liquid ammonia cabin through ship liquid hydrogen cold energy. The device comprises a cold box heat exchanger, wherein a liquid hydrogen cabin and an LNG tank / liquid ammonia cabin are both communicated with the cold box heat exchanger; a liquid hydrogen boil-off gas circulation passage is arranged between the cold box heat exchanger and the liquid hydrogen cabin, and liquid hydrogen boil-off gas flows into the cold box heat exchanger from the liquid hydrogen cabin through the passage; an LNG / liquid ammonia boil-off gas circulation passage is arranged between the cold box heat exchanger and the LNG tank / liquid ammonia cabin, and LNG / liquid ammonia boil-off gas flows into the cold box heat exchanger from the LNG tank / liquid ammonia cabin through the passage; an LNG / liquid ammonia circulation channel is further arranged between the cold box heat exchanger and the LNG tank / liquid ammonia cabin, and LNG / liquid ammonia flows into the cold box heat exchanger from the LNG tank / liquid ammonia cabin through the channel. According to the device, effective utilization of the cold energy of the hydrogen evaporation gas is achieved, and the energy consumption in the LNG or liquid ammonia evaporation gas cooling and liquefying process is further reduced.

Description

Technical Field

[0001] The present application relates to the field of ship transportation, and more specifically, to a device for liquefying evaporated gas from LNG tanks and liquid ammonia tanks by utilizing the cold energy of liquid hydrogen in ships. Background Art

[0002] Hydrogen energy is a secondary energy source with abundant sources, green and low carbon, and widely used. Ships can transport hydrogen energy efficiently. The temperature of liquid hydrogen cargo is -253℃, and the temperature difference between it and the external environment is as high as nearly 300℃. The heat transferred between the liquid hydrogen tank and the environment causes the liquid hydrogen to evaporate. The density of liquid hydrogen is very low, about 71kg / m 3 The specific gravity of evaporation gas caused by environmental heat leakage is very high, which can easily lead to cargo loss and increased cabin pressure, and even endanger the navigation safety of the ship.

[0003] The latent heat of vaporization of liquid hydrogen under normal pressure is only 446 kJ / kg, while the sensible heat when heated to room temperature is about 3500 kJ / kg. In addition, the specific heat of hydrogen is extremely large, reaching 11-14 kJ / (kg.℃) in different temperature ranges, which is much higher than other substances in nature. Hydrogen can absorb a large amount of heat energy when it is heated. Its density under low temperature conditions is about 15 times that at room temperature. The special thermophysical properties of hydrogen and the changes in thermophysical properties with large temperature differences highlight that hydrogen evaporated gas contains huge usable cold energy. In the prior art, the main patent direction for the treatment of liquid hydrogen evaporated gas is the field of liquid hydrogen evaporated gas reliquefaction, but the equipment for liquefaction of liquid hydrogen evaporated gas is expensive, consumes huge energy, and wastes the huge cold energy contained in hydrogen evaporated gas.

[0004] The principle usually adopted for liquefying boil-off gas in ship's LNG tank or liquid ammonia tank is that the boil-off gas is first pressurized by a compressor, then cooled, and finally liquefied. This process utilizes the principle that the boiling point of the medium is higher under high pressure and the boil-off gas is easier to be cooled and liquefied, that is, the boil-off gas is further cooled and liquefied on the outlet side of the compressor.

[0005] Based on the above, if the huge cold energy contained in liquid hydrogen boil-off gas can be applied to the liquefaction of LNG or liquid ammonia boil-off gas, it can not only realize the effective utilization of the cold energy of hydrogen boil-off gas, but also greatly reduce the energy consumption of the cooling and liquefaction process of LNG or liquid ammonia boil-off gas. Summary of the invention

[0006] The object of the present invention is to realize the effective utilization of the cooling energy of hydrogen boil-off gas. Therefore, the present application provides a device for liquefying boil-off gas of LNG tanks and liquid ammonia tanks by utilizing the cooling energy of liquid hydrogen in ships.

[0007] In order to achieve the above invention objectives, this application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a device for liquefying boil-off gas from LNG tanks and liquid ammonia tanks using cold energy from liquid hydrogen in a ship, wherein the device is arranged based on the liquid hydrogen tank and LNG tank / liquid ammonia tank of the ship, and comprises a cold box heat exchanger, wherein the liquid hydrogen tank and the LNG tank / liquid ammonia tank are both connected to the cold box heat exchanger;

[0009] A liquid hydrogen boil-off gas flow passage is provided between the cold box heat exchanger and the liquid hydrogen tank, and the liquid hydrogen boil-off gas flows from the liquid hydrogen tank into the cold box heat exchanger through the passage;

[0010] An LNG / liquid ammonia vapor flow passage is provided between the cold box heat exchanger and the LNG tank / liquid ammonia tank, and the LNG / liquid ammonia vapor flows from the LNG tank / liquid ammonia tank into the cold box heat exchanger through the passage;

[0011] An LNG / liquid ammonia flow passage is also provided between the cold box heat exchanger and the LNG tank / liquid ammonia tank, and the LNG / liquid ammonia flows from the LNG tank / liquid ammonia tank into the cold box heat exchanger through the passage.

[0012] Furthermore, two reflux passages are arranged between the cold box heat exchanger and the LNG tank / liquid ammonia tank. One of the reflux passages is used to reflux the supercooled LNG / liquid ammonia formed by cooling the LNG / liquid ammonia in the cold box heat exchanger into the LNG tank / liquid ammonia tank, and the other reflux passage is provided with a condensate collecting tank. The excess evaporation gas after gas-liquid separation in the condensate collecting tank is supplied for use, and the liquefied condensate is refluxed into the LNG tank / liquid ammonia tank.

[0013] Furthermore, a gas-blocking and liquid-passing device is also provided on the passage between the condensate collecting tank and the LNG tank / liquid ammonia tank.

[0014] Furthermore, the condensate collection tank is located higher than the LNG tank / liquid ammonia tank, so that the liquefied condensate can flow back into the LNG tank / liquid ammonia tank only by relying on liquid gravity.

[0015] Furthermore, the LNG tank / liquid ammonia tank includes an inner wall of the LNG tank / liquid ammonia tank and an insulation layer of the LNG tank / liquid ammonia tank, the insulation layer of the LNG tank / liquid ammonia tank is vacuum insulation or insulation coating material, and an LNG pump / liquid ammonia pump is also provided in the LNG tank / liquid ammonia tank for pumping the LNG liquid / liquid ammonia in the LNG tank / liquid ammonia tank into the cold box heat exchanger.

[0016] Furthermore, two or more groups of cooling coils are arranged outside the liquid hydrogen tank, the inlet of the cooling coil is connected to the liquid hydrogen tank, and the outlet of the cooling coil is connected to the cold box heat exchanger; hydrogen evaporated gas enters the cooling coil from the liquid hydrogen tank to cool the liquid hydrogen tank, and then flows into the cold box heat exchanger from the outlet of the cooling coil.

[0017] Furthermore, a plurality 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.

[0018] Furthermore, the liquid hydrogen tank comprises 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 is in a vacuum insulation form, and an insulating coating material is arranged on the outside of the outer wall of the liquid hydrogen tank.

[0019] Furthermore, it also includes a heater and a gas compressor. The heater can heat liquid hydrogen vapor, LNG or liquid ammonia vapor, and a mixture of the two to room temperature; the compressor can pressurize room-temperature hydrogen, LNG or liquid ammonia vapor, and a mixture of the two for use by hydrogen or LNG or liquid ammonia vapor users, and also extract hydrogen and LNG or liquid ammonia vapor to exchange heat at the inlet side of the compressor to liquefy and condense the LNG or liquid ammonia vapor.

[0020] In a second aspect, the present application discloses a working method of the device described in the first aspect, including the following two working states:

[0021] Working state 1: When only hydrogen is used as ship fuel, hydrogen boil-off gas is used to reduce the evaporation rate of the liquid hydrogen tank. When the hydrogen boil-off gas cooling energy is sufficient, hydrogen boil-off gas is directly used as fuel;

[0022] Working state two: When LNG or ammonia mixed with hydrogen is used as fuel, liquid hydrogen evaporation gas cooling can be used to liquefy LNG or liquid ammonia evaporation gas. When the liquid hydrogen evaporation gas cooling energy is surplus, the hydrogen evaporation gas is used to reduce the evaporation rate of the liquid hydrogen tank.

[0023] Compared with the prior art, the device of the present invention has the following beneficial effects:

[0024] (1) Make full use of the ship's liquid hydrogen evaporation gas cooling energy, by using the evaporation gas generated during the ship's transportation of liquid hydrogen to condense the evaporation gas in the LNG tank or liquid ammonia tank, or directly cool the LNG or liquid ammonia to form a supercooled liquid and then return it to the tank for spraying and reducing the pressure, or keep the liquid hydrogen tank cold to reduce the evaporation rate of the liquid hydrogen tank.

[0025] (2) The same type of compressor can be used to extract hydrogen boil-off gas and LNG or liquid ammonia boil-off gas, avoiding the need to equip two independent hydrogen compressors and LNG or liquid ammonia boil-off gas compressors. At the same time, hydrogen fuel and LNG fuel can be mixed in a certain proportion and then the mixed gas can be extracted 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.

[0026] (3) The liquefaction and condensation of the boil-off gas in the low-pressure LNG tank or liquid ammonia tank is realized on the compressor inlet side. The traditional boil-off gas liquefaction process includes the steps of pressurization, cooling, and liquefaction on the compressor outlet side. In comparison, the cold energy utilization efficiency of the present invention is much higher, the equipment configuration is also simplified, and there is no need for a large number of cooling sources to cool the high-temperature gas generated by the compressor compression. At the same time, a condensate collection tank higher than the LNG or liquid ammonia tank is set up, so that the condensate can flow back to the LNG or liquid ammonia tank only by gravity, and the boil-off gas that is not liquefied or cannot be liquefied is separated by gas and liquid in the condensate collection tank and further transported from the compressor inlet to the outside as fuel. The boil-off gas processing flow rate is maximized, that is, the boil-off gas reliquefaction and the boil-off gas transmission as ship fuel are processed simultaneously.

[0027] (4) For the liquid hydrogen tank with vacuum interlayer, the cooling coil is surrounded by the metal outer wall of the vacuum liquid hydrogen tank, and the low-temperature liquid hydrogen evaporation gas is used to reduce the temperature of the metal outer wall of the liquid hydrogen tank, thereby reducing the temperature difference between the inner wall and the outer wall of the liquid hydrogen tank, greatly reducing the heat leakage from the external environment, and reducing the evaporation rate of liquid hydrogen cargo and cargo loss. Compared with the method of reducing the evaporation rate of the liquid hydrogen tank in the prior art, the device of the present invention does not need to use other cryogenic working fluids such as liquid nitrogen or a special hydrogen refrigeration system, and can make full use of the cold energy of the ship's cryogenic fuel. The implementation method is simple and the implementation cost is low. By dividing the evaporation gas cooling coil into an upper cooling coil and a lower cooling coil, the cooling coil is close to the metal outer wall of the vacuum liquid hydrogen tank, and the good thermal conductivity of the metal outer wall of the liquid hydrogen tank is used. A small number of cooling coils are used to cool the entire metal outer wall to form a complete low-temperature layer of the metal outer wall of the liquid hydrogen tank. When the cold energy is insufficient, the lower cooling coil is given priority to supply air to ensure the cooling effect of the liquid hydrogen cargo at the bottom of the liquid hydrogen tank and reduce the generation of hydrogen evaporation gas.

[0028] (5) Through the use of the above measures, the evaporation rate of liquid hydrogen cargo in the liquid hydrogen tank of the ship can be effectively reduced, the compressor equipment cost can be reduced, the boil-off gas of the LNG tank or the liquid ammonia tank can be liquefied, and the LNG or liquid ammonia can be directly supercooled and returned to the tank for cooling, which can fully utilize the cooling energy of the hydrogen boil-off gas and save the heat energy required for the ship to heat the hydrogen boil-off gas, LNG or liquid ammonia, reduce the amount of cargo transportation loss caused by the use of hydrogen boil-off gas as fuel, greatly reduce the transportation cost and fuel cost of the ship, and reduce the energy consumption and equipment configuration of the LNG or liquid ammonia boil-off gas treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 : Schematic diagram of the device for liquefying boil-off gas from LNG tanks and liquid ammonia tanks using the cold energy of liquid hydrogen from a ship in this embodiment.

[0030] Description of the drawings: 1. Inner wall of liquid hydrogen tank; 2. Outer wall of liquid hydrogen tank; 3. Insulation coating material; 4. Upper cooling coil; 5. Lower cooling coil; 6. Hydrogen boil-off gas main valve; 7. Inlet control valve for lower hydrogen cooling coil; 8. Inlet control valve for upper hydrogen cooling coil; 9. Hydrogen boil-off gas main pipeline control valve; 10. Cooling coil outlet temperature sensor; 11. Boil-off gas main pipeline temperature sensor; 12. Hydrogen cooling coil outlet control valve; 13. Cold box heat exchanger; 14. Gas compressor; 15. Inner wall of LNG / liquid ammonia tank; 16. LNG / liquid ammonia tank Insulation layer; 17. LNG / liquid ammonia pump; 18. LNG / liquid ammonia evaporation gas main valve; 19. LNG / liquid ammonia reflux valve; 20. LNG / liquid ammonia liquid main valve; 21. LNG / liquid ammonia direct utilization control valve; 22. LNG / liquid ammonia condensate reflux valve; 23. Gas blocking liquid vent; 24. LNG / liquid ammonia condensate collection tank; 25. Hydrogen flow valve; 26. Natural gas / liquid ammonia flow valve; 27. Hydrogen flow meter; 28. Natural gas / ammonia flow meter; 29. ​​Heater; 30. LNG / liquid ammonia evaporation gas direct utilization control valve. DETAILED DESCRIPTION

[0031] The structure and effect of the present application are further described in detail below in conjunction with the embodiments. It is to be understood that the specific embodiments described herein are only used to explain the invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the invention rather than the entire structure are shown in the accompanying drawings.

[0032] Example

[0033] A device for liquefying boil-off gas from LNG tanks and liquid ammonia tanks using liquid hydrogen cooling energy from ships, referring to Figure 1 The device is arranged based on the liquid hydrogen tank and LNG tank or liquid ammonia tank of the ship. The liquid hydrogen tank is used to load liquid hydrogen cargo on the ship and use the hydrogen evaporated gas as ship fuel; the LNG tank is used to store or transport LNG and use LNG as ship fuel; the liquid ammonia tank is used to store or transport liquid ammonia and use liquid ammonia as ship fuel.

[0034] Reference Figure 1 The liquid hydrogen tank includes an inner wall 1 and an outer wall 2 of the liquid hydrogen tank. The outer wall 2 of the liquid hydrogen tank is made of a metal material that is resistant to low temperatures and has good thermal conductivity. The interlayer between the inner wall 1 and the outer wall 2 of the liquid hydrogen tank is insulated by vacuuming. If necessary, the vacuum interlayer can be filled with thermal insulation materials. An insulating coating material 3 is provided outside the liquid hydrogen tank. The insulating coating material 3 can be made of insulating materials such as polyurethane foam or polystyrene, and is coated on the outside of the outer wall 2 of the liquid hydrogen tank to enhance the thermal insulation performance of the liquid hydrogen tank.

[0035] Reference Figure 1A cooling coil is provided between the outer wall 2 of the liquid hydrogen tank and the insulation layer, and the cooling coil is arranged close to the outer wall 2 of the liquid hydrogen tank. In a feasible implementation, the cooling coil can be divided into two or more groups. In this embodiment, two groups are taken as an example for explanation, that is, the cooling coil includes an upper cooling coil 4 and a lower cooling coil 5, and the upper cooling coil 4 and the lower cooling coil 5 are arranged at the upper part and the lower part 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 covers the cooling coil and the outer wall 2 of the liquid hydrogen tank as a whole. It is worth noting that the cooling coil does not need to wrap around the entire liquid hydrogen tank. It only needs to cover the local 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 using the fast thermal conductivity of the metal of the outer wall 2 of the liquid hydrogen tank.

[0036] Reference Figure 1 At the inlet of the cooling coil, multiple control valves for hydrogen boil-off gas are arranged, 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. In addition, in order to realize the direct supply of hydrogen boil-off gas, a hydrogen boil-off gas main pipeline control valve 9 is also arranged to be directly connected to the hydrogen boil-off gas main valve 6.

[0037] Reference Figure 1 A temperature sensor 10 is also connected to the outlet of the cooling coil to monitor the outlet temperature of the cooling coil, so as to achieve the purpose of adjusting the control valve group through temperature changes. The temperature sensor 10 is connected to the cooling coil outlet control valve 12, and the cooling coil outlet control valve 12 adjusts the flow rate of each cooling group according to the outlet temperature sensor 10 to improve the cooling effect.

[0038] Therefore, the liquid hydrogen boil-off gas has at least the following passages:

[0039] Path 1: Liquid hydrogen boil-off gas from the liquid hydrogen tank sequentially passes through the hydrogen boil-off gas main valve 6 and the hydrogen lower cooling coil inlet control valve 7 to enter the lower cooling coil 5, then flows out from the outlet of the lower cooling coil 5, and finally sequentially passes through the temperature sensor 10 and the cooling coil outlet control valve 12 before being supplied for use;

[0040] Path 2: Liquid hydrogen boil-off gas enters the upper cooling coil 4 from the liquid hydrogen tank through the hydrogen boil-off gas main valve 6 and the hydrogen upper cooling coil inlet control valve 8 in sequence, then flows out from the outlet of the upper cooling coil 4, and finally passes through the temperature sensor 10 and the cooling coil outlet control valve 12 in sequence before being supplied for use;

[0041] Passage 3: Liquid hydrogen boil-off gas is supplied from the liquid hydrogen tank through the hydrogen boil-off gas main valve 6 and the hydrogen boil-off gas main pipeline control valve 9 in sequence.

[0042] Reference Figure 1After the liquid hydrogen boil-off gas passes through any of the above paths, it passes through the boil-off gas main pipeline temperature sensor 11 and enters the cold box heat exchanger 13 for heat exchange.

[0043] 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 a vacuum insulation or an insulation coating material. A plurality of control valves for LNG are also provided at the inlet of the LNG tank, including an LNG evaporation gas main valve 18 and an LNG liquid main valve 20, which are used to control the opening and closing of the LNG supply. The LNG tank is also provided with an LNG pump 17, which is connected to the LNG liquid main valve 20.

[0044] Therefore, LNG has at least the following pathways:

[0045] Passage 1: LNG boil-off gas flows out of the LNG tank and passes through the LNG boil-off gas main valve 18 before entering the cold box heat exchanger 13 for heat exchange;

[0046] Passage 2: After the LNG liquid is pumped out from the LNG tank by the LNG pump 17, it passes through the LNG liquid main valve 20 and enters the cold box heat exchanger 13 for heat exchange (an LNG direct utilization control valve 21 is also provided on this passage to directly supply LNG for use).

[0047] Reference Figure 1 A control valve for LNG reflux is also provided at the inlet of the LNG tank, including an LNG reflux valve 19, which is provided on the reflux path between the cold box heat exchanger 13 and the LNG tank. The cold box heat exchanger 13 is connected to an LNG condensate collection tank 24, and the LNG condensate collection tank 24 is connected to the LNG tank, and a gas-liquid blocking device 23 and an LNG condensate reflux valve 22 are provided on the communication path between the two.

[0048] Therefore, LNG has at least the following reflux paths:

[0049] Passage 1: After heat exchange in the cold box heat exchanger 13, the LNG is cooled to form supercooled LNG, which then flows out and flows back into the LNG tank through the LNG return valve 19;

[0050] Path 2: LNG evaporated gas exchanges heat in the cold box heat exchanger 13, and the LNG evaporated gas condensate formed by liquefaction after heat exchange enters the condensate collection tank 24. The excess evaporated gas after gas-liquid separation is supplied for use. The liquefied condensate passes through the gas-liquid blocking device 23 and then flows back to the LNG tank through the LNG condensate reflux valve 22 (the position of the condensate collection tank 24 is higher than the LNG tank, so that the liquid can flow back to the LNG tank only by gravity).

[0051] Reference Figure 1 The output end of the cold box heat exchanger 13 is connected to the heater 29 and the gas compressor 14 in sequence.

[0052] A hydrogen flow meter 27 and a hydrogen flow valve 25 are also provided on the passage. In addition, the excess evaporation gas after gas-liquid separation in the LNG condensate collection tank 24 can be directly supplied for use after passing through the natural gas flow meter 28 and the LNG evaporation gas direct utilization control valve 30 in sequence, or can be mixed with the hydrogen evaporation gas output by the cold box heat exchanger 13 after passing through the natural gas flow meter 28 and the natural gas flow valve 26 in sequence and then flow into the heater 29.

[0053] It is worth noting that, although the above description is only based on the LNG tank as an example, it should be understood that replacing the above LNG tank with a liquid ammonia tank can also achieve the same function and have the same liquid ammonia / liquid ammonia evaporation gas flow path. That is, the LNG tank inner wall 15, the LNG tank insulation layer 16, the LNG pump 17, the LNG evaporation gas main valve 18, the LNG reflux valve 19, the LNG liquid main valve 20, the LNG direct utilization control valve 21, the LNG condensate reflux valve 22, the LNG condensate collection tank 24, the natural gas flow valve 26, the natural gas flow meter 28, and the LNG evaporation gas direct utilization control valve 30 can all be correspondingly configured as liquid ammonia tank related structures and control valves.

[0054] In addition, the heater 29 mentioned above can heat the liquid hydrogen boil-off gas, LNG or (or liquid ammonia) boil-off gas, and the mixture of the two to room temperature, so that it can be used as fuel by subsequent gas users. The compressor 14 mentioned above can pressurize the normal temperature hydrogen or natural gas (or ammonia), or the mixture of the two, for use by hydrogen or natural gas (or ammonia) users. At the same time, hydrogen and natural gas (or ammonia) are also extracted, so that the two are heat exchanged at the inlet side of the compressor 14, so that the natural gas (or ammonia) is liquefied and condensed.

[0055] In summary, when a ship uses liquid hydrogen boil-off gas as fuel, regardless of whether natural gas or ammonia is used to mix hydrogen, the present invention can utilize liquid hydrogen boil-off gas cooling energy, and there are the following working states:

[0056] Working state 1: When only hydrogen is used as ship fuel, the device control method is: open the hydrogen lower cooling coil inlet control valve 7 and the hydrogen upper cooling coil inlet control valve 8 corresponding to the upper cooling coil 4 and the lower cooling coil 5 of hydrogen evaporation gas. The lower cooling coil inlet and outlet control valve 7 is opened first to ensure that the lower outer wall of the liquid hydrogen tank is cooled first; if the lower cooling coil outlet temperature sensor 10 detects a low temperature, the upper cooling coil inlet and outlet control valve 8 can be opened to further cool the upper outer wall of the liquid hydrogen tank; when the hydrogen evaporation gas cooling energy is sufficient, open the hydrogen evaporation gas main pipeline control valve 9 to directly use the hydrogen evaporation gas as fuel.

[0057] Working state two: When natural gas or ammonia mixed with hydrogen is used as fuel, the device control method is: liquid hydrogen evaporation gas cooling energy is preferentially used for the liquefaction of LNG or liquid ammonia evaporation gas. When the liquid hydrogen evaporation gas cooling energy is surplus, it is transported to the cooling coil of the liquid hydrogen tank to reduce the evaporation rate of the liquid hydrogen tank.

[0058] The device for liquefying LNG (or liquid ammonia) boil-off gas by liquid hydrogen boil-off gas cooling is specifically as follows (the following description is made taking LNG boil-off gas as an example):

[0059] When the ship needs to use the boil-off gas of LNG as fuel, the LNG boil-off gas main valve 18 is opened, and the liquid hydrogen boil-off gas and LNG boil-off gas are sucked at the same time through the suction function of the compressor 14. The hydrogen boil-off gas flow rate and the LNG boil-off gas flow rate are adjusted through the hydrogen flow meter 27 and the natural gas flow meter 28, the hydrogen flow valve 25 and the natural gas flow valve 26, so as to realize the liquid hydrogen cold energy required for liquefying the LNG boil-off gas and realize the adjustment of the hydrogen blending ratio of the LNG boil-off gas. The liquid hydrogen boil-off gas and the LNG boil-off gas with adjusted ratios are heat exchanged in the cold box heat exchanger 13, and the liquefied LNG boil-off gas condensate formed after the heat exchange enters the condensate collection tank 24. After the gas-liquid separation, the excess boil-off gas is transported to the inlet of the compressor 14 to mix with the hydrogen, and the liquefied condensate flows back to the LNG tank through the gas blocking liquid vent 23. Preferably, the condensate collection tank 24 is located higher than the LNG tank, so as to realize the return to the LNG tank only by the gravity of the liquid.

[0060] When a ship needs to directly use LNG (or liquid ammonia) as liquid fuel (the following uses LNG boil-off gas as an example):

[0061] Liquid is extracted by LNG pump 17, and LNG liquid main valve 20 is opened. LNG liquid passes through cold box heat exchanger 13, and is cooled by liquid hydrogen evaporation gas to form supercooled liquid, which is sprayed back into the cabin to cool down and reduce the pressure of LNG tank. Supercooled liquid directly liquefies evaporation gas in the cabin. When the cooling energy of liquid hydrogen evaporation gas is low, LNG direct utilization control valve 21 can be opened to reduce the flow of LNG liquid, thereby ensuring the cooling range of supercooled liquid returning to the cabin. Preferably, the cooling range of LNG liquid is not less than 5°C, and the best effect is 10-15°C, but it does not need to exceed 20°C.

[0062] For some users who can use low-pressure hydrogen or natural gas as fuel, such as boilers, gas combustion devices, fuel cells, etc., they can directly provide LNG or liquid ammonia evaporated gas as fuel through the control valve 30 without using a compressor for pressurization.

[0063] 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 modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A device for liquefying boil-off gas from LNG tanks and liquid ammonia tanks using liquid hydrogen cooling energy of a ship, the device being arranged based on the liquid hydrogen tank and LNG tank / liquid ammonia tank of the ship, characterized in that: It includes a cold box heat exchanger, and the liquid hydrogen tank and the LNG tank / liquid ammonia tank are both connected to the cold box heat exchanger; A liquid hydrogen boil-off gas flow passage is provided between the cold box heat exchanger and the liquid hydrogen tank, and the liquid hydrogen boil-off gas flows from the liquid hydrogen tank into the cold box heat exchanger through the passage; An LNG / liquid ammonia vapor flow passage is provided between the cold box heat exchanger and the LNG tank / liquid ammonia tank, and the LNG / liquid ammonia vapor flows from the LNG tank / liquid ammonia tank into the cold box heat exchanger through the passage; An LNG / liquid ammonia flow passage is also provided between the cold box heat exchanger and the LNG tank / liquid ammonia tank, and the LNG / liquid ammonia flows from the LNG tank / liquid ammonia tank into the cold box heat exchanger through the passage.

2. The device according to claim 1, characterized in that Two reflux paths are also arranged between the cold box heat exchanger and the LNG tank / liquid ammonia tank. One of the reflux paths is used to return the supercooled LNG / liquid ammonia formed by cooling the LNG / liquid ammonia after heat exchange in the cold box heat exchanger to the LNG tank / liquid ammonia tank. The other reflux path is provided with a condensate collecting tank. The excess evaporation gas after gas-liquid separation in the condensate collecting tank is supplied for use, and the liquefied condensate is returned to the LNG tank / liquid ammonia tank.

3. The device according to claim 2, characterized in that A gas-blocking and liquid-passing device is also provided on the passage between the condensate collecting tank and the LNG tank / liquid ammonia tank.

4. The device according to claim 2, characterized in that The condensate collection tank is located higher than the LNG tank / liquid ammonia tank, so that the liquefied condensate can flow back into the LNG tank / liquid ammonia tank only by relying on liquid gravity.

5. The device according to claim 1, characterized in that The LNG tank / liquid ammonia tank includes an inner wall of the LNG tank / liquid ammonia tank and an insulation layer of the LNG tank / liquid ammonia tank. The insulation layer of the LNG tank / liquid ammonia tank is vacuum insulation or insulation coating material. An LNG pump / liquid ammonia pump is also provided in the LNG tank / liquid ammonia tank for pumping the LNG liquid / liquid ammonia in the LNG tank / liquid ammonia tank into the cold box heat exchanger.

6. The device according to claim 1, characterized in that Two or more groups of cooling coils are arranged outside the liquid hydrogen cabin, the inlet of the cooling coil is connected to the liquid hydrogen cabin, and the outlet of the cooling coil is connected to the cold box heat exchanger; hydrogen evaporated gas enters the cooling coil from the liquid hydrogen cabin to cool the liquid hydrogen cabin, and then flows into the cold box heat exchanger from the outlet of the cooling coil.

7. The device according to claim 6, characterized in that A plurality 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.

8. The device according to claim 1, characterized in that The liquid hydrogen tank comprises 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 is in a vacuum insulation form. An insulating coating material is arranged on the outer side of the outer wall of the liquid hydrogen tank.

9. The device according to claim 1, characterized in that It also includes a heater and a gas compressor. The heater can heat liquid hydrogen evaporated gas, LNG or liquid ammonia evaporated gas, and a mixture of the two to room temperature; the compressor can pressurize room-temperature hydrogen, LNG or liquid ammonia evaporated gas, and a mixture of the two for use by hydrogen or LNG or liquid ammonia evaporated gas users, and also extract hydrogen and LNG or liquid ammonia evaporated gas, so that the two exchange heat at the inlet side of the compressor, so that the LNG or liquid ammonia evaporated gas is liquefied and condensed.

10. The working method of the device according to any one of claims 1 to 9, characterized in that: There are two working states: Working state 1: When only hydrogen is used as ship fuel, hydrogen boil-off gas is used to reduce the evaporation rate of the liquid hydrogen tank. When the hydrogen boil-off gas cooling energy is sufficient, hydrogen boil-off gas is directly used as fuel; Working state two: When LNG or ammonia mixed with hydrogen is used as fuel, liquid hydrogen evaporation gas cooling can be used to liquefy LNG or liquid ammonia evaporation gas. When the liquid hydrogen evaporation gas cooling energy is surplus, the hydrogen evaporation gas is used to reduce the evaporation rate of the liquid hydrogen tank.

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