Liquid nitrogen cold insulation system for no-load sailing of liquid hydrogen ship

Abstract

The invention belongs to the technical field of ships, and provides a liquid hydrogen ship no-load sailing cold insulation system utilizing liquid nitrogen, which comprises a purification system, a compressor, a seawater heat exchanger, an air separation system, a liquid nitrogen tank, a liquid nitrogen pump, a liquid nitrogen interface, a liquid hydrogen ship interface, a liquid cargo tank, a liquid hydrogen interface, a liquid hydrogen tank, a liquid hydrogen pump and a booster pump. Cold energy released by liquid hydrogen is utilized in the liquid nitrogen preparation process, and waste of liquid hydrogen cold energy is avoided; meanwhile, in view of the obvious defects existing in the two precooling modes of spraying precooling and remaining cargo precooling, when the liquid hydrogen ship sails in a no-load mode, liquid nitrogen is used for conducting cold insulation on the liquid cargo tank of the ship, the liquid cargo tank is kept in a low-temperature state all the time, and precooling treatment before loading is achieved. Compared with spraying pre-cooling, the pre-cooling time before loading is saved, and the freight cycle is shortened; and compared with reserved goods pre-cooling, the liquid hydrogen transportation amount of a single voyage is greatly increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of ships, and particularly relates to a system for using liquid nitrogen for cold insulation during the empty voyage of a liquid hydrogen ship. Background Art

[0003] Since the temperature of liquid hydrogen is extremely low under normal pressure (about -253°C), before filling liquid hydrogen at the filling port, the liquid cargo hold of the ship needs to be "pre-cooled" so that the temperature inside the liquid cargo hold remains around -180°C to -200°C. This is because if liquid hydrogen is directly filled into the liquid cargo hold of the ship, large thermal stresses will be generated on the metal cabin wall, which will in turn cause damage to the cabin body. There are mainly two methods for pre-cooling the liquid cargo hold of a liquid hydrogen ship: spray pre-cooling and retained cargo pre-cooling.

[0004] The method of spray pre-cooling means that when the liquid hydrogen ship berths at the filling port, before filling liquid hydrogen into the liquid cargo hold of the ship, a small amount of liquid hydrogen is continuously sprayed into the liquid cargo hold first to gradually lower the temperature inside the liquid cargo hold. When the temperature difference between the temperature inside the liquid cargo hold of the ship and the temperature of liquid hydrogen (-253°C) is small, the spraying process ends, and then liquid hydrogen is filled into the liquid cargo hold. Although the method of spray pre-cooling can effectively reduce the temperature inside the liquid cargo hold, since the temperature inside the cargo hold may be close to room temperature or only dozens of degrees below zero before spraying, it takes a long time, possibly more than 4 days. This makes the shipping cycle of the ship longer, and the longer the ship stays at the port will also generate higher costs. The method of retained cargo pre-cooling means that when the liquid hydrogen ship berths at the receiving port for unloading, most of the liquid hydrogen in the liquid cargo hold is unloaded to the receiving port, and a small amount of liquid hydrogen is left in each liquid cargo hold of the ship. The purpose is to use the cold energy of the liquid hydrogen left in the liquid cargo hold to keep the temperature inside the liquid cargo hold at a low temperature during the empty voyage of the liquid hydrogen ship to the filling port. In this way, when berthing at the liquid hydrogen filling port, liquid hydrogen can be directly filled into the liquid cargo hold of the ship. Although the method of retained cargo pre-cooling reduces the transportation time of liquid hydrogen, this method will greatly reduce the transportation volume of liquid hydrogen per voyage due to the retained cargo.

[0005] Liquid nitrogen has a temperature of approximately -196°C at atmospheric pressure, and after vaporizing, it directly turns into nitrogen gas. Nitrogen is an inert gas and does not react easily with most substances, making it an ideal pre-cooling medium. Liquid nitrogen is typically produced using cryogenic air separation, a process that involves air first passing through a purification system to remove impurities and other substances. The air is then pressurized and cooled. The cooled air then enters the air separation system, where it undergoes compression, cooling, expansion, distillation, and condensation, before liquid nitrogen is separated. The primary cost of producing liquid nitrogen using this cryogenic air separation process is the high power consumption associated with refrigeration due to the large amount of cold energy required. Because liquid hydrogen ships transport large quantities of liquid hydrogen, after unloading at the receiving port, the liquid hydrogen is typically regasified and transported via pipelines to factories or users. This regasification process releases a significant amount of cold energy, which, if fully utilized in the production of liquid nitrogen, would generate considerable value.

[0006] Based on this, if a system can be designed to use liquid nitrogen for cold preservation when a liquid hydrogen ship is sailing empty, the cold energy released by liquid hydrogen can be used to produce liquid nitrogen, and then a certain amount of liquid nitrogen can be injected into the liquid cargo tank of the ship. When the ship is sailing empty, the cold energy of the liquid nitrogen can be used to keep the liquid cargo tank cold, so that the liquid cargo tank is always in a low temperature state, and pre-cooling of the ship before loading is achieved. This not only makes rational use of the cold energy of liquid hydrogen, but also increases the transportation volume of liquid hydrogen, while greatly reducing the freight cycle, which is of very high value. Summary of the Invention

[0007] In response to the above-mentioned problems, the present invention proposes a system for using liquid nitrogen to keep a liquid hydrogen ship cold when sailing empty. The system includes: a purification system, a compressor, a seawater heat exchanger, an air separation system, a liquid nitrogen tank, a liquid nitrogen pump, a liquid nitrogen interface, a liquid hydrogen ship interface, a liquid cargo tank, a liquid hydrogen interface, a liquid hydrogen tank, a liquid hydrogen pump, and a booster pump.

[0008] The purification system, compressor, seawater heat exchanger, air separation system, and liquid nitrogen tank are connected in sequence through pipelines; the liquid nitrogen tank is located at a receiving port on land; the liquid nitrogen pump is placed in the liquid nitrogen tank and connected to the liquid nitrogen interface through a pipeline; the liquid nitrogen interface is located at the receiving port; the liquid hydrogen ship interface is located on the liquid hydrogen ship and connected to the liquid cargo tank through a pipeline;

[0009] The liquid hydrogen interface is located at the receiving port and is connected to the liquid hydrogen tank through a pipeline; the liquid hydrogen tank is located at the receiving port on land and is used to store liquid hydrogen unloaded by the liquid hydrogen ship; the liquid hydrogen pump is placed in the liquid hydrogen tank and is connected to the booster pump and the air separation system in sequence through a pipeline.

[0010] Furthermore, the present invention produces liquid nitrogen through a cryogenic air separation method. The working principle is: utilizing the different boiling points of various components in the air under the same pressure, nitrogen in the air is separated by distillation, and then the cold energy released by the gasification of liquid hydrogen is used to produce liquid nitrogen.

[0011] When the liquid hydrogen ship docks at the receiving port, the liquid hydrogen interface is first connected to the liquid hydrogen ship interface, and all the liquid hydrogen in the ship's cargo tank is unloaded into the liquid hydrogen tank at the receiving port. Then, liquid nitrogen is produced at the receiving port using the cryogenic air separation method: First, the air passes through the purification system to remove impurities and moisture, then enters the compressor for pressurization. The pressurized air enters the seawater heat exchanger through a pipeline for cooling, and then enters the air separation system. At the same time, the liquid hydrogen pump transfers the liquid hydrogen in the liquid hydrogen tank to the booster pump. After the boosting effect of the booster pump, the liquid hydrogen enters the air separation system, continuously providing cold energy for the production of liquid nitrogen in the air separation system. In the air separation system, liquid nitrogen is separated from the air after a series of processes such as compression, cooling, expansion, distillation, and condensation. Finally, the liquid nitrogen is stored in the liquid nitrogen tank at the receiving port. At the same time, the liquid hydrogen releases cold energy in the air separation system and heats up. The hydrogen finally formed is transported to the factory or user through a pipeline.

[0012] Since the liquid nitrogen produced by the above process is stored in the liquid nitrogen tank at the receiving port, when the next liquid hydrogen ship berths at the receiving port, after unloading the liquid hydrogen in the liquid cargo tank into the liquid hydrogen tank, liquid nitrogen can be immediately added to the liquid hydrogen tank. After the liquid hydrogen ship unloads all the liquid hydrogen into the liquid hydrogen tank at the receiving port through the original cargo pump, liquid nitrogen is immediately added to the liquid hydrogen ship. First, the liquid nitrogen interface is connected to the liquid hydrogen ship interface, and then the liquid nitrogen pump in the liquid nitrogen tank transfers a certain amount of liquid nitrogen to each liquid cargo tank. In the process of the ship sailing empty to the refueling port, the liquid nitrogen relies on its own cold energy to keep the liquid cargo tank at a low temperature at all times, which has a cooling effect on the liquid cargo tank and realizes pre-cooling of the liquid cargo tank before loading. When the liquid hydrogen ship berths at the refueling port, the liquid nitrogen in the liquid cargo tank is first unloaded to the receiving port on land, and then the liquid hydrogen from the refueling port is directly added to the ship's cargo tank.

[0013] Beneficial effects of the present invention:

[0014] 1. This invention uses liquid nitrogen to keep the liquid cargo tanks cool when the liquid hydrogen carrier is sailing empty, keeping them at a constant low temperature and achieving pre-cooling of the cargo tanks. Compared to "spray pre-cooling," this invention saves pre-cooling time and shortens the freight cycle; compared to "cargo pre-cooling," it significantly increases the liquid hydrogen transport volume per voyage.

[0015] 2. The present invention applies liquid hydrogen as a refrigerant to the process of producing nitrogen by cryogenic air separation, and utilizes the cold energy generated by the gasification of liquid hydrogen to produce liquid nitrogen. This not only rationally utilizes the cold energy of liquid hydrogen, but also achieves the effect of liquefying nitrogen with almost zero power consumption, thus having high value. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the flow chart for liquid nitrogen preparation and filling;

[0017] Figure 2 Flow chart for unloading liquid hydrogen from a liquid hydrogen ship;

[0018] In the attached figure: 1. Purification system; 2. Compressor; 3. Seawater heat exchanger; 4. Air separation system; 5. Liquid nitrogen tank; 6. Liquid nitrogen pump; 7. Liquid nitrogen interface; 8. Liquid hydrogen ship interface; 9. Liquid cargo tank; 10. Liquid hydrogen interface; 11. Liquid hydrogen tank; 12. Liquid hydrogen pump; 13. Booster pump. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0020] A system for using liquid nitrogen to keep a liquid hydrogen ship cold when sailing empty, such as Figure 1 、 Figure 2 As shown, the system includes a purification system 1, a compressor 2, a seawater heat exchanger 3, an air separation system 4, a liquid nitrogen tank 5, a liquid nitrogen pump 6, a liquid nitrogen interface 7, a liquid hydrogen ship interface 8, a liquid cargo tank 9, a liquid hydrogen interface 10, a liquid hydrogen tank 11, a liquid hydrogen pump 12, and a booster pump 13.

[0021] The purification system 1, compressor 2, seawater heat exchanger 3, air separation system 4, and liquid nitrogen tank 5 are connected in sequence through pipelines; the purification system 1 is used to remove impurities, moisture, etc. in the air; the compressor 2 is used to pressurize the air; the seawater heat exchanger 3 is used to cool the pressurized air; the air separation system 4 is used to produce liquid nitrogen; the liquid nitrogen tank 5 is located at a receiving port on land and is used to store separated liquid nitrogen; the liquid nitrogen pump 6 is placed in the liquid nitrogen tank 5 and is connected to the liquid nitrogen interface 7 through a pipeline; the liquid nitrogen interface 7 is located at the receiving port; the liquid hydrogen ship interface 8 is located on the liquid hydrogen ship and is connected to the liquid cargo tank 9 through a pipeline.

[0022] The liquid hydrogen interface 10 is located at the receiving port and is connected to the liquid hydrogen tank 11 via a pipeline. The liquid hydrogen tank 11 is located at the receiving port on land and is used to store liquid hydrogen unloaded from the liquid hydrogen ship. The liquid hydrogen pump 12 is placed in the liquid hydrogen tank 11 and is connected to the booster pump 13 and the air separation system 4 in sequence via pipelines. The liquid hydrogen pump 12 is used to transfer the liquid hydrogen in the liquid hydrogen tank 11 to the booster pump 13; the booster pump 13 realizes the pressurization of the liquid hydrogen.

[0023] Furthermore, the present invention produces liquid nitrogen through a cryogenic air separation method. The working principle is as follows: utilizing the different boiling points of various components in the air at the same pressure, the various components in the air are separated by distillation to separate nitrogen, and then the cold energy released by the gasification of liquid hydrogen is used to produce liquid nitrogen.

[0024] When the liquid hydrogen ship docks at the receiving port, first connect the liquid hydrogen ship interface 8 and the liquid hydrogen interface 10, unload all the liquid hydrogen in the liquid cargo tank 9 into the liquid hydrogen tank 11 at the receiving port, and then use the cryogenic air separation method to produce liquid nitrogen, and the cold energy of the liquid hydrogen is reasonably used in the production process of liquid nitrogen. The main process is as follows: first, air enters the purification system 1 to remove dust and mechanical impurities, and then enters the compressor 2 for pressurization. The pressurized air enters the seawater heat exchanger 3 through a pipeline for cooling, and then enters the air separation system 4 through inlet D; at the same time, the liquid hydrogen pump 12 transfers the liquid hydrogen in the liquid hydrogen tank 11 to the booster pump 13, and the liquid hydrogen is pressurized in the booster pump 13. The pressurized liquid hydrogen enters the air separation system 4 through inlet A, continuously providing cold energy for the production of liquid nitrogen in the air separation system 4; in the air separation system 4, liquid nitrogen is separated from the air after a series of processes such as compression, cooling, expansion, distillation, and condensation. Finally, the liquid nitrogen flowing out through outlet B is stored in the liquid nitrogen tank 5 at the receiving port. At the same time, the liquid hydrogen releases cold energy in the air separation system 4 and heats up. The hydrogen finally formed is transported to the factory or user through a pipeline through outlet C.

[0025] Since the liquid nitrogen produced by the above process is stored in the liquid nitrogen tank 5 at the receiving port, when the next liquid hydrogen ship docks at the receiving port, after unloading the liquid hydrogen in the liquid cargo tank 9 to the liquid hydrogen tank 11, liquid nitrogen can be immediately added to the liquid hydrogen tank. The specific process is as follows: first, connect the liquid hydrogen ship interface 8 and the liquid hydrogen interface 10, and unload all the liquid hydrogen in the liquid cargo tank 9 to the liquid hydrogen tank 11 at the receiving port through the ship's original cargo pump. After unloading, disconnect the liquid hydrogen ship interface 8 and the liquid hydrogen interface 10, and then connect the liquid nitrogen interface 7 and the liquid hydrogen ship interface 8. The liquid nitrogen pump 6 transfers 1000m from the liquid nitrogen tank 5 to each liquid cargo tank 9. 3 ~2000m 3 The amount of liquid nitrogen added depends on the size of the ship. Usually, 1000m3 of liquid nitrogen is added to each cargo tank 9. 3 ~2000m 3 Small ships usually fill 1000m 3 When the filling is completed, disconnect the liquid nitrogen interface 7 and the liquid hydrogen ship interface 8. In the process of the ship sailing empty to the filling port, the liquid nitrogen relies on its own cold energy to keep the liquid cargo tank 9 at a low temperature, which has a cooling effect on the liquid cargo tank 9 and realizes the pre-cooling treatment of the liquid cargo tank 9. When the liquid hydrogen ship docks at the filling port, most of the liquid nitrogen in the liquid cargo tank 9 has evaporated, and only a small amount of liquid nitrogen remains. After the liquid nitrogen is unloaded to the land receiving port, the temperature of the liquid cargo tank 9 is about -180℃~-200℃, which meets the filling conditions of liquid hydrogen. The liquid hydrogen is then filled into the ship's liquid cargo tank 9 at the filling port.

[0026] Since nitrogen is an inert gas with stable properties and is not easy to react with most substances, during the above-mentioned liquid nitrogen unloading process, even if the liquid nitrogen in the liquid cargo tank 9 cannot be completely unloaded, liquid hydrogen can be directly added to the liquid cargo tank 9 in this case.

[0027] Since the "spray pre-cooling" method used in the liquid hydrogen ship's cargo tank 9 will increase the ship's freight cycle, and the cost of long-term port calls is high, and the "cargo retention pre-cooling" method will reduce the transportation volume of liquid hydrogen, in view of the obvious shortcomings of the two pre-cooling methods, the present invention proposes to use liquid nitrogen to pre-cool the liquid hydrogen ship's cargo tank 9. That is, when the liquid hydrogen ship docks at the receiving port, the liquid hydrogen is first unloaded into the liquid hydrogen tank 11, and then a certain amount of liquid nitrogen is added to the liquid cargo tank 9. During the process of the ship sailing empty to the refueling port, the liquid nitrogen's own cold energy is used to pre-cool the liquid cargo tank 9, so that the liquid cargo tank 9 always maintains a low temperature state. The present invention can directly add liquid hydrogen to the liquid cargo tank 9 after the liquid hydrogen ship docks at the refueling port and unloads the liquid nitrogen. This not only increases the transportation volume of liquid hydrogen, but also saves the pre-cooling time before liquid hydrogen refueling, greatly reducing the freight cycle.

[0028] When a liquid hydrogen ship docks at a receiving port, the liquid hydrogen in cargo tank 9 must be unloaded into liquid hydrogen tanks 11 at the receiving port for storage. Due to the large volume of liquid hydrogen, it typically needs to be vaporized and transported via pipelines to factories or end users. This vaporization process releases a large amount of cold energy. The present invention rationally utilizes the cold energy released during the vaporization of liquid hydrogen, applying this cold energy to the production of liquid nitrogen using a cryogenic air separation method. This achieves near-zero-power liquefied nitrogen, avoiding waste of cold energy.

[0029] The foregoing is merely a preferred embodiment of the present invention. The specific embodiments described herein are intended solely to explain the present invention and are not intended to limit the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A system for using liquid nitrogen to keep a liquid hydrogen ship cool when sailing empty, characterized by: This system includes: Purification system (1), compressor (2), seawater heat exchanger (3), air separation system (4), liquid nitrogen tank (5), liquid nitrogen pump (6), liquid nitrogen interface (7), liquid hydrogen ship interface (8), liquid cargo tank (9), liquid hydrogen interface (10), liquid hydrogen tank (11), liquid hydrogen pump (12), booster pump (13); The purification system (1), the compressor (2), the seawater heat exchanger (3), the air separation system (4), and the liquid nitrogen tank (5) are sequentially connected through pipelines; the liquid hydrogen pump (12) is placed in the liquid hydrogen tank (11), and is sequentially connected to the booster pump (13) and the air separation system (4) through pipelines; the liquid nitrogen pump (6) is placed in the liquid nitrogen tank (5), and is connected to the liquid nitrogen interface (7) through pipelines; the liquid hydrogen interface (10) is located at the receiving port, and is connected to the liquid hydrogen tank (11) through pipelines; After the liquid hydrogen ship unloads all the liquid hydrogen in the liquid cargo tank (9) to the liquid hydrogen tank (11) at the receiving port, the liquid nitrogen interface (7) is connected to the liquid hydrogen ship interface (8), and liquid nitrogen is immediately added to the liquid hydrogen ship. When the ship is sailing empty, the cold energy of the liquid nitrogen is used to keep the liquid cargo tank (9) cold.

2. The system for using liquid nitrogen to keep a liquid hydrogen carrier cold during empty navigation according to claim 1, characterized in that: The liquid nitrogen interface (7) is located at the receiving port; the liquid hydrogen ship interface (8) is located on the liquid hydrogen ship and is connected to the liquid cargo tank (9) via a pipeline.

3. The system for using liquid nitrogen to keep a liquid hydrogen ship cold during empty navigation according to claim 1, characterized in that: The amount of liquid nitrogen filled in a single tank of the liquid cargo tank (9) is 1000 m 3 ~2000 m 3 .

4. The system for using liquid nitrogen to keep a liquid hydrogen carrier cold during empty navigation according to claim 1, characterized in that: The air separation system (4) is used to separate liquid nitrogen. The liquid nitrogen flowing out through the outlet B is stored in the liquid nitrogen tank (5) at the receiving port. At the same time, the liquid hydrogen releases cold energy in the air separation system (4) and heats up, eventually forming hydrogen gas and transporting it to the factory or user through the outlet C.

5. A system for using liquid nitrogen for cold insulation during the empty voyage of a liquid hydrogen ship according to claim 1, characterized in that: The liquid nitrogen tank (5) and the liquid hydrogen tank (11) are located at a receiving port on land.

6. The system for cryogenic preservation of liquid hydrogen ship in no-load navigation using liquid nitrogen according to claim 1, characterized in that: When the liquid hydrogen ship unloads liquid hydrogen at the receiving port, the liquid hydrogen ship interface (8) is connected to the liquid hydrogen interface (10).

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