Liquid hydrogen and LNG (Liquefied Natural Gas) combined transportation cargo hold system of ammonia-powered ship

Abstract

The invention belongs to the technical field of ships, and provides an ammonia-powered ship liquid hydrogen and LNG combined transportation cargo hold system. Comprising a hydrogen liquid cargo tank, an LNG liquid cargo tank, an ammonia fuel tank, a lightering pump, a hydrogen pressure sensor, an LNG pressure sensor, a hydrogen fuel battery pack, an LNG power generation unit, an ammonia fuel power generation unit, a load control unit, a ship power grid, a propulsion motor, a pressure control unit, a hydrogen evaporation gas valve, an LNG evaporation gas valve, an ammonia fuel valve, an external control signal and a ballast tank. The hydrogen liquid cargo tank, the LNG liquid cargo tank and the ammonia fuel tank are combined into a hierarchical wrapping structure from inside to outside, the cold energy advantages of liquid hydrogen, LNG and ammonia are integrated, the temperature gradient which is gradually reduced from outside to inside is formed, the problem that the generation amount of liquid hydrogen BOG and LNG boil-off gas is too large is effectively solved, a small amount of boil-off gas is converted into electric energy to be used for ship propulsion, and the ship propulsion efficiency is improved. Zero emission of evaporated gas and efficient utilization of energy are realized. In addition, by means of combined transportation of liquid hydrogen and LNG, the stability of the ship is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ships, and in particular relates to a liquid hydrogen and LNG combined transport cargo tank system for an ammonia powered ship. Background Art

[0002] As the International Maritime Organization (IMO) sets increasingly higher standards for carbon emissions from ships, more and more commercial ships are turning to clean energy, including ammonia, LNG, liquid hydrogen, etc.

[0003] Due to the high price of hydrogen, ships generally do not actively use hydrogen as fuel, but prefer to use cheaper ammonia or LNG. Since ammonia combustion mainly produces nitrogen and water, it has almost zero carbon emissions and its environmental performance far exceeds that of traditional fuel ships. Therefore, more and more ships choose ammonia fuel as a power source.

[0004] As an important clean energy, hydrogen has attracted much attention in the field of international trade and transportation. Ships are important carriers for transporting hydrogen. In order to reduce the volume of hydrogen occupied by ships, ships are usually transported in liquid form. The transport ships used to transport liquid hydrogen are called liquid hydrogen transport ships. Liquid hydrogen transport ships are facing a series of thorny problems in their current development. Liquid hydrogen storage requires an extremely low temperature environment of about -253°C, which is nearly 300°C different from the natural environment temperature, resulting in the inevitable generation of a large amount of liquid hydrogen BOG during transportation. Liquid hydrogen BOG is usually treated by reliquefaction or direct combustion. Reliquefaction will cause a lot of refrigeration power consumption and increase operating costs. Direct combustion usually refers to sending liquid hydrogen BOG to hydrogen fuel cells or ship power units. Hydrogen fuel cells have a high energy conversion rate, but they cannot completely process all BOG. ​​If the remaining BOG is sent to the ship power unit for combustion, the energy utilization rate is low, which will cause energy waste. At the same time, liquid hydrogen transport ships are moving towards large-scale development in order to increase transportation volume. For example, a ship designed by a British research institute has a capacity of 280,000m 3 The liquid hydrogen transport ship is 370m long and 75m wide, with an empty draft of 9.2m and a full draft of only 10.02m. The difference between the full and empty drafts is less than 1m. This is because the density of liquid hydrogen is extremely low (about 70.8kg / m 3 ), the unit volume mass is small, and the total load capacity is still relatively limited even when fully loaded, and the center of gravity of the ship is relatively high. In order to ensure navigation stability, a certain amount of ballast water needs to be added to the ballast tank even when fully loaded. This undoubtedly increases the load capacity and the average transportation cost per ton of liquid hydrogen, thereby increasing the ship's operating costs.

[0005] LNG, which is also a major clean energy source, also has the problem of generating a large amount of evaporation gas due to heat exchange with the outside world during ship transportation. The storage temperature of LNG is usually around -162℃, which is also a huge temperature difference with the outside world. Even if there is a good insulation layer, it will inevitably exchange heat with the outside world and generate a large amount of LNG evaporation gas. However, the main component of LNG is methane, and its density is about 470kg / m 3 , which is much higher than liquid hydrogen. This makes the LNG carrier have a deeper draft when fully loaded, and there is no need to add ballast water to the ballast tank, so the ship has good stability.

[0006] In addition, important energy exporting countries in the world, such as Australia, have extremely rich LNG and hydrogen resource reserves. Nowadays, the demand for liquid hydrogen and LNG in various countries is increasing. For example, China, Japan, and South Korea, as global energy consumption, the demand for hydrogen and LNG fuels continues to grow. Liquid hydrogen and LNG have similar physical and chemical properties, and the loading port can be set at the same port, which provides practical feasibility for ships to realize the combined transportation of hydrogen and LNG.

[0007] Therefore, if the hydrogen cargo tank, LNG cargo tank and ammonia fuel tank can be combined to form a hierarchical packaging structure from the inside to the outside, by integrating the cold energy advantages of liquid hydrogen, LNG and ammonia, a temperature gradient that decreases step by step from the outside to the inside can be formed, which can greatly reduce the generation of liquid hydrogen BOG and LNG boil-off gas. In addition, compared with a single liquid hydrogen carrier, the density of LNG is much higher than that of liquid hydrogen. Combined transportation will increase the draft of the ship and significantly improve the stability of the ship. Summary of the invention

[0008] The purpose of the present invention is to solve the above-mentioned problems and to propose an ammonia-powered ship liquid hydrogen and LNG combined transport cargo tank system, which includes: q, an ammonia fuel tank, a hydrogen liquid cargo tank, an LNG liquid cargo tank, a hydrogen liquid cargo tank pressure sensor, an LNG liquid cargo tank pressure sensor, a hydrogen fuel cell group, an LNG power generation unit, an ammonia power generation unit, a load control unit, a ship power grid, a propulsion motor, a pressure control unit, a hydrogen fuel valve, an LNG evaporated gas valve, an ammonia fuel valve, an external control signal, and a ballast tank.

[0009] The transfer pump is connected to the ammonia fuel power generation unit and the load control unit in sequence. The ammonia fuel tank is connected to the ammonia fuel valve and the ammonia fuel power generation unit in sequence. A pipeline is provided above the LNG liquid cargo tank, which is connected to the LNG evaporation valve and the LNG power generation unit in sequence, and another pipeline is provided, which is connected to the LNG pressure sensor, the pressure control unit, and the LNG power generation unit in sequence. A pipeline is provided above the hydrogen liquid cargo tank, which is connected to the hydrogen evaporation valve and the hydrogen fuel cell group in sequence, and another pipeline is connected to the hydrogen pressure sensor, the pressure control unit, and the hydrogen fuel cell group in sequence. The hydrogen fuel cell group, LNG power generation unit, ammonia fuel power generation unit, propulsion motor and load control unit are respectively connected to the ship's power grid.

[0010] The hydrogen liquid cargo tank is wrapped by the LNG liquid cargo tank, and the two share the same bottom surface. The LNG liquid cargo tank is wrapped by the ammonia fuel tank, and the bottom of the LNG liquid cargo tank is connected to the bottom of the ammonia fuel tank through a support. The hydrogen liquid cargo tank, the LNG liquid cargo tank, and the ammonia liquid cargo tank form a nested structure, and the bulkheads around the three and the bulkheads on the top are independent of each other, and there is a certain distance between them.

[0011] The hydrogen fuel cell group includes a liquid hydrogen BOG supply unit and a hydrogen fuel cell; the LNG power generation unit includes an LNG boil-off gas supply unit and an LNG engine power generation device; the ammonia fuel power generation unit includes an ammonia fuel supply unit and an ammonia fuel engine power generation device.

[0012] The liquid hydrogen BOG produced in the hydrogen liquid cargo tank is sent from the hydrogen liquid cargo tank to the hydrogen fuel cell group through the hydrogen boil-off valve. After the liquid hydrogen BOG reaches the corresponding temperature and pressure in the liquid hydrogen BOG supply unit in the hydrogen fuel cell group, it enters the hydrogen fuel cell. In the hydrogen fuel cell group, the liquid hydrogen BOG directly converts chemical energy into electrical energy through electrochemical reactions, and the generated electrical energy is incorporated into the ship's power grid. At the same time, the hydrogen pressure sensor monitors the pressure in the hydrogen liquid cargo tank in real time and feeds back the pressure information to the pressure control unit. The pressure control unit controls the amount of liquid hydrogen BOG entering the hydrogen fuel cell group by controlling the liquid hydrogen BOG supply unit in the hydrogen fuel cell group, thereby always controlling the pressure in the hydrogen liquid cargo tank between 0.1 bar and 0.15 bar.

[0013] The LNG boil-off gas generated in the LNG cargo tank first enters the LNG power generation unit through the LNG boil-off gas valve. After the LNG boil-off gas reaches the corresponding temperature and pressure in the LNG boil-off gas supply unit in the LNG power generation unit, it enters the LNG engine power generation device to convert chemical energy into electrical energy, and the generated electrical energy is incorporated into the ship's power grid. At the same time, the LNG pressure sensor monitors the pressure in the LNG cargo tank in real time and feeds back the pressure data to the pressure control unit. The pressure control unit controls the amount of LNG boil-off gas entering the LNG power generation unit by controlling the LNG boil-off gas supply unit in the LNG power generation unit, thereby always controlling the pressure in the LNG cargo tank between 0.1 bar and 0.15 bar.

[0014] The ammonia vapor produced by the ammonia fuel tank enters the ammonia fuel power generation unit through the ammonia fuel valve. The liquid ammonia fuel is transported to the ammonia fuel power generation unit through a pipeline under the action of the transfer pump. After the ammonia vapor supply unit reaches the corresponding temperature and pressure, the ammonia fuel enters the ammonia fuel engine power generation device to be converted into electrical energy and incorporated into the ship's power grid. Among them, the ship's power grid transmits the electrical energy of the LNG power generation unit, the hydrogen fuel cell group and the ammonia fuel power generation unit to the propulsion motor, and feeds back the generated electrical energy signal to the load control unit. The ship's control system transmits external control signals to the load control unit according to the load demand of the propulsion motor, and the load control unit then controls the amount of ammonia fuel delivered to the ammonia fuel power generation unit.

[0015] Beneficial effects of the present invention:

[0016] 1. Aiming at the low temperature characteristics of liquid hydrogen and LNG, the present invention forms a temperature gradient that decreases step by step from the outside to the inside by combining hydrogen liquid cargo tanks, LNG liquid cargo tanks, and ammonia fuel tanks. This hierarchical packaging structure can weaken the external heat penetration layer by layer, reduce the temperature difference between liquid hydrogen and LNG and the outside world, and greatly reduce the amount of liquid hydrogen and LNG evaporation gas generated.

[0017] 2. Compared with a single liquid hydrogen transport ship, the liquid hydrogen and LNG combined transport ship of the present invention increases the draft of the ship and significantly improves the ship's stability and transport efficiency because the density of LNG is much higher than that of liquid hydrogen. Moreover, when the ship is fully loaded, there is no need to add pressurized water, which improves the transport efficiency.

[0018] 3. The amount of liquid hydrogen BOG produced by the present invention is very small, so it can be sent to the hydrogen fuel cell for treatment. Compared with the reliquefaction method, it avoids a large amount of refrigeration power consumption, and compared with sending it to the ship power unit for combustion, it reduces heat loss and improves energy utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a system diagram of the present invention;

[0020] Figure 2 A top view of the present invention

[0021] Figure 3 A side view of the present invention

[0022] In the attached figure: 1. Hydrogen liquid cargo tank; 2. LNG liquid cargo tank; 3. Ammonia fuel tank; 4. Transfer pump; 5. Hydrogen pressure sensor; 6. LNG pressure sensor; 7. Hydrogen fuel cell stack; 8. LNG power generation unit; 9. Ammonia fuel power generation unit; 10. Load control unit; 11. Ship power grid; 12. Propulsion motor; 13. Pressure control unit; 14. Hydrogen evaporation valve; 15. LNG evaporation valve; 16. Ammonia fuel valve; 17. External control signal; 18. Ballast tank. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings.

[0024] like Figure 1 , Figure 2 , Figure 3 As shown, the present invention proposes a liquid hydrogen and LNG combined transport cargo tank system for an ammonia-powered ship, the system comprising: a hydrogen liquid cargo tank 1, an LNG liquid cargo tank 2, an ammonia fuel tank 3, a transfer pump 4, a hydrogen pressure sensor 5, an LNG pressure sensor 6, a hydrogen fuel cell group 7, an LNG power generation unit 8, an ammonia fuel power generation unit 9, a load control unit 10, a ship power grid 11, a propulsion motor 12, a pressure control unit 13, a hydrogen evaporation valve 14, an LNG evaporation valve 15, an ammonia fuel valve 16, an external control signal 17, and a ballast tank 18.

[0025] like Figure 1 As shown, the fuel tank adopts special insulation materials and high-strength structural design to ensure that it can withstand the storage pressure of the internal ammonia fuel and the influence of the external environment. The LNG liquid cargo tank 2 is installed inside the ammonia fuel tank 3, and the LNG liquid cargo tank 2 is firmly connected to the bottom of the ammonia fuel tank 3 through the bottom support to ensure that the position of the LNG liquid cargo tank 2 is fixed. The LNG liquid cargo tank 2 also has good insulation performance to reduce the heat exchange with the outside and the ammonia fuel tank 3. The hydrogen liquid cargo tank 1 is installed inside the LNG liquid cargo tank 2 so that the two share the same bottom surface. A unique nested structure is formed by the hydrogen liquid cargo tank 1, the LNG liquid cargo tank 2 and the ammonia liquid cargo tank 3. This nested structure is composed of the hydrogen liquid cargo tank 1, the LNG liquid cargo tank 2 and the ammonia liquid cargo tank 3 from the inside to the outside. Specifically, the hydrogen liquid cargo tank 1 is wrapped by the LNG liquid cargo tank 2, and the LNG liquid cargo tank 2 is wrapped by the ammonia liquid cargo tank 3. In this structure, the bulkheads around the three and the bulkheads on the top are independent of each other, and there is a certain distance between them, such as Figure 2 , Figure 3In addition, the hydrogen liquid cargo tank 1 and the LNG liquid cargo tank 2 use ultra-low temperature insulation materials to meet the requirements of liquid hydrogen and LNG storage for extremely low temperature environments.

[0026] like Figure 1 As shown, the transfer pump 4 is connected to the ammonia fuel power generation unit 9 and the load control unit 10 in sequence through pipelines and lines to ensure that the ammonia fuel can be smoothly transported to the power generation unit and realize the regulation of energy transmission. Hydrogen pressure sensor 5 and LNG pressure sensor 6 are installed in the hydrogen liquid cargo tank 1 and LNG liquid cargo tank 2 respectively for real-time monitoring of evaporation gas pressure. At the same time, the hydrogen evaporation gas valve 14 and the LNG evaporation gas valve 15 are connected to the hydrogen fuel cell group 7 and the LNG power generation unit 8 to control the delivery of evaporation gas. The ammonia fuel valve 16 is installed on the pipeline between the ammonia fuel tank 3 and the ammonia fuel power generation unit 9 to accurately control the delivery amount of ammonia fuel. The ship power grid 11 is connected with each power generation unit, the propulsion motor 12, and the load control unit 10 by lines to realize the transmission of power and signals. The pressure control unit 13 is connected to the hydrogen pressure sensor 5, the LNG pressure sensor 6, the hydrogen evaporation gas valve 14, and the LNG evaporation gas valve 15 to achieve stable control of the system pressure.

[0027] The hydrogen fuel cell stack 7 includes a liquid hydrogen BOG supply unit and a hydrogen fuel cell; the LNG power generation unit 8 includes an LNG boil-off gas supply unit and an LNG engine power generation device; the ammonia fuel power generation unit 9 includes an ammonia fuel supply unit and an ammonia fuel engine power generation device.

[0028] The LNG boil-off gas generated in the LNG cargo tank 2 first enters the LNG power generation unit 8 through the LNG boil-off gas valve 15. After the LNG boil-off gas reaches the corresponding temperature and pressure in the LNG boil-off gas supply unit in the LNG power generation unit 8, it enters the LNG engine power generation device to convert chemical energy into electrical energy, and the generated electrical energy is incorporated into the ship power grid 11. At the same time, the LNG pressure sensor 6 monitors the pressure in the LNG cargo tank 2 in real time and feeds back the pressure data to the pressure control unit 13. The pressure control unit 13 controls the amount of LNG boil-off gas entering the LNG power generation unit 8 by controlling the LNG boil-off gas supply unit in the LNG power generation unit 8, so that the pressure in the LNG cargo tank 2 is always controlled between 0.1 bar and 0.15 bar.

[0029] The liquid hydrogen BOG generated in the hydrogen liquid cargo tank 1 is sent from the hydrogen liquid cargo tank 1 to the hydrogen fuel cell group 7 through the hydrogen boil-off valve 14. After the liquid hydrogen BOG reaches the corresponding temperature and pressure in the liquid hydrogen BOG supply unit in the hydrogen fuel cell group 7, it enters the hydrogen fuel cell. In the hydrogen fuel cell group 7, the liquid hydrogen BOG directly converts chemical energy into electrical energy through electrochemical reaction, and the generated electrical energy is incorporated into the ship power grid 11. At the same time, the hydrogen pressure sensor 5 monitors the pressure in the hydrogen liquid cargo tank 1 in real time and feeds back the pressure information to the pressure control unit 13. The pressure control unit 13 controls the amount of liquid hydrogen BOG entering the hydrogen fuel cell group 7 by controlling the liquid hydrogen BOG supply unit in the hydrogen fuel cell group 7, so that the pressure in the hydrogen liquid cargo tank 1 is always controlled between 0.1 bar and 0.15 bar.

[0030] The ammonia vapor produced by the ammonia fuel tank 3 enters the ammonia fuel power generation unit 9 through the ammonia fuel valve 16, and the liquid ammonia fuel is transported to the ammonia fuel power generation unit 9 through the pipeline under the action of the transfer pump 4. After the ammonia fuel reaches the corresponding temperature and pressure in the ammonia vapor supply unit in the ammonia fuel power generation unit 9, it enters the ammonia fuel engine power generation device to be converted into electrical energy and is incorporated into the ship power grid 11. Among them, the ship power grid 11 transmits the electrical energy of the LNG power generation unit 8, the hydrogen fuel cell group 7 and the ammonia fuel power generation unit 9 to y12, and feeds back the generated electrical energy signal to the load control unit 10. The ship control system transmits the external control signal 17 to the load control unit 10 according to the load demand of the propulsion motor 12, and the load control unit 10 further controls the amount of ammonia fuel delivered to the ammonia fuel power generation unit 9. Assuming that the propulsion power of the propulsion motor 12 required for the ship's navigation is 18000kW, the hydrogen fuel cell group 7 can provide 1500kW, and the LNG power generation unit 8 can provide 8000kW. The load control unit 10 calculates that the power required to be provided by the ammonia fuel power generation unit 9 is 8500kW based on the external control signal 17 transmitted by the ship control system and the electric energy signal fed back by the ship power grid 11, and then controls the ammonia fuel supply of the ammonia fuel power generation unit 9 to meet this requirement.

[0031] If the ship speeds up, the load control unit 10 calculates the power that needs to be increased and controls the ammonia fuel power generation unit 9 to increase the ammonia fuel delivery; if the ship slows down, the load control unit 10 calculates the power that needs to be reduced and controls the ammonia fuel power generation unit 9 to reduce the ammonia fuel delivery. In addition, because the amount of evaporated gas generated in the hydrogen liquid cargo tank 1 and the LNG liquid cargo tank 2 fluctuates due to the influence of the ship's navigation status and weather, the power provided by the hydrogen fuel cell group 7 and the LNG power generation unit 8 also fluctuates. The load control unit 10 regulates the amount of ammonia fuel required by the ammonia fuel supply unit by calculating the power difference in real time. In short, the difference between the power required by the propulsion motor 12 and the total power provided by the hydrogen fuel cell group 7 and the LNG power generation unit 8 is compensated by the ammonia fuel power generation unit 9.

[0032] The pressure control unit 13 plays a key role in pressure regulation. The hydrogen pressure sensor 5 monitors the pressure in the hydrogen liquid cargo tank 1 in real time and feeds back the pressure signal to the pressure control unit 13. The pressure control unit 13 controls the pressure in the hydrogen liquid cargo tank 1 to about 0.125 bar. When the ship is sailing normally, the pressure in the hydrogen liquid cargo tank 1 will fluctuate between 0.1 bar and 0.15 bar. If the pressure is higher than 0.125 bar, the pressure control unit 13 will issue an instruction to the liquid hydrogen BOG supply unit in the hydrogen fuel cell group 7 to increase the liquid hydrogen BOG delivery amount, so that the pressure in the hydrogen liquid cargo tank 1 decreases. The greater the pressure deviation from 0.125 bar, the greater the liquid hydrogen BOG delivery amount. On the contrary, if the pressure is lower than 0.125 bar, the pressure control unit 13 will issue an instruction to the liquid hydrogen BOG supply unit in the hydrogen fuel cell group 7 to reduce the liquid hydrogen BOG delivery amount, so that the pressure in the hydrogen liquid cargo tank 1 increases. The greater the pressure deviation from 0.125 bar, the less the liquid hydrogen BOG delivery amount, and the pressure in the hydrogen liquid cargo tank 1 is always maintained between 0.1 bar and 0.15 bar.

[0033] Similarly, for the LNG cargo tank 2, the LNG pressure sensor 6 feeds back the pressure signal in real time, and the pressure control unit 13 also controls the pressure at about 0.125 bar, and normally fluctuates between 0.1 bar and 0.15 bar. When the pressure is higher than 0.125 bar, the pressure control unit 13 controls the LNG boil-off gas supply unit to increase the delivery amount of the LNG boil-off gas. The greater the pressure deviation from 0.125 bar, the greater the delivery amount of the LNG boil-off gas; when the pressure is lower than 0.125 bar, the pressure control unit 13 controls the LNG boil-off gas supply unit to reduce the delivery amount of the LNG boil-off gas. The greater the pressure deviation from 0.125 bar, the less the delivery amount of the LNG boil-off gas, and the pressure in the LNG cargo tank 2 is always maintained between 0.1 bar and 0.15 bar.

[0034] The present invention uses a layered wrapping structure. Since the LNG liquid cargo tank 2 and the ammonia fuel tank 3 are wrapped on the outside of the hydrogen liquid cargo tank 1, and LNG has an ultra-low temperature, the temperature difference between the hydrogen liquid cargo tank 1 and the outside is reduced by about 190°C compared with the traditional liquid hydrogen storage method, which greatly reduces the heat exchange between the hydrogen liquid cargo tank 1 and the outside, and reduces the generation of liquid hydrogen BOG. ​​Similarly, since the ammonia fuel tank 3 is wrapped on the outside of the LNG liquid cargo tank 2, and the ammonia fuel has a low temperature, the temperature difference between the LNG liquid cargo tank 2 and the outside is reduced by about 70°C compared with the traditional LNG storage method, which greatly reduces the heat exchange between the LNG liquid cargo tank 2 and the outside. At the same time, since the temperature of liquid hydrogen is much lower than that of LNG, the cold energy of liquid hydrogen will be transferred to the LNG liquid cargo tank 2, making the temperature inside the LNG liquid cargo tank 2 lower, which greatly reduces the generation of LNG evaporation gas.

[0035] The hydrogen fuel cell group 7 and the LNG power generation unit 8 are mainly responsible for processing liquid hydrogen BOG and LNG boil-off gas and converting them into electrical energy. Since the liquid hydrogen BOG and LNG boil-off gas generated by the present invention are very small, and the load of the hydrogen fuel cell group 7 and the LNG power generation unit 8 is small when the ship is sailing, especially when it needs to travel at high speed or cope with complex working conditions, the electricity generated by the hydrogen fuel cell group 7 and the LNG power generation unit 8 alone cannot meet all power requirements. Therefore, the ammonia fuel power generation unit 9 is required to continuously provide the main power for the ship to compensate for the remaining power requirements.

[0036] Due to the density of LNG (about 470kg / m 3 ) is much higher than the density of liquid hydrogen (about 70.8kg / m 3 ), when LNG and liquid hydrogen are transported together, the draft of the ship increases significantly, which effectively improves the stability of the ship during navigation, reduces the risk of the ship shaking or even capsizing due to factors such as wind and waves, and ensures the safety of ship transportation. In addition, when the ship is fully loaded, there is no need to add pressure water to increase the weight of the ship, which improves transportation efficiency and reduces the average transportation cost per ton of liquid hydrogen and LNG.

[0037] Due to the high price of hydrogen, liquid hydrogen BOG is rarely used directly as fuel. Usually, liquid hydrogen BOG is treated by reliquefaction, but the reliquefaction method consumes a lot of refrigeration power. The present invention uses a hierarchical packaging structure to reduce the temperature difference between liquid hydrogen and the outside world, and the amount of liquid hydrogen BOG produced is very small, so it can be passed into a hydrogen fuel cell 7 with a higher energy conversion rate for treatment, without the need to use reliquefaction to treat liquid hydrogen BOG, thereby reducing the cost of treating liquid hydrogen BOG. ​​In addition, compared with sending it to a ship power unit for combustion, sending it to a hydrogen fuel cell 7 reduces heat loss and has a higher energy utilization rate.

[0038] The above is only a preferred implementation mode of the present invention, but it is not limited to the above embodiments when it is implemented. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An ammonia powered ship liquid hydrogen and LNG combined transport cargo tank system, characterized by: The present invention comprises a hydrogen liquid cargo tank (1), an LNG liquid cargo tank (2), an ammonia fuel tank (3), a transfer pump (4), a hydrogen pressure sensor (5), an LNG pressure sensor (6), a hydrogen fuel cell group (7), an LNG power generation unit (8), an ammonia fuel power generation unit (9), a load control unit (10), a ship power grid (11), a propulsion motor (12), a pressure control unit (13), a hydrogen evaporation valve (14), an LNG evaporation valve (15), an ammonia fuel valve (16), an external control signal (17), and a ballast tank (18). The transfer pump (4) is connected to the ammonia fuel power generation unit (9) and the load control unit (10) in sequence; the ammonia fuel tank (3) is connected to the ammonia fuel valve (16) and the ammonia fuel power generation unit (9) in sequence; a pipeline is provided above the LNG liquid cargo tank (2) and is connected to the LNG evaporation valve (15) and the LNG power generation unit (8) in sequence; another pipeline is provided and is connected to the LNG pressure sensor (6), the pressure control unit (13), and the LNG power generation unit (8) in sequence; a pipeline is provided above the hydrogen liquid cargo tank (1) and is connected to the hydrogen evaporation valve (14) and the hydrogen fuel cell group (7) in sequence; another pipeline is connected to the hydrogen pressure sensor (5), the pressure control unit (13), and the hydrogen fuel cell group (7) in sequence; the hydrogen fuel cell group (7), the LNG power generation unit (8), the ammonia fuel power generation unit (9), the propulsion motor (12), and the load control unit (10) are respectively connected to the ship power grid (11); The hydrogen liquid cargo tank (1) is wrapped by the LNG liquid cargo tank (2), and the two share the same bottom surface. The LNG liquid cargo tank (2) is wrapped by the ammonia fuel tank (3), and the bottom of the LNG liquid cargo tank (2) is connected to the bottom of the ammonia fuel tank (3) through a support.

2. The ammonia-powered ship liquid hydrogen and LNG combined transport cargo tank system according to claim 1 is characterized by: By combining the hydrogen liquid cargo tank (1), the LNG liquid cargo tank (2), and the ammonia fuel tank (3) to form a hierarchical wrapping structure, a temperature gradient that decreases step by step from the outside to the inside is formed.

3. The ammonia-powered ship liquid hydrogen and LNG combined transport cargo tank system according to claim 1 is characterized in that: The ammonia vapor generated by the ammonia fuel tank (3) enters the ammonia fuel power generation unit (9) to be converted into electric energy and then connected to the ship power grid (11). The ship power grid (11) transmits the electric energy of the hydrogen fuel cell group (7), the LNG power generation unit (8) and the ammonia fuel power generation unit (9) to the propulsion motor (12). The load control unit (10) receives an external control signal (17) and regulates the amount of ammonia fuel delivered to the ammonia fuel power generation unit (9) to meet the propulsion power of the propulsion motor (12).

4. The ammonia-powered ship liquid hydrogen and LNG combined transport cargo tank system according to claim 1 is characterized in that: The pressure control unit (13) always controls the pressure in the hydrogen liquid cargo tank (1) and the LNG liquid cargo tank (2) to be between 0.1 bar and 0.15 bar.

5. The ammonia-powered ship liquid hydrogen and LNG combined transport cargo tank system according to claim 1 is characterized in that: When the liquid hydrogen and LNG combined transport ship is fully loaded, the ballast tank (18) does not need to be pressurized with water.

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