Vacuum heat insulation system for liquid hydrogen transport ship cargo hold

Abstract

The invention relates to the technical field of ships, and provides a liquid hydrogen transport ship cargo hold vacuum heat insulation system which comprises a liquid hydrogen cargo hold, a vacuum layer, a cargo hold compressor, a vacuum pump, a fuel compressor, a temperature control system, a power device, a gas sensor, a one-way valve, an electromagnetic valve and a monitoring device. According to the method, external air permeating into the vacuum layer in the vacuum layer or hydrogen leaked into the vacuum layer by the liquid hydrogen cargo hold in the vacuum layer is constantly pumped through the vacuum pump, so that the vacuum layer is always kept at a relatively high vacuum degree, a good heat insulation effect is achieved, and BOG (Boil Off Gas) in the liquid hydrogen cargo hold is reduced. In addition, through cooperation of the gas sensor, the vacuum pump and the monitoring device, the leakage problem of the vacuum layer can be monitored at any time, corresponding emergency treatment measures are taken, and good practicability is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of ships, and in particular relates to a vacuum insulation system for a cargo hold of a liquid hydrogen transport ship. Background Art

[0002] As the International Maritime Organization (IMO) sets higher and higher standards for carbon emissions from ships, hydrogen, as an ideal clean fuel, is increasingly in demand worldwide. In order to reduce the storage space for hydrogen on ships, liquid hydrogen (LH 2 ) in the form of liquid hydrogen stored on ships. Ships that transport liquid hydrogen are called liquid hydrogen tankers.

[0003] The storage of liquid hydrogen on ships needs to be carried out under specific conditions such as low temperature and high pressure. During the transportation of liquid hydrogen, due to the extremely low storage temperature of liquid hydrogen (about -253°C) and the temperature difference of nearly 300°C with nature, even under good insulation conditions, such as increasing the wall thickness of the liquid hydrogen cargo hold, heat exchange will inevitably occur, thereby producing a large amount of boil-off gas (BOG). The traditional method of dealing with BOG is to compress BOG and then liquefy it. This method is often accompanied by high power consumption, which greatly increases the transportation cost. As hydrogen-blended engine technology gradually matures, hydrogen-blended combustion has shown many advantages. For example, hydrogen-blended combustion in diesel engines can significantly improve the combustion process, improve combustion efficiency, and reduce particulate matter (PM) and nitrogen oxides (NO x ) and other pollutants. Therefore, the BOG generated in the liquid hydrogen cargo tank can be sent to the ship's hydrogen-blended engine for combustion.

[0004] Heat transfer is mainly carried out through three ways: heat conduction, heat convection and heat radiation. In order to ensure the thermal insulation of the liquid hydrogen cargo tank, a vacuum layer can be built around the liquid hydrogen cargo tank. The vacuum environment almost eliminates the influence of heat convection, and also has a significant inhibitory effect on heat conduction and heat radiation. Therefore, the vacuum layer can greatly reduce the transfer of heat and reduce the rate at which external heat is transferred into the liquid hydrogen cargo tank, thereby reducing the generation of BOG in the cargo tank.

[0005] However, the application of the vacuum layer is not without disadvantages. In actual situations, there is a risk of leakage when using vacuum technology. If outside air penetrates into the vacuum layer, due to the large temperature difference between the outside environment and the liquid hydrogen cargo tank, the air that penetrates into the vacuum layer will undergo convective heat exchange with the outer wall of the liquid hydrogen cargo tank, causing more heat to penetrate into the interior of the liquid hydrogen cargo tank, prompting the liquid hydrogen cargo tank to produce more BOG; if the hydrogen (including liquid hydrogen and BOG) in the liquid hydrogen cargo tank leaks into the vacuum layer, due to the flammable and explosive properties of hydrogen, it is very easy to cause an explosion accident under certain conditions, posing a serious threat to the safety of the ship. At the same time, the hydrogen leaked into the vacuum layer will become a heat-conducting medium, causing the heat from the outside to be transferred to the hydrogen, and the liquid hydrogen will quickly absorb the heat and vaporize into BOG, and the BOG will transfer the heat to the liquid hydrogen cargo tank, causing more heat to penetrate into the interior of the liquid hydrogen cargo tank, further prompting the liquid hydrogen to produce more BOG. ​​Therefore, if the vacuum layer leaks, it will seriously affect the storage stability and safety of liquid hydrogen.

[0006] In order to effectively monitor whether the vacuum layer leaks, it is usually necessary to deploy sensors in the vacuum layer. However, due to the large outer surface of the liquid hydrogen cargo tank, the entire three-dimensional space of the vacuum layer is too large. In order to achieve comprehensive and accurate monitoring, sensors need to be deployed in multiple locations in the vacuum layer space. Due to the large space, the number of sensors is huge, which greatly increases the complexity of monitoring and the cost of the system.

[0007] Based on the above problems, if a vacuum insulation system for the cargo hold of a liquid hydrogen transport ship can be designed, the gas in the vacuum layer can be extracted by a vacuum pump at all times, so that the vacuum layer always maintains a high vacuum degree, which plays a good insulation role, reduces the generation of BOG in the liquid hydrogen cargo hold, and can always monitor the leakage of the vacuum layer, which has good practicality. Summary of the invention

[0008] The purpose of the present invention is to solve the above-mentioned problems and to propose a vacuum insulation system for the cargo hold of a liquid hydrogen transport ship, the system comprising: a liquid hydrogen cargo hold, a vacuum layer, a cargo hold compressor, a vacuum pump, a fuel compressor, a temperature control system, a power unit, a gas sensor, a one-way valve, a solenoid valve, and a monitoring device.

[0009] The liquid hydrogen cargo tank is wrapped by the vacuum layer, and the top of the liquid hydrogen cargo tank is connected to the cargo tank compressor. The cargo tank compressor is connected to the vacuum pump, the fuel compressor, the temperature control system, and the power device in sequence. The vacuum layer is connected to the one-way valve, the solenoid valve, the gas sensor, and the vacuum pump in sequence through a pipeline. The monitoring device is connected to the gas sensor and the solenoid valve.

[0010] The liquid hydrogen cargo tank is located inside the ship and is used to store liquid hydrogen. The interlayer space between the outer wall of the liquid hydrogen cargo tank and the inner wall of the ship is called a vacuum layer. The vacuum layer can keep the liquid hydrogen cargo tank in a vacuum environment, reduce the heat exchange between liquid hydrogen and the external environment, and thus reduce the amount of BOG generated. The gas sensor can monitor the leakage of hydrogen at all times. If a hydrogen leak is detected, the leakage signal will be immediately transmitted to the monitoring device. The power unit is a combination of various equipment and systems that provide power for the ship. According to the actual situation of the ship, the ship power unit may be a ship main engine or auxiliary engine mixed with hydrogen, a hydrogen fuel cell or a ship boiler burning hydrogen, etc.

[0011] During the voyage of a liquid hydrogen carrier, the liquid hydrogen in the liquid hydrogen cargo hold will inevitably produce BOG due to the huge temperature difference between the liquid hydrogen in the liquid hydrogen cargo hold and the external environment. BOG is extracted from the liquid hydrogen cargo hold by the cargo hold compressor, compressed and transported to the vacuum pump, and then sent to the fuel compressor for further compression to reach the pressure for supplying the power unit, then enters the temperature control system to be heated to the temperature for supplying the power unit, and finally sent to the power unit for combustion.

[0012] At the same time, the negative pressure generated inside the vacuum pump draws out the gas in the vacuum layer so that the vacuum layer always maintains a high vacuum degree, and the gas sensor monitors the changes in the gas composition in the vacuum layer in real time.

[0013] If outside air penetrates into the vacuum layer, the gas sensor will transmit the signal of the gas composition to the monitoring device, and the monitoring device will send out an alarm signal of air infiltration. The signal is transmitted to the solenoid valve, and the solenoid valve will be closed in time to prevent air from entering the vacuum pump and mixing with hydrogen to cause an explosion. At the same time, it reminds the ship's personnel to take emergency measures for vacuum layer leakage in time.

[0014] If hydrogen leaks, the vacuum pump will suck the BOG leaking from the vacuum layer and the BOG from the liquid hydrogen cargo tank at the same time and mix them fully. After mixing, the vacuum pump will send the fuel compressor to the pressurized BOG, and then send the pressurized BOG to the temperature control system for heating. Finally, the pressurized and heated BOG is sent to the power unit. At the same time, the gas sensor transmits the signal of the gas component to the monitoring device, and the monitoring device sends an alarm signal of BOG leakage to remind the ship personnel to take emergency measures for the vacuum layer leakage in time.

[0015] Beneficial effects of the present invention:

[0016] 1. The present invention enables the vacuum layer to maintain a high vacuum degree in real time, so that the liquid hydrogen cargo tank is always in a vacuum environment, preventing the gas leaked in the vacuum layer from becoming a heat-conducting medium and performing convection heat exchange with the outer wall of the liquid hydrogen cargo tank, thereby avoiding more heat from flowing into the liquid hydrogen cargo tank, thereby reducing the generation of BOG in the liquid hydrogen cargo tank.

[0017] 2. In the present invention, each liquid hydrogen cargo tank realizes gas leakage monitoring through only one vacuum pump and one gas sensor, which greatly simplifies the complexity of monitoring, reduces the cost of the system, and improves the efficiency and safety of liquid hydrogen cargo tank monitoring compared with the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The system diagram of the present invention

[0019] Figure 2 This is a cross-sectional schematic diagram of the cargo hold of the liquid hydrogen transport ship of the present invention.

[0020] Figure 3 A schematic diagram of the cargo hold axle side of a liquid hydrogen transport ship

[0021] In the attached figure: 1. Liquid hydrogen cargo tank; 2. Vacuum layer; 3. Cargo tank compressor; 4. Vacuum pump; 5. Fuel compressor; 6. Temperature control system; 7. Power unit; 8. Gas sensor; 9. Check valve; 10. Solenoid valve; 11. Monitoring device DETAILED DESCRIPTION

[0022] 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.

[0023] like Figure 1 , Figure 2 , Figure 3 As shown, the present invention proposes a vacuum insulation system for a liquid hydrogen transport ship cargo hold, the system comprising: a liquid hydrogen cargo hold 1, a vacuum layer 2, a cargo hold compressor 3, a vacuum pump 4, a fuel compressor 5, a temperature control system 6, a power unit 7, a gas sensor 8, a one-way valve 9, a solenoid valve 10, and a monitoring device 11.

[0024] like Figure 1 , Figure 2 , Figure 3 As shown, the liquid hydrogen cargo tank 1 is wrapped by the vacuum layer 2, and the top of the liquid hydrogen cargo tank 1 is connected to the cargo tank compressor 3. The cargo tank compressor 3 is sequentially connected to the vacuum pump 4, the fuel compressor 5, the temperature control system 6, and the power device 7. The vacuum layer 2 is sequentially connected to the one-way valve 9, the solenoid valve 10, the gas sensor 8, and the vacuum pump 4 through a pipeline. The monitoring device 11 is connected to the gas sensor 8 and the solenoid valve 10.

[0025] like Figure 1As shown, the vacuum pump 4 is a jet pump. Based on the Bernoulli principle, the BOG in the liquid hydrogen cargo tank 1 is used as the working fluid, and the gas in the vacuum layer 2 is used as the ejection fluid. When the BOG in the liquid hydrogen cargo tank 1 passes through the nozzle, a high-speed jet is generated, thereby forming a low-pressure area at the nozzle outlet. This low-pressure area attracts the gas in the vacuum layer 2 and mixes it with the BOG in the liquid hydrogen cargo tank 1. After mixing, the required pressure and flow are achieved through the diffusion chamber, and then it is transported to the fuel compressor 5.

[0026] The liquid hydrogen cargo tank 1 is located inside the ship and is used to store liquid hydrogen. The interlayer space between the outer wall of the liquid hydrogen cargo tank 1 and the inner wall of the ship is called a vacuum layer 2. The vacuum layer 2 can keep the liquid hydrogen cargo tank 1 in a vacuum environment at all times, reducing the heat exchange between liquid hydrogen and the external environment, thereby reducing the amount of BOG generated. The gas sensor 8 can monitor the leakage of hydrogen at all times. If a hydrogen leakage is detected, the leakage signal will be immediately transmitted to the monitoring device 11. The power unit 7 is a combination of various equipment and systems that provide power for the ship. According to the actual situation of the ship, the ship power unit 7 may be a ship main engine or auxiliary engine for hydrogen fueling, a hydrogen fuel cell or a ship boiler burning hydrogen, etc.

[0027] During the voyage of the liquid hydrogen transport ship, the liquid hydrogen in the liquid hydrogen cargo hold 1 will inevitably produce BOG due to the great temperature difference between the liquid hydrogen and the external environment. Under the action of the cargo hold compressor 3, the BOG is extracted from the liquid hydrogen cargo hold 1, compressed and transported to the vacuum pump 4. Under the action of the vacuum pump 4, the BOG is sent to the fuel compressor 5 for multi-stage pressurization to increase the pressure of the BOG to a level that meets the combustion requirements of the power unit 7. The pressurized BOG enters the temperature control system 6. The temperature control system 6 uses a heat exchanger to accurately adjust the temperature of the BOG according to the combustion temperature requirements of the power unit 7, so that its temperature is stabilized in the optimal combustion range, and then sent to the power unit 7 for combustion.

[0028] At the same time, the negative pressure generated inside the vacuum pump 4 draws out the gas in the vacuum layer 2, so that the vacuum layer 2 always maintains a high vacuum degree, and the gas sensor 8 monitors the changes in the gas composition in the vacuum layer 2 in real time.

[0029] If outside air infiltrates into the vacuum layer 2, due to the large temperature difference between the outside environment and the liquid hydrogen cargo tank 1, the air infiltrated into the vacuum layer 2 will undergo convection heat exchange with the outer wall of the liquid hydrogen cargo tank 1, causing more heat to infiltrate the interior of the liquid hydrogen cargo tank 1, prompting the liquid hydrogen cargo tank 1 to produce more BOG. ​​At this time, the gas sensor 8 transmits the signal of the gas component detected to the monitoring device 11, and the monitoring device 11 sends an alarm signal of air infiltration, and the signal is transmitted to the solenoid valve 10, and the solenoid valve 10 is closed in time to prevent air from entering the vacuum pump 4 and mixing with BOG to cause an explosion. At the same time, it reminds the ship personnel to take emergency measures for the leakage of the vacuum layer 2 in time.

[0030] If BOG leaks, hydrogen is flammable and explosive, which can easily cause an explosion under certain conditions, posing a serious threat to the safety of the ship. At the same time, the BOG leaked into the vacuum layer 2 will become a heat-conducting medium, exchange heat with the external environment, and the BOG temperature will rise. Then, it will convectively exchange heat with the outer wall of the liquid hydrogen cargo tank 1, causing more heat to penetrate into the liquid hydrogen cargo tank 1, further prompting the liquid hydrogen to produce more BOG. ​​At this time, the vacuum pump 4 simultaneously sucks in and fully mixes the BOG leaked from the vacuum layer 2 and the BOG from the cargo tank compressor 3. The mixed BOG is further compressed by the fuel compressor 5 to reach the pressure supplied to the power unit 7, and then enters the temperature control system 6 to be heated to the temperature supplied to the power unit 7, and finally sent to the power unit 7 for combustion. At the same time, the gas sensor 8 transmits the signal of the gas component detected to the monitoring device 11, and the monitoring device 11 sends a leakage alarm signal to remind the ship personnel to take emergency measures for the leakage of the vacuum layer 2 in time.

[0031] The present invention constructs an efficient vacuum insulation system through the coordinated work of the cargo hold compressor 3, the vacuum pump 4 and the vacuum layer 2, so that the vacuum layer 2 can be continuously and stably maintained at a high vacuum level. The purpose is to effectively prevent the air that penetrates into the vacuum layer 2 and the hydrogen that leaks into the vacuum layer 2 from becoming a heat-conducting medium, thereby blocking the heat from being transferred to the liquid hydrogen cargo hold 1 through conduction, convection, etc. It avoids the phase change of liquid hydrogen due to the introduction of external heat, thereby reducing the amount of BOG generated in the liquid hydrogen cargo hold 1, which plays a key role in maintaining the low-temperature liquid storage state of liquid hydrogen, reducing energy consumption, and improving the safety and stability of the overall system.

[0032] In the prior art, the leakage monitoring of the vacuum layer 2 usually involves setting up gas sensors 8 inside the vacuum layer 2 to construct a monitoring system. Since the vacuum layer 2 is distributed on the outer surface of the liquid hydrogen cargo tank and the entire three-dimensional space is large, there are two situations for the layout of the gas sensors 8. The first situation: If a small number of gas sensors 8 are arranged in the three-dimensional space, the distance between adjacent sensors is too large. If a slight gas leak occurs, the concentration change of the leaked gas is difficult to trigger the response of the adjacent gas sensors 8 due to the sparse distribution of the gas sensors 8, and the leakage cannot be effectively monitored. The second situation: If the detection accuracy is to be improved, although a large number of additional gas sensors 8 can achieve more detailed spatial monitoring coverage, it will greatly increase the difficulty of layout and system cost, and will cause many problems in the maintenance and management of the gas sensors 8, data integration and analysis, and overall coordination of the system. The present invention uses the vacuum pump 4 to suck the gas that may leak in the vacuum layer 2 in real time. Once a leak occurs at any position in the vacuum layer 2, the leaked gas can be immediately pumped to the gas sensor 8 by the vacuum pump 4, and an alarm signal is issued in time, and the ship personnel immediately take emergency measures to deal with the leak. In the present invention, each liquid hydrogen cargo tank 1 only has one vacuum pump 4 and one gas sensor 8 to monitor gas leakage. Compared with the existing technology, the complexity of monitoring is greatly simplified, the cost of the system is reduced, and the monitoring efficiency and safety of the liquid hydrogen cargo tank 1 are improved.

[0033] The present invention collects and processes the BOG generated by liquid hydrogen, and through the pressurization of the fuel compressor 5 and the temperature control operation of the temperature control system 6, the BOG meets the operating requirements of the ship power device 7, and the ship power device 7 may be a ship main engine or auxiliary engine mixed with hydrogen, a hydrogen fuel cell or a ship boiler burning hydrogen, etc. This method avoids the complex and energy-intensive reliquefaction process of BOG in the traditional method, significantly reduces the energy consumption of the ship, and improves the energy utilization efficiency of the entire liquid hydrogen transportation system.

[0034] 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. A vacuum insulation system for a cargo hold of a liquid hydrogen transport ship, characterized in that: The present invention comprises a liquid hydrogen cargo tank (1), a vacuum layer (2), a cargo tank compressor (3), a vacuum pump (4), a fuel compressor (5), a temperature control system (6), a power device (7), a gas sensor (8), a one-way valve (9), a solenoid valve (10), and a monitoring device (11); The liquid hydrogen cargo tank (1) is wrapped by the vacuum layer (2), the top of the liquid hydrogen cargo tank (1) is connected to the cargo tank compressor (3), the cargo tank compressor (3) is connected to the vacuum pump (4), the fuel compressor (5), the temperature control system (6), and the power device (7) in sequence, the vacuum layer (2) is connected to the one-way valve (9), the solenoid valve (10), the gas sensor (8), and the vacuum pump (2) in sequence through a pipeline, and the monitoring device (11) is connected to the gas sensor (8) and the solenoid valve (10).

2. The vacuum insulation system for the cargo hold of a liquid hydrogen transport ship according to claim 1, characterized in that: The vacuum pump (4) is based on the Bernoulli principle, the BOG in the liquid hydrogen cargo tank (1) serves as the working fluid, and the gas in the vacuum layer (2) serves as the ejection fluid.

3. The vacuum insulation system for the cargo hold of a liquid hydrogen transport ship according to claim 1, characterized in that: The vacuum pump (4) is used in conjunction with a gas sensor (8). The vacuum pump (4) extracts gas from the vacuum layer (2). The gas sensor (8) monitors the gas components in the vacuum layer (2) in real time and transmits a signal to the monitoring device (11) when a leak is detected in the vacuum layer (2).

4. The vacuum insulation system for a liquid hydrogen transport ship cargo hold according to claim 1, characterized in that: The gas sensor (8) transmits a signal indicating that air has infiltrated the vacuum layer (2) to the monitoring device (11), and the monitoring device (11) controls the electromagnetic valve (10) to close.

5. The vacuum insulation system for the cargo hold of a liquid hydrogen transport ship according to claim 1, characterized in that: The cargo hold vacuum layer (2), the compressor (3) and the vacuum pump (4) work in coordination to construct a vacuum heat insulation system, thereby maintaining a relatively high vacuum degree of the vacuum layer (2) and preventing the outside air that penetrates therein from becoming a heat transfer medium with the hydrogen leaked from the liquid hydrogen cargo hold (1).

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