A CO 2 Combined storage tanks for ammonia fuel and cargo on transport vessels

Abstract

The present invention proposes a combined storage tank for ammonia fuel and cargo on a CO2 transport ship, which cleverly combines the fuel tank and cargo hold of an ammonia-powered CO2 transport ship, immersing the CO2 storage tank in liquid ammonia fuel, and using the cold energy of the liquid ammonia fuel to reduce the temperature difference between liquid carbon dioxide and the external environment, thereby reducing the evaporation rate of carbon dioxide BOG; and when the CO2 transport ship returns to the loading port, the temperature of the CO2 storage tank is relatively low, and the CO2 storage tank does not need to be pre-cooled when refilling carbon dioxide. In addition, the present invention utilizes a combined storage tank to store liquid ammonia fuel and liquid carbon dioxide at the same time, so the ship does not need to be equipped with a larger fuel tank separately, which improves the utilization rate of the ship's cargo hold space and solves the technical problem of storing liquid ammonia fuel on board the ship; at the same time, the cargo capacity of liquid carbon dioxide is greatly increased, the operating efficiency of the ship is improved, and it has good economy.

Description

Technical Field

[0001] The invention belongs to the technical field of ships, and in particular relates to a combined storage tank for ammonia fuel and cargo of a carbon dioxide transport ship. Background Art

[0002] Carbon dioxide is the main gas that produces the greenhouse effect. Carbon capture and storage technology (CCS) is usually used to treat carbon dioxide emissions. During the CCS process, the captured carbon dioxide needs to be transported to a specific area for storage, such as Iceland, deep sea, geological storage, etc. Due to the large amount of carbon dioxide transported, for example, the transportation of China's carbon dioxide to Iceland for storage involves long-distance sea transportation, so CO2 transport ships are the main means of this implementation.

[0003] In the process of transporting carbon dioxide at sea, in order to increase the carrying capacity of the ship, carbon dioxide is usually stored and transported in liquid form in a semi-cold and semi-pressurized manner (temperature is about -49°C, pressure is about 0.7MPa). The semi-cold and semi-pressurized storage method requires the tank to have a certain pressure bearing capacity, so C-type tanks are used to store liquid carbon dioxide. However, the shape of the C-type tank cylinder is completely different from the shape of the rectangular parallelepiped of the ship's cargo hold. Placing the C-type tank in the cargo hold will cause a large amount of unused space between the C-type tank and the cargo hold, resulting in a serious "deficient hold" phenomenon. In other words, the cargo hold space of the ship is large, but the amount of carbon dioxide loaded is not large, which reduces the utilization rate of the ship's cargo hold space.

[0004] In order to reduce the penetration heat between the semi-cold and semi-pressurized C-type storage tank and the external environment, a thicker insulation layer needs to be installed on the CO2 storage tank. The external ambient temperature of the ship during navigation is usually designed according to the working condition of 45°C. The temperature difference between liquid carbon dioxide and the external environment is as high as 94°C. Although the insulation layer is installed outside the storage tank, it is inevitable to produce carbon dioxide evaporation gas (BOG for short). In addition, the route of the ship when transporting carbon dioxide is long, and a large amount of BOG will be generated during the transportation process.

[0005] Ammonia, as a clean energy source, is one of the most ideal fuels for green ships. Therefore, the use of ammonia as the fuel for the power unit of CO2 transport ships is more in line with the concept of "zero carbon" emissions. Since the calorific value of ammonia fuel is about 18MJ / kg and the density is about 617kg / m 3 The calorific value of fuel oil is 42MJ / kg and its density is about 980kg / m 3, and considering the thickness of the insulation layer, the volume of ammonia fuel required for the same calorific value is about 4 times that of fuel oil, that is, the volume of the ammonia fuel tank is about 4 times that of the fuel oil tank. Ammonia fuel is usually stored in liquid form on ships. The storage temperature of ammonia fuel (-33.6℃) is low, and it is flammable, explosive and corrosive. Considering the high storage requirements of liquid ammonia, it is not possible to set up fuel tanks in narrow "corners" such as double bottoms and compartments of ships like fuel oil. The reason is: on the one hand, each fuel tank needs to be equipped with a separate insulation layer, which has a high manufacturing cost; on the other hand, the number of fuel tanks set in "corners" is large, and the shapes are strange and the surface area is large, which will greatly increase the heat exchange area between liquid ammonia and the external environment, increase the evaporation rate of liquid ammonia, and this storage method has great safety risks and does not meet the specifications for ship liquefied gas storage. Therefore, it is necessary to set up a separate fuel tank on the ship to centrally store liquid ammonia fuel, which will occupy more hull space. In addition, since ammonia-powered CO2 transport ships have long routes and need to carry larger amounts of ammonia fuel, setting up a separate ammonia fuel tank on the CO2 transport ship will occupy more hull space, seriously affecting the cargo hold space of the ship, and in turn affecting the ship's carbon dioxide cargo capacity. Therefore, the storage of liquid ammonia fuel on ships is a very large technical challenge.

[0006] Based on this, if a combined storage tank for ammonia fuel and cargo of a CO2 transport ship can be proposed, and liquid ammonia can be directly stored in the cargo hold where the CO2 storage tank is placed, this will not only greatly reduce the temperature difference between liquid carbon dioxide and the external environment and reduce the generation of carbon dioxide BOG, but also greatly increase the space of the ship's cargo hold, so that the space of the cargo hold can be effectively utilized. This method has very high practical application value. Summary of the invention

[0007] The purpose of the present invention is to address the above-mentioned problems and propose a combined storage tank for ammonia fuel and cargo for a CO2 transport ship, where liquid ammonia fuel is directly stored in the cargo hold where the CO2 storage tank is placed, so that the CO2 storage tank is immersed in liquid ammonia fuel, which greatly reduces the temperature difference between liquid carbon dioxide and the external environment (i.e., liquid ammonia, -33.6°C), reduces the generation of carbon dioxide BOG, and can use the cold energy of liquid ammonia fuel to reliquefy the BOG generated by carbon dioxide. The present invention does not require a separate ammonia fuel tank, greatly increases the space of the ship's cargo hold, and makes full use of the large amount of space between the CO2 storage tank and the cargo hold.

[0008] The present invention proposes a combined storage tank for ammonia fuel and cargo of a CO2 transport ship, comprising a CO2 storage tank, a transfer pump, a booster pump, a condenser, a cylinder jacket water heater, a gas compressor, an expansion valve, and a fuel storage tank.

[0009] The CO2 storage tank is placed in the fuel storage cabin, and an insulation layer is provided outside the storage tank; the fuel storage cabin is filled with liquid ammonia fuel, and an insulation layer is provided outside the cabin; the combined storage cabin is composed of a CO2 storage tank and a fuel storage cabin.

[0010] The transfer pump, booster pump, condenser, and jacket water heater are connected in sequence through pipelines, and the pipelines finally lead to the main engine of the ship to form an ammonia fuel supply system. The transfer pump is installed in the fuel storage tank.

[0011] The CO2 storage tank, gas compressor, condenser and expansion valve are connected in sequence through pipelines to form a carbon dioxide BOG reliquefaction processing system.

[0012] During the voyage of the ship, the liquid ammonia fuel in the fuel storage tank is transferred out of the fuel storage tank through the transfer pump, and then the booster pump is used to pressurize the liquid ammonia fuel in the pipeline. The pressurized liquid ammonia fuel exchanges heat with the refrigerant in the condenser, and then enters the cylinder jacket water heater. The cylinder jacket water heater heats the liquid ammonia fuel to the supply temperature to meet the intake temperature of the ship's main engine for use by the ship's main engine.

[0013] In the carbon dioxide BOG reliquefaction treatment system, the BOG generated in the CO2 storage tank enters the gas compressor through a pipeline. The gas compressor compresses the BOG to a gaseous state with a higher temperature and pressure, and then enters the condenser to exchange heat with liquid ammonia. The BOG is cooled and liquefied, and then the liquid carbon dioxide is decompressed by the expansion valve and flows back to the CO2 storage tank.

[0014] Furthermore, in order to reasonably utilize the hull space, the present invention does not need to set up a separate fuel tank, and the liquid ammonia fuel is stored in the fuel storage tank, so that the CO2 storage tank is immersed in the liquid ammonia fuel.

[0015] Beneficial effects of the present invention:

[0016] 1. The present invention is applied to a CO2 transport ship powered by ammonia fuel, and the fuel tank is cleverly combined with the cargo tank, so that the CO2 storage tank is immersed in liquid ammonia fuel, the cold energy of the liquid ammonia fuel is reasonably utilized, and the temperature difference between the liquid carbon dioxide and the external environment is greatly reduced, thereby reducing the evaporation rate of carbon dioxide BOG.

[0017] 2. The present invention cleverly combines the fuel tank with the cargo tank and utilizes the combined storage tank to simultaneously store liquid ammonia fuel and liquid carbon dioxide. The ship does not need to be equipped with a separate fuel tank, thereby improving the utilization rate of the ship's cargo hold space, greatly increasing the cargo capacity of liquid carbon dioxide, and having good economic efficiency.

[0018] 3. When the CO2 transport ship returns to the loading port, the liquid ammonia fuel in the combined storage tank will keep the CO2 storage tank at a relatively low temperature. When refilling with carbon dioxide, the CO2 storage tank does not need to be pre-cooled, which simplifies the loading and unloading process of carbon dioxide cargo and improves the transportation efficiency of carbon dioxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the distribution of combined storage tanks on a ship;

[0020] Figure 2 Cross-sectional view of a single combined storage compartment;

[0021] Figure 3 System diagram of the present invention;

[0022] In the attached figure: 1. CO2 storage tank; 2. transfer pump; 3. booster pump; 4. condenser; 5. cylinder jacket water heater; 6. gas compressor; 7. expansion valve; 8. fuel storage 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 and embodiments.

[0024] A combined storage tank for ammonia fuel and cargo of a CO2 carrier, such as Figure 1 , Figure 2 and 3 As shown, it includes: a CO2 storage tank 1, a transfer pump 2, a booster pump 3, a condenser 4, a cylinder jacket water heater 5, a gas compressor 6, an expansion valve 7, and a fuel storage tank 8.

[0025] The system of the present invention is applied to a liquefied carbon dioxide transport ship powered by liquid ammonia fuel. The CO2 storage tank 1 is placed in the cargo hold, i.e., the fuel storage tank 8, and an insulation layer is provided outside the storage tank; there are three fuel storage tanks 8, which are filled with liquid ammonia fuel and an insulation layer is provided outside the tank; the combined storage tank is composed of a CO2 storage tank 1 and a fuel storage tank 8. The combined storage tank is arranged under the deck; the transfer pump 2, the booster pump 3, the condenser 4, and the cylinder jacket water heater 5 are connected in sequence through pipelines, and the final pipeline leads to the ship's main engine to form an ammonia fuel supply system. Among them, the transfer pump 2 is installed in the fuel storage tank 8, and the transfer pump 2 is used to transfer the liquid ammonia fuel in the fuel storage tank 8; the booster pump 3 is used to pressurize the liquid ammonia fuel in the pipeline; the condenser 4 is used to heat the pressurized liquid ammonia fuel with the refrigerant in the condenser 4; the cylinder jacket water heater 5 is used to heat the liquid ammonia fuel to the supply temperature to meet the intake temperature of the ship's main engine for use by the ship's main engine. The CO2 storage tank 1, gas compressor 6, condenser 4, and expansion valve 7 are connected in sequence through pipelines to form a carbon dioxide BOG reliquefaction processing system. The gas compressor 6 is used to compress the carbon dioxide BOG; and the expansion valve 7 is used to throttle and reduce the pressure of the liquefied liquid carbon dioxide.

[0026] During the navigation of the ship, the liquid ammonia fuel in the fuel storage tank 8 is transferred out of the fuel storage tank 8 by the transfer pump 2, and then the booster pump 3 is used to pressurize the liquid ammonia fuel in the pipeline. The pressurized liquid ammonia fuel exchanges heat with the refrigerant in the condenser 4, and then enters the cylinder jacket water heater 5. The cylinder jacket water heater 5 heats the liquid ammonia fuel to the supply temperature to meet the intake temperature of the ship's main engine for use by the ship's main engine.

[0027] Due to the temperature difference between the external environment and the CO2 storage tank 1, carbon dioxide BOG is inevitably generated. The external environment temperature of the ship during navigation is designed according to the working condition of 45℃. In the traditional semi-cold and semi-pressurized C-type storage tank, the temperature difference between liquid carbon dioxide and the external environment is as high as 94℃. Figure 2 and Figure 3 As shown, the present invention cleverly combines the fuel tank and the cargo tank, and directly stores the liquid ammonia fuel in the cargo tank where the CO2 storage tank 1 is placed, so that the CO2 storage tank 1 is immersed in the liquid ammonia fuel, providing a good external environment for the storage of carbon dioxide. In the present invention, since the temperature of liquid ammonia under atmospheric pressure is -33.6°C, the temperature difference between the CO2 storage tank 1 and the external environment (i.e., liquid ammonia, -33.6°C) is reduced to 15.4°C, so the temperature difference between the CO2 storage tank 1 and the external environment is significantly reduced, and the CO2 storage tank 1 does not need to be provided with a thicker insulation layer, which can significantly reduce the evaporation rate of carbon dioxide BOG, thereby reducing the manufacturing cost.

[0028] The present invention cleverly combines the fuel tank with the cargo tank, and uses the combined storage tank to store liquid ammonia fuel and liquid carbon dioxide at the same time. The ship does not need to set up a large fuel tank separately, which greatly increases the space of the ship's cargo tank, and stores the liquid ammonia fuel in the unused space between the CO2 storage tank 1 and the cargo tank, thereby improving the utilization rate of the ship's cargo tank space. The present invention can greatly increase the cargo capacity of liquid carbon dioxide, improve the operating efficiency of the ship, and has good economic efficiency.

[0029] Furthermore, in order to solve the storage problem of liquid ammonia fuel on ships, the present invention stores the liquid ammonia fuel in a fuel storage tank 8, and an insulation layer is provided outside the tank to reduce the evaporation of the liquid ammonia.

[0030] In the carbon dioxide BOG reliquefaction treatment system, the carbon dioxide BOG generated in the CO2 storage tank 1 enters the gas compressor 6 through a pipeline. The gas compressor 6 compresses the BOG to a higher temperature and pressure, and then enters the condenser 4 to exchange heat with liquid ammonia. The BOG is cooled and liquefied, and then the liquid carbon dioxide is decompressed by the expansion valve 7 and flows back to the CO2 storage tank 1.

[0031] The ship consumes liquid ammonia fuel in the combined storage tank when sailing. Even if part of the CO2 storage tank 1 is above the liquid ammonia level as the liquid ammonia fuel is used, the temperature of the liquid ammonia BOG in the combined storage tank is still close to -33.6°C, so the temperature difference between the CO2 storage tank 1 and the environment is still very small. Therefore, as the liquid ammonia fuel is consumed, the temperature difference between carbon dioxide and the external environment will basically not change and remain at 15.4°C, so there is always a small carbon dioxide BOG evaporation rate in the CO2 storage tank 1.

[0032] When a traditional CO2 transport ship returns to the loading port for the next loading, the CO2 storage tank 1 will return to normal temperature. When the empty CO2 storage tank 1 is refilled with low-temperature liquid carbon dioxide, the tank body needs to be precooled in advance to avoid thermal stress caused by filling the CO2 storage tank 1 with carbon dioxide without precooling. The present invention places the CO2 storage tank 1 in liquid ammonia fuel. When the CO2 transport ship returns to the loading port for the next loading, the CO2 storage tank 1 can maintain a low temperature because some liquid ammonia fuel will remain in the combined storage cabin. Therefore, the CO2 storage tank 1 does not need to be precooled, which can simplify the filling procedure during carbon dioxide transportation and improve the transportation efficiency of carbon dioxide.

[0033] During the voyage, the ship burns liquid ammonia fuel and consumes liquid ammonia fuel in three combined storage tanks at the same time, and ensures that the consumption of liquid ammonia fuel in each combined storage tank is equal. Taking the route from China to Iceland as an example, due to the long route when the ship transports carbon dioxide, the demand for ammonia fuel is very large. A large amount of liquid ammonia fuel is stored on the ship. When transporting carbon dioxide from China to Iceland, there will be more fuel left in the combined storage tank. Therefore, the temperature difference between liquid carbon dioxide and the external environment in this route remains basically unchanged, and the CO2 storage tank 1 has a smaller evaporation rate of carbon dioxide BOG.

[0034] During the voyage of the ship, the BOG generated by the CO2 storage tank 1 is reliquefied through the reliquefaction treatment system, and the liquid ammonia fuel is used as the cold source of the condenser 4, and the cold energy of the liquid ammonia is used to reliquefy the carbon dioxide BOG. ​​Since the temperature of the liquid ammonia is very low, which is similar to the temperature of the liquid carbon dioxide, the cold energy of the liquid ammonia can significantly reduce the energy consumption of the BOG reliquefaction treatment system.

[0035] In order to further reduce the power consumption of the reliquefaction treatment system, the present invention can reliquefy the generated BOG in an intermittent treatment manner. When the pressure of BOG in the CO2 storage tank 1 is lower than the set lower limit, the BOG reliquefaction treatment system stops working, and when the pressure of BOG in the CO2 storage tank 1 is higher than the set upper limit, the BOG reliquefaction treatment system restarts working.

[0036] The liquid ammonia fuel in the present invention is stored in the unused space between the CO2 storage tank 1 and the cargo hold. As the ammonia fuel is burned, the liquid level of the liquid ammonia fuel will change. However, no matter how the liquid level of the liquid ammonia fuel changes, since the CO2 storage tank 1 is provided in the combined storage compartment, Figure 3 As shown, the free liquid surface of liquid ammonia is very small, and the impact on the stability of the ship is negligible, which fully meets the requirements of ship stability.

[0037] In the present invention, three combined storage compartments are arranged on the ship, but in fact the number of combined storage compartments can be appropriately increased or decreased according to the length of the ship.

[0038] The above describes a specific implementation mode of the present invention by taking a combined storage tank as an example. All cargo tanks in a CO2 transport ship apply the cargo tank of the present invention, and the implementation mode is the same as that described above.

[0039] The above is only a preferred embodiment of the present invention. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A combined storage tank for ammonia fuel and cargo of a CO2 transport ship, characterized by: The present invention comprises a CO2 storage tank (1), a transfer pump (2), a booster pump (3), a condenser (4), a cylinder jacket water heater (5), a gas compressor (6), an expansion valve (7), and a fuel storage tank (8); The CO2 storage tank (1) is placed in the fuel storage tank (8), and a heat-insulating layer is provided outside the CO2 storage tank (1); the fuel storage tank (8) contains liquid ammonia fuel; the combined storage tank is composed of the CO2 storage tank (1) and the fuel storage tank (8); the combined storage tank is arranged under the deck, The transfer pump (2), the booster pump (3), the condenser (4), and the jacket water heater (5) are connected in sequence through pipelines, and the pipelines finally lead to the main engine of the ship. The CO2 storage tank (1), the gas compressor (6), the condenser (4), and the expansion valve (7) are connected in sequence through pipelines. The BOG generated in the CO2 storage tank (1) enters the gas compressor (6) through a pipeline. The gas compressor (6) compresses the BOG to a high temperature and a high pressure. The BOG then enters the condenser (4) to exchange heat with liquid ammonia. The BOG is cooled and liquefied. The carbon dioxide is then decompressed by the expansion valve (7) and flows back to the CO2 storage tank (1).

2. A combined storage tank for ammonia fuel and cargo for a CO2 transport ship according to claim 1, characterized in that: The fuel storage tank (8) is provided with a heat-insulating layer outside to reduce the evaporation of liquid ammonia.

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