LNG ship hybrid power system based on fuel oil and natural gas hydrate

Abstract

The utility model discloses an LNG ship hybrid power system based on fuel oil and natural gas hydrate. The LNG ship hybrid power system comprises an engine selection control unit, an engine, a fuel oil supply unit and a natural gas hydrate supply unit. The engine selection control unit is connected with the engine, the fuel oil supply unit and the natural gas hydrate supply unit, and the engine selection control unit selects the fuel oil supply unit to provide fuel for the engine or selects the natural gas hydrate supply unit to provide fuel for the engine according to the load change of the engine; the fuel supply unit is connected with an engine through a fuel stop valve, and the fuel stop valve is controlled by the engine selection control unit. The natural gas hydrate supply unit is connected with an engine through a natural gas stop valve, and the natural gas stop valve is controlled by the engine selection control unit. The natural gas hydrate releases gaseous natural gas after being heated, and the gaseous natural gas is provided for an engine as fuel.

Description

Technical Field

[0001] This application belongs to the field of liquefied natural gas ship propulsion technology, specifically referring to an LNG ship hybrid power system based on fuel oil and natural gas hydrate. Background Technology

[0002] Since the International Maritime Organization (IMO) imposed sulfur caps, increasing the proportion of liquefied natural gas (LNG) as ship fuel has received significant attention from major shipping nations and relevant regulatory bodies worldwide. According to the latest IMO forecast, by 2030, LNG will account for 30% of ship engine fuel. Clearly, planning a fuel supply system adapted to the ship's structural characteristics and the thermophysical properties of LNG is crucial. Current research shows that for most ships operating on inland waterways, compressed natural gas (CNG) systems are typically installed to maintain stable fuel supply pressure in response to rapid load changes during navigation in narrow waterways. However, since approximately 0.8% of LNG in storage tanks produces boil-off gas (BOG) daily, two core technical challenges remain: how to safely manage BOG and maintain CNG system pressure.

[0003] Current research reveals three main methods for handling boil-off gas (BOG): First, using a reverse Brayton cycle-based refrigeration system to liquefy the high-temperature BOG into LNG; second, supplying BOG to a dual-fuel engine via a dedicated gas supply line for combustion, with any remaining BOG directly fed into the Gas Combustion Unit (GCU); and third, using a multi-stage compressor to compress BOG into high-pressure CNG (20-25 MPa) and storing it in high-pressure cylinders. For commercial LNG carriers in my country currently undergoing "oil-to-gas" conversion, the third method is primarily employed, effectively utilizing BOG while simultaneously returning it to the fuel system as CNG, maintaining the pressure of the fuel supply system. However, pressurizing low-pressure BOG to 25 MPa CNG requires a multi-stage compressor on board, and storing 25 MPa CNG in vessels also poses significant safety risks.

[0004] Therefore, current LNG-powered vessels suffer from several drawbacks. Firstly, the CNG subsystem within the propulsion system operates at high pressure, necessitating the installation of multi-stage compressors on board. Secondly, the flammability and explosiveness of high-pressure natural gas, coupled with the simultaneous presence of LNG and high-pressure CNG storage tanks, compromises the safety and stability of vessel operations. Furthermore, the management of BOG (Boiled Air Gaseous) generated from LNG on small and medium-sized inland waterway vessels is inadequate, failing to fully utilize the low-temperature advantage of BOG in the design and planning of the fuel subsystem. Utility Model Content

[0005] To overcome the shortcomings of the prior art, this application provides an LNG ship hybrid power system based on fuel oil and natural gas hydrate, which converts BOG in the storage tank into natural gas hydrate for fuel utilization.

[0006] This utility model provides an LNG ship hybrid power system based on fuel oil and natural gas hydrate, the hybrid power system including: an engine selection control unit, an engine, a fuel oil supply unit and a natural gas hydrate supply unit;

[0007] The engine selection control unit is connected to the engine, the fuel supply unit, and the natural gas hydrate supply unit. The engine selection control unit selects either the fuel supply unit or the natural gas hydrate supply unit to supply fuel to the engine according to the change in engine load.

[0008] The fuel supply unit is connected to the engine via a fuel shut-off valve, which is controlled by the engine selection control unit.

[0009] The natural gas hydrate supply unit is connected to the engine via a natural gas shut-off valve, which is controlled by the engine selection control unit.

[0010] The natural gas hydrate supply unit includes a liquefied natural gas (LNG) storage tank, a natural gas hydrate storage tank, and a natural gas pipeline. The LNG storage tank and the natural gas hydrate storage tank are connected by a first heat exchanger. The evaporated gas formed by the LNG in the LNG storage tank enters the natural gas hydrate storage tank through the first heat exchanger. The evaporated gas undergoes wet adsorption by a metal-organic framework in the natural gas hydrate storage tank to form natural gas hydrate. The natural gas hydrate is heated to release gaseous natural gas, which is then supplied to the engine as fuel.

[0011] Furthermore, according to the LNG ship hybrid power system based on fuel oil and natural gas hydrate provided in this embodiment, the natural gas hydrate supply unit further includes a natural gas buffer, the input end of which is connected to the first output end of the natural gas hydrate storage tank, and the output end of which is connected to the natural gas shut-off valve.

[0012] Furthermore, according to the LNG ship hybrid power system based on fuel oil and natural gas hydrate provided in this embodiment, the natural gas hydrate supply unit further includes a second heat exchanger, the input end of which is connected to the second output end of the liquefied natural gas storage tank, and the output end of which is connected to the input end of the natural gas buffer.

[0013] Furthermore, according to the LNG ship hybrid power system based on fuel oil and natural gas hydrate provided in this embodiment, a first shut-off valve, a liquefied natural gas circulation pump, and a second shut-off valve are sequentially connected between the input end of the second heat exchanger and the second output end of the liquefied natural gas storage tank; a third shut-off valve is connected between the output end of the second heat exchanger and the input end of the natural gas buffer.

[0014] Furthermore, according to the LNG ship hybrid power system based on fuel oil and natural gas hydrate provided in this embodiment, the first heat exchanger is connected to the first output end of the liquefied natural gas storage tank, and a fourth shut-off valve is connected between the first heat exchanger and the first output end of the liquefied natural gas storage tank; a fifth shut-off valve is connected between the output end of the first heat exchanger and the first input end of the natural gas hydrate storage tank.

[0015] A sixth shut-off valve is connected between the first output end of the natural gas hydrate storage tank and the input end of the natural gas buffer.

[0016] Furthermore, according to the LNG ship hybrid power system based on fuel oil and natural gas hydrate provided in this embodiment, the end cap of the natural gas hydrate storage tank is provided with a fresh water atomizing nozzle, the fresh water atomizing nozzle is connected to a water supply solenoid valve, and the water supply solenoid valve is connected to a fresh water pipeline.

[0017] The natural gas hydrate storage tank is surrounded by multiple layers of cooling coils for cooling the natural gas hydrate inside the tank.

[0018] The natural gas hydrate storage tank is equipped with a top water spraying lysis reinforcement plate and a bottom water spraying lysis reinforcement plate at the top and bottom of the tank containing the natural gas hydrate, respectively.

[0019] The natural gas hydrate storage tank is equipped with heat transfer fins for heating the natural gas hydrate and releasing gaseous natural gas.

[0020] The fifth shut-off valve connected to the first input end of the natural gas hydrate storage tank is a liquid supply solenoid valve, and the sixth shut-off valve connected to the first output end of the natural gas hydrate storage tank is a gas supply solenoid valve.

[0021] The natural gas hydrate storage tank also includes a second input terminal and a second output terminal. The second output terminal of the natural gas hydrate storage tank is connected to the first channel of a three-way solenoid valve. The second channel of the three-way solenoid valve is connected to a second liquid supply solenoid valve. The other end of the second liquid supply solenoid valve is connected to the second input terminal of the natural gas hydrate storage tank. The third channel of the three-way solenoid valve is connected to a third liquid supply solenoid valve. The other end of the third liquid supply solenoid valve is connected to the first input terminal of the natural gas hydrate storage tank.

[0022] Furthermore, according to the LNG ship hybrid power system based on fuel oil and natural gas hydrate provided in this embodiment, a first pressure reducing valve is also connected between the output end of the natural gas buffer and the natural gas shut-off valve.

[0023] Furthermore, in the LNG ship hybrid power system based on fuel oil and natural gas hydrate provided in this embodiment, a natural gas mixer and a natural gas injector are connected in sequence between the natural gas shut-off valve and the engine.

[0024] Furthermore, according to the LNG ship hybrid power system based on fuel oil and natural gas hydrate provided in this embodiment, the engine selection control unit includes an engine electronic control unit and an engine load detector;

[0025] The input terminal of the engine load detector is connected to the engine, and the output terminal of the engine load detector is connected to the engine electronic control unit;

[0026] The engine electronic control unit is connected to the natural gas shut-off valve and the fuel shut-off valve.

[0027] Furthermore, according to the LNG ship hybrid power system based on fuel oil and natural gas hydrate provided in this embodiment, the fuel oil supply unit includes a fuel oil storage tank and a fuel oil pipeline;

[0028] The output end of the fuel tank is connected to the seventh shut-off valve, the other end of the seventh shut-off valve is connected to the input end of the fuel supply pump, the output end of the fuel supply pump is connected to the eighth shut-off valve, the other end of the eighth shut-off valve is connected to the input end of the fuel booster pump, the input end of the fuel booster pump is also connected to the engine selection control unit, the output end of the fuel booster pump is connected to the fuel shut-off valve, and the other end of the fuel shut-off valve is connected to the engine.

[0029] The beneficial effects of this utility model are as follows: The LNG ship hybrid power system based on fuel oil and natural gas hydrate provided in this application offers a new natural gas hydrate supply unit. It allows the evaporated gas formed from liquefied natural gas in the liquefied natural gas storage tank to enter the natural gas hydrate storage tank through a first heat exchanger. The evaporated gas then undergoes wet adsorption via a metal-organic framework (MOF) within the natural gas hydrate storage tank to form natural gas hydrate. When the ship's engine requires natural gas as fuel, the natural gas hydrate is heated to release gaseous natural gas, which is then supplied to the engine as fuel. The wet adsorption via the MOF utilizes the cooling energy of the BOG released from the LNG storage tank to maintain the temperature at which the storage system can form natural gas hydrate (NGH) through wet adsorption on the adsorbent using BOG at a lower pressure, thereby increasing the natural gas storage density within the storage system at a lower storage pressure. Furthermore, the system process utilizes the cooling energy of BOG for cooling and forms NGH through wet adsorption at a lower pressure, which is then used to provide fuel for the ship's propulsion system during rapid load changes. Because high-density NGH is formed under lower pressure, the pressure in the storage system is reduced, thus improving the safety of ship navigation. Attached Figure Description

[0030] The technical solution and other beneficial effects of this application will become apparent from the following detailed description of specific embodiments in conjunction with the accompanying drawings.

[0031] Figure 1 This is a schematic diagram of the LNG ship hybrid power system based on fuel oil and natural gas hydrates provided in this embodiment.

[0032] Figure 2 This is a schematic diagram of the structure of the natural gas hydrate storage tank provided in this embodiment.

[0033] The components in the diagram are labeled as follows: Engine Electronic Control Unit 1, Engine Load Detector 2, Fuel Booster Pump 3, Fuel Cut-off Valve 4, Eighth Cut-off Valve 5, Fuel Supply Pump 6, Seventh Cut-off Valve 7, Fuel Storage Tank 8, Natural Gas Mixer 9, Natural Gas Injector 10, Engine 11, Natural Gas Cut-off Valve 12, First Pressure Reducing Valve 13, Natural Gas Buffer 14, Third Cut-off Valve 15, Second Heat Exchanger 16, Second Cut-off Valve 17, Liquefied Natural Gas Circulation Pump 18, First Cut-off Valve 19, Sixth Cut-off Valve 20, Fifth Cut-off Valve 21, First Heat Exchanger 22, Fourth Cut-off Valve 23, Liquefied Natural Gas Storage Tank 24, Natural Gas Hydrate Storage Tank 25, Water Supply Solenoid Valve 26, Three-Way Solenoid Valve 27, Second Liquid Supply Solenoid Valve 28, Third Liquid Supply Solenoid Valve 29, Cooling Coil 252, End Cap 254, Fresh Water Atomizing Nozzle 255, Bottom Water Spraying Divided Reinforcement Plate 256, Top Water Spraying Divided Reinforcement Plate 257, Heat Transfer Fins 258. Detailed Implementation

[0034] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0035] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0036] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0037] Currently constructed LNG ships suffer from several issues. Firstly, the CNG subsystem within the propulsion system operates at high pressure, requiring multi-stage compressors. Secondly, the flammability and explosiveness of high-pressure natural gas necessitate the simultaneous presence of LNG and high-pressure CNG storage tanks on board, impacting operational safety and stability. Furthermore, the management of BOG (Boiled Gas) generated from LNG on small and medium-sized inland waterway vessels is inadequate, failing to fully utilize the low-temperature advantage of BOG in the design and planning of fuel subsystems.

[0038] To address this, researchers have proposed using porous media to adsorb BOG (BoG) to create Absorbed Natural Gas (ANG) as a substitute for CNG, and have simultaneously conducted research on BOG adsorption and storage on activated carbon. However, due to the low pressure of BOG, and the fact that ANG typically requires pressures above 4 MPa to achieve high energy storage density, a compressor is needed on board ships to pressurize the BOG when using ANG for storage. Clearly, using ANG to adsorb BOG and construct a fuel supply system for ships also presents significant drawbacks. Meanwhile, the storage of natural gas as NGH has also attracted researchers' attention. Researchers have found that by adsorbing natural gas onto porous media with a certain water content, hydrates can form under a wider range of temperature and pressure conditions than in the methane / water system, increasing the adsorption capacity of the adsorbent for methane. Furthermore, the stored natural gas can be released by depressurization. The study found that the conditions for methane to form hydrates on MIL-101, ZIF-8, and activated carbon with a certain water content are -1℃ to 2℃ and 6 MPa to 7 MPa. According to the phase diagram of hydrate formation, if the system temperature can be lowered, the pressure for hydrate formation will be reduced.

[0039] LNG typically has a temperature of -162°C, while LNG storage tanks are designed to operate at pressures less than 1 MPa. The temperature of the bound gas (BOG) produced during LNG evaporation is below the critical temperature of methane, which is -83°C. Therefore, the cooling capacity of the BOG generated by LNG from ships can be used to cool the fuel storage system. At temperatures matched to extremely low evaporation pressures, non-volatile organic compounds (NGH) are formed through the adsorption of methane on metal-organic frameworks (MOFs), which have better adsorption properties than activated carbon. This improves the energy density of the storage system and enhances its operational safety.

[0040] Based on the characteristics of large volume and low temperature of BOG generated from marine LNG, and taking into account the structure and navigation characteristics of LNG ships, this application proposes to form NGH by wet adsorption of methane using metal-organic framework materials (MOFs) at low temperature and low storage pressure. This NGH can then replace the high-pressure CNG fuel supply subsystem in the fuel system, thereby stabilizing the fuel supply of the ship's engine under rapid load changes and improving the safety and economy of ship navigation.

[0041] The embodiments of this application will now be further described in conjunction with the accompanying drawings and specific implementation details.

[0042] Figure 1 This is a schematic diagram of the structure of an LNG ship hybrid power system based on fuel oil and natural gas hydrates, provided in an embodiment of this application.

[0043] like Figure 1As shown, the hybrid power system includes: an engine selection control unit, an engine 11, a fuel supply unit, and a natural gas hydrate supply unit; the engine selection control unit is connected to the engine 11, the fuel supply unit, and the natural gas hydrate supply unit, and selects either the fuel supply unit or the natural gas hydrate supply unit to supply fuel to the engine 11 according to changes in the load of the engine 11; the fuel supply unit is connected to the engine 11 via a fuel shut-off valve 4, and the fuel shut-off valve 4 is controlled by the engine selection control unit; the natural gas hydrate supply unit is connected to the engine 11 via a natural gas shut-off valve 12. The engine 11 is connected, and the natural gas shut-off valve 12 is controlled by the engine selection control unit. The natural gas hydrate supply unit includes a liquefied natural gas storage tank 24, a natural gas hydrate storage tank 25, and a natural gas pipeline. The liquefied natural gas storage tank 24 and the natural gas hydrate storage tank 25 are connected by a first heat exchanger 22. The evaporated gas formed by the liquefied natural gas in the liquefied natural gas storage tank 24 enters the natural gas hydrate storage tank 25 through the first heat exchanger 22. The evaporated gas undergoes wet adsorption by a metal-organic framework in the natural gas hydrate storage tank 25 to form natural gas hydrate. The natural gas hydrate is heated to release gaseous natural gas, which is then supplied to the engine 11 as fuel.

[0044] Specifically, in this embodiment, when the LNG ship is frequently used, the engine 11 is connected to the fuel supply unit to use fuel oil; when the ship is sailing at a constant speed or needs to change its speed quickly, the engine 11 is connected to the natural gas hydrate supply unit to use natural gas as fuel, so as to improve the stability of the power system operation.

[0045] The specific implementation scheme includes: after acquiring information on the LNG vessel's load and navigation conditions, the engine selection control unit outputs adjustment signals to control the start and stop of the fuel supply unit and the natural gas hydrate supply unit. In the fuel supply mode where the vessel frequently uses its engines, the fuel shut-off valve 4 is opened, the natural gas shut-off valve 12 is closed, and the fuel pipeline is connected to the engine 11, thereby supplying fuel to the engine 11 injectors. In the vessel's constant speed navigation or rapid speed change mode, the fuel shut-off valve 4 is closed, the natural gas shut-off valve 12 is opened, and the natural gas pipeline is connected to the engine 11, switching the engine 11 to natural gas operating mode.

[0046] like Figure 1As shown, the LNG ship hybrid power system based on fuel oil and natural gas hydrate provided in this embodiment includes a natural gas buffer 14 in the natural gas hydrate supply unit. The input end of the natural gas buffer 14 is connected to the first output end of the natural gas hydrate storage tank 25, and the output end of the natural gas buffer 14 is connected to the natural gas shut-off valve 12. The natural gas buffer 14 is used to receive the natural gas output from the natural gas hydrate supply unit, which can provide a stable natural gas fuel to the engine 11 and improve the combustion stability of the engine 11.

[0047] The natural gas hydrate supply unit further includes a second heat exchanger 16. The input end of the second heat exchanger 16 is connected to the second output end of the liquefied natural gas storage tank 24, and the output end of the second heat exchanger 16 is connected to the input end of the natural gas buffer 14. The second heat exchanger 16 is used to directly heat the liquefied natural gas output from the second output end of the liquefied natural gas storage tank 24 to release gaseous natural gas, which is then output to the natural gas buffer 14 to provide fuel for the engine 11.

[0048] The input end of the second heat exchanger 16 is connected in sequence to the second output end of the liquefied natural gas storage tank 24 via a first shut-off valve 19, a liquefied natural gas circulation pump 18, and a second shut-off valve 17; the output end of the second heat exchanger 16 is connected to the input end of the natural gas buffer 14 via a third shut-off valve 15.

[0049] In this embodiment, both the first heat exchanger 22 and the second heat exchanger 16 are ambient temperature heat exchangers.

[0050] The first heat exchanger 22 is connected to the first output end of the liquefied natural gas storage tank 24, and a fourth shut-off valve 23 is connected between the first heat exchanger 22 and the first output end of the liquefied natural gas storage tank 24; a fifth shut-off valve 21 is connected between the output end of the first heat exchanger 22 and the first input end of the natural gas hydrate storage tank 25; and a sixth shut-off valve 20 is connected between the first output end of the natural gas hydrate storage tank 25 and the input end of the natural gas buffer 14.

[0051] The output end of the natural gas buffer 14 is also connected to the natural gas shut-off valve 12 via a first pressure reducing valve 13.

[0052] The natural gas shut-off valve 12 is connected in sequence to the engine 11 via a natural gas mixer 9 and a natural gas injector 10.

[0053] The engine selection control unit includes an engine electronic control unit 1 and an engine load detector 2; the input terminal of the engine load detector 2 is connected to the engine 11, and the output terminal of the engine load detector 2 is connected to the engine electronic control unit 1; the engine electronic control unit 1 is connected to the natural gas shut-off valve 12 and the fuel shut-off valve 4.

[0054] The fuel supply unit includes a fuel tank 8 and a fuel pipeline; the output end of the fuel tank 8 is connected to a seventh shut-off valve 7, the other end of the seventh shut-off valve 7 is connected to the input end of the fuel supply pump 6, the output end of the fuel supply pump 6 is connected to an eighth shut-off valve 5, the other end of the eighth shut-off valve 5 is connected to the input end of the fuel booster pump 3, the input end of the fuel booster pump 3 is also connected to the engine 11 selection control unit, the output end of the fuel booster pump 3 is connected to a fuel shut-off valve 4, and the other end of the fuel shut-off valve 4 is connected to the engine 11.

[0055] In this embodiment, the first shut-off valve 19 to the seventh shut-off valve 7 can all be configured as solenoid valves. The fuel shut-off valve 4 and the natural gas shut-off valve 12 can both be configured as solenoid valves.

[0056] Figure 2 This is a schematic diagram of the structure of the natural gas hydrate storage tank 25 provided in this embodiment.

[0057] like Figure 2 As shown, the end cap 254 of the natural gas hydrate storage tank 25 is provided with a fresh water atomizing nozzle 255, which is connected to a water supply solenoid valve 26, and the water supply solenoid valve 26 is connected to a fresh water pipeline.

[0058] The natural gas hydrate storage tank 25 is surrounded by a multi-layer cooling coil 252 for cooling the natural gas hydrate inside the natural gas hydrate storage tank 25.

[0059] The natural gas hydrate storage tank 25 is equipped with a top water spraying lysis reinforcement plate 257 and a bottom water spraying lysis reinforcement plate 256 at the top and bottom of the natural gas hydrate inside the tank.

[0060] The natural gas hydrate storage tank 25 is equipped with heat transfer fins 258 for heating the natural gas hydrate and releasing gaseous natural gas.

[0061] The fifth shut-off valve 21 connected to the first input end of the natural gas hydrate storage tank 25 is a liquid supply solenoid valve, and the sixth shut-off valve 20 connected to the first output end of the natural gas hydrate storage tank 25 is a gas supply solenoid valve.

[0062] The natural gas hydrate storage tank 25 also includes a second input terminal and a second output terminal. The second output terminal of the natural gas hydrate storage tank 25 is connected to the first channel of a three-way solenoid valve 27, and the second channel of the three-way solenoid valve 27 is connected to a second liquid supply solenoid valve 28. The other end of the second liquid supply solenoid valve 28 is connected to the second input terminal of the natural gas hydrate storage tank 25. The third channel of the three-way solenoid valve 27 is connected to a third liquid supply solenoid valve 29, and the other end of the third liquid supply solenoid valve 29 is connected to the first input terminal of the natural gas hydrate storage tank 25. The second output terminal of the natural gas hydrate storage tank 25 can guide the naturally evaporated natural gas inside the tank through the three-way solenoid valve 27 into the tank via the first and second input terminals for further cooling and adsorption.

[0063] In this embodiment, in the natural gas hydrate storage tank 25, based on the properties of LNG vaporized gas (BOG) in ships, and considering the preparation cost, adsorption capacity, structural stability, and thermal conductivity of the BOG, MOFs suitable for the characteristics of ship BOG were selected. Furthermore, it was proposed to arrange honeycomb-shaped heat transfer fins 258 in the NGH adsorption bed and to adopt enhanced heat and mass transfer measures by adding expanded graphite (ENG) to the MOFs for molding and curing, thereby reducing the pressure for NGH formation and increasing the energy density of the NGH system.

[0064] Therefore, in this embodiment, the cooling capacity of LNG vaporized gas (BOG) is used to form an NGH storage system at a pressure not exceeding 1 MPa while reducing the storage system temperature. The storage pressure is only 4% of the CNG storage tank pressure, which improves the system's safety and the economy of ship operation.

[0065] Combination Figure 1 and Figure 2 In this embodiment, under the fuel supply mode of frequent ship vehicle use, the fuel shut-off valve 4 is turned on, the natural gas shut-off valve 12 is turned off, the seventh shut-off valve 7, the eighth shut-off valve 5 and the fuel shut-off valve 4 are all energized and turned on, the fuel pipeline is connected to the engine 11, and at the same time the fuel supply pump 6 and the fuel booster pump 3 are energized and start working, thereby supplying fuel to the injectors of the engine 11.

[0066] In constant speed navigation or rapid speed change mode, the fuel shut-off valve 4 is closed, the natural gas shut-off valve 12 is opened, the seventh shut-off valve 7, the eighth shut-off valve 5 and the fuel shut-off valve 4 are all de-energized and closed, the natural gas pipeline is connected to the engine 11, and the natural gas in the natural gas buffer 14 enters the natural gas mixer 9 and the natural gas injector 10 after passing through the first pressure reducing valve 13, injecting the natural gas into the engine 11, and the engine 11 switches to natural gas operating mode.

[0067] Specifically, in this embodiment, the gaseous natural gas supplied by the natural gas hydrate supply unit includes two parts: natural gas released from the LNG inside the liquefied natural gas storage tank 24 after being heated and vaporized by the second heat exchanger 16, and natural gas released from the natural gas hydrate storage tank 25 after heating. The two-part gas supply scheme includes:

[0068] When the LNG vessel is sailing at a constant speed, the engine 11 consumes natural gas released from the LNG inside the LNG storage tank 24 after being heated and vaporized by the second heat exchanger 16. The operating mode is as follows: the LNG in the LNG storage tank 24 is transferred by the LNG circulation pump 18, vaporized by the second heat exchanger 16, and enters the natural gas buffer 14. After being depressurized by the first pressure reducing valve 13, it enters the natural gas mixer 9 and the natural gas injector 10 in sequence, thereby providing fuel for the engine 11.

[0069] When the LNG vessel's speed changes rapidly, the sixth shut-off valve 20 is energized and opens, causing the wall of the natural gas hydrate storage tank 25 to heat up and the natural gas stored in the tank to be rapidly released into the natural gas buffer 14, thereby stabilizing the pressure of the natural gas supply system and ensuring the fuel demand of the engine 11 when the load changes rapidly.

[0070] In summary, this embodiment provides an LNG ship hybrid power system based on fuel oil and natural gas hydrates. It proposes the formation of natural gas hydrates (NGH) through the adsorption of low-temperature, low-pressure BOG on MOFs, thereby replacing the natural gas hydrate supply unit of the high-pressure CNG fuel supply subsystem in the fuel system. The evaporated gas formed from liquefied natural gas in liquefied natural gas storage tank 24 can enter the natural gas hydrate storage tank 25 through the first heat exchanger 22. Within the natural gas hydrate storage tank 25, the evaporated gas undergoes wet adsorption via a metal-organic framework to form natural gas hydrates. When the ship's engine 11 requires natural gas as fuel, the natural gas hydrates are heated to release gaseous natural gas, which is then supplied to the engine 11 as fuel. The wet adsorption via the metal-organic framework utilizes the cooling energy of the BOG released from the LNG storage tank to maintain the temperature at which the storage system can achieve the wet adsorption of BOG on the adsorbent to form natural gas hydrates (NGH) at a lower pressure, thus increasing the natural gas storage density within the storage system at a lower storage pressure. Furthermore, the system utilizes the cooling capacity of BOG (Bottle-Oxide Gas) to form NGH (Natural Gas Glucose) through wet adsorption at lower pressure. This NGH is then heated and released to fuel the ship's propulsion system during rapid load changes. Because high-density NGH is formed at lower pressures, the storage system pressure is reduced, improving the safety of ship navigation.

[0071] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the present invention. Finally, it should be noted that in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0072] The above provides a detailed description of the LNG ship hybrid power system based on fuel oil and natural gas hydrate provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. An LNG ship hybrid power system based on fuel oil and natural gas hydrate, characterized in that, The hybrid power system includes: an engine selection control unit, an engine, a fuel supply unit, and a natural gas hydrate supply unit; The engine selection control unit is connected to the engine, the fuel supply unit, and the natural gas hydrate supply unit. The engine selection control unit selects either the fuel supply unit or the natural gas hydrate supply unit to supply fuel to the engine according to the change in engine load. The fuel supply unit is connected to the engine via a fuel shut-off valve, which is controlled by the engine selection control unit. The natural gas hydrate supply unit is connected to the engine via a natural gas shut-off valve, which is controlled by the engine selection control unit. The natural gas hydrate supply unit includes a liquefied natural gas (LNG) storage tank, a natural gas hydrate storage tank, and a natural gas pipeline. The LNG storage tank and the natural gas hydrate storage tank are connected by a first heat exchanger. The evaporated gas formed by the LNG in the LNG storage tank enters the natural gas hydrate storage tank through the first heat exchanger. The evaporated gas undergoes wet adsorption by a metal-organic framework in the natural gas hydrate storage tank to form natural gas hydrate. The natural gas hydrate is heated to release gaseous natural gas, which is then supplied to the engine as fuel.

2. The LNG ship hybrid power system based on fuel oil and natural gas hydrate according to claim 1, characterized in that, The natural gas hydrate supply unit also includes a natural gas buffer, the input end of which is connected to the first output end of the natural gas hydrate storage tank, and the output end of which is connected to the natural gas shut-off valve.

3. The LNG ship hybrid power system based on fuel oil and natural gas hydrate according to claim 2, characterized in that, The natural gas hydrate supply unit further includes a second heat exchanger, the input end of which is connected to the second output end of the liquefied natural gas storage tank, and the output end of which is connected to the input end of the natural gas buffer.

4. The LNG ship hybrid power system based on fuel oil and natural gas hydrate according to claim 3, characterized in that, The input end of the second heat exchanger is sequentially connected to the second output end of the liquefied natural gas storage tank via a first shut-off valve, a liquefied natural gas circulation pump, and a second shut-off valve; the output end of the second heat exchanger is connected to the input end of the natural gas buffer via a third shut-off valve.

5. The LNG ship hybrid power system based on fuel oil and natural gas hydrate according to any one of claims 2-4, characterized in that, The first heat exchanger is connected to the first output end of the liquefied natural gas storage tank, and a fourth shut-off valve is connected between the first heat exchanger and the first output end of the liquefied natural gas storage tank; a fifth shut-off valve is connected between the output end of the first heat exchanger and the first input end of the natural gas hydrate storage tank. A sixth shut-off valve is connected between the first output end of the natural gas hydrate storage tank and the input end of the natural gas buffer.

6. The LNG ship hybrid power system based on fuel oil and natural gas hydrate according to claim 5, characterized in that, The end cap of the natural gas hydrate storage tank is equipped with a fresh water atomizing nozzle, which is connected to a water supply solenoid valve, and the water supply solenoid valve is connected to a fresh water pipeline. The natural gas hydrate storage tank is surrounded by multiple layers of cooling coils for cooling the natural gas hydrate inside the tank. The natural gas hydrate storage tank is equipped with a top water spraying lysis reinforcement plate and a bottom water spraying lysis reinforcement plate at the top and bottom of the tank containing the natural gas hydrate, respectively. The natural gas hydrate storage tank is equipped with heat transfer fins for heating the natural gas hydrate and releasing gaseous natural gas. The fifth shut-off valve connected to the first input end of the natural gas hydrate storage tank is a liquid supply solenoid valve, and the sixth shut-off valve connected to the first output end of the natural gas hydrate storage tank is a gas supply solenoid valve. The natural gas hydrate storage tank also includes a second input terminal and a second output terminal. The second output terminal of the natural gas hydrate storage tank is connected to the first channel of a three-way solenoid valve. The second channel of the three-way solenoid valve is connected to a second liquid supply solenoid valve. The other end of the second liquid supply solenoid valve is connected to the second input terminal of the natural gas hydrate storage tank. The third channel of the three-way solenoid valve is connected to a third liquid supply solenoid valve. The other end of the third liquid supply solenoid valve is connected to the first input terminal of the natural gas hydrate storage tank.

7. The LNG ship hybrid power system based on fuel oil and natural gas hydrate according to claim 5, characterized in that, A first pressure reducing valve is also connected between the output end of the natural gas buffer and the natural gas shut-off valve.

8. The LNG ship hybrid power system based on fuel oil and natural gas hydrate according to claim 2, characterized in that, The natural gas shut-off valve is connected in sequence to the engine via a natural gas mixer and a natural gas injector.

9. The LNG ship hybrid power system based on fuel oil and natural gas hydrate according to claim 1, characterized in that, The engine selection control unit includes an engine electronic control unit and an engine load detector; The input terminal of the engine load detector is connected to the engine, and the output terminal of the engine load detector is connected to the engine electronic control unit; The engine electronic control unit is connected to the natural gas shut-off valve and the fuel shut-off valve.

10. The LNG ship hybrid power system based on fuel oil and natural gas hydrate according to claim 1, characterized in that, The fuel supply unit includes a fuel storage tank and fuel pipelines; The output end of the fuel tank is connected to the seventh shut-off valve, the other end of the seventh shut-off valve is connected to the input end of the fuel supply pump, the output end of the fuel supply pump is connected to the eighth shut-off valve, the other end of the eighth shut-off valve is connected to the input end of the fuel booster pump, the input end of the fuel booster pump is also connected to the engine selection control unit, the output end of the fuel booster pump is connected to the fuel shut-off valve, and the other end of the fuel shut-off valve is connected to the engine.

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