Marine lng engine gas supply and reliquefaction hybrid system

Abstract

The application discloses a kind of ship LNG engine gas supply and liquefaction composite system, including a for storing natural gas storage tank, a gasifier, a compressor, the storage tank includes a booster pump, a first throttling device, a spiral coil, the booster pump includes an inlet and an outlet, the spiral coil also includes an inlet and an outlet, the inlet of the booster pump is in fluid communication with the storage tank, the outlet of the booster pump, the first throttling device.The advantage of the ship LNG engine gas supply system of the application is: the cold energy generated by LNG vaporization before entering the engine can be used to cool the natural gas in the LNG storage tank, and the flow of natural gas supplied to the engine and the flow of natural gas used for liquefaction can also be dynamically adjusted according to the load of the engine, so that the compressor in the gas supply system can maintain high operating efficiency.

Description

Technical Field

[0001] This invention relates to the field of liquefied natural gas (LNG) application technology in marine engines, and more specifically to a combined LNG supply and reliquefaction system for marine LNG engines. Background Technology

[0002] Natural gas, as a clean energy source, is increasingly being used as fuel for ship engines. However, gaseous natural gas occupies a large space, making it inconvenient to transport and store. Therefore, it is usually liquefied into liquefied natural gas (LNG) through pressurization and cooling and stored in tanks. However, LNG cannot be directly used by engines; it must be converted back into a gaseous state before it can be used. At the same time, there is a significant temperature difference between the low-temperature LNG in the tank and the external environment. After absorbing heat from the outside, some of the LNG will evaporate into a gaseous state, increasing the pressure inside the tank. To solve this technical problem, ship LNG storage tanks must also be equipped with a reliquefaction system to release the heat from the gaseous natural gas and keep it in a low-temperature liquid state for safe operation, resulting in high production costs. Moreover, the operation of the ship's LNG engine gas supply system and reliquefaction system each consumes a large amount of energy, leading to high operating costs. Summary of the Invention

[0003] The present invention mainly addresses the technical problems existing in the prior art, thereby providing a marine LNG engine gas supply and reliquefaction composite system with only one compressor, which can be used for both natural gas reliquefaction and natural gas regasification, has a low cost, and can dynamically adjust the flow rate of natural gas supplied to the engine and the flow rate of natural gas used for reliquefaction according to the engine load, so that the compressor in the gas supply system maintains a high operating efficiency.

[0004] The present invention solves the technical problems existing in the prior art through the following technical solution:

[0005] A combined gas supply and reliquefaction system for a marine LNG engine includes a storage tank for storing natural gas, a vaporizer, and a compressor. The system further includes a booster pump and a gas-liquid separator. The booster pump has an inlet and an outlet. The gas-liquid separator has a liquid interface and a liquid outlet. The liquid interface and the liquid outlet are located near the bottom of the gas-liquid separator, and the gas outlet is located near the top of the gas-liquid separator. The inlet of the booster pump is in fluid communication with the storage tank, and the outlet of the booster pump is in fluid communication with the liquid interface. The liquid outlet, the vaporizer, and the compressor's suction port are sequentially in fluid communication.

[0006] As a preferred technical solution of the present invention, the ship LNG engine gas supply and reliquefaction composite system further includes a three-way valve and a cooler. A spiral coil is installed in the storage tank. The spiral coil also includes an inlet and an outlet. The gas-liquid separator is arranged between the outlet of the spiral coil and the vaporizer. The compressor includes a gas supply port. A gas-liquid mixing port is provided on the gas-liquid separator. The outlet of the spiral coil is in fluid communication with the gas-liquid mixing port. The gas outlet is in fluid communication with the gas supply port of the compressor.

[0007] The three-way valve includes three ports: a first connection port, a second connection port, and a third connection port. The cooler includes a cooler inlet and a cooler outlet. The first connection port is in fluid communication with the exhaust port of the compressor, the second connection port is in fluid communication with the cooler inlet, and the third connection port is in fluid communication with the engine. Natural gas discharged from the compressor exhaust port can flow to the cooler and the engine respectively through the three-way valve. The cooler outlet is in fluid communication with one end of a second throttling device, and the other end of the second throttling device is in fluid communication with the inlet of the spiral coil.

[0008] As a preferred technical solution of the present invention, the air outlet is in fluid communication with a superheater, and the superheater is in fluid communication with the air inlet of the compressor.

[0009] As a preferred technical solution of the present invention, the booster pump is a bidirectional pump, which can both discharge the natural gas in the storage tank to the gas-liquid separator and discharge the natural gas in the gas-liquid separator to the storage tank.

[0010] As a preferred technical solution of the present invention, the three-way valve is a proportional three-way valve, which can distribute the flow of natural gas to the cooler and the engine.

[0011] The advantages of the combined gas supply and reliquefaction system for marine LNG engines of the present invention are: it only needs to carry one compressor, which can be used for both natural gas reliquefaction and natural gas regasification, with low cost, and can also dynamically adjust the flow rate of natural gas supplied to the engine and the flow rate of natural gas used for reliquefaction according to the engine load, so that the compressor in the gas supply system can maintain a high operating efficiency. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of the combined gas supply and reliquefaction system for a ship's LNG engine according to the present invention.

[0014] in:

[0015] 1. Storage tank; 11. Spiral coil;

[0016] 2. Vaporizer; 3. Compressor; 4. Booster pump;

[0017] 5. Gas-liquid separator; 51. Liquid inlet; 52. Liquid outlet; 53. Gas outlet; 54. Gas-liquid mixing port;

[0018] 6. Superheater;

[0019] 7. Three-way valve; 71. First connection port; 72. Second connection port; 73. Third connection port;

[0020] 8. Cooler; 81. Cooler inlet; 82. Cooler outlet;

[0021] 9. Throttling device. Detailed Implementation

[0022] The preferred embodiments of the present invention will be described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the scope of protection of the present invention.

[0023] The advantages of the combined gas supply and reliquefaction system for marine LNG engines of the present invention are: it only needs to carry one compressor, which can be used for both natural gas reliquefaction and natural gas regasification, with low cost, and can also dynamically adjust the flow rate of natural gas supplied to the engine and the flow rate of natural gas used for reliquefaction according to the engine load, so that the compressor in the gas supply system can maintain a high operating efficiency.

[0024] like Figure 1 As shown, a combined gas supply and reliquefaction system for a ship's LNG engine includes a storage tank 1 for storing natural gas, a gasifier 2, a compressor 3, a booster pump 4, a gas-liquid separator 5, a superheater 6, a three-way valve 7, and a cooler 8.

[0025] The storage tank 1 is used to store liquefied natural gas (LNG). The LNG inside gradually heats up and evaporates into a gaseous state after absorbing heat. If the amount of gaseous natural gas gradually increases, it will cause excessive pressure inside the storage tank 1, making it unsafe to operate. A common solution is to use reliquefaction technology to reliquefy it. A spiral coil 11 is installed inside the storage tank 1. The spiral coil 11 includes an inlet and an outlet. The spiral coil 11 can be arranged either attached to or not attached to the inner wall surface of the storage tank 1. When the spiral coil 11 is not attached to the inner wall surface, its size is smaller, allowing for more spiral coils to be arranged inside the storage tank 1, thus achieving a larger heat exchange area and better heat transfer performance. If the spiral coil 11 is attached to the inner wall surface, it can be easily fixed to the inner wall surface, preventing vibration during operation.

[0026] The gas-liquid separator 5 includes a liquid inlet 51, a liquid outlet 52, a gas outlet 53, and a gas-liquid mixing port 54. The liquid inlet 51 and the liquid outlet 52 are arranged near the bottom of the gas-liquid separator 5, the gas outlet 53 is arranged near the top of the gas-liquid separator 5, and the gas-liquid mixing port 54 is arranged near the upper part of the gas-liquid separator 5. The gas-liquid two-phase natural gas entering the storage tank 1 from the liquid inlet 51 or the gas-liquid mixing port 54 will be separated into liquid natural gas and gaseous natural gas under the action of gravity.

[0027] The inlet of the booster pump 4 is in fluid communication with the storage tank 1, and the outlet of the booster pump 4 is in fluid communication with the liquid interface 51. The booster pump 4 also includes an inlet and an outlet. The booster pump 4 is a bidirectional pump, which can pump the fluid from the inlet to its outlet and the fluid from the outlet to its inlet. That is to say, the booster pump 4 can both discharge the natural gas in the storage tank 1 to the gas-liquid separator 5 and discharge the natural gas in the gas-liquid separator 5 to the storage tank 1.

[0028] The liquid outlet 52, the vaporizer 2, and the air intake of the compressor 3 are sequentially fluidly connected. The liquefied natural gas in the gas-liquid separator 5 can be discharged from the liquid outlet 52 to the vaporizer 2, vaporized in the vaporizer 2, and then flow to the air intake of the compressor 3. Finally, it is compressed to a high pressure state in the compressor 3 and then discharged into the engine.

[0029] The gas-liquid separator 5 is arranged between the outlet of the spiral coil 11 and the vaporizer 2. The compressor 3 includes a gas inlet. The gas-liquid separator 5 is provided with a gas-liquid mixing port 54. The outlet of the spiral coil 11 is in fluid communication with the gas-liquid mixing port 54. The outlet 53, the superheater 6, and the gas inlet of the compressor 3 are in fluid communication in sequence. The superheater 6 may not be provided between the outlet 53 and the gas inlet of the compressor 3, as long as the gas discharged from the outlet 53 is free of liquid. For example, a filter can be arranged at the outlet 53 to filter out the liquid mixed in the gas, because liquid can damage the compressor 3 through liquid slugging. However, adding the superheater 6 can increase the enthalpy of the gas entering the compressor 3, which is beneficial to increasing the enthalpy of the gas at the outlet of the compressor 3, thereby improving the thermal efficiency of the engine.

[0030] The three-way valve 7 includes three ports: a first connection port 71, a second connection port 72, and a third connection port 73. The cooler 8 includes a cooler inlet 81 and a cooler outlet 82. The first connection port 71 is in fluid communication with the exhaust port of the compressor 3, the second connection port 72 is in fluid communication with the cooler inlet 81, and the third connection port 73 is used to communicate with the engine. Natural gas discharged from the exhaust port of the compressor 3 can flow to the cooler 8 and the engine respectively through the three-way valve 7. The cooler outlet 82 is in fluid communication with one end of a throttling device 9, and the other end of the throttling device 9 is in fluid communication with the inlet of the spiral coil 11.

[0031] The three-way valve 7 is a proportional three-way valve, which can distribute the flow of natural gas to the cooler 8 and the engine, and can also completely close the second connection port 72 or the third connection port 73.

[0032] The gas-liquid separator 5 is equipped with a liquid level sensor. This sensor can detect the liquid level in the gas-liquid separator 5 and control the rotation direction of the booster pump 4 based on the liquid level, thereby controlling the liquid level in the gas-liquid separator 5. When the liquid level in the gas-liquid separator 5 is too low, the liquid level sensor can control the rotation of the booster pump 4, allowing the natural gas in the storage tank 1 to flow to the gas-liquid separator 5, thus gradually increasing the liquid level in the gas-liquid separator 5. When the liquid level in the gas-liquid separator 5 is too high, the liquid level sensor can control the rotation of the booster pump 4, allowing the liquefied natural gas in the gas-liquid separator 5 to gradually discharge into the storage tank 1. This structure allows the liquid level in the gas-liquid separator 5 to be stably maintained at a suitable height, ensuring a stable supply of natural gas to the suction port of the compressor 3 while preventing liquefied natural gas from being discharged from the outlet 53 to the gas supply port of the compressor 3. If liquefied natural gas enters the compressor 3 from the gas supply port, it will damage the compressor 3 through liquid slugging.

[0033] When the third connection port 73 of the three-way valve 7 is opened, at least a portion of the high-temperature, high-pressure gaseous natural gas discharged from the exhaust port of the compressor 3 will be discharged into the cooler 8 through the second connection port 72 and the cooler inlet 81. The high-temperature, high-pressure gaseous natural gas will gradually condense into a liquid state in the cooler 8 and eventually be discharged through the cooler outlet 82. When passing through the throttling device 9, it is throttled into a low-temperature, low-pressure gas-liquid mixture of natural gas, which then enters the spiral coil 11. At this time, the low-temperature, low-pressure gas-liquid mixture of natural gas will continuously absorb heat from the liquid and / or natural gas in the storage tank 1 and rise in temperature in the spiral coil 11. Some of the liquid natural gas will continue to vaporize. The gas-liquid mixture of natural gas in the spiral coil 11 will eventually be discharged into the cooler 8. The liquid separator 5 completes gas-liquid separation within it. During this process, the amount of liquefied natural gas within the gas-liquid separator 5 will continuously increase or decrease. If the liquid level of the liquefied natural gas in the gas-liquid separator 5 is too high, it may enter the compressor 3 through the outlet 53 and the gas supply port of the compressor 3, damaging the compressor 3. If the liquid level of the liquefied natural gas in the gas-liquid separator 5 is too low, the amount of natural gas entering the vaporizer 2 and the intake port of the compressor 3 will be insufficient, preventing the engine from operating normally. By installing a liquid level sensor on the gas-liquid separator 5 and designing the booster pump 4 as a bidirectional pump, the liquid level within the gas-liquid separator 5 can be better controlled, ensuring both the gas supply to the compressor 3 and its safe operation.

[0034] The above are merely some of the design ideas for the embodiments of the present invention. Where the system allows, the present invention can be extended to simultaneously connect more functional modules, thereby maximizing its functionality.

[0035] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions conceived without inventive effort should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A combined system for supplying gas to and reliquefying LNG engines in ships, comprising a storage tank (1) for storing natural gas, a vaporizer (2), and a compressor (3), characterized in that: The aforementioned ship LNG engine gas supply and reliquefaction composite system also includes a booster pump (4), a gas-liquid separator (5), a three-way valve (7), a cooler (8), and a throttling device (9). The compressor (3) includes an intake port, a replenishment port, and an exhaust port. The booster pump (4) includes an inlet and an outlet. The gas-liquid separator (5) includes a liquid inlet (51), a liquid outlet (52), a gas outlet (53), and a gas-liquid mixing port (54). The liquid inlet (51) and the liquid outlet (52) are arranged near the bottom of the gas-liquid separator (5), and the gas outlet (53) is arranged near the top of the gas-liquid separator (5). The inlet of the booster pump (4) is in fluid communication with the storage tank (1), and the outlet of the booster pump (4) is in fluid communication with the liquid interface (51). The liquid outlet (52), the vaporizer (2), and the air inlet of the compressor (3) are in sequential fluid communication. The storage tank (1) is provided with a spiral coil (11), which also includes an inlet and an outlet. The gas-liquid separator (5) is arranged between the outlet of the spiral coil (11) and the vaporizer (2). The outlet of the spiral coil (11) is in fluid communication with the gas-liquid mixing port (54), and the gas outlet (53) is in fluid communication with the gas supply port of the compressor (3). The three-way valve (7) includes three ports: a first connection port (71), a second connection port (72), and a third connection port (73). The cooler (8) includes a cooler inlet (81) and a cooler outlet (82). The first connection port (71) is in fluid communication with the exhaust port of the compressor (3), the second connection port (72) is in fluid communication with the inlet (81) of the cooler, and the third connection port (73) is used to be in fluid communication with the engine. The natural gas discharged from the exhaust port of the compressor (3) can flow to the cooler (8) and the engine respectively through the three-way valve (7); the cooler outlet (82) is in fluid communication with one end of the throttling device (9), and the other end of the throttling device (9) is in fluid communication with the inlet of the spiral coil (11).

2. The combined gas supply and reliquefaction system for marine LNG engines according to claim 1, characterized in that: The air outlet (53) is in fluid communication with a superheater (6), and the superheater (6) is in fluid communication with the air supply port of the compressor (3).

3. The combined gas supply and reliquefaction system for marine LNG engines according to claim 1, characterized in that: The booster pump (4) is a bidirectional pump, which can discharge natural gas in the storage tank (1) into the gas-liquid separator (5) and also discharge natural gas in the gas-liquid separator (5) into the storage tank (1). The gas-liquid separator (5) is equipped with a liquid level sensor, which can detect the liquid level in the gas-liquid separator (5) and control the rotation direction of the booster pump (4) according to the liquid level, thereby controlling the liquid level in the gas-liquid separator (5).

4. The combined gas supply and reliquefaction system for marine LNG engines according to claim 1, characterized in that: The three-way valve (7) is a proportional three-way valve, which can distribute the flow of natural gas to the cooler (8) and the engine.

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