Ship and onboard power generation method

Abstract

To provide a ship and an onboard power generation method capable of improving fuel efficiency using boil-off gas.SOLUTION: A ship comprises a hull having a propeller, a main engine to drive the propeller installed on the hull, a shaft power generator to generate inboard power by being driven in association with the main engine rotation, a tank installed in the hull and capable of storing a liquified gas, a main supply line vaporizing the liquefied gas stored in the tank and capable of supplying it to the main engine, and a boil-off gas line capable of supplying the boil-off gas generated in the tank to the main engine.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a ship and an in-ship power generation method.

Background Art

[0002] Patent Document 1 discloses a configuration in which boil-off gas generated in a storage tank storing liquefied natural gas as fuel is compressed and reliquefied and supplied to an engine. With such a configuration, the boil-off gas generated in the tank is effectively utilized to reduce the fuel consumption.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a ship as described in Patent Document 1, in order to generate electric power for in-ship use, there is a ship equipped with an engine for driving a generator separately from the main engine. The engine for driving the generator has lower fuel efficiency compared to the main engine. For this reason, it is desired to improve the fuel efficiency while effectively utilizing the boil-off gas.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a ship and an in-ship power generation method capable of effectively utilizing boil-off gas and improving fuel efficiency.

Means for Solving the Problems

[0006] To solve the above problems, the ship according to the present disclosure includes a hull, a main engine, a shaft generator, a tank, a main supply line, and a boil-off gas line. The hull has a propeller. The main engine is provided on the hull to drive the propeller. The shaft generator is driven along with the rotation of the main engine to generate in-ship power. The tank is provided on the hull and can store liquefied gas. The main supply line can vaporize the liquefied gas stored in the tank and supply it to the main engine. The boil-off gas line can supply the boil-off gas generated in the tank to the main engine.

[0007] The in-ship power generation method according to the present disclosure is an in-ship power generation method in a ship as described above. The in-ship power generation method switches between a first mode and a second mode. In the first mode, boil-off gas is supplied to the main engine during navigation of the ship, and in-ship power is generated by the shaft generator. In the second mode, the boil-off gas is supplied to the auxiliary machinery during berthing of the ship, and in-ship power is generated by the auxiliary machinery.

Effect of the Invention

[0008] According to the ship and the in-ship power generation method of the present disclosure, boil-off gas can be effectively utilized to improve fuel efficiency.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

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Figure 16

Mode for Carrying Out the Invention

[0010] Hereinafter, a ship and an in-ship power generation method according to an embodiment of the present disclosure will be described with reference to FIGS. 1 to 16. <First Embodiment> (Overall Configuration of Ship) As shown in FIG. 1, the ship 1 of this first embodiment mainly includes a hull 2, a main engine 20, a shaft generator 25, auxiliary machinery 30, and a tank 10. The ship type of the ship 1 is not limited to a specific one. Examples of the ship type of the ship 1 include carriers for liquefied gases such as liquefied natural gas (LNG), carbon dioxide, and ammonia, ferries, RORO ships (Roll-on / Roll-off ships), PCTCs (Pure Car & Truck Carriers), passenger ships, and the like.

[0011] The hull 2 has a pair of side shells 3A and 3B forming its outer shell, a bottom 4, and an upper deck 5. The side shells 3A and 3B are composed of a pair of side shell plates forming the left and right side shells respectively. The bottom 4 is composed of a bottom shell plate connecting these side shells 3A and 3B. The upper deck 5 is an all-through deck exposed to the outside. In the hull 2, for example, an upper structure 7 having a living area is formed on the upper deck 5 on the stern 2b side.

[0012] (Configurations of Main Engine, Shaft Generator, and Auxiliary Machinery) The main engine 20 and the auxiliary machinery 30 are provided inside the hull 2. The main engine 20 and the auxiliary machinery 30 use the liquefied gas stored in the tank 10 as fuel. In this first embodiment, the main engine 20 and the auxiliary machinery 30 use, for example, LNG as fuel. The liquefied gas as fuel for the main engine 20 and the auxiliary machinery 30 is not limited to LNG, and may be LPG (liquefied petroleum gas), ammonia, hydrogen, or the like.

[0013] The main engine 20 is, for example, an engine (internal combustion engine) that burns liquefied gas as fuel. In this first embodiment, the main engine 20 is a direct injection type two-stroke engine that directly injects fuel into the combustion chamber. The main engine 20 uses fuel at a higher pressure compared to the auxiliary machine 30. The pressure of the fuel (fuel gas) used in the main engine 20 is, for example, a high pressure of 20 MPa or more and 35 MPa or less. The pressure of the fuel supplied to the main engine 20 is preferably, for example, 25 MPa or more and 30 MPa or less.

[0014] The main engine 20 drives the propeller 9. The propeller 9 is provided outside the stern 2b of the hull 2. The main engine 20 and the propeller 9 are connected via a propeller shaft 8 extending in the fore-and-aft direction FA. The main engine 20 rotationally drives the propeller 9 by rotating the propeller shaft 8 around its axis. The propeller 9 exerts a propulsive force for navigating the ship 1 when rotationally driven by the main engine 20.

[0015] The shaft generator 25 is provided inside the hull 2 and generates in-ship power used inside the ship 1. The shaft generator 25 is driven as the main engine 20 rotates. In this first embodiment, the shaft generator 25 is connected to the propeller shaft 8. The shaft generator 25 converts the rotational energy of the propeller shaft 8 rotationally driven by the main engine 20 into electrical energy. The shaft generator 25 may be directly connected to the propeller shaft 8, or may be connected to the propeller shaft 8 via a speed increaser, a clutch, or the like.

[0016] The auxiliary machine 30 illustrated in this first embodiment is a generator engine for driving a generator (not shown) for generating in-ship power used inside the ship 1. The auxiliary machine 30 uses fuel at a lower pressure than the main engine 20. The pressure of the fuel (fuel gas) used in the auxiliary machine 30 is, for example, 0.5 MPa or more and 1.0 MPa or less. As the auxiliary machine 30, for example, a gas turbine, a reciprocating engine, or the like can be used. The rotational energy generated by the auxiliary machine 30 is converted into electrical energy by the generator and can be supplied to each part inside the hull 2.

[0017] (Configuration of the tank) The tank 10 is installed in the hull 2. The tank 10 of this first embodiment is provided, for example, on the upper deck 5. The tank 10 may be provided inside the hull 2. In this first embodiment, the tank 10 stores LNG as liquefied gas that serves as fuel for the main engine 20 and auxiliary machinery 30.

[0018] (Configuration of main supply line and boil-off gas line) FIG. 2 is a diagram showing a fuel supply system from a tank to a main engine and auxiliary machinery in a ship according to the first embodiment of the present disclosure. As shown in FIG. 2, the ship 1 includes a main supply line 100, an auxiliary machinery supply line 200, and a boil-off gas line 300A in order to supply the liquefied gas stored in the tank 10 as fuel to the main engine 20 and the auxiliary machinery 30.

[0019] The main supply line 100 connects the tank 10 and the main engine 20. The main supply line 100 vaporizes the liquefied gas LG in the tank 10 and supplies it to the main engine 20. The main supply line 100 is provided with a pump 11, a pressurizing pump 12, and a high-pressure vaporizer 13.

[0020] The pump 11 is provided in the main supply line 100. The pump 11 sucks out the liquefied gas LG in the tank 10. The pump 11 pumps the sucked liquefied gas LG toward the main engine 20.

[0021] The pressurizing pump 12 is provided on the downstream side in the flow direction of the liquefied gas LG in the main supply line 100 rather than the pump 11 in the main supply line 100. The pressurizing pump 12 boosts the pressure of the liquefied gas LG to a pressure higher than that of the pump 11.

[0022] The high-pressure vaporizer 13 is provided on the downstream side in the flow direction of the liquefied gas LG in the main supply line 100 rather than the pressure pump 12 in the main supply line 100. The high-pressure vaporizer 13 vaporizes the liquefied gas LG pumped by the pressure pump 12. The high-pressure vaporizer 13 vaporizes the liquefied gas LG at a pressure higher than that of the auxiliary equipment vaporizer 31 described later to generate the fuel gas FG. In this first embodiment, the pressure of the fuel gas FG generated through the pressure pump 12 and the high-pressure vaporizer 13 is, for example, about 30 MPa. The fuel gas FG generated through the high-pressure vaporizer 13 is supplied to the main engine 20 through the main supply line 100.

[0023] The auxiliary equipment supply line 200 vaporizes the liquefied gas LG in the tank 10 and supplies it to the auxiliary equipment 30. The upstream end 201 of the auxiliary equipment supply line 200 is connected between the pump 11 and the pressure pump 12 in the main supply line 100. The downstream end 202 of the auxiliary equipment supply line 200 is connected to the auxiliary equipment 30.

[0024] The auxiliary equipment supply line 200 is provided with an auxiliary equipment vaporizer 31. The auxiliary equipment vaporizer 31 vaporizes the liquefied gas LG pumped by the pump 11. The auxiliary equipment vaporizer 31 vaporizes the liquefied gas LG at a pressure lower than that of the high-pressure vaporizer 13 to generate the auxiliary equipment fuel gas FG2. The pressure of the auxiliary equipment fuel gas FG2 generated through the pump 11 and the auxiliary equipment vaporizer 31 is, for example, about 0.6 MPa. The auxiliary equipment fuel gas FG2 generated by the auxiliary equipment vaporizer 31 is supplied to the auxiliary equipment 30 through the auxiliary equipment supply line 200.

[0025] The boil-off gas line 300A can supply the boil-off gas BOG generated in the tank 10 to the main engine 20. The upstream end 301 of the boil-off gas line 300A is connected to the tank 10 so as to communicate with the gas phase portion in the tank 10. The downstream end 302 of the boil-off gas line 300A is connected to the main supply line 100 on the downstream side of the high-pressure vaporizer 13.

[0026] Inside the tank 10, the liquefied gas LG in a liquid state vaporizes due to natural heat input from the outside or the like, and boil-off gas BOG is generated. In this first embodiment, the boil-off gas line 300A introduces the boil-off gas BOG generated inside the tank 10 into the main engine 20.

[0027] The boil-off gas line 300A is provided with a high-pressure gas compressor (gas compressor) 51 that pressurizes the boil-off gas supplied to the main engine 20 through the boil-off gas line 300A. The high-pressure gas compressor 51 can pressurize the boil-off gas BOG to a pressure equal to or higher than the pressure of the fuel gas FG supplied to the main engine 20. The high-pressure gas compressor 51 of this first embodiment pressurizes the gaseous boil-off gas BOG to the same pressure as the fuel gas FG that has passed through the pump 11, the pressurizing pump 12, and the high-pressure vaporizer 13. The boil-off gas line 300A of this first embodiment is configured to be able to merge the boil-off gas BOG pressurized by the high-pressure gas compressor 51 into the main supply line 100 on the downstream side of the high-pressure vaporizer 13. That is, the boil-off gas line 300A supplies the boil-off gas BOG to the main engine 20 by mixing it with the fuel gas FG vaporized by the high-pressure vaporizer 13.

[0028] (In-ship power generation method) Next, the in-ship power generation method in the ship 1 will be described. FIG. 3 is a diagram showing a state in which power is being generated using the main engine in a ship according to the first embodiment of the present disclosure. As shown in FIG. 3, in this first embodiment, when the ship 1 is sailing with the main engine 20 driving the propeller 9, the shaft generator 25 is driven by the main engine 20, and the shaft generator 25 generates in-ship power. In this case, the boil-off gas BOG in the tank 10 is pressurized and supplied to the main engine 20 by the high-pressure gas compressor 51 through the boil-off gas line 300A. Further, according to the generation amount of the boil-off gas BOG in the tank 10, the fuel gas FG (gas obtained by vaporizing the liquefied gas LG) that has passed through the pressurizing pump 12 and the high-pressure vaporizer 13 from the tank 10 may be supplied to the main engine 20 through the main supply line 100. Alternatively, while mainly supplying the fuel gas FG in the main supply line 100 to the main engine 20, the shortage may be supplemented with the boil-off gas BOG passing through the boil-off gas line 300A. In this first embodiment, when the shaft generator 25 is driven by the main engine 20 in this manner, the auxiliary machine 30 is stopped. To do this, the supply of the liquefied gas LG to the auxiliary machine 30 is stopped by a method such as closing the valve 205 provided in the auxiliary machine supply line 200. In this way, while the ship 1 is sailing, in-ship power is generated by the shaft generator 25 using the main engine 20, which has better fuel efficiency than the auxiliary machine 30.

[0029] FIG. 4 is a diagram showing a state in which power is being generated using an auxiliary machine in a ship according to an embodiment of the present disclosure. As shown in FIG. 4, when the main engine 20 is stopped while the ship 1 is at anchor, the auxiliary machine 30 drives a generator (not shown) to supply in-ship power. To do this, the liquefied gas LG in the tank 10 is vaporized through the auxiliary machine vaporizer 31 by the auxiliary machine supply line 200 to generate the auxiliary machine fuel gas FG. The auxiliary machine supply line 200 supplies the generated auxiliary machine fuel gas FG2 to the auxiliary machine 30. In this case, for example, the supply of the liquefied gas LG to the main engine 20 is stopped by closing the valve 105 provided in the main supply line 100. Also, in the boil-off gas line 300A, for example, the supply of the boil-off gas BOG to the main engine 20 is stopped by closing the valve 305 provided in the boil-off gas line 300A. In the first embodiment, the case where the auxiliary machine 30 is not driven during the navigation of the ship 1 has been described. However, when the ship's internal power is insufficient with only the shaft generator 25 being driven, the auxiliary machine 30 may be driven to supplement the shortage.

[0030] (Function and effect) The ship 1 of the first embodiment includes a main supply line 100 capable of supplying the liquefied gas LG in the tank 10 to the main engine 20, and a boil-off gas line 300A capable of supplying the boil-off gas BOG in the tank 10 to the main engine 20. Thereby, the main engine 20 can use both the liquefied gas LG in the tank 10 and the boil-off gas BOG generated by the vaporization of the liquefied gas LG in the tank 10 as fuel. Along with the rotation of the main engine 20 when driving the propeller 9 by such a main engine 20, by driving the shaft generator 25, the ship's internal power can be generated using the main engine 20 with high fuel efficiency. Therefore, the boil-off gas BOG can be effectively utilized to improve the fuel efficiency.

[0031] Also, in the first embodiment, the high-pressure fuel gas that becomes the fuel of the main engine 20 is generated from the liquefied gas LG in the tank 10 by the pressurizing pump 12 and the high-pressure vaporizer 13 provided in the main supply line 100. In the boil-off gas line 300A, the boil-off gas BOG can be utilized as the high-pressure fuel gas FG supplied to the main engine 20 by pressurizing the boil-off gas BOG to the pressure of the fuel gas supplied to the main engine 20 by the high-pressure gas compressor 51. Thereby, even when the main engine 20 that requires high-pressure gas as fuel is provided, the boil-off gas BOG can be effectively utilized to improve the fuel efficiency.

[0032] <Second Embodiment> Next, a second embodiment of the ship and the in-ship power generation method according to the present disclosure will be described. In the second embodiment described below, only the configuration of the boil-off gas line is different from that of the first embodiment. Therefore, the same parts as those in the first embodiment will be denoted by the same reference numerals and described, and redundant descriptions will be omitted. FIG. 5 is a diagram showing a fuel supply system from a tank to a main engine and auxiliary machinery in a ship according to a second embodiment of the present disclosure. As shown in FIG. 5, for the ship 1 of this second embodiment to supply the liquefied gas stored in the tank 10 as fuel to the main engine 20 and the auxiliary machinery 30, a main supply line 100, an auxiliary machinery supply line 200, and a boil-off gas line 300B are provided.

[0033] The boil-off gas line 300B can supply the boil-off gas BOG generated in the tank 10 to the main engine 20. The upstream end 301 of the boil-off gas line 300B is connected to the tank 10 so as to communicate with the gas phase portion in the tank 10. The downstream end 302 of the boil-off gas line 300B is connected to the main supply line 100 on the downstream side with respect to the high-pressure vaporizer 13.

[0034] The boil-off gas line 300B is provided with a gas compressor 52 for pressurizing the boil-off gas BOG supplied to the main engine 20 through the boil-off gas line 300B. The gas compressor 52 can pressurize the boil-off gas BOG to a pressure equal to or higher than the pressure of the fuel gas FG supplied to the main engine 20. The boil-off gas line 300B of this second embodiment includes a first gas compressor 53 and a second gas compressor 54 as a plurality of gas compressors 52.

[0035] The first gas compressor 53 boosts the boil-off gas BOG from the tank 10 supplied through the boil-off gas line 300B to a first pressure (for example, 0.6 MPa) required as fuel for the auxiliary machinery 30 (pressure of the auxiliary machinery fuel gas FG2).

[0036] The second gas compressor 54 is disposed in the boil-off gas line 300B between the first gas compressor 53 and the main supply line 100 having its downstream end 302 connected thereto. The second gas compressor 54 further boosts the boil-off gas BOG that has been boosted to the first pressure through the first gas compressor 53 to the second pressure (e.g., 30 MPa) required as fuel for the main engine 20. This second pressure is preferably set to the same pressure as the fuel gas FG that has passed through the pump 11, the pressurizing pump 12, and the high-pressure vaporizer 13. Here, since the second gas compressor 54 only needs to boost the boil-off gas BOG that has been boosted to the first pressure through the first gas compressor 53 to the second pressure, its capacity can be lower compared to the high-pressure gas compressor 51 shown in the above first embodiment.

[0037] The boil-off gas line 300B is configured to allow the boil-off gas BOG that has been boosted through the first gas compressor 53 and the second gas compressor 54 to flow into the main supply line 100 on the downstream side of the high-pressure vaporizer 13. That is, the boil-off gas line 300B supplies the main engine 20 by mixing the boil-off gas BOG with the fuel gas FG vaporized in the high-pressure vaporizer 13.

[0038] Also, an auxiliary boil-off gas supply line 400 is branched and connected to the boil-off gas line 300B. The upstream end of the auxiliary boil-off gas supply line 400 is connected to the boil-off gas line 300B between the first gas compressor 53 and the second gas compressor 54. The downstream end of the auxiliary boil-off gas supply line 400 is connected to the auxiliary machine 30. The auxiliary boil-off gas supply line 400 supplies the boil-off gas BOG that has been boosted to the first pressure through the first gas compressor 53 to the auxiliary machine 30 as the auxiliary fuel gas FG2 for the auxiliary machine 30.

[0039] (Configuration of the switching unit) The ship 1 of this second embodiment includes a switching unit 70. The switching unit 70 enables selective switching of the supply destination of the boil-off gas BOG through the boil-off gas line 300B between the main engine 20 and the auxiliary machine 30. The switching unit 70 includes a first valve 71 and a second valve 72. The first valve 71 is provided between the first gas compressor 53 and the second gas compressor 54 in the boil-off gas line 300B. The first valve 71 is provided on the downstream side of the position where the upstream end of the auxiliary boil-off gas supply line 400 is connected in the boil-off gas line 300B. The first valve 71 is configured to open and close the flow path in the boil-off gas line 300B. The second valve 72 is provided in the middle of the auxiliary boil-off gas supply line 400. The second valve 72 is configured to open and close the flow path in the auxiliary boil-off gas supply line 400.

[0040] When the first valve 71 is open and the second valve 72 is closed, the boil-off gas BOG is pressurized to the second pressure through the first gas compressor 53 and the second gas compressor 54 and supplied to the main engine 20. When the first valve 71 is closed and the second valve 72 is open, the boil-off gas BOG is pressurized to the first pressure only through the first gas compressor 53 and supplied to the auxiliary machine 30 as the auxiliary fuel gas FG2 for the auxiliary machine 30. The first valve 71 and the second valve 72 can be opened and closed manually by an operator or remotely by an operator.

[0041] (In-ship power generation method) Next, the in-ship power generation method in the ship 1 as described above will be described. FIG. 6 is a diagram showing the flow of boil-off gas when the first mode is being executed in the in-ship power generation method according to the second embodiment of the present disclosure. FIG. 7 is a diagram showing the flow of boil-off gas when the second mode is being executed in the in-ship power generation method according to the second embodiment of the present disclosure. The ship 1 switches the supply destination of the boil-off gas BOG between the main engine 20 and the auxiliary machine 30 according to its navigation state, specifically, whether or not the main engine 20 is operating for navigation. For this reason, the ship 1 is configured to be able to switch between a first mode M1 executed during navigation and a second mode M2 executed during berthing.

[0042] As shown in FIG. 6, in this second embodiment, when the ship 1 is sailing with the main engine 20 driving the propeller 9, the ship 1 executes the first mode M1. In the first mode M1, the shaft generator 25 is driven by the main engine 20, and the shaft generator 25 generates in-ship power. In this case, the first valve 71 is opened and the second valve 72 is closed. As a result, the boil-off gas BOG from the tank 10 is pressurized to the second pressure through the first gas compressor 53 and the second gas compressor 54 and supplied to the main engine 20. In this first mode M1, the boil-off gas BOG is supplied to the main engine 20 during the navigation of the ship 1, and the shaft generator 25 generates in-ship power. At this time, according to the amount of boil-off gas BOG generated in the tank 10 and the shortage of the supply capacity of the second gas compressor 54 with respect to the amount of fuel gas required by the main engine 20, the fuel gas FG (gas obtained by vaporizing the liquefied gas LG) that has passed through the pressure pump 12 and the high-pressure vaporizer 13 from the tank 10 may be supplied to the main engine 20 through the main supply line 100.

[0043] As shown in FIG. 7, in this second embodiment, when the ship 1 is at anchor and the main engine 20 is not driving the propeller 9, the ship 1 executes the second mode M2. In the second mode M2, the first valve 71 is closed and the second valve 72 is opened. As a result, the boil-off gas BOG from the tank 10 is pressurized to the first pressure only through the first gas compressor 53, and is supplied as auxiliary machine fuel gas FG2 to the auxiliary machine 30 through the auxiliary machine boil-off gas supply line 400. In this second mode M2, the boil-off gas BOG is supplied to the auxiliary machine 30 during the anchorage of the ship 1, and the auxiliary machine 30 generates in-ship power. At this time, according to the amount of boil-off gas BOG generated in the tank 10 and the shortage of the supply capacity of the first gas compressor 53 with respect to the amount of fuel gas required by the auxiliary machine 30, through the auxiliary machine supply line 200, from the tank 10 to the pump 11 and the auxiliary machine vaporizer 31, the fuel gas FG (gas obtained by vaporizing the liquefied gas LG) may be supplied to the auxiliary machine 30. In the above second embodiment, the case where the auxiliary machine 30 is not driven during the navigation of the ship 1 has been described. However, similar to the first embodiment, when the in-ship power is insufficient with only the shaft generator 25 driven, the boil-off gas BOG may be supplied from the first gas compressor 53 to both the auxiliary machine 30 and the second gas compressor 54, and the auxiliary machine 30 may be driven to supplement the shortage of the in-ship power.

[0044] (Function and effect) In the ship 1 of the above second embodiment, by the switching unit 70, the supply destination of the boil-off gas BOG through the boil-off gas line 300B can be selectively switched between the main engine 20 and the auxiliary machine 30. Thereby, when the main engine 20 is operating, the boil-off gas BOG can be supplied to the main engine 20, and when the auxiliary machine 30 is operating, the boil-off gas BOG can be supplied to the auxiliary machine 30. Therefore, it is possible to suppress the waste of the boil-off gas BOG generated in the tank 10 and effectively consume it with the main engine 20 and the auxiliary machine 30.

[0045] Also, in the above second embodiment, the pressurizing pump 12 and the high-pressure vaporizer 13 provided in the main supply line 100 generate high-pressure fuel gas that becomes the fuel of the main engine 20 from the liquefied gas LG in the tank 10. In the boil-off gas line 300B, the boil-off gas BOG can be used as the high-pressure fuel gas supplied to the main engine 20 by pressurizing the boil-off gas BOG to the pressure of the fuel gas supplied to the main engine 20 by the gas compressor 52. Thereby, even when the ship is equipped with the main engine 20 that requires high-pressure gas as fuel, the boil-off gas BOG can be effectively utilized and the fuel efficiency can be improved.

[0046] Further, in the above-described second embodiment, the gas compressor 52 includes a first gas compressor 53 and a second gas compressor 54. The first gas compressor 53 can boost the boil-off gas BOG to a first pressure and supply the boosted boil-off gas BOG as auxiliary machine fuel gas FG2 to the auxiliary machine 30. Also, the second gas compressor 54 can further boost the boil-off gas that has been boosted to the first pressure by the first gas compressor 53 to a second pressure and supply the boosted boil-off gas BOG as fuel gas FG to the main engine 20. In this way, when supplying the boil-off gas BOG to the main engine 20, the first gas compressor 53 and the second gas compressor 54 boost the boil-off gas BOG in two stages, and when supplying the boil-off gas BOG to the auxiliary machine 30, only the first gas compressor 53 boosts the boil-off gas BOG. Such a boil-off gas line 300B can realize a configuration in which the supply destination of the boil-off gas BOG can be switched between the main engine 20 and the auxiliary machine 30.

[0047] In the method for generating in-ship power of the above-described second embodiment, there is a switch between a first mode M1 in which the boil-off gas BOG is supplied to the main engine 20 during navigation of the ship 1 and in-ship power is generated by the shaft generator 25, and a second mode M2 in which the boil-off gas BOG is supplied to the auxiliary machine 30 during berthing of the ship 1 and in-ship power is generated by the auxiliary machine 30. Thereby, when the main engine 20 is operating during navigation of the ship 1, in-ship power is generated by the main engine 20, and when the auxiliary machine 30 is operating during berthing of the ship 1, in-ship power can be generated by the auxiliary machine 30. Therefore, it is possible to suppress waste of the boil-off gas BOG generated in the tank 10 and effectively utilize it to generate in-ship power by the main engine 20 and the auxiliary machine 30. As a result, even when the ship is equipped with the main engine 20 that requires high-pressure gas as fuel, the boil-off gas can be effectively utilized and the fuel efficiency can be improved.

[0048] Further, in the second embodiment, similar to the first embodiment, there are provided a main supply line 100 capable of supplying the liquefied gas LG in the tank 10 to the main engine 20, and a boil-off gas line 300B capable of supplying the boil-off gas BOG in the tank 10 to the main engine 20. Thereby, the boil-off gas BOG can be effectively utilized to improve the fuel efficiency.

[0049] Also, in the second embodiment, the pressurizing pump 12 and the high-pressure vaporizer 13 provided in the main supply line 100 generate high-pressure fuel gas FG serving as fuel for the main engine 20 from the liquefied gas LG in the tank 10. In the boil-off gas line 300B, the boil-off gas BOG is pressurized by the high-pressure gas compressor 51 to a pressure corresponding to the fuel gas FG supplied to the main engine 20, so that the boil-off gas BOG can be used as the high-pressure fuel gas FG supplied to the main engine 20. Thereby, even when the main engine 20 that requires high-pressure gas as fuel is provided, the boil-off gas can be effectively utilized to improve the fuel efficiency.

[0050] In the second embodiment, the switching unit 70 includes the first valve 71 and the second valve 72, but the present invention is not limited thereto. Instead of the first valve 71 as the switching unit 70, the supply and stop of the boil-off gas BOG passing through the boil-off gas line 300B may be switched by switching the operation and stop of the second gas compressor 54. That is, when the shaft generator 25 generates in-ship power, the second gas compressor 54 is operated, and the boil-off gas BOG from the tank 10 is supplied to the main engine 20 through the first gas compressor 53 and the second gas compressor 54. When the auxiliary machine 30 generates in-ship power, the operation of the second gas compressor 54 is stopped. Thereby, the boil-off gas BOG from the tank 10 is supplied to the auxiliary machine 30 as the auxiliary machine fuel gas FG2 through only the first gas compressor 53.

[0051] <Third Embodiment> Next, a third embodiment of the ship and the in-ship power generation method according to the present disclosure will be described. In the third embodiment described below, only the configuration of the boil-off gas line is different from that of the first embodiment. Therefore, the same reference numerals will be given to the same parts as those in the first and second embodiments, and redundant descriptions will be omitted. FIG. 8 is a diagram showing a fuel supply system from a tank to a main engine and auxiliary machinery in a ship according to the third embodiment of the present disclosure. As shown in FIG. 8, for the ship 1 of this third embodiment to supply the liquefied gas stored in the tank 10 as fuel to the main engine 20 and the auxiliary machinery 30, it is provided with a main supply line 100, an auxiliary machinery supply line 200, and a boil-off gas line 300C.

[0052] The boil-off gas line 300C can supply the boil-off gas BOG generated in the tank 10 to the main engine 20. The upstream end 301 of the boil-off gas line 300C is connected to the tank 10 so as to communicate with the gas phase portion in the tank 10. The downstream end 303 of the boil-off gas line 300C is connected to the main supply line 100 between the pump 11 and the pressure pump 12. The downstream end 303 of the boil-off gas line 300C is connected to the main supply line 100 on the downstream side of the upstream end 201 of the auxiliary machinery supply line 200.

[0053] The boil-off gas line 300C is provided with a gas compressor 55 for pressurizing the boil-off gas supplied to the main engine 20 through the boil-off gas line 300C. In this third embodiment, the gas compressor 55 boosts the boil-off gas BOG from the tank 10 supplied through the boil-off gas line 300C to the pressure (for example, 0.6 MPa) required as fuel (auxiliary machinery fuel gas FG2) for the auxiliary machinery 30.

[0054] The boil-off gas line 300C mixes the boil-off gas BOG pressurized through the gas compressor 55 into the liquefied gas LG flowing through the main supply line 100. In this third embodiment, the boil-off gas line 300C mixes the boil-off gas BOG pressurized through the gas compressor 55 into the liquefied gas LG flowing through the main supply line 100 upstream of the pressure pump 12. As a result, the boil-off gas BOG mixed into the liquefied gas LG is cooled by the liquefied gas LG, promoting the reliquefaction of the boil-off gas BOG. Therefore, the boil-off gas BOG pressurized through the gas compressor 55, together with the liquefied gas LG from the tank 10, is further pressurized by the pressure pump 12, vaporized in the high-pressure vaporizer 13, and sent to the main engine 20.

[0055] Also, an auxiliary boil-off gas supply line 400 is connected to the boil-off gas line 300C. The upstream end of the auxiliary boil-off gas supply line 400 is connected to the boil-off gas line 300C between the gas compressor 55 and the downstream end 303 of the boil-off gas line 300C. The downstream end of the auxiliary boil-off gas supply line 400 is connected to the auxiliary machine 30. This auxiliary boil-off gas supply line 400 supplies the boil-off gas BOG pressurized through the gas compressor 55 to the auxiliary machine 30 as the auxiliary fuel gas FG2 of the auxiliary machine 30.

[0056] (Configuration of the switching unit) The ship 1 of the third embodiment includes a switching unit 70B. The switching unit 70B enables the supply destination of the boil-off gas BOG through the boil-off gas line 300C to be selectively switched between the main engine 20 and the auxiliary machine 30. The switching unit 70B includes a first valve 73 and a second valve 74.

[0057] The first valve 73 is provided between the gas compressor 55 and the downstream end 303 of the boil-off gas line 300C in the boil-off gas line 300C. The first valve 73 is provided on the downstream side of the position where the upstream end of the auxiliary machine boil-off gas supply line 400 is connected in the boil-off gas line 300C. The first valve 73 is capable of opening and closing the flow path in the boil-off gas line 300C. The second valve 74 is provided in the middle of the auxiliary machine boil-off gas supply line 400. The second valve 74 is capable of opening and closing the flow path in the auxiliary machine boil-off gas supply line 400.

[0058] When the first valve 73 is open and the second valve 74 is closed, the boil-off gas BOG is pressurized through the gas compressor 55, the pressurizing pump 12, and the high-pressure vaporizer 13 and supplied to the main engine 20 as the fuel gas FG. When the first valve 73 is closed and the second valve 74 is open, the boil-off gas BOG is pressurized only through the gas compressor 55 and supplied to the auxiliary machine 30 as the auxiliary machine fuel gas FG2 for the auxiliary machine 30.

[0059] (In-ship power generation method) Next, the in-ship power generation method in the ship 1 as described above will be described. FIG. 9 is a diagram showing the flow of boil-off gas when the first mode is executed in the in-ship power generation method according to the third embodiment of the present disclosure. FIG. 10 is a diagram showing the flow of boil-off gas when the second mode is executed in the in-ship power generation method according to the third embodiment of the present disclosure.

[0060] As shown in FIG. 9, when the ship 1 is sailing with the main engine 20 driving the propeller 9, the ship 1 executes the first mode M11. In the first mode M11, the shaft generator 25 is driven by the main engine 20, and the shaft generator 25 generates in-ship power. In this case, the first valve 73 is opened and the second valve 74 is closed. As a result, the boil-off gas BOG from the tank 10 is supplied to the main engine 20 as fuel gas FG through the gas compressor 55, the pressurizing pump 12, and the high-pressure vaporizer 13. In the first mode M11, the boil-off gas BOG is supplied to the main engine 20 during the navigation of the ship 1, and the shaft generator 25 generates in-ship power.

[0061] As shown in FIG. 10, when the ship 1 is at anchor and the main engine 20 is not driving the propeller 9, the ship 1 executes the second mode M12. In the second mode M12, the first valve 73 is closed and the second valve 74 is opened. As a result, the boil-off gas BOG from the tank 10 is pressurized only through the gas compressor 55, and is supplied to the auxiliary machinery 30 as auxiliary machinery fuel gas FG2 through the auxiliary machinery boil-off gas supply line 400. In the second mode M12, the boil-off gas BOG is supplied to the auxiliary machinery 30 during the anchorage of the ship 1, and the auxiliary machinery 30 generates in-ship power.

[0062] (Function and Effect) In the ship 1 of the above third embodiment, the high-pressure fuel gas serving as the fuel of the main engine 20 is generated from the liquefied gas LG in the tank 10 by the pressurizing pump 12 and the high-pressure vaporizer 13 provided in the main supply line 100. By mixing the boil-off gas BOG with the pressurized liquefied gas LG flowing through the main supply line 100, it can be supplied as the fuel of the main engine 20. In this way, by vaporizing the boil-off gas BOG together with the liquefied gas LG flowing through the main supply line 100, the fuel gas FG can be efficiently generated and supplied to the main engine 20.

[0063] Further, in the third embodiment, similar to the second embodiment, the switching unit 70B can selectively switch the supply destination of the boil-off gas BOG through the boil-off gas line 300C between the main engine 20 and the auxiliary machine 30. Thereby, when the main engine 20 is operating, the boil-off gas BOG can be supplied to the main engine 20, and when the auxiliary machine 30 is operating, the boil-off gas BOG can be supplied to the auxiliary machine 30. Therefore, the boil-off gas BOG generated in the tank 10 can be prevented from being wasted and can be effectively consumed by the main engine 20 and the auxiliary machine 30.

[0064] In the in-ship power generation method of the third embodiment, there are a first mode M11 in which the boil-off gas BOG is supplied to the main engine 20 during the navigation of the ship 1 and the shaft generator 25 generates in-ship power, and a second mode M12 in which the boil-off gas BOG is supplied to the auxiliary machine 30 during the berthing of the ship 1 and the auxiliary machine 30 generates in-ship power, which are switched. Thereby, when the main engine 20 is operating during the navigation of the ship 1, the in-ship power is generated by the main engine 20, and when the auxiliary machine 30 is operating during the berthing of the ship 1, the in-ship power can be generated by the auxiliary machine 30. Therefore, the boil-off gas BOG generated in the tank 10 can be prevented from being wasted and can be effectively used to generate in-ship power by the main engine 20 and the auxiliary machine 30. As a result, the boil-off gas can be effectively utilized and the fuel efficiency can be improved.

[0065] Further, in the third embodiment, similar to the first embodiment, it includes a main supply line 100 capable of supplying the liquefied gas LG in the tank 10 to the main engine 20 and a boil-off gas line 300C capable of supplying the boil-off gas BOG in the tank 10 to the main engine 20. Thereby, the boil-off gas BOG can be effectively utilized and the fuel efficiency can be improved.

[0066] <Fourth Embodiment> Next, a fourth embodiment of the ship and the in-ship power generation method according to the present disclosure will be described. In the fourth embodiment described below, only the configuration of the boil-off gas line is different from the first to third embodiments, so the same reference numerals are given to the same parts as the first to third embodiments and the description thereof will be given, and the overlapping description will be omitted. FIG. 11 is a diagram showing a fuel supply system from a tank to a main engine and auxiliary machinery in a ship according to a fourth embodiment of the present disclosure. As shown in FIG. 11, the ship 1 of the fourth embodiment includes a main supply line 100, an auxiliary machinery supply line 200, and a boil-off gas line 300D for supplying liquefied gas stored in the tank 10 as fuel to the main engine 20 and the auxiliary machinery 30.

[0067] The boil-off gas line 300D can supply boil-off gas BOG generated in the tank 10 to the main engine 20. The upstream end 301 of the boil-off gas line 300D is connected to the tank 10. The downstream end 304 of the boil-off gas line 300D is connected to the main supply line 100 between the pump 11 and the pressure pump 12. The downstream end 304 of the boil-off gas line 300D is connected to the main supply line 100 on the downstream side with respect to the upstream end 201 of the auxiliary machinery supply line 200.

[0068] The boil-off gas line 300D is provided with a gas compressor 55 and a heat exchanger 56. The gas compressor 55 pressurizes the boil-off gas BOG supplied to the main engine 20 through the boil-off gas line 300D. The heat exchanger 56 is provided between the pressure pump 12 and the high-pressure vaporizer 13 in the main supply line 100. The heat exchanger 56 performs heat exchange between the boil-off gas BOG flowing through the boil-off gas line 300D and the liquefied gas LG that has passed through the pressure pump 12 in the main supply line 100.

[0069] The boil-off gas line 300D mixes the boil-off gas BOG pressurized through the gas compressor 55 with the liquefied gas LG flowing through the main supply line 100 after cooling the boil-off gas BOG through heat exchange with the liquefied gas LG in the heat exchanger 56. In an embodiment of the present disclosure, the boil-off gas line 300D mixes the boil-off gas BOG pressurized through the gas compressor 55 with the liquefied gas LG flowing through the main supply line 100 upstream of the pressurizing pump 12. Thereby, the boil-off gas BOG pressurized and cooled through the gas compressor 55 and the heat exchanger 56, together with the liquefied gas LG from the tank 10, is further pressurized by the pressurizing pump 12 and then vaporized in the high-pressure vaporizer 13 and sent to the main engine 20.

[0070] (In-ship power generation method) Next, the in-ship power generation method in the ship 1 as described above will be described. FIG. 12 is a diagram showing the flow of boil-off gas when the first mode is being executed in the in-ship power generation method according to the fourth embodiment of the present disclosure. FIG. 13 is a diagram showing the flow of boil-off gas when the second mode is being executed in the in-ship power generation method according to the fourth embodiment of the present disclosure.

[0071] As shown in FIG. 12, when the ship 1 is sailing with the main engine 20 driving the propeller 9, the ship 1 executes the first mode M21. In the first mode M21, the main engine 20 drives the shaft generator 25, and the shaft generator 25 generates in-ship power. In this case, the first valve 73 is opened and the second valve 74 is closed. Thereby, the boil-off gas BOG from the tank 10 is supplied to the main engine 20 as fuel gas FG through the gas compressor 55, the heat exchanger 56, the pressurizing pump 12, and the high-pressure vaporizer 13. In the first mode M21, the boil-off gas BOG generated during the sailing of the ship 1 is supplied to the main engine 20, and the shaft generator 25 generates in-ship power.

[0072] As shown in FIG. 13, when the ship 1 is at berth and the propeller 9 is not driven by the main engine 20, the ship 1 executes the second mode M22. In the second mode M22, the boil-off gas BOG from the tank 10 is pressurized only through the gas compressor 55, and is supplied as auxiliary engine fuel gas FG2 to the auxiliary engine 30 through the auxiliary engine boil-off gas supply line 400. In the second mode M22, the boil-off gas BOG generated when the ship 1 is at berth is supplied to the auxiliary engine 30, and the auxiliary engine 30 generates in-ship power.

[0073] (Function and Effect) The ship 1 of the above fourth embodiment is provided with a heat exchanger 56. In the heat exchanger 56, heat exchange is performed between the boil-off gas BOG flowing through the boil-off gas line 300D and the liquefied gas LG that has passed through the pressurizing pump 12, thereby cooling the boil-off gas BOG. By mixing the boil-off gas BOG cooled by the heat exchanger 56 with the liquefied gas LG flowing through the main supply line 100, the amount of boil-off gas BOG that can be reliquefied is increased, and the boil-off gas BOG can be consumed efficiently.

[0074] Also, in the above fourth embodiment, similar to the above third embodiment, by mixing the boil-off gas BOG with the pressurized liquefied gas LG flowing through the main supply line 100, the pressure of the boil-off gas BOG increases, and it becomes a state where it is easy to vaporize when supplied as fuel for the main engine 20. In this way, by vaporizing the boil-off gas BOG together with the liquefied gas LG flowing through the main supply line 100, fuel gas FG can be generated efficiently and supplied to the main engine 20.

[0075] Furthermore, in the above fourth embodiment, similar to the above first embodiment, it is provided with a main supply line 100 capable of supplying the liquefied gas LG in the tank 10 to the main engine 20, and a boil-off gas line 300D capable of supplying the boil-off gas BOG in the tank 10 to the main engine 20. Thereby, the boil-off gas BOG can be effectively utilized and the fuel efficiency can be improved.

[0076] <Fifth Embodiment> Next, a fifth embodiment of the ship and the in-ship power generation method according to the present disclosure will be described. In the fifth embodiment described below, only the configuration of the boil-off gas line is different from that of the first to fourth embodiments. Therefore, the same parts as those in the first to fourth embodiments will be denoted by the same reference numerals and described, and redundant descriptions will be omitted. FIG. 14 is a diagram showing a fuel supply system from a tank to a main engine and auxiliary machines in a ship according to a fifth embodiment of the present disclosure. As shown in FIG. 14, a ship 1 according to the fifth embodiment includes a main supply line 100, an auxiliary machine supply line 200, and a boil-off gas line 300E in order to supply liquefied gas stored in a tank 10 as fuel to a main engine 20 and auxiliary machines 30.

[0077] The boil-off gas line 300E can supply boil-off gas BOG generated in the tank 10 to the main engine 20. The upstream end 301 of the boil-off gas line 300E is connected to the tank 10. The boil-off gas line 300E branches into a first line 310 and a second line 320 midway. The downstream end 312 of the first line 310 is connected to the main supply line 100 on the downstream side with respect to the high-pressure vaporizer 13. The downstream end 322 of the second line 320 is connected to the main supply line 100 between the pump 11 and the pressure pump 12. The downstream end 322 of the second line 320 is connected to the main supply line 100 on the downstream side with respect to the upstream end 201 of the auxiliary machine supply line 200.

[0078] The boil-off gas line 300E is provided with a first gas compressor 53 and a second gas compressor 54 as gas compressors 52, and a heat exchanger 56. The first gas compressor 53 is arranged in the boil-off gas line 300E between the tank 10 and the second gas compressor 54. The first gas compressor 53 boosts the boil-off gas BOG from the tank 10 supplied through the boil-off gas line 300E to a first pressure (for example, 0.6 MPa) required as fuel for the auxiliary machine 30 (pressure of the auxiliary machine fuel gas FG2).

[0079] The second gas compressor 54 is provided in the middle of the first line 310 in the boil-off gas line 300E. The second gas compressor 54 further boosts the boil-off gas BOG that has been pressurized to the first pressure through the first gas compressor 53 to the second pressure (for example, 30 MPa) required as fuel for the main engine 20. The boil-off gas line 300E mixes the boil-off gas BOG that has been pressurized through the first gas compressor 53 and the second gas compressor 54 with the main supply line 100 downstream of the high-pressure vaporizer 13. The boil-off gas line 300E mixes a part of the boil-off gas BOG supplied to the main engine 20 with the fuel gas FG vaporized by the high-pressure vaporizer 13 in the main supply line 100.

[0080] The heat exchanger 56 is provided in the middle of the second line 320. The heat exchanger 56 performs heat exchange between the boil-off gas BOG that has been pressurized through the first gas compressor 53 and flows through the boil-off gas line 300E and the liquefied gas LG that has passed through the pressurizing pump 12 in the main supply line 100.

[0081] The boil-off gas line 300E cools a part of the boil-off gas BOG that has been pressurized through the first gas compressor 53 by heat exchange with the liquefied gas LG in the heat exchanger 56, and then mixes it with the liquefied gas LG flowing through the main supply line 100. In the fifth embodiment, the boil-off gas line 300E mixes the boil-off gas BOG that has been pressurized through the first gas compressor 53 with the liquefied gas LG flowing through the main supply line 100 upstream of the pressurizing pump 12. Thereby, the boil-off gas BOG that has been pressurized and cooled through the first gas compressor 53 and the heat exchanger 56, together with the liquefied gas LG from the tank 10, is further pressurized by the pressurizing pump 12, then vaporized by the high-pressure vaporizer 13, and sent to the main engine 20.

[0082] Note that each of the first line 310 and the second line 320 may be provided with an on-off valve, a flow rate adjustment valve, etc., so as to adjust the flow rate balance between the boil-off gas BOG supplied to the second gas compressor 54 and the boil-off gas BOG supplied to the heat exchanger 56. Also, the heat exchanger 56 in this fifth embodiment can be omitted.

[0083] (Method for generating in-ship power) Next, a method for generating in-ship power in the ship 1 as described above will be described. FIG. 15 is a diagram showing the flow of boil-off gas when the first mode is being executed in the method for generating in-ship power according to the fifth embodiment of the present disclosure. FIG. 16 is a diagram showing the flow of boil-off gas when the second mode is being executed in the method for generating in-ship power according to the fifth embodiment of the present disclosure.

[0084] As shown in FIG. 15, when the ship 1 is sailing with the main engine 20 driving the propeller 9, the ship 1 executes the first mode M31. In the first mode M31, the shaft generator 25 is driven by the main engine 20, and in-ship power is generated by the shaft generator 25. In this case, the first valve 71 is opened and the second valve 72 is closed. As a result, a part of the boil-off gas BOG from the tank 10 is sent into the main supply line 100 through the first gas compressor 53 and the second gas compressor 54. The remainder of the boil-off gas BOG from the tank 10 is supplied to the main engine 20 as fuel gas FG through the first gas compressor 53, the heat exchanger 56, the pressurizing pump 12, and the high-pressure vaporizer 13. Thus, in the first mode M31, the boil-off gas BOG generated during the navigation of the ship 1 is supplied to the main engine 20, and in-ship power is generated by the shaft generator 25.

[0085] As shown in FIG. 16, when the ship 1 is at berth and the main engine 20 is not driving the propeller 9, the ship 1 executes the second mode M32. In the second mode M32, the boil-off gas BOG from the tank 10 is pressurized through only the first gas compressor 53 and supplied to the auxiliary machinery 30 as auxiliary machinery fuel gas FG2 through the auxiliary machinery boil-off gas supply line 400. In the second mode M32, the boil-off gas BOG generated during the berthing of the ship 1 is supplied to the auxiliary machinery 30, and in-ship power is generated by the auxiliary machinery 30.

[0086] (Function and effect) The ship 1 of the above-described fifth embodiment can supply boil-off gas BOG to the main engine 20 as fuel for the main engine 20 together with the liquefied gas LG flowing through the main supply line 100 by mixing the boil-off gas BOG boosted in two stages by the first gas compressor 53 and the second gas compressor 54 with the liquefied gas LG flowing through the main supply line 100.

[0087] Also, in the above-described fifth embodiment, heat exchange is performed between the boil-off gas BOG flowing through the boil-off gas line 300E and the liquefied gas LG that has passed through the pressure pump 12 in the heat exchanger 56, thereby cooling the boil-off gas BOG. By mixing the boil-off gas BOG cooled by the heat exchanger 56 with the liquefied gas LG flowing through the main supply line 100, it becomes easier to reliquefy the boil-off gas BOG, increases the amount of boil-off gas BOG that can be reliquefied, and enables efficient consumption of the boil-off gas BOG.

[0088] Furthermore, in the above-described fifth embodiment, similar to the first embodiment, it includes a main supply line 100 capable of supplying the liquefied gas LG in the tank 10 to the main engine 20 and a boil-off gas line 300E capable of supplying the boil-off gas BOG in the tank 10 to the main engine 20. Thereby, the boil-off gas BOG can be effectively utilized and the fuel efficiency can be improved.

[0089] <Appendix> The ship 1 and the in-ship power generation method described in each embodiment can be understood as follows, for example.

[0090] (1) The ship 1 according to the first aspect includes a hull 2 having a propeller 9, a main engine 20 provided on the hull 2 for driving the propeller 9, a shaft generator 25 that is driven in accordance with the rotation of the main engine 20 to generate in-ship power, a tank 10 provided on the hull 2 in which the liquefied gas LG can be stored, a main supply line 100 capable of vaporizing the liquefied gas LG in the tank 10 and supplying it to the main engine 20, and boil-off gas lines 300A to 300E capable of supplying the boil-off gas BOG in the tank 10 to the main engine 20.

[0091] As a result, the main engine 20 can use both the liquefied gas LG in the tank 10 and the boil-off gas BOG generated in the tank 10 as fuel. When driving the propeller 9 with such a main engine 20, by driving the shaft generator 25 along with the rotation of the main engine 20, in-ship power can be generated using the main engine 20 with high fuel efficiency. Therefore, even when the main engine 20 that requires high-pressure gas as fuel is provided, the boil-off gas BOG can be effectively utilized to improve the fuel efficiency.

[0092] (2) The ship 1 according to the second aspect is the ship 1 of (1), and further includes an auxiliary machine 30 that generates in-ship power by fuel supply. The boil-off gas line 300B can supply the boil-off gas BOG to the auxiliary machine 30 in addition to the main engine 20, and is provided with a switching unit 70 that can selectively switch the supply destination of the boil-off gas BOG by the boil-off gas line 300B between the main engine 20 and the auxiliary machine 30.

[0093] As a result, when the main engine 20 is operating, the boil-off gas BOG can be supplied to the main engine 20, and when the auxiliary machine 30 is operating, the boil-off gas BOG can be supplied to the auxiliary machine 30. Therefore, the boil-off gas BOG generated in the tank 10 can be prevented from being wasted and can be effectively consumed by the main engine 20 and the auxiliary machine 30.

[0094] (3) The ship 1 according to the third aspect is the ship 1 of (1) or (2), and the main supply line 100 includes a pressure pump 12 that pressurizes the liquefied gas LG and a vaporizer 13 that vaporizes the liquefied gas LG pressurized by the pressure pump 12 to generate fuel gas that becomes the fuel of the main engine 20. The boil-off gas lines 300A and 300B are provided with gas compressors 51 and 52 that can pressurize the boil-off gas BOG to the pressure of the fuel gas supplied to the main engine 20.

[0095] As a result, it becomes possible to use boil-off gas (BOG) as high-pressure fuel gas supplied to the main engine 20. Therefore, the boil-off gas (BOG) can be effectively utilized to improve fuel efficiency.

[0096] (4) The ship 1 according to the fourth aspect is the ship 1 in (2), wherein the boil-off gas lines 300B and 300E include a first gas compressor 53 that boosts the boil-off gas (BOG) to a first pressure required as fuel for the auxiliary machine 30, and a second gas compressor 54 that further boosts the boil-off gas (BOG) boosted to the first pressure by the first gas compressor 53 to a second pressure required as fuel for the main engine 20.

[0097] As a result, the boil-off gas (BOG) can be boosted in two stages by the first gas compressor 53 and the second gas compressor 54. Therefore, it can be supplied to the auxiliary machine 30 as fuel for the auxiliary machine 30, and the boosted boil-off gas (BOG) can be supplied to the main engine 20 as fuel for the main engine 20.

[0098] (5) The ship 1 according to the fifth aspect is the ship 1 in (4), wherein the boil-off gas line 300E mixes the boil-off gas (BOG) boosted by the first gas compressor 53 with the liquefied gas (LG) flowing in the main supply line 100.

[0099] As a result, by mixing the boil-off gas (BOG) boosted by the first gas compressor 53 with the liquefied gas (LG) flowing in the main supply line 100, the boil-off gas (BOG) can be supplied to the main engine 20 as fuel for the main engine 20 together with the liquefied gas (LG) flowing in the main supply line 100.

[0100] (6) The ship 1 according to the sixth aspect is the ship 1 of (5), wherein the main supply line 100 includes a pressure pump 12 for pressurizing the liquefied gas LG and a vaporizer 13 for vaporizing the liquefied gas LG pressurized by the pressure pump 12 to generate fuel gas that becomes the fuel of the main engine 20, and further includes a heat exchanger 56 that performs heat exchange between the boil-off gas BOG pressurized by the first gas compressor and the liquefied gas LG that has passed through the pressure pump 12 of the main supply line 100.

[0101] Thereby, the boil-off gas BOG before being mixed with the liquefied gas LG is cooled. Therefore, by mixing the boil-off gas BOG cooled by the heat exchanger 56 with the liquefied gas LG flowing through the main supply line 100, the boil-off gas BOG becomes even more easily re-liquefied.

[0102] (7) The ship 1 according to the seventh aspect is the ship 1 of any one of (1) to (6), wherein the main supply line 100 includes a pressure pump 12 for pressurizing the liquefied gas LG and a vaporizer 13 for evaporating the liquefied gas LG pressurized by the pressure pump 12 to generate fuel gas that becomes the fuel of the main engine 20, and the boil-off gas lines 300C and 300D mix the boil-off gas BOG supplied to the main engine 20 with the liquefied gas LG flowing through the main supply line 100.

[0103] Thereby, since the boil-off gas BOG is cooled and re-liquefied by the liquefied gas LG flowing through the main supply line 100, it can be efficiently supplied to the main engine 20 as fuel for the main engine 20.

[0104] (8) The ship 1 according to the eighth aspect is the ship 1 of (7), and further includes a heat exchanger 56 that performs heat exchange between the boil-off gas BOG flowing through the boil-off gas line 300D and the liquefied gas LG that has passed through the pressure pump 12 of the main supply line 100.

[0105] As a result, the boil-off gas BOG cooled by the heat exchanger 56 can be mixed with the liquefied gas LG flowing through the main supply line 100, making the boil-off gas BOG even easier to reliquefy.

[0106] (9) The in-ship power generation method according to the ninth aspect is the in-ship power generation method in the ship 1 of (2), and includes a first mode M1, M11, M21, M31 in which boil-off gas BOG is supplied to the main engine 20 during navigation of the ship 1 to generate in-ship power by the shaft generator 25, and a second mode M2, M12, M22, M32 in which the boil-off gas BOG is supplied to the auxiliary machine 30 during berthing of the ship 1 to generate in-ship power by the auxiliary machine 30, and these modes are switched.

[0107] As a result, when the main engine 20 is operating during navigation of the ship 1, in-ship power is generated by the main engine 20, and when the auxiliary machine 30 is operating during berthing of the ship 1, in-ship power can be generated by the auxiliary machine 30. Therefore, the boil-off gas BOG generated in the tank 10 can be prevented from being wasted and can be effectively utilized to generate in-ship power by the main engine 20 and the auxiliary machine 30. As a result, the boil-off gas can be effectively utilized and the fuel efficiency can be improved.

Explanation of reference numerals

[0108] 1…Ship 2…Hull 2b…Stern 3A, 3B…Side 4…Bottom 5…Upper deck 7…Superstructure 8…Propeller shaft 9…Propeller 10…Tank 11…Pump 12…Pressurizing pump 13…Vaporizer 13…High-pressure vaporizer 20…Main engine 25…Shaft generator 30…Auxiliary machine 31…Vaporizer for auxiliary machine 51…High-pressure gas compressor (gas compressor) 51, 52, 55…Gas compressor 53…First gas compressor 54…Second gas compressor 56…Heat exchanger 70, 70B…Switching section 71, 73…First valve 72, 74…Second valve 100…Main supply line 105, 205, 305…Valve 200…Auxiliary machine supply line 201, 301…Upstream end 202, 302, 303, 304, 312, 322…Downstream end 300A~300E…Boil-off gas line 310…First line 320…Second line 400…Auxiliary machine boil-off gas supply line M1, M11, M21, M31…First mode M2, M12, M22, M32…Second mode

Claims

1. A hull having a propeller; A main engine provided on the hull for driving the propeller; A shaft generator that is driven as the main engine rotates to generate in-ship power; A tank provided on the hull and capable of storing liquefied gas; A main supply line that vaporizes the liquefied gas stored in the tank and can supply it to the main engine; A boil-off gas line that can supply the boil-off gas generated in the tank to the main engine; A ship comprising:

2. Further comprising an auxiliary machine that generates in-ship power by fuel supply, The boil-off gas line is configured to be able to supply the boil-off gas to the auxiliary machine in addition to the main engine, and a switching unit that can selectively switch the supply destination of the boil-off gas by the boil-off gas line between the main engine and the auxiliary machine. The ship according to claim 1.

3. The main supply line includes a pressure pump that pressurizes the liquefied gas and a vaporizer that vaporizes the liquefied gas pressurized by the pressure pump to generate fuel gas that becomes fuel for the main engine, The boil-off gas line includes a gas compressor that can pressurize the boil-off gas to the pressure of the fuel gas supplied to the main engine. The ship according to claim 1 or 2.

4. The boil-off gas line includes a first gas compressor that boosts the boil-off gas to a first pressure required as fuel for the auxiliary machine, and a second gas compressor that further boosts the boil-off gas boosted to the first pressure by the first gas compressor to a second pressure required as fuel for the main engine. Comprising: The ship according to claim 2.

5. The boil-off gas line Mix the boil-off gas pressurized by the first gas compressor with the liquefied gas flowing in the main supply line. The ship according to claim 4.

6. The main supply line is provided with a pressurizing pump for pressurizing the liquefied gas and a vaporizer for vaporizing the liquefied gas pressurized by the pressurizing pump to generate fuel gas that becomes fuel for the main engine. Further provided is a heat exchanger that performs heat exchange between the boil-off gas pressurized by the first gas compressor and the liquefied gas that has passed through the pressurizing pump in the main supply line. The ship according to claim 5.

7. The main supply line is provided with a pressurizing pump for pressurizing the liquefied gas and a vaporizer for vaporizing the liquefied gas pressurized by the pressurizing pump to generate fuel gas that becomes fuel for the main engine. The boil-off gas line mixes the boil-off gas supplied to the main engine with the liquefied gas flowing in the main supply line. The ship according to claim 1 or 2.

8. Further provided is a heat exchanger that performs heat exchange between the boil-off gas flowing through the boil-off gas line and the liquefied gas that has passed through the pressurizing pump in the main supply line. The ship according to claim 7.

9. A method for generating in-ship electric power in the ship according to claim 2, comprising: A first mode in which boil-off gas is supplied to the main engine during navigation of the ship to generate in-ship electric power by the shaft generator; and A second mode in which the boil-off gas is supplied to the auxiliary machinery during berthing of the ship to generate in-ship electric power by the auxiliary machinery, and switching between the two modes. A method for generating in-ship electric power.

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