JP7818564B2 - Marine fuel supply system - Google Patents

Description

The present invention relates to a fuel supply system for a ship that supplies liquid fuel stored in multiple fuel tanks to the ship's engine, and more specifically to a fuel supply system for a ship that does not require the installation of individual pumps in each fuel tank.

In recent years, as described in Non-Patent Document 1, liquefied gas fuels such as liquefied ammonia and liquefied petroleum gas (LPG) have been used as ship fuel. Long voyages require large amounts of liquefied gas fuel to be carried on board ships. In particular, when using liquefied ammonia as fuel, it has a lower calorific value than petroleum gas, so large quantities must be carried on board.

When manufacturing large-capacity fuel tanks, heat treatment and other measures are required to prevent damage due to stress and corrosion. However, heat treatment equipment for large-capacity fuel tanks requires an annealing furnace the same size as the fuel tank, which requires a large facility and limited space for installation. For this reason, multiple small-capacity fuel tanks, which can be manufactured in smaller facilities, are used to ensure the required capacity.

Patent Document 1 proposes a method of supplying fuel to a pump by supplying warm air to the fuel tank to increase the internal pressure of the fuel tank. However, this method is undesirable because it requires the fuel tank's design pressure to be sufficiently high and there is a risk of fire.

Japanese Patent Application Laid-Open No. 2021-123119

Nippon Kaiji Kyokai Alternative Fuel Ship Guidelines (Version 2.0) (Methanol/Ethanol/LPG/Ammonia) Part C-1

Fuel tanks for ships are classified into pressure vessels (pressurized type) that store fuel at room temperature and high pressure, full-refrigerated type that stores fuel at low temperature and atmospheric pressure, and semi-refrigerated type that stores fuel at semi-low temperature with an internal pressure of 1 MPa or less.

Semi-refrigerated and fully refrigerated fuel tanks are generally equipped with re-liquefaction equipment to process evaporated gases for temperature control purposes. To prevent liquid fuel leaks on board, ship regulations stipulate that the fuel outlet must be located above the liquid level, where gas leakage is minimal, and that the fuel must be extracted from above the liquid level.

In addition, pressure vessels (pressurized type) that do not need to be removed from a position higher than the liquid level are classified as Class 1, Class 2, and Class 3 pressure vessels according to NK Steel Ship Rules, Part D, 10.1.3. Each of the Class 1 and Class 2 vessels specifies the thickness of the copper plate, design pressure, maximum operating temperature, and design pressure of the steam pressure generator. Class 3 pressure vessels are pressure vessels that do not fall into either the Class 1 or Class 2 pressure vessel category.

When the fuel outlet is higher than the liquid level, a deepwell pump attached to the tank or a submerged pump installed inside the tank is used. If there are multiple fuel tanks on a ship, a deepwell or submerged pump must be installed for each fuel tank. Therefore, as the number of fuel tanks increases, the number of pumps required also increases, resulting in a significant increase in installation costs.

Also, when performing maintenance on the pump, if an inner pipe surrounding the pump is installed inside the fuel tank, only the fuel inside the inner pipe needs to be removed, but even in this case, it takes a long time to remove the pump from the fuel tank.

Furthermore, when using a deepwell pump, the height of the pump is roughly equal to the height of the fuel tank, so if multiple fuel tanks are stacked on top of each other, the pump cannot be removed from the lower fuel tank, making it impossible to stack fuel tanks on top of each other. As a result, the number of fuel tanks that can be installed vertically in a given space cannot be increased.

The objective of the present invention is to provide a fuel supply system for a ship that supplies liquid fuel stored in multiple fuel tanks to the ship's engine, without the need to install individual pumps in each fuel tank.

Further objects of the present invention will become apparent from the following description.

The above problems are solved by the following inventions.
1.
A fuel supply device for a ship that supplies liquid fuel stored in a plurality of fuel tanks to an engine of the ship,
a plurality of extraction pipes for extracting the liquid fuel from each of the fuel tanks, the extraction pipes being located above the liquid level of the liquid fuel stored in each of the fuel tanks;
a buffer tank to which the liquid fuel is delivered via the plurality of extraction pipes;
a pump that supplies the liquid fuel in the buffer tank to an engine of the ship;
a negative pressure generating device that generates a negative pressure in a space above the liquid fuel level in the buffer tank and sucks out the liquid fuel from each of the fuel tanks.
2.
2. The fuel supply system for a marine vessel according to claim 1, wherein the buffer tank is a tank that does not require withdrawal of fuel from above the liquid level in the tank.
3.
a liquid level of the liquid fuel in the buffer tank is lower than a liquid level of the liquid fuel stored in each of the fuel tanks;
2. The fuel supply device for a marine vessel according to claim 1, wherein a siphon is formed from the liquid fuel stored in each of the fuel tanks through each of the extraction pipes to an end of the extraction pipe in the buffer tank.
4.
2. The fuel supply system for a marine vessel according to claim 1, wherein the negative pressure generating device is a re-liquefaction device.
5.
2. The fuel supply system for a boat according to claim 1, wherein the negative pressure generating device is a gas compressor.
6.
2. The fuel supply system for a ship according to claim 1, wherein the negative pressure generating device is a denitration device.
7.
2. The fuel supply system for a boat according to claim 1, wherein at least two of the fuel tanks are stacked one above the other.
8.
8. The marine vessel fuel supply device according to any one of 1 to 7, wherein the plurality of fuel tanks are loaded onto the marine vessel and connected to the extraction pipes while storing the liquid fuel, and are detached from the extraction pipes and lowered from the marine vessel when the liquid fuel is consumed and the stored amount is reduced.
9.
8. The fuel supply system for a marine vessel according to any one of 1 to 7, further comprising gas supply and discharge pipes connecting each of the fuel tanks to an outside facility.
10.
8. The marine fuel supply device according to any one of 1 to 7, further comprising a buffer tank pressure reduction pipe that connects a location downstream of a flow rate control valve provided in the withdrawal pipe leading to the buffer tank with a location upstream of the flow rate control valve, and that has a pressure reduction valve provided midway.

According to the present invention, it is possible to provide a fuel supply device for a ship that supplies liquid fuel stored in a plurality of fuel tanks to the engine of the ship, and that does not require the installation of individual pumps in each fuel tank.
In this fuel supply system for a boat, it is not necessary to provide a plurality of pumps for each fuel tank, and liquid fuel can be supplied from the buffer tank to the boat's engine with a single pump.

FIG. 1 is a block diagram showing the configuration of a fuel supply system for a boat according to a first embodiment of the present invention; FIG. 10 is a block diagram showing the configuration of a fuel supply system for a boat according to a second embodiment of the present invention. FIG. 10 is a block diagram showing the configuration of a fuel supply system for a boat according to a third embodiment of the present invention. FIG. 10 is a block diagram showing the configuration of a fuel supply system for a boat according to a fourth embodiment of the present invention. FIG. 10 is a block diagram showing the configuration of a fuel supply system for a boat according to a fifth embodiment of the present invention. FIG. 10 is a block diagram showing the configuration of a fuel supply system for a boat according to a sixth embodiment of the present invention. 1 is a block diagram showing the configuration of a fuel supply system for a marine vessel according to a first improved embodiment of the present invention;

The following describes a preferred embodiment of the present invention.

First Embodiment
A fuel supply system for a boat according to the present invention is a fuel supply system for a boat that supplies liquid fuel stored in a plurality of fuel tanks to an engine of a boat.
FIG. 1 is a block diagram showing the configuration of a fuel supply system for a boat according to a first embodiment of the present invention.

As shown in Figure 1, the marine fuel supply system of this embodiment includes multiple fuel tanks 1a, 1b, 1c, and 1d that store liquid fuel L to be supplied to the marine engine. In this description, the number of fuel tanks 1a, 1b, 1c, and 1d is four, but this number is not limited to four and may be two, three, five, or more.

A ship's engines include not only propulsion engines, but also generators, boilers, and all other engines that generate energy by burning liquid fuel L.

In this embodiment, the liquid fuel L is a liquefied gas fuel such as liquefied ammonia (NH3), liquefied natural gas (LNG), or liquefied petroleum gas (LPG).

Each fuel tank 1a, 1b, 1c, 1d is provided with multiple extraction pipes 4a, 4b, 4c, 4d for extracting liquid fuel L above the liquid level of the stored liquid fuel L. Each extraction pipe 4a, 4b, 4c, 4d is connected to a portion corresponding to each fuel tank 1a, 1b, 1c, 1d, and then converges into a single pipe that leads to a buffer tank 5.

Each extraction pipe 4a, 4b, 4c, and 4d is provided with an on-off valve 6a, 6b, 6c, and 6d corresponding to each fuel tank 1a, 1b, 1c, and 1d. Furthermore, a flow control valve 7 is provided at the joint of each extraction pipe 4a, 4b, 4c, and 4d.

A gas treatment device 14 is connected to the junction of the withdrawal pipes 4a, 4b, 4c, and 4d. The gas treatment device 14 treats the gas inside the withdrawal pipes 4a, 4b, 4c, and 4d. Examples of gas treatment include purging.

In addition, the withdrawal pipes 4a, 4b, 4c, and 4d may each lead to the buffer tank 5 individually, rather than being combined. In this case, multiple flow control valves 7 and gas processing devices 14 are provided for each of the withdrawal pipes 4a, 4b, 4c, and 4d.

In Figures 1 to 7, the piping from each extraction pipe 4a, 4b, 4c, and 4d to the gas treatment device 14 is indicated by dotted lines indicating the gas flow path, but there is a possibility that liquid (liquid droplets) may be mixed into this piping. In this case, it is preferable to install a gas-liquid separator and send only the gas to the gas treatment device 14 through the gas-liquid separator.

Liquid fuel L is delivered to the buffer tank 5 via multiple extraction pipes 4a, 4b, 4c, and 4d. The buffer tank 5 is connected to a re-liquefaction device 8, which is a negative pressure device that creates a negative pressure in the space above the liquid level of the liquid fuel L in the buffer tank 5 and sucks out the liquid fuel L from each of the fuel tanks 1a, 1b, 1c, and 1d. A pressure reducing valve 9 is provided between the buffer tank 5 and the re-liquefaction device 8. The pressure reducing valve 9 is an on-off valve.

In this embodiment, the negative pressure device is a re-liquefaction device 8. The re-liquefaction device 8 compresses, or compresses and cools, the vaporized gas in the space above the liquid level of the liquid fuel L in the buffer tank 5, and re-liquefies it. In FIG. 1, the liquid flow path is shown by a solid line, and the gas flow path is shown by a dotted line. This is also true in the other drawings described below. Note that in some of the other embodiments described below, the negative pressure device is a gas compressor and/or denitration equipment.

The liquid fuel L in the buffer tank 5 is supplied by pump 10 through a mixing tank 11 and via a fuel supply line to the ship's engine 12, such as a propulsion engine. In the mixing tank 11, the liquid fuel L from the buffer tank 5 is mixed with the liquid fuel reliquefied by the reliquefaction device 8. The liquid fuel reliquefied by the reliquefaction device 8 is sent to the mixing tank 11 via check valve 8a, where it is mixed with the liquid fuel L from the buffer tank 5 and supplied to the ship's engine 12. The mixing tank 11 may be replaced with a mixer.

The fuel supply line may be provided with various devices (not shown) for supplying fuel to the engine 12 of the ship, as well as a gas-liquid separator. Examples of the various devices for supplying fuel include a compressor, a high-pressure pump, and a heat exchanger.
In addition, the fuel supply line may be supplied with inert gas to purge residual vaporized gas when the ship's engine 12 is started, stopped, or in an emergency stop, and this inert gas, together with the residual vaporized gas, is introduced into the detoxification device via a gas-liquid separator.
The gas-liquid separator through which the gas introduced into the detoxification device passes may also be used for the gas sent to the gas treatment device 14. In this case, if the buffer tank 5 is empty, the gas in the extraction pipes 4a, 4b, 4c, and 4d passes through the buffer tank 5, the fuel supply line, and the gas-liquid separator, and is sent to the gas treatment device 14 for treatment.

In this embodiment, the liquid fuel reliquefied by the reliquefaction device (negative pressure device) 8 is used in the ship's engine 12, so the liquid fuel is used without waste. Note that the liquid fuel reliquefied by the reliquefaction device 8 may also be used in the ship's auxiliary engines rather than the main engine.

In this marine fuel supply system, the liquid fuel L in the buffer tank 5 can be supplied to the marine engine 12 using a single pump 10, eliminating the need to provide multiple pumps for each fuel tank 1a, 1b, 1c, and 1d. This simplifies pump maintenance and reduces installation costs.

The buffer tank 5 may be provided with upper and lower liquid level sensors (level switches) 13u, 13d for controlling the liquid level position within the buffer tank 5. The upper liquid level sensor 13u is provided at the upper limit of the liquid level of the liquid fuel L within the buffer tank 5. The lower liquid level sensor 13d is provided at the lower limit of the liquid level of the liquid fuel L within the buffer tank 5.

When the upper liquid level sensor 13u detects the liquid level of the liquid fuel L, the flow rate control valve 7 is controlled to close, and the transfer of the liquid fuel L from each of the fuel tanks 1a, 1b, 1c, and 1d to the buffer tank 5 is blocked. When the lower liquid level sensor 13d detects the liquid level of the liquid fuel L, the flow rate control valve 7 and the pressure reducing valve 9 are controlled to open, and the pressure inside the buffer tank 5 can be reduced and the liquid fuel L can be transferred to the buffer tank 5. The amount of liquid fuel L transferred to the buffer tank 5 is regulated by the opening degree of the flow rate control valve 7.

Fuel tanks 1a, 1b, 1c, and 1d are connected to supply pipes 2 for supplying liquid fuel L from bunkering equipment 100 outside the ship, such as a bunker ship. One pipe on the supply pipe 2 connected to the bunkering equipment 100 branches off at the fuel tanks 1a, 1b, 1c, and 1d sides, and these are connected to the fuel tanks 1a, 1b, 1c, and 1d. Opening/closing valves 3a, 3b, 3c, and 3d are provided at the branched portions of the supply pipe 2, corresponding to each of the fuel tanks 1a, 1b, 1c, and 1d.

To supply liquid fuel L to each fuel tank 1a, 1b, 1c, and 1d via supply pipe 2, one pipe on the bunkering equipment 100 side is connected to the bunkering equipment 100, each on-off valve 3a, 3b, 3c, and 3d is opened, and the liquid fuel L is sent to each fuel tank 1a, 1b, 1c, and 1d by the pump of the bunkering equipment 100.

[About the buffer tank]
The buffer tank 5 is preferably a tank that does not require withdrawal from above the liquid level, for example, a pressure vessel as defined in the NK Steel Ship Rules. If the buffer tank 5 is a tank that does not require withdrawal from above the liquid level, the liquid fuel L in the buffer tank 5 may be withdrawn from below the liquid level. Therefore, various types of pumps, such as diaphragm pumps and canned motor pumps, can be used as the pump 10 that supplies the liquid fuel L from the buffer tank 5 to the ship's engine 12. Diaphragm pumps and canned motor pumps are preferred because they can easily pump liquid at high pressure. Submerged pumps and deepwell pumps cannot raise the pressure to the desired level in a single stage depending on the fluid, so they are designed to use a two-stage pressure boost. Diaphragm pumps and canned motor pumps can raise the pressure to the desired level in a single stage.

According to the NK Shipbuilding Rules, Part D, 13.9.1-7, each fuel tank 1a, 1b, 1c, and 1d must have a capacity capable of maintaining the ship's engine (main engine) 12 at maximum continuous output and the generator at normal load for at least eight hours. On the other hand, if fuel tanks 1a, 1b, 1c, and 1d are present, buffer tank 5 is considered a process pressure vessel under the NK Shipbuilding Rules. Process pressure vessels under the NK Shipbuilding Rules are not subject to the requirement to drain liquid from above the tank's liquid level.

Here, NK Rules for Steel Ships refers to the rules for steel ships issued by Nippon Kaiji Kyokai (Class NK).

[Regarding the formation of siphons from each fuel tank]
It is preferable that the liquid level of the liquid fuel L in the buffer tank 5 be lower than the liquid level of the liquid fuel L stored in each of the fuel tanks 1a, 1b, 1c, and 1d so that a siphon is formed from the liquid fuel L stored in each of the fuel tanks 1a, 1b, 1c, and 1d through each of the withdrawal pipes 4a, 4b, 4c, and 4d to the end of the withdrawal pipe in the buffer tank 5. When the siphon is formed, the liquid fuel L is sucked out of each of the fuel tanks 1a, 1b, 1c, and 1d and sent to the buffer tank 5 without the need to reduce the pressure inside the buffer tank 5 by the re-liquefaction device 8. This reduces the energy consumption of the re-liquefaction device 8.

[About stacking fuel tanks]
It is preferable that at least two of the fuel tanks 1a, 1b, 1c, and 1d are stacked one above the other. By stacking the fuel tanks 1a, 1b, 1c, and 1d one above the other, the floor area occupied by the fuel tank per stored amount of fuel is reduced, and combined with the fact that the pump is installed separately, volume can be saved.

[Reducing bunkering time]
In this marine fuel supply system, it is also preferable that the multiple fuel tanks 1a, 1b, 1c, and 1d are loaded onto the marine vessel while storing liquid fuel L, and are connected to extraction pipes 4a, 4b, 4c, and 4d, and then, when the liquid fuel L is consumed and the stored amount decreases, the fuel tanks are detached from the extraction pipes 4a, 4b, 4c, and 4d and unloaded from the marine vessel. In this case, the supply pipe 2 is not necessary. In this case, it is also preferable to use IBC tanks (Intermediate Bulk Container Tanks) as the fuel tanks 1a, 1b, 1c, and 1d. Because IBC tanks are container-shaped, this reduces the amount of reloading work.

When disconnecting fuel tanks 1a, 1b, 1c, 1d from withdrawal pipes 4a, 4b, 4c, 4d, on-off valves 6a, 6b, 6c, 6d and flow rate control valve 7 are closed, and the withdrawal pipes 4a, 4b, 4c, 4d between these on-off valves 6a, 6b, 6c, 6d and flow rate control valve 7 are purged by gas treatment device 14. The purged section is then isolated, preventing leakage of liquid fuel from within the withdrawal pipes 4a, 4b, 4c, 4d. For safety reasons, an additional on-off valve 6a, 6b, 6c, 6d may be added.

If multiple fuel tanks 1a, 1b, 1c, and 1d are loaded onto a ship with liquid fuel L stored in them and then unloaded from the ship with a reduced amount of liquid fuel L stored in them, each fuel tank 1a, 1b, 1c, and 1d can be filled with liquid fuel L in advance, significantly shortening the bunkering time without relying on the supply flow rate of equipment such as pumps that bunker the liquid fuel.

Second Embodiment
2 is a block diagram showing the configuration of a fuel supply system for a marine vessel according to a second embodiment of the present invention. The same reference numerals as in FIG. 1 designate the same components, and unless otherwise specified, the description in FIG. 1 is used and will not be repeated here.

In this embodiment, the liquid fuel is a liquefied gas fuel.

In this embodiment, as shown in FIG. 2, the re-liquefaction device 8, which is a negative pressure device, returns the re-liquefied liquid fuel to each fuel tank 1a, 1b, 1c, and 1d, rather than to the mixing tank 11. The liquid fuel re-liquefied by the re-liquefaction device (negative pressure device) 8 is returned to each fuel tank 1a, 1b, 1c, and 1d via return piping 16.

The return pipe 16 has one pipe connected to the reliquefaction device 8, which branches off at the fuel tanks 1a, 1b, 1c, and 1d sides and is connected to each of the fuel tanks 1a, 1b, 1c, and 1d. The branched portions of the return pipe 16 are provided with on-off valves 15a, 15b, 15c, and 15d corresponding to each of the fuel tanks 1a, 1b, 1c, and 1d.

The liquid fuel reliquefied by the reliquefaction device 8 is returned to each fuel tank 1a, 1b, 1c, and 1d and used in the ship's engine 12, ensuring that the liquid fuel is used without waste.

Note that, depending on the amount of liquid fuel extracted from each fuel tank 1a, 1b, 1c, and 1d and the amount consumed by the engine 12, in order to utilize the liquid fuel reliquefied by the reliquefaction device 8, it is preferable to return it to each fuel tank 1a, 1b, 1c, and 1d as described above, rather than to the buffer tank 5. This is because if it were returned to the buffer tank 5, there would be no pressure difference between the fuel tanks 1a, 1b, 1c, and 1d and the buffer tank 5.

In this embodiment, the liquid fuel re-liquefied by the vacuum device is used in the ship's engine 12, so the liquid fuel is used without waste.

Also, in this embodiment, there is no need to provide multiple pumps for each fuel tank 1a, 1b, 1c, and 1d, which simplifies pump maintenance and reduces installation costs. Furthermore, by stacking the fuel tanks 1a, 1b, 1c, and 1d one above the other, combined with the fact that the pumps are installed separately, it is possible to reduce the volume of the system. Furthermore, if a siphon is formed from the liquid fuel L stored in each fuel tank 1a, 1b, 1c, and 1d to the end of the extraction pipe in the buffer tank 5, it is not necessary to reduce the pressure inside the buffer tank 5, which reduces the energy consumption of the re-liquefaction device 8.
If each fuel tank 1a, 1b, 1c, and 1d is loaded onto the ship with liquid fuel L stored in advance, the bunkering time can be significantly reduced without relying on the supply flow rate of a bunkering pump or the like.
If the buffer tank 5 is a tank that does not require the liquid to be drawn from above the tank's liquid surface, various types of pumps can be used for the buffer tank 5, such as a diaphragm pump or a canned motor pump.

Third Embodiment
3 is a block diagram showing the configuration of a fuel supply system for a boat according to a third embodiment of the present invention. The same reference numerals as those in FIGS. 1 and 2 designate the same components, and unless otherwise specified, the explanations in FIGS. 1 and 2 are used and will not be repeated here.

In this embodiment, the liquid fuel L includes not only liquefied gas fuel, but also various other liquid fuels such as methanol, heavy oil, and light oil.

In this embodiment, as shown in Figure 3, a gas compressor 17 is provided as a negative pressure device instead of the reliquefaction device 8 in the second embodiment.

The gas compressor 17 compresses the gas in the space above the liquid level of the liquid fuel L in the buffer tank 5, creating a negative pressure in this space. The vaporized gas compressed by the gas compressor 17 is returned to each fuel tank 1a, 1b, 1c, and 1d via the return pipe 16.

As in the second embodiment, the return pipe 16 has one pipe connected to the gas compressor 17, which branches off at the fuel tanks 1a, 1b, 1c, and 1d and is connected to each of the fuel tanks 1a, 1b, 1c, and 1d. The branched portions of the return pipe 16 are provided with on-off valves 15a, 15b, 15c, and 15d corresponding to each of the fuel tanks 1a, 1b, 1c, and 1d.

When the lower liquid level sensor 13d detects the liquid level of the liquid fuel L, the gas compressor 17 is activated, reducing the pressure inside the buffer tank 5 and pressurizing each of the fuel tanks 1a, 1b, 1c, and 1d, thereby sending the liquid fuel L to the buffer tank 5.

In this embodiment, the gas in the buffer tank 5 is returned to each of the fuel tanks 1a, 1b, 1c, and 1d, thereby increasing the pressure difference between the air pressure in the buffer tank 5 and the air pressure in each of the fuel tanks 1a, 1b, 1c, and 1d. This allows the liquid fuel L in each of the fuel tanks 1a, 1b, 1c, and 1d, which is at high pressure, to be efficiently transferred to the buffer tank 5, which is at low pressure.

Furthermore, if the liquid fuel L is liquefied gas fuel, the liquid fuel is returned to each fuel tank 1a, 1b, 1c, and 1d and re-liquefied, and used in the ship's engine 12, which has the effect of ensuring that the liquid fuel is used without waste.

Also, in this embodiment, there is no need to provide multiple pumps for each fuel tank 1a, 1b, 1c, and 1d, which simplifies pump maintenance and reduces installation costs. Furthermore, stacking the fuel tanks 1a, 1b, 1c, and 1d one above the other, coupled with the separate pumps, allows for reduced volume. Furthermore, if a siphon is formed from the liquid fuel L stored in each fuel tank 1a, 1b, 1c, and 1d to the end of the extraction pipe in the buffer tank 5, there is no need to reduce the pressure inside the buffer tank 5, which reduces the energy consumption of the negative pressure device.
If each fuel tank 1a, 1b, 1c, and 1d is loaded onto the ship with liquid fuel L stored in advance, the bunkering time can be significantly reduced without relying on the supply flow rate of a bunkering pump or the like.
If the buffer tank 5 is a tank that does not require the liquid to be drawn from above the tank's liquid surface, various types of pumps can be used for the buffer tank 5, such as a diaphragm pump or a canned motor pump.

Fourth Embodiment
4 is a block diagram showing the configuration of a fuel supply system for a marine vessel according to a fourth embodiment of the present invention. The same reference numerals as in FIG. 1 designate the same components, and unless otherwise specified, the description in FIG. 1 is used and will not be repeated here.

In this embodiment, the liquid fuel is liquefied ammonia.

In this embodiment, as shown in Figure 4, a gas compressor 17 is provided as a negative pressure device instead of the reliquefaction device 8 in the first embodiment.

The gas compressor 17 compresses the vaporized gas in the space above the liquid level of the liquid fuel L in the buffer tank 5, creating a negative pressure in this space. The vaporized gas compressed by the gas compressor 17 is sent to the condensed water tank 18.

When the lower liquid level sensor 13d detects the liquid level of the liquid fuel L, the gas compressor 17 is activated to reduce the pressure inside the buffer tank 5 and send the liquid fuel L to the buffer tank 5.

Condensed water (liquefied ammonia) is sent from the condensed water tank 18 through the check valve 8a to the mixing tank 11, where it is mixed with the liquid fuel L from the buffer tank 5 and supplied to the ship's engine 12.

In this embodiment, the condensed water condensed by the vacuum device is used in the ship's engine 12, so liquid fuel is used without waste.

Also, in this embodiment, there is no need to provide multiple pumps for each fuel tank 1a, 1b, 1c, and 1d, which simplifies pump maintenance and reduces installation costs. Furthermore, stacking the fuel tanks 1a, 1b, 1c, and 1d one above the other, coupled with the separate pumps, allows for reduced volume. Furthermore, if a siphon is formed from the liquid fuel L stored in each fuel tank 1a, 1b, 1c, and 1d to the end of the extraction pipe in the buffer tank 5, there is no need to reduce the pressure inside the buffer tank 5, which reduces the energy consumption of the negative pressure device.
If each fuel tank 1a, 1b, 1c, and 1d is loaded onto the ship with liquid fuel L stored in advance, the bunkering time can be significantly reduced without relying on the supply flow rate of a bunkering pump or the like.
If the buffer tank 5 is a tank that does not require the liquid to be drawn from above the tank's liquid surface, various types of pumps can be used for the buffer tank 5, such as a diaphragm pump or a canned motor pump.

Fifth Embodiment
5 is a block diagram showing the configuration of a fuel supply system for a marine vessel according to a fifth embodiment of the present invention. The same reference numerals as in FIG. 1 designate the same components, and unless otherwise specified, the description in FIG. 1 is used and will not be repeated here.

In this embodiment, the liquid fuel is liquefied ammonia.

In this embodiment, as shown in Figure 5, a denitration system 19 is provided as a negative pressure device instead of the reliquefaction system 8 in the first embodiment. The denitration system 19 is an exhaust gas denitration system such as a catalytic reduction device.

Vaporized gas in the space above the liquid fuel L level in the buffer tank 5 is sent via pressure reducing valve 9 to the denitration equipment 19, which denitrifies this vaporized gas. The denitration equipment 19 creates a negative pressure in the space above the liquid fuel L level in the buffer tank 5, causing the liquid fuel L to be sent to the buffer tank 5. When the lower liquid level sensor 13d detects the liquid fuel L level, the pressure reducing valve 9 is controlled to open, allowing the vaporized gas in the buffer tank 5 to be denitrified.

In addition, the vaporized gas in the space above the liquid level of the liquid fuel L in the buffer tank 5 may be supplied to a reducing agent production device and stored as a reducing agent.

In this embodiment, the vaporized gas in the buffer tank 5 is used for denitration by the denitration equipment 19, so liquid fuel is used without waste.

Also, in this embodiment, there is no need to provide multiple pumps for each fuel tank 1a, 1b, 1c, and 1d, which simplifies pump maintenance and reduces installation costs. Furthermore, stacking the fuel tanks 1a, 1b, 1c, and 1d one above the other, coupled with the separate pumps, allows for reduced volume. Furthermore, if a siphon is formed from the liquid fuel L stored in each fuel tank 1a, 1b, 1c, and 1d to the end of the extraction pipe in the buffer tank 5, there is no need to reduce the pressure inside the buffer tank 5, which reduces the energy consumption of the negative pressure device.
If each fuel tank 1a, 1b, 1c, and 1d is loaded onto the ship with liquid fuel L stored in advance, the bunkering time can be significantly reduced without relying on the supply flow rate of a bunkering pump or the like.
If the buffer tank 5 is a tank that does not require the liquid to be drawn from above the tank's liquid surface, various types of pumps can be used for the buffer tank 5, such as a diaphragm pump or a canned motor pump.

Sixth Embodiment
6 is a block diagram showing the configuration of a fuel supply system for a marine vessel according to a sixth embodiment of the present invention. The same reference numerals as those in FIGS. 1 and 5 designate the same components, and unless otherwise specified, the explanations in FIGS. 1 and 5 are used and will not be repeated here.

In this embodiment, the liquid fuel is liquefied ammonia.

In this embodiment, as shown in Figure 6, a gas compressor 17 and denitration equipment 19 are provided as negative pressure devices instead of the reliquefaction device 8 in the first embodiment.

The gas compressor 17 compresses the vaporized gas in the space above the liquid level of the liquid fuel L in the buffer tank 5, creating a negative pressure in this space. The vaporized gas compressed by the gas compressor 17 is sent to the denitration equipment 19.

In this embodiment, by providing both a gas compressor 17 and denitration equipment 19 as negative pressure devices, it is possible to efficiently create a negative pressure in the space above the liquid surface of the liquid fuel L in the buffer tank 5.

When the lower liquid level sensor 13d detects the liquid level of the liquid fuel L, the gas compressor 17 is activated, sending vaporized gas to the denitration equipment 19, reducing the pressure inside the buffer tank 5, and sending liquid fuel L to the buffer tank 5.

In this embodiment, the vaporized gas in the space above the liquid level of the liquid fuel L in the buffer tank 5 may also be supplied to a reducing agent production device and stored as a reducing agent.

In this embodiment, the vaporized gas in the buffer tank 5 is used for denitration by the denitration equipment 19, so liquid fuel is used without waste.

Also, in this embodiment, there is no need to provide multiple pumps for each fuel tank 1a, 1b, 1c, and 1d, which simplifies pump maintenance and reduces installation costs. Furthermore, stacking the fuel tanks 1a, 1b, 1c, and 1d one above the other, coupled with the separate pumps, allows for reduced volume. Furthermore, if a siphon is formed from the liquid fuel L stored in each fuel tank 1a, 1b, 1c, and 1d to the end of the extraction pipe in the buffer tank 5, there is no need to reduce the pressure inside the buffer tank 5, which reduces the energy consumption of the negative pressure device.
If each fuel tank 1a, 1b, 1c, and 1d is loaded onto the ship with liquid fuel L stored in advance, the bunkering time can be significantly reduced without relying on the supply flow rate of a bunkering pump or the like.
If the buffer tank 5 is a tank that does not require the liquid to be drawn from above the tank's liquid surface, various types of pumps can be used for the buffer tank 5, such as a diaphragm pump or a canned motor pump.

[First improved embodiment]
7 is a block diagram showing the configuration of a marine fuel supply system according to a first improved embodiment of the present invention. The same reference numerals as in FIG. 1 designate the same components, and unless otherwise specified, the description in FIG. 1 is used and will not be repeated here.

As shown in Figure 7, this improved embodiment adds a gas supply/discharge pipe 20 and a buffer tank pressure reduction pipe 22 to the marine fuel supply device of the first embodiment (Figure 1). Note that it is also possible to add only one of the gas supply/discharge pipe 20 and the buffer tank pressure reduction pipe 22.

The gas supply/discharge pipe 20 and/or the buffer tank decompression pipe 22 can also be added to the marine fuel supply systems of the second to sixth embodiments (FIGS. 2 to 6).
The configurations and functions of the gas supply/discharge pipe 20 and the buffer tank pressure reduction pipe 22 are the same as those of the gas supply/discharge pipe 20 and the buffer tank pressure reduction pipe 22 in this improved embodiment when added to any of the marine fuel supply devices of the second to sixth embodiments (FIGS. 2 to 6), and therefore will not be described here.

[Gas supply and exhaust pipe 20]
The gas supply and discharge pipe 20 is a pipe connected to outside equipment, which branches off at the fuel tanks 1a, 1b, 1c, and 1d sides and is connected to the fuel tanks 1a, 1b, 1c, and 1d.
At the branched portions of the gas supply/discharge pipe 20, on-off valves 21a, 21b, 21c, and 21d are provided corresponding to the fuel tanks 1a, 1b, 1c, and 1d, respectively.

Here, the off-board equipment includes not only the bunkering equipment 100 but also gas treatment equipment on the bunker ship (not shown) and gas treatment equipment on land.
The gas supply and discharge pipe 20 is a pipe for supplying or discharging gas between outside equipment and each fuel tank 1a, 1b, 1c, and 1d, and is therefore preferably connected to a location that will be the gas phase if liquid is present in each fuel tank 1a, 1b, 1c, and 1d.

By providing the gas supply and discharge pipes 20, preparations can be made before new liquid fuel L is poured into each fuel tank 1a, 1b, 1c, and 1d. It is also possible to make preparations before inspecting the inside of each fuel tank 1a, 1b, 1c, and 1d.

Common operations for these two preparations include gasifying (gas vaporizing) the liquid fuel L remaining in each of the fuel tanks 1a, 1b, 1c, and 1d, and rendering the gas harmless.
Preparations before adding new liquid fuel L include gasifying the liquid fuel L remaining in each fuel tank 1a, 1b, 1c, and 1d (Gas Vaporizing), removing moisture (Drying), supplying inert gas (Innerting), removing impurities (Gassing up), and pre-cooling (Cool down).
Preparations before inspections include gasifying the liquid fuel L remaining in each of the fuel tanks 1a, 1b, 1c, and 1d (gas vaporizing) and increasing the oxygen concentration (aeration).

(Operations common to both preparation operations)
The preparation operation for each of the fuel tanks 1a, 1b, 1c, and 1d using the gas supply and discharge pipe 20 is carried out when the liquid fuel L in each of the fuel tanks 1a, 1b, 1c, and 1d has been completely used up.

Even if all the liquid fuel L is used up, the liquid fuel L or gas evaporated from the liquid fuel L may remain in each fuel tank 1a, 1b, 1c, 1d, so if any liquid fuel L remains, it is gasified.
The remaining liquid fuel L is gasified by opening the on-off valves 21a, 21b, 21c, and 21d, and heating the liquid fuel L remaining in each of the fuel tanks 1a, 1b, 1c, and 1d, or by supplying heated gas or applying pressure (gas vaporizing). At this time, the inside of each of the fuel tanks 1a, 1b, 1c, and 1d is heated.
If the remaining gas resulting from gasification of the remaining liquid fuel L and/or the remaining gas cannot be released into the atmosphere, it is necessary to supply it to an on-board facility, an off-board facility such as a bunker ship, or a gas treatment facility on land for detoxification treatment. Since the gas treatment facility on land can have a larger treatment capacity than the on-board gas treatment facility 14, it is preferable to use the gas supply and discharge pipe 20 to send the remaining gas to the on-shore gas treatment facility for treatment.

(Preparation before adding new liquid fuel L)
Preparations before filling each fuel tank 1a, 1b, 1c, and 1d with new liquid fuel L are made as follows: first, in order to prevent condensation in each fuel tank 1a, 1b, 1c, and 1d, open the on-off valves 21a, 21b, 21c, and 21d, and supply dry air to each fuel tank 1a, 1b, 1c, and 1d using the gas supply and discharge pipe 20, thereby removing moisture from each fuel tank 1a, 1b, 1c, and 1d (drying).

Next, an inert gas is supplied to each of the fuel tanks 1a, 1b, 1c, and 1d using the gas supply and discharge pipes 20 (Innerting).
If the gas volatilizing from the newly supplied liquid fuel L is a flammable gas, there is a possibility of explosion if the oxygen concentration is high, so the oxygen concentration in each fuel tank 1a, 1b, 1c, and 1d can be lowered to below the lower explosion limit.
Furthermore, if the gas volatilizing from the newly supplied liquid fuel L is a toxic gas (e.g., _NH3 ), a high oxygen concentration may cause stress corrosion cracking depending on the material of each fuel tank 1a, 1b, 1c, and 1d, so the oxygen concentration can be lowered.
Furthermore, if gas volatilized from the liquid fuel L remains in each of the fuel tanks 1a, 1b, 1c, and 1d, the supply of inert gas also removes this remaining gas.

Next, the inert gas in each fuel tank 1a, 1b, 1c, and 1d is replaced with gas volatilized from the liquid fuel L using the gas supply and exhaust pipe 20, thereby removing impurities from each fuel tank 1a, 1b, 1c, and 1d (gassing up).

Furthermore, if the liquid fuel L is a fuel that requires cooling, the inside of each fuel tank 1a, 1b, 1c, and 1d must be pre-cooled. Therefore, gas that has been evaporated and cooled from the liquid fuel L is supplied to pre-cool (cool down) the inside of each fuel tank 1a, 1b, 1c, and 1d.

Then, the on-off valves 21a, 21b, 21c, and 21d are closed, and liquid fuel L is supplied from the bunkering equipment 100 to each fuel tank 1a, 1b, 1c, and 1d via the supply pipe 2 (Loading).

Incidentally, one method for adjusting the temperature of each fuel tank 1a, 1b, 1c, 1d is to spray liquefied gas such as liquid fuel L. However, when the flow rate of the liquid fuel L supplied through the supply pipe 2 is large (for example, 700 m ³ /h), the amount of heat absorbed by the liquid fuel L becomes excessively large, and the flow rate must be small (10 m ³ /h), making it difficult to uniformly adjust the temperature of each fuel tank 1a, 1b, 1c, 1d. Therefore, it is easier to adjust the temperature of each fuel tank 1a, 1b, 1c, 1d by supplying cooled gas from an onshore facility.

Gas may be supplied from the bunkering facility 100 through the supply pipe 2, and pressure may be released through the gas supply and discharge pipe 20.

(Preparation before inspection, etc.)
Preparations before inspecting each of the fuel tanks 1a, 1b, 1c, and 1d are made by first opening the on-off valves 21a, 21b, 21c, and 21d and supplying dry air into each of the fuel tanks 1a, 1b, 1c, and 1d using the gas supply and discharge pipes 20. This is to increase the oxygen concentration (aeration) so that workers can enter each of the fuel tanks 1a, 1b, 1c, and 1d. If the oxygen concentration in each of the fuel tanks 1a, 1b, 1c, and 1d is low, workers will not be able to enter.
Furthermore, if gas volatilized from the liquid fuel L remains in each of the fuel tanks 1a, 1b, 1c, and 1d, the supply of dry air also removes this remaining gas.

Then, the on-off valves 21a, 21b, 21c, and 21d are closed, and inspections of the inside of each fuel tank 1a, 1b, 1c, and 1d are carried out.

[Buffer tank decompression pipe 22]
The buffer tank decompression pipe 22 is a pipe that connects a location downstream of the flow rate control valve 7 at the junction of the withdrawal pipes 4a, 4b, 4c, and 4d with a location upstream of the flow rate control valve 7. A pressure reducing valve 23 is provided midway along the buffer tank decompression pipe 22.

By providing the buffer tank decompression pipe 22, the buffer tank 5 can be emptied in preparation for inspection of the buffer tank 5 and the pump 10, for example.
If there is any residual gas in the buffer tank 5, this residual gas passes through the buffer tank pressure reducing pipe 22, the pressure reducing valve 23, and the junction of the extraction pipes 4a, 4b, 4c, and 4d (upstream of the flow control valve 7), and is sent to the gas treatment device 14, where it is detoxified.
Since the gas treatment device 14 has a flow rate restriction, the pressure reducing valve 23 adjusts the gas flow rate through the buffer tank pressure reducing pipe 22 to match the flow rate restriction of the gas treatment device 14 .

It is possible to consider making the flow control valve 7 a two-way valve and using it also as a pressure reducing valve to empty the buffer tank 5, but since the flow control valve 7 is a valve for liquids and cannot adjust the gas flow rate, there is great significance in providing a separate pressure reducing valve 23 for gases.

The pressure reducing valve 23 may be installed inside the gas treatment device 14. In this case, the evaporation rate will be greater than the treatment rate, resulting in high pressure, so it is preferable to increase the design pressure of each device and piping.

The remaining gas can be sent from the buffer tank 5 to the gas processing device 14 by the suction force of a suction device such as a compressor optionally provided in the gas processing device 14 .
Alternatively, the remaining gas can be sent from the buffer tank 5 to the gas processing device 14 by providing a separate dedicated line from a gas supply device (not shown) and pumping the gas into the buffer tank 5.
From the viewpoint of ensuring safety, it is preferable that the gas pressure-fed into the buffer tank 5 be an inert gas.

Furthermore, the buffer tank decompression pipe 22 can also be used as an exhaust pipe when purging and ventilating with an inert gas to ensure safety when opening the buffer tank 5. This inert gas is, for example, _N2 gas or oxygen-depleted air.
In this case, the inert gas for purging and ventilation can be supplied to the buffer tank 5 by pressure from an inert gas supply device (not shown) through a separate dedicated line.
In addition, this inert gas may be supplied from the inert gas supply device into the buffer tank 5 and discharged from the buffer tank 5 by the suction force of a suction device such as a compressor optionally provided in the gas processing device 14, rather than by pressure feeding.

Although each embodiment has been described above, the present invention is not limited to these embodiments, and various improvements and design changes may be made, and each embodiment may be combined with another, without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1a Fuel tank 1b Fuel tank 1c Fuel tank 1d Fuel tank 2 Supply pipe 3a On-off valve 3b On-off valve 3c On-off valve 3d On-off valve 4a Withdrawal pipe 4b Withdrawal pipe 4c Withdrawal pipe 4d Withdrawal pipe 5 Buffer tank 6a On-off valve 6b On-off valve 6c On-off valve 6d On-off valve 7 Flow rate control valve 8 Reliquefaction device 8a Check valve 9 Pressure reducing valve 10 Pump 11 Mixing tank 12 Ship's engine 13u Upper liquid level sensor 13d Lower liquid level sensor 14 Gas treatment device 15a On-off valve 15b On-off valve 15c On-off valve 15d On-off valve 16 Return pipe 17 Gas compressor 18 Condensed water tank 19 Denitrification equipment 20 Gas supply and discharge pipe 21a On-off valve 21b On-off valve 21c On-off valve 21d On-off valve 22 Buffer tank pressure reducing pipe 23 Pressure reducing valve 100 Bunkering equipment L Liquid fuel

Claims (9)

A fuel supply device for a ship that supplies liquid fuel stored in a plurality of fuel tanks to an engine of the ship,
a plurality of extraction pipes for extracting the liquid fuel from each of the fuel tanks, the extraction pipes being located above the liquid level of the liquid fuel stored in each of the fuel tanks;
a buffer tank to which the liquid fuel is delivered via the plurality of extraction pipes;
a pump that supplies the liquid fuel in the buffer tank to an engine of the ship;
a negative pressure generating device that generates a negative pressure in a space above the liquid fuel level in the buffer tank and sucks out the liquid fuel from each of the fuel tanks ,
a buffer tank pressure reduction pipe that connects a location downstream of a flow rate adjustment valve provided in the extraction pipe leading to the buffer tank with a location upstream of the flow rate adjustment valve and that has a pressure reduction valve provided midway;
A fuel supply device for a ship. 2. The fuel supply system for a marine vessel according to claim 1, wherein the buffer tank is a tank that does not require the liquid to be drawn from above the liquid level of the tank. a liquid level of the liquid fuel in the buffer tank is lower than a liquid level of the liquid fuel stored in each of the fuel tanks;
2. The fuel supply device for a marine vessel according to claim 1, wherein a siphon is formed from the liquid fuel stored in each of the fuel tanks through each of the withdrawal pipes to an end of the withdrawal pipe in the buffer tank. 2. The fuel supply system for a marine vessel according to claim 1, wherein the negative pressure generating device is a re-liquefaction device. 2. The fuel supply system for a boat according to claim 1, wherein the negative pressure generating device is a gas compressor. 2. The fuel supply system for a marine vessel according to claim 1, wherein the negative pressure generating device is a denitration facility. 2. The fuel supply system for a marine vessel according to claim 1, wherein at least two of the fuel tanks are stacked one above the other. 8. The marine vessel fuel supply device according to claim 1, wherein the plurality of fuel tanks are loaded onto the marine vessel and connected to the extraction pipes while storing the liquid fuel, and are detached from the extraction pipes and lowered from the marine vessel when the liquid fuel is consumed and the stored amount is reduced. 8. The fuel supply system for a marine vessel according to claim 1, further comprising gas supply and discharge pipes connecting each of the fuel tanks to an outside facility.