KR102610000B1 - Apparatus and method for supplying fuel to a power generation unit - Google Patents

Abstract

Apparatus and method for supplying fuel to a power generation unit
Device (10, 110, 210) and method for supplying liquid fuel, in particular to a power generation unit (12) installed on a ship (14), comprising: a main tank (16) of liquefied gas, at least a first surge tank (16) of liquefied gas; 18), a first duct 32 for transporting liquefied gas from the first surge tank 18 to the power generation unit 12, the first end of the first duct for supplying liquid fuel to the power generation unit (32a) leads to the first surge tank (18) and the second end (32b) of the first duct is connected to the power generation unit (12), and the liquefied gas is supplied to the main tank ( 16) to the first surge tank 18, and the second duct 22 is configured to be submerged in the liquefied gas 24 contained in the main tank 16. comprising a first end (22a) and a second end (22b) leading to the first surge tank (18) for supplying liquefied gas to the first surge tank, and wherein the apparatus and method have a pressure lower than atmospheric pressure. means (20, 36) for depressurizing the first surge tank (18) with respect to the main tank (16), comprising at least one compressor (20) configured to apply an operating pressure to the first surge tank; It is characterized by having

Description

Apparatus and method for supplying fuel to a power generation unit

The present invention relates in particular to an apparatus and method for supplying fuel to a power generation unit installed on a ship.

The prior art includes, say, documents WO-A1-2012/089891 and WO-A1-2015/183966.

To facilitate transporting gases, such as natural gas, over long distances, the gas is usually liquefied by cooling it at atmospheric pressure to a cryogenic temperature, e.g. -163°C (e.g. liquefied natural gas - becomes LNG). The liquefied gas is then loaded onto a special vessel.

For example, on ships carrying liquefied gases of the LNG carrier-type, power generation units are installed to meet the operating energy needs of the ship, in particular to generate electricity for the ship's propulsion and onboard equipment.

These devices usually include a thermal machine using gas supplied by an evaporator; The gas is obtained from liquefied gas transported as cargo in one or multiple tanks of the ship.

Document FR-A-2 837 783 discloses a method of providing an evaporator and/or other system providing propulsion power using a pump submerged in the bottom of one of the ships tanks.

There are several disadvantages to locating the pump in this way. According to ICAS (International Association of Classification Societies ) rules, pump inspection work requires regular inspections and may require the main tanks to be opened, which requires the vessel to be secured and may damage the tanks. There is a risk.

One solution to this problem is to include an opening in the bottom of the tank, through which the liquefied gas is discharged from the tank. However, the IGF rules and the IGC rules ( International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk ) stipulate that the above-mentioned large tank, in the case of the main tank of the ship, must be used. Opening is prohibited.

The present invention proposes to perfect the current technology in a simple, effective and cost-effective manner.

The invention relates in particular to a device and method for supplying liquid fuel to a power generation unit installed on a ship, comprising:

- main tank of liquefied gas,

- at least a first liquefied gas surge tank,

- Transferring liquefied gas from a first surge tank to the power generation unit, the first end being open to the first surge tank and the second end connected to the power generation unit for supplying liquid fuel to the power generation unit. The first duct has,

- transporting liquefied gas from a main tank to a first surge tank, comprising: a first end configured to be immersed in the liquefied gas contained in the main tank; a second duct comprising a second end that continues, and

- Liquid is sucked from the first surge tank so that the liquefied gas coming out of the main tank is transported by the second duct and supplied to the first surge tank to create an operating pressure lower than the pressure of the main tank. means for depressurizing the first surge tank relative to the main tank, configured to act on the tank;

Characterized in that the pressure reducing means includes at least one compressor and the operating pressure is lower than atmospheric pressure.

The device according to the invention overcomes the problems associated with the prior art. A pump submerged within the main tank is not essential for transferring liquefied gas from the main tank to the surge tank. Depressurization in the surge tank, that is, a pressure difference between the surge tank and the main tank, causes the liquefied gas contained in the main tank to be supplied to the surge tank. This causes the liquefied gas to circulate in the second duct from the main tank towards the surge tank. Typically, the BOG contained in the main tank can be used to supply a power generation unit installed on the ship. In this case, the device is used to add liquid to the BOG source, in the form of liquid or gas, which is available in the surge tank and can be conveyed to the power generation unit by a first duct.

The first surge tank is configured to be depressurized to a pressure lower than atmospheric pressure (eg, a pressure of -600 mbarg to -100 mbarg, even a pressure of -600 mbarg to -200 mbarg). Even when the surge tank is under a pressure close to atmospheric pressure, for example -100 mbarg to 100 mbarg, or -100 mbarg to 250 mbarg, or -100 mbarg to 400 mbarg, liquefied gas can be supplied from the main tank to the surge tank. For transfer to a tank, the compressor is configured to achieve this reduced pressure.

This allows the liquefied gas to be supplied immediately to a power generation unit comprising, for example, an engine, whereas according to the current state of the art, the pressure inside the main tank is at a level sufficient to supply the gas to the engine. You need to wait for it to reach. In this case, it should be noted that the pressure should be at a level suitable for the engine, for example above 6 barg, and that the tank, especially the type of tank, can be selected based on the tank's resistance to pressure.

According to the invention, the device comprises one or several of the following features, individually or in combination:

- the main tank is a membrane tank, that is, the walls of the main tank, in particular the side walls of the main tank, contain at least one metal layer forming a sealing membrane and at least one layer of insulation. Contains;

- the main tank is configured to withstand a pressure of not more than 3000 mbarg, preferably not more than 750 mbarg;

- the main tank is not a membrane tank;

- the main tank is configured to withstand a pressure of at least 3000 mbarg, preferably at least 6000 mbarg;

- the pressure reducing means comprises an outlet adapted to be connected to the power generation unit;

- the pressure reducing means comprises at least one compressor;

- a pump is connected to the first duct and is configured to suck liquefied gas from the first surge tank;

- the compressor is connected to a third pressure reduction duct of the first surge tank, the first end of the third pressure reduction duct is connected to the first surge tank, and the second end of the third pressure reduction duct is connected to the compressor. It is connected to the inlet, and the third duct is configured to suck boil-off gas from the first surge tank and supply the boil-off gas to the compressor.

- for supplying fuel gas to the power generation unit, the compressor comprises an outlet connected to the power generation unit;

- the second end of the third duct is connected to the compressor by a first heat exchange circuit;

- the device comprises a fourth duct conveying gas from the main tank to the compressor;

- the fourth duct comprises a first end connected to the main tank and a second end connected to the compressor;

- the second end of the fourth duct, together with the second duct, is connected to the inlet of the first heat exchange circuit, and one outlet of the first heat exchange circuit is connected to the compressor;

- the first end of the second duct does not contain a pump;

- the first duct contains at least one pump and/or one pressure reducing valve and/or one heat exchanger; To supply fuel gas to the power generation unit, the heat exchanger may be configured to vaporize liquefied gas circulating in the first duct;

- the pump is configured to be controlled based on the fuel gas demand of the power generation unit;

- the device comprises a fifth liquid return duct from the pressure reducing means to the main tank, a first end of the fifth liquid return duct being connected to an outlet of the pressure reducing means, and a second The end is connected to the main tank;

- the device comprises a second liquefied gas surge tank;

- 2nd surge tank

■ the first duct including a third end connected to the second surge tank, and

■ connected to the second duct including a third end connected to the second surge tank;

- the second surge tank is connected to the third duct comprising a third end connected to the second surge tank;

- the device comprises a fifth duct supplying gas to the first surge tank and the second surge tank, the first end of the fifth duct being connected to the outlet of the pressure reducing means and the second end being connected to the outlet of the pressure reducing means. connected to the first surge tank, and a third end connected to the second surge tank, such that the fifth duct supplies compressed gas to the first surge tank and/or the second surge tank. Consists of;

- the first duct is connected by a sixth duct to a liquefied gas atomizer boom in the main tank, wherein the boom sprays the liquefied gas into the main tank in the form of droplets, in order to condense at least a part of the boil-off gas in the main tank. It is configured to spray the boil-off gases in the tank;

- each of the tanks is equipped with a pressure sensor and/or a level sensor;

- the surge tank or each surge tank is arranged below the upper part of the main tank;

- the surge tank or each surge tank is arranged outside the main tank;

The or each surge tank may be used for expansion and/or isolation purposes; At least a portion of the liquefied gas supplied to the surge tank may undergo partial vaporization and phase separation within the tank; Less than half or less than 10% of the inhaled liquefied gas may be vaporized in this way; The gas outlet, in gaseous and liquid state, can be connected to the power generation unit without going through the main tank; A small portion (1% to 10%) of the extracted LNG is evaporated upstream from the compressor so that a reduced flow compressor can be used; A smaller amount of gas needs to be inhaled (for a given demand of a power generation unit of gaseous LNG) than when the gas is inhaled (the gas volume is approximately 600 times larger than the liquid volume);

- the liquefied gas contains at least one pure gas or substance; For example:

- the first duct transports at least a part of this pure gas (in liquid state and possibly in combination with other gases) from the surge tank to the power generation unit, and/or

- the compressor draws in at least a portion of the pure gas (perhaps in combination with other gases), and/or

- The compressor supplies pure gas (perhaps in combination with other gases) to the power generation unit.

In this application, the expression “pure” is used to refer to a single chemical substance or chemical species, rather than a combination of several chemicals or chemical species. For example, a pure gas is either a light gas or a heavy gas.

In this application, the expressions heavier and lighter refer to a high-density gas or gas with a high molar mass and a low-density gas or gas with a low molar mass, respectively. In liquefied gas, the light gas is usually methane. Liquefied gas may contain some nitrogen as part of its lighter parts. In the case of liquefied natural gas, small amounts of the heavier fraction include propane, butane and ethane (which evaporate at higher temperatures or lower pressures). In liquefied gas, the heavy portion corresponds to 5.2% to 49.8% of the total mass of the liquefied gas. Heavy gases are characterized by having a molar mass that is 25% to 500% higher than that of light gases.

The present invention relates to ships equipped with at least one device of the above-described type, particularly to ships used to transport liquefied gases. The invention relates in particular to LNG-powered ships (as is common in liquefied gas carriers, in which case it is believed that propulsion tanks are also used for transport purposes).

The invention also relates to a method for supplying fuel to a power generation unit, especially installed on a ship, using a device of the type described above, comprising:

- Step A of filling the first surge tank by depressurizing the first surge tank with respect to the main tank, so that liquefied gas is transferred from the main tank to the first surge tank;

It is characterized by including.

According to the present invention, the method may include one or several of the following features individually or in combination:

- the method comprises a step B1 in which the power generation unit is fueled by the compressor by gas intake from the first surge tank;

- During step B1, the power generation unit is fueled by the compressor by gas extraction from the main tank and the surge tank;

- the method comprises step B2, wherein the compressor supplies gas from the first surge tank and/or the second surge tank to the power generation unit, thereby circulating the liquefied gas in the first duct;

- During step B1 or step B2, using the compressor, the second surge tank is depressurized with respect to the main tank so that the liquefied gas is transferred from the main tank to the second surge tank, thereby causing the second surge tank to deliver liquefied gas. be supplied;

- During stage A, the pressure inside the main tank is controlled by regulating the gas flow circulating in the fourth duct and/or the fifth duct;

- During or after stage A, the pump in the first duct is supplied with liquefied gas from the first surge tank;

- the method comprises a step B3 in which the power generation unit is supplied with fuel by the first duct using the pump;

- During stage A, decompression is maintained continuously for a predetermined period of time;

- a pressure difference between the surge tank and the main tank, in the second duct, which is greater than the hydrostatic pressure generated by the generally straight vertical height of the second duct, excluding load losses, if any. Decompression is achieved by imparting;

- the pump is controlled based on the fuel gas demand of the power generation unit;

- at least some of the valves included in one or several of the ducts are controlled based on the fuel gas demand of the power generation unit;

- When the level of liquefied gas inside the surge tank falls below a given critical level, the pressure difference between the surge tank and the main tank increases, in order to increase the supply flow of liquefied gas to the surge tank;

- the pressure difference between one of the surge tanks and the main tank is adjusted based on the filling speed of the other surge tank with liquefied gas coming from the main tank;

- The liquefied gas contained in the first surge tank is transported to the sprayer boom by the first duct and the sixth duct.

By reference to the following description, which is given by way of non-limiting example, and to the accompanying drawings, the invention will be better understood and other details, features and advantages of the invention will become more apparent.
- Figure 1 is a schematic diagram of a first embodiment of a device according to the invention, installed on a ship,
- Figures 2 to 6 are schematic diagrams of Figure 1 showing the steps of the method according to the invention,
- Figure 7 is a schematic diagram of a second embodiment of the device according to the invention, installed on a ship,
- Figures 8 to 12 are schematic diagrams relative to Figure 7 showing the steps of the method according to the invention, and
- Figure 13 is a schematic diagram of a third embodiment of the device according to the invention, installed on a ship.

In the description below, the terms "upstream" and "downstream" relate to the flow of a fluid, such as a gas or liquid, in a duct or circuit.

Figure 1 shows a first embodiment device 10 according to the invention, which can be considered to be configured to supply fuel gas to a ship, such as a liquefied gas carrier. The device 10 can therefore be used to supply fuel gas to a power generation unit 12 installed on a ship 14 .

The vessel 14 contains one tank 16 or several similar tanks 16 used to store liquefied gas. The gas is, for example, methane or a mixture of various gases containing methane. Tank 16 or each tank 16 may contain gas in a liquid state at a predetermined pressure and temperature, for example at atmospheric pressure and a temperature of -163°C. One or several tanks 16 of the vessel can be connected to the power generation unit 12 by means of the device 10 according to the invention. The number of tanks is not limited. For example, the number of tanks may be 1 to 6. Each tank 16 can have a holding volume of between 1'000 (even 100) m ³ and 50'000 m ³ .

Hereinafter, the term “tank 16” should be understood as “tank or each tank 16”.

The tank 16 accommodates the liquefied gas 16aa and the gas 16ab generated by natural evaporation of the liquefied gas 16aa inside the tank 16. Naturally, the liquefied gas 16aa is stored at the bottom of the tank 16, while the boil-off gas 16ab exists above the level of the liquefied gas inside the tank, schematically represented by the letter N.

Hereinafter, “LNG” refers to liquefied gas, that is, gas in a liquid state, “BOG” refers to vapor gas or boil-off gas, “NBOG” refers to natural boil-off gas, and “FBOG” refers to forced boil-off gas. represents (forced boil-off gas); These abbreviations are known to those skilled in the art because they reflect English terminology commonly used in the art.

In the embodiment shown in Figure 1, one end 22a of duct 22 is submerged in LNG 16aa in tank 16. Preferably, this end does not contain a pump, so that there is no need for maintenance of the pump and to ensure that the duct is supplied only with LNG, even when the tank is almost empty, preferably at the bottom of the tank. It is placed in

In this application, the term "bottom" of a tank or vat is used to indicate a location less than one meter from the bottom wall of the tank, which is closest to the center of the Earth during operation.

Duct 22 contains a bypass and has two ends disposed outside of tank 16. One of these ends 22d forms the LNG filling port of the tank 16 and is therefore available to the user, especially when LNG is loaded into the ship's tank 16.

The other end 22b of the duct is connected to a surge tank 18 disposed outside the tank 16. Valves (23d, 23b) are coupled to the ends (22d, 22b), respectively. The valve 23d is configured to stop the circulation of the fluid inside the duct 22 and, consequently, to stop the supply of LNG to the tank 16. The valve 23d may form a check valve. The valve 23b is configured to stop the supply of fluid to the surge tank 18, especially during bunkering of the main tank 16.

An LNG droplet atomizer boom 52 is disposed in the upper part of the tank 16 above height N. The LNG droplet sprayer boom 52 is configured to spray LNG droplets into the BOG of the tank. This is used to re-condense the BOG in tank 16.

Tank 16 also includes a BOG inlet 16a and a BOG outlet 16b. The BOG outlet 16b is connected to one end 30a of a duct 30 containing a side pipe defining two ends disposed outside the tank 16. One of these ends 30c forms the BOG evacuation port of the tank 16 and is therefore available to the user, especially when LNG is loaded into the ship's tank 16.

The other end 30b of the duct 30 is connected to the inlet 28aa of the first circuit 28a of the heat exchanger 28 and the outlet 28ab of the first circuit 28a of the heat exchanger 28. is connected to the inlet 20a of the compressor 20. Since the first circuit 28a is a cold circuit, the fluid circulating in the first circuit 28a circulates in the second circuit 28b, known as the hot circuit of the heat exchanger 28. It is designed to be heated by fluid.

The valves 31a and 31c are respectively coupled to the ends 30a and 30c. The valve 31a is configured to stop the circulation of fluid within the duct 30 and, consequently, to stop the discharge of LNG from the tank 16. The valve 31a may form a check valve. Valve 31c may be used to stop discharge of the BOG to end 30c and associated orifice.

The inlet 16a of the tank 16 is connected to one end 38b of the duct 38, and the other end 38a of the duct 38 is connected to the outlet 20b of the compressor 20. A valve 39 is connected to the duct 38 and blocks circulation of fluid from the outlet of the compressor 20 to the tank 16. The outlet 20b of the compressor 20 is also connected to the power generation unit 12 by a valve 41 .

Surge tank 18 includes three openings, one inlet 18a connected to end 22b of duct 22 and two outlets 18b, 18c. The inlet 18a is configured to receive LNG, and the surge tank 18 is configured to receive LNG directly from the tank 16.

Outlet 18b is a gas outlet, especially a BOG outlet, and outlet 18c is an LNG outlet. The outlet 18b is connected to one end 26a of the duct 26, and the opposite end 26b of the duct 26 is connected to the inlet 20a of the compressor 20. In the example shown, BOG from surge tank 18 is heated by heat exchanger 28 before being supplied to compressor 20. For this purpose, the duct 26 is connected to the duct 30 upstream from the heat exchanger 28, more particularly upstream from the first circuit 28a of the heat exchanger 28, so that the tank ( 16) and the BOG from the surge tank 18 can be supplied to the heat exchanger 28 and heated before being supplied to the compressor 20.

The duct 26 includes a valve 27 configured to block the circulation of fluid within the duct 26, in particular to block the discharge of BOG from the surge tank 18 to the heat exchanger 28.

The outlet 18c is connected to the end 32a of the duct 32, and the end 32a of the duct 32 is connected to the power generation unit 12 together with the outlet 20b of the compressor 20. This duct 32 contains the pump 36 and the heat exchanger 34 or is connected to the pump 36 and the heat exchanger 34. The duct 32 also includes two valves 33a, 33b, one of which is, for example, a pressure reducing valve 33b. In the example shown, from upstream to downstream, that is, from the surge tank 18 to the outlet 20b of the compressor 20, the pump 36, valve 33b, heat exchanger 34 and valve 33a are connected. are arranged.

Duct 32 is connected to the outlet 20b of compressor 20 immediately upstream from valve 41. Additionally, at the outlet of valve 33a, duct 32 is connected to duct 38 immediately downstream from valve 39 by valve 33c.

In the example shown, LNG discharged from surge tank 18 by pump 36 is vaporized by heat exchanger 34 before being supplied to power generation unit 12. For this purpose, a duct 32 is connected to the inlet 34aa of the first circuit 34a of the heat exchanger 34 and the outlet 34ab of the first circuit 34a of the heat exchanger 34. It is connected to the valve (33a). Since the first circuit 34a is a low-temperature circuit, the fluid circulating in the first circuit 34a is heated by the fluid circulating in the second circuit 34b, known as the high-temperature circuit of the heat exchanger 34.

If valve 33b is a pressure reducing valve configured to vaporize all of the LNG into FBOG, the FBOG is heated by heat exchanger 34 before being supplied to power generation unit 12. Therefore, preferably, the valve 33b is configured such that the pressure of the FBOG at the outlet is equal to the operating pressure of the fuel gas in the power generation unit 12.

A duct 50 with a valve 51 connects the LNG droplet atomizer boom 52 to the duct 32. The upstream end of the duct is connected to the duct 32 between the pump 36 and the valve 33b, i.e. immediately downstream from the pump 36, and the downstream end of the duct is connected to the LNG droplet atomizer boom. It is connected to (52). Accordingly, as noted above, it should be noted that LNG contained within surge tank 18 may be supplied to LNG droplet atomizer boom 52.

Therefore, the surge tank 18 is configured to receive LNG from the tank 16. The operating pressure inside the surge tank 18 is lower than the storage pressure of LNG inside the tank 16. Supplying LNG to the surge tank 18 can cause partial evaporation of the LNG, which causes generation of FBOG inside the surge tank 24 and cooling of the LNG remaining in the surge tank 24, LNG cooled in this way is called “supercooled liquefied gas.” The surge tank 18 receives gas in a liquid state at a predetermined temperature and pressure.

The surge tank 18 accommodates the supercooled liquefied gas 18aa as well as the gas 18ab generated by forced evaporation of the liquefied gas 16aa coming from the tank 16. Naturally, the subcooled liquefied gas 18aa (or LNG) is stored at the bottom of the surge tank 18, while the boil-off gas 18ab (or FBOG) is stored in the surge tank 18, schematically represented by the letter L. ) exists above the level of the liquefied gas inside.

In this case, the compressor 20 is used to apply operating pressure inside the surge tank 18. Accordingly, the compressor is configured to depressurize the surge tank 18 with respect to the tank 16. The pressure difference between surge tank 18 and tank 16 may be sufficient to circulate LNG from tank 16 to surge tank 18. It should be noted that in this case the submerged pump at end 22a of duct 22 is not required. The conditions imposed on the surge tank 18 by the compressor 20 are determined to generate LNG in the surge tank 18.

As another form or additional feature, pump 36 may be configured to depressurize surge tank 18 with respect to main tank 16.

When the amount of LNG in the surge tank 18 is very significant and is about to reach a critical level, LNG droplets from the LNG outlet of the surge tank 18 into the power generation unit 12 and/or the main tank 16. It can be transported to the spray boom 52.

The LNG generates cooling power, which can be stored in the surge tank 18 when it is not needed, for example during phases when the amount of NBOG generated is insufficient to meet the demand. .

In the example shown, the pressure relief in surge tank 18 should be sufficient to allow LNG to circulate in duct 22. The duct 22 comprises a vertical portion forming a plunger and submerged in the LNG of the main tank 16, the upper end of which is connected to the remainder of the duct 22 by a T-shaped connection. The pressure difference between the two tanks 16, 18 is preferably equal to the height of the duct 22 (specifically, a T-shape from the bottom of the main tank), excluding the load loss in the duct 22. The height of the vertical part of the duct 22 up to the connection must be greater than the hydrostatic pressure generated by the main tank 16 (when the main tank 16 is empty, the LNG must rise to this height). In another version, the surge tank 18 (more specifically the outlet 22b) is lower than this height and the duct is full (e.g., lower than when the main tank 16 is almost full). (by a small pressure difference) the pressure difference should become smaller.

The pressure difference can be adjusted in the following manner:

- the gas demand of the power generation unit 12 controls the pump 36 (the gas demand is, for example, the gas flow rate measured between the outlet 32b and the power generation unit 12 and the demand of the power generation unit 12 determined by the difference between),

- the surge tank 18 includes a level sensor; When the liquid level in tank 18 falls below the lowest critical level, the pressure difference increases to increase the flow rate in surge tank 18 (similarly, the maximum critical level is such that, once the level is reached, the pressure difference is reduced or eliminated). can be configured to have).

The fuel gas supply device has two main purposes:

- Fuel gas is supplied to the main tank (e.g. 50 kg/h to 2000 kg/h) at a given pressure (e.g. 6 bar to 300 bar) and a given temperature (e.g. 20° C.) at the required flow rate (e.g. 50 kg/h to 2000 kg/h) 16) supply to the ship's power generation unit; The fuel gas may be in a gaseous state (vapor) or a liquid state;

- regulating the pressure inside the main tank 16 and maintaining this pressure within an acceptable range (eg -100 mbarg to +700 mbarg or -700 mbarg to 6000 mbarg);

contribute to

The illustrated device 10 can be used, for example, for the application of cryogenic liquids at atmospheric pressure (e.g. volumes of 1000 (even 100) m ³ to 10000 m ³ and -100 mbarg to +700 mbarg or -700 mbarg to 6000 mbarg. a main tank 16 designed to receive a cryogenic fluid (e.g., having a volume of 1 m ³ to 20 m ³ and an applied pressure of -500 mbarg to 6000 mbarg) and a surge tank ( 18) is included. In order to transfer fluid from the main tank 16 to the surge tank 18, a pressure difference (e.g. , +500 mbarg) is generated in the main tank for the surge tank. The fluid in the surge tank 18 is compressed by the pump 36 and sent to the power generation unit 12 by the vaporization valve 33b. The level of fluid in surge tank 18 is adjusted by a suitable mechanism, for example between 10% and 90% of the internal volume of the surge tank. In this way, the pump 36 is always supplied with 100% liquid gas (mixtures of liquid and gaseous gases can damage the pump). The controls and appropriate mechanisms of the device are designed to maintain the internal pressure of the main tank 16 at the required level (eg -100 mbarg to 700 mbarg). Each tank of the device 10 is therefore preferably equipped with a pressure sensor and/or a level sensor.

Figures 2 to 6 show the operating stages of the device of Figure 1, which correspond to different speed levels of the vessel equipped with this device.

The supply phase is described herein in three stages:

1. Minimum consumption stage: natural evaporation meets the power demand of the unit (the ship's propulsion engines are stopped or operating at low load and gas is mainly used to meet heating and electricity needs).

2. Normal consumption stage: Natural evaporation does not guarantee the ship's power needs.

3. Zero consumption phase (except the gas compressor, all onboard gas consumers of the power generation unit 12 are shut down).

4. Filling step.

1. Minimum consumption stage (see Figure 2)

In the operational phase shown in Figure 2, the ship's main engine and power consumption are less than the maximum capacity of the compressor 20 (< 2 - 3 MW).

Evaporation of LNG 16aa within main tank 16 results in an increase in pressure of BOG 16ab within main tank 16. BOG 16ab is sucked in by compressor 20, heated in heat exchanger 28 and returned to power generation unit 12. Because of this, the pressure in the main tank 16 can be kept below the permissible threshold.

In order to adjust the pressure inside the main tank 16,

- The flow rate of BOG sent to the compressor 20 can be adjusted (if the flow rate is higher than the natural evaporation rate, the pressure inside the main tank 16 is reduced, and if the flow rate is lower than the natural evaporation rate, the main tank 16 (16) the pressure inside increases);

- A portion of the compressed gas (from the compressor 20) can be reinjected into the main tank 16 (for example, if the specifications of the compressor 20 set the inlet flow rate of the compressor to a given threshold (this is If not reduced below (greater than the natural evaporation rate), a portion of the compressed gas is reinjected into the main tank 16 via duct 38 in order to regulate the pressure inside the main tank 16.

The device 10 thus meets all the demands of the power generation unit 12 on the gases coming from the main tank 16 and maintains the pressure inside the tank at the required level (e.g. -100 mbarg to 700 mbarg). I order it.

2. Typical consumption stage

In the second operating phase, the consumption is at a normal level.

Natural evaporation in the main tank 16 is insufficient to meet the power demand of the power generation unit 12. Forced evaporation is necessary to meet the energy needs of the ship: this phase includes two detailed steps:

- Steps to prepare for forced evaporation: Fill the surge tank (18) and pump (36) with liquefied natural gas.

- Forced evaporation step: The liquid from the surge tank 18 is sent to the device and evaporated.

- Preparing for forced evaporation (Figure 3).

The first stage is between the main tank 16 and the surge tank 18 by reducing the pressure in the surge tank 18 and/or increasing the pressure in the main tank 16, for example -500 mbar. is to create a pressure difference. The internal pressure of main tank 16 can be increased by reinjecting compressed BOG, as described above. The internal pressure of surge tank 18 can be reduced by sucking natural gas within the surge tank with compressor 20. Due to this pressure difference, the LNG contained in the main tank 16 can be sucked in from a height of 10 m.

When the pressure in the main tank 16 increases, the BOG contained in the main tank 16 tends to discharge LNG from the main tank 16, thereby causing the LNG to flow from the inside of the duct 22 to the surge tank 18. circulate. When the pressure in the surge tank 18 decreases, LNG is sucked from the main tank 16 toward the surge tank 18. This pressure difference contributes to the formation and flash evaporation of BOG in the surge tank 18. BOG is sucked in by the compressor 20 to maintain the pressure difference between the main tank 16 and the surge tank 18.

The second step is to fill pump 36 with liquefied natural gas. Once the surge tank 18 is filled with liquefied natural gas to the required level, for example up to 90% of the volume of the surge tank, the LNG is forced by gravity into the pump 36. The pump 36 must be completely filled with liquid, otherwise bubbles may form and damage the pump. LNG flows from duct 32 to pump 36 and through the pump, keeping pump 36 stationary.

In order to regulate the pressure in the main tank 16, these operations can be combined with the first operation stage.

- Forced evaporation step (Figure 4).

The fluid from the surge tank 18 is sent to the power generation unit 12 by circulating the fluid.

LNG from surge tank 18 is sent to power generation unit 12 through heat exchanger 34. The LNG sent to the power generation unit 12 is conditioned by a pump 36. The power generation unit 12 preferentially receives gas from the compressor 20 (which regulates the pressure in the main tank 16 and the surge tank 18), and the gas replenishment takes LNG into the heat exchanger 34. The pump 36 is used to circulate the LNG to the valve 33b in order to vaporize the LNG preferably completely before heating it internally. As mentioned above, supplying LNG to the surge tank is achieved by depressurizing the surge tank 18 with respect to the main tank 16. The LNG discharged from the surge tank 18 is regulated by the pump 36. The level of LNG in the surge tank 18 is adjusted to maintain the required level, for example between 10% and 90% of the volume of the surge tank.

In order to regulate the pressure in the main tank 16, these operations can be combined with the first operation stage.

3. Non-consumption phase (see Figure 5)

This operating stage is activated in an emergency. The power generation unit 12 is closed, which means that there is no fuel gas consumption. The heat exchanger (28), compressor (20) and pump (36) are operated by an emergency generator.

For this step, it is assumed that the main tank 16 and surge tank 18 contain LNG. A pump (36) circulates LNG from the surge tank (18) to the LNG droplet atomizer boom (52). Because there is a pressure difference between the main tank 16 and the surge tank 18, LNG continues to circulate from the main tank 16 to the surge tank 18 where the LNG is evaporated. This means that the LNG formed in the surge tank 18 is supercooled with respect to the LNG contained in the main tank 16. The LNG droplet atomizer boom 52 receives supercooled liquefied gas from the surge tank 18 and sprays droplets of this liquefied gas into the BOG of the main tank 16. This condenses the BOG in the main tank 16 and reduces and maintains the pressure inside the main tank 16.

Due to this, the pressure inside the main tank 16 is regulated by the flow of LNG coming from the surge tank 18 and atomized by the LNG droplet atomizer boom 52. This operating step can be combined with a first operating step or a second operating step in order to reduce the pressure inside the main tank 16.

4. Charging step (see Figure 6)

Valve 23d is open. LNG is sent from the filling station to the main tank 16. Since the BOG that evaporates during charging is discharged by opening the valve 31a and valve 31c, a free flow of BOG toward the charging station is generated.

Figure 7 shows a device 110 of an alternative embodiment according to the invention, which differs from the device 10 of the previous embodiment because it comprises two surge tanks 18, 40. .

The features related to the device 10 described above can be applied to the device 110 as long as they do not contradict the description below.

Duct 22 is connected to each of the surge tanks 18 and 40, with one end 22b connected to the LNG inlet 18a of surge tank 18 and the LNG inlet 40a of surge tank 40. It includes an end portion 22c. In addition to the valves 23b and 23d of the duct 22 described above, valves 23e and 23f are coupled to each of the ends 23b and 23d.

In this case, each surge tank 18, 40 contains four holes, two of which are inlets 18a, 40a, 18d, 40d and the other two are outlets 18b, 40b, 18c, 40c). The inlets 18a and 40a are respectively connected to the ends 22b and 22c of the duct 22 and are configured to receive LNG, so that each surge tank 18 and 40 receives LNG directly from the main tank 16. It is configured to receive supply.

Outlets 18b, 40b are gas outlets, especially BOG outlets, and outlets 18c, 40c are LNG outlets. The outlets 18b and 40b are respectively connected to ends 26a and 26c of the duct 26, and the opposite end 26b of the duct 26 is connected to the inlet 20a of the compressor 20, as described above. , or connected to the inlet 28aa of the first circuit 28a of the heat exchanger 28.

In addition to the valve 27, the duct 26 includes a valve coupled to each of its ends 26a, 26b.

Another duct 42 connects the outlet 20b of the compressor 20 to the outlets 18d and 40d of the tank. In this case this is a gas inlet or a compressed BOG inlet, since the tanks 18, 40 can be supplied with compressed BOG, as described in more detail below. The duct 42 includes a valve 43 to stop the circulation of fluid from the outlet of the compressor 20 to the tanks 18 and 40. Additionally, each of the inlets 18d and 40d is coupled with a valve configured to isolate the tanks from each other.

The outlets 18c and 40c of the tanks 18 and 40 are connected to the ends 32a and 32c of the duct 32, which is connected to the outlet 20b of the compressor 20. This duct 32 includes or is connected to a heat exchanger 34 . The duct also contains two valves 33a, 33b, one of which is, for example, a pressure reducing valve 33b. In the example shown, the valve 33b, the heat exchanger 34 and the valve 33a are arranged from upstream to downstream, that is, from the tanks 18, 40 to the outlet 20b of the compressor 20. . The valves are also connected to each of the outlets 18c and 40c.

Duct 32 is connected to the outlet 20b of compressor 20 immediately upstream from valve 41. Additionally, at the outlet of valve 33a, duct 32 is connected to duct 38 immediately downstream from valve 39 by valve 33c.

In the example shown, LNG discharged from surge tank 18 is heated by heat exchanger 34 before being supplied to compressor 12. For this purpose, a duct 32 is connected to the inlet 34aa of the first circuit 34a of the heat exchanger 34 and the outlet 34ab of the first circuit 34a of the heat exchanger 34. It is connected to the valve (33a). Since the first circuit 34a is a low-temperature circuit, the fluid circulating in the first circuit 34a is heated by the fluid circulating in the second circuit 34b, known as the high-temperature circuit of the heat exchanger 34.

If valve 33b is a pressure reducing valve configured to vaporize all of the LNG into FBOG, the FBOG is heated by heat exchanger 34 before being supplied to power generation unit 12. Therefore, preferably, the valve 33b is configured such that the pressure of the FBOG at the outlet is equal to the operating pressure of the fuel gas in the power generation unit 12.

A duct (50) connects the LNG droplet atomizer boom (52) to the duct (32). The upstream end of the duct is connected to duct 32, immediately downstream from valve 33b, and the downstream end of the duct is connected to LNG droplet atomizer boom 52. Accordingly, as noted above, it should be noted that LNG contained within surge tanks 18, 40 may be supplied to LNG droplet atomizer boom 52.

In the example shown, the pressure relief in surge tank 18 should be sufficient to allow LNG to circulate in duct 22. The duct 22 comprises a vertical portion forming a plunger and submerged in the LNG of the main tank 16, the upper end of which is connected to the remainder of the duct 22 by an elbow connector. It is done. The pressure difference between the two tanks 16, 18 is preferably equal to the height of the duct 22 (specifically, the duct from the bottom of the main tank to the L-shaped connector), excluding load losses in the duct 22. The height of the vertical part of (22) - when the main tank (16) is empty, the LNG must be raised to this height) must be greater than the hydrostatic pressure generated by it. In another version, if the surge tank 18 (more specifically the outlet 22b) is below this level and the duct 22 is full (e.g. the main tank 16 is almost full), (by a smaller pressure difference when) the pressure difference should become smaller.

The pressure difference can be adjusted in the following manner:

- The gas demand of the power generation unit 12 regulates the valves associated with the outlets 18c, 40c of the surge tanks 18, 40.

- The pressure difference is adjusted so that the surge tanks can be filled quickly enough (the system is also regulated by the gas demand of the power generation unit 12).

Each of the surge tanks 18 and 40 functions as the surge tank 8 of the device 10. The surge tanks 18, 40 also serve another purpose since they are connected to the outlet 20b of the compressor 20. Compressed BOG from the compressor 20 and supplied to the surge tanks 18, 40 can be used to pressurize the surge tanks 18, 40 and exit 18c, 40c of the surge tanks 18, 40. It can be used to pass LNG (18aa, 40aa) through. Accordingly, the outlet does not need to be equipped with a pump, such as the pump 36 used in the device 10, to discharge LNG out of the surge tanks 18, 40.

The fuel gas supply device has two main purposes:

- Fuel gas is supplied to the main tank (e.g. 50 kg/h to 2000 kg/h) at a given pressure (e.g. 6 bar to 300 bar) and a given temperature (e.g. 20° C.) at the required flow rate (e.g. 50 kg/h to 2000 kg/h) 16) supply to the ship's power generation unit; The fuel gas may be in a gaseous state (vapor) or a liquid state;

- regulating the pressure inside the main tank 16 and maintaining this pressure within an acceptable range (eg -100 mbarg to +700 mbarg);

contribute to

The illustrated device 10 comprises, for example, a main tank designed to receive cryogenic liquid (e.g. with a volume of 1000 m ³ to 10000 m ³ and an applied pressure of -100 mbarg to +700 mbarg) at atmospheric pressure. 16) and a surge tank 18 configured to receive cryogenic fluid (e.g., with a volume of 1 m ³ to 20 m ³ and an applied pressure of -500 mbarg to 6000 mbarg). In order to transfer fluid from the main tank 16 to the surge tanks 18 and 40, a pressure difference between the main tank 16 and the surge tanks 18 and 40 by the compressor 20 (e.g., surge tank +500 mbarg) is generated in the main tank. The fluid in the surge tanks 18, 40 is sent to the power generation unit 12 by the vaporization valve 33b. The level of fluid in each surge tank is adjusted by a suitable device, for example between 10% and 90% of the internal volume of the surge tank.

The controls and appropriate mechanisms of the device are designed to maintain the internal pressure of the main tank 16 at the required level (eg -100 mbarg to 700 mbarg). Each tank of the device 110 is therefore preferably equipped with a pressure sensor and/or a level sensor.

Figures 8 to 12 show the operating stages of the device of Figure 7, which correspond to different speed levels of the vessel equipped with this device.

The liquefied gas cooling process is described in three steps:

1. Minimum consumption stage: natural evaporation meets the power demand of the power generation unit 12 (the ship's propulsion engines are stopped or run at low load and the gas is mainly used to meet heating and electricity needs) used).

2. Normal consumption stage: Natural evaporation does not guarantee the ship's power needs.

3. Zero consumption phase (except the gas compressor, all onboard gas consumers of the power generation unit 12 are shut down).

4. Charging step.

This is a sequential process, with surge tanks being filled and emptied alternately. Since the process for surge tank 40 is symmetrical to that for surge tank 18, this description only relates to filling and emptying surge tank 18.

1. Minimum consumption stage (see Figure 8)

In the operational phase shown in Figure 8, the ship's main engine and power consumption are less than the maximum capacity of the compressor 20 (< 2 - 3 MW).

Evaporation of LNG 16aa within main tank 16 results in an increase in pressure of BOG 16ab within main tank 16. BOG 16ab is sucked in by compressor 20, heated in heat exchanger 28 and returned to power generation unit 12. Because of this, the pressure in the main tank 16 can be kept below the permissible threshold.

In order to adjust the pressure inside the main tank 16,

- The flow rate of BOG sent to the compressor 20 can be adjusted (if the flow rate is higher than the natural evaporation rate, the pressure inside the main tank 16 is reduced, and if the flow rate is lower than the natural evaporation rate, the main tank 16 (16) the pressure inside increases);

- A portion of the compressed gas (from the compressor 20) can be reinjected into the main tank 16 (for example, if the specifications of the compressor 20 set the inlet flow rate of the compressor to a given threshold (this is If not reduced below the natural evaporation rate, a portion of the compressed gas is reinjected into the main tank 16 via duct 38.

The device 10 thus meets all the demands of the power generation unit 12 on the gases coming from the main tank 16 and maintains the pressure inside the tank at the required level (e.g. -100 mbarg to 700 mbarg). I order it.

2. Typical consumption stage

In the second operating phase, the consumption is at a normal level.

Natural evaporation in the main tank 16 is insufficient to meet the power demand of the power generation unit 12. Forced evaporation is necessary to meet the energy needs of the ship: this involves two detailed steps:

- Preparing for forced evaporation: Fill the surge tank (18) with liquefied natural gas from the main tank (16).

- Forced evaporation stage: the liquid from the surge tank 18 is sent to the heat exchanger and then back to the power generation unit (while the other surge tank 40 is filled with LNG).

- Preparing for forced evaporation (see Figure 9).

The first stage is between the main tank 16 and the surge tank 18 by reducing the pressure in the surge tank 18 and/or increasing the pressure in the main tank 16, for example -500 mbar. is to create a pressure difference. The internal pressure of the main tank 16 may be increased as described in the first operating step. The internal pressure of surge tank 18 can be reduced by sucking the natural gas within this surge tank with compressor 20. Due to this pressure difference (-500 mbar), LNG from the main tank 16 can be sucked in from a height of approximately 10 m.

When the pressure increases in the main tank 16, the BOG in the main tank 16 causes the LNG to discharge from the main tank 16, thereby circulating the LNG inside the duct 22 to the surge tank 18. When the pressure in the surge tank 18 decreases, the LNG in the main tank 16 is sucked toward the surge tank 18. This pressure difference contributes to the instantaneous evaporation of LNG in the surge tank 18. Boil-off gas is sucked in by the compressor 20 to maintain the pressure difference between the main tank 16 and the surge tank 18. The surge tank 18 is filled with liquefied natural gas, for example up to 90% of the volume of the surge tank.

In order to regulate the pressure in the main tank 16, these operations can be combined with the first operation stage.

- Forced evaporation step (Figure 10).

The second step is to pressurize the surge tank 18 with compressed natural gas from compressor 20.

The duct 22 and valve 23b used to fill the surge tank 18 with fluid and to suck natural gas from the surge tank are closed. Compressed gas from compressor 20 is sent to surge tank 18 (by flash evaporation, if necessary) and pressurizes surge tank 18. This circulates LNG from surge tank 18 to heat exchanger 34 and power generation unit 12.

While the surge tank 18 is used to provide LNG to the power generation unit 12, the surge tank 40 is filled with LNG from the main tank 16 (only valves 23d and 23e are closed). and the valve 23b and valve 23f remain open). The device 110 is preferably designed to fill the surge tank 40 at a faster rate than the rate at which the compressor 20 discharges LNG from the surge tank 18.

The flow rate and pressure of LNG discharged from the surge tank 18 are controlled by the valve 33b. The surge tank 18 is used until the LNG level is very low (eg 5% of volume). At that time, purge tank 40 is ready to provide LNG to power generation unit 12. Next, the main tank 16 is filled with LNG as described in the first step.

During this phase of operation, purge tanks 18, 40 are alternately filled with LNG and compressed by compressor 20 to provide LNG to power generation unit 12.

In order to regulate the pressure in the main tank 16, these operations can be combined with the first operation stage.

3. Non-consumption phase (see Figure 11)

This operating stage is activated in an emergency. The power generation unit 12 is closed, which means that there is no fuel gas consumption. The heat exchanger 28 and compressor 20 are operated by an emergency generator.

For this step, it is assumed that the main tank 16 and surge tank 18 contain LNG. Compressor 20 is used to increase the internal pressure of the purge tank 18 by sending compressed gas to the purge tank 18, which discharges LNG from the purge tank toward the LNG droplet atomizer boom 52. From the boom 52, LNG is sprayed into the BOG of the main tank 16. This participates in reducing and maintaining the pressure in the main tank 16 by condensing the BOG inside the main tank 16.

Due to this, the pressure inside the main tank 16 is regulated by the flow of LNG coming from the surge tank 18 and atomized by the LNG droplet atomizer boom 52.

If surge tank 18 is empty, this operation is repeated with surge tank 40 and surge tank 18 is filled.

This operating step can be combined with a first operating step or a second operating step in order to reduce the pressure inside the main tank 16.

4. Charging step (see Figure 12)

Valve 23d is open. LNG is sent from the filling station to the main tank 16. Since the BOG that evaporates during charging is discharged by opening the valve 31a and valve 31c, a free flow of BOG toward the charging station is generated.

Figure 13 shows an alternative embodiment of device 210 according to the invention, which differs from the device 110 of the previous embodiment because it also includes a pump 36.

The features related to the device 110 described above can be applied to the device 210 as long as they do not contradict the description below.

The pump 36 is disposed in a duct 54, the upstream end of which is connected to the outlets 18c, 40c of the purge tanks 18, 40 immediately downstream from the valves of the purge tanks. The downstream end of is connected to the duct 32 immediately upstream from the valve 33b. This duct 54 includes a valve 56 extending parallel to a portion of duct 32 containing an additional valve 58. According to this configuration, pump 36 may or may not be used to discharge the LNG contained within purge tanks 18 and 40 to LNG droplet atomizer boom 52 and/or power generation unit 12.

The device therefore features a hybrid operating mode with respect to the devices 10, 110 of the previous embodiments.

Claims (39)

A device (10, 110, 210) installed on a ship (14) for supplying liquid fuel to a power generation unit (12),
- main tank (16) of liquefied gas,
- at least a first liquefied gas surge tank (18),
- a first end (32a) open to the first liquefied gas surge tank (18) for transferring liquefied gas from the first liquefied gas surge tank (18) to the power generation unit (12); a first duct (32) having a second end (32b) connected to the power generation unit (12) for supplying liquid fuel to
- transporting liquefied gas from the main tank (16) to the first liquefied gas surge tank (18), comprising: a first end (22a) configured to be immersed in the liquefied gas (24) contained in the main tank (16); a second duct (22) comprising a second end (22b) leading to the first liquefied gas surge tank (18) for supplying gas to the first liquefied gas surge tank (18), and
- Suction liquid from the first liquefied gas surge tank so that the liquefied gas coming from the main tank 16 is transported by the second duct 22 and supplied to the first liquefied gas surge tank 18 Pressure reduction means (20, 36) of the first liquefied gas surge tank (18) with respect to the main tank (16), configured to apply an operating pressure lower than the pressure of the main tank to the first liquefied gas surge tank,
In the device comprising,
Device (10, 110, 210), characterized in that the pressure reducing means comprises at least one compressor (20) and the operating pressure is lower than atmospheric pressure. 2. Device (10, 110, 210) according to claim 1, characterized in that the pressure reducing means comprises an outlet (20b) adapted to be connected to the power generation unit (12). 3. Device (10, 110, 210) according to claim 1 or 2, characterized in that a pump is connected to the first duct and is configured to suck liquefied gas from the first liquefied gas surge tank. 4. The method of claim 3, wherein the compressor (20) is connected to a third pressure reduction duct (26) of the first liquefied gas surge tank (18), and the first end (26a) of the third pressure reduction duct (26) is It is connected to the first liquefied gas surge tank 18, and the second end 26b of the third pressure reduction duct 26 is connected to the inlet 20a of the compressor, and the third pressure reduction duct 26 is connected to the first pressure reduction duct 26. 1 A device (10, 110, 210) characterized in that it is configured to suck boil-off gas from a liquefied gas surge tank and supply the boil-off gas to the compressor. 5. Device (10, 110, 210) according to claim 4, characterized in that the compressor (20) has an outlet (20b) connected to the power generation unit for supplying fuel gas to the power generation unit. 5. Apparatus (10, 110, 210) according to claim 4, characterized in that the second end of the third pressure reduction duct is connected to the compressor by a first heat exchange circuit. 7. Device (10, 110, 210) according to claim 6, characterized in that the device comprises a fourth duct conveying gas from the main tank to the compressor. 8. Apparatus (10, 110, 210) according to claim 7, wherein the fourth duct comprises a first end connected to the main tank and a second end connected to the compressor. 9. The method of claim 8, wherein the second end of the fourth duct, together with the second duct, is connected to an inlet of the first heat exchange circuit, and one outlet of the first heat exchange circuit is connected to the compressor. A device (10, 110, 210) characterized in that there is. 3. Device (10, 110, 210) according to claim 1 or 2, characterized in that the first end (22a) of the second duct (22) does not comprise a pump. 3. Device (10, 110, 210) according to claim 1 or 2, characterized in that the first duct comprises at least one pump and/or one pressure reducing valve and/or one heat exchanger. 12. Device (10, 110, 210) according to claim 11, wherein the pump is configured to be controlled based on the fuel gas demand of the power generation unit. 3. The apparatus according to claim 1 or 2, wherein the device comprises a fifth liquid return duct from the pressure reducing means to the main tank, the first end of the fifth liquid return duct being connected to an outlet of the pressure reducing means. and the second end is connected to the main tank (10, 110, 210). 3. Device (10, 110, 210) according to claim 1 or 2, characterized in that the device comprises a second liquefied gas surge tank (40). 15. The method of claim 14, wherein the second liquefied gas surge tank (40)
- the first duct (32) comprising a third end (32c) connected to the second liquefied gas surge tank (40), and
- Device (10, 110, 210), characterized in that it is connected to the second duct (22) comprising a third end (22c) connected to the second liquefied gas surge tank (40). According to clause 15,
The compressor 20 is connected to a third pressure reduction duct 26 of the first liquefied gas surge tank 18, and the first end 26a of the third pressure reduction duct 26 is connected to the first liquefied gas surge tank 18. It is connected to the tank 18, and the second end 26b of the third pressure reducing duct 26 is connected to the inlet 20a of the compressor 20, and the second liquefied gas surge tank 40 is connected to the inlet 20a of the compressor 20. Device (110, 210), characterized in that it is connected to the third pressure relief duct (26) comprising a third end (26c) leading to the second liquefied gas surge tank (40). 15. The method of claim 14, wherein the device comprises a fifth duct (42) supplying gas to the first liquefied gas surge tank (18) and the second liquefied gas surge tank (40), and a fifth duct ( The first end 42a of 42) is connected to the outlet 20b of the pressure reducing means 20, the second end 42b is connected to the first liquefied gas surge tank 18, and the second end 42b is connected to the first liquefied gas surge tank 18. The third end 42c is connected to the second liquefied gas surge tank 40, and the fifth duct supplies compressed gas to the first liquefied gas surge tank and/or the second liquefied gas surge tank. A device (110, 210) characterized in that it is configured. 3. The method of claim 1 or 2, wherein the first duct is connected to a liquefied gas atomizer boom in the main tank by a sixth duct, and the liquefied gas is configured to condense at least a portion of the boil-off gas in the main tank. Device (10, 110, 210), characterized in that the spray boom is configured to spray liquefied gas in the form of droplets onto the boil-off gas in the main tank. Device (10, 110, 210) according to claim 1 or 2, characterized in that each tank is equipped with a pressure sensor and/or a level sensor. 3. Device (10, 110, 210) according to claim 1 or 2, characterized in that the surge tank or each surge tank is arranged below the upper part of the main tank. The device (10, 110, 210) according to claim 1 or 2, wherein the surge tank or each surge tank is disposed outside the main tank. 3. Device (10, 110, 210) according to claim 1 or 2, characterized in that the surge tank or each surge tank can be used for expansion and/or separation purposes. 3. Device (10, 110, 210) according to claim 1 or 2, characterized in that the main tank is a membrane tank. 24. Device (10, 110, 210) according to claim 23, wherein the main tank is configured to withstand a pressure of less than 3000 mbarg, or less than 750 mbarg. A vessel used to transport liquefied gas,
A vessel, characterized in that it comprises at least one device (10, 110) according to claim 1 or 2. A method of supplying fuel to a power generation unit (12) installed on a ship (14) using the device (10) according to claim 1 or 2, comprising:
- a first liquefied gas surge tank by depressurizing the first liquefied gas surge tank 18 with respect to the main tank 16 so that the liquefied gas is transferred from the main tank 16 to the first liquefied gas surge tank 18 Step A, filling (18);
A method comprising: According to clause 26,
- step B1 in which the power generation unit 12 is fueled by the compressor 20 by means of gas intake from the first liquefied gas surge tank 18;
A method comprising: 28. The apparatus of claim 27, wherein the device (10) comprises a second liquefied gas surge tank (40),
- The compressor 20 supplies gas from the first liquefied gas surge tank 18 and/or the second liquefied gas surge tank 40 to the power generation unit 12, thereby supplying the liquefied gas to the first liquefied gas surge tank 40. Step B2 circulating in duct 32;
A method comprising: 29. The method of claim 28, wherein during step B1 or step B2, liquefied gas is transferred from the main tank (16) to the second liquefied gas surge tank (40), using the compressor (20). Characterized in that the second liquefied gas surge tank (40) is supplied with liquefied gas by depressurizing the tank (40) with respect to the main tank (16). 27. The method of claim 26, wherein the device includes a fourth duct for transferring gas from the main tank (16) to the compressor (20), a second liquefied gas surge tank (40) and a first liquefied gas surge tank (18). It includes a fifth duct 42 that supplies gas to the second liquefied gas surge tank 40,
Characterized in that during step A, the pressure inside the main tank is controlled by regulating the gas flow circulating in the fourth duct and/or the fifth duct. 27. The apparatus of claim 26, wherein the device comprises a pump connected to the first duct and configured to draw liquefied gas from the first liquefied gas surge tank,
During or after step A, the pump in the first duct is supplied with liquefied gas from the first liquefied gas surge tank. 27. The apparatus of claim 26, wherein the device comprises a pump connected to the first duct and configured to draw liquefied gas from the first liquefied gas surge tank,
Step B3 in which the power generation unit is supplied with fuel by the first duct using the pump;
A method comprising: 27. The method of claim 26, wherein during step A, reduced pressure is maintained for a predetermined period of time. 27. The first liquefied gas surge tank according to claim 26, wherein in the second duct, load loss, if any, is greater than the hydrostatic pressure generated by the straight vertical height of the second duct. Characterized in that depressurization is achieved by imposing a pressure difference between (18) and said main tank (16). 27. The apparatus of claim 26, wherein the device comprises a pump connected to the first duct and configured to draw liquefied gas from the first liquefied gas surge tank,
wherein the pump is controlled based on the fuel gas demand of the power generation unit. 27. The method of claim 26, wherein at least some of the valves included in one or more of the ducts are controlled based on the fuel gas demand of the power generation unit. 27. The method of claim 26, wherein when the level of liquefied gas within the first liquefied gas surge tank falls below a given threshold level, the first liquefied gas surge is used to increase the supply flow of liquefied gas to the first liquefied gas surge tank. A method characterized by an increase in pressure difference between the tank and the main tank. 27. The method of claim 26, wherein the device (10) comprises a second liquefied gas surge tank (40),
and wherein the pressure difference between one of the surge tanks and the main tank is adjusted based on the rate of filling of the other surge tank with liquefied gas from the main tank. According to clause 26,
the first duct is connected to a liquefied gas atomizer boom in the main tank by a sixth duct,
A method characterized in that the liquefied gas contained in the first liquefied gas surge tank is transported to the liquefied gas atomizer boom by the first duct and the sixth duct.

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