KR102632391B1 - Fuel supply system for ship - Google Patents

Abstract

The ship's fuel supply system is initiated.
The ship's fuel supply system includes a storage tank for storing liquefied gas; An additional compressor that compresses the boil-off gas discharged from the storage tank; a multi-stage compression unit that compresses the boil-off gas compressed by the additional compressor in multiple stages; a heat exchanger that cools the boil-off gas discharged from the storage tank by heat-exchanging the boil-off gas compressed by the multi-stage compression unit with a refrigerant; and expansion means for expanding the fluid cooled by the heat exchanger, wherein the multi-stage compression unit is composed of two stages of a first compressor and a second compressor, and a portion of the boil-off gas compressed by the multi-stage compression unit or All of it is sent to the high-pressure engine, and among the boil-off gases compressed by the multi-stage compression unit, the excess boil-off gas that is not used in the high-pressure engine is sent to the heat exchanger.

Description

Ship's fuel supply system {FUEL SUPPLY SYSTEM FOR SHIP}

The present invention relates to a fuel supply system for a ship that can optimize a system for compressing fuel supplied to an engine to high pressure.

Recently, the consumption of liquefied gas such as liquefied natural gas (LNG) is rapidly increasing worldwide. Liquefied gas, which is made by liquefying gas at low temperature, has a much smaller volume than gas, so it has the advantage of increasing storage and transportation efficiency. In addition, liquefied gas, including liquefied natural gas, can remove or reduce air pollutants during the liquefaction process, so it can be viewed as an eco-friendly fuel with low emissions of air pollutants during combustion.

Liquefied natural gas is a colorless and transparent liquid obtained by liquefying natural gas containing methane as a main component by cooling it to about -163°C, and has a volume of about 1/600 of that of natural gas. Therefore, when natural gas is liquefied and transported, it can be transported very efficiently.

However, since the liquefaction temperature of natural gas is extremely low at -163°C at normal pressure, liquefied natural gas is sensitive to temperature changes and easily evaporates. For this reason, the storage tank that stores liquefied natural gas is insulated, but external heat is continuously transferred to the storage tank, so during the transportation of liquefied natural gas, liquefied natural gas is continuously naturally vaporized within the storage tank, producing boil-off gas (boil). -Off Gas, BOG) occurs. This is also true for other low-temperature liquefied gases such as ethane.

Evaporation gas is a type of loss and is an important issue in transportation efficiency. In addition, if evaporation gas accumulates in the storage tank, the pressure inside the tank may increase excessively, and in severe cases, there is a risk of tank damage. Therefore, various methods are being studied to treat boil-off gas generated within the storage tank. Recently, for the treatment of boil-off gas, a method of re-liquefying the boil-off gas and returning it to the storage tank, using the boil-off gas as fuel for ship engines, etc. Methods such as using it as an energy source for consumers are being used.

Methods for re-liquefying the boil-off gas include a method of re-liquefying the boil-off gas by heat-exchanging it with a refrigerant using a refrigeration cycle using a separate refrigerant, and a method of re-liquefying the boil-off gas itself as a refrigerant without a separate refrigerant. There is. In particular, the system employing the latter method is called the Partial Re-liquefaction System (PRS).

Meanwhile, among engines generally used in ships, engines that can use natural gas as fuel include gas fuel engines such as DFDE, ME-GI engines, and X-DF engines.

DFDE is used for power generation and consists of four strokes. The Otto Cycle is adopted in which natural gas, which has a relatively low pressure of about 6.5 bara, is injected into the combustion air inlet and compressed as the piston rises.

The ME-GI engine is used for propulsion and consists of two strokes. The diesel cycle is adopted in which high-pressure natural gas around 300 bara is directly injected into the combustion chamber near the top dead center of the piston.

The X-DF engine is used for propulsion and consists of two strokes. It uses medium pressure natural gas of about 16 bara as fuel and adopts the Otto cycle.

The present invention seeks to provide a ship fuel supply system that optimizes the multi-stage compression unit, which compresses natural gas to the pressure required by a high-pressure engine, to be composed of two stages.

According to one aspect of the present invention for achieving the above object, a storage tank for storing liquefied gas; An additional compressor that compresses the boil-off gas discharged from the storage tank; a multi-stage compression unit that compresses the boil-off gas compressed by the additional compressor in multiple stages; a heat exchanger that cools the boil-off gas discharged from the storage tank by heat-exchanging the boil-off gas compressed by the multi-stage compression unit with a refrigerant; and expansion means for expanding the fluid cooled by the heat exchanger, wherein the multi-stage compression unit is composed of two stages of a first compressor and a second compressor, and a portion of the boil-off gas compressed by the multi-stage compression unit or All of the boil-off gas is sent to the high-pressure engine, and the excess boil-off gas not used in the high-pressure engine among the boil-off gas compressed by the multi-stage compression unit is sent to the heat exchanger.

The fuel supply system of the ship may further include a gas-liquid separator installed at a rear end of the expansion means to separate the re-liquefied liquefied gas and the boil-off gas in a gaseous state.

The ship's fuel supply system includes a pump that pressurizes the liquefied gas inside the storage tank; and a vaporizer for vaporizing the liquefied gas pressurized by the pump, and the gas vaporized by the vaporizer can be supplied as fuel for the high-pressure engine.

The boil-off gas separated by the gas-liquid separator can be combined with the boil-off gas discharged from the storage tank and used as a refrigerant in the heat exchanger.

The additional compressor may be a compressor that compresses fluid at a lower pressure than the first compressor and the second compressor.

The boil-off gas compressed by the additional compressor may be at 45°C and 6.5 bara.

A portion of the boil-off gas compressed by the additional compressor may be branched and supplied to the low-pressure engine.

The boil-off gas compressed by the multi-stage compression unit and then sent to the heat exchanger may have a temperature of 43°C and 300 bara.

The high-pressure engine can use gas at 45°C and 300 bara as fuel.

According to another aspect of the present invention for achieving the above object, a storage tank for storing liquefied gas; A multi-stage compression unit that compresses the boil-off gas discharged from the storage tank in multiple stages; a heat exchanger that cools the boil-off gas discharged from the storage tank by heat-exchanging the boil-off gas compressed by the multi-stage compression unit with a refrigerant; and expansion means for expanding the fluid cooled by the heat exchanger, wherein the multi-stage compression unit is composed of two stages of a first compressor and a second compressor, and a portion of the boil-off gas compressed by the multi-stage compression unit or All of it is sent to the high-pressure engine, and among the boil-off gas compressed by the multi-stage compression unit, the excess boil-off gas not used in the high-pressure engine is sent to the heat exchanger, and the pressure of the boil-off gas discharged from the storage tank is 6.6 bara. A fuel supply system for a ship is provided, characterized in that.

The storage tank may be a Type C tank made of a component containing high manganese steel.

The fuel supply system of the ship may further include a gas-liquid separator installed at the rear end of the expansion means to separate the re-liquefied liquefied gas and gaseous boil-off gas, and the gas-liquid separator stores the fluid up to 6.7 bara and then can be discharged.

The gas-liquid separator may be a Type C gas-liquid separator made of a component containing high manganese steel.

The boil-off gas separated by the gas-liquid separator can be combined with the boil-off gas discharged from the storage tank and used as a refrigerant in the heat exchanger.

The ship's fuel supply system may further include a heater installed between the heat exchanger and the multi-stage compression unit.

A portion of the boil-off gas heated by the heater may be branched and supplied to the low-pressure engine.

The boil-off gas heated by the heater may be at 45°C and 6.5 bara.

The boil-off gas compressed by the multi-stage compression unit and then sent to the heat exchanger may be at 43°C and 300 bara.

The high-pressure engine can use gas at 45°C and 300 bara as fuel.

The ship's fuel supply system includes a pump that pressurizes the liquefied gas inside the storage tank; And it may further include a vaporizer for vaporizing the liquefied gas pressurized by the pump, and the gas vaporized by the vaporizer can be supplied as fuel for the high-pressure engine.

According to the present invention, the multi-stage compression unit, which conventionally consisted of 5 stages, can be configured into 2 stages, thereby reducing the cost of installing and operating the equipment.

1 is a schematic diagram of a fuel supply system for a ship according to a first preferred embodiment of the present invention.
Figure 2 is a schematic diagram of a fuel supply system for a ship according to a second preferred embodiment of the present invention.

Hereinafter, the structure and operation of a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. The ship fuel supply system of the present invention can be applied to a variety of applications, such as ships equipped with engines using natural gas as fuel and ships containing liquefied gas storage tanks. Additionally, the following examples may be modified into various other forms, and the scope of the present invention is not limited to the following examples.

Additionally, the fluid in each line of the present invention may be in any one of a liquid state, a gas-liquid mixture state, a gas state, and a supercritical fluid state, depending on the operating conditions of the system.

1 is a schematic diagram of a fuel supply system for a ship according to a first preferred embodiment of the present invention. The first embodiment shown in FIG. 1 can be particularly preferably applied to a liquefied natural gas carrier.

Referring to Figure 1, the fuel supply system of the ship of this embodiment includes a storage tank (T), a heat exchanger 100, an additional compressor 900, a multi-stage compression unit 200, and an expansion means 300. .

The storage tank (T) of this embodiment is equipped with a sealing and insulating barrier so that liquefied gas such as liquefied natural gas can be stored in a cryogenic state, but it cannot completely block heat transmitted from the outside, and the storage tank (T) Evaporation of liquefied gas continues inside and the internal pressure may increase. In order to prevent excessive increase in pressure due to such evaporated gas and maintain the internal pressure at an appropriate level, the evaporated gas inside the storage tank (T) is discharged. . The boil-off gas discharged from the storage tank (T) of this embodiment (point A1 in FIG. 1) may be approximately -130°C and 1.06 bara.

The heat exchanger 100 of this embodiment cools the boil-off gas discharged from the storage tank T by heat-exchanging the boil-off gas compressed by the multi-stage compression unit 200 with a refrigerant. The boil-off gas used as a refrigerant in the heat exchanger 100 after being discharged from the storage tank (T) (point B1 in FIG. 1) may be approximately 7°C and 1.04 bara.

The additional compressor 900 of this embodiment compresses the boil-off gas used as a refrigerant in the heat exchanger 100 after being discharged from the storage tank T. The additional compressor 900 of this embodiment may be a compressor that compresses fluid at a lower pressure than the first compressor 210 and the second compressor 220 included in the multi-stage compression unit 200.

The boil-off gas compressed by the additional compressor 900 of this embodiment (point C1 in FIG. 1) may be approximately 45°C and 6.5 bara.

According to this embodiment, a portion of the boil-off gas compressed by the additional compressor 900 may be branched and supplied to the low-pressure engine, and the remainder may be supplied to the multi-stage compression unit 200, and the low-pressure engine may be operated at approximately 45° C. It may be an engine that uses 6.5 bara gas as fuel.

The multi-stage compression unit 200 of this embodiment compresses the boil-off gas used as a refrigerant in the heat exchanger 100 after being discharged from the storage tank T in multiple stages to the required pressure of the high-pressure engine. The multi-stage compression unit 200 of this embodiment includes a first compressor 210 and a second compressor 220, and is composed of two stages, unlike the conventional five stages.

Part or all of the boil-off gas compressed by the multi-stage compression unit 200 of this embodiment is sent to the high-pressure engine, and the surplus boil-off gas not used in the high-pressure engine among the boil-off gas compressed by the multi-stage compression unit 200 is heat exchanged. It is sent to unit 100 and undergoes a reliquefaction process. The boil-off gas compressed by the multi-stage compression unit 200 and then sent to the heat exchanger 100 may be approximately 43°C and 300 bara (point D1 in FIG. 1), and the high pressure engine may have a temperature of approximately 45°C and 300 bara. It may be an engine that uses as fuel.

The expansion means 300 of this embodiment expands the cooled fluid by heat-exchanging the evaporation gas discharged from the storage tank T in the heat exchanger 100 with a refrigerant after being compressed by the multi-stage compression unit 200. The expansion means 300 of this embodiment may be an expansion valve such as a Joule-Thompson valve.

The boil-off gas that has undergone a compression process by the multi-stage compression unit 200, a cooling process by the heat exchanger 100, and an expansion process by the expansion means 300 is partially or entirely re-liquefied.

The ship's fuel supply system of this embodiment may further include a gas-liquid separator 400 installed at the rear of the expansion means 300 to separate the re-liquefied liquefied gas and the gaseous boil-off gas.

A first valve (V1) that controls the flow rate and opening and closing of the fluid may be installed on the line through which the boil-off gas separated by the gas-liquid separator 400 of this embodiment is discharged, and the gas-liquid separator 400 of this embodiment separates the gas-liquid separator 400 of this embodiment. A second valve (V2) that controls the flow rate and opening and closing of the fluid may be installed on the line through which the liquefied gas is discharged.

In addition, the boil-off gas separated by the gas-liquid separator 400 can be combined with the boil-off gas discharged from the storage tank (T) and used as a refrigerant in the heat exchanger 100, and the liquefied gas separated by the gas-liquid separator 400 Can be returned to the storage tank (T). The liquefied gas (point E1 in FIG. 1) returned to the storage tank (T) after being separated by the gas-liquid separator 400 may be -161°C and 1.06 bara.

The ship's fuel supply system of this embodiment may further include a pump 500 that pressurizes the liquefied gas inside the storage tank (T), and a vaporizer 600 that vaporizes the liquefied gas pressurized by the pump 500. there is.

The pump 500 and vaporizer 600 of this embodiment vaporize the liquefied gas inside the storage tank (T) and supply it to the engine when the evaporation gas inside the storage tank (T) does not satisfy the amount required by the engine. It plays a role. According to this embodiment, rather than vaporizing the liquefied gas and then compressing it, the liquefied gas is first compressed and then vaporized, so a pump (500) that is relatively inexpensive and has low operating costs without using a compressor to pressurize the gas. ) can be used, making it economical.

On the line where the liquefied gas discharged from the storage tank (T) passes through the pump 500 and the vaporizer 600 and is sent to the low-pressure engine or high-pressure engine, in order to meet the pressure and temperature conditions required by the low-pressure engine and the high-pressure engine, One or more of a pressure reducing device, a pressurizing device, and a heater may be installed.

Figure 2 is a schematic diagram of a fuel supply system for a ship according to a second preferred embodiment of the present invention. The second embodiment shown in FIG. 2 can be particularly preferably applied to ships that use liquefied natural gas as a propulsion fuel for ships.

Compared to the fuel supply system of the ship of the first embodiment shown in FIG. 1, the fuel supply system of the ship of the second embodiment shown in FIG. 2 does not include an additional compressor 900 and discharges the fuel from the storage tank (T). There is a difference in that the pressure of the evaporation gas is approximately 6.6 bara, and the differences will be mainly explained below. Detailed descriptions of the same members as the fuel supply system of the ship in the first embodiment described above will be omitted.

Referring to FIG. 2, the ship's fuel supply system of this embodiment, like the first embodiment, includes a storage tank (T), a heat exchanger 100, a multi-stage compression unit 200, and an expansion means 300. do. However, unlike the first embodiment, the ship's fuel supply system of this embodiment does not include an additional compressor 900.

Unlike the first embodiment, the storage tank T of this embodiment stores boil-off gas up to approximately 6.6 bara and then discharges it. The storage tank (T) of this embodiment may be a Type C tank made of a component containing high manganese steel. The boil-off gas discharged from the storage tank (T) (point A2 in FIG. 2) may be approximately -130°C and 6.6 bara.

The heat exchanger 100 of this embodiment, like the first embodiment, cools the boil-off gas discharged from the storage tank T by heat-exchanging the boil-off gas compressed by the multi-stage compression unit 200 with a refrigerant.

Like the first embodiment, the multi-stage compression unit 200 of this embodiment compresses the boil-off gas used as a refrigerant in the heat exchanger 100 after being discharged from the storage tank T in multiple stages up to the required pressure of the high-pressure engine. I order it.

The multi-stage compression unit 200 of this embodiment includes a first compressor 210 and a second compressor 220, as in the first embodiment, and is composed of two stages, unlike the conventional five stages. The multi-stage compression unit 200 of this embodiment can be configured in two stages because the pressure of the boil-off gas discharged from the storage tank (T) is approximately 6.6 bara, which is approximately the pressure of the boil-off gas discharged from the conventional storage tank. This is because it is higher than 1.06 bara.

The boil-off gas discharged from the storage tank (T), used as a refrigerant in the heat exchanger 100, and then supplied to the multi-stage compression unit 200 (point B2 in FIG. 2) is preferably approximately 45°C and 6.5 bara, In preparation for the case where the temperature of the boil-off gas at point B1 is low, the ship's fuel supply system of this embodiment may further include a heater 800 installed between the heat exchanger 100 and the multi-stage compression unit 200. there is.

According to this embodiment, the evaporation gas discharged from the storage tank (T) and used as a refrigerant in the heat exchanger 100 (if it includes the heater 800) is used as a refrigerant in the heat exchanger 100 and then used as a refrigerant in the heater 800. A portion of the heated boil-off gas may be branched and supplied to the low-pressure engine, and the remainder may be supplied to the multi-stage compression unit 200. The low-pressure engine is an engine that uses gas at approximately 45°C and 6.5 bara as fuel. It can be.

According to this embodiment, as in the first embodiment, part or all of the boil-off gas compressed by the multi-stage compression unit 200 is sent to the high-pressure engine, and the high-pressure boil-off gas compressed by the multi-stage compression unit 200 is sent to the high-pressure engine. Excess evaporative gas not used in the engine is sent to the heat exchanger 100 and undergoes a re-liquefaction process. The boil-off gas (point C2 in FIG. 2) sent to the heat exchanger 100 after being compressed by the multi-stage compression unit 200 may be approximately 43°C and 300 bara, and the high pressure engine may have a temperature of approximately 45°C and 300 bara. It may be an engine that uses as fuel.

The expansion means 300 of this embodiment, like the first embodiment, cools the evaporation gas discharged from the storage tank T in the heat exchanger 100 by heat-exchanging it with a refrigerant after being compressed by the multi-stage compression unit 200. expands the liquid. The expansion means 300 of this embodiment may be an expansion valve such as a Joule-Thompson valve.

As in the first embodiment, the evaporated gas that has gone through the compression process by the multi-stage compression unit 200, the cooling process by the heat exchanger 100, and the expansion process by the expansion means 300 is partly or entirely reused. It becomes liquefied.

The fuel supply system of the ship of this embodiment, like the first embodiment, may further include a gas-liquid separator 400 installed at the rear of the expansion means 300 to separate the re-liquefied liquefied gas and the gaseous boil-off gas. there is. However, the gas-liquid separator 400 of the present embodiment, unlike the first embodiment, stores the fluid up to approximately 6.7 bara and then discharges it, and may be a Type C gas-liquid separator made of a component containing high manganese steel.

According to this embodiment, like the first embodiment, a first valve (V1) for controlling the flow rate and opening and closing of the fluid may be installed on the line through which the boil-off gas separated by the gas-liquid separator 400 is discharged, A second valve (V2) that controls the flow rate and opening and closing of the fluid may be installed on the line through which the liquefied gas separated by the separator 400 is discharged.

In addition, according to this embodiment, like the first embodiment, the boil-off gas separated by the gas-liquid separator 400 can be combined with the boil-off gas discharged from the storage tank (T) and used as a refrigerant in the heat exchanger (100). And, the liquefied gas separated by the gas-liquid separator 400 can be returned to the storage tank (T). The liquefied gas (point D2 in FIG. 2) returned to the storage tank (T) after being separated by the gas-liquid separator 400 may be -161°C and 6.7 bara.

The ship's fuel supply system of this embodiment, like the first embodiment, includes a pump 500 that pressurizes the liquefied gas inside the storage tank (T), and a vaporizer ( 600) may further be included.

Like the first embodiment, the pump 500 and the carburetor 600 of this embodiment liquefy the storage tank (T) when the evaporation gas inside the storage tank (T) does not satisfy the amount required by the engine. It vaporizes gas and supplies it to the engine. According to this embodiment, as in the first embodiment, instead of vaporizing and then compressing the liquefied gas, the liquefied gas is first compressed and then vaporized, so it is relatively inexpensive and easy to operate without using a compressor to pressurize the gas. It is economical because a low-cost pump (500) can be used.

On the line through which the liquefied gas discharged from the storage tank (T) passes through the pump 500 and the vaporizer 600 and is sent to the low-pressure engine or the high-pressure engine, as in the first embodiment, the pressure required by the low-pressure engine and the high-pressure engine And one or more of a pressure reducing device, a pressurizing device, and a heater may be installed to adjust the temperature conditions.

The present invention is not limited to the above-mentioned embodiments, and it is obvious to those skilled in the art that the present invention can be implemented with various modifications or variations without departing from the technical gist of the present invention. It was done.

T: Storage tank V1, V2: Valve
100: heat exchanger 200: multi-stage compression unit
210, 220: Compressor 300: Expansion means
400: gas-liquid separator 500: pump
600: vaporizer 800: heater
900: Additional compressor

Claims (20)

A storage tank for storing liquefied gas;
A multi-stage compression unit that compresses the boil-off gas discharged from the storage tank in multiple stages;
a heat exchanger that cools the boil-off gas discharged from the storage tank by heat-exchanging the boil-off gas compressed by the multi-stage compression unit with a refrigerant; and
It includes expansion means for expanding the fluid cooled by the heat exchanger,
The multi-stage compression unit consists of two stages: a first compressor and a second compressor,
Part or all of the boil-off gas compressed by the multi-stage compression unit is sent to the high-pressure engine, and surplus boil-off gas not used in the high-pressure engine among the boil-off gas compressed by the multi-stage compression unit is sent to the heat exchanger,
The high-pressure engine uses gas at 45°C and 300 bara as fuel,
A ship's fuel supply system, characterized in that the pressure of the boil-off gas discharged from the storage tank is 6.6 bara. In claim 1,
A fuel supply system for a ship, further comprising a gas-liquid separator installed at a rear end of the expansion means to separate the re-liquefied liquefied gas and the gaseous boil-off gas. In claim 1,
A pump that pressurizes the liquefied gas inside the storage tank; and
It further includes a vaporizer that vaporizes the liquefied gas pressurized by the pump,
The gas vaporized by the vaporizer is supplied as fuel for the high-pressure engine. In claim 2,
The fuel supply system of a ship wherein the boil-off gas separated by the gas-liquid separator is combined with the boil-off gas discharged from the storage tank and used as a refrigerant in the heat exchanger. The method according to any one of claims 1 to 4,
It further includes an additional compressor that compresses the boil-off gas discharged from the storage tank,
A ship's fuel supply system in which the boil-off gas compressed by the additional compressor is sent to the multi-stage compression unit. In claim 5,
The ship's fuel supply system where the boil-off gas compressed by the additional compressor is at 45°C and 6.5 bara. In claim 5,
A ship's fuel supply system in which the boil-off gas compressed by the additional compressor is partially branched and supplied to the low-pressure engine. The method according to any one of claims 1 to 4,
A ship's fuel supply system in which the boil-off gas compressed by the multi-stage compression unit and then sent to the heat exchanger is 43°C and 300 bara. In claim 5,
The additional compressor is a compressor that compresses fluid to a lower pressure than the first compressor and the second compressor. delete The method according to any one of claims 1 to 4,
The fuel supply system of a ship, wherein the storage tank is a Type C tank made of a component containing high manganese steel. In claim 2,
The gas-liquid separator is a ship's fuel supply system that stores fluid up to 6.7 bara and then discharges it. In claim 12,
The fuel supply system of a ship, wherein the gas-liquid separator is a Type C gas-liquid separator composed of a component containing high manganese steel. delete The method according to any one of claims 1 to 4,
A fuel supply system for a ship, further comprising a heater installed between the heat exchanger and the multi-stage compression unit. In claim 15,
A ship's fuel supply system in which a portion of the boil-off gas heated by the heater is branched and supplied to the low-pressure engine. In claim 15,
The ship's fuel supply system where the boil-off gas heated by the heater is at 45°C and 6.5 bara. delete delete delete

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