KR20230100810A - Fuel Supply System And Method For Ship - Google Patents

Abstract

A fuel supply system and method for a ship are disclosed. The ship's fuel supply system of the present invention includes a gas supply line for supplying boil-off gas generated from liquefied gas stored in a storage tank of the ship to a main engine in the ship; a multi-stage compressor provided in the gas supply line to compress boil-off gas to the fuel supply pressure of the main engine, and having a plurality of compressors and intercoolers alternately provided; a branch line branched off from the gas supply line and connected to a gas consumption point in the ship, and supplying boil-off gas compressed by the multi-stage compressor to the gas consumption point; a cooler bypass line provided to bypass the intermediate cooler of the last stage in the multi-stage compressor; and a cooler bypass valve provided in the cooler bypass line, characterized in that the temperature of the boil-off gas compressed through the multi-stage compressor can be adjusted through the cooler bypass line.

Description

Ship's fuel supply system and method {Fuel Supply System And Method For Ship}

The present invention relates to a fuel supply system and method for a ship, and more particularly, in a multi-stage compressor for compressing boil-off gas, a plurality of compressors and an intercooler are provided alternately to provide a cooler bypass line bypassing the intercooler of the last stage , It relates to a fuel supply system and method for ships capable of controlling the temperature of boil-off gas compressed in a multi-stage compressor.

Natural gas (natural gas) has methane (methane) as a main component, and there is little emission of environmental pollutants during combustion, so it is attracting attention as an eco-friendly fuel. Liquefied Natural Gas (LNG) is obtained by liquefying natural gas by cooling it to about -163°C under atmospheric pressure, and since its volume is reduced to about 1/600 of that in gaseous state, it is suitable for long-distance transportation through sea. very suitable Therefore, natural gas is mainly stored and transported in the form of liquefied natural gas, which is easy to store and transport.

Since the liquefaction point of natural gas is a cryogenic temperature of about -163 ° C. at atmospheric pressure, it is common for LNG storage tanks to be insulated so that LNG can remain in a liquid state. However, although the LNG storage tank is insulated, there is a limit to blocking external heat, and since external heat is continuously transferred to the LNG storage tank, LNG is continuously stored in the LNG storage tank during the LNG transportation process. It is vaporized and boil-off gas (BOG) is generated.

When boil-off gas is continuously generated in the LNG storage tank, it becomes a factor that increases the internal pressure of the LNG storage tank. If the internal pressure of the storage tank exceeds the set safety pressure, it may cause an emergency situation such as tank rupture, so the boil-off gas must be discharged to the outside of the storage tank using a safety valve. However, boil-off gas is a kind of LNG loss, and since it is an important problem in the transportation efficiency and fuel efficiency of LNG, various methods for treating boil-off gas generated in the storage tank are used.

Recently, a method of using boil-off gas at a fuel demand place such as a ship's engine, a method of re-liquefying boil-off gas and recovering it to a storage tank, or a method of using these two methods in combination have been developed and applied.

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

1 schematically illustrates a conventional fuel supply system for supplying boil-off gas generated in a storage tank as fuel for a main engine in a ship.

As shown in FIG. 1, a gas line GL is connected from the storage tank T to the main engine ME, and a compressor 10 for compressing boil-off gas for fuel supply to the main engine is provided in the gas line. .

Some of the evaporation gas compressed by the compressor may be branched and supplied to the power generation engine (GE) or the like, and when the fuel supply pressure of the power generation engine is lower, it may be reduced and supplied through the pressure reducing valve 20.

However, when the ME-GI engine is provided as the main engine, the boil-off gas compressed through the compressor 10 is around 45 ℃ at a pressure of around 300 barg. When the pressure is reduced to around or outside the barg, the temperature drops to about -50 ℃. Therefore, in order to meet the fuel supply conditions of the DFGE, it must be heated again to 0 to 60 ° C through the heater 30, and for such a heat energy supply, operating costs increase and incidental costs such as maintenance occur.

The present invention is to solve this problem and propose a fuel supply system capable of effectively supplying boil-off gas as fuel to main engines and power generation engines while lowering operating costs.

According to one aspect of the present invention for solving the above problems, the gas supply line for supplying the boil-off gas generated from the liquefied gas stored in the storage tank of the ship to the main engine in the ship;

a multi-stage compressor provided in the gas supply line to compress boil-off gas to the fuel supply pressure of the main engine, and having a plurality of compressors and intercoolers alternately provided;

a branch line branched off from the gas supply line and connected to a gas consumption point in the ship, and supplying boil-off gas compressed by the multi-stage compressor to the gas consumption point;

a cooler bypass line provided to bypass the intermediate cooler of the last stage in the multi-stage compressor; and

It includes a cooler bypass valve provided in the cooler bypass line,

There is provided a fuel supply system for a ship, characterized in that the temperature of the boil-off gas compressed through the multi-stage compressor can be adjusted through the cooler bypass line.

Preferably, a pressure reducing device provided in the branch line and reducing the boil-off gas compressed in the multi-stage compressor to a fuel supply pressure of the gas consumer may be further included.

Preferably, a gas heater provided downstream of the pressure reducing device in the branch line; a heater bypass line provided to bypass the gas heater; and a heater bypass valve provided in the heater bypass line.

Preferably, the fuel supply pressure of the main engine is 250 to 350 barg, and the gas consumption source may include a power generation engine and a boiler having a lower fuel supply pressure than the main engine.

Preferably, the liquefied gas is LNG, and the storage tank may be a Type C tank with a design pressure of 4 barg.

According to another aspect of the present invention, the boil-off gas generated from the liquefied gas stored in the storage tank of the ship is compressed to the fuel supply pressure of the main engine in the ship through a multi-stage compressor in which a plurality of compressors and an intercooler are alternately provided to the main engine. supply,

The boil-off gas compressed in the multi-stage compressor is branched and supplied to a gas consumption place in the ship,

There is provided a fuel supply method for a ship, characterized in that the temperature of the boil-off gas compressed through the multi-stage compressor can be adjusted by providing a cooler bypass line bypassing the intermediate cooler of the last stage in the multi-stage compressor.

Preferably, the gas consumer includes a power generation engine and a boiler having a lower fuel supply pressure than the main engine, and the boil-off gas to be supplied to the gas consumer is compressed through the multi-stage compressor and then passed through the cooler bypass line to the multi-stage compressor. The last stage of the intermediate cooler may be bypassed and the pressure may be reduced to the fuel supply pressure of the gas consumer through a pressure reducing device.

In the present invention, a cooler bypass line bypassing the intermediate cooler of the last stage in the multi-stage compressor is provided so that the temperature of the boil-off gas compressed through the multi-stage compressor can be adjusted. Through this, while supplying fuel to gas consumers such as power generation engines and boilers using a multi-stage compressor installed for fuel supply to the main engine, when supplying fuel to these gas consumers, after passing through the cooler bypass line, boil-off gas is discharged according to the fuel supply pressure. When depressurized, the decompressed gas can be supplied as fuel to the gas consumer without going through a separate heater, etc., reducing operating costs and preventing unnecessary energy loss, thereby reducing energy consumption on board.

In addition, since the system can be simplified without installing a separate heater, it is easy to arrange on board, and the number of equipment in the system can be reduced to reduce the number of maintenance and costs.

1 schematically shows a fuel supply system of a conventional ship.
2 schematically shows a fuel supply system for a ship according to an embodiment of the present invention.
3 schematically shows a fuel supply system for a vessel according to a modified embodiment of the present invention.

In order to fully understand the operational advantages of the present invention and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the configuration and operation of a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In adding reference numerals to the components of each drawing, it should be noted that the same components are marked with the same numerals as much as possible, even if they are displayed on different drawings.

Hereinafter, in the ship of the present invention, all types of engines that can use liquefied gas and boil-off gas generated from liquefied gas as fuel for engines for propulsion or power generation are installed or use liquefied gas or boil-off gas as fuel for inboard engines. of ships, typically LNG carriers, liquid hydrogen carriers, ships with self-propelled capabilities such as LNG RVs (Regasification Vessel), LNG FPSOs (Floating Production Storage Offloading), LNG FSRUs (Floating Storage Regasification Units) ) may also include offshore structures that do not have propulsion capability but are floating on the sea.

In addition, in the present invention, the liquefied gas can include all types of liquefied gas that can be transported by liquefying the gas at a low temperature, generate boil-off gas in a stored state, and can be used as fuel for engines and the like. These liquefied gases are, for example, liquefied petrochemicals such as LNG (Liquefied Natural Gas), LEG (Liquefied Ethane Gas), LPG (Liquefied Petroleum Gas), liquefied ethylene gas, and liquefied propylene gas. may be gas. However, in the embodiment to be described later, it will be described as an example in which LNG, which is one of representative liquefied gases, is applied.

Meanwhile, the fluid flowing through each line of the present embodiments may be in any one of a liquid state, a gas-liquid mixture state, a gas state, and a supercritical fluid state according to operating conditions of the system.

2 schematically shows a fuel supply system for a ship according to an embodiment of the present invention.

As shown in FIG. 2, the fuel supply system of this embodiment includes a gas supply line (GL) for supplying boil-off gas generated from liquefied gas stored in a storage tank (T) of a ship to a main engine (ME) in a ship, and the gas Provided in the supply line to compress the boil-off gas to the fuel supply pressure of the main engine, a plurality of compressors (110a, 110b, 110c, 110d, 110e) and intermediate coolers (120a, 120b, 120c, 120d, 120e) are provided alternately It includes a multi-stage compressor (100).

The branch line BL is branched from the gas supply line GL and connected to the inboard gas consumers GE and B, so that the boil-off gas compressed in the multi-stage compressor 100 can be supplied to the gas consumer. Gas consumers may include power generation engines with lower fuel supply pressure than the main engine, boilers, and GCUs.

The storage tank T may be, for example, a Type C tank with a design pressure of 4 barg. A pump P for transporting liquefied gas is provided in the storage tank so that the liquefied gas in the storage tank can be supplied as inboard fuel such as the main engine. In addition, a gas supply line GL is provided so that boil-off gas generated in the storage tank can be discharged and supplied as fuel to the main engine and gas consumers for processing.

The main engine (ME) is a main engine for ship propulsion that produces power for ship propulsion and delivers it to the ship's propeller. It can be the ME-GI engine of MAN-ES (company), which is a -stroke engine. Among the gas consumers where boil-off gas is supplied as fuel, a power generation engine (GE) is an engine that produces power required in a ship, for example, boil-off gas and diesel oil compressed to around 3 to 8 bar, more preferably 5.5 to 6.5 barg. It may be a DFGE (Duel Fuel Generator Engine), a 4-stroke engine supplied with fuel. Boiler B) is a device for generating steam required in a ship, and may be, for example, a dual fuel boiler supplied with boil-off gas and diesel oil as fuel.

The multi-stage compressor 100 receives the boil-off gas discharged from the storage tank through the gas supply line GL, and includes, for example, five compressors 110a, 110b, 110c, 110d, and 110e and five intercoolers 120a, 120b, 120c, 120d, 120e) compresses the boil-off gas to the fuel supply pressure of the main engine through five stages of compression and intermediate cooling processes alternately provided. Boiled gas compressed through some of the multi-stage compressors may be supplied as fuel in accordance with the pressure conditions required for the gas consumer on board, or the boil-off gas compressed through all of the compressors of the multi-stage compressor may be reduced and supplied to the gas consumer.

To this end, a pressure reducing device 200 for reducing the boil-off gas compressed in the multi-stage compressor to a fuel supply pressure of a gas consumer is provided in the branch line BL. The decompression device may be, for example, a Joule-Thomson valve or an expander that expands and depressurizes the compressed boil-off gas.

However, the boil-off gas compressed through the multi-stage compressor is around 45 ℃ at a pressure of around 300 barg, and when the pressure is reduced to around 6.5 barg in the pressure reducing device according to the DFGE fuel supply pressure, the temperature drops to about -50 ℃, which is used as the fuel of DFGE. In order to meet the supply conditions, heat energy is supplied again to the boil-off gas intermediately cooled in the multi-stage compressor to heat it to 0 to 60 ° C., so there is a problem in that energy is wasted twice.

In this embodiment, in order to solve this problem, a cooler bypass line (CBL) capable of bypassing the last stage intermediate cooler 120e in the multi-stage compressor and a cooler bypass valve (CBV) installed in the cooler bypass line are provided, so that the multi-stage compressor The temperature of the compressed boil-off gas can be controlled through the

In this way, when the intermediate cooler 120e of the last stage is bypassed through the cooler bypass line (CBL), the boil-off gas compressed through the multi-stage compressor 100 is discharged with the temperature rising to around 300 barg and 90 ° C. By sending it to the branch line (BL) and reducing the pressure in the pressure reducing device 200, the temperature above room temperature can be maintained after the pressure reduction, so that the fuel supply conditions of gas consumers such as power generation engines and boilers can be met without additional heating. Therefore, it is possible to eliminate the heater installed to supply boil-off gas to the power generation engine and boiler by utilizing the conventional multi-stage compressor prepared for fuel supply to the main engine, thereby reducing the configuration of devices in the fuel supply system and reducing installation costs and fuel supply system It can reduce the waste of energy and reduce the operating cost of the ship.

By adjusting the opening and closing of the cooler bypass valve (CBV) installed in the cooler bypass line (CBL) to adjust the flow rate of boil-off gas passing through the cooler bypass line, the temperature of the boil-off gas discharged through the multi-stage compressor can be adjusted as needed. .

On the other hand, FIG. 3 shows a fuel supply system of a modified embodiment in which the system of the above-described embodiment is modified.

Compared to the heater of the branch line connected to the gas consumption point in the system of the above-mentioned embodiment, in this modified embodiment, the gas heater 300 for heating the boil-off gas is left as it is at the downstream of the decompression device of the branch line as in the prior art, A heater bypass line (HBL) and a heater bypass valve (HBV) that bypass the heater are additionally provided.

In this way, a heater bypass line (HBL) and a heater bypass valve (HBV) are additionally provided along with a cooler bypass line (CBL) and a cooler bypass valve (CBV) that bypass the intermediate cooler (120e) of the last stage of the multi-stage compressor, When supplying boil-off gas to gas consumers such as power generation engines and boilers, boil-off gas can be supplied to gas consumers while reducing energy use as described above through a cooler bypass line (CBL) and a heater bypass line (HBL). In addition, when the boil-off gas compressed by the multi-stage compressor 100 is simultaneously supplied to the main engine (ME) and gas consumers (GE, B), the cooler bypass valve (CBV) is closed and the boil-off gas is compressed through the last stage compressor and the intercooler. After being supplied as fuel to the main engine (ME), the boil-off gas branched to the branch line (BL) can be heated according to the fuel supply conditions of the gas consumers (GE, B) through the gas heater 300 after depressurization.

As such, the modified embodiment does not eliminate the gas heater, so it is not possible to reduce the device configuration cost, but it is possible to reduce energy consumption and increase the flexibility of system operation.

It is obvious to those skilled in the art that the present invention is not limited to the above embodiments and can be variously modified or modified without departing from the technical gist of the present invention. it did

T: storage tank
ME: main engine
GE: Power generation engine
B: Boiler
GL: gas supply line
BL: branch line
CBL: Cooler bypass line
CBV: Chiller bypass valve
100: multi-stage compressor
110a, 110b, 110c, 110d, 110e: compressor
120a, 120b, 120d, 120d, 120e: intercooler
200: decompression device

Claims (7)

A gas supply line for supplying evaporation gas generated from liquefied gas stored in the storage tank of the ship to the main engine in the ship;
a multi-stage compressor provided in the gas supply line to compress boil-off gas to the fuel supply pressure of the main engine, and having a plurality of compressors and intercoolers alternately provided;
a branch line branched off from the gas supply line and connected to a gas consumption point onboard, and supplying boil-off gas compressed by the multi-stage compressor to the gas consumption point;
a cooler bypass line provided to bypass the intermediate cooler of the last stage in the multi-stage compressor; and
It includes a cooler bypass valve provided in the cooler bypass line,
A fuel supply system for a ship, characterized in that the temperature of the boil-off gas compressed through the multi-stage compressor can be adjusted through the cooler bypass line. According to claim 1,
The ship's fuel supply system further comprising: a decompression device provided in the branch line and reducing the boil-off gas compressed in the multi-stage compressor to a fuel supply pressure of the gas consumption point. According to claim 2,
a gas heater provided downstream of the pressure reducing device in the branch line;
a heater bypass line provided to bypass the gas heater; and
A heater bypass valve provided in the heater bypass line: Ship's fuel supply system further comprising a. According to any one of claims 1 to 3,
The fuel supply pressure of the main engine is 250 to 350 barg,
The gas consumption point includes a power generation engine and a boiler having a lower fuel supply pressure than the main engine. According to claim 4,
The liquefied gas is LNG,
The storage tank is a fuel supply system for a ship, characterized in that the Type C tank with a design pressure of 4 barg. The boil-off gas generated from the liquefied gas stored in the storage tank of the ship is compressed to the fuel supply pressure of the main engine in the ship through a multi-stage compressor in which a plurality of compressors and an intercooler are alternately provided, and supplied to the main engine,
The boil-off gas compressed in the multi-stage compressor is branched and supplied to a gas consumption place in the ship,
A method for supplying fuel to a ship, characterized in that the temperature of the boil-off gas compressed through the multi-stage compressor can be adjusted by providing a cooler bypass line bypassing the intermediate cooler of the last stage in the multi-stage compressor. According to claim 6,
The gas consumption source includes a power generation engine and a boiler having a lower fuel supply pressure than the main engine,
The boil-off gas to be supplied to the gas consumer is compressed through the multi-stage compressor, bypasses the intermediate cooler of the last stage of the multi-stage compressor through the cooler bypass line, and is reduced to the fuel supply pressure of the gas consumer through a pressure reducing device. How to supply fuel to a ship.

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