KR102538933B1 - Fuel Supplying System And Method For Ship Using Liquefied Gas - Google Patents

Abstract

A fuel supply system and method for a liquefied gas propulsion ship are disclosed. A fuel supply system for a liquefied gas propulsion ship of the present invention includes a fuel storage tank provided in the ship and storing liquefied gas to be supplied to an engine in the ship; a fuel supply line through which the liquefied gas is supplied from the fuel storage tank to the engine; a return line connected to the fuel storage tank from the engine to recirculate the liquefied gas; a separator provided in the return line to separate gas-liquid from the liquefied gas being recycled; and a gas processing line branched off from the return line to supply the gas separated by the separator to the BOG processing means, wherein the pressure of the separator is controlled to a required pressure in the BOG processing means.

Description

Fuel Supply System And Method For Ship Using Liquefied Gas

The present invention relates to a fuel supply system and method for a liquefied gas propulsion ship, and more particularly, to supply liquefied gas to an engine along a fuel supply line from a fuel storage tank provided on a ship and storing liquefied gas to be supplied to an engine in a ship, A separator is provided on the return line that recirculates the liquefied gas from the downstream of the engine to the fuel storage tank, and among the recirculated liquefied gas, only the liquid separated from the separator is supplied to the fuel storage tank, and the gas separated from the separator passes through the gas processing line. It relates to a fuel supply system and method for a liquefied gas propulsion ship, characterized in that the pressure of the separator is controlled to the required pressure in the BOG processing means while supplying it to the BOG processing means in the ship through the.

Consumption of liquefied gases such as LNG (Liquefied Natural Gas) and LPG (Liquefied Petroleum Gas) is rapidly increasing worldwide. Liquefied gas is transported in a gaseous state through onshore or offshore gas pipelines, or transported to a distant consumer while being stored in a liquefied gas carrier in a liquefied state. Liquefied gas, such as LNG or LPG, is obtained by cooling natural gas or petroleum gas to a cryogenic temperature (approximately -163 ° C in the case of LNG), and its volume is significantly reduced compared to the gas state, so it is very suitable for long-distance transportation through sea.

The liquefaction temperature of petroleum gas is at a low temperature of about -42 ° C under atmospheric pressure, and since LPG evaporates when the atmospheric pressure is higher than -42 ° C, the LPG storage tank of the ship is insulated. However, since external heat is continuously transferred to the LPG, the LPG is continuously vaporized in the LPG storage tank during the transport process of the LPG, and boil-off gas is generated in the LPG storage tank.

In conventional LPG carriers, when boil-off gas accumulates in the LPG storage tank, the pressure inside the LPG storage tank rises excessively. used

However, if a boil-off gas re-liquefaction device composed of a suction pump, a reciprocating compressor, a cooler, a condenser, an expansion valve, etc. is used to condense and re-liquefy the boil-off gas, a lot of power is consumed and the operating cost increases, and the initial facility investment cost increases, Since a large device must be installed in a limited space of a ship, it is difficult to secure space in the ship.

On the other hand, conventional LPG carriers adopt a fuel supply system using heavy oil such as bunker C oil, which is relatively inexpensive as a propulsion fuel for ships. Due to stricter regulations, a separate heavy fuel oil fuel tank (LSHFO tank) with low sulfur content had to be installed, and the demand for an eco-friendly fuel supply system that meets international environmental regulatory standards has increased.

In recent years, the application of fuel supply systems that use LPG or LNG and boil-off gas generated from them as propulsion fuel in LPG or LNG carriers is increasing, and in accordance with the strengthening of international exhaust gas emission regulations, general ships in addition to LPG or LNG carriers are also using LNG. Ships using it as a propulsion fuel are increasing.

An example of a conventional fuel supply system for a ship using LPG as a propulsion fuel is schematically shown in FIG.

As shown in FIG. 1, LPG to be supplied as fuel to the engine 40 passes through the pump 20 and the heat exchanger 30 from the fuel storage tank 10 through the fuel supply line L1 as fuel for the engine. It is supplied to the ship's engine according to the supply conditions.

On the other hand, when it is necessary to prevent the supply pressure from falling due to excessive supply or a change in fuel consumption rate according to a change in engine load, some of the supplied LPG is recirculated to the fuel storage tank, and LPG is passed through the return line (L2) from the engine. It can be assumed that a part is supplied to the fuel storage tank 10 .

The present inventors have considered the increase in internal pressure of the fuel storage tank due to boil-off gas generated from LPG in this fuel supply system, the flashing of LPG fuel recirculated through the return line, and the flashing due to heat generated according to the use of the pump. I found that I had to design it.

In particular, when the pressure of the fuel storage tank is low, the pressure of the recirculated LPG drops rapidly and a large amount of gas is generated through flashing. In one case, the inventors have found that 45% of the recycled LPG is flashed, which can cause an increase in tank capacity.

The present invention is to solve this problem and to provide a fuel supply system capable of effectively treating liquefied gas that is recycled while reducing the capacity of a fuel storage tank.

According to one aspect of the present invention for solving the above problems, a fuel storage tank provided in a ship and storing liquefied gas to be supplied to an engine on board;

a fuel supply line through which the liquefied gas is supplied from the fuel storage tank to the engine;

a return line connected to the fuel storage tank from the engine to recirculate the liquefied gas;

a separator provided in the return line to separate gas-liquid from the liquefied gas being recycled; and

A gas processing line branched from the return line and supplying the gas separated in the separator to a BOG processing means;

The pressure of the separator is provided with a fuel supply system for a liquefied gas propulsion vessel, characterized in that controlled to the required pressure in the BOG processing means.

Preferably, a pressure control valve provided in the gas processing line; further comprising, wherein the BOG processing means includes a re-liquefaction device for re-liquefying BOG generated in the ship by compressing and cooling it, and the pressure control valve is In the reliquefaction device, the pressure of the separator may be adjusted to be 0.1 to 3 bar higher than the pressure downstream of the compressor for compressing the BOG.

Preferably, a pressure sensor for sensing the pressure of BOG may be provided downstream of the compressor of the re-liquefaction device.

Preferably, a control valve provided upstream of the separator in the return line controls the pressure of the liquefied gas introduced into the separator; a level sensor that detects a water level of the separator; and a water level control valve provided downstream of the separator in the return line. may further include.

Preferably, the water level control valve is opened and closed by the water level of the separator detected by the level sensor, so that the water level inside the separator can be adjusted.

Preferably, the fuel supply line includes a pump for compressing the liquefied gas supplied from the fuel storage tank to a fuel supply pressure required by the engine; and a heat exchanger for heating the liquefied gas compressed by the pump. can be provided.

According to another aspect of the present invention, supplying the liquefied gas to the engine along the fuel supply line from a fuel storage tank for storing the liquefied gas to be supplied to the onboard engine provided in the ship,

A separator for gas-liquid separation of the liquefied gas is provided in a return line through which the liquefied gas is recirculated from downstream of the engine to the fuel storage tank, and only the liquid separated by the separator among the recirculated liquefied gas is supplied to the fuel storage tank. And, the gas separated from the separator is supplied to the BOG processing means in the ship through the gas processing line, and the pressure of the separator is controlled by the required pressure in the BOG processing means Fuel supply method for a liquefied gas propulsion ship is provided.

The present invention provides a separator in the return line through which liquefied gas is recirculated from the engine to the fuel storage tank, transfers only the liquid to the fuel storage tank and recirculates it, thereby reducing the capacity of the fuel storage tank to reduce installation costs and to secure space in the ship. contribute

In particular, by controlling the pressure of the separator to the required pressure in the BOG processing means, the gas separated from the separator can be transferred to the re-liquefaction device of the BOG processing means and re-liquefied and processed immediately without additional compression, thereby reducing recycled liquefied gas. can be processed efficiently.

1 schematically shows an example of a conventional fuel supply system for a ship using LPG as a propulsion fuel.
Figure 2 schematically shows a fuel supply system for a liquefied gas propulsion vessel according to an 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.

In an embodiment of the present invention to be described later, the ship may be any type of ship using liquefied gas as fuel or an engine capable of using liquefied gas as a fuel for a propulsion engine or a power generation engine. Typically, ships with self-propelled capabilities such as LPG carriers, LNG carriers, liquid hydrogen carriers, and LNG RVs (Regasification Vessel), LNG FPSOs (Floating Production Storage Offloading), LNG FSRUs (Floating Storage Regasification Units) Offshore structures that do not have propulsion capability, but are floating on the sea, can also be included. However, in an embodiment to be described later, a liquefied gas carrier will be described as an example.

In addition, the present embodiment can be applied to a fuel supply system for 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 supplied as engine fuel. 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 embodiments to be described later, an example in which LPG, which is one of representative liquefied gases, is applied will be described.

Figure 2 schematically shows a fuel supply system for a liquefied gas propulsion vessel according to an embodiment of the present invention.

As shown in FIG. 2, the system of this embodiment is provided in a ship, a fuel storage tank (T) for storing liquefied gas to be supplied to the engine (E) on board, and a fuel supply line for supplying liquefied gas from the fuel storage tank to the engine. (FL), a return line (RL) connected from the engine to the fuel storage tank to recirculate liquefied gas, a separator 100 provided in the return line for gas-liquid separation of the liquefied gas being recycled, and a gas branched from the return line and separated from the separator It includes a gas treatment line (GL) for supplying to the BOG processing means (200).

The fuel supply line FL is provided with a pump 300 for compressing liquefied gas supplied from the fuel storage tank to a fuel supply pressure required by the engine, and a heat exchanger 400 for heating the liquefied gas compressed by the pump.

When liquefied gas is supplied to the engine in excess or when the fuel consumption rate changes according to the load of the engine and the fuel supply pressure must be prevented from falling, some of the liquefied gas supplied to the engine is supplied through the return line. It can be recycled by supplying it to the fuel storage tank.

In this embodiment, the engine is supplied with liquefied gas as fuel, and may be, for example, a Dual Fuel Engine or a MAN D&T ME-LGIP engine that receives LPG and diesel as fuel. Liquefied gas can be supplied to the engine through a high-pressure pump and heat exchanger at the temperature and pressure necessary for the engine, for example, 50 bar, 30 to 55 ° C in the case of a dual fuel engine supplied with LPG and diesel as fuel, and in this case, the return The temperature and pressure of the liquefied gas recirculated to the fuel storage tank through the line may be about 45 bar and 60°C. The recirculated liquefied gas is reduced in temperature and reduced in pressure while passing through devices such as valves and separators, and is supplied to the fuel storage tank.

The fuel storage tank (T) for storing liquefied gas may be installed on the top or bottom of the deck of the ship. When installed on the top of the deck, the pressure inside the tank may change according to the change in atmospheric temperature, It can be provided with a tank that can withstand it, for example, it can be a type-C tank.

In this embodiment, the pressure of the separator is characterized in that it is controlled by the necessary pressure in the BOG processing unit. The BOG processing means 200 may be, for example, a re-liquefying device that compresses and cools BOG generated in a ship to re-liquefy it.

The re-liquefaction device may include a compressor composed of multi-stage BOG compressors to compress BOG and a heat exchanger or a cooler using seawater to cool the compressed BOG.

A pressure sensor 250 for detecting the pressure of BOG is provided downstream of the compressor of the re-liquefaction device, and a pressure control valve V1 is provided in the gas processing line GL.

Based on the pressure detected by the pressure sensor, the pressure regulating valve sets the pressure of the separator slightly higher than the pressure downstream of the compressor for compressing BOG in the reliquefaction device, more specifically, 0.1 to 3 bar, more preferably 0.5 to 2 bar. Adjust the bar to a higher level.

2 shows an example of a re-liquefaction apparatus including a compressor including a three-stage BOG compressor. In the re-liquefaction apparatus shown in FIG. 2, a pressure sensor 250 is provided downstream of the compressor to detect the pressure of the BOG compressed through the 3-stage BOG compressor, and controls the pressure control valve V1 based on the value to obtain a separator Adjust the pressure to 100. By adjusting the pressure of the separator slightly higher than the pressure downstream of the three-stage BOG compressor, the gas separated from the separator can be directly supplied downstream of the three-stage BOG compressor. Therefore, by supplying the gas separated from the separator to the downstream of the compressor according to the compression pressure of the BOG in the re-liquefaction device without going through the compressor, it can be re-liquefied directly with only heat exchange, and the compressor drive can be reduced, reducing operating costs and efficiently gas can be treated.

Among the recycled liquefied gas, the gas in the separator is transferred to the re-liquefaction device for treatment, and only the separated liquid is transferred to the fuel storage tank, so the amount of liquefied gas recirculated can be reduced and the capacity of the fuel storage tank can be reduced. As a result, the cost of installing the system can be reduced, and it can also contribute to securing space in the ship.

For example, in the case of a Dual Fuel Engine, if it is liquefied gas of pure propane, the pressure of the fuel storage tank is 1 bara, and the amount of recirculated fuel is 200 kg/hr, the liquefied gas is supplied to the engine at 50 bar and 30 to 55 ° C. , the temperature and pressure of the liquefied gas recirculated to the fuel storage tank through the return line are about 45 bar and 60 °C. In the re-liquefaction device, the compressed BOG is cooled using seawater, and if the temperature of the seawater is 5℃, the BOG pressure detected by the pressure sensor downstream of the compressor is around 6.8 bar and the pressure control valve controls the pressure of the separator to around 7.8 bar. . The gas fraction of the liquefied gas recirculated from the engine through the return line is 0.12, and in the separator, the liquefied gas is gas-liquid separated, and the separated gas is transported downstream of the compressor and cooled with seawater to be re-liquefied. Since only the liquid separated from the separator is transferred to the fuel storage tank, the volume reduction rate of the fuel recycled to the fuel storage tank is reduced to 80.3% compared to the prior art. Under the same conditions, when the seawater temperature is 36℃, the BOG pressure downstream of the compressor is around 15.2 bar and the pressure in the separator is controlled around 16.2 bar by the pressure control valve. is 0.024, the volume reduction rate of the fuel recycled to the fuel storage tank is 58.4% compared to the prior art.

On the other hand, in the return line (RL), a control valve (V2) for controlling the pressure of the liquefied gas introduced into the separator is provided upstream of the separator, and a water level control valve (V3) is provided downstream, respectively, to detect the level of the separator. A level sensor 500 is provided.

The water level control valve is opened and closed by the water level of the separator detected by the level sensor, so that the water level inside the separator can be adjusted.

As described above, the fuel supply system of the present embodiment provides a separator in the return line, controls the pressure of the separator to the required pressure in the BOG processing means, and transfers the gas separated from the separator to the re-liquefaction device of the BOG processing means It can be re-liquefied and processed immediately without the need for additional pressure, and only the liquid can be transferred to the fuel storage tank and recycled, so that the liquefied gas that is recycled can be efficiently treated while reducing the capacity of the fuel storage tank.

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: fuel storage tank
E: engine
FL: fuel supply line
RL: return line
GL: gas processing line
100: separator
200: BOG processing means
250: pressure sensor
300: pump
400: heat exchanger
500: level sensor
V1: Pressure regulating valve
V2: control valve
V3: Water level control valve

Claims (7)

A fuel storage tank provided in the ship and storing liquefied gas to be supplied to the ship's engine;
a fuel supply line through which the liquefied gas is supplied from the fuel storage tank to the engine;
a return line connected to the fuel storage tank from the engine to recirculate the liquefied gas;
a separator provided in the return line to separate gas-liquid from the liquefied gas being recycled;
a gas processing line branched off from the return line and supplying the gas separated from the separator to a BOG processing means; and
It includes a pressure control valve provided in the gas treatment line,
The BOG processing means includes a re-liquefying device that compresses and cools the BOG generated in the ship to re-liquefy, and the pressure control valve has a pressure 0.1 to 3 bar higher than a downstream pressure of a compressor for compressing the BOG in the re-liquefying device. Adjust the pressure of the separator,
The fuel supply system for a liquefied gas propulsion vessel, characterized in that the gas separated in the separator is supplied downstream of the compressor. delete According to claim 1,
A fuel supply system for a liquefied gas propulsion vessel, characterized in that a pressure sensor for detecting the pressure of the BOG is provided downstream of the compressor of the re-liquefaction device. According to claim 3,
a control valve provided upstream of the separator in the return line to control the pressure of the liquefied gas introduced into the separator;
a level sensor that detects a water level of the separator; and
a water level control valve provided downstream of the separator in the return line; A fuel supply system for a liquefied gas propulsion vessel further comprising a. According to claim 4,
The fuel supply system of a liquefied gas propulsion vessel, characterized in that the water level control valve is opened and closed by the water level of the separator detected by the level sensor to adjust the water level inside the separator. The method of claim 1, wherein the fuel supply line
a pump for compressing the liquefied gas supplied from the fuel storage tank to a fuel supply pressure required by the engine; and
a heat exchanger for heating the liquefied gas compressed by the pump; A fuel supply system for a liquefied gas propulsion vessel, characterized in that provided. Supplying the liquefied gas to the engine along a fuel supply line from a fuel storage tank provided in the ship and storing liquefied gas to be supplied to the engine on board,
A separator for gas-liquid separation of the liquefied gas is provided in a return line that recirculates the liquefied gas from downstream of the engine to the fuel storage tank, and only the liquid separated by the separator among the recirculated liquefied gas is supplied to the fuel storage tank. And, the gas separated from the separator is supplied to the BOG processing means in the ship through the gas processing line,
The BOG processing means includes a re-liquefying device that compresses and cools the BOG generated in the ship to re-liquefy, and the pressure downstream of the compressor for compressing the BOG in the re-liquefying device by a pressure control valve provided in the gas processing line A fuel supply method for a liquefied gas propulsion vessel, characterized in that the pressure of the separator is adjusted to be higher than 0.1 to 3 bar, and the gas separated from the separator is supplied downstream of the compressor.

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