KR20230087680A - Fuel Supply System And Method For Ship - Google Patents

Abstract

A fuel supply system and method for a ship are disclosed. A fuel supply system for a ship of the present invention includes a fuel supply line for supplying liquefied gas from a fuel supply tank provided in the ship to an engine in the ship; a compression unit provided in the fuel supply line and compressing the liquefied gas to a pressure required for the engine; a return line for recovering liquefied gas not consumed by the engine among the liquefied gas supplied to the engine from the engine; a gas-liquid separator provided in the return line and separating gas-liquid fuel recovered from the engine; and a liquid line for supplying the liquefied gas in a liquid state separated by the gas-liquid separator to the front end of the compression unit of the fuel supply line, wherein the liquefied gas is supplied to the engine in a liquid state.

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, to supply liquefied gas in a liquid state from a fuel supply tank to an engine, recover liquefied gas not consumed by the engine from the engine, and operate a gas-liquid separator. It relates to a fuel supply system and method for a ship that supplies liquefied gas in a liquid state to the front end of a compression part of a fuel supply line.

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 low at atmospheric pressure of about -42 ° C, and it can be stored in a liquid state up to a temperature of about 45 ° C at 18 bar and 20 ° C at 7 bar. Since LPG evaporates when the normal pressure is higher than -42℃, the ship's LPG storage tank 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 LPG carriers, when boil-off gas accumulates in the LPG storage tank, the pressure inside the LPG storage tank rises excessively. Therefore, the LPG storage tank has a pressure-resistant structure and a boil-off gas re-liquefaction device is used to treat the boil-off gas generated in the tank. do.

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.

In particular, LPG is easier to store than LNG, which is liquefied at cryogenic temperatures, and does not fall significantly in SPECIFIC ENERGY and ENERGY DENSITY compared to existing HFO, and has excellent effects in reducing SOX, NOX, CO2, PM, etc. compared to existing HFO.

In ships using LPG as fuel, LPG to be supplied as fuel to the engine is supplied to the engine of the ship according to the fuel supply conditions of the engine through the fuel supply system including the compression pump and heater from the fuel supply tank. are supplied

LPG, an incompressible fluid, can be supplied in excess of the fuel required by the engine so that it can respond immediately to changes in engine load. When stopped, LPG remaining in the engine and pipes is recovered upstream of the engine.

However, if the recovered LPG is discharged into the air as it is, there is a problem of wasting fuel and causing environmental pollution, and if it is sent to a cargo tank, there is a risk of contamination of the LPG cargo and lubricating oil freezing due to sealing oil introduced from the engine. In addition, since the LPG recovered from the engine is pressurized and heated according to the fuel supply conditions of the engine and is in a high-temperature and high-pressure state, there is a problem of increasing the pressure in the tank by increasing the amount of BOG generated when it is sent to the fuel supply tank.

The present invention solves this problem, and aims to provide a system capable of effectively supplying fuel while effectively treating LPG recovered from an engine.

According to one aspect of the present invention for solving the above problems, a fuel supply line for supplying liquefied gas from a fuel supply tank provided in a ship to an inboard engine;

a compression unit provided in the fuel supply line and compressing the liquefied gas to a pressure required for the engine;

a return line for recovering liquefied gas not consumed by the engine among the liquefied gas supplied to the engine from the engine;

a gas-liquid separator provided in the return line and separating gas-liquid fuel recovered from the engine; and

A liquid line for supplying the liquefied gas in the liquid state separated in the gas-liquid separator to the front end of the compression part of the fuel supply line;

There is provided a fuel supply system for a ship, characterized in that the liquefied gas is supplied to the engine in a liquid state.

Preferably, the gas-liquid separator can separate and remove lubricating oil mixed in the fuel recovered from the engine.

Preferably, the compression unit includes a transfer pump for transferring liquefied gas to be supplied to the engine from the fuel supply tank; and a compression pump for boosting the liquefied gas transferred from the transfer pump to a pressure required for the engine.

Preferably, a first valve opening and closing the liquid line; a liquid level sensor for detecting a liquid gas level in the gas-liquid separator; and a liquid level controller controlling the first valve by the level of the liquefied gas detected by the liquid level sensor.

Preferably, a check valve provided between the junction of the liquid line and the fuel supply tank in the fuel supply line may further include.

Preferably, a gas discharge line for transferring the gas separated in the gas-liquid separator to the fuel supply tank; and a second valve opening and closing the gas discharge line.

Preferably, a pressure sensor for sensing the pressure of the gas-liquid separator; and a pressure controller configured to control the second valve based on the pressure sensed by the pressure sensor, wherein the pressure controller adjusts the opening of the second valve according to the pressure sensed by the pressure sensor, so that the gas-liquid The pressure of the separator may be maintained higher than the pressure of the fuel supply tank.

Preferably, a heat exchanger provided downstream of the compression pump in the fuel supply line to heat liquefied gas to be supplied to the engine; and a decompression unit provided upstream of the gas-liquid separator in the return line to depressurize the liquefied gas recovered from the engine.

According to another aspect of the present invention, liquefied gas is transported from a fuel supply tank provided in a ship, compressed through a compression unit, and supplied as fuel in a liquid state to an engine in a ship,

The liquefied gas not consumed in the engine is recovered by the gas-liquid separator to separate gas and lubricating oil, and the liquefied gas in liquid state separated in the gas-liquid separator is transferred to the front end of the compression unit and recycled,

There is provided a fuel supply method for a ship, characterized in that the pressure of the gas-liquid separator is maintained higher than the pressure of the fuel supply tank while discharging the gas separated in the gas-liquid separator to the fuel supply tank.

In the present invention, among the liquefied gas supplied as fuel to the engine, liquefied gas not consumed by the engine is recovered through the return line, but a gas-liquid separator is provided in the return line to separate the liquefied gas recovered through the return line, Only the liquefied gas is recirculated to the front of the compression part of the fuel supply line.

In this way, by filtering and recirculating the liquefied gas remaining after being consumed as fuel in the engine through a gas-liquid separator, mixing of lubricating oil in the fuel is prevented, thereby preventing incomplete combustion of the engine and consequent generation of pollutants in the exhaust. It can prevent LPG contamination and crystallization of lubricating oil in the fuel supply tank due to sealing oil.

In addition, by recirculating the liquefied gas recovered from the engine to the front of the transfer pump and the compression pump, the gas-liquid separator is not directly affected by the change in the discharge pressure of the transfer pump and the compression pump caused by the load change of the engine, so the engine or fuel supply process Even if an emergency stop occurs, the fuel supply system can be operated more stably by controlling the pressure of the gas-liquid separator, and it is easy to return to normal operation.

1 schematically shows a fuel supply system according to a basic embodiment of a ship supplying liquefied gas such as LPG as engine fuel.
Figure 2 schematically shows a fuel supply system for a vessel according to an embodiment of the present invention improved on the basic embodiment.

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 vessel may be any type of vessel in which an engine capable of using liquefied petroleum gas as a fuel for a propulsion engine or a fuel for a power generation engine is installed. 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.

In addition, this embodiment can be liquefied at a low temperature and transported, boil-off gas is generated in a stored state, and can be applied to a fuel supply system for all types of liquefied gas that 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. gas and ammonia, and the like. 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.

1 schematically shows a fuel supply system according to a basic embodiment of a ship supplying liquefied gas such as LPG as engine fuel.

As shown in FIG. 1, the fuel supply system of a ship receiving LPG as fuel is provided in a fuel supply line (SL) through which liquefied gas is supplied to the inboard engine (E) and a fuel supply line, and is provided from the fuel supply tank to the engine A transfer pump 100 for transferring liquefied gas to be supplied to, a compression pump 110 provided in a fuel supply line and compressing liquefied gas to a pressure required for the engine, recovering liquefied gas that is not consumed by the engine among liquefied gas from the engine It includes a return line (RL) and a gas-liquid separator 200 provided in the return line and receiving the liquefied gas to be recycled and separating the gas-liquid.

The liquefied gas stored in the fuel supply tank (T) is transferred through the transfer pump 100, compressed to the fuel supply pressure of the engine through the compression pump 110, and then discharged from the engine through the heat exchanger 120 or fuel heater. After being heated to the required temperature, it is supplied to the engine.

A filter (not shown) and a service valve (not shown) may be further provided in the fuel supply line to filter out foreign substances in the compressed and heated liquefied gas through a compression unit and a heat exchanger. In the service valve part, while supplying LPG to the engine, when the supply of LPG fuel is stopped due to engine switching to fuel oil, LPG mode stop, trip, etc., each pipe is double-blocked through the valve to relieve pressure in the pipe.

An engine receiving such compressed and heated LPG as fuel may be, for example, a MAN Diesel & Turbo ME-LGIP engine. In this case, LPG is supplied to the engine in a high-pressure liquid state of around 54 bar and 35 ° C through a compression unit and a heat exchanger, and is injected into a nozzle at a pressure of 600 to 700 bar hydraulically from the engine to operate the engine.

That is, in the engine of this embodiment, compressed and heated fuel is supplied to the engine in a liquid state. Unlike engines supplied with a compressible fluid having a large volume change according to pressure change, that is, gas fuel, the volume changes even when pressure is applied When liquid LPG, an incompressible fluid with little or no incompressible fluid, is supplied as engine fuel, sufficient fuel is supplied to respond immediately to changes in the load of the engine, and excess LPG is supplied to the engine to prevent cavitation. Of the LPG supplied to the engine, the remaining LPG is discharged from the engine through the return line (RL) and recycled as fuel. As a result, there is a risk of LPG contamination in the fuel supply tank, and when supplied as fuel, incomplete combustion may generate atmospheric pollutants in the exhaust and adversely affect fuel efficiency. In addition to liquid LPG, the recovered liquefied gas also includes gases such as evaporation gas generated through compression and heating for fuel supply, which also causes equipment failure in the compression unit or increases the pressure and temperature in the fuel supply tank. This can pose a threat to tank and ship safety.

Therefore, the gas/liquid separator 200 is provided in the return line RL of the fuel supply system to separate gas/liquid/lubricating oil from the liquefied gas recovered from the engine to recirculate the liquefied gas in liquid state and separate and remove the lubricating oil . Separation of the lubricating oil may be performed using, for example, a difference in specific gravity of each component in fuel recovered from an engine. The main components of LPG are propane (C ₃ H ₈ ) and butane (C ₄ H ₁₀ ). Although there are differences depending on the ratio of propane and butane, the specific gravity is about 0.5, and the specific gravity of lubricating oil is about 0.9. Therefore, in the gas-liquid separator, the gas is separated at the top, and the lubricating oil heavier than LPG is layered at the bottom due to the difference in specific gravity, so that the layered lubricating oil can be discharged through a pipe at the bottom of the gas-liquid separator. By adjusting the viscosity of the fuel by adjusting the pressure of the gas-liquid separator, the lubricating oil can be separated and discharged more easily by the difference in viscosity and specific gravity.

A pressure reducing device (not shown) such as an expansion valve for reducing and cooling the liquefied gas to be recovered by the gas-liquid separator may be additionally provided in the return line RL, if necessary.

In this way, the liquefied gas in liquid state separated from the fuel recovered by the gas-liquid separator along the return line (RL) is supplied between the transfer pump and the compression pump along the recirculation line (RL1) and recycled, and the lubricating oil is lubricating oil discharge tank 210 is emitted with A valve Va that opens and closes according to the liquid level of the gas-liquid separator is provided in the recirculation line RL1.

The gas separated from the gas-liquid separator is returned to the fuel supply tank (T) through the vapor line (RLg), and the vapor line (RLg) has a pressure control valve (Vb) for controlling the gas transferred to the fuel supply tank (T). is provided

In order to send liquefied gas from the gas-liquid separator to the fuel supply line at the rear of the transfer pump, the pressure of the gas-liquid separator must be kept higher than the discharge pressure of the transfer pump. If the differential pressure is large, the differential pressure controller (DPIC) opens the pressure control valve (Vb) to discharge a large amount of gas from the gas-liquid separator to the fuel supply tank (T) to lower the pressure in the gas-liquid separator. The differential pressure is reduced by increasing the pressure in the gas-liquid separator. In this way, the liquid level of the gas-liquid separator can be kept constant by adjusting the differential pressure between the gas-liquid separator and the discharge side of the transfer pump to adjust the amount of liquefied gas sent from the gas-liquid separator to the discharge side of the transfer pump.

However, in such a fuel supply system, when the load of the compression pump changes according to the load of the propulsion engine and the discharge pressure of the transfer pump changes, this is directly related to the pressure change of the gas-liquid separator. Frequent pressure changes in the gas-liquid separator adversely affect liquid level control, which in turn causes instability of the entire fuel supply system, requiring improvement, and the following embodiments are derived to improve this.

2 schematically shows a fuel supply system for a ship according to an embodiment of the present invention improved from the above-described basic embodiment. Descriptions of configurations overlapping with those of the above-described basic embodiment will be omitted.

The system of the present embodiment transfers liquefied gas separated from the gas-liquid separator 200 to the front end of the transfer pump 100 of the compression unit so that the pressure of the gas-liquid separator can be more stably maintained even when the load of the engine is changed to increase the operational stability of the fuel supply system. transported to and recycled.

Accordingly, in this embodiment, the liquid line for supplying the liquefied gas in the liquid state separated in the gas-liquid separator 200 to the front end of the compression part of the fuel supply line SL, that is, upstream of the compression pump 110 and the transfer pump 100 ( LL) is connected, and a first valve V1 for opening and closing the pipe is provided in the liquid line.

The liquid level detector (LT) detects the level of the liquefied gas in the gas-liquid separator, and according to the detected level of the liquefied gas, the level controller (LC) controls the first valve (V1) of the liquid line to supply the liquefied gas from the gas-liquid separator to the inlet side of the transfer pump. It is possible to adjust the liquid level of the gas-liquid separator while transferring the

In this way, by recirculating LPG recovered from the engine and passed through the gas-liquid separator to the inlet side of the transfer pump, the pressure of the gas-liquid separator is not directly affected by the change in discharge pressure of the transfer pump and the compression pump due to the change in the load of the propulsion engine, The stability of operation and control can be improved. In particular, even if an emergency stop of the engine or fuel supply system occurs, the pressure of the gas-liquid separator is not affected by the pressure change on the discharge side of the transfer pump, which varies greatly depending on whether the pump is in operation, so interference between devices is minimized to ensure stable control and operation of the gas-liquid separator This is possible, and it is easy to return to normal operation.

Meanwhile, a check valve (CV) is provided between the junction of the liquid line (LL) in the fuel supply line (SL) and the fuel supply tank (T). Even if the lubricating oil in the fuel recovered from the engine is separated and discharged through the gas-liquid separator, some lubricating oil may be included in the liquefied gas recirculated to the liquid line (LL). is provided to prevent the recirculating liquefied gas from flowing back to the fuel supply tank.

In this embodiment, the gas discharge line (GL) for transferring the gas separated in the gas-liquid separator 200 to the fuel supply tank (T) is connected to the fuel supply tank (T), and the gas discharge line has a second pipe for opening and closing. A valve V2 is provided.

The pressure sensor (PT) detects the pressure of the gas-liquid separator (200), and the pressure controller (PIC) adjusts the opening of the second valve (V2) according to the pressure detected by the pressure sensor to release the gas in the gas-liquid separator (200). While discharging to the fuel supply tank, the pressure of the gas-liquid separator can be maintained higher than the pressure of the fuel supply tank. In this way, in this embodiment, since the pressure of the gas-liquid separator is set to a higher pressure than the pressure of the fuel supply tank with relatively little pressure change and maintained constant, the system can be operated more stably, and accordingly, the liquid level control of the gas-liquid separator is also This can be done under stable pressure.

The present invention is not limited to the above embodiments, and it can be practiced with various modifications or variations within a range that does not deviate from the technical gist of the present invention to those skilled in the art to which the present invention belongs. It is self-evident.

T: fuel supply tank
E: engine
SL: fuel supply line
RL: return line
LL: Liquidline
GL: gas discharge line
100: transfer pump
110: compression pump
120: heat exchanger
200: gas-liquid separator
210: lubricating oil discharge tank

Claims (9)

A fuel supply line for supplying liquefied gas from a fuel supply tank provided in a ship to an engine on board;
a compression unit provided in the fuel supply line and compressing the liquefied gas to a pressure required for the engine;
a return line for recovering liquefied gas not consumed by the engine among the liquefied gas supplied to the engine from the engine;
a gas-liquid separator provided in the return line and separating gas-liquid fuel recovered from the engine; and
A liquid line for supplying the liquefied gas in the liquid state separated in the gas-liquid separator to the front end of the compression part of the fuel supply line;
The fuel supply system of a ship, characterized in that the liquefied gas is supplied to the engine in a liquid state. According to claim 1,
The gas-liquid separator separates and removes the lubricating oil mixed in the fuel recovered from the engine. The method of claim 1, wherein the compression unit
a transfer pump transferring liquefied gas to be supplied to the engine from the fuel supply tank; and
Ship's fuel supply system comprising: a compression pump for boosting the liquefied gas transferred from the transfer pump to a pressure required for the engine. According to claim 3,
a first valve opening and closing the liquid line;
a liquid level sensor for detecting a liquid gas level in the gas-liquid separator; and
A fuel supply system for a ship further comprising: a liquid level controller controlling the first valve by the level of the liquefied gas detected by the liquid level sensor. According to claim 4,
Ship's fuel supply system further comprising: a check valve provided between the fuel supply tank and the junction of the liquid line in the fuel supply line. According to claim 5,
a gas discharge line for transferring the gas separated in the gas-liquid separator to the fuel supply tank; and
A second valve for opening and closing the gas discharge line: Ship's fuel supply system further comprising a. According to claim 6,
a pressure sensor for sensing the pressure of the gas-liquid separator; and
Further comprising: a pressure controller for controlling the second valve by the pressure sensed by the pressure sensor,
The vessel's fuel supply system, characterized in that the pressure controller adjusts the opening of the second valve according to the pressure sensed by the pressure sensor to maintain the pressure of the gas-liquid separator higher than the pressure of the fuel supply tank. According to any one of claims 3 to 7,
a heat exchanger provided downstream of the compression pump in the fuel supply line to heat liquefied gas to be supplied to the engine; and
A fuel supply system for a ship further comprising: a decompression unit provided upstream of the gas-liquid separator in the return line to depressurize the liquefied gas recovered from the engine. The liquefied gas is transported from the fuel supply tank provided on the ship, compressed through the compression unit, and supplied as fuel to the ship's engine in a liquid state.
The liquefied gas not consumed in the engine is recovered by the gas-liquid separator to separate gas and lubricating oil, and the liquefied gas in liquid state separated in the gas-liquid separator is transferred to the front end of the compression unit and recycled,
A fuel supply method for a ship, characterized in that maintaining the pressure of the gas-liquid separator higher than the pressure of the fuel supply tank while discharging the gas separated in the gas-liquid separator to the fuel supply tank.

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