KR102589456B1 - Fuel Supply System and Method for Ships - Google Patents

Abstract

The present invention relates to a fuel supply system and method for a ship that can prevent the problem of increased evaporation gas generation in a storage tank in order to maintain the minimum flow rate of the fuel supply pump.
The fuel supply method for ships according to the present invention compresses the boil-off gas or forced vaporization gas of liquefied gas and supplies it as fuel for the engine, and re-liquefies the gas fuel in an amount exceeding the amount of fuel required by the engine to produce liquefied gas. Recovering to the storage tank, supplying the forced vaporization gas as fuel for the engine includes discharging the liquefied gas from the liquefied gas storage tank and vaporizing the discharged liquefied gas, and converting the liquefied gas into the engine. When gas fuel below the discharge pump operating range is required, the pump is not operated, and the re-liquefied boil-off gas is vaporized and supplied to the engine.

Description

{Fuel Supply System and Method for Ships}

The present invention relates to a fuel supply system and method for a ship that can prevent the problem of increased evaporation gas generation in a storage tank in order to maintain the minimum flow rate of the fuel supply pump.

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 (BOG). ; Boil-Off Gas) occurs.

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 for treating boil-off gas generated in storage tanks are being studied. Recently, for processing boil-off gas, a method of using boil-off gas as fuel for a ship's engine, a method of using boil-off gas as fuel for a ship's engine, and a method of using boil-off gas as fuel for a ship's engine, re-liquefying boil-off gas and using it in a storage tank Methods of returning to are being used.

Among engines used in ships, dual fuel engines that can use natural gas as fuel include ME-GI (MAN Electronic Gas Injection) engines and X-DF (eXtra long stroke Dual Fuel) engines. , DF engines (DFDE (Dual Fuel Diesel Electric), DFDG (Dual Fuel Diesel Generator)), etc.

In order to effectively process boil-off gas on ships, the boil-off gas generated by natural vaporization of LNG in the LNG storage tank is compressed and supplied to the pressure required by the engine. If the amount of boil-off gas is less than the amount required by the engine, LNG is supplied. is forcedly vaporized and supplied as fuel. The boil-off gas generated by natural gasification of LNG is called NBOG (Natural Boil-off Gas), and the natural gas generated by forced vaporization of LNG is called forced boil-off gas or FBOG (Forced Boil-off Gas).

Referring to FIG. 1, in order to supply FBOG as fuel for the engine 400, a fuel supply pump 310 is used to discharge LNG for fuel from a storage tank (cargo tank), and the fuel supply pump 310 pressurizes and transfers it. A vaporizer 320 is provided to vaporize the LNG.

When the flow rate of the fuel supply pump 310 falls below the minimum flow rate (pressure) of the fuel supply pump, a problem occurs in which LNG is vaporized, causing a cavitation phenomenon, and accordingly, the fuel supply pump 310 Vibration and heat are generated, which may cause the fuel supply pump 310 to be damaged or, in severe cases, damaged, resulting in safety problems.

Therefore, the inlet flow rate of the fuel supply pump 310 must be maintained above the minimum flow rate. Conventionally, in order to satisfy the minimum flow rate of the fuel supply pump 310, a control valve (CV) and a bypass line (BL) were applied downstream of the fuel supply pump 310.

Specifically, when the LNG fuel flow rate required by the engine 400 is less than the minimum flow rate of the fuel supply pump 310, the fuel supply pump 310 is allowed to inhale and discharge LNG at a minimum flow rate or more, and then fuel is supplied. Of the LNG pressurized by the pump 310, only the LNG fuel flow rate required by the engine 400 is transferred to the carburetor 320, and the remainder is returned to the storage tank through the bypass line (BL), so that the control valve (CV) ) is to control the opening degree.

As the LNG is pressurized by the fuel supply pump 310, the pressure of the LNG increases and the temperature also increases. According to this conventional method, the high-temperature and high-pressure LNG is returned to the storage tank and stored due to the heat ingress phenomenon. As the temperature inside the tank rises, NBOG increases.

In addition, when the fuel supply pump 310 is provided inside the storage tank, not only does the heat generated by the operation of the fuel supply pump 310 promote natural vaporization of LNG, but also the fuel supply pump 310 is operated. There is a problem that excessive power consumption occurs. Even if the fuel supply pump 310 is not provided inside the storage tank, the same phenomenon occurs because a stripping pump installed inside the storage tank must be operated to supply LNG inside the storage tank to the fuel supply pump 310.

Therefore, the present invention is intended to solve the above problems, and provides a ship's fuel supply system and We would like to provide a method.

According to one aspect of the present invention for achieving the above-described object, a compressor that compresses the boil-off gas generated in the liquefied gas storage tank to the pressure required by the engine; a re-liquefaction unit that re-liquefies compressed boil-off gas exceeding the amount of gas fuel required by the engine; A re-liquefaction line connecting the re-liquefaction unit and the liquefied gas storage tank so that the re-liquefied boil-off gas re-liquefied in the re-liquefaction unit is recovered into the liquefied gas storage tank; A fuel supply pump that discharges the liquefied gas stored in the liquefied gas storage tank to supply it as fuel for the engine; A vaporizer that vaporizes the liquefied gas transferred from the fuel supply pump and sends it to the compressor; A reliquefaction fuel line branched from the reliquefaction line and connected to the vaporizer so that the reliquefaction boil-off gas from the reliquefaction unit is transferred to the vaporizer; A third valve provided in the reliquefied fuel line; a control unit that stops operation of the fuel supply pump when the amount of gas fuel required by the engine is less than the minimum flow rate; and a flow rate controller that opens the third valve to adjust the flow rate of re-liquefied boil-off gas supplied to the vaporizer when the amount of gas fuel required by the engine is less than the minimum flow rate of the fuel supply pump operation range. A fuel supply system is provided.

Preferably, the temperature of the liquefied gas discharged from the fuel supply pump is higher than the temperature of the liquefied gas sucked into the fuel supply pump and the temperature of the re-liquefied boil-off gas, and the liquefied gas discharged from the fuel supply pump is converted to a vaporizer. a first valve for controlling the opening and closing of the flow path to supply; A flow rate control line branched from a forced vaporization line connecting the fuel supply pump and the vaporizer so that the liquefied gas discharged by the fuel supply pump is recovered into the liquefied gas storage tank; a second valve installed in the flow control line, the opening rate of which is controlled to control the flow rate of liquefied gas supplied from the fuel supply pump to the vaporizer; And by calculating the flow rate of the liquefied gas discharged from the fuel supply pump, the opening rate of the second valve is adjusted so that the liquefied gas in an amount exceeding the flow rate of the liquefied gas required by the vaporizer is recovered into the liquefied gas storage tank. It may further include a flow rate regulator for controlling.

Preferably, when the amount of gas fuel required by the engine is less than the minimum flow rate of the fuel supply pump operation range, the first valve is closed by the flow rate controller, and the second valve is closed by the flow rate controller. You can.

Preferably, the re-liquefaction unit includes a boosting compressor that further compresses the boil-off gas compressed by the compressor to a critical pressure or higher; A heat exchanger that cools the compressed boil-off gas by exchanging heat between the boil-off gas compressed by the boosting compressor and the boil-off gas before compression supplied to the compressor from the liquefied gas storage tank; A pressure reducing valve that expands the boil-off gas cooled by the heat exchanger; a gas-liquid separator that separates the gas-liquid mixture generated by the pressure reducing valve; And a gas recovery line for joining the uncondensed boil-off gas in the gaseous state separated by the gas-liquid separator to the pre-compression boil-off gas flow supplied to the heat exchanger, and re-liquefaction evaporation in the liquid state separated by the gas-liquid separator. Gas may flow along the reliquefaction line or reliquefaction fuel line.

Preferably, a cooler for cooling the forced vaporization gas generated by vaporizing the liquefied gas in the vaporizer; A methane number regulator that separates the gas-liquid mixture generated by the cooler; A condensate recovery line that discharges liquid heavy hydrocarbons separated from gas and liquid in the methane number controller from the methane number controller; And it may further include a forced vaporization line that supplies light hydrocarbons in a gaseous state separated from gas-liquid in the methane number regulator to the compressor.

According to another aspect of the present invention for achieving the above-described object, the boil-off gas or forced vaporization gas of liquefied gas is compressed and supplied as fuel for the engine, and the gas fuel in an amount exceeding the amount of fuel required by the engine is It is re-liquefied and recovered to a liquefied gas storage tank, and supplying the forced vaporization gas as fuel for the engine includes discharging the liquefied gas from the liquefied gas storage tank and vaporizing the discharged liquefied gas, and the engine When gas fuel below the operating range of the pump for discharging the liquefied gas is required, a fuel supply method for ships is provided in which the re-liquefied boil-off gas is vaporized and supplied to the engine without operating the pump.

Preferably, the flow rate of the liquefied gas flowing into the vaporizer from the pump is measured, the flow rate of the liquefied gas discharged from the pump is calculated, and when the measured flow rate is greater than the flow rate required by the vaporizer, from the pump The opening rate of the valve can be adjusted so that an amount of the discharged liquefied gas that exceeds the flow rate required by the vaporizer is recovered into the liquefied gas storage tank.

The ship's fuel supply system and method according to the present invention can solve the problem of the internal temperature of the storage tank rising due to heat influx accompanying the use of the fuel supply pump and the problem of increased power consumption.

In addition, the methane value of the engine can be satisfied by vaporizing the re-liquefied boil-off gas and supplying it as fuel for the engine.

Figure 1 is a schematic diagram illustrating a typical ship fuel supply system.
Figure 2 is a schematic diagram illustrating a ship's fuel supply system according to an embodiment of the present invention.

In order to fully understand the operational advantages of the present invention and the objectives achieved by embodiments 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 structure and operation of a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. Here, in adding reference numerals to components in each drawing, it should be noted that identical components are indicated with the same reference numerals as much as possible, even if they are shown in different drawings.

In the embodiments of the present invention described later, the ship may be any type of ship equipped with a storage tank for storing liquefied gas. Representative examples include ships with self-propulsion capabilities such as LNG carriers, liquid hydrogen carriers, and LNG RVs (Regasification Vessels), as well as LNG FPSOs (Floating Production Storage Offloading) and LNG FSRUs (Floating Storage Regasification Units). Marine structures that do not have capabilities but are floating at sea may also be included.

In addition, in this embodiment, the liquefied gas is, for example, LNG (Liquefied Natural Gas), LEG (Liquefied Ethane Gas), LPG (Liquefied Petroleum Gas), Liquefied Ethylene Gas, and Liquefied Propylene Gas. , ammonia, liquefied hydrogen, etc., can be low-temperature fluids that are stored and transported in liquid form and can be used as fuel for engines. In the embodiments described later, the liquefied gas will be LNG as an example.

In addition, the ship according to this embodiment may be a liquefied gas propulsion ship capable of propulsion using liquefied gas in a liquid state, boil-off gas generated by natural vaporization of liquefied gas, or gas generated by forced vaporization of liquefied gas as fuel. there is.

For example, in this embodiment, the engine may be a dual-fuel engine that can use natural gas and fuel oil selectively or in combination.

Among the engines used in ships, dual fuel engines that can use natural gas as fuel include ME-GI (MAN Electronic Gas Injection) engines, X-DF (eXtra long stroke Dual Fuel) engines, and DF engines. (DFDE (Dual Fuel Diesel Electric), DFDG (Dual Fuel Diesel Generator)), etc.

ME-GI engines are mainly used for propulsion using a 2-stroke cycle. Additionally, the ME-GI engine operates based on the diesel cycle, which injects high-pressure natural gas of approximately 300 bar directly into the combustion chamber near the top dead center of the piston. The X-DF engine is mainly used for propulsion using a 2-stroke cycle, and like the ME-GI engine, it directly drives the propeller to propel the ship. In addition, the X-DF engine uses medium pressure natural gas of approximately 16 bar as fuel and operates based on the Otto cycle. DF engines are mainly used for power generation using a 4-stroke cycle. Additionally, the DF engine operates based on the Otto cycle, which injects low-pressure natural gas of approximately 6.5 bar into the combustion air inlet and compresses it as the piston rises.

In engines that operate based on the diesel cycle, only air is compressed during the compression stroke, so the knocking phenomenon, which is a phenomenon in which premature ignition occurs before the piston reaches top dead center, does not fundamentally occur. However, in an engine operating based on the Otto cycle, a mixture of fuel and combustion air is introduced into the cylinder before the upward stroke, so early ignition may occur before ignition by the ignition source, resulting in a knocking phenomenon.

In an embodiment of the present invention described later, an X-DF engine is used as a propulsion engine and a DFDG is used as a power generation engine.

Hereinafter, with reference to FIG. 2, a fuel supply system and method for a ship according to an embodiment of the present invention will be described. The ship's fuel supply system according to an embodiment of the present invention shown in FIG. 2 is installed inside the storage tank in order to maintain the minimum flow rate of the fuel supply pump 310 generated in the general ship's fuel supply system shown in FIG. 1. An improved ship fuel supply system is provided to solve problems such as rising temperatures.

Referring to FIG. 2, the ship's fuel supply system according to an embodiment of the present invention supplies boil-off gas (NBOG) generated in an LNG cargo tank (not shown) storing LNG to the fuel demand source 400. A boil-off gas supply unit that supplies forced vaporization gas (FBOG) obtained by forcibly vaporizing LNG stored in an LNG storage tank to the fuel demander (400) exceeds the amount of gas fuel required by the fuel demander (400). It includes a re-liquefaction unit that re-liquefies the amount of boil-off gas or forced vaporization gas and returns it to the storage tank.

The boil-off gas supply unit includes a compressor 200 that compresses the boil-off gas transferred through the boil-off gas supply line (NL) connected from the top of the storage tank and supplies it to the fuel demand source 400.

In this embodiment, the fuel demand source 400 produces heat energy such as steam required by the heat source demand source within the ship by burning the It may include an auxiliary boiler 430 that combusts and processes gas in an emergency situation, and a Gas Combustion Unit (GCU) 440.

The X-DF engine 410 requires about 10 to 18 bar of gaseous fuel for combustion, or about 12 to 16 bar. The compressor 200 of this embodiment can compress the boil-off gas to the pressure required by the X-DF engine 410.

The boil-off gas compressed in the compressor 200 is transferred to the fuel consumer 400 through a fuel supply line (SL) connecting the compressor 200 and the fuel consumer 400.

On the other hand, it further includes a re-liquefaction line (RL) branched from the fuel supply line (SL) connecting the compressor 200 and the fuel demand source 400 and connected to the re-liquefaction unit, so that the amount of boil-off gas increases with the fuel demand source 400. If it is more than the amount required, the boil-off gas subject to reliquefaction in excess of the amount required by the fuel consumer 400 is transferred to the reliquefaction unit through the reliquefaction line (RL), is reliquefied, and then stored in a storage tank. It is recovered as

The re-liquefaction unit of this embodiment includes a boosting compressor 510 that further compresses the excess boil-off gas compressed in the compressor 200 above the critical pressure to increase re-liquefaction efficiency, and a boosting compressor 510 that evaporates the boil-off gas compressed in the boosting compressor 510. A heat exchanger (100) that cools the boil-off gas with the cold heat of the boil-off gas before compression directed to the compressor (100) through the gas supply line (NL), and expands the boil-off gas cooled by the heat exchanger (100) to create a low-temperature, low-pressure gas-liquid mixture. It includes a pressure reducing valve 520 that generates pressure, and a gas-liquid separator 530 that separates the gas-liquid mixture generated by the pressure reducing valve 520.

The boosting compressor 510 of this embodiment may further compress the boil-off gas compressed in the compressor 300 to a critical pressure, for example, about 50 to 150 bar.

The pressure reducing valve 520 of this embodiment may be a Joule-Thompson valve, and the temperature of the boil-off gas is lowered as the boil-off gas expands isentropically by the pressure-reducing valve 520, and a gas-liquid mixture is generated in this process.

In this embodiment, the pressure reducing valve 520 is described as an example of a Joule-Thompson valve, but the pressure reducing valve 520 may be an expander, a compander that converts the expansion work into compression work, or an electric power supply for the expansion work. It may be an expansion-generator that converts to .

The operating pressure of the gas-liquid separator 530 in this embodiment may be about 4.5 barg. That is, the pressure reducing valve 520 of this embodiment can reduce the pressure of the boil-off gas to about 4.5 barg.

The liquid re-liquefied boil-off gas separated in the gas-liquid separator 530 is recovered to the storage tank through the re-liquefaction line (RL) connecting the gas-liquid separator 530 and the storage tank, and the gas separated in the gas-liquid separator 530 The uncondensed boil-off gas is introduced from the storage tank into the heat exchanger 100 through the gas recovery line (GL) connected from the gas-liquid separator 530 to the boil-off gas supply line (NL) upstream of the heat exchanger 100. Can join the gas flow.

Meanwhile, if the amount of boil-off gas is less than the amount required by the fuel demander 400, the forced vaporization gas supply unit may generate forced vaporization gas and supply it to the fuel demander 400.

The forced vaporization gas supply unit of this embodiment includes a fuel supply pump 310 that pressurizes and discharges the LNG to be forcedly vaporized from the storage tank, and a vaporizer that vaporizes the LNG transferred from the fuel supply pump 310 through the forced vaporization line (FL). Includes (320).

The fuel supply pump 310 can compress LNG to the pressure required by the vaporizer 320. For example, the operating pressure of the carburetor 320 of this embodiment is about 4 barg, and therefore the fuel supply pump 310 of this embodiment pressurizes and transfers LNG so that the inlet pressure of the carburetor 320 can be maintained at 4 barg. can do.

In addition, the forced vaporization gas supply unit of this embodiment includes a cooler 330 that cools the forced vaporization gas vaporized in the vaporizer 320 to produce a gas-liquid mixture, and separates the gas-liquid mixture generated in the cooler 330 to produce light hydrocarbons. and a methane number regulator 340 that separates heavy hydrocarbons.

A cooling line (CL) branching from the forced vaporization line (FL) upstream of the vaporizer (320) may be connected to the cooler (430) of this embodiment. The cooler 430 mixes the forced vaporization generated in the vaporizer 320 with the LNG transferred through the cooling line (CL) to generate a gas-liquid mixture. In this process, the heavy hydrocarbon components with a high liquefaction point are condensed, and the light hydrocarbon components with a low liquefaction point, that is, methane, remain in a gaseous state.

The gas-liquid mixture generated in the cooler 430 is separated from gas and liquid in the methane number controller 340, and the liquid separated in the methane number controller 340, that is, heavy hydrocarbons, can be transferred to the storage tank through the condensate recovery line (HL). In addition, the gas separated from the methane number controller 340, that is, the methane-rich gas, is compressed through the forced vaporization line (FL) connecting the methane number controller 340 and the fuel supply line (SL) upstream of the compressor 200. ) can be transferred to.

Meanwhile, the fuel supply pump 310 has a set flow rate range that it can support, that is, the minimum flow rate and maximum flow rate, and in order to prevent damage to the fuel supply pump 310, the flow rate of the fuel supply pump 310 inlet must be set to the fuel supply pump 310. It must be maintained above the minimum flow rate supported by (310). For example, if the flow rate range that the fuel supply pump 310 can support is 2 to 12 m ³ /hr, the flow rate at the inlet of the fuel supply pump 310 must be maintained at least 2 m ³ /hr.

If the flow rate of the forced vaporization line (FL) connecting the fuel supply pump 310 and the carburetor 320 remains above a preset value according to the supportable flow rate range of the fuel supply pump 310, the fuel supply pump 310 ) The flow rate at the inlet can be maintained above the minimum flow rate.

According to this embodiment, in order to control the flow rate of the fuel supply pump 310, the flow rate of the forced vaporization line (FL) connecting the fuel supply pump 310 and the carburetor 320, that is, the inlet pressure of the carburetor 320 ( As a control means for controlling the flow rate to be maintained above the set value, a first valve (V1) installed on the forced vaporization line (FL) connecting the fuel supply pump 310 and the carburetor 320, and a fuel supply It includes a flow control line (BL) branched from the forced vaporization line (FL) downstream of the pump 310 and connected back to the storage tank, and a second valve (V2) installed on the flow control line (BL).

In addition, a re-liquefied fuel line (LL) connected from the gas-liquid separator 530 to a forced vaporization line (FL) connecting the fuel supply pump 310 and the carburetor 320, and installed on the re-liquefied fuel line (LL) It further includes a third valve (V3).

In addition, a flow meter (FM) that measures the flow rate of LNG transferred from the fuel supply pump 310 to the vaporizer 320, and a ammeter (CT) that measures the current of the motor (M) that drives the fuel supply pump 310. It further includes. The flow rate of the fuel supply pump 310 can be calculated from the current measurement value of the ammeter (CT).

In addition, a flow controller (FIC) that controls the opening and closing of the first valve (V1) and the third valve (V3) according to the flow rate measurement value of the flow meter (FM), and fuel supply calculated from the current measurement value of the ammeter (CT) It further includes a flow rate controller (CIC) that controls the opening and closing of the second valve (V2) according to the flow rate of the pump 310.

Conventionally, when the flow rate of LNG discharged from the fuel supply pump 310 exceeds the flow rate of LNG to be forcibly vaporized, that is, the inlet pressure of the vaporizer 320, the opening degree of the second valve V2 is adjusted, The high-temperature LNG discharged from the fuel supply pump 310 was returned to the storage tank through the flow control line (BL).

In addition, conventionally, even when the flow rate of LNG to be forcedly vaporized is less than the flow rate range that the fuel supply pump 310 can support, the fuel supply pump 310 suctions and discharges LNG from the storage tank at more than the minimum flow rate. 2 The opening rate of the valve (V2) was increased, and the amount of the discharged LNG exceeding the LNG flow rate to be forcedly vaporized was recovered into the storage tank through the flow control line (BL).

However, according to this existing method, there is a problem in that LNG, whose temperature has increased due to compression, is returned to the storage tank, increasing the internal temperature of the storage tank and increasing the amount of boil-off gas generated.

According to this embodiment, a reliquefaction fuel line (LL) is provided to recover high temperature LNG through the flow control line (BL), such as when the flow rate of LNG to be forcedly vaporized is less than the minimum flow rate of the fuel supply pump 310. In cases where it is necessary to do so, rather than supplying the LNG to be forcibly vaporized from the storage tank to the vaporizer 320, the re-liquefied boil-off gas condensed in the gas-liquid separator 530 is transferred through the re-liquefied fuel line (LL) to the vaporizer (320). ) can be supplied.

When supplying the re-liquefied boil-off gas condensed in the gas-liquid separator 530 to the vaporizer 320, the flow controller (FIC) sends a signal to close the first valve (V1), and the flow controller (CIC) sends a signal to close the second valve ( A signal to close V2) is sent to close the first valve V1 and the second valve V2, and a control unit (not shown) instructs the fuel supply pump 310 to stop operating. Thereafter, the flow controller (FIC) adjusts the flow rate of LNG supplied from the gas-liquid separator 530 to the vaporizer 320 while adjusting the opening rate of the third valve (V3) according to the flow rate measurement value of the flow meter (FM). .

In this way, by supplying the re-liquefied boil-off gas to the vaporizer 320 without operating the fuel supply pump 310, there is no need to recover pressurized LNG to maintain the minimum flow rate of the fuel supply pump 310, so the conventional flow control line ( By recovering pressurized LNG through BL), the problem of the internal temperature of the storage tank rising can be prevented.

In addition, it is possible to prevent the problem of excessively increasing evaporative gas generation inside the storage tank.

In addition, since there is no need to operate the fuel supply pump 310, the problem of an increase in the amount of evaporative gas generated in the storage tank due to the operation of the fuel supply pump 310 can be prevented, and in order to operate the fuel supply pump 310, Power consumption can be reduced.

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

100: heat exchanger
200: Compressor
310: Fuel supply pump
320: carburetor
330: Cooler
340: Methane number regulator
400: Fuel demand source
510: Boosting compressor
520: pressure reducing valve
530: Gas-liquid separator
LL: Reliquefaction fuel line
V1: first valve
V2: second valve
V3: Third valve
FIC: flow controller

Claims (7)

A compressor that compresses the boil-off gas generated in the liquefied gas storage tank to the pressure required by the engine;
a re-liquefaction unit that re-liquefies compressed boil-off gas exceeding the amount of gas fuel required by the engine;
A re-liquefaction line connecting the re-liquefaction unit and the liquefied gas storage tank so that the re-liquefied boil-off gas re-liquefied in the re-liquefaction unit is recovered into the liquefied gas storage tank;
A fuel supply pump that discharges the liquefied gas stored in the liquefied gas storage tank to supply it as fuel for the engine;
A vaporizer that vaporizes the liquefied gas transferred from the fuel supply pump and sends it to the compressor;
A reliquefaction fuel line branched from the reliquefaction line and connected to the vaporizer so that the reliquefaction boil-off gas from the reliquefaction unit is transferred to the vaporizer;
A third valve provided in the reliquefied fuel line;
When the amount of gas fuel required by the engine is less than the minimum flow rate of the fuel supply pump, operation of the fuel supply pump is stopped and the third valve is opened to supply the re-liquefied evaporation gas to the vaporizer, thereby re-liquefying evaporation. A control unit that supplies gas as fuel to the engine; and
A flow rate controller that opens the third valve to adjust the flow rate of the re-liquefied boil-off gas supplied to the vaporizer when the amount of gas fuel required by the engine is less than the minimum flow rate of the fuel supply pump operation range. Fuel supply system. In claim 1,
The temperature of the liquefied gas discharged from the fuel supply pump is higher than the temperature of the liquefied gas sucked into the fuel supply pump and the temperature of the re-liquefied boil-off gas,
A first valve for controlling the opening and closing of a flow path so that the liquefied gas discharged from the fuel supply pump is supplied to the vaporizer;
A flow rate control line branched from a forced vaporization line connecting the fuel supply pump and the vaporizer so that the liquefied gas discharged by the fuel supply pump is recovered into the liquefied gas storage tank;
a second valve installed in the flow control line, the opening rate of which is controlled to control the flow rate of liquefied gas supplied from the fuel supply pump to the vaporizer; and
Calculate the flow rate of the liquefied gas discharged from the fuel supply pump and control the opening rate of the second valve so that the liquefied gas in an amount exceeding the flow rate of the liquefied gas required by the vaporizer is returned to the liquefied gas storage tank. A fuel supply system for a ship, further comprising a flow rate regulator. In claim 2,
If the amount of gas fuel required by the engine is less than the minimum flow rate of the fuel supply pump operation range,
the first valve is closed by the flow controller,
The second valve is closed by the flow regulator. In claim 1,
The reliquefaction unit,
A boosting compressor that further compresses the boil-off gas compressed by the compressor to a critical pressure or higher;
A heat exchanger that cools the compressed boil-off gas by exchanging heat between the boil-off gas compressed by the boosting compressor and the boil-off gas before compression supplied to the compressor from the liquefied gas storage tank;
A pressure reducing valve that expands the boil-off gas cooled by the heat exchanger;
a gas-liquid separator that separates the gas-liquid mixture generated by the pressure reducing valve; and
It includes a gas recovery line for joining the gaseous uncondensed boil-off gas separated by the gas-liquid separator into the pre-compression boil-off gas flow supplied to the heat exchanger,
A ship's fuel supply system wherein the liquid re-liquefied boil-off gas separated by the gas-liquid separator flows along the re-liquefied line or re-liquefied fuel line. In claim 1,
A cooler that cools the forced vaporization gas generated by vaporizing the liquefied gas in the vaporizer;
A methane number regulator that separates the gas-liquid mixture generated by the cooler;
A condensate recovery line that discharges liquid heavy hydrocarbons separated from gas and liquid in the methane number controller from the methane number controller; and
A fuel supply system for a ship, further comprising a forced vaporization line that supplies gaseous light hydrocarbons separated from gas-liquid in the methane number regulator to the compressor. The boil-off gas of liquefied gas or forced vaporization gas is compressed and supplied as fuel for the engine.
Gas fuel in an amount exceeding the amount of fuel required by the engine is re-liquefied and recovered into a liquefied gas storage tank,
Supplying the forced vaporization gas as fuel for the engine,
Discharging the liquefied gas from the liquefied gas storage tank,
Including vaporizing the discharged liquefied gas,
When the engine requires gas fuel below the operating range of the pump for discharging the liquefied gas, the pump is not operated, and at least a portion of the re-liquefied boil-off gas returned to the liquefied gas storage tank is vaporized and supplied to the engine. A method of supplying fuel to a ship. In claim 6,
Measure the flow rate of liquefied gas flowing into the vaporizer from the pump,
Calculate the flow rate of liquefied gas discharged from the pump,
If the measured flow rate is greater than the flow rate required by the vaporizer, the opening rate of the valve is adjusted so that the amount of liquefied gas discharged from the pump exceeding the flow rate required by the vaporizer is recovered to the liquefied gas storage tank. Regulating the fuel supply method of a ship.

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