Fuel supply system and method for liquefied gas tanker

Abstract

The present invention discloses a fuel supply system and method for a liquefied gas carrier. The fuel supply system for a liquefied gas carrier of the present invention comprises a fuel supply pipeline, a delivery pump, a compression pump, a return pipeline, a separator, a liquid pipeline, a cooler, and a refrigerant supply pipeline, wherein the fuel supply pipeline is branched off between the junction of the delivery pump and the liquid pipeline, and all or part of the liquefied gas pumped from the delivery pump is supplied to the cooler as a refrigerant.

Description

Technical Field

[0001] The present invention relates to a fuel supply system and method for a liquefied gas carrier, and more specifically, to a fuel supply system and method for a liquefied gas carrier, which can recover and recirculate the excess liquefied gas that is oversupplied to the engine in a ship using liquefied gas such as LPG as fuel, while being able to effectively supply fuel to the engine. Background Art

[0002] The consumption of liquefied gases such as liquefied natural gas (LNG) or liquefied petroleum gas (LPG) is increasing rapidly around the world. Liquefied gases are transported in a gaseous state through land or sea gas pipelines, or stored in a liquefied state on liquefied gas carriers and transported to distant consumption sites. Liquefied gases such as LNG and LPG are obtained by cooling natural gas or petroleum gas to extremely low temperatures (about -163°C in the case of LNG), and their volume is greatly reduced compared to when they are in a gaseous state, making them very suitable for long-distance transportation by sea.

[0003] The liquefaction temperature of LPG is as low as about -42°C at atmospheric pressure. It can be stored in a liquid state at about 45°C at 18 bar and at 20°C at 7 bar. LPG evaporates at atmospheric pressure above -42°C, so the LPG storage tank of the ship is insulated. However, since external heat is continuously transferred to LPG, LPG is continuously vaporized in the LPG storage tank during LPG transportation, generating boil-off gas (Boil-Off Gas) in the LPG storage tank.

[0004] In an LPG transport ship, if boil-off gas accumulates in an LPG storage tank, the pressure in the LPG storage tank will increase excessively. Therefore, a pressure-resistant structure is provided in the LPG storage tank, and a boil-off gas reliquefaction device is used to process the boil-off gas generated in the tank.

[0005] On the other hand, existing LPG transport ships and the like use a fuel supply system that uses relatively cheap heavy oil such as Class C fuel oil as the ship's propulsion fuel. However, in such a heavy oil fuel supply system, due to the strengthening of international exhaust emission controls on the use of heavy oil fuel, it is necessary to additionally install a low-sulfur heavy oil fuel tank (LSHFO tank), and the demand for an environmentally friendly fuel supply system that meets international environmental control standards has increased.

[0006] In recent years, the use of fuel supply systems that use LPG or LNG and the evaporated gas generated therefrom as propulsion fuel has been increasing in LPG or LNG carriers. As international exhaust emission controls are strengthened, in addition to LPG or LNG carriers, the number of general ships that use LNG as propulsion fuel has also gradually increased.

[0007] In particular, LPG is easier to store than LNG, which is liquefied at extremely low temperatures, and does not significantly reduce specific energy and energy density compared to existing HFO. It has the advantage of significantly reducing SOx, NOx, CO2, PM, etc. compared to existing HFO. Summary of the invention

[0008] Technical issues to be solved

[0009] In a ship using LPG as fuel, LPG to be supplied to the engine as fuel is supplied from a fuel supply tank to the ship's engine via a fuel supply system including a compression pump, a heater, etc., in a manner that meets the fuel supply conditions of the engine.

[0010] LPG, which is a non-compressible fluid, can be oversupplied compared to the fuel required by the engine to immediately respond to changes in the engine load. The LPG that is oversupplied and remains after the fuel is consumed, the LPG that remains due to changes in the fuel consumption rate caused by changes in the engine load, and the LPG that remains in the engine and the pipeline when the engine is stopped are recovered upstream of the engine.

[0011] However, if the recovered LPG is directly discharged and burned, there is a problem of wasting fuel, and if the recovered LPG is sent to the cargo hold, there is a concern that the LPG cargo will be contaminated by the sealing oil flowing from the engine. In addition, since the recovered LPG is compressed and heated in a manner that meets the fuel supply conditions of the engine and is in a high-temperature and high-pressure state, if the LPG is sent to the fuel supply tank, there is a problem of rising pressure and temperature in the tank.

[0012] In order to solve such a technical problem, the present invention provides a system capable of effectively processing LPG recovered from an engine and efficiently supplying fuel.

[0013] Means of solving the problem

[0014] In order to solve the above technical problems, according to one aspect of the present invention, a fuel supply system for a liquefied gas carrier is provided, which comprises: a fuel supply pipeline for supplying liquefied gas from a fuel supply tank arranged on the deck of the ship to an engine in the ship; a delivery pump arranged on the fuel supply pipeline for delivering the liquefied gas to be supplied from the fuel supply tank to the engine; a compression pump arranged on the fuel supply pipeline for compressing the liquefied gas at a pressure required by the engine; and a reflux pipeline for recycling the liquefied gas not consumed by the engine to the upstream of the engine. ; a separator, arranged in the reflux pipeline, receiving the recycled liquefied gas and performing gas-liquid separation; a liquid pipeline, supplying the liquid liquefied gas separated in the separator to the rear end of the delivery pump of the fuel supply pipeline; a cooler, arranged in the fuel supply pipeline downstream of the confluence point of the liquid pipeline, for cooling the liquefied gas; and a refrigerant supply pipeline, branching from the fuel supply pipeline between the confluence point of the delivery pump and the liquid pipeline, supplying all or part of the liquefied gas pumped from the delivery pump as a refrigerant to the cooler.

[0015] Preferably, the refrigerant supply line may be connected to the fuel supply tank so that the liquefied gas used as the refrigerant in the cooler is recovered to the fuel supply tank.

[0016] Preferably, it may also include: a temperature regulating valve, which is arranged on the refrigerant supply pipeline; a branch pipeline, which branches off from the upstream of the cooler in the refrigerant supply pipeline and is connected to the fuel supply tank; and a flow regulating valve, which is arranged on the branch pipeline, and when the refrigerant flow required by the cooler is less than the minimum flow required by the delivery pump, the liquefied gas pumped by the delivery pump that exceeds the refrigerant flow required by the cooler is recovered to the fuel supply tank through the branch pipeline.

[0017] Preferably, it may also include: a fuel heater, which is arranged at the front end of the cooler in the fuel supply pipeline and is used to heat the liquefied gas; and a first temperature sensing unit, which is arranged at the rear end of the cooler in the fuel supply pipeline and is used to sense the temperature of the liquefied gas introduced into the compression pump.

[0018] Preferably, it may also include a second temperature sensing unit, which is arranged at the rear end of the compression pump in the fuel supply pipeline, and is used to sense the temperature of the liquefied gas to be supplied to the engine via the compression pump. When the temperature of the liquefied gas sensed by the first temperature sensing unit is lower than 25°C, steam is supplied to the fuel heater to heat the liquefied gas. When the temperature of the liquefied gas sensed by the first temperature sensing unit is higher than 33°C, the temperature regulating valve is opened, and the liquefied gas pumped from the delivery pump is supplied to the cooler through the refrigerant supply pipeline. The temperature of the liquefied gas sensed by the second temperature sensing unit is maintained at 26 to 44°C.

[0019] Preferably, the fuel tank may further include: a steam line for recovering the gas separated in the separator to the fuel supply tank; and a pressure regulating valve provided in the steam line.

[0020] Preferably, the rear end pressure of the delivery pump can be sensed, and the opening of the pressure regulating valve can be adjusted according to the sensed pressure, so that the pressure of the separator is maintained 0.5 to 2 bar higher than the rear end pressure of the delivery pump.

[0021] Preferably, a decompression unit may be further included, wherein the decompression unit is arranged upstream of the separator in the reflux line to decompress the recycled liquefied gas.

[0022] Preferably, the return line may include: a first return line connected from the engine to the separator; and a second return line connected from a fuel supply line at the rear end of the compression pump to the separator.

[0023] Preferably, the decompression unit may include: a first decompression device, which is provided in the first return line and decompresses the liquefied gas recovered from the engine; and a second decompression device, which is provided in the second return line.

[0024] Preferably, it may also include: a reliquefaction section, which receives boil-off gas generated from a cargo hold and reliquefies it, the cargo hold being arranged on the ship and storing liquefied gas to be transported; and a cooling pipeline, which is connected from the reliquefaction section to the cargo hold via the fuel supply tank, and the liquefied gas reliquefied in the reliquefaction section cools the fuel supply tank along the cooling pipeline and is transported to the cargo hold.

[0025] Preferably, the delivery pump and the compression pump may be constituted by side channel pumps.

[0026] According to another aspect of the present invention, there is provided a fuel supply method for a liquefied gas carrier, wherein the method comprises the following steps: compressing the liquefied gas from a fuel supply tank disposed on a deck of the ship along a fuel supply pipeline via a delivery pump and a compression pump, and supplying the liquefied gas as fuel to an engine in the ship;

[0027] Recirculating the liquefied gas not consumed by the engine to the upstream of the engine along a return line, providing a separator in the return line to separate the recirculated liquefied gas into gas and liquid, and supplying the liquefied gas separated in the separator to a fuel supply line at the rear end of the delivery pump through a liquid line; and

[0028] In the fuel supply pipeline, a cooler is arranged downstream of the confluence point of the liquid pipeline, and all or part of the liquefied gas pumped from the delivery pump is branched from the upstream of the confluence point of the liquid pipeline and supplied to the cooler as a refrigerant, thereby cooling the liquefied gas in the fuel supply pipeline.

[0029] Preferably, the liquefied gas used as a refrigerant in the cooler can be recovered to the fuel supply tank. When the refrigerant flow rate required by the cooler is less than the minimum flow rate required by the delivery pump, the liquefied gas pumped from the delivery pump that exceeds the refrigerant flow rate required by the cooler is branched from the upstream of the cooler and recovered to the fuel supply tank without passing through the cooler.

[0030] Preferably, a fuel heater can be arranged at the front end of the cooler in the fuel supply pipeline to sense the temperature of the liquefied gas introduced from the rear end of the cooler to the compression pump. When the sensed temperature of the liquefied gas is lower than 25°C, steam is supplied to the fuel heater to heat the liquefied gas. When the sensed temperature of the liquefied gas is above 33°C, the liquefied gas pumped from the delivery pump is branched from the upstream of the confluence point of the liquid pipeline and supplied to the cooler as a refrigerant to cool the liquefied gas. At the rear end of the compression pump, the temperature of the liquefied gas to be supplied to the engine is maintained at 26-44°C.

[0031] Preferably, the liquefied gas which is not consumed in the engine and is to be recycled along the return line may be cooled by decompression and then separated into gas and liquid in the separator.

[0032] Preferably, the delivery pump and the compression pump may be constituted by side channel pumps.

[0033] Effects of the Invention

[0034] In the present invention, the liquefied gas not consumed by the engine is recycled along the return line to the upstream of the engine, the recycled liquefied gas is separated into gas and liquid by a separator arranged in the return line, and the separated liquefied gas is supplied to the fuel supply line at the rear end of the delivery pump for recycling.

[0035] In particular, a cooler is arranged downstream of the liquid line confluence point of the fuel supply pipeline, and the liquefied gas of the fuel supply tank pumped from the delivery pump is supplied to the cooler as a refrigerant to cool the recirculated liquefied gas, thereby effectively adjusting the temperature of the liquefied gas in the fuel supply pipeline without the need for additional refrigerant.

[0036] Furthermore, by recycling the recirculated liquefied gas recovered from the engine to the fuel supply line via the separator, it is possible to prevent lubricating oil mixed with the fuel while passing through the engine from flowing into the fuel supply tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A fuel supply system for a liquefied gas tanker according to an embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0038] In order to fully understand the operational advantages of the present invention and the objects achieved by practicing the present invention, reference should be made to the drawings illustrating preferred embodiments of the present invention and the contents described in the drawings.

[0039] The structure and function of the preferred embodiment of the present invention are described in detail with reference to the accompanying drawings. It should be noted that when assigning reference numerals to the structural elements of each drawing, the same structural elements are marked with the same reference numerals as much as possible even if they are shown in different drawings.

[0040] In the embodiments of the present invention described later, the ship may be any type of ship equipped with an engine capable of using liquefied petroleum gas as a fuel for a propulsion engine or a fuel for a power generation engine. As a representative example, in addition to ships with self-propulsion capabilities such as LPG carriers, LNG carriers, liquid hydrogen carriers, and LNG regasification vessels (RV), offshore structures that do not have propulsion capabilities but float on the sea, such as LNG floating production storage offloading units (FPSO) and LNG floating storage and regasification units (FSRU), may also be included.

[0041] In addition, the present embodiment can be applied to a fuel supply system for all kinds of liquefied gases that can be transported by liquefying at low temperature and that can generate boil-off gas when stored and can be supplied as fuel for an engine. Such liquefied gas can be, for example, liquefied natural gas (LNG), liquefied ethane gas (LEG), liquefied petroleum gas (LPG), liquefied ethylene gas (Ethylene Gas), liquefied propylene gas (Propylene Gas), and liquefied petroleum gas, as well as ammonia gas. However, in the embodiments described below, the case of applying LPG, which is one of the representative liquefied gases, will be described as an example.

[0042] Figure 1 A fuel supply system for a liquefied gas tanker according to an embodiment of the present invention is schematically shown.

[0043] like Figure 1 As shown, the fuel supply system of this embodiment includes: a fuel supply pipeline SL, which supplies liquefied gas from a fuel supply tank DT arranged on the deck of the ship to the engine E in the ship; a delivery pump 100, which is arranged on the fuel supply pipeline, and delivers the liquefied gas to be supplied from the fuel supply tank to the engine; a compression pump 110, which is arranged on the fuel supply pipeline, and compresses the liquefied gas at the pressure required by the engine; a reflux pipeline RL1, RL2, which recirculates the liquefied gas not consumed by the engine to the upstream of the engine; a separator 200, It is arranged in the reflux pipeline, receives the recycled liquefied gas and performs gas-liquid separation; the liquid pipeline LL supplies the liquid liquefied gas separated in the separator to the rear end of the delivery pump of the fuel supply pipeline; the cooler 120b is arranged in the fuel supply pipeline downstream of the junction point of the above-mentioned liquid pipeline, and is used to cool the above-mentioned liquefied gas; the refrigerant supply pipeline BL branches from the above-mentioned fuel supply pipeline between the junction point of the delivery pump and the above-mentioned liquid pipeline, and supplies all or part of the liquefied gas pumped from the above-mentioned delivery pump as a refrigerant to the above-mentioned cooler. The refrigerant supply pipeline is connected to the fuel supply tank, and the liquefied gas used as a refrigerant in the cooler is recovered to the fuel supply tank.

[0044] The system of this embodiment recirculates the liquefied gas not consumed by the engine along the return line to the upstream of the engine, separates the gas and liquid of the recirculated liquefied gas by a separator arranged in the return line, and supplies the separated liquefied gas to the fuel supply line at the rear end of the delivery pump for recirculation, and in particular, a cooler is arranged downstream of the line junction of the liquid pipe of the fuel supply line, and the liquefied gas of the fuel supply tank pumped from the delivery pump is supplied to the cooler as a refrigerant, so that the temperature of the liquefied gas in the fuel supply line can be effectively adjusted without the need for additional refrigerant. In the system of this embodiment, the fuel supply to the engine is realized as follows.

[0045] The ship of this embodiment is a liquefied gas carrier, and is equipped with a cargo tank (not shown) for storing and transporting liquefied gas (LPG, for example), and a fuel supply tank is provided on the deck of the ship separately from the cargo tank, and the fuel supply tank stores the liquefied gas to be used as fuel in the ship. The fuel supply tank stores LPG at a pressure of 1 to 8 barg, and at an operating pressure of about 4 barg, for example, and supplies fuel to the engine through a fuel supply line.

[0046] The liquefied gas stored in the fuel supply tank DT is delivered by the delivery pump 100, compressed to the fuel supply pressure of the engine by the compression pump 110, and then supplied to the engine. In this embodiment, the delivery pump and the compression pump may be constituted by a side channel pump, for example.

[0047] The liquefied gas compressed by each pump of the fuel supply line SL passes through the filter 130 for filtering impurities in the fuel and the service valve unit SVT and is supplied to the engine E. When the fuel oil of the engine is switched or the LPG mode is stopped when LPG is supplied to the engine, or when the LPG fuel supply is interrupted due to tripping, the service valve unit double-closes each pipeline with a valve and eliminates the pressure in the pipeline.

[0048] An example of an engine that receives such compressed and heated LPG as fuel is the ME-LGIP engine of MANDiesel & Turbo. In this case, LPG is delivered from a delivery pump at about 15 barg, and then supplied to the engine at a high pressure liquid state of about 53 barg and 35°C via a compression pump, etc. for 2 to 4 m 3 / h, and in the engine, the oil is injected into the nozzle at a hydraulic pressure of 600 to 700 bar to drive the engine. When a side channel pump is used as a delivery pump and a compression pump, a portion of the LPG can be heated by a lower pump efficiency of about 20% and compression.

[0049] In the engine of this embodiment, the compressed and heated fuel is supplied to the engine in a liquid state. However, unlike an engine supplied with a compressible fluid, i.e., a gas fuel, whose volume changes greatly according to pressure changes, when LPG in a non-compressible fluid, i.e., a liquid state, whose volume does not change or changes only slightly even when pressure is applied is supplied as the engine fuel, sufficient fuel is supplied to respond immediately even when the load of the engine changes, and an excessive amount of LPG is supplied to the engine to prevent cavitation. The LPG remaining after the LPG supplied to the engine is consumed as fuel is discharged from the engine through the return line RL1 and recycled. If the compressed and heated LPG is directly recycled or sent to the fuel supply tank, there is a risk of generating vapor in the suction portion of the compression pump, which may increase the pressure and temperature in the fuel supply tank and threaten the safety of the oil tank and the ship.

[0050] In this embodiment, in order to solve this problem, the return lines RL1 and RL2 are provided with decompression units 210 and 220 and a separator 200 for decompressing the liquefied gas, so that the liquefied gas discharged from the engine can be decompressed and gas-liquid separated before being recycled. The compressed liquefied gas is cooled by the Joule-Thomson effect while undergoing adiabatic expansion or isentropic expansion during the decompression process.

[0051] In this embodiment, the return line includes: a first return line RL1, connected from the engine to the separator; and a second return line RL2, connected from the fuel supply line at the rear end of the compression pump to the separator, and the decompression unit includes: a first decompression device 210, arranged in the first return line, to decompress the liquefied gas recovered from the engine; and a second decompression device 220, arranged in the second return line. The first decompression device and the second decompression device can be composed of an expander or an expansion valve such as a Joule-Thomson valve that performs adiabatic expansion or isentropic expansion on the compressed liquefied gas to cool it.

[0052] A reflux valve RVT and a filter 230 are provided upstream of the first decompression device of the first reflux line, and the liquefied gas discharged from the engine is introduced into the first decompression device via the reflux valve and the filter. The filter can filter lubricating oil and the like mixed in the liquefied gas discharged from the engine.

[0053] The compressed liquefied gas recirculated from the engine E through the return line RL1 is decompressed and cooled via the first decompression device 210, and then introduced into the separator 200 to be separated into gas and liquid. The liquid liquefied gas separated in the separator is merged with the rear end of the delivery pump 100 of the fuel supply line SL through the liquid line LL, and then supplied to the engine again. The gas separated in the separator is recovered to the fuel supply tank DT through the vapor line GL. A pressure regulating valve V3 for regulating the gas delivered to the fuel supply tank DT is provided on the vapor line.

[0054] The pressure at the rear end of the delivery pump is sensed, and the opening of the pressure regulating valve is adjusted according to the sensed pressure to deliver gas from the separator to the fuel supply tank, so that the pressure of the separator can be maintained 0.5 to 2 bar higher than the pressure at the rear end of the delivery pump. As described above, by adjusting the pressure of the separator, the recirculated liquefied gas separated in the separator can be delivered to the fuel supply pipeline at the rear end of the delivery pump through the liquid pipeline.

[0055] The first return pipe line RL1 and the first decompression device 210 decompress the liquefied gas discharged from the engine downstream of the fuel heater and transport it to the separator 200, and the second return pipe line RL2 and the second decompression device 220 transport the liquefied gas compressed by the compression pump to the separator 200 downstream of the fuel heater.

[0056] Thus, when the LPG mode of the engine is stopped or the LPG fuel supply is interrupted due to tripping, the remaining LPG in the engine and the fuel supply line can also be cooled by decompression and delivered to the separator. In addition, when the amount of liquefied gas fuel to be supplied to the engine is less than the minimum flow rate required by the compression pump, the liquefied gas is pumped from the compression pump at the minimum flow rate required by the compression pump, and the fuel is supplied in an amount required by the engine from the liquefied gas pumped by the compression pump, and the liquefied gas delivered in excess of the amount is recovered to the separator 200 through the second return line RL2 and the second decompression device 220 and recycled.

[0057] Since there is no need to recirculate LPG from the separator to the fuel supply line when the LPG fuel supply is interrupted, the liquefied gas recovered from the separator may also be sent to the fuel supply tank through a transfer line (not shown).

[0058] In this embodiment, a temperature regulating unit 120 for regulating the temperature of the liquefied gas is provided on the fuel supply pipeline between the delivery pump and the compression pump. The temperature regulating unit includes a fuel heater 120a and a cooler 120b.

[0059] The engine of the present embodiment is supplied with liquefied gas at a predetermined pressure and temperature as fuel. For example, in the case of the ME-LGIP engine, the fuel is supplied at 53 barg and about 35°C. LPG is about -42°C at atmospheric pressure and about 20°C at 7 bar. Therefore, if the operating pressure of the fuel supply tank is set to about 4 barg, the liquefied gas delivered from the fuel supply tank may need to be heated separately even if it is compressed by the delivery pump and the compression pump so that the fuel is supplied at the temperature required by the engine. In addition, while the operating pressure of the separator is maintained at 0.5 to 2 bar higher than the rear end pressure of the delivery pump of about 15 barg, when the amount of recirculated liquefied gas supplied to the rear end of the delivery pump through the liquid line LL via the decompression unit and the separator is large due to the large amount of liquefied gas recirculated from the engine and the like through the return line RL1 line RL1, RL2, in order to maintain the temperature required by the engine, the liquefied gas in the fuel supply line may need to be cooled. In the system of this embodiment, a temperature adjustment unit including a fuel heater and a cooler is provided between the delivery pump and the compression pump to heat or cool the liquefied gas according to circumstances, thereby adjusting the temperature of the liquefied gas to be supplied as fuel.

[0060] A fuel heater 120a and a cooler 120b are provided downstream of the confluence point of the liquid line in the rear end of the delivery pump of the fuel supply line. The fuel heater can receive steam as a heat source, and the cooler can receive liquefied gas from the fuel supply tank along the refrigerant supply line BL from the delivery pump as a refrigerant.

[0061] A temperature regulating valve V1 is provided on the refrigerant supply line BL, and a branch line BLa is provided which branches from the refrigerant supply line upstream of the cooler and is connected to the fuel supply tank, and a flow regulating valve V2 is provided on the branch line BLa. In the refrigerant supply line, a back pressure regulating valve V4 is provided downstream of the cooler to maintain back pressure.

[0062] When the flow rate of refrigerant required by the above-mentioned cooler 120b is less than the minimum flow rate required by the delivery pump 100, liquefied gas is pumped from the delivery pump at the minimum flow rate required by the delivery pump, and the temperature regulating valve V1 is adjusted to supply the cooler with the flow rate required by the cooler from the liquefied gas pumped by the delivery pump, and the flow regulating valve is adjusted to recover the liquefied gas exceeding the refrigerant flow required by the cooler to the fuel supply tank through the above-mentioned branch pipeline BL.

[0063] When the amount of liquefied gas recycled through the reflux line and the separator is large due to the low engine load, for example, when the engine load is about 10%, the temperature of the refrigerant in the refrigerant supply line introduced into the cooler can vary according to the composition of the LPG, the operating pressure of the fuel supply tank, etc., and can be in the range of about -26°C to 24°C. It can be confirmed through simulation that if the temperature of the liquefied gas in the fuel supply line introduced into the cooler is about 44°C, it can be cooled to about 32°C by the cooler.

[0064] On the other hand, the heating or cooling of the liquefied gas is adjusted according to the temperature of the liquefied gas sensed at the rear end of the cooler, and for this purpose, a first temperature sensing unit T1 is provided at the rear end of the cooler 120b in the fuel supply line to sense the temperature of the liquefied gas introduced into the compression pump 110. If the temperature of the liquefied gas sensed by the first temperature sensing unit T1 is lower than 25°C, steam is supplied to the fuel heater 120a to heat the liquefied gas, and if the temperature of the liquefied gas sensed by the first temperature sensing unit T1 is higher than 33°C, the temperature regulating valve V1 is opened and the liquefied gas pumped from the delivery pump is supplied to the cooler 120b through the above-mentioned refrigerant supply line BL to cool the liquefied gas.

[0065] A second temperature sensing unit T2 is provided at the rear end of the compression pump of the fuel supply pipeline to sense the temperature of the liquefied gas to be supplied to the above-mentioned engine through the compression pump. By heating or cooling the liquefied gas, the temperature of the liquefied gas sensed by the second temperature sensing unit can be maintained at 26 to 44°C.

[0066] As described above, in the system of the present embodiment, even if the amount of liquefied gas recovered and recycled through the return line is large, the liquefied gas stored in the fuel supply tank can be delivered to the delivery pump and used as a refrigerant in the cooler, so that even without an additional refrigerant, the temperature of the liquefied gas to be supplied as fuel can be appropriately adjusted. In addition, the recycled liquefied gas recovered from the engine is recycled to the fuel supply line via the separator, so that the lubricating oil mixed in the fuel during the process of passing through the engine can be prevented from flowing into the fuel supply tank.

[0067] The ship of this embodiment is a liquefied gas transport ship having a cargo tank (not shown) for storing and transporting liquefied gas. The ship is provided with a reliquefaction unit RS which receives boil-off gas generated from cargo in the cargo tank and reliquefies the gas.

[0068] A cooling line CL is provided which is connected from the reliquefaction section RS to the cargo hold via the fuel supply tank DT. The liquefied gas reliquefied in the reliquefaction section cools the fuel supply tank along the cooling line and is transferred to the cargo hold for storage.

[0069] That is, the fuel supply tank stores LPG at a pressure below 8 barg and supplies fuel to the engine in the ship. However, since it is installed on the deck of the ship, the temperature in the tank may become high and the pressure may rise due to external air or gas introduced from the separator, etc. However, in this embodiment, after the boil-off gas generated from the cargo hold is reliquefied in the reliquefaction unit RS, it is recovered to the cargo hold (not shown) via the fuel supply tank DT, so that the fuel supply tank is cooled by utilizing the heat of the reliquefied liquefied gas, thereby solving the above-mentioned problem.

[0070] The present invention is not limited to the above-mentioned embodiments, and various modifications or variations can be made without departing from the technical spirit of the present invention, which is obvious to those skilled in the art.

Claims

1. A fuel supply system for a liquefied gas carrier, characterized in that: include: A fuel supply line that supplies liquefied gas from a fuel supply tank disposed on the deck of the ship to an engine within the ship; a delivery pump, provided in the fuel supply pipeline, for delivering liquefied gas to be supplied from the fuel supply tank to the engine; A compression pump, disposed in the fuel supply pipeline, compressing the liquefied gas at a pressure required by the engine; a return line for recycling the liquefied gas not consumed by the engine to the upstream of the engine; A separator, arranged in the reflux pipeline, receiving the recycled liquefied gas and performing gas-liquid separation; a liquid pipeline for supplying the liquid liquefied gas separated in the separator to the rear end of the delivery pump of the fuel supply pipeline; a cooler, disposed in the fuel supply line downstream of a junction of the liquid line, for cooling the liquefied gas; as well as The refrigerant supply line branches from the fuel supply line between the junction of the delivery pump and the liquid line, and supplies all or part of the liquefied gas pumped from the delivery pump to the cooler as the refrigerant.

2. The fuel supply system for a liquefied gas carrier according to claim 1, characterized in that: The refrigerant supply line is connected to the fuel supply tank so that the liquefied gas used as the refrigerant in the cooler is recovered to the fuel supply tank.

3. The fuel supply system for a liquefied gas carrier according to claim 2, characterized in that: Also includes: a temperature regulating valve, arranged on the refrigerant supply pipeline; a branch line branched from an upstream side of the cooler in the refrigerant supply line and connected to the fuel supply tank; and A flow regulating valve is arranged on the branch pipeline. When the refrigerant flow rate required by the cooler is less than the minimum flow rate required by the delivery pump, the liquefied gas pumped by the delivery pump exceeding the refrigerant flow rate required by the cooler is recovered to the fuel supply tank through the branch line.

4. The fuel supply system for a liquefied gas carrier according to claim 3, characterized in that: Also includes: a fuel heater, disposed in the fuel supply line at the front end of the cooler, for heating the liquefied gas; and The first temperature sensing unit is provided at the rear end of the cooler in the fuel supply line and is used to sense the temperature of the liquefied gas introduced into the compression pump.

5. The fuel supply system for a liquefied gas carrier according to claim 4, characterized in that: The fuel supply pipeline further includes a second temperature sensing unit, which is disposed at the rear end of the compression pump in the fuel supply line and is used to sense the temperature of the liquefied gas to be supplied to the engine via the compression pump. When the temperature of the liquefied gas sensed by the first temperature sensing unit is lower than 25° C., steam is supplied to the fuel heater to heat the liquefied gas. When the temperature of the liquefied gas sensed by the first temperature sensing unit is 33° C. or higher, the temperature regulating valve is opened, and the liquefied gas pumped from the delivery pump is supplied to the cooler through the refrigerant supply line. The temperature of the liquefied gas sensed by the second temperature sensing unit is maintained at 26 to 44°C.

6. The fuel supply system for a liquefied gas carrier according to claim 1, characterized in that: Also includes: a vapor line for recovering the gas separated in the separator to the fuel supply tank; and A pressure regulating valve is arranged on the steam pipeline.

7. The fuel supply system for a liquefied gas carrier according to claim 6, characterized in that: The rear end pressure of the delivery pump is sensed, and the opening of the pressure regulating valve is adjusted according to the sensed pressure, so that the pressure of the separator is maintained 0.5 to 2 bar higher than the rear end pressure of the delivery pump.

8. The fuel supply system for a liquefied gas carrier according to claim 1, characterized in that: The system further comprises a decompression unit, which is disposed in the reflux line upstream of the separator and is configured to decompress the recycled liquefied gas.

9. The fuel supply system for a liquefied gas carrier according to claim 8, characterized in that: The reflux line comprises: a first return line connected from the engine to the separator; and A second return line is connected from a fuel supply line at a rear end of the compression pump to the separator.

10. The fuel supply system for a liquefied gas carrier according to claim 9, characterized in that: The decompression unit comprises: a first decompression device, disposed in the first return line, for decompressing the liquefied gas recovered from the engine; and The second pressure reducing device is arranged on the second reflux line.

11. The fuel supply system for a liquefied gas carrier according to any one of claims 1 to 10, characterized in that: Also includes: a reliquefaction unit that receives and reliquefies boil-off gas generated from a cargo tank that is provided in the ship and stores liquefied gas to be transported; and a cooling line connected from the reliquefaction unit to the cargo hold via the fuel supply tank, The liquefied gas reliquefied in the reliquefaction section cools the fuel supply tank along the cooling line and is transported to the cargo hold.

12. The fuel supply system for a liquefied gas carrier according to claim 11, characterized in that: The delivery pump and the compression pump are formed by side channel pumps.

13. A fuel supply method for a liquefied gas tanker, characterized in that: The steps include: The liquefied gas is compressed from the fuel supply tank on the deck of the ship through the fuel supply pipeline via the delivery pump and the compression pump, and then supplied to the engine in the ship as fuel; Recirculating the liquefied gas not consumed by the engine to the upstream of the engine along a return line, providing a separator in the return line to separate the recirculated liquefied gas into gas and liquid, and supplying the liquefied gas separated in the separator to a fuel supply line at the rear end of the delivery pump through a liquid line; and In the fuel supply pipeline, a cooler is arranged downstream of the confluence point of the liquid pipeline, and all or part of the liquefied gas pumped from the delivery pump is branched from the upstream of the confluence point of the liquid pipeline and supplied to the cooler as a refrigerant, thereby cooling the liquefied gas in the fuel supply pipeline.

14. The fuel supply method for a liquefied gas tanker according to claim 13, characterized in that: The liquefied gas used as a refrigerant in the cooler is recovered to the fuel supply tank. When the refrigerant flow rate required by the cooler is less than the minimum flow rate required by the delivery pump, the liquefied gas pumped by the delivery pump that exceeds the refrigerant flow rate required by the cooler is branched from the upstream of the cooler and recovered to the fuel supply tank without passing through the cooler.

15. The fuel supply method for a liquefied gas tanker according to claim 14, characterized in that: A fuel heater is provided at the front end of the cooler in the fuel supply line, sensing the temperature of the liquefied gas introduced from the rear end of the cooler to the compression pump, When the sensed temperature of the liquefied gas is lower than 25° C., steam is supplied to the fuel heater to heat the liquefied gas, and when the sensed temperature of the liquefied gas is higher than 33° C., the liquefied gas pumped from the delivery pump is branched from the upstream of the junction of the liquid pipeline and supplied to the cooler as a refrigerant to cool the liquefied gas. At the rear end of the compression pump, the temperature of the liquefied gas to be supplied to the engine is maintained at 26 to 44°C.

16. The fuel supply method for a liquefied gas tanker according to claim 15, characterized in that: The liquefied gas which is not consumed in the engine and is to be recycled along the return line is cooled by decompression and then separated into gas and liquid in the separator.

17. The fuel supply method for a liquefied gas tanker according to claim 16, characterized in that: The delivery pump and the compression pump are formed by side channel pumps.

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