KR20110074169A - Lng supplying system - Google Patents

Abstract

PURPOSE: An LNG supply system is provided to limit the rise of the inner temperature and reduce the generation of evaporation gas since LNG, which has relatively high temperature, is supplied as fuel. CONSTITUTION: An LNG supply system comprises a tank(10) and a fuel supply unit(20). The tank stores LNG. The fuel supply unit supplies the LNG which has relatively high temperature, from the tank to an engine(40). The fuel supply unit comprises an upper absorbing unit(22), a lower absorbing unit(23), an LNG supply line(24) and an evaporator(26). The upper absorbing unit and the lower absorbing unit are respectively installed to absorb LNG from the upper and lower areas in the tank. The LNG supply line is connected to supply the LNG absorbed from the upper and lower absorbing units to the engine. The evaporator is installed on the LNG supply line and evaporates the supplied LNG.

Description

LNG Supply System {LNG SUPPLYING SYSTEM}

The present invention relates to a liquefied natural gas supply system, and more particularly to a liquefied natural gas supply system for supplying liquefied natural gas stored in the liquefied natural gas storage tank as a fuel such as a ship.

Liquefied natural gas (LNG) is obtained by cooling natural gas (NG) to cryogenic temperatures (approximately -163 ° C), and its volume is reduced to approximately 1/600 of that of natural gas. It is very suitable for long distance transportation by sea.

Liquefied natural gas is stored in a liquefied natural gas storage tank equipped with a thermal insulation system, and the internal temperature increases as the external heat is continuously transmitted. On the other hand, liquefied natural gas increases in temperature as heat is continuously transferred to the outside, and thus, when the temperature at atmospheric pressure is higher than -163 ° C, vaporization occurs and boil off gas (BOG) is generated. .

When boil-off gas is generated in the liquefied natural gas storage tank, the internal pressure of the liquefied natural gas storage tank is increased.

As such, when the internal pressure of the liquefied natural gas storage tank is increased by the evaporation gas, it poses a great threat to safety. The method of storing back to the storage tank is widely used.

As a vessel using liquefied natural gas as a fuel for propulsion means, electric propulsion liquefied natural gas vessels or steam propulsion vessels have been developed and used.

These vessels have storage tanks for storing liquefied natural gas inside, such as LNG carriers, and use natural boil-off gas as fuel or forcibly vaporize liquefied natural gas stored in liquefied natural gas storage tank. To use as fuel.

Recently, a liquefied natural gas pump is installed inside a liquefied natural gas storage tank, and a method of supplying liquefied natural gas sucked from the pump to an engine and using it as a fuel has been studied.

Here, the engine may be a dual fuel diesel electric engine (DFDEE) or ME-GI engine that can use diesel and liquefied natural gas as fuel. In addition, liquefied natural gas may be directly supplied to the engine, and the liquefied natural gas may be supplied by vaporizing natural gas after pressurizing the liquefied natural gas.

However, in the conventional LNG supply system, the liquefied natural gas stored in the liquefied natural gas storage tank is thermally stratified due to convection and conduction phenomena, and the liquefied natural gas is removed from the lower liquefied natural gas to the engine. Increasing the internal temperature as supplied.

Therefore, in the related art, the internal energy is increased in the liquefied natural gas stored in the liquefied natural gas storage tank, which is a factor of increasing the amount of generated boil-off gas.

The present invention provides a liquefied natural gas supply system configured to supply relatively hot liquefied natural gas as fuel according to a temperature gradient in a liquefied natural gas storage tank.

According to an aspect of the present invention, the liquefied natural gas supply system is a liquefied natural gas supply system for supplying liquefied natural gas to the engine from the vessel to which the engine using the liquefied natural gas as a fuel, the storage for storing the liquefied natural gas A tank and a fuel supply unit for extracting a relatively high temperature liquefied natural gas from the storage tank according to the temperature gradient to supply to the engine.

The fuel supply unit uses the upper suction part and the lower suction part installed to suck the liquefied natural gas in the upper region and the lower region among the liquefied natural gas stored in the storage tank, and the liquefied natural gas sucked from the upper suction part or the lower suction part as an engine. It may include a liquefied natural gas supply line connected to supply, and a vaporizer for vaporizing the liquefied natural gas supplied and supplied on the liquefied natural gas supply line.

The upper suction part may include at least two suction pipes installed at different heights according to a temperature gradient of the stored liquefied natural gas, and suction valves respectively installed at the suction pipes.

The upper suction part may include a suction pipe whose height is varied according to a temperature gradient of the stored liquefied natural gas, and a suction valve installed at the suction pipe.

The fuel supply unit may further include a pump for supplying the liquefied natural gas.

The fuel supply unit may further include a high pressure pump installed at the front end of the vaporizer to pressurize the liquefied natural gas to a high pressure.

The fuel supply unit may further include a natural gas compressor installed at the rear end of the vaporizer.

It may further include an evaporation gas supply line for supplying the engine with the evaporated gas generated from the liquefied natural gas stored in the storage tank.

It may further include a compressor installed in the boil-off gas supply line for compressing the boil-off gas.

Therefore, the supply of liquefied natural gas, which is relatively hot, can be suppressed to increase the internal temperature, reduce the generation of boil-off gas, and consume energy for vaporizing the liquefied natural gas used as the engine fuel. Can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

Hereinafter, an embodiment of a liquefied natural gas supply system according to the present invention will be described in detail with reference to the accompanying drawings, in the following description with reference to the accompanying drawings, the same or corresponding components are given the same reference numerals and Duplicate explanations will be omitted.

1 (a) and (b) are graphs showing a temperature gradient in an liquefied natural gas storage tank and an internal temperature gradient in a liquefied natural gas storage tank after a predetermined time elapses. Here, the horizontal axis is the axis showing the temperature displacement, the vertical axis is the axis showing the water level displacement of the storage tank.

Referring to (a) of FIG. 1, the liquefied natural gas storage tank is used for vaporizing the liquefied natural gas most of the heat introduced from the outside in the initial storage of the liquefied natural gas, accordingly the temperature gradient near the gas liquid surface not big.

On the other hand, as shown in Figure 1 (b), as the liquefied natural gas storage tank over time, the heat flowing through the wall of the storage tank from the outside rises on the wall gradually accumulates in the upper storage tank, accordingly the gas-liquid surface The temperature gradient in the vicinity becomes large.

In addition, the liquefied natural gas stored in the upper region near the gas-liquid surface is increased in temperature relative to the liquefied natural gas stored in the lower region.

In addition, as in the present embodiment, when the pressure rise in the storage tank is allowed to be pressurized and operated, the temperature gradient in the storage tank becomes larger.

 Figure 2 is a schematic diagram showing a liquefied natural gas supply system according to an embodiment of the present invention. Referring to FIG. 2, the liquefied natural gas supply system may include a storage tank 10 and a fuel supply unit 20.

The liquefied natural gas supply system according to the present embodiment is a system for supplying liquefied natural gas to the engine 40 of a ship. Here, the engine 40 applied to the vessel is applied to the engine 40 using the liquefied natural gas as fuel.

To this end, the liquefied natural gas supply system includes a storage tank 10 for storing liquefied natural gas.

The storage tank 10 may be installed in a ship or the like, and is equipped with an insulation system for storing liquefied natural gas at low temperature.

The storage tank 10 may be continuously transferred to the outside heat, the internal temperature may be increased by the heat generated by the flow of the liquefied natural gas or the operation of the pump therein.

At this time, the storage tank 10 is the temperature of the upper region of the stored liquefied natural gas is increased to a relatively high temperature compared to the lower region, the liquefied natural gas is vaporized near the gas-liquid surface as heat is continuously introduced from the outside and the evaporated gas Occurs.

The liquefied natural gas stored in the upper region of the liquefied natural gas stored in the storage tank 10 has a relatively high temperature according to a temperature gradient, and the relatively high temperature liquefied natural gas is taken out and supplied to the engine 40 to store the storage tank 10. Heat can be prevented from being accumulated, the temperature of the liquefied natural gas stored in the storage tank 10 can be kept uniform, and the generation of boil-off gas can be suppressed.

To this end, the present embodiment includes a fuel supply unit 20 for extracting a relatively high temperature liquefied natural gas in accordance with the temperature gradient of the liquefied natural gas stored in the storage tank 10 to supply to the engine 40.

The fuel supply unit 20 has an upper suction part 22 and a lower suction part 23 installed to suck liquefied natural gas in the upper region and the lower region, respectively, among the liquefied natural gases stored in the storage tank 10.

In addition, the fuel supply unit 20 has a liquefied natural gas supply line 24 connected to the upper suction unit 22 and the lower suction unit 23.

The liquefied natural gas supply line 24 is connected to supply the liquefied natural gas sucked from the upper suction part 22 or the lower suction part 23 to the engine 40.

Here, the upper suction part 22 may include an upper suction pipe 22a for sucking the liquefied natural gas in the upper region, and an upper suction valve 22b for controlling the opening and closing of the upper suction pipe 22a. .

On the other hand, the liquefied natural gas is lowered as the consumption increases, and thus the upper suction pipe (22a) can also be installed to suck the liquefied natural gas is lowered.

To this end, the upper suction pipe 22a may be installed in at least two branches with different heights according to the temperature gradient of the liquefied natural gas stored in the upper region.

That is, the upper suction pipe 22a may be installed in a plurality of branches with a predetermined height difference in the upper region of the storage tank 10.

In addition, the upper suction part 22 may be provided with an upper suction valve 22b at each branched upper suction pipe 22a, and the upper suction valve 22b is controlled to store the upper suction valve 22b in the upper region of the liquefied natural gas. The liquefied natural gas at a relatively high temperature can be sucked first.

In the present embodiment, the upper suction part 22 is configured to suck the liquefied natural gas by varying the height by the suction pipe 22a branched into a plurality of pieces at different heights, but the present invention is not limited thereto. It may include a suction pipe is variable in height depending on the temperature gradient of the stored liquefied natural gas.

To this end, the upper suction part 22 is installed as a corrugated pipe that can vary the height of the suction pipe, and is installed so that the buoyant body is always locked at a constant level from the gas-liquid surface by buoyancy, etc. by installing a buoyant body on the upper part of the corrugated pipe. It is also possible.

As described above, the fuel supply unit 20 may extract the liquefied natural gas in the upper region by using the upper suction unit 22 and supply it to the engine 40.

Meanwhile, the lower suction part 23 includes a lower suction pipe 23a for sucking liquefied natural gas in the lower region, and a lower suction valve 23b for controlling the opening and closing of the lower suction pipe 23a. By using the lower suction part 23, the liquefied natural gas stored in the lower region of the storage tank 10 may be extracted and supplied to the engine 40.

In this way, the liquefied natural gas supply line 24 for supplying liquefied natural gas to the engine 40 may be provided with a vaporizer 26 for vaporizing the liquefied natural gas supplied to the engine 40.

In addition, the fuel supply unit 20 may further include a pump 25 for pumping and supplying liquefied natural gas. As such, the fuel supply unit 20 may supply a sufficient amount of liquefied natural gas required by the engine 40 by the pump 25, and pressurize and supply the liquefied natural gas supplied to the vaporizer 26. have.

In this embodiment, the pump 25 may be installed in the liquefied natural gas supply line 24 and may compress the liquefied natural gas stored in the storage tank 10 to a high pressure and supply the same to the vaporizer 26.

The vaporizer 26 is a device for vaporizing a liquid liquefied natural gas into a natural gas in a gaseous state, and may include a heating unit for heating the liquefied natural gas.

In addition, the liquefied natural gas supply line 24 may be provided with a control valve 29 for adjusting the flow rate of the liquefied natural gas supplied by the pump 25.

On the other hand, the storage tank 10 is designed in consideration of the strength that can withstand the pressure rise of the boil-off gas generated by the liquefied natural gas is vaporized, for this purpose, the outer wall of the storage tank 10 is designed to be thick or on the outer wall or inner wall Reinforcement can be added to increase strength.

Such, the storage tank 10 is when the stored liquefied natural gas is evaporated to generate the evaporated gas, the internal pressure is increased to cause a safety problem, it is made to process the evaporated gas.

In this embodiment, the boil-off gas generated from the liquefied natural gas may be supplied to the engine 40 and used as fuel.

To this end, the storage tank 10 may be further provided with an evaporative gas supply line 30 connected to the engine 40.

In the boil-off gas supply line 30, a compressor 32 for compressing the boil-off gas at a high pressure may be installed.

In addition, the boil-off gas supply line 30 may be further provided with a pressure control valve 34 for controlling the supply of boil-off gas compressed by the compressor (32).

Looking at the operation of the liquefied natural gas supply system configured as described above are as follows.

First, the liquefied natural gas cooled to cryogenic temperature is stored in a storage tank 10 of a ship to which an engine 40 using liquefied natural gas is used as fuel.

In addition, the vessel extracts the liquefied natural gas having a relatively high temperature according to the temperature gradient among the liquefied natural gas stored in the storage tank 10 and uses it as the fuel of the engine 40.

At this time, the liquefied natural gas stored in the storage tank 10 has a relatively high temperature in the upper region adjacent to the gas-liquid surface where the boil-off gas is generated, compared to the lower region, and thus is stored as the liquefied natural gas is removed and used as fuel. The internal temperature of the tank 10 can be kept low.

The liquefied natural gas of the relatively high temperature removed from the storage tank 10 is supplied to the vaporizer 26 via the control valve 29.

The vaporizer 26 heats the liquefied natural gas, converts it into gaseous natural gas, and supplies the gas to the engine 40.

At this time, since the liquefied natural gas is supplied to the vaporizer 26 with a relatively high temperature, energy for vaporizing it may be reduced.

On the other hand, the storage tank 10, the amount of heat flowing in as time passes, thereby evaporation occurs in the gas-liquid surface of the stored liquefied natural gas and the evaporation gas is generated.

This boil-off gas is supplied as fuel to the engine 40 by the boil-off gas supply line 30.

At this time, the boil-off gas is supplied to the engine 40 in a state of being compressed at high pressure by the compressor 32 installed in the boil-off gas supply line 30.

In this embodiment, the liquefied natural gas supply system may be applied to all vessels having a storage tank 10 for storing liquefied natural gas therein and an engine 40 using the same as a fuel, for example, a liquefied natural gas carrier or It can be applied to various structures such as Floating, Production, Storage and Offloading (FPSO) or Floating Storage and Regasification Unit (FSRU), as well as various transport vessels and vessels such as LNG Regasification Vessels (RVs).

In this embodiment, the engine 40 is described as directly burning the natural gas vaporized in the vaporizer 26 by supplying it to the engine 40, but is not limited to this, the natural gas is compressed and supplied as shown in FIG. It is also possible.

Figure 3 is a schematic diagram showing a liquefied natural gas supply system according to another embodiment of the present invention.

Referring to FIG. 3, the fuel supply unit 20 may further include a natural gas compressor 28 installed at the rear end of the vaporizer 26.

The natural gas compressor 28 may increase the combustion efficiency by compressing the natural gas vaporized by the vaporizer 26 and supplying it to the engine 40.

In this embodiment, the fuel supply unit 20 is described as one pump 25 is installed, but the number or installation position of the pump 25 is not limited and may be variously changed.

For example, the high pressure pump 27 may be further installed at the front end of the vaporizer 26, and it is also possible to pressurize the liquefied natural gas supplied to the vaporizer 26 to a high pressure.

Here, although the high pressure pump 27 is described as being installed at the front end of the vaporizer 26, the position where the high pressure pump 27 is installed is not limited by the present embodiment and the control valve 29 is installed in the pump 25 It is also possible to pressurize and supply the liquefied natural gas which is pressurized from the pressure to a higher pressure.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be understood that the invention may be varied and varied without departing from the scope of the invention.

1 (a) and (b) are graphs showing a temperature gradient inside an liquefied natural gas storage tank and a temperature gradient inside a liquefied natural gas storage tank after a predetermined time elapses.

Figure 2 is a schematic diagram showing a liquefied natural gas supply system according to an embodiment of the present invention.

Figure 3 is a schematic diagram showing a liquefied natural gas supply system according to another embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

10: storage tank 20: fuel supply unit

22: upper suction part 22a: upper suction pipe

22b: Upper suction valve 23: Lower suction part

23a: lower suction pipe 23b: lower suction pipe

24: LNG supply line 25: pump

26: carburetor 28: natural gas compressor

29: control valve 30: boil-off gas supply line

32: compressor 34: pressure control valve

40: engine

Claims (9)

As a liquefied natural gas supply system for supplying liquefied natural gas to the engine from a vessel to which an engine using liquefied natural gas is applied, A storage tank for storing liquefied natural gas, Liquefied natural gas supply system, characterized in that it comprises a fuel supply unit for removing the relatively high temperature liquefied natural gas from the storage tank according to the temperature gradient to supply to the engine. The method of claim 1, wherein the fuel supply unit An upper suction part and a lower suction part installed to suck liquefied natural gas in the upper region and the lower region among the liquefied natural gas stored in the storage tank; A liquefied natural gas supply line connected to supply liquefied natural gas sucked from the upper suction part or the lower suction part to the engine; Liquefied natural gas supply system comprising a vaporizer for vaporizing the liquefied natural gas is installed on the liquefied natural gas supply line. The method according to claim 2, The upper suction unit includes at least two suction pipes installed at different heights according to a stored temperature gradient of liquefied natural gas, Liquefied natural gas supply system characterized in that it comprises a suction valve respectively installed in the suction pipe. The method according to claim 2, The upper suction part and the suction pipe is variable in height according to the temperature gradient of the stored liquefied natural gas, Liquefied natural gas supply system comprising a suction valve installed in the suction pipe. The method according to claim 2, The fuel supply unit liquefied natural gas supply system further comprises a pump for supplying the liquefied natural gas. The method according to claim 5, The fuel supply unit is a liquefied natural gas supply system, characterized in that it further comprises a high-pressure pump is installed in the front end of the vaporizer to pressurize the liquefied natural gas at high pressure. The method according to claim 2, The fuel supply unit liquefied natural gas supply system further comprises a natural gas compressor installed in the rear end of the vaporizer. The method according to any one of claims 1 to 7, Liquefied natural gas supply system, characterized in that it further comprises a boil-off gas supply line for supplying the boil-off gas generated from the liquefied natural gas stored in the storage tank to the engine. The method according to claim 8, Liquefied natural gas supply system characterized in that it further comprises a compressor installed in the boil-off gas supply line to compress the boil-off gas.

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