KR101333947B1 - A treatment system of liquefied natural gas - Google Patents

Abstract

An LNG treatment system according to one embodiment of the present invention includes: an LNG feeding line being connected from an LNG storage tank to an LNG demander; a pump being installed on the LNG feeding line and pressurizing LNG discharged from the LNG storage tank; a boil-off gas compressor pressurizing boil-off gas generated in the LNG storage tank; an LNG heat exchanger being installed on the LNG feeding line between the LNG demander and the pump, and heat-exchanging the pressurized boil-off gas with the LNG fed from the pump; a boil-off gas heat exchanger being installed at the upper stream of the boil-off gas compressor and heat-exchanging the boil-off gas generated in the LNG storage tank with the boil-off gas pressurized in the boil-off gas compressor; and a decompression apparatus decompressing the boil-off gas heat-exchanged with the LNG in the LNG heat exchanger, wherein the LNG and the decompressed boil-off gas passing through the LNG feeding line is fed to the pump. The LNG treatment system according to the present invention pressurizes the boil-off gas generated in the LNG storage tank with external heat penetration, and then feeds the boil-off gas to a low-pressure LNG demander, or feeds the boil-off gas to a high-pressure LNG demander through the pump with liquefying and decompressing the boil-off gas after multi-stage pressurization, thereby preventing the boil-off gas from being thrown away.

Description

LNG Treatment System {A Treatment System of Liquefied Natural Gas}

The present invention relates to an LNG processing system.

A ship is a means of transporting large quantities of minerals, crude oil, natural gas, or more than a thousand containers. It is made of steel and buoyant to float on the water surface. ≪ / RTI >

Such a vessel generates thrust by driving the engine. In this case, the engine uses gasoline or diesel to move the piston so that the crankshaft is rotated by the reciprocating motion of the piston, so that the shaft connected to the crankshaft is rotated to drive the propeller It was common.

In recent years, however, LNG fuel supply systems for driving an engine using LNG as a fuel have been used in an LNG carrier carrying Liquefied Natural Gas (LNG) It is also applied to other ships.

Generally, it is known that LNG is a clean fuel and its reserves are more abundant than petroleum, and its usage is rapidly increasing as mining and transfer technology develops. This LNG is generally stored in a liquid state at a temperature of -162 ° C. or below under 1 atm. The volume of liquefied methane is about one sixth of the volume of methane in a gaseous state, The specific gravity is 0.42, which is about one half of that of crude oil.

However, the temperature and pressure required to drive the engine may be different from the state of the LNG stored in the tank. Therefore, in recent years, research and development have been made on the technology of controlling the temperature and pressure of the LNG stored in the liquid state and supplying the engine to the engine.

In addition, when LNG is stored in the liquid phase, as the heat penetrates into the tank, some LNG is vaporized to generate boil off gas (BOG). In the past, the boil off gas (BOG) was lowered to remove the risk of damage to the tank. It was simply discharged to the outside. Recently, however, the necessity of development has gradually increased for the utilization of re-liquefaction of the boil-off gas generated in the tank and supply to the engine.

The present invention was created to solve the problems of the prior art as described above, an object of the present invention is to provide a LNG processing system by compressing, liquefying, decompressing the boil-off gas to supply to the LNG demand destination by using the boil-off gas It is to provide.

It is also an object of the present invention to provide an LNG processing system that can easily liquefy the boil-off gas, and supply the boil-off gas to the pump by reducing the boil-off gas.

An LNG processing system according to an embodiment of the present invention includes an LNG supply line connected from an LNG storage tank to an LNG consumer site; A pump provided on the LNG supply line for pressurizing the LNG discharged from the LNG storage tank; An evaporative gas compressor for pressurizing the evaporative gas generated in the LNG storage tank; An LNG heat exchanger provided on the LNG supply line between the LNG consumer and the pump for heat-exchanging the LNG supplied from the pump with the pressurized evaporated gas; An evaporative gas heat exchanger installed upstream of the evaporative gas compressor for exchanging heat between the evaporated gas generated in the LNG storage tank and the evaporated gas pressurized in the evaporative gas compressor; And an evaporation gas decompressor for decompressing the evaporated gas heat exchanged with the LNG in the LNG heat exchanger, wherein the LNG and the decompressed evaporated gas through the LNG supply line are supplied to the pump.

Here, the present invention further comprises an evaporation gas supply line connected from the LNG storage tank to the boil-off gas heat exchanger, the boil-off gas compressor, the boil-off gas heat exchanger, the LNG heat-exchanger, the boil-off gas decompressor. do.

In addition, the present invention is provided downstream of the boil-off gas reducer and the LNG supply line between the LNG storage tank and the pump, LNG is introduced from the LNG storage tank, the boil-off gas is introduced from the boil-off gas reducer Characterized in that it further comprises a temporary storage tank for discharging the LNG to the pump.

In addition, the temporary storage tank is characterized in that the boil-off gas discharged from the boil-off gas decompressor mixed with LNG discharged from the LNG storage tank and liquefied and supplied to the pump.

In addition, the boil-off gas decompressor LNG processing system, characterized in that consisting of a multi-stage gas-liquid separator.

In addition, the boil-off gas decompressor, characterized in that to reduce the boil-off gas to 10bar to 20bar.

In addition, the boil-off gas pressure reducer is characterized in that the flash gas discharge line is discharged is formed.

Further, the present invention is characterized in that an evaporation gas re-liquefaction line branched from the evaporation gas heat exchanger to the LNG storage tank is branched from the evaporation gas heat exchanger to the LNG heat exchanger on the evaporation gas supply line, And a liquefaction device for liquefying the evaporation gas.

According to the present invention, there is provided an evaporative gas re-liquefaction line provided on an upstream side of the evaporation gas decompressor branched on the evaporation gas supply line, and provided on the evaporation gas re-liquefaction line, And further comprising:

In addition, the LNG demand destination connected to the LNG supply line is characterized in that the high pressure LNG demand destination.

In addition, the boil-off gas compressor is provided with a plurality of pressurizing the boil-off gas in multiple stages, one end is connected between the plurality of boil-off gas compressor on the boil-off gas supply line and low pressure supplying the pressurized boil-off gas to low pressure LNG demand destination Further comprising a boil-off gas supply line.

LNG processing system according to the present invention, by compressing the boil-off gas generated in the LNG storage tank by external heat penetration to supply to low-pressure LNG demand, or liquefied, reduced pressure after multi-stage compression to supply to high-pressure LNG demand through the pump, The boil-off gas can be prevented from being discarded.

In addition, the LNG processing system according to the present invention can pressurize the boil-off gas with the boil-off gas compressor so that the boil-off gas can be easily liquefied, and reduce the pressure of the boil-off gas to supply the pump to prevent damage to the pump.

1 is a conceptual diagram of a conventional LNG processing system.
2 is a conceptual diagram of an LNG processing system according to a first embodiment of the present invention.
3 is a conceptual diagram of an LNG processing system according to a second embodiment of the present invention.
4 is a conceptual diagram of an LNG processing system according to a third embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a conceptual diagram of a conventional LNG processing system.

As shown in FIG. 1, the conventional LNG processing system 1 includes an LNG storage tank 10, an LNG demand destination 20, a pump 30, and an LNG heat exchanger 40. In this case, the LNG demand source 20 may be a gas fuel engine that is a high pressure LNG source or a dual fuel engine that is a low pressure LNG source, and the pump 30 may include a boosting pump 31 and a high pressure pump 32. It can be configured to include.

Hereinafter, the LNG may be used to encompass not only a liquid state NG but also a NG state such as a supercritical state for the sake of convenience. The evaporation gas may include not only gaseous state evaporation gas but also liquefied evaporation gas Can be used as a meaning.

The conventional LNG processing system 1 extracts liquid LNG from the LNG storage tank 10 and pressurizes it through the boosting pump 31 and the high pressure pump 32, and then, in the LNG heat exchanger 40, to glycol water or the like. The method of heating and supplying to the LNG demand destination 20 was used.

In this case, however, only the liquid LNG stored in the LNG storage tank 10 is used. Therefore, the evaporation gas naturally generated in the LNG storage tank 10 by the external heat penetration is used to lower the internal pressure of the LNG storage tank 10 And discharged to the outside along the evaporation gas discharge line (11). Therefore, the conventional LNG processing system 1 does not utilize any boil-off gas, there is a problem that energy waste occurs.

2 is a conceptual diagram of an LNG processing system according to a first embodiment of the present invention.

2, the LNG processing system 2 according to the first embodiment of the present invention includes an LNG storage tank 10, a high-pressure LNG consumer 20a, a low-pressure LNG consumer 20b, a pump 30, The LNG heat exchanger 40, the evaporative gas compressor 50, the evaporative gas heat exchanger 60, the evaporative gas pressurizing means 70, the evaporative gas decompressor 80, and the temporary storage tank 90. In the first embodiment of the present invention, the LNG storage tank 10, the pump 30, and the like are denoted by the same reference numerals as those in the conventional LNG processing system 1, .

The LNG storage tank 10 stores LNG to be supplied to the LNG demanders 20a and 20b. The LNG storage tank 10 must store the LNG in a liquid state, and the LNG storage tank 10 may have a pressure tank form.

The LNG storage tank 10 includes an outer tank (not shown), an inner tank (not shown), and a heat insulating portion (not shown). The outer tank is a structure of the outer wall of the LNG storage tank 10, and may be formed of steel, and may have a polygonal cross section.

The inner tank is provided inside the outer tank, and can be supported and supported inside the outer tank by a support (not shown). At this time, the support may be provided on the lower end of the inner tank, and may be provided on the side of the inner tank for suppressing lateral movement of the inner tank.

The inner tank can be made of stainless steel and can be designed to withstand pressures from 5 bar to 10 bar (6 bar, for example). The reason for designing the inner tank so as to withstand such a constant pressure is that the inner pressure of the inner tank may be increased as the LNG contained in the inner tank is evaporated to generate the evaporative gas.

A baffle (not shown) may be provided in the inner tank. The baffle means a plate in the form of a lattice. As the baffle is installed, the pressure inside the tank can be evenly distributed to prevent the tank pressure from being concentrated to a part of the tank.

The heat insulating portion is provided between the inner tank and the outer tank and can prevent the external heat energy from being transmitted to the inner tank. At this time, the heat insulating portion may be in a vacuum state. By forming the thermal insulation in a vacuum, the LNG storage tank 10 can withstand higher pressures more efficiently compared to conventional tanks. For example, the LNG storage tank 10 can sustain a pressure of 5 to 20 bar through the vacuum insulation.

As described above, the present embodiment can minimize the generation of boil-off gas by using a pressure tank-type LNG storage tank 10 having a vacuum insulated portion between the outer tank and the inner tank, and even if the internal pressure rises, the LNG storage tank. It is possible to prevent problems such as breakage of (10) from occurring.

In this embodiment, the evaporation gas generated in the LNG storage tank 10 is supplied to the evaporation gas compressor 50 and used for heating the LNG, or the evaporation gas is supplied to the pump 30 by pressurizing, liquefying, And is used as the fuel for the high-pressure LNG consumer 20a, the evaporation gas can be efficiently used.

The LNG demanders 20a and 20b are driven through the LNG supplied from the LNG storage tank 10 to generate power. In this case, the LNG demand destination 20a, 20b includes a high pressure LNG demand destination 20a and a low pressure LNG demand destination 20b, the high pressure LNG demand destination 20a may be a MEGI LNG destination, and the low pressure LNG demand destination 20b is a dual fuel LNG. It can be a demand source.

As a piston (not shown) inside the cylinder (not shown) reciprocates by the combustion of the LNG, the LNG demanders 20a and 20b rotate the crankshaft (not shown) connected to the piston, The shaft (not shown) to be connected can be rotated. Therefore, as the propeller (not shown) connected to the shaft rotates when the LNG consumers 20a and 20b are driven, the hull can advance or backward.

Of course, in this embodiment, the LNG demanders 20a and 20b may be LNG demanders for driving the propeller, but they may be LNG demanders for power generation or LNG demanders for generating other power. That is, the present embodiment does not specifically limit the types of the LNG demanders 20a and 20b. However, the LNG demanders 20a and 20b may be internal combustion engines that generate driving force by combustion of the LNG.

The high pressure LNG demand destination 20a generates power by receiving LNG in a supercritical state (30 ° C. to 60 ° C., 200 bar to 400 bar) from the LNG heat exchanger 40, while the low pressure LNG demand destination 20 b is an evaporated gas. The driving force can be obtained by receiving the boil-off gas pressurized by the compressor 50. The state of the LNG or the evaporation gas supplied to the high-pressure LNG consumer 20a and the low-pressure LNG consumer 20b may vary depending on the state required by the LNG consumers 20a and 20b.

In the case of low-pressure LNG demand site (20b), it may be a dual-fuel LNG demand place where LNG and oil are not mixed and LNG or oil is selectively supplied. This is to prevent the two materials having different combustion temperatures from being mixed and supplied, thereby preventing the efficiency of the low pressure LNG demand destination 20b from falling.

An LNG supply line 21 for delivering LNG may be installed between the LNG storage tank 10 and the high pressure LNG demand destination 20a, and the LNG supply line 21 may include a pump 30, an LNG heat exchanger 40, and the like. Is provided so that the LNG can be supplied to the high pressure LNG demand destination (20a).

At this time, the fuel supply valve (not shown) is installed in the LNG supply line 21, the supply amount of LNG can be adjusted according to the opening degree of the fuel supply valve.

The pump 30 is provided on the LNG supply line 21 and pressurizes the LNG discharged from the LNG storage tank 10. The pump 30 may include a boosting pump 31 and a high pressure pump 32.

The boosting pump 31 may be provided on the LNG supply line 21 between the LNG storage tank 10 and the high pressure pump 32 or in the LNG storage tank 10, and is sufficient for the high pressure pump 32. A positive amount of LNG is supplied to prevent cavitation of the high pressure pump 32.

Also, the boosting pump 31 can pressurize the LNG from the LNG storage tank 10 to a pressure of several to several tens of bar, and the LNG through the boosting pump 31 can be pressurized to 1 to 25 bar.

The LNG stored in the LNG storage tank 10 is in a liquid state. At this time, the boosting pump 31 may pressurize the LNG discharged from the LNG storage tank 10 to slightly increase the pressure and the temperature, and the LNG pressurized by the boosting pump 31 may still be in a liquid state.

The high pressure pump 32 pressurizes the LNG discharged from the LNG storage tank 10 to a high pressure so as to be supplied to the high pressure LNG demand destination 20a. The LNG is discharged at a pressure of about 10 bar from the LNG storage tank 10 and then pressurized primarily by the boosting pump 31, and the high pressure pump 32 receives the liquid LNG pressurized by the boosting pump 31. It is pressurized secondary and it supplies to the LNG heat exchanger 40.

At this time, the high pressure pump 32 pressurizes the LNG to the high pressure LNG demand destination 20a by supplying the pressure required by the high pressure LNG demand destination 20a, for example, 200 bar to 400 bar, so that the high pressure LNG demand destination 20a is driven through the LNG. Can be produced.

The high pressure pump 32 is capable of phase-changing the LNG discharged from the boosting pump 31 to a supercritical state having a higher temperature and a higher pressure than the LNG at a high pressure have. At this time, the temperature of the supercritical LNG may be lower than -20 ° C, which is relatively higher than the critical temperature.

Or the high-pressure pump 32 can pressurize the LNG in a liquid state to a super-cooled liquid state by pressurizing it with a high pressure. Here, the supercooled liquid state means that the pressure of the LNG is higher than the critical pressure and the temperature is lower than the critical temperature.

Specifically, the high-pressure pump 32 pressurizes the liquid LNG discharged from the boosting pump 31 to a high pressure of 200 to 400 bar so that the temperature of the LNG becomes lower than the critical temperature, Phase change. Here, the temperature of the LNG in the subcooled liquid state may be -140 캜 to -60 캜, which is relatively lower than the critical temperature.

The evaporative gas compressor (50) pressurizes the evaporative gas generated in the LNG storage tank (10). The evaporative gas compressor 50 can pressurize the evaporated gas generated in the LNG storage tank 10 and discharged at a pressure of about 10 bar to supply the LNG heat exchanger 40 to be described later.

The plurality of evaporation gas compressors (50) can pressurize the evaporation gas at multiple stages. For example, three evaporation gas compressors 50 may be provided so that the evaporation gas is pressurized in three stages. At this time, the evaporation gas pressurized at the first stage is supplied to the low pressure LNG consumer 20b through the low pressure evaporation gas supply line 23 .

The low pressure boil-off gas supply line 23 may be connected between the plurality of boil-off gas compressors 50 on the boil-off gas supply line 22 and supply pressurized boil-off gas to the low pressure LNG demand destination 20b. For example, when three evaporative gas compressors 50 are provided, the low-pressure evaporative gas supply line 23 may be connected to the downstream of the first evaporative gas compressor 50 based on the flow of the evaporative gas. Accordingly, the evaporated gas pressurized in the first evaporative gas compressor 50 can be branched and supplied after the low-pressure LNG consumer 20b or the second evaporative gas compressor 50, respectively.

(Not shown) may be provided on the connection point between the evaporation gas supply line 22 and the low-pressure evaporation gas supply line 23, and the evaporation gas supply valve may be connected to the low-pressure LNG demand source 20b through evaporation Gas flow rate or the flow rate of the evaporation gas supplied to the LNG heat exchanger 40 through the third evaporative gas compressor 50, or may be a three-way valve.

Between the plurality of evaporative gas compressors 50, an evaporative gas cooler (not shown) may be provided. When the evaporation gas is pressurized by the evaporation gas compressor 50, since the temperature may also rise with the pressure increase, this embodiment can lower the temperature of the evaporation gas again by using the evaporation gas cooler. The evaporative gas cooler may be installed in the same number as the evaporative gas compressor 50, and each evaporative gas cooler may be provided downstream of each evaporative gas compressor 50.

The evaporation gas compressor 50 pressurizes the evaporation gas in order to increase the liquefaction efficiency of the evaporation gas. The boil-off gas has an elevated boiling point when the pressure rises, which means that it can be liquefied even at relatively high temperatures. Therefore, this embodiment can increase the pressure of the evaporation gas to the evaporation gas compressor 50, so that the evaporation gas can be easily liquefied. At this time, the evaporated gas discharged from the most downstream evaporative gas compressor (50) may have a pressure of 30 to 60 bar (45 bar, for example). However, the evaporated gas discharged from the evaporative gas compressor 50 located upstream of the low-pressure evaporative gas supply line 23 can have a pressure required by the low-pressure LNG consumer 20b and can be supplied to the low-pressure LNG consumer 20b May be between 1 and 50 bar.

When the evaporated gas generated in the LNG storage tank 10 is continuously supplied to the evaporation gas compressor 50 directly, there is a risk of damage due to the evaporation gas temperature. Therefore, the evaporation gas generated in the LNG storage tank 10 It is necessary to increase the temperature to increase the suitability of the state of the evaporated gas when it is used in the evaporative gas compressor (50).

The evaporation gas heat exchanger 60 is installed in the evaporation gas supply line 22 upstream of the evaporation gas compressor 50 to heat exchange the evaporation gas so as to enhance the stability of the evaporation gas compressor 50, Exchanges the evaporated gas generated in the LNG storage tank 10 with the evaporated gas pressurized in the evaporative gas compressor 50.

That is, the evaporated gas discharged from the LNG storage tank 10 is pressurized in multiple stages in the evaporative gas compressor 50 and is recovered to the evaporative gas heat exchanger 60, and the evaporated gas newly supplied from the LNG storage tank 10 Exchanged in the evaporated gas heat exchanger 60 with the recovered evaporated gas. Accordingly, the evaporated gas to be introduced into the evaporated gas heat exchanger 60 can be heated by the evaporated gas which is pressurized by the evaporated gas compressor 50 in the evaporated gas heat exchanger 60 and the temperature is raised. Therefore, whenever the evaporated gas generated in the LNG storage tank 10 is supplied to the evaporative gas compressor 50, the heat of the evaporated gas is not directly affected by the temperature of the evaporated gas generated in the LNG storage tank 10, So that the breakage due to the temperature of the evaporation gas can be reduced.

The boil-off gas pressurizing means 70 may be provided downstream of the boil-off gas compressor 50 to pressurize the boil-off gas once more to raise the pressure. For example, the pressure of the boil-off gas may be pressurized to 45 bar to 60 bar. When the evaporation gas is pressurized by the evaporation gas pressurizing means 70, the breaking point is raised, so that liquefaction can be facilitated and the heat exchange efficiency can be improved.

The LNG heat exchanger 40 is provided on the LNG supply line 21 between the high pressure LNG consumer 20a and the pump 30 and exchanges the LNG supplied from the pump 30 with the pressurized evaporated gas. The pump 30 for supplying the LNG to the LNG heat exchanger 40 may be the high pressure pump 32 and the LNG heat exchanger 40 may be configured to discharge the LNG in the supercooled or supercritical state from the high pressure pump 32 Exchanged with the evaporation gas while maintaining the pressure of 200 bar to 400 bar, and converted into LNG having a supercritical state of 30 to 60 degrees, and then supplied to the high-pressure LNG consumer 20a.

The LNG heat exchanger (40) can heat the LNG using the evaporated gas pressurized in the evaporative gas compressor (50). The LNG is heated by receiving heat from the evaporation gas, and thereby the high-pressure LNG consumer 20a is heated by being heated by the evaporation gas compressor 50. The LNG is cooled by supplying heat to the LNG, The temperature can be raised to the required temperature.

Of course, since the heat source included in the evaporated gas can vary depending on the amount of evaporated gas generated in the LNG storage tank 10, the present embodiment can be applied to the LNG storage tank 10, A heater (not shown) may be provided. At this time, the heater may be provided on the LNG supply line 21 downstream of the LNG heat exchanger 40, and the LNG may be heated using electric energy or using steam or glycol water.

The evaporation gas decompressor (80) reduces the evaporated gas heat exchanged with the LNG. For example, the boil-off gas decompressor 80 may reduce the boil-off gas to 10 bar to 20 bar, and the boil-off gas may be reduced to 1 bar when the boil-off gas is liquefied and transferred to the LNG storage tank 10.

Here, the boil-off gas is cooled by heat exchange with the LNG in the LNG heat exchanger 40, but the pressure may maintain the discharge pressure discharged from the boil-off gas compressor 50. Since the liquefied evaporated gas can be supplied to the high-pressure LNG consumer 20a by the high-pressure pump 32, the evaporated gas that maintains the discharge pressure in the evaporated gas compressor 50 is supplied to the high-pressure pump 32 The excessive pressure may be applied to the inflow end of the high pressure pump 32, which may damage the high pressure pump 32.

Therefore, in this embodiment, the pressure of the evaporation gas is lowered by using the evaporation gas decompressor 80 so that the evaporation gas pressure at the inlet of the high pressure pump 32 is maintained within a range that does not cause a problem in driving the high pressure pump 32 .

Since the evaporation gas decompressor 80 may be provided downstream of the LNG heat exchanger 40, at least a part of the evaporation gas flowing into the evaporation gas decompressor 80 may be in a liquefied state. Therefore, the evaporated gas in the liquid state, which is reduced in pressure by the evaporation gas decompressor 80, can be supplied to the high pressure LNG consumer 20a together with the LNG introduced into the high pressure pump 32 through the boosting pump 31.

The evaporation gas decompressor 80, although not shown, may be provided in a plurality of stages to reduce the pressure of the evaporation gas at multiple stages. At this time, the pressure of the evaporated gas discharged from the evaporative gas decompressor 80 located at the downstream may be 10 to 20 bar (for example, 15 bar).

The evaporation gas decompressor 80 may be, for example, a gas-liquid separator. The gas-liquid separator separates the gas and the liquid so that the gas can be removed from the evaporation gas, so that the flash gas can be discharged as an inert gas (for example, N 2), which is the main component of the evaporation gas . When the inert gas, which is the main component of the boil-off gas, is discharged to the flash gas, not only the generation rate of the boil-off gas is reduced, but also the ratio of methane (methane number) is increased, thereby improving the quality of LNG.

The flash gas may be generated when the evaporation gas is decompressed by the evaporation gas decompressor 80. Since the flash gas may cause a cavitation phenomenon in the high-pressure pump 32 when the flash gas flows into the high-pressure pump 32, the flash gas is connected to the evaporation gas decompressor 80 at one end, And a flash gas discharge line 81 for discharging the flash gas to the outside. Since the plurality of evaporative gas decompressors 80 may be provided, the flash gas discharge line 81 may be provided in at least one evaporative gas decompressor 80.

The temporary storage tank 90 is provided in the LNG supply line 21 downstream of the evaporative gas decompressor 80 and between the LNG storage tank 10 and the pump 30 and the LNG is supplied from the LNG storage tank 10 And the evaporation gas is introduced from the evaporation gas decompressor 80 to discharge the LNG to the high-pressure pump 32.

The temporary storage tank 90 is configured to liquefy the evaporated gas discharged from the evaporation gas decompressor 80 by heat exchange with the LNG discharged from the LNG storage tank 10 to discharge the LNG through the LNG recovery line 24, The evaporated gas liquefied in the heat exchanger (40) can be discharged to the high-pressure pump (32). Here, the LNG recovery line 24 is a line connected between the temporary storage tanks 90 and the LNG storage tanks 10 to recover the liquefied evaporated gas from the temporary storage tanks 90 to the LNG storage tanks 10 .

The evaporation gas supply line 22 of the present embodiment is provided with the evaporation gas heat exchanger 60, the evaporation gas compressor 50, the evaporation gas heat exchanger 60, the LNG heat exchanger 40, The gas pressure reducer 80, and the temporary storage tank 90. The evaporation gas is generated in the LNG storage tank 10 and discharged along the evaporation gas supply line 22 and is pressurized in the evaporative gas compressor 50 through the evaporation gas heat exchanger 60 and is supplied to the LNG heat exchanger 40 Exchanged by the LNG, can be decompressed in the evaporative gas decompressor 80, and then introduced into the pump 30. At this time, the pump 30 may mean the high-pressure pump 32.

As described above, the present embodiment can reduce the energy consumption by heating LNG through the boil-off gas, and can increase the liquefaction efficiency by pressurizing the boil-off gas to 48 bar or more to increase the liquefaction efficiency. The breakage of the high pressure pump 32 can be prevented. In addition, by discharging the flash gas separated from the boil off gas as a gas to reduce the generation rate of the boil off gas by reducing nitrogen (Nitrogen), one of the main components of the boil off gas, it is possible to improve the quality of the LNG.

3 is a conceptual diagram of an LNG processing system according to a second embodiment of the present invention.

3, the LNG processing system 3 according to the second embodiment of the present invention includes an LNG storage tank 10, a high-pressure LNG consumer 20a, a low-pressure LNG consumer 20b, a pump 30, The LNG heat exchanger 40, the evaporation gas compressor 50, the evaporation gas heat exchanger 60, the evaporation gas pressurization means 70, the evaporation gas decompressor 80, and the re-liquefier 100a, The rest of the configuration except for the liquefaction device 100a and the evaporation gas re-liquefaction line 110a is the same as that described in the first embodiment, so a detailed description of each configuration will be omitted.

The redistribution device 100a may be branched from the evaporation gas heat exchanger 60 to the LNG storage tank 10 on the evaporation gas supply line 22 and between the LNG heat exchanger 40, . The re-liquefier 100a can sufficiently cool the evaporated gas pressurized by the evaporative gas compressor 50 and change it into a liquid phase. The evaporated gas changed into the liquid phase is re-introduced into the LNG storage tank 10, Pressure LNG consumer 20a and can be used as a fuel for the high pressure LNG consumer 20a and may be supplied to the LNG storage tank 10 to control the pressure of the LNG storage tank 10 stably .

Here, the remelting device 100a may be provided on the evaporation gas remelting line 110a. The evaporation gas re-liquefaction line 110a may be connected to the LNG storage tank 10 in the evaporation gas supply line 22 and may be connected to the evaporation gas supply line 22 and evaporation gas supply line 22. [ A valve (not shown), for example, a three-way valve, may be provided on the connection point of the gas refill line 110a. Accordingly, the evaporated gas discharged from the evaporative gas heat exchanger (60) can be introduced into the refueling apparatus (100a) or the LNG heat exchanger (40).

At least a portion of the evaporated gas discharged from the refill liquor 100a may be in a liquid state and at least a portion of the evaporated gas discharged from the refill liquor 100a may be liquefied and introduced into the LNG storage tank 10, Pressure LNG consumer 20a from the tank 10 through the pump 30 and used.

As described above, in this embodiment, the evaporation gas generated in the LNG storage tank 10 is re-liquefied by external heat penetration and is recovered to the LNG storage tank 10, thereby preventing the evaporation gas from being discarded.

4 is a conceptual diagram of an LNG processing system according to a third embodiment of the present invention.

4, the LNG processing system 4 according to the third embodiment of the present invention includes an LNG storage tank 10, a high-pressure LNG consumer 20a, a low-pressure LNG consumer 20b, a pump 30, The LNG heat exchanger 40, the evaporation gas compressor 50, the evaporation gas heat exchanger 60, the evaporation gas pressurization means 70, the evaporation gas decompressor 80, and the re-liquefier 110b, Except for the liquefaction device 110b and the evaporation gas re-liquefaction line 110b, the remaining configuration is the same as that described in the first embodiment, so that a detailed description of each configuration will be omitted.

The redistribution device 110b of this embodiment is different from the redistribution device 100a of the second embodiment only in the position to be connected to the LNG heat exchanger 40 and can be provided on the evaporation gas re- And liquefies the evaporated gas.

The evaporation gas re-liquefaction line 110b of the present embodiment may be provided on the upstream side of the evaporation gas decompressor 80, branched on the evaporation gas supply line 22. [ A valve (not shown), for example, a three-way valve, may be provided on the connection point between the evaporation gas supply line 22 and the evaporation gas remelting line 110b. Accordingly, the evaporated gas discharged from the LNG heat exchanger 40 flows into the evaporative gas decompressor 80 by liquefying the evaporated gas through the re-liquefier 110b, or the evaporated gas is supplied to the liquefier 110b The refrigerant can be directly introduced into the evaporation gas decompressor 80 from the LNG heat exchanger 40 without being supplied.

Thus, in this embodiment, the evaporation gas through the LNG heat exchanger 40 can be easily liquefied through the redistribution device 110b and the evaporation gas can be prevented from being discarded, and the LNG heat exchanger 40, It is possible to directly discharge the evaporated gas to the evaporative gas decompressor 80, thereby increasing the power efficiency.

1, 2, 3, 4: LNG processing system 10: LNG storage tank
20: LNG demand 21: LNG supply line
22: boil-off gas supply line 23: low pressure boil-off gas supply line
24: LNG recovery line 30: pump
40: LNG heat exchanger 50: Evaporative gas compressor
60: Evaporative gas heat exchanger 70: Evaporative gas pressurizing means
80: Evaporative gas decompressor 81: Flash gas discharge line
90: Temporary storage tank 100a, 110b: Re-liquefying device
110a, 110b: evaporation gas re-liquefaction line

Claims (11)

An LNG supply line from the LNG storage tank to the LNG consumer site;
A pump provided on the LNG supply line for pressurizing the LNG discharged from the LNG storage tank;
An evaporative gas compressor for pressurizing the evaporative gas generated in the LNG storage tank;
An LNG heat exchanger provided on the LNG supply line between the LNG consumer and the pump for heat-exchanging the LNG supplied from the pump with the pressurized evaporated gas;
An evaporative gas heat exchanger installed upstream of the evaporative gas compressor for exchanging heat between the evaporated gas generated in the LNG storage tank and the evaporated gas pressurized in the evaporative gas compressor; And
It includes an evaporator gas decompressor for reducing the evaporation gas heat exchanged with the LNG in the LNG heat exchanger,
The pump includes a boosting pump provided on the LNG supply line and pressurizing the LNG, and a high pressure pump compressing the LNG discharged from the boosting pump to a high pressure.
The evaporated gas of the liquid state decompressed by the evaporating gas decompressor is introduced into the high pressure pump together with the LNG delivered through the boosting pump,
The evaporation gas decompressor, the LNG processing system, characterized in that to prevent the breakage of the high pressure pump by introducing the evaporated gas into the high pressure pump after decompression. The method of claim 1,
It is provided in the LNG supply line downstream of the boil-off gas reducer and between the LNG storage tank and the pump, LNG is introduced from the LNG storage tank, and boil-off gas is introduced from the boil-off gas reducer to convert LNG into the pump. LNG processing system further comprises a temporary storage tank for discharging. The method of claim 2, wherein the temporary storage tank,
LNG processing system, characterized in that the boil-off gas discharged from the boil-off gas decompressor mixed with liquefied LNG from the LNG storage tank and supplied to the pump. The method of claim 1,
The boil-off gas decompressor LNG processing system, characterized in that consisting of a multi-stage gas-liquid separator. The method of claim 4, wherein the boil-off gas decompressor,
LNG processing system, characterized in that to reduce the evaporated gas to 10bar to 20bar. The method of claim 1,
LNG processing system, characterized in that the flash gas discharge line is formed in the boil-off gas pressure reducer. delete The method of claim 1,
An evaporation gas reliquefaction line is connected between the evaporation gas heat exchanger and the LNG heat exchanger to the LNG storage tank,
LNG processing system further comprises a re-liquefaction apparatus provided on the boil-off gas reliquefaction line to liquefy the boil-off gas. The method of claim 1,
The boil-off gas reliquefaction line is provided upstream of the boil-off gas reducer,
LNG processing system further comprises a re-liquefaction apparatus provided on the boil-off gas reliquefaction line to liquefy the boil-off gas. The method of claim 1, wherein the LNG demanding entity, to which the LNG supply line is connected,
LNG processing system, characterized in that the high pressure LNG demand. The method of claim 10,
The boil-off gas compressor is provided with a plurality to pressurize the boil-off gas in multiple stages,
And a low pressure boil-off gas supply line, one end of which is connected between the plurality of boil-off gas compressors and supplies the pressurized boil-off gas to a low pressure LNG source.

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