KR101686513B1 - Device and method for BOG re-liquefaction - Google Patents

Abstract

An evaporation gas remelting device is disclosed. More specifically, an evaporative gas remelting device is disclosed that includes a nitrogen filter that separates nitrogen from the evaporative gas to reduce the energy required for the evaporative gas remelting device.
According to the present invention, it is possible to reduce the power consumption for re-liquefying the evaporation gas. In particular, when nitrogen is separated from the evaporation gas before the evaporation gas is supplied to the compressor, the power consumed in the compressor can be reduced.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a device and method for BOG re-

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to an apparatus and a method for liquefying a vaporized gas, and more particularly, to an apparatus and a method for liquefying a vaporized gas that can reduce power consumption required for liquefaction of a vaporized gas.

The storage tank for storing liquefied gas such as Natural Liquefied Gas (LNG) or Liquefied Petroleum Gas (LPG) and the like is provided around the inside of the storage tank and the outside of the storage tank Perfect insulation is impossible. Therefore, boil off gas (BOG) is continuously generated in the storage tank due to heat exchange inside and outside the storage tank.

When the evaporation gas is continuously accumulated in the storage tank, the pressure inside the storage tank increases and the safety becomes poor. Since the evaporation gas inside the storage tank accelerates the evaporation of the liquefied gas in the storage tank, It will accelerate.

Therefore, it is necessary to discharge or evaporate the evaporated gas to the outside. However, the process of re-liquefaction of such evaporated gas does not occur by itself. Especially, equipment for re-liquefaction of evaporation gas consumes power because it requires energy. Therefore, it is necessary to minimize the energy consumed in the equipment for compressing the evaporative gas in terms of power saving.

On the other hand, the evaporation gas discharged from the storage tank contains not only hydrocarbons but also nitrogen components. Taking liquefied natural gas as an example, the main component of liquefied natural gas is methane, but the evaporative gas discharged from the storage tank contains not only methane but also nitrogen.

Accordingly, an object of the present invention is to provide an apparatus for re-liquefying a vaporized gas discharged from a storage tank, the apparatus including: an evaporator for removing nitrogen contained in the evaporated gas to reduce the amount of evaporated gas to be cooled, There is a reduction.

According to an aspect of the present invention, there is provided an apparatus for re-liquefying an evaporated gas discharged from a storage tank for storing liquefied gas, the apparatus comprising: a compressor for compressing evaporative gas discharged from the storage tank; A heat exchanger provided downstream of the compressor for cooling the evaporated gas discharged from the compressor; And a nitrogen filter for separating nitrogen contained in the evaporated gas from the evaporated gas; An evaporation gas re-liquefying apparatus is provided.

A first expansion means provided downstream of the heat exchanger for decompressing the evaporated gas cooled by the heat exchanger; And a gas-liquid separator provided downstream of the first expansion means, for separating the gas-liquid mixture, which is decompressed through the first expansion means, into a gas and a liquid; As shown in FIG.

A cooler provided downstream of the compressor for cooling the evaporated gas discharged from the compressor; As shown in FIG.

The heat exchanger exchanges the evaporated gas discharged during the compression in the compressor with the mixed gas of the evaporated gas discharged from the storage tank and the mixed gas discharged from the gas-liquid separator to cool the evaporated gas discharged during the compression in the compressor 1 heat exchanger; And a second heat exchanger for heat-exchanging the evaporated gas cooled in the first heat exchanger with the evaporated gas discharged to the last in the compressor to cool the evaporated gas discharged after being compressed in the compressor to the last; . ≪ / RTI >

A second expansion means provided between the first heat exchanger and the second heat exchanger for further reducing the pressure of the evaporated gas cooled by the first heat exchanger to further cool the evaporated gas; As shown in FIG.

Four compressors are provided in series to compress the evaporation gas in four stages or a multi-stage compressor to compress the evaporation gases in four stages.

Said nitrogen filter comprising: a membrane for separating nitrogen from the evaporation gas according to the size of the molecule; . ≪ / RTI >

According to another aspect of the present invention, there is provided an apparatus for re-liquefying an evaporated gas discharged from a storage tank for storing liquefied gas, the apparatus comprising: A nitrogen filter for separating the nitrogen gas from the nitrogen gas; Wherein the nitrogen filter is provided downstream of the compressor for compressing the evaporated gas.

According to another aspect of the present invention, there is provided a method for re-liquefying an evaporated gas discharged from a storage tank storing a liquefied gas, the method comprising: compressing an evaporated gas discharged from the storage tank; Separating nitrogen from the compressed evaporated gas; And an evaporation gas re-liquefaction method.

According to the present invention, it is possible to reduce the power consumption for re-liquefying the evaporation gas. In particular, it is possible to reduce the power consumed in the compressor by reducing the amount of evaporative gas to cool by separating nitrogen from the evaporated gas before the evaporated gas is supplied to the compressor.

1 is a view showing an evaporative gas remelting apparatus according to a first embodiment of the present invention.
2 is a view showing an evaporative gas remelting apparatus according to a second embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention will be described with reference to the embodiments shown in the drawings, but it is to be understood that various modifications and equivalent embodiments may be made by those skilled in the art without departing from the scope of the present invention. Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

FIG. 1 is a view showing an evaporative gas remelting apparatus according to a first embodiment of the present invention, and FIG. 2 is a view showing an evaporating gas remelting apparatus according to a second embodiment of the present invention. As will be described later, the evaporation gas remelting apparatus shown in FIG. 1 uses a separate refrigerant to re-liquefy the evaporation gas, whereas the evaporation gas re-liquefying apparatus shown in FIG. 2 uses the evaporation gas discharged from the storage tank Partial Re-liquefaction device that re-liquefies evaporated gas using cold heat of gas. First, a first embodiment of the present invention will be described with reference to FIG. The liquefied gas stored in the storage tank is not limited to liquefied natural gas but may be a liquefied natural gas such as liquefied petroleum gas (hereinafter, referred to as " liquefied natural gas " It contains all kinds of liquefied gas.

1, the apparatus for liquefying vaporized gas according to the first embodiment of the present invention includes a storage tank 1 for storing LNG and discharging vapor generated from LNG, A cooler 30 for supplying a coolant for re-liquefying the evaporated gas by heat exchange with the evaporated gas, a heat exchanger 30 for exchanging heat between the evaporated gas discharged from the storage tank 1 and the refrigerant discharged from the cooler 30, A compressor 10 provided between the storage tank 1 and the heat exchanger 20 for compressing the evaporated gas discharged from the storage tank 1 and a refrigerant discharged from the storage tank 1 And a nitrogen filter 40 for separating the nitrogen. At this time, the nitrogen filter 40 may be provided between the compressor 10 and the heat exchanger 20. The nitrogen filter 40 may include a membrane (not shown) capable of separating nitrogen separately depending on the size of the molecules. Also, although not shown in FIG. 1, the nitrogen collected in the nitrogen filter 40 may be discharged to the outside or stored in a separate nitrogen storage device (not shown), and then used for other purposes. Hereinafter, the operation of the evaporation gas remelting apparatus according to the first embodiment of the present invention will be described with reference to FIG.

The evaporated gas discharged from the storage tank (1) is pressurized while passing through the compressor (10). The pressurized evaporation gas is supplied to the nitrogen filter (40). As described above, nitrogen can be more efficiently separated from the pressurized evaporated gas in the compressor 10 when the nitrogen filter 40 is capable of separating the nitrogen separately according to the size of the molecules. That is, the evaporation gas is separated into nitrogen and methane as it passes through the membrane separating the molecules according to the size of the molecules. The higher the pressure of the evaporation gas, the more efficient this separation takes place.

The nitrogen separated from the nitrogen filter 40 is discharged to the outside as described above or stored in a separate nitrogen storage device (not shown), and the nitrogen-separated evaporated gas is supplied to the heat exchanger 20. In the heat exchanger (20), the refrigerant supplied from the cooling device (30) and the evaporated gas from which nitrogen is separated heat-exchange and the evaporated gas is liquefied.

According to the first embodiment of the present invention, the liquefaction performance is improved as compared with the case where the evaporation gas is supplied to the heat exchanger 20 without separating nitrogen. That is, in the heat exchanger 20, not only the methane as the main component of the evaporative gas but also the nitrogen is cooled, whereas when the nitrogen is removed from the evaporative gas, only the evaporative gas excluding nitrogen is cooled in the heat exchanger 20 The cold heat of the refrigerant can be used more efficiently. Therefore, ultimately, the power required for evaporating the gas re-liquefaction can be saved. Thereafter, the refrigerant discharged from the heat exchanger 20 is supplied again to the cooling device 30, cooled, and then supplied to the heat exchanger 20 again. Further, the liquefied evaporated gas is supplied again to the storage tank 1.

1 shows a case where the nitrogen filter 40 is provided between the compressor 10 and the heat exchanger 20 but the nitrogen filter 40 may be provided between the storage tank 1 and the compressor 10 have. In this case, the power consumed by the compressor 10 is also reduced. That is, when the nitrogen filter 40 is provided between the storage tank 1 and the compressor 10, only the evaporated gas in which nitrogen is separated is supplied to the compressor 10, and in the compressor 10, Lt; RTI ID = 0.0 > compress < / RTI > of nitrogen. Therefore, power consumed in the evaporative gas remelting apparatus is reduced.

2 is a view showing an evaporative gas remelting apparatus according to a second embodiment of the present invention. As described above, FIG. 2 shows a partial re-liquefaction apparatus for re-liquefying evaporated gas using the cold heat of the evaporated gas discharged from the storage tank without a separate refrigerant, unlike FIG.

As shown in FIG. 2, the evaporative gas remelting apparatus according to the second embodiment of the present invention includes a storage tank 1 for storing LNG and discharging vapor generated from LNG, A second compressor 102, a third compressor 104 and a fourth compressor 106 for sequentially compressing the evaporated gas discharged from the storage tank 1. The first compressor 100, the second compressor 102, the third compressor 104,

Downstream of the first to fourth compressors 100, 102, 104, and 106, a first cooler for cooling the evaporated gas discharged from the first to fourth compressors 100, 102, 104, A first cooler 110, a second cooler 112, a third cooler 114, and a fourth cooler 116. However, the quantity of such compressors 100, 102, 104, and 106 and the coolers 110, 112, 114, 116 is exemplary only and may include more than four compressors or coolers. Alternatively, instead of a plurality of compressors, one multi-stage compressor may be used. For example, the multi-stage compressor may be a multi-stage compressor that compresses the evaporation gas into four stages.

Further, downstream of the fourth compressor 106, as shown in FIG. 2, may include a nitrogen filter 150 for separating nitrogen from the evaporated gas discharged from the fourth compressor 106. However, the position of the nitrogen filter 150 is not limited to Fig. For example, the nitrogen filter 150 may be provided downstream of the first to third compressors 100, 102, 104, or upstream of the first compressor 100. Also, although not shown in FIG. 2, the nitrogen collected in the nitrogen filter 150 may be discharged to the outside or stored in a separate nitrogen storage device (not shown) and then used for other purposes. An example of the principle in which nitrogen is separated in the nitrogen filter 150 is omitted from FIG.

As shown in FIG. 2, the evaporative gas remelting apparatus according to the second embodiment of the present invention diffuses the evaporated gas discharged from the third compressor 104 into evaporation gas discharged from the storage tank 1, A first heat exchanger 120 for cooling the evaporated gas discharged from the third compressor 104 by heat exchange with the gas mixture discharged from the separator 130 and a second heat exchanger 120 for cooling the evaporated gas cooled in the first heat exchanger 120 And a second heat exchanger (122) for cooling the evaporated gas discharged from the fourth compressor (106) by heat exchange with the evaporated gas discharged from the fourth compressor (106). However, the evaporated gas cooled in the first heat exchanger (120) is not limited to the evaporated gas discharged from the third compressor (104). For example, the evaporated gas cooled in the first heat exchanger 120 may be an evaporative gas discharged from the first compressor 100 or the second compressor 102, and the quantity of the compressor may be larger than that shown in FIG. 2 It may be a vaporized gas discharged from another compressor.

Downstream of the second heat exchanger (122) is provided a first expansion means (140) for decompressing and cooling the evaporated gas cooled in the second heat exchanger (122) to produce a vapor-liquid mixture from the evaporated gas, wherein the first expansion means 140), a gas-liquid separator (130) for passing the gas-liquid mixture through the first expansion means (140) and separating the gas-liquid mixture into gas and liquid may be provided.

A second expansion means 142 provided between the first heat exchanger 120 and the second heat exchanger 122 for further reducing the pressure of the evaporated gas cooled in the first heat exchanger 120 may be provided . The second expansion means 142 may be an expander and when the second expansion means 142 is an inflator, the kinetic energy generated by expanding the evaporation gas in the second expansion means 142 may be transmitted to a power transmission means For example, the first compressor 100, and can be used as a power source.

Hereinafter, the operation of the evaporation gas remelting apparatus according to the second embodiment of the present invention will be described with reference to FIG.

The evaporated gas discharged from the storage tank 1 and the gaseous evaporated gas discharged from the gas-liquid separator 130 are supplied to the first heat exchanger 120. The evaporated gas discharged from the storage tank 1 and the gaseous state discharged from the gas-liquid separator 130 are separated from the evaporated gas discharged from the compressor, referring to FIG. 2, compared with the evaporated gas discharged from the third compressor 104 It is possible to transmit cold heat to the evaporated gas discharged from the third compressor (104). Accordingly, the evaporated gas discharged from the third compressor (104) in the first heat exchanger (120) is cooled.

The evaporated gas discharged from the storage tank 1 and the gaseous evaporated gas discharged from the gas-liquid separator 130, which have been deprived of the cold heat in the first heat exchanger 120, are supplied to the first to third compressors 100, ). Some of the evaporated gas discharged from the third compressor 104 is supplied to the first heat exchanger 120 and cooled as described above and another portion of the evaporated gas discharged from the third compressor 104 is discharged to the fourth compressor 106 and is further compressed. Nitrogen is removed from the evaporated gas discharged from the fourth compressor 106 through the nitrogen filter 150. The nitrogen-free evaporated gas passes through the second heat exchanger 122 and is further reduced in pressure and cooled through the second expansion means 142 after being cooled in the first heat exchanger 120, Exchanges heat with the evaporation gas supplied to the evaporator 122 and is further cooled. The evaporated gas cooled in the second heat exchanger 122 is further decompressed and cooled while passing through the first expansion means 140, and the gas-liquid mixture is separated into gas and liquid in the gas-liquid separator 130. The liquid is supplied to the tank including the storage tank 1 and the gas is supplied to the first heat exchanger 120 to repeat the above-described process.

Meanwhile, the evaporated gas heated in the second heat exchanger 122 is supplied to the first compressor 100 together with the 'evaporated gas heated in the first heat exchanger 120' to repeat the above-described process.

2 shows a case where the nitrogen filter 150 is provided downstream of the fourth compressor 106. The nitrogen filter 150 is disposed downstream of the first to third compressors 100, 1 compressor 100. In this case, As the nitrogen filter 150 is disposed upstream of the line provided with the compressors 100, 102, 104, and 106, the power consumption for compressing nitrogen is reduced. On the other hand, as the nitrogen filter 150 is disposed downstream of the line provided with the compressors 100, 102, 104, and 106, it is possible to efficiently separate nitrogen from the operation principle of the nitrogen filter 150 described above.

1 - Storage tank
10 - Compressor
20 - Heat exchanger
30 - Cooling system
40 - Nitrogen filter
100 - first compressor
102 - Second compressor
104 - third compressor
106 - Fourth compressor
110 - first cooler
112 - second cooler
114 - Third Cooler
116 - Fourth cooler
120 - first heat exchanger
122 - a second heat exchanger
130 - gas-liquid separator
140 - a first expansion means
142 - a second expansion means
150 - Nitrogen filter

Claims (9)

An apparatus for re-liquefying a vaporized gas discharged from a storage tank for storing a liquefied gas,
A compressor for compressing the evaporated gas discharged from the storage tank;
A heat exchanger provided downstream of the compressor for cooling the evaporated gas discharged from the compressor; And
A nitrogen filter for separating nitrogen contained in the evaporated gas from the evaporated gas; Lt; / RTI >
A first expansion means provided downstream of the heat exchanger for decompressing the evaporated gas cooled by the heat exchanger; And
A gas-liquid separator provided downstream of the first expansion means, for separating the gas-liquid mixture, which is decompressed through the first expansion means, into a gas and a liquid; Further comprising:
The heat exchanger
A first heat exchanger which cools the evaporated gas discharged during the compression in the compressor by exchanging heat with the mixed gas of the evaporated gas discharged from the storage tank and the gas discharged from the gas-liquid separator, ; And
A second heat exchanger for heat-exchanging the evaporated gas cooled in the first heat exchanger with the evaporated gas discharged after being compressed in the compressor to cool the evaporated gas discharged after being compressed in the compressor to the last; And the evaporation gas remelting device. delete The method according to claim 1,
A cooler provided downstream of the compressor for cooling the evaporated gas discharged from the compressor; ≪ / RTI >
Evaporating gas remelting device. delete The method according to claim 1,
A second expansion means provided between the first heat exchanger and the second heat exchanger for further reducing the pressure of the evaporated gas cooled by the first heat exchanger to further cool the evaporated gas; Further comprising: an evaporation gas re-liquefying device for heating the evaporation gas. The method according to claim 1,
The compressor includes:
Four in series, compressing the evaporation gas in four stages,
A multi-stage compressor, comprising:
Evaporating gas remelting device. The method according to claim 1,
Said nitrogen filter comprising: a membrane for separating nitrogen from the evaporation gas according to the size of the molecule; / RTI >
Evaporating gas remelting device. delete A method for re-liquefying an evaporated gas discharged from a storage tank for storing a liquefied gas,
Supplying the evaporated gas discharged from the storage tank to the multi-stage compressor;
A step of discharging evaporation gas during compression by the multi-stage compressor, and cooling the evaporation gas discharged from the storage tank and supplied to the multi-stage compressor; And
And a step of discharging the evaporated gas compressed to the last in the multi-stage compressor and cooling the evaporated gas with the cooled evaporated gas,
Separating the nitrogen from the compressed evaporated gas to the last in the multi-stage compressor before cooling the evaporated gas compressed to the last in the multi-stage compressor.

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