KR20170135147A - liquefaction system of boil-off gas and ship having the same - Google Patents

Abstract

The present invention relates to a re-liquefaction system of boil-off gas and a ship which can maximize re-liquefaction efficiency. The re-liquefaction system of boil-off gas comprises: a liquefied gas storage tank; a compressor to compress boil-off gas produced in the liquefied gas storage tank; a boil-off gas heat exchanger to cool the boil-off gas compressed by the compressor with the boil-off gas produced in the liquefied gas storage tank; a decompression valve to decompress the boil-off gas cooled by the boil-off gas heat exchanger; a gas-liquid separator to separate gaseous flash gas from the boil-off gas decompressed by the decompression valve; and a cooler which is arranged between the compressor and the boil-off gas heat exchanger, and uses a heating fluid for heating a cofferdam to cool the boil-off gas compressed by the compressor.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an evaporation gas re-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporation gas remelting system and a ship.

Liquefied natural gas (Liquefied natural gas), Liquefied petroleum gas (Liquefied petroleum gas) and other liquefied gas are widely used in place of gasoline or diesel in recent technology development.

Liquefied natural gas is a liquefied natural gas that is obtained by refining natural gas collected from a gas field. It is a colorless and transparent liquid with almost no pollutants and high calorific value. On the other hand, liquefied petroleum gas is a liquid fuel made by compressing gas containing propane (C3H8) and butane (C4H10), which come from oil in oil field, at room temperature. Liquefied petroleum gas, like liquefied natural gas, is colorless and odorless and is widely used as fuel for household, business, industrial, and automotive use.

Such liquefied gas is stored in a liquefied gas storage tank installed on the ground or stored in a liquefied gas storage tank provided in a ship which is a means of transporting the ocean. The liquefied natural gas is liquefied to a volume of 1/600 The liquefaction of liquefied petroleum gas has the advantage of reducing the volume of propane to 1/260 and the content of butane to 1/230, resulting in high storage efficiency. The temperature and pressure necessary for driving the engine using such liquefied gas as fuel may be different from the state of the liquefied gas stored in the tank.

In addition, when LNG is stored in the liquid phase, some LNG is vaporized and boil off gas (BOG) is generated as heat penetration occurs in the tank. Such evaporation gas may cause problems in the evaporation gas re-liquefaction system, (To discharge the evaporation gas to the outside in order to eliminate the risk of damage of the tank by lowering the tank pressure in the past) by consuming the evaporation gas to the outside, Causing a problem of waste.

Therefore, recently, as a technique for efficiently processing evaporative gas, there has been utilized a method of re-liquefying the generated evaporative gas and supplying it to the engine. However, since sufficient evaporative gas is not consumed even in such a utilization, efficient utilization And the ongoing research and development is being carried out.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for heating a cofferdam of an automobile so that a heating fluid used for heating a coffer dam is supplied with heat from a compressed evaporated gas, And to provide a vaporization gas remelting system and a ship capable of maximizing re-liquefaction efficiency by lowering the temperature of the compressed gas used for re-liquefaction.

According to an embodiment of the present invention, an evaporation gas remelting system includes a liquefied gas storage tank; A compressor for compressing the evaporated gas generated in the liquefied gas storage tank; An evaporating gas heat exchanger for cooling the evaporated gas compressed in the compressor to evaporated gas generated in the liquefied gas storage tank; A pressure reducing valve for reducing the pressure of the evaporated gas cooled through the evaporating gas heat exchanger; A gas-liquid separator for separating gaseous flash gas from the evaporated gas depressurized through the pressure reducing valve; And a cooler provided between the compressor and the evaporative gas heat exchanger to cool the evaporated gas compressed in the compressor by utilizing a heating fluid for heating the cofferd dam.

Specifically, the apparatus includes a coffer dam heating unit that uses the heating fluid to implement heating of the coffer dam, and the cooler is capable of heat-exchanging the cooling fluid with the evaporating gas while heating the coffer dam.

Specifically, the coffer dam may be provided on a side surface of the liquefied gas storage tank.

Specifically, the heater may further include a heater for heating the heating fluid.

Specifically, the heater can heat the heating fluid heated by the evaporation gas.

Specifically, the heater can heat the heating fluid using heat generated in a motor room.

Specifically, the apparatus may further include a flash gas heat exchanger for exchanging heat between the evaporation gas heat exchanger and the gas-liquid separator.

Specifically, the air conditioner may further include a mixer provided between the liquefied gas storage tank and the evaporative gas heat exchanger and mixing the flash gas into the evaporative gas.

Specifically, the evaporation gas supply line is connected to the consumer through the evaporation gas heat exchanger in the liquefied gas storage tank, and the compressor is installed. An evaporation gas liquefaction line branched from the evaporation gas supply line downstream of the compressor and connected to the gas-liquid separator via the evaporation gas heat exchanger and provided with the pressure reducing valve; And a flash gas return line connected from the gas-liquid separator to the mixer.

Specifically, the flash gas return line may be connected from the gas-liquid separator to the mixer via the flash gas heat exchanger.

A ship according to an embodiment of the present invention is characterized by having the evaporation gas re-liquefaction system.

The evaporation gas re-liquefaction system and the ship according to the present invention can greatly improve the energy use efficiency by heating the heating fluid for cofferdam heating by using the compressed evaporation gas.

FIG. 1 is a conceptual diagram of a vaporization gas remelting system according to an embodiment of the present invention.
2 is a conceptual diagram of a vaporization gas remelting system according to another embodiment of the present invention.
3 is a conceptual diagram of a vaporization gas remelting system according to another embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The objects, particular advantages and novel features of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. It should be noted that, in the present specification, the reference numerals are added to the constituent elements of the drawings, and the same constituent elements are assigned the same number as much as possible even if they are displayed on different drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, an evaporation gas re-liquefaction system 1 according to the present invention will be described. The present invention includes a vapor re-liquefaction system 1 and a vessel having the same.

Hereinafter, the liquefied gas may be used to encompass all gaseous fuels generally stored in a liquid state, such as LNG or LPG, ethylene, ammonia, etc. In the case where the gas is not in a liquid state by heating or pressurization, . This also applies to the evaporative gas. In addition, LNG can be used to mean not only NG (Natural Gas) in liquid state but also NG in supercritical state for convenience, and evaporation gas can be used to include not only gaseous evaporation gas but also liquefied evaporation gas have.

Also in the following, the reduced pressure may be a state generated through expansion, and conversely, the reduced pressure may be a state generated by expansion, so that the reduced pressure and the expansion can be used in combination with each other.

FIG. 1 is a conceptual diagram of a vaporization gas remelting system according to an embodiment of the present invention.

1, an evaporation gas remelting system 1 according to an embodiment of the present invention includes a liquefied gas storage tank 10, a compressor 20, a cooler 23, an evaporation gas heat exchanger 30, A pressure reducing valve 40, a gas-liquid separator 50, and a mixer 70.

The liquefied gas storage tank 10 stores liquefied gas to be supplied to the customer 100. The liquefied gas storage tank 10 must store the liquefied gas in a liquid state, wherein the liquefied gas storage tank 10 can store the liquefied gas at a pressure of 1 bar to 10 bar (1.03 bar, for example).

The liquefied gas storage tank 10 may be a stand-alone type, a membrane type, or the like, and various liquefied structures may be used to store the liquefied gas in a liquid state. The evaporated gas generated in the liquefied gas storage tank 10 may be, The compressor 20 or the like.

The compressor (20) compresses the evaporated gas generated in the liquefied gas storage tank (10) and supplies it to the customer (100). Here, the customer 100 is a high-pressure consumer (100a (70) MEGI engine or the like) using a high-pressure gas such as 200 bar to 400 bar (for example, 300 bar), a low-pressure consumer 100b 70) DFDE, DFDG, boiler, GCU, turbine, etc.).

The compressor 20 may be provided in a plurality of units and may be connected to the downstream side of the five-stage compressor 20 or downstream of the two-stage compressor 20 according to a required pressure. An intermediate cooler 21 is provided downstream of each compressor 20 to cool the evaporated gas heated by the compressed heat.

The evaporation gas supply line 11 may be provided from the liquefied gas storage tank 10 to the customer 100 and the evaporation gas supply line 11 may be provided with a valve (not shown) for controlling the supply amount of the evaporation gas, May be provided. The evaporation gas supply line 11 may be connected to the customer 100 via a vapor gas heat exchanger 30 to be described later.

The evaporation gas supply line 11 is provided with a mixer (not shown), and the liquefied gas supply line 12 can be connected from a liquefied gas pump (not shown) installed in the liquefied gas storage tank 10 to the mixer, A forced vaporizer (13) may be provided on the liquefied gas supply line (12). Further, a valve (not shown) may be provided upstream or downstream of the mixer to adjust the flow rate of the evaporation gas.

That is, the liquefied gas may be mixed in the flow of the evaporative gas from the liquefied gas storage tank 10 to the compressor 20. The evaporation gas is supplied to the customer 100 to operate the customer 100. When the flow rate of the evaporation gas is insufficient, the liquefied gas can be forcibly vaporized and replenished. For this, a liquefied gas pump is provided in the liquefied gas storage tank 10, and the liquefied gas can be forcedly vaporized by the forced vaporizer 13 and then joined to the vaporized gas through the mixer.

When the liquefied gas is mixed with the evaporated gas, the compressor 20 can compress the evaporated gas mixed with the liquefied gas, and the evaporated gas heat exchanger 30, which will be described later, converts the compressed evaporated gas into the evaporated gas mixed with the liquefied gas Of course.

The cooler 23 is provided between the compressor 20 and the evaporation gas heat exchanger 30 and utilizes a heating fluid for heating the coffer dam to cool the evaporation gas. The heating of the copper dam can be performed by heating the inside of the copper dam to about 5 degrees instead of the cryogenic temperature, so that a general structure other than the cryogenic structure can be disposed inside the copper dam. The cooler 23 can be provided upstream of the evaporative gas heat exchanger 30 in the evaporative gas liquefaction line 22 and can heat-exchange the evaporated gas compressed in the compressor 20 with the heating fluid.

For this, a heating fluid circulation line 27 may be provided between the cofferdam heating unit 25 and the cooler 23, and the heating fluid circulation line 27 may be provided in the form of a closed loop, Can be achieved.

At this time, the heating fluid may be a fluid used for implementing the heating of the copper dam in the copper dam heating section 25, and the copper dam may be a structure provided on the side (front and rear) of the liquefied gas storage tank 10.

The heating fluid is cooled while heating the cofferdams, and the cooled heating fluid can be heated while exchanging heat with the evaporated gas in the cooler 23. In this case, the evaporated gas is cooled and transferred to the evaporative gas heat exchanger (30), and the heating fluid is heated and utilized for heating the copper dam.

That is, in this embodiment, the heating fluid used for heating the coffer dam is supplied with the heat contained in the compressed evaporated gas, so that the energy required for heating the coffer dam can be reduced. Also, since the compressed evaporated gas is cooled by the heating fluid and then flows into the evaporated gas heat exchanger 30, the efficiency of re-liquefaction of the evaporated gas can be increased.

The evaporated gas can be introduced into the evaporative gas heat exchanger 30 bypassing the cooler 23 in accordance with conditions such as whether or not the copper dam is heated or the like and in this case the evaporative gas liquefaction line 22 is provided with a cooler bypass line 24 ) May be provided.

The evaporation gas heat exchanger 30 is provided upstream of the compressor 20 on the evaporation gas supply line 11 and is provided downstream of the cooler 23 on the evaporation gas liquefaction line 22 at the same time. The evaporation gas heat exchanger 30 is connected to the evaporator 22 through the evaporator 22 so that the evaporation gas cooled by the heating fluid in the cooler 23 after being compressed to a high pressure by the compressor 20 is supplied to a relatively low- (The evaporation gas to be introduced into the evaporator 20).

The evaporation gas heat exchanger 30 may be provided in a three stream structure having two flow paths or three flow paths having two flow paths and the evaporation gas supply line 11 and the evaporation gas liquefaction line 22 may be connected. The evaporation gas liquefaction line 22 is branched downstream of the compressor 20 of the evaporation gas supply line 11 and connected to the gas-liquid separator 50 via the evaporation gas heat exchanger 30, Etc. may be provided. That is, the evaporation gas heat exchanger 30 can cool the evaporation gas of the evaporation gas liquefaction line 22 to the evaporation gas of the evaporation gas supply line 11.

At this time, the evaporation gas liquefaction line 22 can be branched from the evaporation gas supply line 11 at least one of the downstream and upstream of the most downstream intermediate cooler 21, and the evaporation gas liquefaction line 22 can be branched In the case of a structure that branches and then merges downstream and upstream of the cooler 21, the flow of the evaporative gas can be controlled by a valve (not shown).

The flash gas can be joined to the evaporative gas flowing from the liquefied gas storage tank 10 to the evaporative gas heat exchanger 30. [ The flash gas may be mixed with the evaporation gas of -80 to -130 deg., 1.03 bar discharged from the liquefied gas storage tank 10 as a low-temperature gas of -80 to -150 degrees, which will be described later.

The evaporated gas discharged from the liquefied gas storage tank 10 may be cooled by the mixing of the flash gas and then introduced into the evaporative gas heat exchanger 30. However, depending on the situation, the temperature of the flash gas varies, and the evaporation gas may be slightly heated by the mixing of the flash gas. Cooling or heating of the evaporation gas by the flash gas mixing may also vary depending on conditions such as the flow rate of the evaporation gas.

The pressure reducing valve 40 at least partially liquefies the high pressure evaporating gas cooled in the evaporating gas heat exchanger 30 by reducing the pressure to 1 to 10 bar. When the pressure is reduced rapidly, the temperature is simultaneously lowered, so that the evaporation gas in which the pressure drops sharply by the pressure reducing valve 40 can be liquefied.

The pressure reducing valve 40 may be a J-T valve utilizing the line-Thomson effect, and an inflator (not shown) may be provided instead of the pressure reducing valve 40, unlike the drawing.

Since the evaporation gas is already cooled in the evaporation gas heat exchanger 30 before the decompression valve 40 decompresses the high-pressure evaporation gas of 300 bar or more to within 10 bar, for example, at least a part of the evaporation gas is decompressed by the decompression valve 40 Can be liquefied.

The depressurization valve 40 can be controlled to be depressurized in accordance with the internal pressure of the liquefied gas storage tank 10 and the depressurized pressure by the depressurization valve 40 can be maintained higher than the internal pressure of the liquefied gas storage tank 10.

The gas-liquid separator (50) separates the vaporized gas, which is at least partially liquefied by the decompression, into gas and liquid. The evaporation gas liquefaction line 22 is branched from the evaporation gas supply line 11 downstream of the compressor 20 and connected to the gas-liquid separator 50. A liquid component is supplied to the liquefied gas storage tank 10 The liquid return line 53 can be connected.

The gas-liquid separator 50 can separate the gaseous flash gas from the decompressed gas through the pressure reducing valve 40. A flash gas return line 61 (gas return line) .

The flash gas return line 61 is connected from the gas-liquid separator 50 to the mixer 70. At this time, the mixer 70 may be positioned between the liquefied gas storage tank 10 and the evaporative gas heat exchanger 30.

Therefore, the evaporation gas flowing toward the compressor 20 along the evaporation gas supply line 11 can be mixed with the flash gas by the mixer 70, and the mixing of the liquefied gas with the mixer can be performed before or after that have.

However, in the case where the liquefied gas is mixed, the flow rate of the evaporation gas is less than the required flow rate of the demander 100. Therefore, when mixing is performed in the mixer, liquefaction of the evaporation gas is not necessary and mixing in the mixer 70 is omitted .

This is the same in the opposite case. That is, in the case where flash gas mixing is performed in the mixer 70, the flow rate of the evaporation gas is sufficient, so that the liquefied gas in the mixer may not be mixed into the evaporation gas. That is, flash gas mixing and liquefied gas mixing can be performed at this time.

The mixer 70 mixes the flash gas into the evaporation gas. The mixer 70 can mix the flash gas with the evaporative gas upstream of the evaporative gas heat exchanger 30 and specifically the mixer 70 can mix the flash gas between the liquefied gas storage tank 10 and the evaporative gas heat exchanger 30 Flash gas can be mixed into the evaporative gas.

Since the flash gas that joins the evaporation gas through the mixer 70 is cooler than the evaporation gas that is compressed at the high pressure in the compressor 20, the flash gas merged through the mixer 70 is supplied to the evaporation gas heat exchanger 30, . ≪ / RTI >

In this case, the evaporation gas heat exchanger (30) can cool the evaporated gas compressed using the evaporated gas in which the flash gas is mixed. Further, as the flash gas is mixed, the minimum load of the compressor 20 can be assured, and the driving stability of the compressor 20 can be ensured.

When the compressor 20 is operated with a too low load (a load of about 10 to 30% or less), the driving stability is deteriorated, the compression efficiency is lowered, and the power consumption is excessively compared with the evaporation gas flow rate. The compressor 20 can be stably and efficiently operated by maintaining the load of the compressor 20 at a predetermined level or more by mixing the gas.

As described above, in this embodiment, the heat of the surplus evaporation gas that has not been consumed in the customer after being compressed at the high pressure can be utilized for heating the heating fluid for the cofferdam heating, thereby significantly improving the energy efficiency and improving the evaporation gas re- .

2 is a conceptual diagram of a vaporization gas remelting system according to another embodiment of the present invention.

Referring to Fig. 2, the present embodiment further includes a heater 26. Fig. The description omitted here is replaced with a description of another embodiment.

The heater 26 heats the heating fluid. The heating fluid is used for heating the cofferdams. The heating fluid is heated while exchanging heat with the compressed evaporated gas in the cooler 23, but the heat may not be sufficient for heating the cofferdams.

Accordingly, the heater 26 can further heat the heating fluid heated in the cooler 23 and deliver it to the cofferdam heating unit 25. [ At this time, the heater 26 may utilize various waste heat or heat generating space generated in the ship. For example, the heater 26 may heat the heating fluid by using the heat generated in the motor room. That is, the heater 26 may be a motor room ventilation system or a motor cooling system.

However, even if the present embodiment includes the heater 26, since the heating fluid is heated by the evaporator gas in the cooler 23, the present embodiment has an effect that the load of the heater 26 can be greatly reduced.

3 is a conceptual diagram of a vaporization gas remelting system according to another embodiment of the present invention.

Referring to FIG. 3, the evaporative gas re-liquefaction system according to another embodiment of the present invention may further include a flash gas heat exchanger 60 according to the embodiment of the present invention illustrated in FIG. The description omitted in the description of the other embodiments.

The flash gas heat exchanger 60 can further cool the flash gas to a high pressure through the compressor 20 and then evaporate gas (which may include flash gas) cooled in the evaporation gas heat exchanger 30.

For this, the flash gas return line 61 is connected from the gas-liquid separator 50 to the mixer 70 via the flash gas heat exchanger 60. That is, the flash gas heat exchanger 60 is connected to the flash gas return line 61, so that the flash gas heat exchanger 60 supplies the evaporated gas of the evaporated gas liquefaction line 22 to the flash gas of the flash gas return line 61 Can be cooled.

For example, the flash gas is a low-pressure gas in a gas-liquid low-temperature state generated by decompressing the high-pressure evaporation gas of about 300 bar, and the high-pressure evaporation gas cooled in the evaporation gas heat exchanger 30 is compressed Liquid separator 50 because it is heated and then cooled by heat.

Therefore, the evaporated gas, which has been cooled in the evaporation gas heat exchanger 30 after compression, can be secondarily cooled by the flash gas. On the contrary, the flash gas is heated and then supplied to the evaporation gas heat exchanger 30). ≪ / RTI >

Thereafter, the pressure reducing valve 40 can at least partially liquefy the high-pressure evaporating gas through the flash gas heat exchanger 60 by reducing the pressure to 1 to 10 bar. The flash gas heat exchanger 60 can cool the evaporation gas to the flash gas between the compressor 20 and the decompression valve 40 so that the decompression valve 40 is first cooled through the evaporation gas heat exchanger 30 It is possible to depressurize the secondarily cooled evaporated gas through the flash gas heat exchanger (60).

Although the flash gas heat exchanger 60 and the evaporation gas heat exchanger 30 are shown as separate structures in the figure, they may be integrally provided. When the flash gas heat exchanger 60 and the evaporation gas heat exchanger 30 are integrally provided, An evaporating gas to be discharged, and a heat exchanger having three streams such as a flash gas.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the same is by way of illustration and example only and is not to be construed as limiting the present invention. It is obvious that the modification and the modification are possible.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

1: evaporation gas re-liquefaction system 10: liquefied gas storage tank
20: compressor 23: cooler
25: cofferdam heating portion 26: heater
30: evaporation gas heat exchanger 40: reducing valve
50: gas-liquid separator 70: mixer
100: Consumer

Claims (11)

Liquefied gas storage tanks;
A compressor for compressing the evaporated gas generated in the liquefied gas storage tank;
An evaporating gas heat exchanger for cooling the evaporated gas compressed in the compressor to evaporated gas generated in the liquefied gas storage tank;
A pressure reducing valve for reducing the pressure of the evaporated gas cooled through the evaporating gas heat exchanger;
A gas-liquid separator for separating gaseous flash gas from the evaporated gas depressurized through the pressure reducing valve; And
And a cooler provided between the compressor and the evaporative gas heat exchanger for cooling the evaporated gas compressed in the compressor by utilizing a heating fluid for heating the cofferd dam. The method according to claim 1,
And a coffer dam heating unit for heating the coffer dam by using the heating fluid,
Wherein the cooler heat-exchanges the cooled heating fluid with the evaporative gas while heating the cofferd dam. The apparatus according to claim 1,
Wherein the liquid storage tank is provided on a side surface of the liquefied gas storage tank. The method according to claim 1,
Further comprising a heater for heating the heating fluid. The apparatus as claimed in claim 4,
And the heating fluid heated by the evaporation gas is heated. The apparatus as claimed in claim 4,
Wherein the heating fluid is heated using heat generated in a motor room. The method according to claim 1,
Further comprising a flash gas heat exchanger for exchanging heat between said evaporation gas heat exchanger and said gas-liquid separator with said flash gas. The method according to claim 1,
Further comprising a mixer disposed between the liquefied gas storage tank and the evaporative gas heat exchanger and mixing the flash gas into the evaporative gas. 9. The method of claim 8,
An evaporation gas supply line connected to the consumer through the evaporation gas heat exchanger in the liquefied gas storage tank and provided with the compressor;
An evaporation gas liquefaction line branched from the evaporation gas supply line downstream of the compressor and connected to the gas-liquid separator via the evaporation gas heat exchanger and provided with the pressure reducing valve; And
And a flash gas return line connected from the gas-liquid separator to the mixer. 10. The fuel cell system according to claim 9, wherein the flash gas return line includes:
And the gas-liquid separator is connected to the mixer via the flash gas heat exchanger. A ship characterized in that it comprises the evaporation gas remelting system according to any one of claims 1 to 10.

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