KR102053479B1 - Treatment system of liquefied gas - Google Patents

Abstract

Liquefied gas processing system according to an embodiment of the present invention, the boil-off gas supply line for supplying the boil-off gas generated in the liquefied gas storage tank; An evaporating gas compressor provided on the evaporating gas supply line and configured to pressurize the evaporating gas in multiple stages; An evaporating gas heat exchanger for heat-exchanging the boil-off gas pressurized by the boil-off gas compressor with the boil-off gas supplied from the liquefied gas storage tank; And a gas-liquid separator for separating gas and liquid from the boil-off gas pressurized by the boil-off gas compressor and heat-exchanged in the boil-off gas heat exchanger, wherein the boil-off gas heat exchanger includes the pressurized boil-off gas in the liquefied gas storage tank. The gas cooled by the supplied boil-off gas or the gas supplied from the gas-liquid separator and heat exchanged in the boil-off gas heat exchanger is joined to the boil-off gas supply line downstream from the boil-off gas heat exchanger.

Description

Treatment system of liquefied gas

The present invention relates to a liquefied gas treatment system.

Recently, liquefied gas such as liquefied natural gas and liquefied petroleum gas has been widely used in place of gasoline or diesel according to technology development.

Liquefied natural gas is liquefied by cooling methane obtained by refining natural gas collected from a gas field. It is a colorless and transparent liquid. Liquefied petroleum gas, on the other hand, is a liquid fuel made by compressing a gas containing propane (C3H8) and butane (C4H10), which come with oil from an oil field, at room temperature. Liquefied petroleum gas, like liquefied natural gas, is colorless and odorless and is widely used as a fuel for household, business, industrial, and automobile use.

Such liquefied gas is stored in a liquefied gas storage tank installed on the ground or in a liquefied gas storage tank provided in a ship which is a means of transporting the ocean, and liquefied natural gas is liquefied to a volume of 1/600. The liquefied petroleum gas is reduced by the liquefied propane is 1/260, butane is reduced to a volume of 1/230 has the advantage of high storage efficiency.

However, since liquefied gas is stored in a liquefied state by forcibly increasing the pressure or lowering the temperature, it is important to secure the thermal insulation of the liquefied gas storage tank due to fear of phase change due to external heat penetration. However, since the liquefied gas storage tank is not able to implement a perfect insulation, some liquefied gas stored in the liquefied gas storage tank is phase-changed into the evaporated gas gas by the heat transmitted from the outside.

At this time, the evaporated gas phase-changed into gas increases the internal pressure of the liquefied gas storage tank because the volume greatly increases, and when the internal pressure of the liquefied gas storage tank exceeds the pressure that the liquefied gas storage tank can withstand, the liquefied gas storage The tank may be damaged.

Therefore, in the related art, in order to maintain a constant internal pressure of the liquefied gas storage tank, a method of lowering the internal pressure of the liquefied gas storage tank by discharging the evaporated gas to the outside when necessary. Alternatively, the boil-off gas was discharged to the outside of the liquefied gas storage tank, and then liquefied using a separate reliquefaction device, and then recovered to the liquefied gas storage tank.

However, if the evaporated gas is simply discharged to the outside, pollution of the external environment may occur, and when using the reliquefaction device, problems such as cost and manpower required to equip and operate the reliquefaction device may occur. Therefore, the development of an effective treatment method of the boil-off gas generated by external thermal penetration is required.

As such a prior art, Korean Patent Publication No. 10-1289212 (2013.07.17) and the like are disclosed.

The present invention has been made to improve the prior art, an object of the present invention is to provide a liquefied gas treatment system that can lower the load of the evaporative gas compressor and improve the liquefaction efficiency using flash gas.

Liquefied gas processing system according to an embodiment of the present invention, the boil-off gas supply line for supplying the boil-off gas generated in the liquefied gas storage tank; An evaporating gas compressor provided on the evaporating gas supply line and configured to pressurize the evaporating gas in multiple stages; An evaporating gas heat exchanger for heat-exchanging the boil-off gas pressurized by the boil-off gas compressor with the boil-off gas supplied from the liquefied gas storage tank; And a gas-liquid separator for separating gas and liquid from the boil-off gas pressurized by the boil-off gas compressor and heat-exchanged in the boil-off gas heat exchanger, wherein the boil-off gas heat exchanger includes the pressurized boil-off gas in the liquefied gas storage tank. The gas cooled by the supplied boil-off gas or the gas supplied from the gas-liquid separator and heat exchanged in the boil-off gas heat exchanger is joined to the boil-off gas supply line downstream from the boil-off gas heat exchanger.

In the liquefied gas treatment system according to the present invention, as the mixing line is branched from the gas recovery line and joined to the boil-off gas compressor, the re-liquefaction efficiency may be improved by heat-exchanging the boil-off gas in which the flash gas is joined in the boil-off gas heat exchanger. . In addition, by joining upstream of the two-stage boil-off gas compressor, the load of the boil-off gas compressor can be reduced by reducing the volume of boil-off gas.

1 is a conceptual diagram of a liquefied gas treatment system according to an embodiment of the present invention.

The objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and the preferred embodiments associated with the accompanying drawings. In the present specification, in adding reference numerals to the components of each drawing, it should be noted that the same components as possible, even if displayed on the other drawings have the same number as possible. In addition, in describing the present invention, if it is determined that the detailed description of the related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

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

1 is a conceptual diagram of a liquefied gas treatment system according to an embodiment of the present invention, Figure 2 is a view showing a lubricant separator of a liquefied gas treatment system according to an embodiment of the present invention.

As shown in FIG. 1, a liquefied gas treatment system 1 according to an exemplary embodiment of the present invention includes a liquefied gas storage tank 10, a customer 20, an evaporative gas compressor 50, and an evaporative gas heat exchanger ( 60), the boil-off gas decompressor 80 and the gas-liquid separator 100.

Hereinafter, in the present specification, liquefied gas may be used to encompass all gaseous fuels which are generally stored in a liquid state, such as LNG or LPG, ethylene, ammonia, and the like. Can be expressed as This can be applied to the boil-off gas as well. In addition, LNG may be used for the purpose of encompassing not only liquid NG (Natural Gas) but also supercritical NG, for convenience, and evaporation gas may be used to include not only gaseous evaporation gas but also liquefied evaporation gas. have.

The liquefied gas storage tank 10 stores the liquefied gas to be supplied to the demand destination 20. The liquefied gas storage tank 10 should store the liquefied gas in a liquid state, where the liquefied gas storage tank 10 may have a pressure tank form.

The liquefied gas storage tank 10 may be designed to withstand a pressure of 1 bar to 10 bar (for example, 6 bar) consisting of a dual structure tank (not shown) and a heat insulating part (not shown).

Here, a forced vaporizer (not shown) may be provided between the liquefied gas storage tank 10 and the boil-off gas compressor 50, and the forced vaporizer may be operated when the flow rate of the boil-off gas is insufficient, thereby requiring the user 20. May increase the flow rate of the boil-off gas.

The demand destination 20 is driven through the boil-off gas supplied from the liquefied gas storage tank 10 to generate power. In this case, the demand source 20 may be a high-pressure engine and a gas fuel engine (eg, MEGI).

For example, the demand source 20 may be an engine for driving the propeller, but may be an engine for power generation or an engine for generating other power. In other words, the present embodiment does not particularly limit the type of the demand destination 20. However, the demand source 20 may be an internal combustion engine generating a driving force by the combustion of the boil-off gas and the flash gas.

The demand destination 20 may receive the boil-off gas pressurized by the boil-off gas compressor 50 to obtain a driving force. The state of the boil-off gas supplied to the customer 20 may vary depending on the condition required by the customer 20.

An evaporative gas supply line 16 is installed to transfer the evaporated gas from the liquefied gas storage tank 10 to the demand destination 20. An evaporative gas heat exchanger 60 and an evaporative gas compressor 50 are provided on the evaporated gas supply line 16. ), Demand destination 20 and the like.

In this embodiment, the boil-off gas supply line 16 is meant to include a re-liquefaction line 16A and a fuel supply line 16B, which will be described later, and the fuel supply line 16B is a demand source 20 from the boil-off compressor 50. ) Is connected to supply the pressurized boil-off gas to the demand destination (20). At this time, the fuel supply valve (not shown) is installed in the boil-off gas supply line 16, the amount of the boil-off gas can be adjusted according to the opening degree of the fuel supply valve.

The boil-off gas compressor 50 pressurizes the boil-off gas generated in the liquefied gas storage tank 10. The boil-off gas compressor 50 may pressurize the boil-off gas generated and discharged from the liquefied gas storage tank 10 and supply the boil-off gas to the boil-off gas heat exchanger 60 or the customer 20. The boil-off gas compressor 50 is provided in plurality and can pressurize the boil-off gas in multiple stages. For example, the evaporation gas compressor 50 may be provided with five to allow the evaporation gas to be pressurized five times.

Here, the reliquefaction line 16A may be branched between the boil-off gas compressor 50 and the demand source 20 and connected to the boil-off gas heat exchanger 60. That is, the boil-off gas supply line 16 forms the fuel supply line 16B connected to the demand source 20 from the boil-off gas compressor 50 or the reliquefaction line 16A connected to the boil-off gas heat exchanger 60. Can be achieved. At this time, a valve (not shown) is provided on the boil-off gas supply line 16 at the branch point to the boil-off gas heat exchanger 60, so that the flow rate of the boil-off gas can be controlled. In the present embodiment, the reliquefaction line 16A illustrates branching downstream of the third boil-off gas compressor 50 in the flow of boil-off gas among the five boil-off gas compressors 50. It may be branched downstream of 50.

A boil-off gas cooler (not shown) is provided downstream of each boil-off gas compressor 50 between the boil-off gas compressors 50, and is pressurized by the boil-off gas compressor 50 to raise the temperature of the boil-off gas. Can be lowered again. By increasing the pressure of the boil-off gas with the boil-off gas compressor 50, it is possible to easily liquefy the boil-off gas.

The boil-off gas heat exchanger 60 is provided between the liquefied gas storage tank 10 and the boil-off gas compressor 50 on the boil-off gas supply line 16 and stores the boil-off gas and the liquefied gas pressurized by the boil-off gas compressor 50. The boil-off gas supplied from the tank 10 may be heat exchanged. The boil-off gas exchanged in the boil-off gas heat exchanger 60 may be supplied to the boil-off gas decompressor 80 or the boil-off gas compressor 50.

That is, the boil-off gas which is pressurized in the multi-stage by the boil-off gas compressor 50 and then recovered by the boil-off gas decompressor 80 and the boil-off gas newly supplied from the liquefied gas storage tank 10 exchange heat in the boil-off gas heat exchanger 60. do.

In addition, the flash gas separated from the gas-liquid separator 100 may be used for heat exchange via the boil-off gas heat exchanger 60. The boil-off gas heat exchanger 60 is provided in the reliquefaction line 16A, and the boil-off gas pressurized by the boil-off gas compressor 50 and the boil-off gas supplied from the liquefied gas storage tank 10 are separated from the gas-liquid separator 100. The flash gas can be heat exchanged.

That is, the boil-off gas heat exchanger (60) is pressurized by the boil-off gas compressor (50) and recovered along the reliquefaction line (16A) branched upstream of the demand destination 20, and in the liquefied gas storage tank (10) Heat the boil-off gas supplied. The boil-off gas heat exchanger 60 exchanges the boil-off gas pressurized by the boil-off gas compressor 50 and recovered along the boil-off gas supply line 16 with the flash gas supplied through the gas-recovery line 17.

At this time, the boil-off gas heat exchanger 60 cools the boil-off gas recovered along the reliquefaction line 16A to the boil-off gas supplied from the liquefied gas storage tank 10 or flashes supplied through the gas recovery line 17. Can be cooled by gas. In this case, the boil-off gas recovered along the reliquefaction line 16A may be first cooled by the boil-off gas discharged from the liquefied gas storage tank 10 and secondly by the flash gas.

The boil-off gas heat exchanger 60 supplies the boil-off gas supplied from the liquefied gas storage tank 10 to the boil-off gas compressor 50, and converts the boil-off gas cooled by the boil-off gas and the flash gas into the boil-off gas decompressor. 80 can be supplied. In this case, since the boil-off gas supplied to the boil-off gas decompressor 80 is cooled not only by the boil-off gas but also by the flash gas, the liquefaction efficiency by the reduced pressure can be greatly increased.

The flash gas passing through the boil-off gas heat exchanger 60 may be supplied to a gas combustion unit 70 that burns fuel, a boiler (not shown), or a separate heterogeneous fuel engine (DFDE) (not shown). At this time, the gas recovery line 17 may extend from the boil-off gas heat exchanger 60 to the gas combustion unit 70.

In this embodiment, the mixing line 17A may be branched from the gas recovery line 17. The mixing line 17A joins the flash gas branched off in the gas recovery line 17 and heat exchanged to the first stage downstream of the first boil-off gas compressor 50 in the flow of the boil-off gas in the boil-off gas compressor 50. Here, the mixing line 17A may be provided downstream of the boil-off gas compressor 50 and downstream of the boil-off gas cooler. That is, it may be joined between the boil-off gas cooler of the first stage boil-off gas compressor 50 and the boil-off gas compressor 50 of the second stage. In this case, the boil-off gas cooler may be omitted in the first stage downstream of the boil-off gas compressor 50.

In addition, a valve (not shown) is provided on the gas recovery line 17 where the mixing line 17A is branched to adjust the amount of flash gas supplied to the boil-off gas compressor 50 and the gas combustion unit 70. .

In this way, as the mixing line 17A branches from the gas recovery line 17 and merges into the boil-off gas compressor 50, the boil-off gas in which the flash gas is joined is heat-exchanged in the boil-off gas heat exchanger 50, thereby re-liquefying efficiency. This can be improved. In addition, by joining upstream of the two-stage boil-off gas compressor 50, the load of the boil-off gas compressor 50 can be reduced by reducing the volume of the boil-off gas.

The boil-off gas decompressor 80 depressurizes the boil-off gas exchanged by the boil-off gas heat exchanger 60 after being pressurized by the boil-off gas compressor 50. For example, the boil-off gas decompressor 80 may reduce the boil-off gas to 1 bar to 10 bar, and the boil-off gas may be reduced to 1 bar when the boil-off gas is liquefied and transferred to the liquefied gas storage tank 10. Cooling effect can be achieved. For example, the boil-off gas reducer 80 may reduce the boil-off gas pressurized to 300 bar by the boil-off gas compressor 50 to 1 bar. This, the boil-off gas reducer 80 may be made of Joule Thompson valve.

The gas-liquid separator 100 separates gas from the boil-off gas reduced in the boil-off gas reducer 80. In the gas-liquid separator 100, the boil-off gas is separated into a liquid and a gas so that the liquid is supplied to the liquefied gas storage tank 10, and the gas may be recovered to the boil-off gas compressor 50 as a flash gas. Here, the boil-off gas reduced in the boil-off gas decompressor 80 may be easy to liquefy the boil-off gas by the lowered temperature, recover the liquefied gas storage tank 10, the flash gas generated in the gas-liquid separator 100 It is used for heat exchange without throwing away.

When the boil-off gas is separated into liquid and gas in the gas-liquid separator 100, the liquefied boil-off gas and the flash gas are respectively vaporized with the liquefied gas storage tank 10 through the liquid recovery line 18 and the gas recovery line 17. It may be recovered to the gas heat exchanger (60). The liquid recovery line 18 is connected from the gas-liquid separator 100 to the liquefied gas storage tank 10 to recover the liquid vaporized gas into the liquefied gas storage tank 10, and the gas recovery line 17 is a gas-liquid separator ( 100 may be connected to the gas combustion unit 70 or connected to the boil-off gas compressor 50 to recover the flash gas upstream of the boil-off gas compressor 50 to prevent the flash gas from being wasted and wasted.

In addition, in the present embodiment, the boil-off gas heated to a temperature of about 45 ° is recovered to the boil-off gas heat exchanger 60 and supplied to the liquefied gas storage tank 10 at about -100 ° and about 150 °. By heat exchange with the flash gas, it is cooled to a temperature of about -95 and is supplied to the boil-off gas decompressor 80. At this time, the boil-off gas in the boil-off gas decompressor 80 is cooled by the reduced pressure may have a pressure of about 3bar and a temperature of about -150.2 degrees.

At this time, as the boil-off gas has a temperature lower than the boiling point at 3 bar, at least a part may be liquefied, and the remainder may exist as a flash gas in a gaseous state. In this case, the flash gas also has a state of about -150 degrees, and the flash gas of -150 degrees may be supplied from the gas-liquid separator 100 to the boil-off gas heat exchanger 60 and used to cool the boil-off gas.

As such, in this embodiment, the boil-off gas supplied to the gas-liquid separator 100 is sufficiently cooled by the boil-off gas and the flash gas in the boil-off gas heat exchanger 60, and then reduced to 3 bar in the boil-off gas decompressor 80 and cooled Therefore, the liquefaction efficiency of the boil-off gas can be improved.

In addition, in the present embodiment, the liquefied evaporated gas may be recovered to the liquefied gas storage tank 10, and the flash gas generated in the gas-liquid separator 100 may be recovered to the evaporative gas heat exchanger 60 to heat exchange the evaporated gas. .

When the boil-off gas is separated into liquid and gas in the gas-liquid separator 100, the liquefied boil-off gas and the flash gas are respectively vaporized with the liquefied gas storage tank 10 through the liquid recovery line 18 and the gas recovery line 17. It may be recovered to the gas heat exchanger (60).

The liquid recovery line 18 is connected from the gas-liquid separator 100 to the liquefied gas storage tank 10 to recover the liquid vaporized gas into the liquefied gas storage tank 10, and the gas recovery line 17 is a gas-liquid separator ( 100 is connected to the boil-off gas heat exchanger 60 to recover the flash gas to the boil-off gas heat exchanger 60 to heat exchange the boil-off gas.

As such, in the present embodiment, as the mixing line 17A branches from the gas recovery line 17 and merges into the boil-off gas compressor 50, the boil-off gas in which the flash gas is joined is transferred from the boil-off gas heat exchanger 50. Re-liquefaction efficiency can be improved by heat exchange. In addition, as it is joined upstream of the two-stage boil-off gas compressor 50, the load of the boil-off gas compressor 50 may be reduced due to the volume reduction of the boil-off gas.

Although the present invention has been described in detail through specific examples, it is intended to describe the present invention in detail, and the present invention is not limited thereto, and should be understood by those skilled in the art within the technical spirit of the present invention. It is obvious that the modifications and improvements are possible.

All simple modifications and variations of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be apparent from the appended claims.

1: liquefied gas treatment system 10: liquefied gas storage tank
16: boil-off gas supply line 16A: reliquefaction line
16B: Fuel Supply Line 17: Gas Recovery Line
18: liquid recovery line 20: demand source
50: boil-off gas compressor 60: boil-off gas heat exchanger
70: gas combustion unit 80: boil-off gas pressure reducer
100: gas-liquid separator

Claims (1)

An boil-off gas supply line for supplying boil-off gas generated in the liquefied gas storage tank;
An evaporative gas compressor provided on the evaporative gas supply line and provided in multiple stages including a low pressure stage and a high pressure stage, and pressurizing the boiled gas into multiple stages to supply the engine to the engine;
An evaporative gas heat exchanger for heat-exchanging at least part of the evaporated gas recovered from the low pressure stage downstream of the evaporative gas compressor after being pressurized by the evaporative gas compressor and the evaporated gas supplied from the liquefied gas storage tank ; And
A gas-liquid separator pressurized by the boil-off gas compressor to separate gas and liquid from the boil-off gas heat-exchanged in the boil-off gas heat exchanger,
The boil-off gas heat exchanger,
The pressurized boil-off gas is cooled with the boil-off gas supplied from the liquefied gas storage tank and the gas supplied from the gas-liquid separator,
The gas heat exchanged in the boil-off gas heat exchanger,
Liquefied gas treatment system, characterized in that to join the boil-off gas supply line at the intermediate stage of the boil-off gas compressor.

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