KR102288013B1 - Reliquefaction system for boil-off gas and ship having the same - Google Patents

Abstract

The present invention relates to a BOG reliquefaction system and a ship, comprising: a BOG compressor for compressing BOG generated in a liquefied gas storage tank in multiple stages; a boil-off gas heat exchanger for exchanging the boil-off gas compressed in the boil-off gas compressor with the boil-off gas flowing into the boil-off gas compressor; a pressure reducing valve for decompressing the boil-off gas that has been compressed in the boil-off gas compressor and then heat-exchanged in the boil-off gas heat exchanger; a lubricant filter provided downstream of the pressure reducing valve; and a lubricating oil processing unit injecting the high-temperature gas compressed in the BOG compressor into the BOG heat exchanger in order to remove lubricating oil mixed with BOG at the high-pressure stage of the BOG compressor and introduced into the BOG heat exchanger, The lubricating oil processing unit may be configured such that the high-temperature gas compressed in the BOG compressor is supplied to a consumer via the BOG heat exchanger, or the high-temperature gas compressed in the BOG compressor is supplied to the BOG heat exchanger, the pressure reducing valve and the lubricant. It is characterized in that it is supplied to the consumer via a filter.

Description

BOG reliquefaction system and ship {Reliquefaction system for boil-off gas and ship having the same}

The present invention relates to a boil-off gas reliquefaction system and a ship.

According to recent technology development, liquefied gas such as liquefied natural gas (Liquefied Natural Gas), liquefied petroleum gas (Liquefied Petroleum Gas), etc. is used as a fuel for an engine by replacing gasoline or diesel.

Liquefied natural gas is liquefied by cooling and liquefying methane obtained by refining natural gas collected from a gas field. It is a colorless and transparent liquid with few pollutants and high calorific value. On the other hand, liquefied petroleum gas is a fuel made into a liquid by compressing the gas containing propane (C3H8) and butane (C4H10) together with petroleum from oil fields 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 automobile use.

Such liquefied gas is stored in a liquefied gas storage tank provided in a ship to be used as fuel for an engine provided in the ship. Liquefied natural gas is reduced to about 1/600 in volume by liquefaction, and liquefied petroleum gas is It has the advantage of being reduced to about 1/260 of a volume by a high storage efficiency.

However, since the liquefied gas is stored in a cryogenic state in which the temperature is lowered below the boiling point and forcibly liquefied, as heat penetrates from the outside, a portion of the liquefied gas is naturally vaporized and changed into boil-off gas.

At this time, since the volume of the boil-off gas changed into gas significantly increases, it becomes a factor to increase the internal pressure of the liquefied gas storage tank. The tank may be damaged.

Therefore, in the prior art, in order to keep the internal pressure of the liquefied gas storage tank constant, the BOG is discharged to the outside and burned to lower the internal pressure of the liquefied gas storage tank, or the BOG is liquefied through a re-liquefaction device using a separate refrigerant. After the liquefied gas storage tank, a method of recovery was used.

However, when the boil-off gas is simply discharged to the outside, an environmental pollution problem occurs. Therefore, there is a need to develop an effective method for treating boil-off gas generated by external heat penetration.

The present invention was created to improve the prior art, and liquefy the boil-off gas through heat exchange and pressure reduction so that the re-liquefaction device can be omitted or reduced. An object of the present invention is to provide a BOG reliquefaction system and a ship capable of efficiently processing lubricating oil.

BOG reliquefaction system according to an embodiment of the present invention comprises: a BOG compressor for compressing BOG generated in a liquefied gas storage tank in multiple stages; a boil-off gas heat exchanger for exchanging the boil-off gas compressed in the boil-off gas compressor with the boil-off gas flowing into the boil-off gas compressor; a pressure reducing valve for decompressing the boil-off gas that has been compressed in the boil-off gas compressor and then heat-exchanged in the boil-off gas heat exchanger; a lubricant filter provided downstream of the pressure reducing valve; and a lubricating oil processing unit injecting the high-temperature gas compressed in the BOG compressor into the BOG heat exchanger in order to remove lubricating oil mixed with BOG at the high-pressure stage of the BOG compressor and introduced into the BOG heat exchanger, The lubricating oil processing unit may be configured such that the high-temperature gas compressed in the BOG compressor is supplied to a consumer via the BOG heat exchanger, or the high-temperature gas compressed in the BOG compressor is supplied to the BOG heat exchanger, the pressure reducing valve and the lubricant. It is characterized in that it is supplied to the consumer via a filter.

Specifically, a boil-off gas supply line connected from the liquefied gas storage tank to the consumer via at least one stage of the boil-off gas compressor; a boil-off gas return line branched from the downstream of the boil-off gas compressor and connected to the liquefied gas storage tank via the boil-off gas heat exchanger and the pressure reducing valve; a first lubricating oil treatment line branched from the downstream of the boil-off gas compressor in the boil-off gas supply line and joined to the boil-off gas supply line after passing through the boil-off gas heat exchanger; and a second lubricating oil processing line branched from the lubricating oil filter and joined to the boil-off gas supply line.

Specifically, the first lubricating oil treatment line may be branched from the boil-off gas return line upstream of the pressure reducing valve via the boil-off gas heat exchanger to join the boil-off gas supply line.

Specifically, a point at which the second lubricating oil treatment line joins the BOG supply line may be downstream from a point at which the first lubricant treatment line joins the BOG supply line.

Specifically, the lubricating oil processing unit includes a lubricating oil processing valve provided in the second lubricating oil processing line, wherein the lubricating oil processing valve applies pulsation to the high-temperature gas by adjusting the opening degree to the boil-off gas heat exchanger and the pressure reducing valve and lubricating oil of the lubricating oil filter may be removed.

Specifically, a boil-off gas bypass line for passing the boil-off gas discharged from the liquefied gas storage tank to the boil-off gas compressor by bypassing the boil-off gas heat exchanger; and a boil-off gas bypass valve for controlling the flow of the boil-off gas bypass line, wherein the boil-off gas bypass valve receives high-temperature boil-off gas compressed in the boil-off gas compressor to remove the lubricating oil introduced into the boil-off gas heat exchanger. When injected into the boil-off gas heat exchanger, the low-temperature boil-off gas discharged from the liquefied gas storage tank may flow to the boil-off gas bypass line so that the boil-off gas injected into the boil-off gas heat exchanger can maintain a high temperature state.

A ship according to an embodiment of the present invention is characterized in that it has the boil-off gas reliquefaction system.

In the BOG reliquefaction system and vessel according to the present invention, in the process of compressing BOG to a high pressure in order to decompress and liquefy BOG, the lubricating oil used in the BOG compressor of the high-pressure stage flows into the BOG heat exchanger, etc. In case of interrupting the flow, the lubricant can be effectively removed to ensure the reliquefaction efficiency.

1 is a side view of a vessel having a boil-off gas reliquefaction system according to the present invention.
2 is a conceptual diagram of a BOG reliquefaction system according to a first embodiment of the present invention.
3 is a cross-sectional view of the gas-liquid separator of the boil-off gas reliquefaction system according to the first embodiment of the present invention.
4 is a cross-sectional view of the gas-liquid separator in the boil-off gas reliquefaction system according to the second embodiment of the present invention.
5 is a cross-sectional view of the gas-liquid separator in the boil-off gas reliquefaction system according to the third embodiment of the present invention.
6 is a cross-sectional view of the gas-liquid separator in the boil-off gas reliquefaction system according to the fourth embodiment of the present invention.
7 is a conceptual diagram of a BOG reliquefaction system according to a fifth embodiment of the present invention.
8 is a conceptual diagram of a BOG reliquefaction system according to a sixth embodiment of the present invention.
9 is a conceptual diagram of a BOG reliquefaction system according to a seventh embodiment of the present invention.
10 is a conceptual diagram of a BOG reliquefaction system according to an eighth embodiment of the present invention.
11 is a conceptual diagram of a BOG reliquefaction system according to a ninth embodiment of the present invention.
12 is a conceptual diagram of a BOG reliquefaction system according to a ninth embodiment of the present invention.
13 is a conceptual diagram of a BOG reliquefaction system according to the present invention.
14 is a conceptual diagram of a BOG reliquefaction system according to the present invention.
15 is a graph illustrating a gas processing state of the BOG reliquefaction system according to the present invention.
16 is a conceptual diagram of a BOG reliquefaction system according to a tenth 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 preferred embodiments taken in conjunction with the accompanying drawings. In the present specification, in adding reference numbers to the components of each drawing, it should be noted that only the same components are given the same number as possible even though they are indicated on different drawings. In addition, in describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Hereinafter, the liquefied gas is a substance that has a gaseous state at room temperature due to a lower boiling point than room temperature, and may be LPG, LNG, ethane, or the like, and may refer to Liquefied Natural Gas (LNG) by way of example. Also, boil-off gas may refer to BOG (Boil-Off Gas), which is a liquefied gas that is naturally vaporized. In addition, it should be noted that the current state of liquefied gas and boil-off gas (gas, liquid, etc.) is not limited by the name. As an example, boil-off gas includes a case in which it is in a liquid state by re-liquefaction.

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

1 is a side view of a vessel having a boil-off gas reliquefaction system according to the present invention.

1, the vessel 1 to which the boil-off gas reliquefaction system 2 according to the present invention is applied may be a liquefied gas carrier that mounts a plurality of liquefied gas storage tanks 10 in the longitudinal direction inside the hull, , for example, the vessel 1 may be an LNG carrier.

The liquefied gas storage tank 10 provided in the ship of the ship 1 stores the liquefied gas. The liquefied gas storage tank 10 may liquefy a gas having a boiling point lower than room temperature and store it in a cryogenic state.

The liquefied gas storage tank 10 may be formed of a membrane type, an independent type, a pressure vessel type, or the like, but is not particularly limited. However, regardless of the type, some of the liquefied gas is naturally vaporized inside the liquefied gas storage tank 10 to generate boil-off gas, which may be a problem because the internal pressure of the liquefied gas storage tank 10 rises. .

Therefore, in this embodiment, BOG can be discharged to the outside of the liquefied gas storage tank 10 according to the internal pressure of the liquefied gas storage tank 10 , and the discharged BOG is re-liquefied to the liquefied gas storage tank 10 . can be returned.

Alternatively, in the present invention, boil-off gas may be used as a fuel for the consumer 3 . At this time, the demand 3 may be provided in the ship 1 , for example, a high-pressure engine 3a (ME) for propelling the ship 1 . -GI engine, XDF engine, etc.), a low-pressure engine 3b (DFDE power generation engine) and/or a gas combustion unit 3c (GCU) for covering the internal power load of the ship 1 .

However, in the present specification, the demand (3) is limited to the high-pressure demand (3) such as the high-pressure engine (3a) excluding the low-pressure demand (3) such as the low-pressure engine (3b) and the gas combustion device (3c). let me know

Of course, in addition to the boil-off gas generated from the liquefied gas storage tank 10, liquefied gas can also be used as a fuel for the consumer 3, and for this purpose, a forced vaporizer (shown) between the liquefied gas storage tank 10 and the consumer 3 Not shown), a heavy carbon separator (not shown), a high-pressure pump (not shown), etc., known components necessary for supplying liquefied gas may be provided.

A cabin (not shown), an engine casing (not shown), etc. are provided on the upper deck of the vessel 1, and the components of the boil-off gas reliquefaction system 2 may also be provided on the upper deck. However, the installation positions of the various components constituting the boil-off gas reliquefaction system 2 may not be particularly limited.

Note that the vessel 1 according to the present invention is an expression encompassing various offshore plants such as FPSOs and FSRUs capable of storing liquefied gas in addition to liquefied gas carriers.

2 is a conceptual diagram of a boil-off gas reliquefaction system according to a first embodiment of the present invention, and FIG. 3 is a cross-sectional view of a gas-liquid separator of the boil-off gas reliquefaction system according to the first embodiment of the present invention.

2 and 3 , the BOG reliquefaction system 2 according to the first embodiment of the present invention includes a BOG compressor 20, a BOG heat exchanger 30, a pressure reducing valve 40, and a gas-liquid It includes a separator 50 , a lubricating oil processing unit 60 , and lubricating oil filters 70a , 70b and 70c .

The BOG compressor 20 compresses BOG generated in the liquefied gas storage tank 10 in multiple stages and supplies it to the consumer 3 . The BOG compressor 20 may be of a centrifugal type, a reciprocating type, a screw type, and the like, and a plurality of BOG compressors are provided in series to compress BOG in multiple stages to change the BOG compressor to a high pressure. In addition, the BOG compressor 20 may be provided in parallel for backup or load sharing.

The boil-off gas compressor 20 may compress the boil-off gas discharged from the liquefied gas storage tank 10 to about 1 bar to a high pressure of 200 bar or more (for example, 200 to 400 bar). For this, the boil-off gas compressor 20 may be provided in five stages, for example.

The 5-stage BOG compressor 20 may be divided into a BOG compressor 20a of a low pressure stage and a BOG compressor 20b of a high pressure stage. Stages 1 to 3 of the 5 stages may be referred to as a low-pressure stage BOG compressor 20a, and stages 4 and 5 may be referred to as a high-pressure stage BOG compressor 20b.

The criterion for classifying the BOG compressor 20a of the low pressure stage and the BOG compressor 20b of the high pressure stage depends on whether the lubricating oil L is mixed into the BOG. In the case of the boil-off gas compressor 20a of the low pressure stage, the lubricating oil L used when the boil-off gas compressor 20 is driven in the process of compressing the boil-off gas does not flow into the boil-off gas, whereas the boil-off gas compressor 20b of the high pressure stage ), the lubricating oil (L) used for driving the BOG compressor 20 may be introduced into the BOG as the BOG is compressed at a high pressure.

Therefore, the BOG compressed from the 5th stage BOG compressor 20 to the 3rd stage is in a state in which lubricating oil (L) is not mixed, but the BOG compressed after the 4th stage is in a state in which the lubricating oil (L) is mixed. can be problematic. In order to solve this problem, the present invention includes various configurations described below.

A boil-off gas supply line 21 is provided from the liquefied gas storage tank 10 to the consumer 3 , and the boil-off gas supply valves 211a and 211b and the boil-off gas compressor 20 are disposed in the boil-off gas supply line 21 . The BOG is discharged from the liquefied gas storage tank 10 and delivered to the consumer 3 via the BOG compressor 20 .

However, surplus BOG that cannot be consumed by the consumer 3 may be generated, and the surplus BOG may be liquefied and returned to the liquefied gas storage tank 10, for this purpose, BOG in the BOG supply line 21 A boil-off gas return line 31 may be branched downstream of the compressor 20 .

The BOG flow from the BOG supply line 21 to the BOG return line 31 is a high-pressure BOG return valve 311 provided in the BOG return line 31 and/or the BOG supply line 21 . can be controlled by

In the downstream of the BOG compressor 20 in the BOG supply line 21, a separator 22, a coalescer 23 (coalescer), etc. This may be provided, and a gas valve train 24 (Gas valve train) for controlling the flow rate of boil-off gas may be provided upstream of the consumer 3 .

Upstream of the boil-off gas compressor 20b of the high-pressure stage in the boil-off gas supply line 21 , the low-pressure boil-off gas supply line 212 may branch. For example, the low-pressure BOG supply line 212 may be connected downstream of the second stage of the BOG compressor 20a of the low-pressure stage, and is connected to the low-pressure demander 3 .

The demand source 3 connected to the BOG supply line 21 may be a high pressure demand source 3 , and the demand source 3 connected to the low pressure BOG supply line 212 may be a low pressure demand source 3 . In addition, the high pressure demand source 3 may be a propulsion engine, and the low pressure demand source 3 may be a power generation engine, etc., the BOG supply line 21 is a main stream, and the low pressure BOG supply line 212 is a side stream. (side stream) may be referred to.

The low-pressure consumer 3 may be a DFDE low-pressure engine 3b as shown in the figure, or a gas combustion device 3c that burns and discards boil-off gas. The pressure of the boil-off gas required by the low-pressure consumer 3 may be around 10 bar.

The low pressure BOG supply line 212 is provided with a low pressure BOG supply valve 213 for controlling the flow of BOG in the same way as/similarly to the BOG supply valves 211a and 211b provided in the BOG supply line 21 . can be

The BOG heat exchanger 30 exchanges heat between BOG compressed in the BOG compressor 20 and BOG flowing into the BOG compressor 20 . The boil-off gas return line 31 described above is branched from the downstream of the boil-off gas compressor 20 from the boil-off gas supply line 21 and can be connected to the liquefied gas storage tank 10 via the boil-off gas heat exchanger 30 , etc. there is. In addition, the BOG supply line 21 may also be connected to the consumer 3 via the BOG heat exchanger 30 and the BOG compressor 20 in sequence from the liquefied gas storage tank 10 .

Accordingly, the boil-off gas heat exchanger 30 is parallel to the boil-off gas supply line 21 and a flow path through which low-pressure/low-temperature boil-off gas flows (not shown), and parallel with the boil-off gas return line 31 and high pressure/high temperature may be provided with a flow path (not shown) through which the boil-off gas of (not shown) may be provided.

The boil-off gas heat exchanger 30 converts the high-temperature boil-off gas introduced along the boil-off gas return line 31 after being compressed by the boil-off gas compressor 20 to the low-temperature boil-off gas discharged from the liquefied gas storage tank 10 . can be cooled with Since the BOG flowing along the BOG return line 31 must be returned to the liquefied gas storage tank 10 after liquefaction, the BOG heat exchanger 30 performs pre-cooling before liquefaction to increase the liquefaction efficiency.

However, the BOG compressed in the BOG compressor 20b of the high-pressure stage may contain lubricating oil (L), and the BOG mixed with the lubricant (L) is mixed with the BOG along the BOG return line 31 ( 30) can be introduced.

At this time, the lubricating oil (L) is a material having a significantly higher boiling point than the boil-off gas, and may be in a liquid state at room temperature, may be sufficiently solidified with a slight cooling, and may have a high viscosity.

It is not a problem if the flow is continuously made in the flow path of the boil-off gas heat exchanger 30, but if the flow in the boil-off gas heat exchanger 30 is reduced due to the absence of excess boil-off gas, the boil-off gas heat exchanger ( 30), the lubricating oil (L) may become stuck in the flow path, which may obstruct the flow.

Therefore, in the present invention, in order to solve the problem of blocking the flow of boil-off gas due to lubricating oil L in the components provided downstream of the boil-off gas heat exchanger 30 and the boil-off gas heat exchanger 30, high-temperature gas, etc. It can be used to melt the lubricant (L) and push it out. This will be described later.

This embodiment may include an auxiliary boil-off gas heat exchanger 32 , wherein the auxiliary boil-off gas heat exchanger 32 discharges the high-pressure boil-off gas cooled in the boil-off gas heat exchanger 30 from the gas-liquid separator 50 . It can be cooled by vapor phase boil-off gas.

To this end, the auxiliary BOG heat exchanger 32 includes a flow path (not shown) connected downstream of the BOG heat exchanger 30 from the BOG return line 31, and a gaseous BOG delivery line 51 to be described later. It may have a structure having a flow path (not shown) connected to the upstream of the boil-off gas heat exchanger (30). However, the auxiliary BOG heat exchanger 32 may not have a flow path through which BOG discharged from the liquefied gas storage tank 10 and delivered to the BOG compressor 20 flows.

The auxiliary BOG heat exchanger 32 may additionally cool the high-pressure BOG cooled by the gaseous BOG in the BOG heat exchanger 30 as a gaseous BOG. That is, the high-pressure BOG compressed by the BOG compressor 20 and flowing along the BOG return line 31 is the low-temperature BOG discharged from the liquefied gas storage tank 10 in the BOG heat exchanger 30 and auxiliary After being first cooled by the gaseous BOG delivered from the BOG heat exchanger 32 , the auxiliary BOG heat exchanger 32 may be secondarily cooled by the BOG delivered from the gas-liquid separator 50 .

Of course, the auxiliary BOG heat exchanger 32 may be omitted, and the BOG heat exchanger 30 and the auxiliary BOG heat exchanger 32 may be provided integrally. That is, the boil-off gas heat exchanger 30 may be of a type including the auxiliary boil-off gas heat exchanger 32 inside the internal flow path structure.

The pressure reducing valve 40 depressurizes the boil-off gas that has been compressed in the boil-off gas compressor 20 and then heat-exchanged in the boil-off gas heat exchanger 30 . In the present invention, the pressure reducing valve 40 may be a Joule-Thompson valve, but it should be noted that it can be replaced with various means capable of lowering the pressure, such as an expander.

BOG may be compressed to about 50 bar by the BOG compressor 20a of the low pressure stage and compressed to 200 bar or more by the BOG compressor 20b of the high pressure stage, and then cooled in the BOG heat exchanger 30 . However, even if the BOG is compressed to a high pressure and the boiling point is increased, the BOG is not sufficiently liquefied by cooling in the BOG heat exchanger 30 .

Therefore, the present invention can take advantage of the effect that the temperature drops when the pressure is reduced by using the pressure reducing valve 40 . The pressure reducing valve 40 may reduce the high-pressure boil-off gas of 200 bar or more to about 1 bar similar to the internal pressure of the liquefied gas storage tank 10, and the temperature of the boil-off gas may drop below the boiling point during decompression.

The pressure reducing valve 40 is provided on the boil-off gas return line 31 , and unlike the drawing, a plurality of pressure reducing valves 40 may be provided in series on the boil-off gas return line 31 . Alternatively, a variant in which the Joule-Thompson valve and the expander are provided in series is also possible.

The gas-liquid separator 50 separates the boil-off gas pressure-reduced by the pressure reducing valve 40 into gas-liquid. BOG may be liquefied as it is cooled in the BOG heat exchanger 30 and reduced in pressure at the pressure reducing valve 40, but complete reliquefaction may not be achieved depending on the circumstances, and it is contained in BOG and has a very low boiling point, such as nitrogen. Some substances may remain unliquefied.

At this time, the gaseous BOG remaining in the gaseous state may be separated from the gas-liquid separator 50 and may not flow into the liquefied gas storage tank 10 , and the liquid BOG in the liquid state may pass through the gas-liquid separator 50 . It is returned to the liquefied gas storage tank 10 along the boil-off gas return line 31 connected to the liquefied gas storage tank 10 . At this time, a liquid boil-off gas return valve 312 may be provided in the boil-off gas return line 31 between the gas-liquid separator 50 and the liquefied gas storage tank 10 .

The gas-liquid separator 50 may return the liquid boil-off gas (G) to the liquefied gas storage tank 10 and deliver the gaseous boil-off gas to the boil-off gas heat exchanger 30 . Since the vapor phase boil-off gas transferred from the gas-liquid separator 50 to the boil-off gas heat exchanger 30 is cooled by pressure reduction by the pressure reducing valve 40 , it is compressed in the boil-off gas compressor 20 and is compressed in the boil-off gas heat exchanger 30 . It can be used to cool the high-pressure boil-off gas flowing into the furnace.

In addition, the gas-liquid separator 50 may deliver the vapor phase BOG to the BOG compressor 20 through the BOG heat exchanger 30 . To this end, the gas-liquid separator 50 is provided with a vapor-phase boil-off gas delivery line 51, the vapor-phase boil-off gas delivery line 51 is a boil-off gas supply line ( 21), and the gaseous BOG delivery line 51 may be provided with a gaseous BOG delivery valve 511 for controlling the flow of gaseous BOG in the upstream and/or downstream of the BOG heat exchanger 30. there is.

The point at which the vapor phase BOG delivery line 51 is connected to the BOG supply line 21 may be upstream of the BOG compressor 20 , and thus the BOG compressor 20 is discharged from the liquefied gas storage tank 10 . In addition to the BOG being used, since gaseous BOG is additionally supplied, it is possible to increase the efficiency by ensuring operation above a certain level.

As described above, the lubricating oil (L) used in the boil-off gas compressor (20b) of the high-pressure stage may be mixed with the boil-off gas, and the gas-liquid separator 50 is a lubricating oil ( L) can be prevented from being mixed, thereby preventing the deterioration of the quality of the liquefied gas stored in the liquefied gas storage tank (10).

In this regard, as shown in FIG. 3 , the gas-liquid separator 50 includes a housing 52 , a boil-off gas inlet 53 , a liquid boil-off gas outlet 54 , a weir 55 , a lubricating oil blocking plate. (56), and a lubricant drain line (57).

The housing 52 stores the boil-off gas decompressed by the pressure reducing valve 40 . The housing 52 may have a cylindrical shape as shown in the drawings, but the shape of the housing 52 is not particularly limited.

However, since the housing 52 must prevent the boil-off gas from being vaporized while storing the boil-off gas of low pressure/low temperature liquefied by decompression, an insulating facility for blocking heat penetration from the outside may be provided.

It can be seen that the housing 52 is provided on the boil-off gas return line 31 , and the boil-off gas return line 31 is located between the boil-off gas inlet 53 and the liquid boil-off gas outlet 54 to be described below. It may be connected through the inner space of the housing 52 .

The boil-off gas inlet 53 introduces the boil-off gas into the housing 52 . The boil-off gas inlet 53 is provided at one end of the boil-off gas return line 31 connected from the pressure reducing valve 40 to the gas-liquid separator 50, and may be a half open inlet with an open lower side. . This is to prevent scattering of the boil-off gas when the low-pressure/low-temperature boil-off gas flows into the housing 52 .

The boil-off gas inlet 53 may be provided above the liquid level of the boil-off gas stored in the housing 52 , but may be provided lower than the upper end of the weir 55 . Accordingly, the BOG introduced through the BOG inlet 53 may be mixed with the BOG stored in the housing 52 .

The liquid boil-off gas discharge unit 54 discharges the liquid boil-off gas (G) inside the housing 52 . The liquid boil-off gas discharge unit 54 may be provided at one end of the boil-off gas return line 31 connected from the gas-liquid separator 50 to the liquefied gas storage tank 10 .

The liquid BOG discharge unit 54 may be provided below the minimum level of BOG stored in the housing 52 , and may be provided above the lubricant blocking plate 56 .

Among the BOGs introduced into the housing 52 through the BOG inlet 53 , BOG above a certain level is passed over the weir 55 , and the liquid BOG discharge part 54 is of the weir 55 . It is possible to discharge the liquid boil-off gas (G) passed to the upper side to the boil-off gas return line (31). To this end, the liquid BOG discharge part 54 and the BOG inlet part 53 are provided opposite to each other with respect to the weir 55 .

In addition, a lubricant blocking plate 56 is provided on the lower side of the weir 55 in a horizontal direction, and between the lower side of the weir 55 and the lower surface of the housing 52 may be opened. After passing from the gas inlet 53 to the lower side of the weir 55 , the liquid boil-off gas (G) passing upward through the lubricating oil blocking plate 56 may be discharged to the boil-off gas return line 31 .

That is, the liquid BOG discharge unit 54 discharges the liquid BOG passing through the weir 55 without passing through the lubricating oil blocking plate 56 or liquid BOG passing through the lubricating oil blocking plate 56 . (G) can be emitted.

In the low pressure/low temperature BOG that is decompressed by the pressure reducing valve 40 and introduced into the housing 52, the lubricating oil (L) is in a liquid or solid state and has a considerably higher density than the BOG, so that the lubricant (L) is absorbed into the BOG Even if mixed and introduced into the housing 52 through the boil-off gas inlet 53 , the lubricant L does not pass over the upper side of the weir 55 and sinks downward, even if it crosses the lower side of the weir 55 . It is blocked by the lubricating oil blocking plate (56).

Accordingly, the lubricating oil L may be removed from the BOG discharged to the liquid BOG discharge unit 54 , unlike the BOG introduced into the BOG inlet 53 .

The weir 55 is provided between the boil-off gas inlet 53 and the liquid boil-off gas outlet 54 . The weir 55 is provided in the vertical direction within the housing 52 and may have a shape to allow the boil-off gas to pass through the upper side. However, as the weir 55 has a sufficient height, the lubricating oil ( L) cannot go over the upper side of the weir (55).

The lubricating oil blocking plate 56 is provided to filter the lubricating oil (L) between the inflow of the boil-off gas and the discharge of the liquid boil-off gas (G). It is provided in the horizontal direction to suppress the lubricating oil (L) inflow into the liquid boil-off gas discharge unit 54 .

The lubricating oil blocking plate 56 may have a hole smaller than the lubricating oil (L) particles and thus may be in the form of a perforated plate that inhibits the passage of the lubricating oil (L) and allows the passage of the liquid boil-off gas (G), but only the lubricating oil blocking plate (56) ), the liquid boil-off gas discharge unit 54 provided above the lubricating oil blocking plate 56 may be provided at a position spaced upward.

This is to prevent a portion of the lubricating oil L from escaping through the liquid BOG discharge unit 54 while floating when the vessel 1 in which the gas-liquid separator 50 is provided is tilted by an external force or the like.

The lubricating oil drain line 57 discharges the lubricating oil L collected at the bottom of the housing 52 to the outside. Between the lower side of the weir 55 and the bottom of the housing 52 may have an open shape (baffles (not shown) provided in a grid may be provided), the lubricant (L) mixed in the boil-off gas are naturally gathered on the bottom of the housing 52 by gravity.

However, the lubricating oil drain line 57 can be kept closed by a drain valve (not shown), and when maintenance is required, the lubricating oil (L) is discharged to the outside to check the efficiency of removing the lubricating oil (L). can

The lubricating oil drain line 57 may be connected to the boil-off gas return line 31, and when the filter efficiency is verified in the boil-off gas compressor 20b of the high-pressure stage, or the separator 22 or the coalescer 23, the lubricant ( When L) is sufficiently filtered, the lubricating oil drain line 57 may be opened toward the boil-off gas return line 31 .

The lubricating oil processing unit 60 pushes the lubricating oil L flowing into the boil-off gas heat exchanger 30 by injecting high-temperature gas to the downstream of the boil-off gas heat exchanger 30 to process it. The lubricating oil L used in the boil-off gas compressor 20b of the high-pressure stage can be mixed with the boil-off gas and introduced into the boil-off gas heat exchanger 30 as described above. In addition to removing the lubricating oil (L) using the structure, injection of a high-temperature gas may be used to remove the lubricating oil (L) stuck in the boil-off gas heat exchanger 30 .

The lubricating oil processing unit 60 may inject high-temperature gas, such as nitrogen gas at 40 degrees or higher, into the BOG heat exchanger 30 , for example, the high-temperature gas injected into the BOG heat exchanger 30 is the BOG heat exchanger 30 . ) can be discharged by heating the lubricating oil (L) flowing into it.

If a continuous BOG flow is made in the BOG heat exchanger 30, the possibility that the lubricating oil L will remain in the BOG heat exchanger 30 is not great. (L) A part may remain in the boil-off gas heat exchanger 30, and at this time, the lubricant (L) is further cooled by the low-temperature boil-off gas discharged from the liquefied gas storage tank 10 and solidifies, so that the boil-off gas heat exchanger 30 ) and may obstruct the flow of boil-off gas.

Therefore, in this embodiment, the lubricating oil (L) is forcibly applied while lowering the viscosity of the lubricating oil (L) by injecting high-temperature gas into the boil-off gas heat exchanger (30) using the lubricating oil processing unit (60) to heat the lubricating oil (L). By pushing, it is possible to prevent the flow in the boil-off gas heat exchanger 30 from being lowered.

The lubricating oil processing unit 60 injects high-temperature gas into the upstream of the boil-off gas heat exchanger 30 from the boil-off gas return line 31 , and the hot gas mixed with the lubricant L is decompressed in the boil-off gas return line 31 . It can be discharged from downstream of valve (40).

To this end, the lubricant processing unit 60 includes a high-temperature gas supply unit and a high-temperature gas discharge unit 62 . The hot gas supply unit is connected to the upstream of the boil-off gas heat exchanger 30 in the boil-off gas return line 31 to inject the hot gas.

The high-temperature gas may be injected while the boil-off gas does not flow in the boil-off gas return line 31 . When BOG flows in the BOG return line 31, the liquefaction efficiency of BOG is lowered when hot gas is injected, and at the same time, the lubricating oil (L) removal effect may be reduced, and BOG may be discharged when hot gas is discharged. am.

When the hot gas flows into the boil-off gas heat exchanger 30 through the boil-off gas return line 31 , the lubricating oil L remaining in the boil-off gas heat exchanger 30 may have a lower viscosity while being heated, and then the hot gas It may come out of the boil-off gas heat exchanger (30) together with.

The high-temperature gas injection unit 61 supplies an inert gas (eg, nitrogen gas, etc.) first before injecting the high-temperature gas (eg, nitrogen gas of 40 degrees or more) to push the boil-off gas inside the boil-off gas heat exchanger 30 . can pay The reason for pushing the boil-off gas is to prevent the explosive boil-off gas from mixing with the high-temperature gas discharged together with the lubricating oil (L) in the future.

The hot gas discharge unit 62 is branched from the upstream and/or downstream of the pressure reducing valve 40 in the boil-off gas return line 31 to discharge the hot gas mixed with the lubricating oil (L). At this time, the lubricating oil L discharged to the outside through the high-temperature gas may be recycled, and the high-temperature gas may also be recycled and injected into the boil-off gas heat exchanger 30 through the high-temperature gas injection unit 61 .

For example, the lubricating oil processing unit 60 filters the lubricating oil (L) from the high-temperature gas + the lubricating oil (L) discharged from the high-temperature gas discharging unit 62, reheats the high-temperature gas, and then reheats the boil-off gas heat exchanger (30). Inflow method can be used.

In addition, the lubricating oil processing unit 60 heats nitrogen gas generated from an inert gas generator (IG Generator) or a nitrogen generator that is commonly provided in the ship 1 and uses it as a high-temperature gas, so that a separate high-temperature gas may not be generated. there is.

Lubricating oil filters 70a, 70b, and 70c filter out the lubricating oil L. The lubricant filter 70a may be provided between the pressure reducing valve 40 and the gas-liquid separator 50 in the boil-off gas return line 31 . For example, the lubricating oil filter 70a may be provided between the high-temperature gas discharge unit 62 and the gas-liquid separator 50 in the boil-off gas return line 31, and the lubricating oil that has not been discharged from the high-temperature gas discharge unit 62 ( L) can be prevented from flowing into the liquefied gas storage tank 10 or from flowing into the boil-off gas heat exchanger 30 through the gaseous boil-off gas delivery line 51 .

The lubricant filter 70a described above may be a liquid filter, and may be provided to remove the liquid lubricant L.

In addition, the lubricant filter 70b may be provided upstream of the boil-off gas heat exchanger 30 in the boil-off gas return line 31 . In this case, the lubricating oil filter 70b may be a gaseous filter, and may remove the lubricating oil L, which may be in a supercritical state by being heated to a high pressure.

The lubricating oil filter 70b provided upstream of the boil-off gas heat exchanger 30 in the boil-off gas return line 31 may be an adsorption tower capable of adsorbing the lubricant L, or between boil-off gas and lubricating oil L. It may be a cyclone separator that separates up and down using a density difference. That is, in the present invention, the lubricating oil filters 70a, 70b, and 70c are not limited to a general filter type, but may be a term encompassing all types capable of filtering the lubricating oil L from the boil-off gas.

The lubricant filter 70c may be provided between the BOG heat exchanger 30 and the auxiliary BOG heat exchanger 32 in the BOG return line 31, and in this case, the lubricant filter 70c may be a liquid filter. .

Alternatively, the lubricant filter 70c may be a liquid-phase separator provided between the boil-off gas heat exchanger 30 and the auxiliary boil-off gas heat exchanger 32 in the boil-off gas return line 31 . The liquid phase separator is a configuration that separates boil-off gas and lubricating oil (L) by a difference in density. Similar to the gas-liquid separator 50 described above, it has a space for accommodating boil-off gas and has a partition wall (not shown) inside to separate the lubricating oil ( L) can be separated.

It goes without saying that the various types of lubricant filters 70a, 70b, and 70c described above may be selectively provided or may be provided in combination. For example, in the BOG return line 31, a gaseous filter is provided upstream of the BOG heat exchanger 30, and a liquid filter is provided between the BOG heat exchanger 30 and the auxiliary BOG heat exchanger 32, lubricating oil ( L) can be filtered in two steps.

As such, in this embodiment, the gas-liquid separator 50 has a structure to filter the lubricant (L), and when the lubricant (L) is interposed in the boil-off gas heat exchanger (30), high-temperature gas is forcibly injected to the lubricant ( L) can be removed, and even if the lubricating oil L is mixed with the boil-off gas in the boil-off gas compressor 20b of the high-pressure stage, it is possible to prevent the deterioration of the storage quality of the liquefied gas storage tank 10 .

4 is a cross-sectional view of the gas-liquid separator in the boil-off gas reliquefaction system according to the second embodiment of the present invention.

Referring to FIG. 4 , the BOG reliquefaction system 2 according to the second embodiment of the present invention has a difference in the structure of the gas-liquid separator 50 as compared with the first embodiment. Hereinafter, the present embodiment will be mainly described on the points that are different from the first embodiment, and the parts omitted from the description will be replaced with the previous content. This is also the case in other embodiments below.

In this embodiment, the gas-liquid separator 50 replaces the weir 55 and the lubricating oil blocking plate 56 in the housing 52, the inlet side partition wall 531, the discharge side inclined wall 541a, 541b, and the baffle ( 58) may be included.

The inlet-side bulkhead 531 serves to collect the boil-off gas flowing in through the boil-off gas inlet 53 downward without scattering, and may be omitted when using the aforementioned half-open inlet.

The discharge-side inclined walls 541a and 541b are provided in two or more and form a v or y shape and may be provided so that the middle is opened for the passage of boil-off gas. The discharge side inclined walls 541a and 541b obstruct the flow of BOG when it exits to the BOG return line 31 through the liquid BOG discharge part 54, so that the lubricant L is transferred to the liquid BOG discharge part ( 54) and may fall to the bottom of the housing 52.

The baffle 58 is provided below the boil-off gas inlet 53 , and may allow the lubricant L to be filtered from the boil-off gas that collides with the inlet-side partition 531 and falls toward the bottom of the housing 52 . In this case, the baffle 58 may be a straightener.

5 is a cross-sectional view of the gas-liquid separator in the boil-off gas reliquefaction system according to the third embodiment of the present invention.

Referring to FIG. 5 , in the third embodiment of the present invention, the gas-liquid separator 50 allows the boil-off gas inlet 53 to be disposed lower than the liquid level of the boil-off gas in the housing 52, unlike the first embodiment, and evaporates A lubricant blocking plate 56 may be provided above the gas inlet 53 .

Therefore, in the present embodiment, the BOG flowing into the housing 52 passes upward through the lubricant blocking plate 56 and the lubricant L can be filtered, and the BOG from which the lubricant L is removed is then transferred to the weir 55 ) and may be discharged to the outside of the housing 52 through the liquid boil-off gas discharge unit 54 .

In this embodiment, the lower side of the weir 55 is fixed to the bottom of the housing 52 so that the boil-off gas can be delivered to the liquid boil-off gas discharge unit 54 through the lubricant blocking plate 56 and the weir 55. The flow of boil-off gas to the lower side of (55) may not be allowed.

6 is a cross-sectional view of the gas-liquid separator in the boil-off gas reliquefaction system according to the fourth embodiment of the present invention.

Referring to FIG. 6 , the gas-liquid separator 50 according to the fourth embodiment of the present invention may include inflow-side inclined walls 532a and 532b and a lubricant blocking plate 56 .

The inlet side inclined walls 532a and 532b may allow the BOG introduced from the upper side of the housing 52 through the BOG inlet to be collected downward. The inlet inclined walls 532a and 532b may have a v or y shape to implement a funnel function, and the boil-off gas delivered to the bottom of the housing 52 on the inlet inclined walls 532a and 532b is in the vertical direction. It may be introduced into the liquid boil-off gas discharge unit 54 past the lubricating oil blocking plate 56 to be placed.

The lubricating oil blocking plate 56 may be provided in a vertical direction, unlike the first embodiment, and may be a perforated plate having a size through which the lubricating oil L included in the boil-off gas cannot pass.

Therefore, the BOG introduced by the BOG inlet 53 is flowed downward by the inlet inclined walls 532a and 532b, and then the housing 52 through the inlet inclined walls 532a and 532b. ) flows towards the bottom.

Since the lubricant (L) contained in the boil-off gas does not pass through the lubricant blocking plate 56, only the boil-off gas from which the lubricant (L) is separated is the boil-off gas return line 31 through the liquid boil-off gas discharge unit 54 . can be emitted as

7 is a conceptual diagram of a BOG reliquefaction system according to a fifth embodiment of the present invention.

Referring to FIG. 7 , the BOG reliquefaction system 2 according to the fifth embodiment of the present invention further includes a BOG bypass line 33 and a vapor BOG bypass line 512 compared to the previous embodiment. For reference, a valve marked in black in FIG. 7 indicates a closed state.

The BOG bypass line 33 allows BOG discharged from the liquefied gas storage tank 10 to bypass the BOG heat exchanger 30 and be delivered to the BOG compressor 20 . The boil-off gas bypass line 33 may be provided with a boil-off gas bypass valve 331 for controlling the flow of the boil-off gas bypass line 33 .

In this embodiment, unlike the first embodiment, instead of injecting a separate high-temperature gas, the lubricating oil ( L) can be heated and removed.

However, when the low-temperature boil-off gas discharged from the liquefied gas storage tank 10 also flows into the boil-off gas heat exchanger 30 when the high-temperature boil-off gas flows into the boil-off gas heat exchanger 30, the lubricating oil ( L) may not be properly heated/removed.

Therefore, in this embodiment, the boil-off gas bypass line 33 is provided so that the low-temperature boil-off gas discharged from the liquefied gas storage tank 10 is supplied to the boil-off gas compressor 20 without flowing into the boil-off gas heat exchanger 30 . can Through this, the high-temperature boil-off gas introduced into the boil-off gas heat exchanger 30 can be removed by effectively heating the lubricating oil (L).

The vapor-phase boil-off gas bypass line 512 allows the vapor-phase boil-off gas discharged from the gas-liquid separator 50 to bypass the boil-off gas heat exchanger 30 and be delivered to the boil-off gas compressor 20 . The vapor boil-off gas bypass line 512 is provided with a vapor-phase boil-off gas bypass valve 513 for controlling the flow of the vapor-phase boil-off gas bypass line 512 .

The reason why the vapor phase BOG bypasses the BOG heat exchanger 30 is to achieve the same purpose as allowing the low-temperature BOG described above to bypass the BOG heat exchanger 30 . Through this, the high-temperature BOG discharged from the BOG compressor 20 is not cooled by the low-temperature BOG or the gaseous BOG in the BOG heat exchanger 30, so that the lubricating oil L can be sufficiently heated.

That is, in this embodiment, the high-pressure BOG return valve 311 is opened to deliver the high-temperature BOG heated in the BOG compressor 20 to the BOG heat exchanger 30, and at this time, the BOG supply valve 211a is closed and By opening the BOG bypass valve 331, it is possible to prevent the low-temperature BOG discharged from the liquefied gas storage tank 10 from cooling the high-temperature BOG.

In addition, the gaseous BOG delivery valve 511 is closed and the gaseous BOG bypass valve 513 is opened, so that the gaseous BOG discharged from the gas-liquid separator 50 does not flow into the BOG heat exchanger 30 and the gaseous BOG bypass line By bypassing the boil-off gas heat exchanger 30 along (512), it is possible to prevent the vapor phase boil-off gas from cooling the high-temperature boil-off gas.

Therefore, in the present embodiment, it is possible to effectively remove the lubricating oil L stuck in the boil-off gas heat exchanger 30 using high-temperature boil-off gas.

8 is a conceptual diagram of a BOG reliquefaction system according to a sixth embodiment of the present invention.

Referring to FIG. 8 , the BOG reliquefaction system 2 according to the sixth embodiment of the present invention may further include a high-temperature BOG supply line 514 compared to the fifth exemplary embodiment, and bypass the vapor phase BOG. Line 512 may be omitted. For reference, a valve marked in black in FIG. 8 indicates a closed state.

The high-temperature BOG supply line 514 in this embodiment transfers the high-temperature BOG compressed in the BOG compressor 20 to the BOG heat exchanger 30 in order to remove the lubricating oil L introduced into the BOG heat exchanger 30. ), the high-temperature BOG discharged from the BOG heat exchanger 30 may be delivered to the consumer 3 .

The high-temperature boil-off gas supply line 514 may be branched from the upstream of the pressure reducing valve 40 in the boil-off gas return line 31 and may be connected to the upstream of the consumer 3 from the boil-off gas supply line 21 . That is, in this embodiment, unlike the previous embodiment, the high-temperature boil-off gas may be withdrawn from the boil-off gas return line 31 in a high pressure state.

The high-temperature BOG mixed with the lubricant (L) while heating the lubricant (L) and pushing it out of the BOG heat exchanger (30) may be delivered to the consumer (3) and consumed. Therefore, in this embodiment, the lubricant (L) removed from the boil-off gas heat exchanger (30) is not recirculated, so that the lubricant (L) is prevented from flowing into the liquefied gas storage tank (10).

In this embodiment, the high-pressure boil-off gas return valve 311 may be provided between the point where the boil-off gas return line 31 is branched from the boil-off gas supply line 21 and the point where the high-temperature boil-off gas supply line 514 is connected. However, when the high-pressure BOG return valve 311 is closed, the high-temperature BOG compressed in the BOG compressor 20 is introduced into the BOG heat exchanger 30 along the BOG return line 31 .

However, the low-temperature BOG discharged from the liquefied gas storage tank 10 flows along the BOG bypass line 33 as the BOG supply valve 211a is closed and the BOG bypass valve 331 is opened. do not cool

In addition, the high-temperature boil-off gas from which the lubricating oil (L) has been removed from the boil-off gas heat exchanger 30 flows along the high-temperature boil-off gas supply line 514 as the pressure reducing valve 40 is closed, and through the boil-off gas supply line 21 . It is delivered to the consumer (3).

In this case, since the high-temperature boil-off gas does not flow into the gas-liquid separator 50 , vapor-phase boil-off gas may not be generated, and the vapor-phase boil-off gas delivery valve 511 may be closed. Therefore, the high-temperature boil-off gas introduced into the boil-off gas heat exchanger 30 can sufficiently heat the lubricating oil (L).

9 is a conceptual diagram of a BOG reliquefaction system according to a seventh embodiment of the present invention.

Referring to FIG. 9 , the BOG reliquefaction system 2 according to the seventh embodiment of the present invention uses the high-pressure/high-temperature BOG compressed in the BOG compressor 20b of the high-pressure stage in the fifth and sixth embodiments. Unlike the utilization, the low pressure/high temperature BOG compressed in the BOG compressor 20a of the low pressure stage may be utilized.

To this end, in this embodiment, instead of the gaseous boil-off gas bypass line 512 of the fifth embodiment or the high-temperature boil-off gas supply line 514 of the sixth embodiment, from the low-pressure boil-off gas supply line 212 as a side stream. A low-pressure boil-off gas return line 214 that branches and delivers high-temperature boil-off gas (about 43 degrees to about 40 degrees) to the boil-off gas heat exchanger 30 may be provided, and the low pressure boil-off gas return line 214 has low pressure evaporation A low pressure boil-off gas return valve 215 for controlling the flow of the gas return line 214 is provided.

The low-pressure BOG return line 214 transfers the high-temperature BOG compressed in the BOG compressor 20a of the low pressure stage to the BOG heat exchanger 30 to remove the lubricating oil L introduced into the BOG heat exchanger 30. ) can be injected.

The low-pressure boil-off gas return line 214 is branched from the low-pressure boil-off gas supply line 212 and is connected to the upstream of the boil-off gas heat exchanger 30 from the boil-off gas return line 31 . Therefore, in order to remove the lubricating oil L of the boil-off gas heat exchanger 30 , in this embodiment, the high-pressure boil-off gas return valve 311 provided in the boil-off gas return line 31 is closed, and the low pressure boil-off gas return valve 215 is closed. ) can be opened to deliver the high-temperature BOG compressed in the BOG compressor 20a of the low pressure stage to the BOG heat exchanger 30 .

At this time, the high-temperature boil-off gas flowing into the boil-off gas heat exchanger 30 is not cooled due to the low-temperature boil-off gas discharged from the liquefied gas storage tank 10 as described above in another embodiment.

In addition, this embodiment may be provided so that the high-temperature boil-off gas does not exchange heat with the vapor-phase boil-off gas discharged from the gas-liquid separator 50. To this end, the present embodiment may further include a high-temperature boil-off gas delivery line 515 and The boil-off gas delivery line 515 may include a high-temperature boil-off gas delivery valve 516 .

The high-temperature boil-off gas delivery line 515 may be connected from the gas-liquid separator 50 to the low-pressure consumer 3 . For example, the high-temperature boil-off gas delivery line 515 is a boil-off gas heat exchanger 30 from the gas-liquid separator 50 . Alternatively, it may be branched from the vapor phase boil-off gas delivery line 51 connected to the boil-off gas compressor 20 and connected to the low-pressure consumer 3 or the low-pressure boil-off gas supply line 212 .

The high-temperature BOG compressed in the low-pressure BOG compressor 20a is transferred to the BOG return line 31 as the low-pressure BOG return valve 215 is opened and introduced into the BOG heat exchanger 30 . At this time, the low pressure BOG supply valve 213 provided in the low pressure BOG supply line 212 may be sealed.

The low pressure/high temperature BOG introduced into the BOG heat exchanger 30 can be pushed out by heating the lubricating oil L stuck in the BOG heat exchanger 30, and then the high-temperature BOG is passed through the pressure reducing valve 40. It is transferred to the gas-liquid separator 50 . However, since the high-temperature boil-off gas used to remove the lubricating oil (L) is a low pressure, even if the pressure is reduced by the pressure reducing valve 40, the temperature drop does not occur significantly (for example, if the pressure is reduced from 10 bar to 7 bar, the temperature will drop from 43 degrees to 42 degrees. can).

After that, the high-temperature BOG in a gaseous state introduced into the gas-liquid separator 50 is sealed with a gaseous BOG delivery valve 511 provided in the gaseous BOG delivery line 51 and provided in the high-temperature BOG delivery line 515. As the high-temperature BOG delivery valve 516 is opened, it may be supplied to the DFDE low-pressure engine 3b and/or the gas combustion device 3c, which is the low-pressure demander 3, along the high-temperature BOG delivery line 515. .

To this end, the high-temperature BOG delivery line 515 is connected to the downstream of the low-pressure BOG supply valve 213 provided in the low-pressure BOG supply line 212 , and when the low-pressure BOG supply valve 213 is closed, the high-temperature BOG is to be supplied to the low-pressure demand (3).

As described above, in this embodiment, the high-temperature boil-off gas (lubricating oil (L) is not mixed) compressed in the boil-off gas compressor (20a) of the low pressure stage is utilized to remove the lubricant oil (L) of the boil-off gas heat exchanger (30) while lubricating oil ( By allowing the high-temperature BOG mixed with L) to be consumed at the low-pressure consumer 3 , the lubricant L remaining in the BOG heat exchanger 30 can be effectively removed.

10 is a conceptual diagram of a BOG reliquefaction system according to an eighth embodiment of the present invention.

Referring to FIG. 10 , the BOG reliquefaction system 2 according to the eighth embodiment of the present invention is low-pressure/high-temperature BOG compressed by the BOG compressor 20a of the low-pressure stage in comparison with the seventh exemplary embodiment. Instead of using , the high-pressure/high-temperature BOG compressed in the BOG compressor 20b of the high-pressure stage may be used to remove the lubricating oil L.

In this case, the present embodiment may omit the low-pressure BOG return line 214 , and when the high-pressure BOG return valve 311 is opened, the high-pressure/high-temperature BOG flows along the BOG return line 31 to the BOG heat exchanger. (30) can be introduced.

Afterwards, the high-temperature BOG discharged from the BOG heat exchanger 30 may be reduced and cooled while passing through the pressure reducing valve 40. For example, when the pressure is reduced from 300bar to 7bar, the high-temperature BOG of 43°C is reduced to around -37°C. can be cooled.

The high-temperature boil-off gas passing through the pressure reducing valve 40 flows into the gas-liquid separator 50 . At this time, the gaseous BOG among the high-temperature BOG goes to the low-pressure consumer 3 along the high-temperature BOG delivery line 515 when the gaseous BOG delivery valve 511 is closed and the high-temperature BOG delivery valve 516 is open. can be supplied.

However, unlike the previous embodiment, in this embodiment, since the high-temperature boil-off gas used for removing the lubricating oil L is high pressure, the temperature drop occurs greatly when the pressure is reduced by the pressure reducing valve 40 .

Therefore, the high-temperature BOG delivered to the low-pressure demander 3 may not meet the required temperature of the low-pressure demander 3, and in this embodiment, a gas heater 517 may be provided in the high-temperature BOG delivery line 515. there is.

The gas heater 517 can heat the boil-off gas that is compressed in the boil-off gas compressor 20b of the high-pressure stage and passed through the boil-off gas heat exchanger 30 and the pressure reducing valve 40 to deliver it to the low-pressure consumer 3 , for example. The gas heater 517 may heat the high-temperature BOG cooled to about -37 degrees to about 40 degrees while passing through the pressure reducing valve 40 . Of course, the heat source used by the gas heater 517 is not particularly limited.

As described above, in this embodiment, the lubricating oil L stuck in the boil-off gas heat exchanger 30 is heated using high-pressure/high-temperature boil-off gas and then it can be effectively removed by strongly pushing it, and the high temperature in which the lubricant L is mixed. By consuming the boil-off gas at the low-pressure demand (3), it is possible to block the inflow of the lubricant (L) into the liquefied gas storage tank (10).

11 and 12 are conceptual views of a BOG reliquefaction system according to a ninth embodiment of the present invention.

11 and 12 , the BOG reliquefaction system 2 according to the ninth embodiment of the present invention includes a low-pressure stage ( For example, the high-temperature and high-speed BOG compressed in the BOG compressor 20 of the second stage) may be used.

To this end, the present embodiment includes a low-pressure BOG return line 214 . The low-pressure BOG return line 214 may be branched from the low-pressure BOG supply line 212 to inject high-temperature BOG into the BOG heat exchanger 30 .

In addition, in this embodiment, the BOG injected from the BOG compressor 20a of the low-pressure stage can be supplied to the low-pressure engine 3b to remove the lubricant L introduced into the BOG heat exchanger 30, and this A high-temperature boil-off gas delivery line 515 is provided for this purpose.

The high-temperature BOG delivery line 515 is branched from the upstream of the pressure reducing valve 40 in the BOG return line 31 and is connected to the low-pressure engine 3b, so that the high-temperature evaporation discharged from the BOG heat exchanger 30 is The gas may be delivered to the low pressure engine 3b upstream of the pressure reducing valve 40 .

At this time, the high-temperature BOG delivery line 515 may be connected downstream of the low-pressure BOG supply valve 213 in the low-pressure BOG supply line 212. In this embodiment, the lubricating oil ( L), when injecting the high-temperature BOG compressed in the BOG compressor 20a of the low pressure stage into the BOG heat exchanger 30 through the low-pressure BOG return line 214, the low-pressure BOG supply line The low-pressure boil-off gas supply valve 213 provided in the 212 may be sealed.

That is, when implementing the removal of the lubricating oil L of the BOG heat exchanger 30 , the high-temperature and high-speed BOG discharged from the BOG compressor 20a at the low pressure stage is a low-pressure BOG branched from the low-pressure BOG supply line 212 . After flowing into the boil-off gas heat exchanger 30 along the return line 214 , it is joined into the low-pressure boil-off gas supply line 212 along the high-temperature boil-off gas delivery line 515 downstream of the boil-off gas heat exchanger 30 . It may be supplied to the low pressure engine 3b.

Therefore, in this embodiment, by using the gas used to remove the lubricating oil (L) in the power generation engine, the efficiency improvement effect can be obtained in terms of system operation and cost. Hereinafter, the cleaning process will be described in more detail.

In the case of the cleaning process, the pressure reducing valve 40 is closed while the BOG compressor 20 operates and the low pressure engine 3b operates in the gas mode. However, at this time, the flow from the boil-off gas compressor 20 to the boil-off gas heat exchanger 30 may reverse flow and adversely affect the lubricant filter 70b to be described later, so between the lubricant oil filter 70b and the boil-off gas heat exchanger 30 . The sealing of a manual valve (not shown) provided in the .

Thereafter, the low-pressure BOG discharged from the liquefied gas storage tank 10 through the opening of the BOG bypass valve 331 and the sealing of the BOG supply valve 211a is provided to bypass the BOG heat exchanger 30 .

In addition, the low pressure BOG return valve 215 provided in the low pressure BOG return line 214 is opened, and a plurality of low pressure BOG return valves 215 may be provided, any one of which is an On/Off type block valve, The other may be a control valve capable of regulating the opening degree.

At this time, the low-pressure BOG return valve 215 with an adjustable opening degree is opened at a low opening degree (for example, 10%), and when the pressure of the high-temperature BOG delivery line 515 reaches a certain pressure (for example, 10 barg), the opening degree may be expanded to 100%, and with this, the high-temperature boil-off gas delivery valve 516 of the high-temperature boil-off gas delivery line 515 may be opened.

In the cleaning process, the low pressure BOG supply valve 213 provided in the low pressure BOG supply line 212 may be closed. However, the flow rate of the high-temperature boil-off gas flowing into the boil-off gas heat exchanger 30 is changed by adjusting the opening degree of the low-pressure boil-off gas supply valve 213, and the temperature of the boil-off gas flowing into the low-pressure engine 3b may vary. .

Therefore, in this embodiment, while the BOG temperature at the front end of the low-pressure engine 3b is suitable for the required temperature (for example, 20 degrees C) of the low-pressure engine 3b, the degree of opening of the low-pressure BOG supply valve 213 is automatically controlled. can do.

The cleaning process may be performed by maintaining the above state for a predetermined time (eg, about 1 hour). However, in the cleaning process, the load of the low-pressure engine 3b may be maintained at a low load (15 to 50%) in order to prevent abnormal combustion due to the inflow of the lubricant L. This is in consideration of the possibility that the lubricant (L) of about 97 g calculated below may be introduced into the low pressure engine 3b during the laden voyage.

The cleaning process may be performed according to the selection of the shipowner, but it is preferable that the cleaning process be performed for each ballast voyage, regardless of how contaminated the boil-off gas heat exchanger 30 is by the lubricating oil (L).

In addition, in this embodiment, a lubricant filter 70a may be provided between the pressure reducing valve 40 and the gas-liquid separator 50, and in this case, the lubricant oil filter 70a may be a solid filter. The lubricating oil filter 70a filters the lubricating oil L delivered in a vapor state, thereby preventing contamination of the boil-off gas flowing into the liquefied gas storage tank 10 .

And/or in this embodiment, by placing the lubricant filter 70b in the downstream of the high-pressure boil-off gas return valve 311 in the boil-off gas return line 31, the lubricant oil L is filtered and the liquefied gas storage tank 10 It can guarantee the quality of the liquefied gas stored in the

In the present embodiment, a separator 22 and a coalescer 23 for filtering foreign substances such as lubricant L from the downstream of the boil-off gas compressor 20 may be provided, and in this case, the separator 22 is a cyclone. can be In this embodiment, the separator 22 , the coalescer 23 , the lubricant filter 70b and the like may be collectively referred to as a filter system (BCA).

Therefore, in this embodiment, the lubricating oil (L) that can be mixed in the BOG compressor 20 of the 4th and 5th stages can be filtered by two filtration systems. The first is a filter system, and the second is a lubricant filter 70a between the pressure reducing valve 40 and the gas-liquid separator 50 .

At this time, for example, the separator 22 is 4 to 10 ppmw, the coalescer 23 is 0.1 ppmw (liquid)/2 to 4 ppmw (vapor), the lubricant filter 70b is 0.1 ppmw, and the lubricant filter 70a is 0.1 μm filtering. performance can be provided.

Assuming such filtering performance, assuming that the vessel sails at a ship speed of 15 knots in a laden voyage (20days+margin(anchoring, etc.)), the flow rate of BOG flowing into the BOG reliquefaction system (2) is 1,761kg/ It may be h (15 knots, 20 days), 2,785 kg/h (anchoring, 2 days), and the amount of lubricating oil (L) filtered by the lubricating oil filter 70b in the laden voyage may be about 97 g.

That is, the present embodiment can suppress the return of the lubricant (L) to the liquefied gas storage tank 10 through two filtration systems. However, such a filtration system alone cannot be considered that the lubricant (L) is completely removed, and the deterioration of heat exchange performance in the boil-off gas heat exchanger (30) cannot be prevented due to the lubricant (L).

Therefore, in the present embodiment, the deterioration of the heat exchange performance of the boil-off gas heat exchanger 30 due to contamination of the lubricant L can be solved by a cleaning system (warm gas cleaning/blowing system) using high-pressure boil-off gas.

However, the cleaning system has the purpose of securing the heat exchange efficiency of the boil-off gas heat exchanger 30, and cannot completely guarantee the removal of the lubricant (L) from the boil-off gas heat exchanger 30. This embodiment is a filtration system By providing a warm gas cleaning/blowing system together, it is possible to completely prevent problems caused by the lubricating oil (L) used in the boil-off gas compressor (20b) of the high pressure stage.

Specifically, the warm gas cleaning/blowing system heats the boil-off gas heat exchanger 30 using the boil-off gas discharged from the boil-off gas compressor 20a at the low pressure stage where the lubricant (L) does not mix, and the boil-off gas heat exchanger ( After melting the lubricating oil (L) remaining in 30), the lubricating oil (L) is supplied to the low-pressure engine 3b together with the boil-off gas.

In this case, in this embodiment, since the high-temperature boil-off gas containing the lubricating oil (L) is not delivered to the pressure reducing valve 40 or the gas-liquid separator 50, the gas-liquid separator 50 and other components are contaminated by the lubricating oil (L). No problem.

Also, during the cleaning process, there is no risk of agglomeration of the liquid lubricating oil L in the gas-liquid separator 50 , and the risk of the agglomerated lubricating oil L flowing into the liquefied gas storage tank 10 can also be completely eliminated.

13 is a conceptual diagram of a BOG reliquefaction system according to the present invention.

Hereinafter, with reference to FIG. 13 , a gas flow appearing according to the state (cool-down, start-up, interruption, trip) of the boil-off gas reliquefaction system 2 according to various embodiments of the present invention described above will be described.

First, in the case of cool down, the boil-off gas compressor 20 is operated using the low-temperature boil-off gas discharged from the liquefied gas storage tank 10 through a vapor header, and the boil-off gas is evaporated. It flows to the gas supply line 21 and the low pressure boil-off gas supply line 212 . At this time, the boil-off gas supply valve 211a may be opened and the boil-off gas bypass valve 331 may be in a closed state.

Thereafter, the pressure reducing valve 40 and the liquid boil-off gas return valve 312 are closed, and the high-pressure boil-off gas return valve 311 is opened at a constant opening degree (about 10%, 5% opening per minute), which passes through the boil-off gas compressor 20 . The low-temperature BOG is introduced into the BOG return line 31 for a certain period of time (about 5 minutes or so) to implement cooling.

Thereafter, after the high-pressure BOG return valve 311 is completely opened to 100%, the pressure reducing valve 40 is opened at a constant opening degree (about 10%, 5% opening per minute), and the set point of the gaseous BOG delivery valve 511 is may be set to around 5 barg. At this time, the gas-liquid separator 50 and the boil-off gas heat exchanger 30 may be cooled through the vapor phase BOG delivery line 51 .

After that, when the level in the gas-liquid separator 50 reaches a certain level (for example, 30%), the liquid boil-off gas return valve 312 is opened to a certain opening degree (about 20%) so that the boil-off gas is discharged into the boil-off gas return line 31 ) while returning to the liquefied gas storage tank 10 along the BOG return line 31 may be cooled.

By such a cool-down, in the present invention, the downstream of the pressure reducing valve 40 in the BOG return line 31, the gaseous BOG delivery line 51, etc. can be cooled to prevent unnecessary vaporization of the gas.

In the case of start-up, it is performed after checking that the cool-down has been completed, and at this time, the pressure reducing valve 40 is switched to a pressure control mode (PIC: Pressure control mode) or a flow control mode (FIC: Flow control mode). can work

Specifically, the pressure reducing valve 40 may operate in a pressure control mode while matching the pressure of the gas supplied to the high-pressure engine 3a to the required pressure of the high-pressure engine 3a when the high-pressure engine 3a operates. . Alternatively, the pressure reducing valve 40 may be operated in the flow rate control mode while checking the flow rate of boil-off gas and the like.

In the case of Stop, first close the pressure reducing valve 40 (reducing the opening to 30% per minute). In this case, the opening degree of the pressure reducing valve 40 may be decreased slowly, and the flow rate between the pressure reducing valve 40 and the gas-liquid separator 50 is reduced.

Thereafter, the high-pressure BOG return valve 311 is closed, thereby reducing the BOG flow rate from the BOG return line 31 to the gas-liquid separator 50 .

Thereafter, the pressure reducing valve 40 is fully opened to 100% to depressurize the boil-off gas between the high-pressure boil-off gas return valve 311 and the gas-liquid separator 50 .

Thereafter, the liquid boil-off gas return valve 312 is fully opened to 100%, and the condensed boil-off gas may be drained from the gas-liquid separator 50 to the liquefied gas storage tank 10 .

Afterwards, when the level in the gas-liquid separator 50 is sensed below a certain level (around 5%), the set point of the gaseous BOG delivery valve 511 is lowered to 1.5barg, and the BOG is depressurized to complete the shutdown process.

In the case of a trip, first, the high-pressure BOG return valve 311 is closed, and the BOG heat exchanger 30, the pressure reducing valve 40 and the gas-liquid separator 50 are directed through the BOG return line 31. The flow of boil-off gas is blocked.

Thereafter, by completely opening the pressure reducing valve 40, the liquid BOG return valve 312, and the gaseous BOG delivery valve 511 to 100%, the BOG return line 31 and the gaseous BOG delivery line 51 inside A trip process is performed by allowing all of the to be depressurized.

14 is a conceptual diagram of a BOG reliquefaction system having a BOG reliquefaction system according to the present invention, and FIG. 15 is a graph illustrating a gas processing state of the BOG reliquefaction system according to the present invention.

For reference, the present invention is not limited to the BOG reliquefaction system 2 described above, and in order to consume BOG or liquefied gas stored in the liquefied gas storage tank 10 as fuel, the BOG reliquefaction system ( In addition to 2), it may be a boil-off gas reliquefaction system further including other components.

14 , the BOG reliquefaction system having the BOG reliquefaction system 2 according to the present invention includes a BOG supply unit (HPC), a high pressure liquefied gas supply unit (HPP), a low pressure liquefied gas supply unit (LPP), It may include a boil-off gas liquefaction unit (ERS), of which the boil-off gas supply unit (HPC) and the boil-off gas liquefaction unit (ERS) may be referred to as the boil-off gas reliquefaction system 2 described above.

In this case, the boil-off gas supply unit (HPC) and the boil-off gas liquefaction unit (ERS) have already been described. Hereinafter, the high-pressure liquefied gas supply unit (HPP) and the low-pressure liquefied gas supply unit (LPP) will be described.

The high-pressure liquefied gas supply unit HPP supplies the liquefied gas discharged from the liquefied gas storage tank 10 to the high-pressure engine 3a through the high-pressure pump 82 and the high-pressure carburetor 83 .

In this case, the liquefied gas supply line 80 extending from the transfer pump (not shown) disposed in the liquefied gas storage tank 10 to the outside of the liquefied gas storage tank 10 is connected to the high-pressure engine 3a. It may be branched to the high-pressure liquefied gas supply line 81 for this purpose.

In the downstream of the high-pressure pump 82 or the high-pressure carburetor 83, (overpressure) liquefied gas is delivered to the liquefied gas storage tank 10 or a vent mast (not shown), etc. to prevent overpressure when supplying the liquefied gas. can

On the other hand, the low pressure liquefied gas supply unit (LPP), the liquefied gas discharged from the liquefied gas storage tank 10 through the forced vaporizer 85, the heavy carbon separator 86, the heater 87, the low pressure engine (3b) or gas combustion It is supplied to the device 3c or the like.

In this case, the forced vaporizer 85 and the like may be provided on the low pressure liquefied gas supply line 84 branched from the liquefied gas supply line 80 . That is, the liquefied gas supply line 80 is branched into a high-pressure liquefied gas supply line 81 and a low-pressure liquefied gas supply line 84 downstream of the transfer pump, and is connected to the high-pressure engine 3a and the low-pressure engine 3b, respectively.

As described above, the BOG reliquefaction system, which may further include a configuration for supplying liquefied gas in addition to the BOG reliquefaction system 2, can variously control whether BOG/liquefied gas is supplied according to the operating state of the vessel 1 . can be controlled This will be described with reference to FIGS. 14 and 15 together.

As an example, in the BOG reliquefaction system of the present invention, when the BOG is sufficiently loaded with liquefied gas (laden voyage), BOG is sufficiently generated so that BOG discharged from the liquefied gas storage tank 10 is the BOG header. After being compressed by the boil-off gas compressor 20, it can be supplied to and consumed by the high-pressure engine 3a or the low-pressure engine 3b.

15 is a graph showing gas consumption according to the speed of the ship, and it can be divided into four sections according to the speed of the ship. First, in the case of Section 1, which covers from anchored state to low-speed operation of less than 12 knots, it can be seen that the amount of boil-off gas in Laden Voyage exceeds the gas consumption by the high-pressure engine (3a) and the low-pressure engine (3b).

Also, in the case of Section 2, in which gas consumption by the high-pressure engine 3a, etc. gradually increases as the ship speed increases, the amount of boil-off gas in the Laden Voyage still exceeds the gas consumption of the high-pressure engine 3a and the like.

Therefore, the BOG reliquefaction system (2) of the present invention may preferably be operated in Section 1 and Section 2 when Laden Voyage to liquefy BOG.

However, in the case of Section 3 where the ship speed is high, the BOG reliquefaction system 2 may not be operated, and in the case of Section 4 where the ship speed is very high, the gas consumption of the high-pressure engine 3a, etc. Thus, the boil-off gas re-liquefaction system 2 can be supplied without operating the liquefied gas.

As described above, according to the present invention, in the BOG reliquefaction system further including a configuration for supplying liquefied gas to the BOG reliquefaction system 2, the reliquefaction of BOG and supply of liquefied gas are efficient in consideration of the ship speed. can be controlled with

16 is a conceptual diagram of a BOG reliquefaction system according to a tenth embodiment of the present invention.

Referring to FIG. 16 , in the BOG reliquefaction system 1 according to the tenth embodiment of the present invention, there is a change in the configuration of the lubricant processing unit 60 in the ninth embodiment described above with reference to FIG. 12 . Hereinafter, the present embodiment will be mainly described in terms of differences from the previous ninth embodiment.

In this embodiment, similarly to other embodiments, BOG generated in the liquefied gas storage tank 10 is compressed using a multi-stage BOG compressor 20, and the compressed BOG is compressed in the BOG heat exchanger 30 ), after cooling with boil-off gas before compression, using the pressure reducing valve 40 to decompress and liquefy, based on partial reliquefaction.

At this time, in this embodiment, the lubricating oil (L) is mixed in the boil-off gas during compression at the high-pressure stage of the boil-off gas compressor (20), and the mixed lubricant oil (L) is left in the boil-off gas heat exchanger (30) to solve the problem. A lubricating oil processing unit 60 is provided.

In particular, the lubricating oil processing unit 60 of this embodiment is the same as the ninth embodiment in that the high-temperature gas compressed in at least one stage of the boil-off gas compressor 20 is injected into the boil-off gas heat exchanger 30 , but the lubricant (L ) There is a difference in that the flow of hot gas for removal can be controlled in two ways.

Specifically, the lubricating oil processing unit 60 is configured such that the high-temperature gas compressed in the BOG compressor 20 is supplied to the consumer 3 via the BOG heat exchanger 30, or the high-temperature gas is supplied to the BOG heat exchanger 30. Of course, it can be supplied to the consumer 3 via the pressure reducing valve 40 and the lubricating oil filter 70a.

In the case of the ninth embodiment, the high-temperature gas for removing the lubricating oil (L) is branched from the second stage of the boil-off gas compressor (20), passes through the boil-off gas heat exchanger (30), and leaves before passing through the pressure reducing valve (40). It is supplied to the low-pressure engine (3b), which is the source (3).

However, in this case, as the lubricating oil L remains in the pressure reducing valve 40 , a clogging phenomenon may occur in the pressure reducing valve 40 , and there is a risk that the reliquefaction performance may be deteriorated.

In addition, as the lubricating oil (L) is accumulated on the outer wall of the filter element of the lubricating oil filter 70a provided between the pressure reducing valve 40 and the gas-liquid separator 50, the pressure at the rear end of the gas-liquid separator 50 is lowered and the reliquefaction performance is improved. and may increase maintenance costs.

In addition, as lubricating oil (L) is accumulated on the line from the rear end of the boil-off gas heat exchanger 30 to the lubricant filter 70a, a differential pressure is additionally generated, and the pressure at the rear end of the lubricant filter 70a is reduced to escape the design operation. Possibility exists.

Therefore, the present embodiment aims to solve the above problems by improving the ninth embodiment. That is, the lubricating oil processing unit 60 of the present embodiment may include a first lubricating oil processing line 63a and a second lubricating oil processing line 63b.

Here, the first lubricating oil treatment line 63a branches from the downstream of the boil-off gas compressor 20 in the low-pressure boil-off gas supply line 212 connected to the consumer 3 via at least one stage of the boil-off gas compressor 20 . It is a line that joins the low-pressure boil-off gas supply line 212 after passing through the boil-off gas heat exchanger 30 .

The first lubricating oil treatment line 63a may have a configuration that encompasses the low-pressure BOG return line 214 and the high-temperature BOG delivery line 515 described in the ninth embodiment and the like, and includes the BOG heat exchanger 30 . It may pass through and branch from the boil-off gas return line 31 upstream of the pressure reducing valve 40 and join the boil-off gas supply line 21 .

In addition, the second lubricating oil treatment line 63b is branched from the lubricating oil filter 70a provided between the pressure reducing valve 40 and the gas-liquid separator 50 on the boil-off gas return line 31 or the lubricating oil filter 70a evaporates downstream. It is a line branched from the gas return line 31 and joined to the boil-off gas supply line 21 .

The point at which the second lubricating oil treatment line 63b joins the boil-off gas supply line 21 may be downstream from the point where the first lubricant treatment line 63a joins the boil-off gas supply line 21, but limited thereto It is of course possible to join together at the same point.

The lubricating oil processing unit 60 includes lubricating oil processing valves 631 and 632 provided in the second lubricating oil processing line 63b. The lubricant treatment valves 631 and 632 are composed of one or more valves and may include an isolation valve 631 for adjusting the start/stop of the lubricant (L) treatment and a control valve 632 for varying the flow of hot gas. there is.

The lubricating oil treatment valves 631 and 632 apply pulsations to the high-temperature gas by adjusting the opening degree. That is, the lubricating oil treatment valves 631 and 632 periodically change the opening degree to give the cycle and amplitude to the flow of the hot gas.

Through this, in the present embodiment, the lubricating oil L of the boil-off gas heat exchanger 30 , the pressure reducing valve 40 , and the lubricating oil filter 70a can be more effectively removed by using the high-temperature gas to which the pulsation is applied.

That is, the lubricating oil processing unit 60 of this embodiment can intensively remove the lubricating oil L accumulated in the boil-off gas heat exchanger 30 by using the first lubricating oil processing line 63a similarly to the ninth embodiment. there is.

Alternatively, the lubricating oil processing unit 60 utilizes the upstream portion of the boil-off gas heat exchanger 30 in the first lubricating oil processing line 63a and the second lubricating oil processing line 63b, unlike in the ninth embodiment, the boil-off gas heat exchanger ( 30) as well as the lubricating oil L accumulated in the pressure reducing valve 40 and the lubricating oil filter 70a can be removed. That is, if the second lubricating oil processing line 63b is utilized in addition to a part of the first lubricating oil processing line 63a, the lubricating oil ( Since L) can be removed, unnecessary differential pressure generation can be suppressed.

However, when the second lubricating oil treatment line 63b is used, the high-temperature gas passes through the pressure reducing valve 40, so it may not satisfy the required pressure of the low-pressure engine 3b, which is the consumer 3 .

In this case, the pressure of the boil-off gas return line 31 may be adjusted through a valve (not shown) provided in the vapor phase boil-off gas delivery line 51 , or the pressure reducing valve 40 may be utilized.

As such, this embodiment solves the problem that occurs when the lubricant (L) remains in the pressure reducing valve 40 and the lubricant filter (70a), etc. when circulating the hot gas to remove the lubricant (L), thereby reducing the maintenance cycle can be minimized and the reliquefaction performance can be guaranteed. In addition, when the filtering function of the lubricant filter (70a) is damaged, it is possible to remove the lubricant (L) that can be introduced into the liquefied gas storage tank (10) in advance.

It goes without saying that the present invention is not limited to the above-described embodiment, and a combination of the above embodiments or a combination of at least one of the above embodiments and a known technology may be included as another embodiment.

In the above, the present invention has been described focusing on the embodiments of the present invention, but this is only an example and does not limit the present invention. It will be appreciated that various combinations or modifications and applications not illustrated in the embodiments are possible within the scope. Accordingly, descriptions related to modifications and applications that can be easily derived from the embodiments of the present invention should be interpreted as being included in the present invention.

1: Vessel 2: BOG reliquefaction system
3: Demand 3a: High pressure engine
3b: low pressure engine 3c: gas combustion device
L: Lubricating oil G: Liquid boil-off gas
HPC: BOG supply unit HPP: High pressure liquefied gas supply unit
LPP: Low-pressure liquefied gas supply unit ERS: BOG liquefaction unit
10: liquefied gas storage tank 20: boil-off gas compressor
20a: BOG compressor of low pressure stage 20b: BOG compressor of high pressure stage
21: boil-off gas supply line 211a, 211b: boil-off gas supply valve
212: low pressure boil-off gas supply line 213: low pressure boil-off gas supply valve
214: low pressure boil-off gas return line 215: low pressure boil-off gas return valve
22: separator 23: coalescer
24: gas valve train 30: boil-off gas heat exchanger
31: boil-off gas return line 311: high-pressure boil-off gas return valve
312: liquid boil-off gas return valve 32: auxiliary boil-off gas heat exchanger
33: boil-off gas bypass line 331: boil-off gas bypass valve
40: pressure reducing valve 50: gas-liquid separator
51: vapor phase boil-off gas delivery line 511: vapor phase boil-off gas delivery valve
512: vapor phase boil-off gas bypass line 513: vapor phase boil-off gas bypass valve
514: high-temperature boil-off gas supply line 515: high-temperature boil-off gas delivery line
516: high-temperature boil-off gas delivery valve 517: gas heater
52: housing 53: boil-off gas inlet
531: inlet-side bulkhead 532a, 532b: inlet-side inclined wall
54: liquid boil-off gas discharge unit 541a, 541b: discharge side inclined wall
55: weir 56: lubricant blocking plate
57: lubricant drain line 58: baffle
60: lubricating oil processing unit 61: hot gas injection unit
62: hot gas discharge unit 63a: first lubricating oil treatment line
63b: second lubricant treatment line 631: lubricant treatment valve
632: lubricant treatment valve 70a, 70b, 70c: lubricant filter
80: liquefied gas supply line 81: high-pressure liquefied gas supply line
82: high pressure pump 83: high pressure carburetor
84: low pressure liquefied gas supply line 85: forced vaporizer
86: heavy carbon separator 87: heater

Claims (7)

BOG compressor for compressing BOG generated in the liquefied gas storage tank in multiple stages;
a boil-off gas heat exchanger for exchanging the boil-off gas compressed in the boil-off gas compressor with the boil-off gas flowing into the boil-off gas compressor;
a pressure reducing valve for decompressing the boil-off gas that has been compressed in the boil-off gas compressor and then heat-exchanged in the boil-off gas heat exchanger;
a lubricant filter provided downstream of the pressure reducing valve; and
In order to remove the lubricating oil that is mixed with the boil-off gas at the high-pressure stage of the boil-off gas compressor and introduced into the boil-off gas heat exchanger, a lubricating oil processing unit injecting the high-temperature gas compressed in the boil-off gas compressor into the boil-off gas heat exchanger,
The lubricating oil processing unit may be configured such that the high-temperature gas compressed in the BOG compressor is supplied to a consumer via the BOG heat exchanger, or the high-temperature gas compressed in the BOG compressor is supplied to the BOG heat exchanger, the pressure reducing valve and the lubricant. to be supplied to the demanding place through the filter,
In the cleaning process of injecting the high-temperature boil-off gas compressed in the boil-off gas compressor into the boil-off gas heat exchanger in order to remove the lubricating oil remaining in the boil-off gas heat exchanger, the high-temperature boil-off gas discharged from the boil-off gas heat exchanger is removed from the pressure reducing valve. BOG reliquefaction system, characterized in that the lubricating oil removed from the BOG heat exchanger is prevented from flowing into the liquefied gas storage tank by transferring it from the upstream or downstream to the consumer and not passing it to the gas-liquid separator. The method of claim 1,
a low-pressure boil-off gas supply line connected from the liquefied gas storage tank to the consumer via at least one stage of the boil-off gas compressor;
a boil-off gas return line branched from the downstream of the boil-off gas compressor and connected to the liquefied gas storage tank via the boil-off gas heat exchanger and the pressure reducing valve;
a first lubricating oil treatment line branched from the downstream of the boil-off gas compressor in the low-pressure boil-off gas supply line and joined to the low-pressure boil-off gas supply line after passing through the boil-off gas heat exchanger; and
BOG reliquefaction system, characterized in that it further comprises a second lubricating oil treatment line branched from the lubricant filter and joined to the low pressure BOG supply line. According to claim 2, wherein the first lubricating oil treatment line,
BOG reliquefaction system, characterized in that it is branched from the BOG return line through the BOG heat exchanger and is joined to the low pressure BOG supply line upstream of the pressure reducing valve. 3. The method of claim 2,
The point at which the second lubricating oil treatment line joins the low pressure boil-off gas supply line is,
BOG reliquefaction system, characterized in that the first lubricating oil treatment line is downstream from the point where it joins the low pressure BOG supply line. According to claim 2, wherein the lubricating oil processing unit,
and a lubricating oil treatment valve provided in the second lubricating oil treatment line,
The lubricating oil treatment valve applies a pulsation to the hot gas through an opening degree control in the cleaning process, so that the lubricating oil of the boil-off gas heat exchanger, the pressure reducing valve and the lubricant filter is removed. 3. The method of claim 2,
a boil-off gas bypass line for passing the boil-off gas discharged from the liquefied gas storage tank to the boil-off gas compressor by bypassing the boil-off gas heat exchanger; and
Further comprising a boil-off gas bypass valve for controlling the flow of the boil-off gas bypass line,
The boil-off gas bypass valve,
In the cleaning process, BOG re-liquefaction characterized in that the low-temperature BOG discharged from the liquefied gas storage tank flows to the BOG bypass line so that the BOG injected into the BOG heat exchanger can maintain a high temperature state. system. A ship characterized in that it has the boil-off gas reliquefaction system according to any one of claims 1 to 6.

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