KR20200012809A - liquefaction system of boil-off gas and ship having the same - Google Patents

Abstract

The present invention relates to a gas processing system and a ship including the same which increase the operating stability of an entire system. The gas processing system comprises: a liquefied gas storage tank; a boil-off gas compressor which is arranged in a compressor room allowing periodic forced ventilation, and compresses boil-off gas of the liquefied gas storage tank in multiple stages to supply compressed boil-off gas to an engine; a reliquefaction device which is loaded on a reliquefaction skid arranged in the compressor room, and liquefies surplus boil-off gas which is not consumed by the engine in boil-off gas compressed by the boil-off gas compressor into a refrigerant; and a gas detector to detect a refrigerant leaking in the compressor room. The gas detector includes: a first gas detector installed on a middle portion of the reliquefaction skid to detect a refrigerant leaking from the reliquefaction device; and a second gas detector installed on an outlet portion of air ventilated in the compressor room to detect a refrigerant leaking from the reliquefaction device.

Description

Liquefaction system of boil-off gas and ship having the same}

The present invention relates to a gas treatment system and a vessel comprising the same.

Recently, liquefied gas such as liquefied natural gas and liquefied petroleum gas have been widely used in place of gasoline or diesel.

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

Such liquefied gas is stored in a liquefied gas storage tank installed on the ground or in a liquefied gas storage tank provided in a ship which is a transportation means for navigating the ocean. The liquefied petroleum gas is reduced by the liquefied propane is 1/260, butane is reduced to a volume of 1/230 has the advantage of high storage efficiency. The temperature and pressure required for driving the engine using such a liquefied gas as fuel may be different from the state of the liquefied gas stored in the tank.

In addition, when LNG is stored in the liquid phase, as heat penetrating into the tank, some LNG is vaporized to generate boil off gas (BOG), which may cause problems in the re-liquefaction system of the boil-off gas. In order to solve the problem by discharging the boil-off by discharging the boil-off gas to the outside (in the past, the boil-off gas was simply discharged to the outside to reduce the risk of damage to the tank by lowering the tank pressure). It is causing a problem of waste.

The present invention was created to solve the problems of the prior art as described above, an object of the present invention, while re-liquefying the evaporated gas generated in the liquefied gas storage tank with a refrigerant, the treatment of evaporated gas, flash gas, vent gas, etc. It is to provide a gas treatment system and a vessel containing the same by improving the efficiency of the entire system to improve the operational stability.

Gas processing system according to an aspect of the present invention, liquefied gas storage tank; An evaporative gas compressor disposed in a compressor room where periodic forced ventilation is performed and configured to compress the evaporated gas of the liquefied gas storage tank into multiple stages and supply the compressed gas to an engine; A reliquefaction apparatus mounted on a reliquefaction skid disposed in the compressor room and liquefying a surplus evaporation gas not consumed by the engine among refrigerants compressed by the evaporation gas compressor with a refrigerant; And a gas detector for detecting a refrigerant leaking in the compressor room, wherein the gas detector is installed at a central portion of the reliquefaction skid and detects the refrigerant leaking from the reliquefaction device; And a second gas detector installed at an outlet portion of the air vented in the compressor room to detect a refrigerant leaking from the reliquefaction apparatus.

In detail, the reliquefaction apparatus may liquefy the boil-off gas using an MR refrigerant, and the second gas detector may be provided to detect the MR refrigerant leaking from the reliquefaction apparatus.

In detail, the compressor room is periodically forced to ventilate using a sound pressure of a vent fan, and the second gas detector may be installed around the vent fan.

Specifically, the second gas detector may be installed below the vent fan.

In detail, the compressor room is periodically forced to ventilate through a duct through which the air escapes, and the second gas detector may be installed around the duct.

Specifically, the outlet portion of the air vented in the compressor room may be a position closer to the reliquefaction device than the boil-off gas compressor.

A ship according to one aspect of the present invention is characterized by having the gas treatment system.

The gas treatment system according to the present invention and the vessel including the same, while using liquefied gas or evaporated gas of the liquefied gas storage tank as the fuel of the propulsion engine, while re-liquefying the excess evaporated gas as a refrigerant, supplying or liquefied evaporated gas By improving the treatment of flash gas generated from boil-off gas, it is possible to improve liquefaction efficiency and reduce OPEX.

1 is a conceptual diagram of a gas treatment system according to an embodiment of the present invention.
2 and 3 are partial conceptual views of a gas treatment system according to an embodiment of the present invention.
4 is a partial plan view of a gas treatment system according to an embodiment of the present invention.

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

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. For reference, the liquefied gas may be LNG, but the present invention is not limited thereto, and the boiling point may be lower than room temperature to be liquefied for storage and may include all materials having a calorific value.

In addition, liquefied gas / evaporation gas in the present specification is classified based on the state inside the fuel tank, it is noted that due to the name is not necessarily limited to the liquid or gaseous phase.

The present invention includes a vessel equipped with a gas treatment system 1 described below, wherein the vessel may be a gas carrier, FSRU, FLNG, Bunkering vessel, etc., which stores gas as a cargo, but not a gas (a container, It can also be applied to commercial ships carrying minerals, etc., marine plants, etc.

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

Referring to Figure 1, the gas treatment system 1 according to an embodiment of the present invention, the liquefied gas storage tank 10, the boil-off gas compressor 20, the re-liquefaction apparatus 30, the gas-liquid separator 40, Forced vaporizer 50 is included.

The liquefied gas storage tank 10 stores the liquefied gas in the liquid phase. The liquefied gas storage tank 10 of the present embodiment may be a cargo tank such as a gas carrier, a membrane type, an independent SPB type, a MOSS type, or the like, and of course, an independent high pressure container type may also be used.

The liquid liquefied gas stored in the liquefied gas storage tank 10 is evaporated gas by natural vaporization due to external heat penetration, and the evaporated gas is discharged from the liquefied gas storage tank 10 to be a propulsion engine (ME) or a power generation engine ( GE or may be returned to the liquefied gas storage tank 10 after reliquefaction.

The liquefied gas storage tank 10 is provided with lines passing through the dome, the liquefied gas discharge line (L3) for discharging the liquefied gas through the evaporation gas discharge line (L1) for discharging the evaporated gas, and the transfer pump (11). And, liquefied gas return line (L31) for returning at least a portion of the liquefied gas in the liquefied gas discharge line (L3) may be provided to pass through the dome. In addition, the condensation return line (L22) for returning the liquefied gas by the reliquefaction apparatus 30 to be described later to the liquefied gas storage tank 10 may also be provided to pass through the dome.

The liquefied gas storage tank 10 may be provided in plural, and at least two liquefied gas storage tanks 10 provided with the evaporative gas discharge line L1 are integrated into one and then connected to the boil-off gas compressor 20. In this case, a portion integrating the boil-off gas discharge line L1 is referred to as a vapor main (VM).

In addition, the liquefied gas discharge line (L3) provided in at least two or more liquefied gas storage tank 10 is also connected to the forced vaporizer 50, the portion integrating the liquefied gas discharge line (L3) is the liquid main (LM) It is called liquid main.

Therefore, the liquefied gas or the boil-off gas may be mixed from each liquefied gas storage tank 10 using the vapor main VM and the liquid main LM, or may be distributed to each liquefied gas storage tank 10 upside down.

The boil-off gas compressor 20 compresses the boil-off gas discharged from the liquefied gas storage tank 10 and supplies it to the engine. The boil-off gas compressor 20 may have a structure for compressing the boil-off gas in multiple stages, and the pressure of the boil-off gas discharged by the boil-off gas compressor 20 may be a propulsion engine (ME) (ME-GI, XDF, etc.) or a power generation engine. Can be set according to the pressure of (GE) (DFDE).

For example, in this embodiment, the propulsion engine ME may be XDF, and the boil-off gas compressor 20 may have a six-stage compression structure. The boil-off gas compressor 20 may be provided on the boil-off gas discharge line L1 connected from the liquefied gas storage tank 10 to the propulsion engine ME and the power generation engine GE. On the downstream side, the boil-off gas discharge line L1 is branched and connected to the propulsion engine ME and the power generation engine GE, respectively.

Of course, in case there is a difference in the required pressure between the propulsion engine (ME) and the power generation engine (GE), the pressure control between the branched branch of the boil-off gas discharge line (L1) and the power generation engine (GE) or propulsion engine (ME) The valve may be provided with a gas valve train (not shown) or a gas valve unit (not shown).

In addition, the boil-off gas liquefaction line L2 branches from the boil-off gas discharge line L1 downstream of the boil-off gas compressor 20. The boil-off gas liquefaction line (L2) may be connected to the re-liquefaction apparatus 30 and the gas-liquid separator 40, which will be described later, the condensation return line (L22) provided between the gas-liquid separator 40 and the liquefied gas storage tank (10) Return the liquefied evaporated gas through the liquefied gas storage tank (10).

The boil-off gas compressor 20 may distribute the compressed boil-off gas to the propulsion engine ME and the reliquefaction apparatus 30. That is, the pressure of the boil-off gas flowing into the propulsion engine ME, the power generation engine GE, and the reliquefaction device 30 through the boil-off gas compressor 20 may be basically the same.

However, when lubricating oil is mixed in the process of compressing the boil-off gas by the boil-off gas compressor 20, the liquefied gas is mixed into the boil-off gas re-liquefied from the reliquefaction apparatus 30 and returned to the liquefied gas storage tank 10. There is a problem that the quality of the liquefied gas in the storage tank 10 is lowered.

Therefore, in this embodiment, in order to satisfy the requirement that the lubricating oil should not be mixed with the boil-off gas flowing into the reliquefaction apparatus 30, a lubricating oil free oil-free (oil-free) type compressor is used. In this case, the boil-off gas compressor 20 may be a centrifugal type.

The reliquefaction apparatus 30 liquefies the excess boil-off gas which is not consumed by an engine among the boil-off gas compressed by the boil-off gas compressor 20 with a refrigerant. In this case, the refrigerant may be an MR refrigerant in which a hydrocarbon-based material is mixed.

The reliquefaction apparatus 30 will be described in detail with reference to FIGS. 2 and 3. Hereinafter, the gaseous phase or the liquid phase is classified based on the refrigerant state in the refrigerant separator 33, and may be vaporized or liquefied during a heat exchange process, and the state of the refrigerant is not limited by the expression.

Referring first to FIG. 2, the reliquefaction apparatus 30 includes a refrigerant compressor 31, a refrigerant cooler 32, a refrigerant separator 33, a liquefier 34, a pressure reducing valve 35, and a receiver 36. The refrigerant circulation line L4 may connect the above components in series.

The refrigerant compressor 31 compresses the refrigerant. In this case, the refrigerant compressor 31 of the reliquefaction apparatus 30 illustrated in FIG. 2 may be provided as an oil-injected type in which lubricant is mixed when refrigerant is compressed.

The refrigerant cooler 32 cools the compressed refrigerant. Since the MR refrigerant is a mixture of materials having different boiling points, and the boiling point of some materials is increased by compression, a part of the MR refrigerant may be liquefied during cooling by the refrigerant cooler 32.

The refrigerant separator 33 separates the compressed and cooled refrigerant into gas-liquid separation. At this time, the refrigerant of the separated gas phase flows into the liquefier 34. In addition, the refrigerant may be partially passed through the liquefier 34 after being cooled in the refrigerant cooler 32 and before being introduced into the refrigerant separator 33, thereby allowing the lubricant to remain in the liquid phase so that the lubricant may remain in the gas phase refrigerant. You can do it.

Of course, the degree of cooling the refrigerant in the refrigerant cooler 32 and the degree of cooling through the liquefier 34 upstream of the refrigerant separator 33 may be set to such an extent that the lubricant does not solidify.

The liquid phase refrigerant separated by the refrigerant separator 33 may be joined in the middle of the feature stream of the liquefier 34, which will be described later.

The liquefier 34 heats the refrigerant and the boil-off gas to liquefy the boil-off gas. The liquefier 34 may be a heat exchanger having a plurality of streams, and the structure is not limited as the fin & tube type, the PCHE type, or the like.

The liquefier 34 is separated from the first stream, the refrigerant separator 33, which is partially passed after the refrigerant cooled in the refrigerant cooler 32 flows to the refrigerant separator 33 when viewed from the left side to the right direction based on the drawings. And a fourth stream through which the evaporated gas flows. The liquefier 34 also has a third stream through which the liquid refrigerant flowing back through the pressure reducing valve 35 flows.

The pressure reducing valve 35 decompresses the gaseous phase refrigerant separated by the refrigerant separator 33 downstream of the liquefier 34 and flows it back into the liquefier 34. The pressure reducing valve 35 may be a Joule-Thomson valve, and the refrigerant may be cooled and liquefied by the Joule-Thompson effect.

The receiver 36 temporarily stores the refrigerant via the liquefier 34 after decompression and transfers the refrigerant to the refrigerant compressor 31. The receiver 36 may be in the form of a tank, and may serve as a buffer so that the liquid phase does not flow into the refrigerant compressor 31.

The liquid refrigerant present in the receiver 36 may be stored in the receiver 36 instead of being delivered to the refrigerant compressor 31, and may be between the refrigerant separator 33 or the refrigerant separator 33 and the liquefier 34. It is also possible to deliver to the refrigerant circulation line (L4).

In order to change the liquid phase in the receiver 36 to the gas phase, a refrigerant return line L42 for returning the compressed refrigerant downstream of the refrigerant compressor 31 to the receiver 36 is provided between the refrigerant compressor 31 and the refrigerant cooler 32. Branched in the refrigerant circulation line (L4) of the receiver 36 may be connected upstream. When the high pressure / high temperature refrigerant compressed by the refrigerant compressor 31 returns to the receiver 36, the liquid phase refrigerant in the receiver 36 may be vaporized and transferred to the refrigerant compressor 31.

Referring to the refrigerant flow flowing along the refrigerant circulation line (L4) as follows. The refrigerant is cooled in the refrigerant cooler 32 and then partially passes through the first stream of the liquefier 34 and then enters the refrigerant separator 33. The gaseous refrigerant separated in the refrigerant separator 33 then exits via the second stream of the liquefier 34.

The gaseous phase refrigerant which flowed out flows into the pressure reducing valve 35 which will be described later, and is cooled (liquefied) by the Joule-Thompson effect during the pressure reduction. The refrigerant passing through the pressure reducing valve 35 flows into the liquefier 34 and heat-exchanges with the boil-off gas to liquefy the boil-off gas.

Of course, in the liquefier 34, the boil-off gas may be cooled while exchanging heat with other refrigerants besides the refrigerant passing through the pressure reducing valve 35. On the contrary, only the lowest temperature refrigerant passing through the pressure reducing valve 35 exchanges with the boil-off gas. You can also arrange to do so. In addition, the liquefier 34 may be a heat exchange between the refrigerant.

The refrigerant of the liquid phase separated from the refrigerant separator 33 may be in a state in which lubricating oil is mixed. The refrigerant may be introduced into the third stream (reduced after decompression of the refrigerant through the liquid refrigerant branch line L41). In the middle of the stream).

In other words, the present embodiment is provided such that the refrigerant mixed with the lubricating oil is joined at the midpoint instead of the starting point of the stream so that the lubricating oil does not freeze during low temperature heat exchange with the boil-off gas.

Of course, the reliquefaction apparatus 30 in FIG. 2 may include a lubricating oil separator for separating the lubricating oil upstream from the liquefier 34, a lubricating oil pump for circulating the separated lubricating oil to the refrigerant compressor 31, a lubricating oil cooler, and the like. It may be.

The reliquefaction apparatus 30 of FIG. 2 may be referred to as a lube oil type in that it uses a refrigerant compressor 31 in which lubricating oil is mixed during compression, whereas in the case of FIG. It may be referred to as a non-lube oil type as using the refrigerant compressor 31 of an oil-free (oil-free) type in which lubricant is not mixed.

Referring to FIG. 3, since the reliquefaction apparatus 30 is provided with a type in which the refrigerant compressor 31 is not mixed with lubricating oil, unlike in FIG. 2, a configuration for separating lubricating oil may be omitted. However, the reliquefaction apparatus 30 may include the components described with reference to FIG. 2, but the refrigerant does not pass through the liquefier 34 between the refrigerant cooler 32 and the refrigerant separator 33, and the refrigerant is a refrigerant. The cooler 32, the refrigerant separator 33, and the liquefier 34 may be provided in order.

In the reliquefaction apparatus 30 of FIG. 3, the refrigerant separator 33 may separate the gaseous refrigerant and the liquid phase refrigerant and transfer them to the liquefier 34 to increase heat exchange efficiency. The liquefier 34 is the first stream through which the refrigerant in the gas phase flows, the second stream through which the refrigerant depressurized by the pressure reducing valve 35 and re-introduced into the liquefier 34 flows, and the third stream through which the evaporating gas flows. The liquid phase refrigerant separated in the refrigerant separator 33 may be joined in the middle of the second stream.

In addition, the reliquefaction apparatus 30 of FIG. 3 may not provide a configuration in which lubricating oil is separately separated upstream of the refrigerant separator 33 and circulated to the refrigerant compressor 31.

In this reliquefaction apparatus 30, the reliquefaction vent line L21 is provided separately. On the flow of liquefied gas or evaporated gas, a vent function should be provided to prepare for an emergency situation, and the vent uses different vent masts according to pressure.

Specifically, the low pressure liquefied gas or the boil-off gas of the upstream of the boil-off gas compressor 20 (between the liquefied gas storage tank 10 and the boil-off gas compressor 20, for example, the buffer tank 51 to be described later) is a low pressure vent line ( L11 is delivered to the low pressure vent mast LV and vented, and the high pressure evaporation gas downstream of the evaporation gas compressor 20 (between the evaporation gas compressor 20 and the engine or the gas-liquid separator 40 to be described later) is a high pressure. It is delivered to the high pressure vent mast HV through the vent line L12 and vented.

However, as described above, since the high-pressure boil-off gas compressed by the boil-off gas compressor 20 is distributed to the engine and the re-liquefaction device 30, the pressure of the boil-off gas in the re-liquefaction device 30 is determined by the high-pressure ventane L12. It corresponds to the pressure of the boil-off gas vented through. Therefore, the vent in the reliquefaction apparatus 30 can also use a high pressure vent mast (HV).

However, if the reliquefaction apparatus 30 is to be vented to the high pressure vent mast (HV), when the boil-off gas compressor 20 is tripped (vented), the vent to the high pressure vent mast (HV) between the engine and the boil-off gas compressor 20 It is not distinguished from venting with the high pressure vent mast HV when the refrigerant leaks from the reliquefaction apparatus 30. That is, there is a problem in that the refrigerant leakage from the reliquefaction apparatus 30 cannot be confirmed in a boil-off gas vent situation due to a trip of the boil-off gas compressor 20.

Therefore, in this embodiment, in order to distinguish the vent of the reliquefaction apparatus 30 independently from the high pressure vent downstream of the boil-off gas compressor 20, the reliquefaction vent mast RV provided separately from the high pressure vent mast HV is provided. It can be provided. At this time, the reliquefaction vent line L21 is connected between the reliquefaction apparatus 30 and the reliquefaction vent mast RV to allow the refrigerant leaking from the reliquefaction apparatus 30 to be vented.

Therefore, the high pressure vent mast HV is vented by receiving the high pressure evaporation gas when the evaporation gas compressor 20 is tripped, and the reliquefaction vent mast RV is independent of the evaporated gas vented when the evaporation gas compressor 20 is tripped. By receiving the refrigerant from the reliquefaction apparatus 30 can be vented.

To this end, the reliquefaction vent line L21 is provided independently of the high pressure vent line L12 so that the evaporation gas delivered to the high pressure vent mast HV may not be introduced when the evaporation gas compressor 20 is tripped. The liquefied vent line L21 may be provided with a gas detector (not shown) for detecting a leak of the refrigerant from the reliquefaction apparatus 30.

Therefore, in the present embodiment, even in a situation where the boil-off gas is vented when the boil-off gas compressor 20 is tripped, the leak in the re-liquefaction apparatus 30 can be clearly confirmed based on the detection of the refrigerant in the re-liquefaction vent line L21.

The gas-liquid separator 40 carries out gas-liquid separation of the liquefied evaporated gas from the reliquefaction apparatus 30 to transfer the liquid evaporated gas to the liquefied gas storage tank 10. To this end, the gas-liquid separator 40 may be provided with a condensation return line (L22) for transmitting the liquid evaporated gas to the liquefied gas storage tank (10).

A purging valve 41 is connected to the condensation return line L22. When the reliquefaction apparatus 30 is stopped, the liquid vaporized gas separated from the gas-liquid separator 40 may be stagnant in the condensation return line L22. Therefore, in the present embodiment, in order to purge the inside of the condensation return line L22 when the reliquefaction apparatus 30 is stopped, the purging line L23 and the purging valve 41 may be directly connected to the condensation return line L22. have.

At this time, the purging valve 41 injects purging gas (nitrogen, inert gas, etc.) delivered from the purging gas supply unit 42 into the condensation return line L22 to liquefy the boiled gas in the condensation return line L22. It can be pushed out to the gas storage tank 10, in which the gas-liquid separator 40 is disposed above the liquefied gas storage tank 10, all the liquid evaporated gas without stagnation by using the pressure of the purging gas in addition to gravity Can be delivered to the liquefied gas storage tank (10).

However, the condensation return line L22 blocks the flow between the point where the purging gas is injected by the purging valve 41 from the gas liquid separator 40 when the purging valve 41 is opened, so that the purging gas is separated from the gas liquid separator 40. It is possible to smoothly push out the liquid evaporated gas in the condensation return line (L22) by the purging gas while suppressing the backflow.

In addition, the vaporized gas of the gas phase separated from the gas-liquid separator 40 is a flash gas, and the temperature may be a material having a low temperature or gaseous phase. At this time, the flash gas may be discharged from the gas-liquid separator 40 according to the internal pressure of the gas-liquid separator 40 to lower the internal pressure of the gas-liquid separator 40.

In the present embodiment, the flash gas may be directly injected into the liquefied gas storage tank 10 instead of being circulated to the boil-off gas compressor 20. That is, the gas-liquid separator 40 transfers the flash gas of the gaseous phase separated from the reliquefied evaporated gas to the liquefied gas storage tank 10 like the liquid vaporized gas.

To this end, the gas-liquid separator 40 may be provided with a flash gas discharge line (L24) for transmitting the flash gas of the gas phase to the liquefied gas storage tank (10). In addition, the flash gas discharge line (L24) can deliver the flash gas at a position lower than the condensation return line (L22) in the liquefied gas storage tank 10, specifically, the flash gas discharge line (L24) is a flash gas of the gaseous phase It can be delivered to the bottom of the liquefied gas storage tank (10).

Therefore, the flash gas may be liquefied by the liquefied gas while flowing into the liquefied gas at the bottom of the liquefied gas storage tank 10 along the flash gas discharge line L24.

Flash gas discharge line (L24) is directly connected to the bottom of the liquefied gas storage tank 10 to inject flash gas into the liquefied gas, or connected to the liquid main (LM) through the liquefied gas return line (L31) The flash gas of the gaseous phase may be delivered to the liquefied gas storage tank 10.

Therefore, the present embodiment, by returning the flash gas to the liquefied gas storage tank 10 in the re-liquefied evaporated gas can effectively lower the internal pressure of the gas-liquid separator 40, the flash gas to the boil-off gas compressor 20 Since it is not recycled to the furnace, the load of the boil-off gas compressor 20 is reduced. In addition, since the flash gas does not return to the reliquefaction apparatus 30 via the boil-off gas compressor 20, the liquefaction efficiency improvement in the reliquefaction apparatus 30 can also be expected.

The high-pressure ventane L12 may be connected to the gas-liquid separator 40, and when the over-pressure of the gas-liquid separator 40 is not resolved by flash gas discharge or the flash gas is not discharged, the gas-liquid separator 40 may be discharged. The boil-off gas may be delivered to the high pressure vent mast HV through the high pressure vent line L12 and vented.

The forced vaporizer 50 forcibly vaporizes the liquefied gas of the liquefied gas storage tank 10 and delivers the liquefied gas to the vaporized gas upstream of the vaporized gas compressor 20. In this case, a buffer tank 51 (Mist separator) in which the liquefied gas is forcibly mixed with the boil-off gas discharged from the liquefied gas storage tank 10 is provided upstream of the boil-off gas compressor 20 in the boil-off gas discharge line L1. The liquid phase may be prevented from flowing into the boil-off gas compressor 20, and the low pressure vent line L11 is connected to the buffer tank 51 so that the liquefied gas or the boil-off gas may be low pressure vent mast LV from the buffer tank 51. Can be vented.

As described above, the boil-off gas compressor 20 of this embodiment is a centrifugal type that is oil-free (oil-free) so that lubricating oil is not mixed in the boil-off gas delivered to the reliquefaction apparatus 30. )

However, when the evaporation gas is insufficient, it is necessary to supply the liquefied gas to the engine along with the evaporated gas. When the liquefied gas is mixed downstream of the evaporative gas compressor 20 while using the evaporative gas compressor 20 of the above type, Unlike the case of using the boil-off gas compressor 20 of the type (screw type, reciprocating type, etc.), it is difficult to control the flow rate change according to the load of the engine immediately. Furthermore, there is a fear that the liquefied gas to be mixed flows back into the boil-off gas compressor 20 and a trip occurs.

Therefore, the present embodiment uses a specific type of compressor so that lubricating oil does not flow into the reliquefaction apparatus 30, while delivering the forced vaporized liquefied gas to the boil-off gas upstream of the boil-off compressor 20 and mixes it. This embodiment prevents the deterioration of the quality of the liquefied gas when the liquefied evaporated gas is returned to the liquefied gas storage tank 10, and at the same time, the evaporative gas compressor 20 controls the discharge flow rate in response to the change of the engine load. In this way, the engine side supply amount of the liquefied gas and the boil-off gas can be effectively adjusted, so that the engine load fluctuation can be effectively coped and the compressor trip can be prevented.

4 is a partial plan view of a gas treatment system according to an embodiment of the present invention. For reference, each leakage scenario of FIG. 4 illustrates how the leaked refrigerant diffuses by ventilation when the refrigerant leaks at different positions of the reliquefaction skid 200.

Referring to FIG. 4, the gas treatment system 1 according to an embodiment of the present invention effectively detects a refrigerant leak in a compressor room 100 (CCR: Cargo Compressor Room) in which an evaporative gas compressor 20 is provided. can do. It demonstrates concretely below.

The compressor room 100 may be a space in which a boil-off gas compressor 20, a forced vaporizer 50, or the like is provided to change a state suitable for supplying liquefied gas or boil-off gas to the engine fuel.

At this time, since the compressor room 100 is a space that handles explosive substances such as evaporated gas, periodic ventilation may be forcibly performed for safety (for example, 30 times per hour).

At this time, the ventilation may be performed in various ways. The outside air is injected using a vent fan (not shown) that implements positive pressure and the atmosphere inside the compressor room 100 is discharged by using a duct (not shown). Using a vent fan (not shown) that implements a sound pressure, on the contrary, the outside air may naturally flow into the compressor room 100 while removing the atmosphere inside the compressor room 100 to the outside.

In the compressor room 100, a reliquefaction skid 200 mounted with the reliquefaction apparatus 30 described above may be disposed. The reliquefaction skid 200 may be a support frame on which the detailed configuration of the reliquefaction apparatus 30 mentioned in FIGS. 2 and 3 is mounted.

The present embodiment includes gas detectors 201 and 202 for detecting refrigerant leaking in the compressor room 100, and the gas detectors 201 and 202 are disposed at the center of the leak hazardous equipment to detect the refrigerant leak. Can be. In detail, the gas detectors 201 and 202 may be installed at the central portion A of the reliquefaction skid 200 to detect the refrigerant leaking from the reliquefaction apparatus 30.

However, in the case of using only the gas detectors 201 and 202 of the central portion A as described above, when the refrigerant leaked from the reliquefaction apparatus 30 is discharged to the outside by the ventilation of the compressor room 100, the gas detector 201 is used. , 202 is not detected because it is not close (leakage scenario 1 of FIG. 4).

Therefore, in the present embodiment, the gas detectors 201 and 202 are additionally installed in the outlet portion B of the vented air, in consideration of an aspect in which the leaked refrigerant spreads due to the ventilation of the compressor room 100, thereby reliquefying the liquid. The refrigerant leaking out of the device 30 can be clearly detected. The outlet portion of the atmosphere to be ventilated may be a position biased to the reliquefaction skid 200 in the compressor room 100, and may be a position closer to the reliquefaction apparatus 30 compared to the boil-off gas compressor 20.

In this case, the gas detectors 201 and 202 installed in the central portion A of the reliquefaction skid 200 are referred to as the first gas detector 201 and installed in the ventilation exit portion B in the compressor room 100. The gas detectors 201 and 202 may be referred to as a second gas detector 202, and the second gas detector 202 may be provided to detect MR refrigerant leaking from the reliquefaction apparatus 30.

Specifically, the second gas detector 202 may be installed at the periphery of the vent fan (lower side in consideration of the density of MR refrigerant compared to the atmosphere) when the compressor room 100 is ventilated with a vent fan using sound pressure. Alternatively, when the exit of the atmosphere is made of a duct may be installed around the duct. Of course, when both the vent pan and the duct are applied, the second gas detector 202 may be installed at the midpoint of the vent pan and the duct.

Accordingly, in the present embodiment, the gas detectors 201 and 202 are not installed only in the central portion A of the reliquefaction skid 200, but the ventilation outlet of the compressor room 100 containing the reliquefaction skid 200 is accommodated. By adding gas detectors 201 and 202 to the part B, it is possible to prevent the refrigerant leaking from the reliquefaction apparatus 30 from being detected due to the ventilation.

As described above, the present embodiment can effectively cope with the engine load while preventing lubricating oil from being mixed in the reliquefaction apparatus 30, and applies the return to the liquefied gas storage tank 10 instead of the circulation of the flash gas. ) It can reduce load and increase reliquefaction efficiency.

In addition, in this embodiment, the liquid liquefied by re-liquefied evaporation gas is condensed to directly purge to the line returned to the liquefied gas storage tank 10 to eliminate the liquid stagnation, to implement an independent vent in the reliquefaction apparatus 30 and reliquefaction In consideration of the ventilation of the compressor room 100 accommodating the skid 200, the gas detectors 201 and 202 may be installed to effectively identify the refrigerant leak.

The present invention encompasses all the embodiments generated by the combination of the above embodiments and known techniques, in addition to the embodiments described above.

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

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

1: gas treatment system 10: liquefied gas storage tank
11: transfer pump 20: evaporative gas compressor
30: reliquefaction apparatus 31: refrigerant compressor
32: refrigerant cooler 33: refrigerant separator
34: liquefier 35: pressure reducing valve
36: receiver 40: gas-liquid separator
41: purging valve 42: purging gas supply unit
50: forced vaporizer 51: buffer tank
100: compressor room 200: reliquefaction skid
201: first gas detector 202: second gas detector
ME: Propulsion engine GE: Power generation engine
LV: low pressure vent mast HV: high pressure vent mast
RV: Reliquefaction Vent Mist L1: Evaporative Gas Discharge Line
L11: low pressure vent line L12: high pressure vent line
L2: boil-off gas liquefaction line L21: reliquefaction vent line
L22: Condensation Return Line L23: Purging Line
L24: flash gas discharge line L3: liquefied gas discharge line
L31: liquefied gas return line L4: refrigerant circulation line
L41: Liquid refrigerant branch line L42: Refrigerant return line
LM: liquid main VM: vapor main

Claims (7)

Liquefied gas storage tanks;
An evaporative gas compressor disposed in a compressor room where periodic forced ventilation is performed and configured to compress the evaporated gas of the liquefied gas storage tank into multiple stages and supply the compressed gas to an engine;
A reliquefaction apparatus mounted on a reliquefaction skid disposed in the compressor room and liquefying a surplus evaporation gas not consumed by the engine among refrigerants compressed by the evaporation gas compressor with a refrigerant; And
It includes a gas detector for detecting the refrigerant leaking in the compressor room,
The gas detector,
A first gas detector installed at a central portion of the reliquefaction skid and detecting a refrigerant leaking from the reliquefaction apparatus; And a second gas detector for sensing. The method of claim 1, wherein the reliquefaction apparatus,
Liquefy the boil-off gas using MR refrigerant,
The second gas detector, the gas processing system, characterized in that provided to detect the MR refrigerant leaked from the reliquefaction apparatus. The method of claim 1, wherein the compressor room,
Periodic forced venting is achieved using sound pressure from the vent pan,
The second gas detector is installed around the vent fan. The method of claim 3, wherein the second gas detector,
Gas treatment system, characterized in that installed below the vent fan. The method of claim 1, wherein the compressor room,
Periodic forced venting occurs through ducts through which the air exits,
The second gas detector is installed around the duct. The outlet portion of the atmosphere vented in the compressor room,
And a position proximate to the reliquefaction device relative to the boil-off gas compressor. Ship having said gas treatment system of any one of Claims 1-6.

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