KR20200067724A - liquefaction system of boil-off gas and ship having the same - Google Patents

Abstract

The present invention relates to a gas treatment system and a ship including the same, capable of optimizing liquefaction efficiency of an evaporation gas in consideration of operating conditions and the like. The gas treatment system includes: a liquefied gas storage tank; a compressor including multiple stages operated by a single driving source, and configured to compress an evaporation gas generated in the liquefied gas storage tank and supply the compressed evaporation gas to an engine; a decompression valve for decompressing at least a part of the evaporation gas compressed by at least a first stage of the compressor; a cooling unit arranged in series with the decompression valve based on a flow of the evaporation gas, and configured to cool the evaporation gas with a refrigerant; an evaporation gas liquefaction line through which evaporation gases in at least two points of a downstream of the first stage of the compressor are transferred to the liquefied gas storage tank via the decompression valve and the cooling unit; and a cooling bypass line provided in the evaporation gas liquefaction line, and through which the evaporation gas bypasses the cooling unit, wherein the cooling bypass line is configured to adjust the flow of the evaporation gas according to a point at which the evaporation gas is introduced into the evaporation gas liquefaction line.

Description

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

The present invention relates to a gas treatment system and a ship including the same.

According to recent technology development, liquefied gas such as Liquefied Natural Gas and Liquefied Petroleum Gas has been widely used to replace gasoline or diesel.

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

The 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 that is a transportation means for navigating the ocean. The liquefied natural gas is liquefied to a volume of 1/600. It is reduced, and liquefied petroleum gas has the advantage of high storage efficiency because it is reduced to 1/260 of propane and 1/230 of butane by liquefaction. The temperature and pressure required to drive the engine using the 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 a liquid state, some LNG is vaporized to generate boil-off gas (BOG) as heat permeation into the tank occurs. In order to eliminate the risk of tank damage by lowering, the evaporated gas was simply discharged to the outside.) However, it tried to solve the problem by causing consumption, but this is causing environmental pollution and waste of resources.

The present invention was created to solve the problems of the prior art as described above, and the object of the present invention is to hybridize liquefaction using heat exchange with refrigerant and liquefaction by Joule-Thomson effect when decompressing and compressing evaporation gas at high pressure. It is to provide a gas treatment system capable of optimizing the liquefaction efficiency of evaporated gas in consideration of operating conditions and the like, and a vessel including the same.

Gas processing system according to an aspect of the present invention, a liquefied gas storage tank; Compressor composed of multiple stages operated by a single driving source and compressing evaporation gas generated in the liquefied gas storage tank to supply to the engine; A pressure reducing valve for reducing at least a portion of the boil-off gas compressed by at least one stage of the compressor; A cooling unit provided in series with the pressure reducing valve based on the flow of the evaporating gas and cooling the evaporating gas with a refrigerant; An evaporation gas liquefaction line allowing at least two points of evaporation gas downstream of the compressor to be delivered to the liquefied gas storage tank via the pressure reducing valve and the cooling unit; And a cooling bypass line provided in the liquefaction gas liquefaction line and allowing the evaporation gas to bypass the cooling unit, wherein the cooling bypass line has a flow of evaporation gas according to a point at which the evaporation gas flows into the liquefaction line. It is characterized by being adjusted.

Specifically, the compressor includes a low pressure stage and a high pressure stage, which are operated by one driving source and have different mixing modes of lubricating oil in the evaporation gas, and the pressure reducing valve comprises at least one of the evaporation gas compressed by at least the low pressure stage of the compressor. Some can be depressurized.

Specifically, the engine is a propulsion engine having a required pressure of 200 bar or more, the low pressure stage of the compressor pressurizes the evaporated gas to less than 100 bar, and the liquefied gas liquefaction line is downstream of the high pressure stage of the compressor and of the compressor. After extending between the low pressure stage and the high pressure stage, they may be joined to be provided to pass through the pressure reducing valve and the cooling unit.

Specifically, the evaporation gas liquefaction line and the cooling bypass line, the evaporation gas is passed through the pressure-reducing valve from the downstream of the high-pressure stage of the compressor to bypass the cooling unit so as to be liquefied by decompression, or the evaporation gas is The pressure reduction valve and the cooling portion may be passed through between the low pressure stage and the high pressure stage of the compressor to achieve liquefaction by reducing pressure and cooling.

Specifically, the evaporation gas liquefaction line and the cooling bypass line may allow the evaporation gas to be liquefied by reduced pressure or liquefied by reduced pressure and cooling depending on the operating state of the engine.

Specifically, the evaporation gas liquefaction line and the cooling bypass line allow the evaporation gas to be liquefied by decompression and cooling during anchoring and low speed navigation of the ship, and the evaporation gas is liquefied by decompression during medium speed navigation of the ship It may be made, and the flow of the liquefied gas liquefaction line may be blocked when the ship is sailing at high speed.

Specifically, it may further include a gas-liquid separator for gas-liquid separation of the evaporated gas that has been subjected to cooling or decompression by a refrigerant to transfer the liquid to the liquefied gas storage tank.

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

The gas treatment system according to the present invention and a vessel including the same are a hybrid system incorporating partial re-liquefaction of decompressing the evaporation gas and complete re-liquefaction of cooling the evaporation gas with a refrigerant. By adjusting, the liquefaction efficiency and system stability can be improved innovatively.

1 is a conceptual diagram of a gas processing system according to a first embodiment of the present invention.
2 is a conceptual diagram of a gas processing system according to a second embodiment of the present invention.
3 is a conceptual diagram of a gas processing system according to a third embodiment of the present invention.
4 is a conceptual diagram of a gas processing system according to a fourth embodiment of the present invention.
5 is a conceptual diagram of a gas processing system according to a fifth embodiment of the present invention.
6 is a conceptual diagram of a gas processing system according to a sixth embodiment of the present invention.
7 is a conceptual diagram of a gas processing system according to a seventh 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 associated with the accompanying drawings. In addition, it should be noted that, in addition to reference numerals to the components of each drawing in the present specification, the same components have the same numbers as possible even though they are displayed on different drawings. In addition, in describing the present invention, when it is determined that detailed descriptions of related well-known technologies may unnecessarily obscure the subject matter of the present invention, detailed descriptions thereof will be omitted.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. For reference, the liquefied gas may be LNG in the present specification, but is not limited thereto, and the boiling point is lower than normal temperature and is forcibly liquefied for storage, and may include all substances (LPG, ethane, ethylene, hydrogen, etc.) having a calorific value. .

Also, in this specification, liquefied gas/evaporation gas is classified based on the state inside the fuel tank, and it is noted that the name is not necessarily limited to liquid or gaseous phases.

The present invention includes a vessel equipped with a gas treatment system described below, wherein the vessel may be a gas carrier, FSRU, FLNG, bunkering vessel, etc. that stores gas as cargo, but is not a gas (container, mineral, etc.) Please note that it can also be applied to merchant ships and marine plants carrying people.

1 is a conceptual diagram of a gas processing system according to a first embodiment of the present invention.

Referring to Figure 1, the gas treatment system 1 according to the first embodiment of the present invention, the liquefied gas storage tank 10, the compressor 20, the evaporative gas heat exchanger 30, the pressure reducing valve 40, It includes a cooling unit 50, a gas-liquid separator 60.

The liquefied gas storage tank 10 stores liquefied gas in a liquid phase. The liquefied gas storage tank 10 of this embodiment may be a cargo tank of a gas carrier, may be a membrane type, an independent SPB type or a MOSS type, and of course, an independent high pressure container type is also possible.

The liquefied liquefied gas stored in the liquefied gas storage tank 10 is naturally vaporized due to external heat permeation and changes into evaporated gas, and the evaporated gas is discharged from the liquefied gas storage tank 10 to propel the engine 100 or the power generation engine ( It may be used as fuel of 110) or returned to the liquefied gas storage tank 10 after re-liquefaction.

Particularly, the present invention allows the liquefied gas storage tank 10 to be liquefied by at least reduced pressure among liquefied by reduced pressure and liquefied by refrigerant cooling, so that efficient reliquefaction according to the amount of evaporated gas can be realized. do.

The liquefied gas storage tank 10 is provided with a dome that serves as a passage between the inside and the outside, and lines through the dome are provided. In addition, a plurality of liquefied gas storage tanks 10 may be provided, and the lines via the dome in each liquefied gas storage tank 10 may be connected to each other.

At this time, the part connected to each other while the liquefied gas of the liquefied gas storage tank 10 flows is called a liquid main, and the part connected to each other while the evaporation gas of the liquefied gas storage tank 10 flows is called vapor main. It is called.

Therefore, the liquefied gas or the evaporated gas is mixed from each liquefied gas storage tank 10 using a vapor main and a liquid main, or can be distributed upside down to each liquefied gas storage tank 10.

Vapor main is connected to the evaporation gas supply line (L10) to the engine may be at least a part of the liquefied gas storage tank 10 of the plurality of liquefied gas storage tanks 10 (liquefied gas storage tank 10 provided exclusively for fuel) E) is discharged from the evaporated gas is delivered to the compressor (20).

On the other hand, the liquid main evaporation gas liquefaction line (L20) is connected, the at least one of the evaporation gas of the liquid liquefied by the pressure reducing valve 40 of the pressure reducing valve 40 and the cooling unit 50 through the liquid main to the liquefied gas storage tank (10) It can be introduced into the interior.

The lines described herein are connected to the vapor main or liquid main depending on the state of the gas flowing therein (liquid or gaseous) and may not directly penetrate the dome, but are not limited thereto. That is, a vapor main or the like is not separately provided, and the boil-off gas supply line L10 is provided to directly penetrate the dome to connect the inside and the outside of the liquefied gas storage tank 10.

The compressor 20 compresses the boil-off gas generated in the liquefied gas storage tank 10 and supplies it to the engine. Compressor 20 is provided with a structure having a plurality of compression stages 21, it is possible to compress the evaporation gas in multiple stages to meet the required pressure of the engine.

That is, the pressure of the boil-off gas discharged from the compressor 20 may be set to the required pressure of the engine. In this embodiment, the engine may include the propulsion engine 100 and the power generation engine 110, and the propulsion engine (100) may have a required pressure of about 200bar to 400bar (hereinafter referred to as high pressure) as ME-GI, or may have a required pressure of about 15bar to 50bar (hereinafter referred to as low pressure) as X-DF.

On the other hand, in the case of the power generation engine 110, it may have a required pressure similar to that of the X-DF, and the required pressure of the power generation engine 110 may be about 10 bar or less (hereinafter referred to as a low pressure encompassing the X-DF required pressure). It is not limited.

The plurality of compression stages 21 constituting the compressor 20 may be connected to be operated by one driving source (motor, shaft, etc.), and at least a portion of the compression stage 21 downstream of the return line (illustrated) May not be provided, and the compression ratio of the compression stage 21 may be varied through unloading control (no-load operation) or the like. In addition, the number of compression stages 21 may vary depending on the type of engine or the manufacturer of the compressor 20, and may be provided in 5 or 6 stages, for example.

For example, the multi-stage compressor 20 of Burckhardt may be 5 stages, and the multi-stage compressor 20 of Kobelco may be 6 stages.

At this time, the multi-stage compressor 20 may be divided into a low-pressure stage and a high-pressure stage. The low-pressure stage and the high-pressure stage may be classified according to the mixing mode of the lubricating oil as boiled gas compressed by the compression stage 21.

For example, in the case of the 5-stage compressor 20 of Burckhardt, in the case of the 1-3-stage compression stage 21, lubricating oil is not mixed into the evaporation gas during compression, but in the case of the 4-5-stage compression stage 21, the evaporation gas during compression There is a fear that lubricant may be mixed within. At this time, the above 5 stage compressor 20 can be divided into a low pressure stage and a 4-5 stage to a high pressure stage up to 3 stages.

On the other hand, in the case of Kobelco's 6-stage compressor 20, there is no mixing of lubricating oil in the evaporation gas when compressed to 1-5 stages, whereas in the 6-stage, lubricating oil mixing occurs, so the low-pressure stage up to the 5th stage and the high-pressure stage are 6 It can be referred to as.

That is, the compressor 20 may include a low pressure stage and a high pressure stage, which are operated by a single driving source and have different mixing modes of the lubricating oil in the evaporation gas during compression. It may be a compression stage 21 with a high possibility of mixing of lubricant.

In addition, the compression stage 21 provided at the most downstream of the compressor 20 may be referred to as a final stage, and the compression stage 21 upstream of the final stage may all be referred to as an intermediate stage. For example, in the 5-stage compressor 20 of Burckhardt, the final stage is 5 stages, and the intermediate stage may be any one of 1-4 stages.

An intercooler (not shown) may be provided downstream of the compression stage 21 of the compressor 20, and the intercooler uses a refrigerant that does not limit the evaporation gas whose volume increases as the temperature increases as it is compressed by the compression stage 21. By cooling, it is possible to ensure the compression efficiency at the compression stage 21 downstream of the intercooler. The intercooler may be provided at each of the first stage and downstream of the final stage, but may be omitted at the downstream of the final stage.

The pressure of the boil-off gas discharged by the final stage of the compressor 20 may correspond to the required pressure of the propulsion engine 100, but the required pressure of the power generation engine 110 may not reach the required pressure of the propulsion engine 100. have. At this time, the liquefied gas storage tank (10) connected to the evaporation gas supply line (L10) from the liquefied gas storage tank (10) via all compression stages (21) of the compressor (20) and connected to the propulsion engine (100) It may also be branched to be branched from the middle end of the compressor 20 to be connected to the power generation engine 110.

At this time, the point at which the boil-off gas supply line (L10) branches to the power generation engine 110 may vary depending on the required pressure of the power generation engine 110 and the compression ratio of the compression stage 21, for example, a 5-stage compressor 20 In the evaporation gas supply line (L10) may be branched from the second or third stage compression stage 21 and connected to the power generation engine 110.

For reference, the boil-off gas supply line L10 via the compression stage 21 may be connected to a separate demand source in addition to the engine. At this time, the separate demand destination may mean a gas combustion device (GCU), a boiler, or the like. . In addition, the point at which the evaporation gas supply line L10 branches from the compressor 20 to a separate customer is not particularly limited, and the point at which the evaporation gas supply line L10 branches to the power generation engine 110 may be shared.

The evaporation gas liquefaction line L20 may be branched to the evaporation gas supply line L10 connected to the engine via the compressor 20. The evaporation gas liquefaction line (L20) is a line through which the evaporation gas is liquefied and returned to the liquefied gas storage tank 10 via a pressure reducing valve 40 and a cooling unit 50, which will be described later.

The boil-off gas liquefaction line (L20), so that at least two points of boil-off gas from the first stage downstream of the compressor 20 is delivered to the liquefied gas storage tank 10 via the pressure reducing valve 40 and the cooling unit 50. Can be. As an example, as shown in the drawing, the evaporation gas liquefaction line (L20) extends between the high-pressure stage (5th stage) downstream of the compressor 20 and the low pressure stage and the high-pressure stage (3 stages) of the compressor 20, and then joins to reduce the pressure. It may be provided to pass through the valve 40 and the cooling unit 50.

Boil-off gas Boil-off gas flowing into the liquefaction line (L20) may be the excess boil-off gas that is discharged from the liquefied gas storage tank 10 but is not consumed by an engine or the like.

However, in order to liquefy the boil-off gas through the Joule-Thomson effect when the pressure is reduced by the pressure-reducing valve 40 to be described later, the pressure of the boil-off gas flowing into the pressure-reducing valve 40 must be sufficient, wherein the pressure is about 100 bar or so (value May be).

When the propulsion engine 100 is a ME-GI engine having a required pressure of 200 bar or more, the discharge pressure of the high pressure stage in the 5-stage compressor 20 is 100 bar or more. Accordingly, the boil-off gas flowing into the boil-off gas liquefaction line (L20) downstream of the high-pressure stage can be liquefied while being depressurized by the pressure reducing valve (40).

However, in the 5-stage compressor 20, the low-pressure stage can pressurize the evaporation gas to less than 100 bar, so that the evaporation gas flowing into the evaporation gas liquefaction line (L20) between the low-pressure stage and the high-pressure stage is sufficiently liquefied using only the pressure reducing valve (40). You may not be able to. Therefore, in this case, it is possible to secure liquefaction efficiency by adding cooling by the cooling unit 50.

The two types of liquefaction as described above can be selectively performed according to the operating state of the engine, the operating state of the ship, and environmental conditions, which will be described in detail below.

However, if the propulsion engine 100 is an X-DF engine having a required pressure of 100 bar or less, as described above, if the discharge pressure at the final stage of the compressor 20 is limited to the required pressure of the propulsion engine 100, the compression stage ( The evaporated gas compressed by 21) has a problem that liquefaction can be properly performed only through both decompression and cooling.

Therefore, in the present exemplary embodiment, when the propulsion engine 100 has a required pressure of less than 100 bar, the final discharge pressure of the compressor 20 can be liquefied only by decompression and in addition to liquefaction of evaporation gas through decompression and cooling. Can be adjusted.

That is, the compressor 20, in order to prepare for the case where the required pressure of the propulsion engine 100 is less than 100 bar which is insufficient to implement liquefaction by the Joule-Thomson effect, so that the discharge pressure at the final stage may exceed the required pressure of the engine Can be prepared.

Of course, in addition to using a low pressure engine as the propulsion engine 100, at least two multi-stage compressors 20 are provided, and the upstream compressor 20 compresses evaporation gas in accordance with the required pressure of the propulsion engine 100, It is also possible for the downstream compressor 20 to implement additional compression for liquefaction.

In addition, the compressor 20 is provided with a type capable of adjusting the compression ratio, so that the discharge pressure at the final stage can be adjusted to correspond to the required pressure of the engine. In detail, the compressor 20 lowers the discharge pressure of the final stage to 100 bar or less when the engine can consume all of the evaporated gas generated from the liquefied gas storage tank 10 (when the ship is sailed at high speed) and requires the engine. Can be pressured.

On the other hand, if excess evaporation gas is generated and evaporation gas is required to be liquefied, the compressor 20 may increase the discharge pressure of the final stage to 100 bar or more to enable liquefaction by decompression. However, a pressure control valve 101 may be provided between the compressor 20 and the engine so that boil-off gas exceeding the required pressure of the propulsion engine 100 does not flow into the propulsion engine 100.

The pressure regulating valve 101 may be a valve that reduces the pressure of the boil-off gas discharged from the compressor 20 to meet the required pressure of the engine (the propulsion engine 100 and the power generation engine 110, etc.). For reference, a valve not shown as a pressure regulating valve 101 in the drawing, but displayed on the upstream of the engine, indicates a gas valve train or gas valve unit that finely regulates the flow rate and pressure. Can be.

That is, the compressor 20 of the present embodiment, when the propulsion engine 100 is ME-GI, compresses the evaporation gas according to the required pressure of the propulsion engine 100 and supplies it to the propulsion engine 100, but the excess evaporation gas is It may be branched between the low pressure stage and the high pressure stage (downstream of the intermediate stage below 100 bar) to be liquefied by reduced pressure & cooling, or branched downstream of the high pressure stage and liquefied under reduced pressure.

On the other hand, when the propulsion engine 100 is X-DF, the compressor 20 compresses the evaporation gas above the required pressure of the propulsion engine 100, and uses only decompression (hereinafter referred to as decompression only in terms of decompression and refrigerant cooling). It means only decompression.) It can be sufficiently liquefied, and the pressure regulating valve 101 upstream of the engine can lower the pressure of the evaporated gas to the required pressure of the engine.

However, when the propulsion engine 100 is an X-DF and wants to liquefy the boil-off gas by using cooling in addition to decompression (when the ship is moored, etc.), the compressor 20 is at the required pressure of the propulsion engine 100. The boil-off gas can be compressed and supplied to the engine, and the excess boil-off gas can be liquefied through cooling of the refrigerant even if it is not sufficiently liquefied by decompression alone.

In this way, the compressor 20 discharges the evaporation gas at the final stage according to the required pressure of the propulsion engine 100 when the propulsion engine 100 is ME-GI, and when the propulsion engine 100 is X-DF The evaporation gas can be discharged at the final stage so as to exceed the required pressure of the yen propulsion engine 100, thereby ensuring stable liquefaction of excess evaporation gas regardless of the type of propulsion engine 100.

The evaporation gas heat exchanger 30 cools the evaporation gas compressed by at least one stage of the compressor 20 and introduced into the evaporation gas liquefaction line L20 with the evaporation gas flowing into the compressor 20. The boil-off gas heat exchanger 30 may be configured to precool excess boil-off gas to be liquefied.

For example, the boil-off gas heat exchanger 30 cools the boil-off gas branching between the low and high-pressure stages of the compressor 20 with boil-off gas flowing into the compressor 20, or branches downstream from the final stage of the compressor 20. The boil-off gas can be cooled by the boil-off gas flowing into the compressor 20.

However, since the boil-off gas flowing into the compressor 20 is heated in the boil-off gas heat exchanger 30, there is a fear that the compression ratio may drop, and when the flow rate of the excess boil-off gas is too large, the boil-off gas is a boil-off gas supply line ( After bypassing the evaporation gas heat exchanger (30) and bypassing the evaporation gas heat exchanger (30) through the evaporation gas bypass line (L30) to rejoin the evaporation gas supply line (L10), the compressor ( 20).

The pressure reducing valve 40 depressurizes at least a portion of the evaporated gas compressed by at least one stage (eg, at least a low pressure stage) of the compressor 20. At this time, at least part means the surplus of the evaporated gas discharged from the liquefied gas storage tank 10.

The pressure reducing valve 40 may be a Joule-Thomson valve, and after being compressed by the compressor 20 at a predetermined pressure or more, the boil-off gas pre-cooled in the boil-off heat exchanger 30 is decompressed, and boil-off gas is obtained through the Joule-Thomson effect. It can liquefy at least a part of.

That is, since at least a part of the boil-off gas (surplus boil-off gas) among the boil-off gas compressed by the compressor 20 flows into the pressure-reducing valve 40, at least a part of the boil-off gas in the pressure-reducing valve 40 is liquefied by the reduced pressure, Liquefaction by the pressure reducing valve 40 may be referred to as a partial reliquefaction system.

The pressure reducing valve 40 is provided downstream of the compression stage 21 in the evaporation gas liquefaction line (L20), as described above, the evaporation gas liquefaction line (L20) between the low and high pressure stages of the compressor 20 or the high pressure stage ( Final stage) Downstream evaporation gas is introduced.

In order to implement liquefaction through the Joule-Thomson effect when reducing pressure by the pressure reducing valve 40, it is preferable that the pressure of the evaporation gas flowing into the pressure reducing valve 40 is 100 bar or more. Therefore, when the evaporation gas downstream of the high pressure stage flows into the pressure reduction valve 40 through the evaporation gas liquefaction line L20, liquefaction by pressure reduction can be implemented.

On the other hand, when the evaporation gas between the low-pressure stage and the high-pressure stage flows into the pressure-reducing valve 40, even if the pressure is reduced, the degree of decompression is not great, so the temperature drop is not sufficient and liquefaction may not be achieved. However, the present embodiment may include a cooling unit 50 that cools and liquefies the evaporation gas with a separate refrigerant so that liquefaction is possible even in this case.

Since lubricating oil may be mixed in the evaporation gas downstream of the high pressure stage, liquefaction is possible only by depressurization, but there is a fear of deteriorating the quality of the liquefied gas when returned to the liquefied gas storage tank 10. Therefore, there is a need for a configuration that liquefies and returns the boil-off gas at a high pressure stage upstream (low pressure stage) where there is no possibility of mixing of lubricant.

However, as described above, since the evaporation gas at the low pressure stage may not reach a pressure sufficient to implement liquefaction by decompression (for example, 100 bar or more), the present invention is intended to solve this when liquefying the evaporation gas at the low pressure stage , A hybrid re-liquefaction system may be provided in which a partial re-liquefaction system is reduced in pressure and a full re-liquefaction system of refrigerant heat exchange is added.

However, depending on the need to prevent lubricating oil mixing, liquefaction by depressurization or liquefaction by decompression and refrigerant cooling is selected, as shown in the drawing, a five-stage compressor 20 (the point where sufficient pressure is reached for liquefaction through decompression) This may be the case (after the fourth stage) is a point where the mixing mode of the lubricant is different (upstream from the third and fourth stages).

For reference, in the case of the above-mentioned six-stage compressor 20, the point at which a sufficient pressure for liquefaction through decompression is reached (after the fifth stage) is the same as the point at which the mixing mode of the lubricant changes (after the fifth stage), liquefied evaporation gas It is based on the reduced pressure, but it is noted that whether or not the cooling unit 50 is used may vary depending on other variables (engine operation state, evaporation gas flow rate, etc.) regardless of the need to prevent lubricant mixing.

The cooling unit 50 is provided in series with the pressure reducing valve 40 based on the flow of the evaporated gas. The cooling unit 50 may be provided upstream of the pressure reducing valve 40 on the liquefied gas liquefaction line L20 as shown in the drawing, but vice versa, and may be provided downstream of the evaporated gas heat exchanger 30. have.

Since the cooling unit 50 of the present invention cools the excess pre-cooled gas through the evaporating gas heat exchanger 30, the cooling unit 50 is used alone to liquefy the evaporating gas. It is possible to significantly reduce the load (capacity) of the cooling unit 50 compared to the system. Therefore, the present invention has the effect of significantly reducing equipment costs and operating costs, such as the cooling unit 50.

Also, as will be described later, since the boil-off gas flowing into the cooling unit 50 of the present invention is pre-cooled by the boil-off gas heat exchanger 30, it is possible to minimize heavy hydrocarbons for pre-cooling of the coolant itself in the coolant cycle. Cost reduction through improvement can also be achieved.

In addition, the cooling unit 50 cools the evaporation gas with a refrigerant. That is, unlike the decompression valve 40 that realizes partial liquefaction through the Joule-Thomson effect by decompression, the cooling unit 50 cools the evaporation gas to a boiling point or lower using a refrigerant having a sufficient low temperature and flow rate to achieve complete liquefaction. It is a configuration that can be implemented.

At this time, the refrigerant used by the cooling unit 50 may be nitrogen or a mixed refrigerant. Here, the mixed refrigerant means a refrigerant in which hydrocarbons (methane, ethane, propane, butane, etc.) having different carbon numbers per molecule are mixed in a certain ratio according to the commonly used in the field of processing LNG.

Specifically, the mixed refrigerant means a refrigerant in which light hydrocarbons (methane, ethane) having 2 or less carbon atoms per molecule, heavy hydrocarbons (propane, butane, etc.) having 3 or more carbon atoms per molecule, and some nitrogen are mixed.

In addition, when a mixed refrigerant is used, heat exchange between mixed refrigerants is used. Since the boiling point of light hydrocarbons in the mixed refrigerant is lower than that of heavy hydrocarbons, the mixed refrigerant may partially generate gas-liquid mixing.

Therefore, the existing refrigerant systems using a common mixed refrigerant have a configuration that separates the gas phase and the liquid phase from the mixed refrigerant and separately flows them to exchange heat with each other.

However, in the case of the present embodiment, while the cooling unit 50 uses a mixed refrigerant as a refrigerant, a mixed refrigerant containing light hydrocarbons having a low carbon number per molecule may be used. That is, the mixed refrigerant of this embodiment is a mixed refrigerant in which light hydrocarbons having 2 or less carbon atoms per molecule and heavy hydrocarbons having 3 or more carbon atoms per molecule are mixed refrigerants, but the ratio of light hydrocarbons is relatively large compared to that of heavy hydrocarbons, and thus the main component can be achieved.

Alternatively, the mixed refrigerant of the present embodiment may include a mixed hydrocarbon having 2 or less carbon atoms per molecule, but a heavy hydrocarbon having 3 or more carbon atoms per molecule may be omitted.

In the case of a conventional mixed refrigerant in which a heavy hydrocarbon having a high boiling point is included in a sufficient ratio, the liquid hydrocarbon is liquefied during the heat exchange process between the mixed refrigerants after the initial operation (at the time of initial refrigerant pre-cooling) and after the liquefied heavy hydrocarbon. It is common to cool the refrigerant so that the refrigerant can absorb a sufficient amount of heat as a whole.

However, in the case of the mixed refrigerant of the present invention containing light hydrocarbons, which are not easy to liquefy because of their low boiling point, since there is no (almost) heavy hydrocarbons to be liquefied, precooling of the refrigerant using liquid medium hydrocarbons during initial operation is insufficient. There is an unsuccessful problem.

Of course, the present invention overcomes this problem in that the boil-off gas flowing into the cooling unit 50 is precooled in the boil-off gas heat exchanger 30 or the boil-off gas is used for precooling of the refrigerant as mentioned above. However, the precooling using evaporation gas will be described in detail in other examples below.

Cooling unit 50 includes a cooler 51, a refrigerant compressor 52, a refrigerant cooler 53, a refrigerant valve 54, a refrigerant tank 55, the refrigerant circulation line (L50) the above components in series It forms a closed loop through which the refrigerant circulates while connecting.

The cooler 51 cools the boil-off gas immediately before being transferred to the pressure-reducing valve 40 via the boil-off gas heat exchanger 30 through the boil-off gas liquefaction line L20, and cools it by heat exchange with the refrigerant. In this case, the cooling of the evaporation gas through the cooler 51 may be performed at a temperature equal to or higher than the boiling point of the evaporation gas, considering that there is an additional drop in temperature due to reduced pressure downstream of the cooler 51.

In addition, the cooler 51 may include a stream through which evaporation gas flows and a stream through which refrigerant flows, and may include two or more streams through which refrigerant flows. Specifically, the cooler 51 is provided in a structure having at least three streams in which the refrigerant before decompression by the refrigerant valve 54, the refrigerant after decompression by the refrigerant valve 54, and the evaporation gas flow independently.

Therefore, the cooler 51 may be configured to implement heat exchange between the mixed refrigerants described above in addition to heat exchange between the evaporation gas and the refrigerant. For reference, the refrigerant that cools the evaporation gas proactively may be refrigerant introduced into the cooler 51 after depressurization by the refrigerant valve 54.

The cooler 51 may be any structure capable of having the above-described stream, and furthermore, the evaporative gas-refrigerant heat exchanger and the refrigerant-refrigerant heat exchanger may be integrated into one, while being provided separately.

The refrigerant compressor 52 compresses the refrigerant. The refrigerant compressor 52 may be provided in the same/similar multiple stages as the compressor 20 for compressing the boil-off gas, and the compression method (centrifugal, reciprocating, screw-type, etc.) is not limited.

The compression pressure of the refrigerant compressor 52 may be 4 to 30 bar, but is not limited thereto. Further, even if the refrigerant is compressed by the refrigerant compressor 52 and then depressurized by the refrigerant valve 54, the mixed refrigerant of the present invention may not liquefy in the circulation process because the light hydrocarbon is a main component.

The refrigerant cooler 53 cools the compressed refrigerant. The refrigerant cooler 53 may cool the refrigerant whose temperature has increased while being compressed by the refrigerant compressor 52 using various methods that are not limited. As described in other embodiments below, unlike the drawings of the present embodiment, the refrigerant cooler 53 may cool the refrigerant using evaporation gas.

The refrigerant valve 54 depressurizes the cooled refrigerant. At this time, the refrigerant valve 54 may be located upstream and downstream of the cooler 51 based on the flow of the refrigerant on the refrigerant circulation line L50. That is, the refrigerant discharged from the cooler 51 may flow back into the cooler 51 after passing through the refrigerant valve 54.

Refrigerant circulation line (L50), the refrigerant compressor 52, the refrigerant cooler 53, the refrigerant valve 54, the cooler 51, the refrigerant compressor 52 sequentially connected in series can form a closed loop. As described, the cooler 51 has at least two streams through which refrigerant flows.

Therefore, the refrigerant circulation line (L50), the refrigerant compressor 52, the refrigerant cooler 53, the first stream of the cooler 51 (refrigerant before decompression by the refrigerant valve 54), the refrigerant valve 54, the cooler ( The second stream of 51 (refrigerant after decompression by the refrigerant valve 54) and the refrigerant compressor 52 may be sequentially connected in series.

Since the first stream of the cooler 51 before entering the refrigerant valve 54 may have a higher temperature than the second stream of the cooler 51 after passing through the refrigerant valve 54, the refrigerant in the first stream is the second stream. The refrigerant in the stream may be cooled, and the refrigerant in the second stream may implement cooling of the evaporation gas.

The refrigerant tank 55 temporarily stores refrigerant. The refrigerant tank 55 may be provided on the refrigerant circulation line L50 to adjust/buffer the circulation flow rate and circulation pressure of the refrigerant.

The refrigerant tank 55 may also be used for replenishing the refrigerant, and in order to maintain the ratio of light hydrocarbons contained in the refrigerant, replenishment of the hydrocarbon may be performed through the refrigerant tank 55.

Of course, as described above, since the refrigerant of the present invention is a mixed refrigerant, light hydrocarbons may be a main component, and thus a facility for replenishing heavy hydrocarbons may be reduced or omitted. For reference, in the case of nitrogen included in the mixed refrigerant, a nitrogen generator (N2 generator) basically provided on the ship may be used as a supplementary facility.

In the present embodiment, the cooling unit 50 and the pressure reducing valve 40 are provided in series in the evaporation gas liquefaction line L20, to implement a case of liquefying only with reduced pressure as described above, the evaporation gas liquefaction line L20 In the cooling bypass line (L21) is provided so that the evaporation gas bypasses the cooling unit 50.

The cooling bypass line L21 may be branched upstream of the cooler 51 in the liquefied gas liquefaction line L20 and then joined downstream of the cooler 51 and upstream of the pressure reducing valve 40. Therefore, the boil-off gas compressed by at least one stage of the compressor 20 is primary cooled in the boil-off gas heat exchanger 30 along the boil-off gas liquefaction line L20, secondary cooled in the cooling unit 50, and the pressure reducing valve. It is liquefied while being decompressed at 40, primary cooling in the evaporative gas heat exchanger 30 along the evaporative gas liquefaction line L20, bypassing the cooling unit 50 through the cooling bypass line L21, and the pressure reducing valve 40 It can be liquefied under reduced pressure.

However, in the latter case, sufficient compression of evaporation gas is required to realize liquefaction only by decompression. Therefore, in the cooling bypass line L21, the flow of the evaporation gas may be adjusted according to the point at which the evaporation gas flows into the evaporation gas liquefaction line L20.

For example, when the boil-off gas enters the boil-off gas liquefaction line (L20) downstream from the high-pressure stage, the boil-off gas is compressed to a sufficient pressure, so the cooling bypass line (L21) is controlled so that the boil-off gas flows. In the following description, it is noted that the flow regulation/control in the line can be made by means such as a valve (not shown) provided in the line and a control unit (not shown) can be used.

On the other hand, when the boil-off gas flows into the liquefied-gas liquefaction line (L20) between the low-pressure stage and the high-pressure stage, the boil-off gas is compressed to a pressure that is not sufficient to be liquefied by depressurization alone, so the cooling bypass line (L21) flows the boil-off gas. Can be controlled not to. Therefore, in this case, the evaporated gas is liquefied through both the cooling unit 50 and the pressure reducing valve 40.

That is, in the present embodiment, the evaporation gas liquefaction line (L20) and the cooling bypass line (L21), so that the evaporation gas passes through the pressure reducing valve 40 from the high-pressure end downstream of the compressor 20 to bypass the cooling unit 50 Liquefaction by decompression can be achieved, or evaporation gas is passed through the decompression valve 40 and the cooling unit 50 from between the low and high pressure stages of the compressor 20 so that liquefaction by decompression and cooling is achieved. can do.

The method of liquefying the boil-off gas as described above may depend on the operating state of the engine. In other words, the evaporation gas liquefaction line (L20) and the cooling bypass line (L21), the evaporation gas can be made to be liquefied by reduced pressure or liquefied by reduced pressure & cooling depending on the operating state of the engine.

For example, in relation to the operating state of the engine, the liquefied gas liquefaction line L20 and the cooling bypass line L21 of this embodiment, when the ship is anchored or sailed at a low speed (stop of the propulsion engine 100 and excess evaporation gas are generated) ) Evaporate gas to be liquefied by reduced pressure and cooling.

At this time, the evaporation gas between the low pressure stage and the high pressure stage may be introduced into the evaporation gas liquefaction line (L20), and the high pressure stage is upstream from downstream (3 stage downstream from 5 stage downstream or 4/3 stage downstream from 5/4 stage downstream, etc.) ) It is possible to suppress the flow of the evaporation gas to the propulsion engine 100 by continuously circulating the evaporation gas through a line connected to.

Alternatively, the boil-off gas may be introduced into the boil-off gas liquefaction line (L20) downstream of the high-pressure stage, and when the propulsion engine 100 having a required pressure of 100 bar or more is in operation, the pressure at which the boil-off gas downstream of the high-pressure stage is liquefied only by reducing the pressure However, when the propulsion engine 100 is stopped, the pressure of the evaporation gas downstream of the high-pressure stage may not reach the required pressure of the propulsion engine 100 through unloading control, etc. have.

Therefore, when the propulsion engine 100 is not in operation, the boil-off gas may be introduced into the boil-off gas liquefaction line (L20) between the low-pressure stage and the high-pressure stage, or downstream of the high-pressure stage, but commonly, in addition to the reduced pressure, liquefaction is achieved through cooling of the refrigerant. Can be.

Of course, when the propulsion engine 100 is stopped, it is also possible for the compressor 20 to still implement high-pressure discharge, so it is possible to implement liquefaction only by reducing pressure. In other words, the present invention can be liquefied by cooling + depressurizing the liquefied gas generated in the liquefied gas storage tank 10 at the time of anchoring or low-speed sailing, or only by depressurizing.

On the other hand, as the propulsion engine 100 is operated when the ship is at medium speed (above the first ship speed), the pressure of the evaporation gas downstream of the high pressure stage can be a pressure that can be liquefied only by decompression, and at this time, the evaporation gas liquefaction line (L20) and cooling Bypass line (L21) can be made to liquefy the boil-off gas only by decompression.

Alternatively, when the ship is sailing at a high speed (above the second ship speed), as the load of the propulsion engine 100 increases, the evaporation gas discharged from the liquefied gas storage tank 10 is consumed by the propulsion engine 100 or the like, and thus surplus evaporation gas Since may not occur, the flow of the liquefied gas liquefaction line (L20) may be blocked.

As described above, in the present exemplary embodiment, it is possible to control whether the cooling unit 50 is bypassed according to a point at which the boil-off gas diverges from the compression stage 21 of the compressor 20 toward the pressure-reducing valve 40, and the engine operates. Depending on the ship operation status, the liquefaction rate and system operation efficiency can be improved by allowing the evaporation gas to be liquefied only through partial reliquefaction or partial reliquefaction and complete reliquefaction.

The gas-liquid separator 60 separates the evaporated gas that has been cooled by the refrigerant or decompressed by gas-liquid to deliver the liquid to the liquefied gas storage tank 10. The liquefied gas liquefaction line (L20) is connected to the liquefied gas storage tank (10) through the evaporative gas heat exchanger (30), the cooling unit (50), the pressure reducing valve (40), and the gas-liquid separator (60) at the compression stage (21). In this case, the evaporation gas may be present in the liquid phase downstream of the gas-liquid separator 60 in the evaporation gas liquefaction line L20.

However, in order to prepare for the case where the gas phase remains downstream of the gas-liquid separator 60, the end of the evaporation gas liquefaction line L20 is connected to the inside of the liquefied gas storage tank 10, and liquefied evaporation gas is injected into the liquefied gas. It is possible to make the remaining gas phase liquefied by liquefied gas.

The flash gas separated from the gas-liquid separator 60 may be discharged through the gaseous discharge line L60. The gaseous phase discharge line L60 is connected to the upstream of the compressor 20 (upstream of the evaporation gas heat exchanger 30) from the evaporation gas supply line L10, so that the gas phase is mixed with the evaporated gas supplied to the compressor 20. have.

In the gas-liquid separator 60, a pressurizing line L23 may be provided. The pressurizing line (L23) allows the boil-off gas compressed by at least one stage of the compressor (20) to bypass the cooling unit (50) and the pressure reducing valve (40) and flow into the gas-liquid separator (60).

Compared to the case where the evaporation gas is liquefied only under reduced pressure, when the refrigerant gas is liquefied by combining the refrigerant cooling with the reduced pressure, the evaporation gas may be sub-cooled beyond the level at which it is liquefied.

In this case, the supercooled evaporation gas flowing into the gas-liquid separator 60 can also liquefy the boil-off gas that may exist inside the gas-liquid separator 60, thereby lowering the pressure inside the gas-liquid separator 60. Therefore, it is difficult to control the internal pressure of the gas-liquid separator 60, and at the same time, the liquid vaporized gas may not be smoothly returned from the gas-liquid separator 60 to the liquefied gas storage tank 10.

In order to solve this, the present embodiment can prevent the excessive pressure drop of the gas-liquid separator 60 by forcibly injecting the vaporized gas before being liquefied into the gas-liquid separator 60. At this time, the pressurization line (L23) may be branched at at least one point upstream or downstream of the evaporation gas heat exchanger (30) in the evaporation gas liquefaction line (L20) to be connected to the gas-liquid separator (60).

The pressurization line L23 may transfer the boil-off gas compressed by at least one stage of the compressor 20 to the gas-liquid separator 60 when the over-cooling concern occurs as the boil-off gas passes through the cooling unit 50. The flow control of the pressure line L23 may also be achieved by a valve (not shown) provided in the pressure line L23, and the control unit may be used as described above.

Therefore, this embodiment can solve the problem of lowering the internal pressure of the gas-liquid separator 60 when the hybrid re-liquefaction combining the reduced pressure and the refrigerant cooling, it is possible to ensure a smooth return of the liquid vaporized gas.

In the liquefied gas liquefaction line L20, a gas-liquid separation bypass line L22 bypassing the gas-liquid separator 60 may be provided. The gas-liquid separation bypass line L22 may be branched upstream of the gas-liquid separator 60 from the evaporative gas liquefaction line L20 and connected to the downstream of the gas-liquid separator 60, the engine is in operation, the evaporation gas liquefaction line (L20) Depending on variables such as the flow rate of the evaporation gas, the evaporation gas can be directly delivered to the liquefied gas storage tank 10 by bypassing the gas-liquid separator 60 downstream of the pressure reducing valve 40.

For example, when the engine load is large and the excess evaporation gas does not generate much, since the evaporation gas is sufficiently liquefied, separation of the gas phase may become unnecessary, and the gas-liquid separation bypass line L22 may be utilized.

Also, as described above, when the gas-liquid separation bypass line L22 is used even when the evaporation gas is supercooled, the supercooled evaporation gas is liquefied gas without the need to inject the evaporation gas through the pressurization line L23 into the gas-liquid separator 60. As it enters the storage tank 10, the effect of suppressing the generation of evaporation gas in the liquefied gas storage tank 10 may be achieved.

As described above, when the evaporation gas flows along the gas-liquid separation bypass line L22, the gaseous discharge through the gaseous discharge line L60 may be omitted or minimized.

2 is a conceptual diagram of a gas processing system according to a second embodiment of the present invention.

Referring to Figure 2, the gas treatment system 1 according to the second embodiment of the present invention, the propulsion engine 100 and the compressor 20 may be different from the previous embodiment. Hereinafter, the present embodiment will be mainly described in terms of differences from other embodiments, and parts omitted from description will be replaced with the previous contents. This also applies to other examples below.

In this embodiment, the required pressure of the propulsion engine 100 may be a pressure (less than 100 bar) in which liquefaction is not sufficient by reducing pressure alone. Here, the propulsion engine 100 may be an X-DF engine or the like having a required pressure of less than 100 bar.

On the other hand, in the present embodiment, the compressor 20, unlike the final stage discharge pressure of the compressor 20 of the previous embodiment corresponds to the required pressure of the engine, the final stage is the required pressure of the engine more than the required pressure of the engine (100 bar or more) It can be pressurized.

That is, the compressor 20 of the present embodiment is provided so that the discharge pressure at the final stage exceeds the required pressure of the engine, but it is possible to supply the evaporation gas to the engine from the intermediate stage rather than the final stage for the operation of the engine.

At this time, the boil-off gas liquefaction line (L20), so that the boil-off gas of the middle stage downstream and the final stage downstream of the compressor 20 is delivered to the liquefied gas storage tank 10 via the pressure reducing valve 40 and the cooling unit 50 It can be, unlike in the previous embodiment, the evaporation gas liquefaction line (L20) downstream of the final stage is branched from the evaporation gas supply line (L10), in this embodiment, the evaporation gas liquefaction line from the evaporation gas supply line (L10) The point at which L20) is branched may be the middle end downstream (which may be between the low end and the high end as the high end). At this time, the high pressure stage of the compressor 20 may be placed on the evaporation gas liquefaction line L20.

In this embodiment, as in the previous embodiment, depending on the ship's operating conditions, the evaporated gas can be liquefied by reduced pressure or liquefied by reduced pressure & cooling. However, in the present embodiment, when the evaporation gas downstream of the middle stage in the anchoring state flows into the evaporation gas liquefaction line L20 for cooling and decompression, and when excess evaporation gas does not occur in the high-speed navigation state, the compressor 20 ), at least a high pressure stage after the middle stage may be idle.

At this time, stir means that the evaporation gas is not compressed, and unloading control and upstream return control may be performed together. In other words, in the high pressure stage of the shed, the evaporated gas can simply flow without compression.

As described above, this embodiment uses a low-pressure two-stroke heterogeneous fuel engine as the propulsion engine 100, so that the final discharge pressure of the multi-stage compressor 20 operating as a single driving source exceeds the required pressure of the propulsion engine 100. . Therefore, in the present embodiment, in addition to liquefaction by decompression and cooling, liquefaction through only decompression is possible by utilizing the high pressure stage of the compressor 20, thereby enabling effective liquefaction operation.

3 is a conceptual diagram of a gas processing system according to a third embodiment of the present invention.

Referring to Figure 3, the gas treatment system 1 according to the third embodiment of the present invention, unlike the previous embodiment in which the evaporation gas is reduced and cooled along the evaporation gas liquefaction line (L20), the evaporation gas is reduced pressure By being liquefied and introduced into the gas-liquid separator 60, the gas phase separated from the gas-liquid separator 60 can be cooled with a refrigerant.

That is, the cooling unit 50 of the present embodiment may cool the gas phase separated from the gas-liquid separator 60 with a refrigerant and transfer it to the liquefied gas storage tank 10. Therefore, since the evaporation gas compressed in the compressor 20 is liquefied by depressurization, and the flash gas, which is a gaseous phase remaining unliquefied, is liquefied by cooling of the cooling unit 50, in this embodiment, the load of the cooling unit 50 is Will decrease.

However, in order to liquefy the boil-off gas only under reduced pressure, the boil-off gas liquefaction line (L20) can be connected to the gas-liquid separator (60) by extending from the compressor (20) downstream of the compression stage (21) of 100 bar or more via the pressure-reducing valve (40). have.

If an ME-GI engine is used as an example, the evaporation gas liquefaction line L20 when the compressor 20 is in the 5th stage may be extended downstream in the 3rd stage, and the evaporation gas liquefaction line L20 when the compressor 20 is the 6th stage. Can be extended downstream of the fifth stage.

On the other hand, if the X-DF engine is used, the number of compression stages 21 may be different compared to the case of using the ME-GI engine, and compression provided downstream of the point where the evaporation gas supply line L10 branches to the power generation engine 110 Column 21 may be omitted.

However, in order to implement liquefaction by reducing the pressure, the discharge pressure of the compressor 20 is 100 bar or more that exceeds the required pressure of the propulsion engine 100 or meets the required pressure of the propulsion engine 100 as described in the first embodiment. Variable control may be possible.

The gaseous discharge line L60 extending from the gas-liquid separator 60 can transmit the gaseous phase separated from the gas-liquid separator 60 to the liquefied gas storage tank 10 via the cooling unit 50, to completely liquefy the gaseous phase. To this end, the gaseous gas discharge line L60 is connected to the lower side of the liquefied gas storage tank 10 so that the gaseous phase cooled in the cooling part 50 is injected into the liquefied gas.

At least one gas-liquid separation bypass line L22 may be provided in the evaporation gas liquefaction line L20. Any one of the gas-liquid separation bypass line (L22) is as described in the previous embodiment, the other gas-liquid separation bypass line (L22) is added in this drawing, branched upstream of the gas-liquid separator 60 to vapor phase It is connected to the discharge line (L60). In the latter gas-liquid separation bypass line L22, in contrast to the former, when the liquefaction of the evaporation gas is not sufficient, the flow of the evaporation gas may be made.

As an example, the latter gas-liquid separation bypass line L22 bypasses the gas-liquid separator 60 downstream of the pressure-reducing valve 40 according to the operating state of the engine, the evaporative gas flow rate of the evaporative gas liquefaction line L20, and the like. It can be made to flow into the cooling unit 50.

That is, when the engine load is small and there is a large amount of excess evaporation gas, when the liquid separation in the gas-liquid separator 60 is not large and overall cooling is required by the cooling unit 50, the flow in the latter gas-liquid separation bypass line L22 This can be done.

However, if the present embodiment uses the latter gas-liquid separation bypass line L22, it may be similar to the case where the evaporated gas is liquefied by decompression & cooling in the first embodiment in terms of liquefied evaporated gas. Of course, it is also possible that the gas-liquid separator 60 itself is omitted, which is shown in other drawings below.

As described above, this embodiment implements liquefaction through a combination of the decompression valve 40 and the cooling unit 50, but is provided so that the cooling unit 50 liquefies only the gas phase that is separated from the gas-liquid after the decompression, and thus the cooling unit 50 ) Can be compacted.

4 is a conceptual diagram of a gas processing system according to a fourth embodiment of the present invention.

Referring to FIG. 4, in the gas treatment system 1 according to the fourth embodiment of the present invention, the liquefied gas liquefaction line L20 undergoes both refrigerant cooling and decompression. At this time, the liquefied gas liquefaction line (L20) may be extended from the middle stage of the compressor 20 when the propulsion engine 100 is high pressure, and may be extended from the final stage of the compressor 20 when the propulsion engine 100 is low pressure.

In addition, in the present embodiment, the gas-liquid separator 60 is omitted downstream of the pressure reducing valve 40, so that even when gas phase and liquid phase are mixed, all of the evaporation gas is introduced into the liquefied gas storage tank 10. At this time, the gas phase may be liquefied naturally while being injected into the liquefied gas.

In addition, in the present embodiment, a mixed refrigerant having light hydrocarbon as a main component is used as a refrigerant, and evaporation gas may be used to solve the problem of insufficient precooling when reducing/omitting heavy hydrocarbon.

In particular, in the present embodiment, the cooler cooler 53 may be provided to cool the coolant with evaporation gas. That is, the refrigerant cooler 53 can cool the refrigerant by using the evaporation gas of the liquefied gas storage tank 10 when the cooling unit 50 is initially operated, and for this purpose, the refrigerant cooler 53 is a refrigerant circulation line (L50) It may be provided with a stream in which the refrigerant flows in parallel and a stream in which the evaporation gas flows in parallel with the evaporation gas supply line (L10).

In the present invention, as described above, the cooling unit 50 uses a mixed refrigerant, but the specific gravity of heavy hydrocarbons in the mixed refrigerant may be reduced or omitted. Therefore, the cooling unit 50 of this embodiment can be provided to circulate one closed loop without separating the flow of the gas phase and the liquid phase, thereby simplifying the refrigerant circulation/supplement configuration.

In addition, this embodiment can minimize the refrigerant system, and utilize the cold energy of the evaporation gas to ensure that the precooling of the mixed refrigerant is sufficiently performed during the initial operation.

That is, unlike the existing mixed refrigerant system that sufficiently contains heavy hydrocarbons and liquid-phase heavy hydrocarbons cool gaseous light hydrocarbons at a temperature necessary for cooling the evaporated gas during heat exchange between refrigerants, this embodiment does not (almost) contain heavy hydrocarbons. Because precooling by liquid bicarbonate is not possible, it realizes precooling using the cold energy of the evaporation gas.

Therefore, in the present embodiment, even if the composition is changed so that the mixed refrigerant is light hydrocarbon as a main component, it is possible to secure sufficient liquefaction efficiency by pre-cooling when the cooling unit 50 is initially operated, while omitting facilities related to heavy hydrocarbons/ It can be reduced.

In addition, since the present invention uses a mixed refrigerant containing light hydrocarbon as a main component, similarly to the mixed refrigerant, the evaporation gas containing light hydrocarbon as a main component can be used for make-up of the refrigerant. To this end, the refrigerant replenishment line L11 may be connected to the refrigerant circulation line L50 or the refrigerant tank 55 from the evaporation gas supply line L10 or the evaporation gas liquefaction line L20.

However, the refrigerant replenishing line (L11) branched from the evaporation gas supply line (L10) can extend upstream of the refrigerant cooler (53) and has a relatively low pressure, so that the refrigerant compressor (52) upstream of the refrigerant compressor (52) To deliver the evaporated gas.

On the other hand, since the refrigerant replenishing line (L11) branched from the liquefied gas liquefaction line (L20) can extend upstream of the pressure reducing valve (40) and has a relatively high pressure, the refrigerant compressor (52) in the refrigerant circulation line (L50) Evaporation gas can be delivered downstream.

As described above, in the present exemplary embodiment, while the mixed refrigerant does not (almost) contain heavy hydrogen unlike the conventional case, it is possible to omit the heavy hydrocarbon supplementation equipment, etc. It can be implemented stably.

5 is a conceptual diagram of a gas processing system according to a fifth embodiment of the present invention.

Referring to FIG. 5, the gas treatment system 1 according to the fifth embodiment of the present invention, instead of the refrigerant cooler 53 being directly connected to the evaporation gas supply line L10 when compared with the previous fourth embodiment, It may be connected to the refrigerant cooling line (L12) branched from the evaporation gas supply line (L10).

In this embodiment, as in the fourth embodiment, the refrigerant cooler 53 cools the refrigerant compressed by the refrigerant compressor 52 with evaporation gas. However, in the case of the fourth embodiment, even if it is out of initial operation, the refrigerant exchanges heat with the evaporation gas, whereas in the present embodiment, pre-cooling using the evaporation gas can be avoided when it enters normal operation after the initial operation.

To this end, the evaporation gas supply line (L10) is partially provided in parallel, and a refrigerant cooling line (L12) via a refrigerant cooler (53) is provided. The refrigerant cooling line (L12) implements pre-cooling by allowing the evaporation gas to pass through the refrigerant cooler (53) during the initial operation of the cooling unit (50), and when the cooling unit (50) operates normally, the evaporation gas is the refrigerant cooler (53). ) Can be bypassed.

Here, the refrigerant cooling line (L12) is to utilize the low-temperature evaporation gas discharged from the liquefied gas storage tank (10), so that the evaporation gas supply line (L10) branches and joins upstream of the evaporation gas heat exchanger (30) It can be provided.

In addition, in the present embodiment, the refrigerant replenishment line L11 is provided as in the fourth embodiment, and the refrigerant replenishment line L11 is branched upstream of the evaporation gas heat exchanger 30 in the evaporation gas supply line L10 and the refrigerant is refrigerated. Refrigerant circulation line (L50) connected to the upstream of the refrigerant compressor (52) in the circulation line (L50), or branched upstream of the evaporation gas heat exchanger (30) in the liquefied gas liquefaction line (L20) and upstream of the pressure reducing valve (40) ) May be connected downstream of the refrigerant compressor 52.

As described above, the present embodiment implements precooling with evaporation gas while using a mixed hydrocarbon-based refrigerant, and when it is out of the initial operation, allows evaporation gas to bypass heat exchange with the mixed refrigerant, thereby controlling optimal operation according to the situation. Is possible.

6 is a conceptual diagram of a gas processing system according to a sixth embodiment of the present invention.

Referring to FIG. 6, in the gas treatment system 1 according to the sixth embodiment of the present invention, a gas-liquid separator 60 may be added as compared to the fifth embodiment, and gas phase separated from the gas-liquid separator 60 is mixed. It can be used for precooling of refrigerant.

In the initial operation that requires precooling of the mixed refrigerant, a large amount of flash gas is generated even though heat exchange between the refrigerant and the evaporation gas does not sufficiently liquefy the evaporation gas.

However, since the flash gas is cooled to a considerable low temperature even in the gas phase, the present embodiment can implement precooling of the refrigerant by using the low temperature flash gas.

To this end, the gas-liquid separator 60 may be provided with a gaseous discharge line L60 that transfers the gas phase separated from the gas-liquid separator 60 to the upstream of the refrigerant cooler 53 from the refrigerant cooling line L12. Therefore, the gas phase separated from the gas-liquid separator 60 may precool the mixed refrigerant during the initial operation of the cooling unit 50.

Of course, in the case of entering normal operation, the flow in the refrigerant cooling line L12 may be reversed so that the gas phase separated from the gas-liquid separator 60 does not exchange heat with the refrigerant.

As described above, in the present embodiment, the precooling time can be shortened by utilizing flash gas generated in a large amount during initial operation for pre-cooling the mixed refrigerant.

7 is a conceptual diagram of a gas processing system according to a seventh embodiment of the present invention.

Referring to FIG. 7, in the gas treatment system 1 according to the seventh embodiment of the present invention, the gaseous discharge line L60 is compared to the previous sixth embodiment through the evaporative gas heat exchanger 30 and the evaporated gas supply line ( L10) may be connected upstream of the compressor 20.

At this time, the evaporation gas heat exchanger 30 has a first stream parallel to the evaporation gas supply line L10, a second stream parallel to the evaporation gas liquefaction line L20, and a third stream parallel to the gaseous emission line L60. It can have a structure that is arranged independently.

That is, in the present embodiment, precooling of the mixed refrigerant containing light hydrocarbon as a main component utilizes evaporation gas, and the gas phase separated from the gas-liquid separator 60 flows along the evaporation gas liquefaction line L20 in the evaporation gas heat exchanger 30. It can be used to pre-cool the evaporated gas.

Of course, the gaseous discharge line L60 of this embodiment may be branched to the refrigerant cooling line L12, and when the cooling unit 50 is initially operated, flash gas flows into the refrigerant cooling line L12, and the cooling unit 50 ) During normal operation, the flash gas may be delivered to the evaporation gas supply line (L10) through the evaporation gas heat exchanger (30).

In addition to the above-described embodiments, the present invention encompasses all of the embodiments generated by a combination of the above embodiments and known techniques.

The present invention has been described in detail through specific examples, but this is for specifically describing the present invention, and the present invention is not limited to this, and by a person skilled in the art within the technical spirit of the present invention. It will be apparent that the modification or improvement is possible.

All simple modifications or changes of the present invention belong to the scope of the present invention, and the specific protection scope of the present invention will be clarified by the appended claims.

1: Gas treatment system 10: Liquefied gas storage tank
L10: Evaporation gas supply line L11: Refrigerant supplement line
L12: refrigerant cooling line 20: compressor
21: compression stage L20: evaporation gas liquefaction line
L21: Cooling bypass line L22: Gas-liquid separation bypass line
L23: Pressurized line 30: Evaporative gas heat exchanger
L30: Evaporation gas bypass line 40: Pressure reducing valve
50: cooling unit 51: cooler
52: refrigerant compressor 53: refrigerant cooler
54: refrigerant valve 55: refrigerant tank
L50: refrigerant circulation line 60: gas-liquid separator
L60: Meteorological emission line 100: Propulsion engine
101: pressure control valve 110: power generation engine

Claims (8)

Liquefied gas storage tank;
Compressor composed of multiple stages operated by one driving source and compressing evaporation gas generated in the liquefied gas storage tank to supply to the engine;
A pressure reducing valve for reducing at least a portion of the boil-off gas compressed by at least one stage of the compressor;
A cooling unit provided in series with the pressure reducing valve based on the flow of the evaporating gas and cooling the evaporating gas with a refrigerant;
An evaporation gas liquefaction line allowing at least two points of evaporation gas to be delivered to the liquefied gas storage tank via the pressure reducing valve and the cooling unit downstream of the first stage of the compressor; And
It is provided in the liquefied gas liquefied line and includes a cooling bypass line that allows the boiled gas to bypass the cooling unit,
The cooling bypass line, the gas processing system characterized in that the flow of the evaporation gas is adjusted according to the point at which the evaporation gas flows into the evaporation gas liquefaction line. According to claim 1,
The compressor includes a low pressure stage and a high pressure stage, which are operated by one driving source and have different mixing modes of lubricating oil in the evaporation gas,
The pressure reducing valve, the gas processing system, characterized in that to decompress at least a portion of the boil-off gas compressed by at least the low-pressure stage of the compressor. According to claim 2,
The engine is a propulsion engine having a required pressure of 200 bar or more,
The low pressure stage of the compressor pressurizes the evaporated gas to less than 100 bar,
The boil-off gas liquefaction line, the gas processing system characterized in that it is provided to extend after the high-pressure stage downstream of the compressor and the low-pressure stage and the high-pressure stage of the compressor to be joined and passed through the pressure reducing valve and the cooling unit. According to claim 3, The evaporation gas liquefaction line and the cooling bypass line,
Evaporation gas is passed through the pressure reducing valve from the downstream of the high pressure stage of the compressor to bypass the cooling portion so that liquefaction by decompression is performed, or evaporation gas is provided between the low pressure stage and the high pressure stage of the compressor to reduce the pressure reducing valve and the cooling portion. Gas treatment system characterized in that the liquefied by the reduced pressure and cooling to be made through. The method of claim 4, wherein the evaporation gas liquefaction line and the cooling bypass line,
Gas processing system characterized in that the evaporation gas is liquefied by reduced pressure or liquefied by reduced pressure and cooling according to the operating state of the engine. The method of claim 4, wherein the evaporation gas liquefaction line and the cooling bypass line,
When the ship is anchored and sailed at low speed, the evaporated gas is liquefied by decompression and cooling,
When the vessel is sailing at medium speed, the evaporated gas is liquefied by decompression,
A gas processing system characterized in that the flow of the liquefied gas liquefaction line is blocked when the ship is sailing at high speed. According to claim 1,
A gas processing system further comprising a gas-liquid separator for gas-liquid separation of the evaporated gas that has undergone cooling or decompression by a refrigerant to deliver a liquid to the liquefied gas storage tank. A ship characterized by having the gas treatment system according to any one of claims 1 to 7.

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