KR20200012673A - Boil-off gas cooling system and ship having the same - Google Patents

Abstract

The present invention relates to a boil off gas cooling system and a ship. The boil off gas cooling system includes: a compressor compressing boil off gas generated in a liquefied gas storage tank; a precooler cooling the boil off gas at an upstream portion of the compressor; a liquefier liquefying the compressed boil off gas; and a vapor-liquid separator separating vapor and liquid of the liquefied boil off gas, wherein the precooler is configured to cool the boil off gas by using the liquid boil off gas separated from the vapor-liquid separator.

Description

Boil-off gas cooling system and ship having the same

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

Liquefied gas carriers that carry liquefied gases, such as Liquefied Natural Gas or Liquefied Petroleum Gas, are those that have a boiling point below room temperature. Is forcibly liquefied and stored in a liquid tank.

Liquefied natural gas is liquefied by cooling methane (CH4) obtained by refining natural gas collected from a gas field. It is a colorless and transparent liquid. Liquefied petroleum gas, on the other hand, is a liquid made of gas containing propane (C3H8) and butane (C4H10), which come with petroleum from oil fields, and is widely used as a fuel for household, business, industrial, and automobiles. Liquefied natural gas is reduced to a volume of 1/600 by liquefaction, liquefied petroleum gas has the advantage of high storage efficiency by reducing the volume of propane is 1/260, butane is 1/230 by liquefaction.

By the way, the storage tank for storing the liquefied gas is implemented a heat insulation function, but can not completely block the vaporization of the liquefied gas. Therefore, in the storage tank, a gaseous evaporation gas generated by the liquefied gas evaporates, and the evaporated gas increases the internal pressure of the storage tank, so it must be discharged from the storage tank for safety.

In order to lower the internal pressure of the storage tank, the evaporated gas discharged from the storage tank is combusted and discarded by a gas combustion unit. By the way, the boil-off gas also corresponds to some of the cargo carried by the ship, the emission of the boil-off gas is a problem because it reduces the reliability of the cargo transportation.

Therefore, in recent years, continuous research and development has been made on a method for effectively treating the boil-off gas generated in the storage tank without discarding it.

The present invention was created to solve the problems of the prior art as described above, an object of the present invention, while pre-cooling the evaporated gas before compression to improve the efficiency of the compressor, smoothly without the compressed gas, such as nitrogen, droplets generated during pre-cooling It is to provide an evaporative gas cooling system that can be returned to the tank and a vessel comprising the same.

It is also an object of the present invention to provide an evaporation gas cooling system and a vessel comprising the same, by pre-cooling the evaporation gas with liquefied evaporation gas instead of liquefied gas, so that the generation of droplets during the pre-cooling is minimized. It is for.

In addition, an object of the present invention, by using the liquefied gas supplied to the engine, etc. to cool the evaporated gas and then compressed, so that the compressor can give a higher pressure by reducing the power consumption required for liquefied evaporation gas cooling system And to provide a vessel comprising the same.

In addition, an object of the present invention, while implementing a backup structure using three compressors having the same / similar head, at least one compressor to lower the design pressure, thereby reducing the compressor installation cost and increase the operating efficiency And to provide a vessel comprising the same.

Evaporation gas cooling system according to an aspect of the present invention, the compressor for compressing the boil off gas generated in the liquefied gas storage tank; A precooler for cooling the boil-off gas upstream of the compressor; A liquefier for liquefying the compressed boil-off gas; And a gas-liquid separator for gas-liquid separation of the liquefied boil-off gas, wherein the precooler is configured to cool the boil-off gas by using a liquid vaporized gas separated from the gas-liquid separator.

Specifically, the separator may further include a separator separating the liquid between the precooler and the compressor.

Specifically, the separator may be provided to store the liquid without discharging it.

Specifically, an liquefied gas liquefaction line connected to the gas-liquid separator via the precooler, the separator, the compressor and the liquefier in the liquefied gas storage tank; A liquid return line connected to the liquefied gas storage tank in the gas-liquid separator; And a liquid delivery line branched from the liquid return line and connected to the precooler.

Specifically, the precooler may cool the boil-off gas by using a liquid boil-off gas having no or little ratio of heavy carbon in place of the liquefied gas.

Ship according to one aspect of the invention, characterized in that having the boil-off gas cooling system.

Evaporative gas cooling system according to the present invention and a vessel including the same, pre-cooling the boil-off gas before compression to increase the pressure, while not returning the liquid generated during the pre-cooling to the tank to avoid the need for a separate nitrogen supply system Can be simplified.

In addition, the boil-off gas cooling system according to the present invention and the vessel including the same, in place of the liquefied gas containing a large amount of heavy carbon, by using the liquefied boil-off gas mainly containing a component having a very low boiling point, such as methane or nitrogen, By pre-cooling, there is little generation of droplets during pre-cooling to omit the relevant configuration.

In addition, the evaporation gas cooling system according to the present invention and a vessel including the same, by cooling the evaporated gas flowing into the compressor by using the liquefied gas and liquefied evaporated gas supplied to the engine, even after using the compressor of the same specifications Increasing the pressure at can improve the power consumption and reliquefaction rate.

In addition, the boil-off gas cooling system according to the present invention and the ship including the same, can cover all the amount of boil-off gas, while using the same head three compressors can be implemented to back up each other, it is possible to reduce the installation cost of the compressor .

1 is a conceptual diagram of an evaporative gas cooling system according to a first embodiment of the present invention.
2 is a conceptual diagram of an evaporative gas cooling system according to a second embodiment of the present invention.
3 is a conceptual diagram of an evaporative gas cooling system according to a third embodiment of the present invention.
4 is a conceptual diagram of an evaporative gas cooling system according to a fourth embodiment of the present invention.
5 is a conceptual diagram of an evaporative gas cooling system according to a fifth embodiment of the present invention.
6 is a conceptual diagram of an evaporative gas cooling system according to a sixth embodiment of the present invention.
7 is a conceptual diagram of an evaporative gas cooling 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 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. Hereinafter, in the present specification, the gas may be used to encompass all substances vaporized in a gaseous state at room temperature, such as LNG or LPG, ethylene, ethane, ammonia, etc. Hereinafter, in the present specification, liquefied gas includes methane, propane, butane, etc. for convenience. It is assumed that it contains LNG.

In addition, liquefied gas means a gas liquefied for storage, evaporated gas means a natural vaporized gas, and the state of liquefied gas or evaporated gas is not limited to liquid and gas, respectively. For reference, liquefied gas contains heavy carbon such as propane and butane, while natural vaporized evaporated gas has (almost) no heavy carbon and mainly contains methane.

In addition, liquefaction in the following does not mean only the case of completely reliquefaction, but can be used as a meaning encompassing at least some intended liquefaction cooling, it is noted that the high pressure and low pressure is a relative meaning, not an absolute value.

The present invention includes a vessel having an evaporative gas cooling system described below, wherein the vessel encompasses all commercial vessels having no type limitation, such as container ships or bulk carriers, in addition to gas ships carrying liquefied gas. Furthermore, in the present specification, a vessel may be used to encompass a marine plant fixed or floating in the ocean in addition to the general merchant vessel.

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

Referring to FIG. 1, the boil-off gas cooling system 1 according to the first embodiment of the present invention includes a liquefied gas storage tank 10, a compressor 20, a precooler 30, a separator 40, and a liquefier. 50, gas-liquid separator 60.

The liquefied gas storage tank 10 stores liquefied gas. The liquefied gas storage tank 10 is not limited to its type, such as a stand-alone type, a membrane type, a pressure vessel type, and the like, and an installation position in a ship is not particularly limited.

For example, when the vessel is a gas line, the liquefied gas storage tank 10 may be a cargo tank provided in plural in the ship in the longitudinal direction, and when the vessel is another ship type such as a container ship other than a ship that transports liquefied gas, the deck It may be a pressure vessel disposed above the bow or stern.

The liquefied gas storage tank 10 may implement heat insulation to store the liquefied gas in the liquid phase, and / or increase the storage pressure to prevent vaporization of the liquefied gas.

The boil-off gas generated in the liquefied gas storage tank 10 may be discharged to the outside because the internal pressure of the liquefied gas storage tank 10 rises, and the boil-off gas discharged to the outside is liquefied to be described later, The liquid 50 may be cooled / liquefied and returned to the liquefied gas storage tank 10 or consumed at the demand destination 100.

For reference, the demand source 100 for consuming boil-off or liquefied gas in the present specification may be a propulsion engine for propelling a ship, a power generation engine generating power required in a ship, and / or a turbine, a boiler other than an engine. The gas combustion device (GCU), the fuel cell and the like are not limited in kind.

The compressor 20 compresses the boil-off gas generated in the liquefied gas storage tank 10. The boil-off gas discharged from the liquefied gas storage tank 10 may be around 1 bar corresponding to the internal pressure of the liquefied gas storage tank 10, and the present specification uses the compressor 20 to increase the boiling point of the boil-off gas. Can be compressed.

The compressor 20 is not limited to the type of centrifugal type, reciprocating type, and the like, and may be provided in one stage or two or more stages in series. Of course, a plurality of compressors 20 may be provided in parallel, and in this case, backup may be possible.

In the liquefied gas storage tank 10, the liquefier 50 to be described later via the compressor 20 may be provided with an liquefied gas liquefied line (L1), the liquefied gas liquefied line (L1) is downstream of the liquefier (50) Up to gas-liquid separator 60 may be connected. In the boil-off gas liquefaction line L1, the boil-off gas supply line L6 may branch to the demand destination 100, and the branch point of the boil-off gas supply line L6 may be between the compressor 20 and the liquefier 50. But it is not limited to this.

The precooler 30 cools the boil-off gas upstream of the compressor 20. The precooler 30 may cool the boil-off gas by using various materials such as boil-off gas, liquefied gas, air, sea water, separate refrigerant, and heat-exchange with boil-off gas or mix the material with the boil-off gas to cool the boil-off gas. Can be implemented.

However, hereinafter, the precooler 30 mixes the substance with the boil-off gas to cool the boil-off gas, and the substance is limited to the liquefied boil-off gas. Of course, the type of precooler 30 or the material used in the precooler 30 may vary as described above.

The precooler 30 may implement precooling by mixing the liquefied gas with the evaporated gas instead of the liquefied gas with the evaporated gas discharged from the liquefied gas storage tank 10.

At this time, since the precooler 30 uses no liquid carbon or a small amount of liquid evaporated gas in place of the liquefied gas, there is no (nearly) heavy carbon inside the precooler 30. Therefore, despite the precooling, the material to be introduced into the compressor 20 may be almost in a gaseous state, which will be described later with reference to FIG. 4.

The precooler 30 has a space for storing the boil-off gas supplied from the liquefied gas storage tank 10, and can be mixed in the form of spraying the liquefied boil-off gas into the interior of the space, referred to as a mixer (mixer) Can be.

It is known in the art of the compressor 20 that if the temperature of the fluid entering the same type centrifugal compressor 20 is low, a higher pressure can be produced. In consideration of this characteristic of the compressor 20, the present invention can further increase the discharge pressure of the compressor 20 under the same specifications by cooling the boil-off gas using the precooler 30 and introducing the same into the compressor 20. .

When the discharge pressure of the compressor 20 rises, the boiling point of the boil-off gas rises, so that the liquefaction efficiency in the liquefier 50 may increase. Therefore, the present invention can achieve the effect of increasing the liquefaction rate and power consumption through pre-cooling upstream of the compressor (20). However, at this time, the compressor 20 may be a cryogenic compressor 20.

The separator 40 separates liquid between the precooler 30 and the compressor 20. Although it may vary depending on the type of compressor 20, it is not desirable for droplets to enter the compressor 20 to operate the compressor 20.

Therefore, the separator 40 may separate the liquid contained in the boil-off gas in front of the compressor 20 and allow only the gas to flow into the compressor 20. In this case, the liquid separated from the separator 40 may be methane or heavy carbon such as propane and butane.

However, as described above, since the material mixed in the precooler 30 may be a liquefied boil-off gas, the liquid separated from the separator 40 may be a small amount of methane and the heavy carbon flows into the separator 40. It may not be.

Since the liquid separated from the separator 40 is a material having energy, it is necessary to collect for recycling. Therefore, the liquid of the separator 40 may be returned to the liquefied gas storage tank 10 via the chamber 411, the pressure vessel 412.

In this case, nitrogen may be blown for a smooth return flow of the liquid, but in this case, a pipe for injecting nitrogen is required, and when additional pipes are added, thermal penetration due to the pipes hinders the operation of the system.

Therefore, the present invention includes a liquid return unit 41 so that the liquid separated from the separator 40 can be smoothly returned to the liquefied gas storage tank 10 without the injection of pressurized fluid such as nitrogen.

The liquid return unit 41 returns the liquid separated from the separator 40 to the liquefied gas storage tank 10, and includes a chamber 411, a pressure vessel 412, and a valve unit 413. In 40, a liquid discharge line L2 drained to the pressure vessel 412 via the chamber 411 is provided.

The chamber 411 receives the liquid of the separator 40. The chamber 411 may be installed at a position lower than the separator 40 so as to smoothly receive the liquid from the separator 40. At this time, the liquid can be delivered by gravity.

The chamber 411 may be provided with a first pressure control line L30 connected to the separator 40, and the first pressure control line L30 may be provided separately from the liquid discharge line L2. As will be described later, the first pressure control line L30 is for preventing the back flow of the liquid from the chamber 411 to the separator 40.

The pressure vessel 412 is provided downstream of the chamber 411. The pressure vessel 412 may be installed at a position lower than the separator 40, particularly at a position lower than the chamber 411, so that the liquid may be delivered from the chamber 411 by gravity.

The pressure vessel 412 is configured to increase the pressure of the chamber 411. To this end, a second pressure regulating line L31 may be provided between the pressure vessel 412 and the chamber 411, and the second pressure regulating line L31 may be provided with a liquid discharge line like the first pressure regulating line L30. It is provided separately from (L2).

In addition to the liquid, the boil-off gas may be introduced into the pressure vessel 412. For example, the boil-off gas compressed in the compressor 20 may be introduced into the pressure vessel 412. Therefore, the pressure vessel 412 may have an internal pressure for boosting the chamber 411.

Of course, since the pressure vessel 412 may maintain a state in which the pressure increases as the liquid accumulates, the configuration in which the boil-off gas flows into the pressure vessel 412 may be omitted.

The liquid return line L4 may be connected to the pressure vessel 412 by the liquefied gas storage tank 10. Therefore, the liquid separated from the separator 40 is stored in the liquefied gas via the chamber 411 and the pressure vessel 412. Return to the tank 10.

The valve unit 413 may adjust the pressure between the separator 40, the chamber 411, and the pressure vessel 412 so that the liquid can be smoothly returned without a separate pressurized fluid. To this end, the valve unit 413 includes a first discharge valve 413a, a second discharge valve 413b, and a first pressure control line L30 provided upstream and downstream of the chamber 411 in the liquid discharge line L2, respectively. ) And a first pressure control valve 413c and a second pressure control valve 413d respectively provided in the second pressure control line L31.

Of course, the valve unit 413 may include a combination of valves different from the above, provided that the liquid flow up and down the chamber 411 and the flow of the first and second pressure regulating lines L30 and L31 can be controlled.

When the liquid is separated from the separator 40, the valve 413 allows the liquid to flow into the chamber 411 from the separator 40 while blocking the flow from the chamber 411 to the pressure vessel 412. To this end, the valve unit 413 closes the second discharge valve 413b and the second pressure control valve 413d and opens the first discharge valve 413a and the first pressure control valve 413c.

However, since the liquid present in the chamber 411 may flow back to the separator 40 when the first discharge valve 413a is opened, the first discharge valve 413a may be opened after the first pressure control valve 413c is opened. Can be done on.

When the state of the valve unit 413 as described above is maintained by the gravity from the separator 40 to the chamber 411, when the level of the liquid flowing into the chamber 411 exceeds the predetermined value, the valve unit 413 may open the flow from chamber 411 to pressure vessel 412.

Specifically, the valve unit 413 closes the first discharge valve 413a and the first pressure regulating valve 413c, and opens the second discharge valve 413b and the second pressure regulating valve 413d.

Due to the opening of the second pressure control valve 413d, the boil-off gas filled in the pressure vessel 412 is transferred to the chamber 411, thereby increasing the internal pressure of the chamber 411. Then, when the air pressure of the chamber 411 is equal to the air pressure of the pressure vessel 412, the liquid may be transferred from the chamber 411 to the pressure vessel 412 through the second discharge valve 413b by gravity.

The pressure vessel 412 may have a higher internal pressure than the liquefied gas storage tank 10, and the liquid introduced into the pressure vessel 412 may be smoothly returned to the liquefied gas storage tank 10 without a problem. .

In this way, the valve unit 413 controls the flow of the liquid discharge line L2 and the pressure regulating lines L30 and L31 so that the liquid separated from the separator 40 moves the chamber 411 and the pressure vessel 412. While going through it to be smoothly returned to the liquefied gas storage tank 10 without a separate pressurized fluid.

In other words, the valve 413 opens the liquid discharge line L2 upstream of the chamber 411 and the first pressure regulating line L30 between the separator 40 and the chamber 411, and the chamber 411. The liquid discharge line L2 downstream and the second pressure control line L31 between the chamber 411 and the pressure vessel 412 are closed to allow the liquid to flow into the chamber 411 from the separator 40.

Thereafter, the valve unit 413 has a liquid discharge line upstream of the chamber 411 when the liquid level in the chamber 411 exceeds a preset value (or when the liquid delivery time to the chamber 411 passes a predetermined time). L2) and the first pressure regulating line L30 between the separator 40 and the chamber 411 and closing the liquid discharge line L2 downstream of the chamber 411 and between the chamber 411 and the pressure vessel 412. The second pressure control line (L31) of the may be to allow the liquid in the chamber 411 to drain to the pressure vessel (412).

In particular, even when the air pressure of the pressure vessel 412 is higher than the pressure of the chamber 411, when the valve portion 413 opens the liquid discharge line L2 and the second pressure regulating line L31 downstream of the chamber 411. The evaporation gas may flow from the pressure vessel 412 into the chamber 411 according to the open second pressure control line L31, and as the internal pressure of the chamber 411 rises, liquid may be removed from the chamber 411. The pressure vessel 412 is drained.

Thereafter, when the drain from the chamber 411 is set in a predetermined amount (for example, when the liquid level in the chamber 411 is less than or equal to the preset value or the drain has passed a predetermined time), the second discharge valve 413b and the second pressure are applied. As the control valve 413d is closed, the liquid discharge line L2 downstream of the chamber 411 and the second pressure control line L31 between the chamber 411 and the pressure vessel 412 are closed.

In addition, the first discharge valve 413a and the first pressure control valve 413c are opened, and the liquid discharge line L2 upstream of the chamber 411 and the first pressure control line L30 between the separator 40 and the chamber 411. ) Is opened, so that the pressures of the chamber 411 and the separator 40 can be equally adjusted.

Therefore, the inflow of the liquid from the separator 40 to the chamber 411 is made again. As described above, the present embodiment allows the liquid separated from the separator 40 to be returned to the liquefied gas storage tank 10 through the chamber 411 and the pressure vessel 412 without a separate nitrogen supply, thereby adding unnecessary configuration. It can prevent the system operation efficiency.

The liquefier 50 liquefies the compressed boil-off gas. The liquefier 50 may cool the evaporated gas using various refrigerants, which are not limited. For example, the refrigerant may be nitrogen, liquefied gas, mixed refrigerant, or the like.

The boil-off gas liquefied by the liquefier 50 may be returned to the liquefied gas storage tank 10 in the liquid phase. Therefore, even if the boil-off gas is generated in the liquefied gas storage tank 10, as the boil-off gas is returned after discharge and liquefaction, the internal pressure of the liquefied gas storage tank 10 can be maintained at a stable level.

However, the evaporated gas introduced into the liquefier 50 may be compressed to increase the boiling point, and a valve (not shown) may reduce the evaporated gas between the liquefier 50 and the liquefied gas storage tank 10. ) May be provided.

Of course, considering the internal volume of the liquefied gas storage tank 10, even if the evaporated gas is returned without a separate decompression may be naturally reduced in the liquefied gas storage tank 10, the pressure reducing valve may not be provided.

The gas-liquid separator 60 gas-separates the liquefied boil-off gas. Even if the liquefier 50 liquefies the boil-off gas using nitrogen or the like, nitrogen or the like having a very low boiling point included in the boil-off gas may remain in a gaseous state.

Therefore, the gas-liquid separator 60 may filter out the material remaining in the gaseous state of the boil-off gas introduced through the liquefier 50, wherein the gaseous material is referred to as flash gas.

The flash gas contains nitrogen but still has a calorific value, and since it is a low temperature state, recycling is preferable. Therefore, the flash gas may be discharged from the gas-liquid separator 60 and introduced into the compressor 20 upstream, or may be introduced into the precooler 30.

The liquid return line L4 is provided from the gas-liquid separator 60 to the liquefied gas storage tank 10. The liquid evaporated gas may flow into the liquefied gas storage tank 10 along the liquid return line L4.

The liquid delivery line L5 may be branched to the liquid return line L4, and the liquid delivery line L5 is connected to the precooler 30. Therefore, the boil-off gas liquefied by the liquefier 50 and gas-liquid separated may be used for cooling the boil-off gas in the precooler 30.

Thus, this embodiment, since the liquid separated from the separator 40 after precooling is smoothly returned to the liquefied gas storage tank 10 through the chamber 411 and the pressure vessel 412 without the injection of nitrogen, the configuration is simplified And prevent unnecessary heat penetration.

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

Hereinafter, the present embodiment will be described based on the point that the present embodiment is different from the previous embodiment, and the description thereof will be replaced with the above contents. This is also true in other embodiments described below.

2, in the boil-off gas cooling system 1 according to the second embodiment of the present invention, unlike the previous embodiment, the gas-liquid separator 60 is omitted and the pressure vessel 412 serves as the gas-liquid separator 60. Do this.

That is, in the present embodiment, the pressure vessel 412 may receive the boil-off gas compressed in the compressor 20 and liquefied in the liquefier 50. However, since the pressure vessel 412 should serve to implement the pressure rise of the chamber 411, the pressure vessel 412 may allow the internal pressure to increase somewhat while the liquefied evaporated gas introduced therein is naturally vaporized. .

Therefore, the pressure vessel 412 may use at least a portion of the liquefied boil-off gas to return the liquid separated from the separator 40, and the rest is returned to the liquefied gas storage tank 10 through the liquid return line L4. can do.

The liquefied gas supply line L8 may be connected to the pressure vessel 412 from the liquefied gas storage tank 10, and the liquefied gas supply line L8 connected to the demand destination 100 may be branched to the liquid return line L4. Can be.

In this case, the demand source 100 may be the same as or different from the demand source 100 to which the boil-off gas supply line L6 is connected. For example, the demand source 100 to which the liquefied gas supply line L8 is connected is the main engine. And, the demand destination 100 to which the boil-off gas supply line (L6) is connected may be a power generation engine, GCU.

In this embodiment, in order to ensure the operation of the demand source 100 as the main engine, the liquefied gas may be replenished in the pressure vessel 412 in case the flow rate of the boil-off gas flowing into the pressure vessel 412 is insufficient. That is, the liquefied evaporated gas and the liquefied gas may be mixed in the pressure vessel 412 and delivered to the demand destination 100.

When all the boil-off gas generated from the liquefied gas storage tank 10 is mixed with the liquefied gas and supplied to the demand destination 100, the consumption of the liquefied gas decreases as the amount of the boil-off gas increases, so that energy consumption efficiency may be improved. have.

However, when the amount of boil-off gas is insufficient when using the boil-off gas together with the liquefied gas as fuel, there is a problem that the energy consumption efficiency is not good.

On the other hand, if all the liquefied gas generated in the liquefied gas storage tank 10 is liquefied and only the liquefied gas is supplied to the demand destination 100, the energy consumption efficiency is relatively constant regardless of the amount of generated boiled gas.

However, in this case, there is a problem that energy may be wasted a little because the refrigerant must be used for reliquefaction of the boiled gas at all times, and if a large amount of boiled gas is generated, a large amount of refrigerant needs to be cooled, so energy consumption is higher than that of supplying boil-off gas as fuel. The efficiency becomes worse.

In this embodiment, in consideration of the energy consumption efficiency in the case of using the evaporated gas as the total amount of fuel, and the total amount of re-liquefied evaporated gas, it is possible to supply the re-liquefied evaporated gas to the fuel while re-liquefying the evaporated gas. For example, the liquefied gas may be mixed with the boil-off gas supplied as fuel.

In this embodiment, when the amount of generated evaporation gas is less (than the required amount of demand), it is possible to re-liquefy the evaporated gas and supply the liquefied gas mainly as fuel (mixed supply of the liquefied gas and the evaporated gas) to increase energy consumption efficiency. On the contrary, when the amount of generated boil-off gas is larger than the demand, it is possible to increase the energy consumption efficiency by supplying the boil-off gas mainly as fuel (stopping the supply of the liquefied gas).

At this time, the amount of generated boil-off gas can be measured by a pressure gauge provided in the liquefied gas storage tank 10 or a flow meter provided in the boil-off gas liquefaction line (L1) and the like. Obviously, it can be confirmed through an engine load.

As described above, the supply of liquefied gas to the demand destination 100 may be equally applicable to other embodiments in which the liquefied boil-off gas is introduced into the pressure vessel 412. However, in the first embodiment, the liquefied gas supply line L8 may be connected to the gas-liquid separator 60 in the liquefied gas storage tank 10 or may be connected to the demand destination in the gas-liquid separator 60.

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

Referring to FIG. 3, in the case of the boil-off gas cooling system 1 according to the third embodiment of the present invention, the position of the liquid discharge line L2 connected downstream of the chamber 411 may be different.

2, the liquid discharge line L2 is connected to the pressure vessel 412 via the chamber 411 in the separator 40, the valve portion 413 is the liquid level in the chamber 411 If it exceeds this preset value, the pressure of the chamber 411 and the pressure vessel 412 can be adjusted equally.

In contrast, in the present embodiment, the liquid discharge line L2 is connected to the liquid return line L4 by bypassing the pressure vessel 412 via the chamber 411 in the separator 40. Therefore, the valve unit 413 of the present embodiment, instead of adjusting the pressure of the chamber 411 and the pressure vessel 412 equally, so that the liquid can be smoothly discharged from the chamber 411 to the liquid return line (L4), The transfer of the boil-off gas from the pressure vessel 412 to the chamber 411 may be implemented.

In this embodiment, the pressure vessel 412 may be replaced with the gas-liquid separator 60 in that the liquefied boil-off gas is delivered to the liquefied gas storage tank 10. That is, the present embodiment may be interpreted as an invention in which the pressure vessel 412 is omitted and the gas-liquid separator 60 is used as the pressure vessel 412.

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

Referring to FIG. 4, in the boil-off gas cooling system 1 according to the fourth embodiment of the present invention, the liquid return part 41 may be omitted. As mentioned above, the precooler 30 may cool the boil-off gas using the liquid boil-off gas separated from the gas-liquid separator 60.

In this case, the precooler 30 cools the boil-off gas by using a liquid boil-off gas having no or no heavy carbon ratio in place of the liquefied gas. Thus, the pre-cooler 30 has a liquid state in the boil-off gas introduced into the separator 40 after pre-cooling. May have (almost) no heavy carbon.

Therefore, in the present embodiment, the separator 40 may be provided to store the liquid without separating the liquid, and the chamber 411 or the pressure vessel 412 receiving the liquid from the separator 40 may be omitted.

In the present embodiment, the separator 40 may also be omitted. Since the heavy carbon is not (almost) already contained in the boil-off gas discharged from the liquefied gas storage tank 10, the precooler 30 mixing the liquefied boil-off gas with the boil-off gas discharged from the liquefied gas storage tank 10. Also, in heavy liquid carbon may not be present, the material entering the compressor 20 may be only gaseous methane and nitrogen.

Therefore, in this embodiment, the configuration and process itself for separating the liquid with respect to the boil-off gas introduced into the compressor 20 after pre-cooling may be omitted.

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

Referring to FIG. 5, the boil-off gas cooling system 1 according to the fifth embodiment of the present invention further includes a heat exchanger 70 and a pump 80.

For reference, in this embodiment, the boil-off gas is cooled in the heat exchanger 70 to be described later, compressed in the compressor 20, liquefied in the liquefier 50, and then passed through the gas-liquid separator 60 to store the liquefied gas storage tank ( 10) can be returned.

The heat exchanger 70 cools the boil-off gas upstream of the compressor 20. The heat exchanger 70 may cool the boil-off gas flowing into the compressor 20 similarly to the precooler 30 in the previous embodiment, except that the heat exchanger 70 of the present embodiment is a liquefied gas storage tank 10. Evaporated gas may be cooled by using the liquefied gas discharged from) and delivered to the demand destination 100.

The gas-liquid separator 60 of the present embodiment may be introduced along the liquefied gas discharge line L7 as well as the liquefied gas liquefied gas discharged from the liquefied gas storage tank 10. At this time, the liquid part is returned to the liquefied gas storage tank 10 through the liquid return line L4, and the liquid part is branched from the liquid return line L4 to the liquefied gas supply line L8 connected to the demand destination 100. It may be delivered to the demand destination 100 through.

That is, the liquid separated from the gas-liquid separator 60 may be returned to the liquefied gas storage tank 10 or supplied to the demand destination 100, wherein the liquid supplied to the demand destination 100 is evaporated gas from the heat exchanger 70. Used for cooling.

The liquid delivered to the heat exchanger 70 may be liquefied gas discharged from the liquefied gas storage tank 10 and introduced into the gas-liquid separator 60, and also liquefied in the liquefier 50 and introduced into the gas-liquid separator 60. May be evaporated gas. Therefore, the heat exchanger 70 may cool the boil-off gas by using the liquefied gas delivered to the demand destination 100 and the liquid boil-off gas separated from the gas-liquid separator 60.

In the liquefied gas storage tank 10, the boil-off gas via the compressor 20 may be supplied to the demand destination 100 along the boil-off gas supply line L6, and the gas separated in the gas-liquid separator 60 is described above. As flash gas, it is mixed upstream of the compressor 20 in the boil-off gas supply line L6.

To this end, a gas mixing line L9 may be provided as the boil-off gas supply line L6 in the gas-liquid separator 60. When the initial behavior or when the evaporation gas temperature is high or the flow rate of the liquefied gas supplied to the demand destination 100 is small, the liquefied gas is not partly increased due to insufficient pressure of the rear end pressure of the compressor 20, the gas-liquid separator 60 There is a two-phase state in which the liquid and flash gas are mixed, wherein the temperature of the flash gas is the saturation temperature of the pressure of the gas-liquid separator 60.

Therefore, since the flash gas may be lower than the temperature flowing into the compressor 20, the present embodiment may lower the temperature of the boil-off gas flowing into the compressor 20 by joining the flash gas upstream of the compressor 20. The resulting increase in the rear pressure and the liquefaction efficiency of the compressor 20 are obtained as described above.

However, the present embodiment may further include an auxiliary compressor (not shown) between the heat exchanger 70 and the point where the gas mixing line L9 is connected in the boil-off gas supply line L6. The gas may be cooled while being mixed, first compressed in the auxiliary compressor, cooled in the heat exchanger 70, and second compressed in the compressor 20, and then supplied to the demand destination 100 or liquefied by the liquefier 50.

The pump 80 pressurizes the liquefied gas via the gas-liquid separator 60 in the liquefied gas storage tank 10. The pump 80 may be a reciprocating pump 80 or the like, and liquefied gas (and liquefaction) delivered from the gas-liquid separator 60 to the heat exchanger 70 along the liquid return line L4 and the liquefied gas supply line L8. Boil-off gas) can be pressurized to the required pressure of the demand destination 100.

Since the pump 80 may be provided upstream of the heat exchanger 70 in the liquefied gas supply line L8, the heat exchanger 70 may cool the boil-off gas by using the liquefied gas downstream of the pump 80. . In this case, however, since the temperature of the liquefied gas pressurized by the pump 80 is increased, the preheating of the boil-off gas in the heat exchanger 70 may not be sufficiently performed.

In order to solve this problem, the following sixth embodiment may further include a precooler 30 similar to that described above. It will be described later.

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

Referring to FIG. 6, the boil-off gas cooling system 1 according to the sixth embodiment of the present invention further includes a precooler 30 and a separator 40 as compared with the fifth embodiment in FIG. 5.

The precooler 30 is similar to that described in the first embodiment, but the precooler 30 of the present embodiment may utilize a liquefied gas in addition to the liquefied evaporated gas. In this case, the precooler 30 may be provided between the heat exchanger 70 and the compressor 20 to cool the boil-off gas by mixing the liquefied gas delivered to the demand destination 100. The liquefied gas upstream of the pump 80 is mixed to cool the boil-off gas.

The separator 40 provided downstream of the precooler 30 may separate the liquid from the precooled boil-off gas. When the liquefied gas is mixed in the precooler 30, the heavy carbon may be separated into the liquid in the separator 40, and the separator 40 may be provided with the liquid return unit 41 described above.

However, in the present embodiment, the evaporated gas is first cooled by the heat exchanger 70, and as the liquefied gas is supplied to the demand destination 100, the flow rate of the liquefied gas delivered to the precooler 30 may be compared with the first embodiment. Since it can be less, the capacity of the compressor 20 or the liquefier 50 can be reduced.

As described above, in the present embodiment, by cooling the boil-off gas upstream of the compressor 20 using the liquefied gas and the liquefied boil-off gas supplied to the demand destination 100, the liquefaction performance can be improved by increasing the compression efficiency.

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

Referring to FIG. 7, the boil-off gas cooling system 1 according to the seventh embodiment of the present invention includes a compressor 20, a precooler 30, and a liquefier 50.

The compressor 20 includes a first compressor 21 and a second compressor 22. The first compressor 21 compresses the boil-off gas generated in the liquefied gas storage tank 10, the second compressor 22 is driven by a different drive source than the first compressor 21 and compressed in the first compressor 21 The compressed boil off gas is further compressed. That is, the first compressor 21 and the second compressor 22 are disposed in series on the boil-off gas liquefaction line L1.

The first compressor 21 may have a design pressure of a predetermined value or less, and the second compressor 22 may have a design pressure of a predetermined value or more. In this case, the preset value may be a value for distinguishing the required pressure of the power generation engine (less than 10 bar) and the pressure suitable for reliquefaction (around 20 bar), or the required pressure of the main engine (about 20 bar) and the required pressure of the power generation engine. It may be a value for distinguishing and may be, for example, about 10 bar.

Therefore, the pressure of the boil-off gas compressed in the first compressor 21 may be a pressure suitable for the demand destination 100 such as a power generation engine or a GCU, and the pressure of the boil-off gas compressed in the second compressor 22 is suitable for reliquefaction. It may be a pressure suitable for the demand destination 100, such as a pressure or a main engine. A boil-off gas branch line L61 may be provided downstream from the boil-off gas liquefaction line L1 to the demand destination 100 such as a power generation engine.

That is, the second compressor 22 is manufactured to withstand the final pressure required by the liquefier 50 or the demander 100, while the first compressor 21 is designed to withstand only a lower pressure and thus the compressor 20 ) Can reduce the overall cost.

In addition, in the present embodiment, the first compressor 21 and the second compressor 22 having different design pressures can both have a head (pressure head) of less than or equal to a predetermined value. In this case, the head may correspond to a difference between the front and rear pressure difference, the inflow pressure, and the discharge pressure of the compressor 20.

That is, in this embodiment, the head of the compressor 20 provided downstream is not larger than the head of the compressor 20 provided upstream, but the heads of the first compressor 21 and the second compressor 22 provided in series are preset. The predetermined value may be about 10 bar, and the heads of the first compressor 21 and the second compressor 22 may be the same or at least similar to each other.

In this case, the pressure of the boil-off gas compressed by the first compressor 21 is about 10 bar, and the pressure of the boil-off gas compressed by the second compressor 22 is about 20 bar. Therefore, it can be compressed according to the effective pressure for reliquefaction or the pressure required by the main engine (for example, about 16 bar when the main engine is XDF).

The second compressor 22 of the present embodiment may be provided in plural and arranged in parallel with respect to the boil-off gas liquefaction line L1 connected from the liquefied gas storage tank 10 to the liquefier 50. As an example, as shown in the drawing, the second compressor 22 may be two or more, and is provided to be able to back up each other.

In addition, in the present exemplary embodiment, since the heads of the first compressor 21 and the second compressor 22 are both less than or equal to a predetermined value, the first compressor 21 may be formed by at least one second compressor 22. Backup is possible.

However, for this purpose, in the boil-off gas liquefaction line L1 in which the first compressor 21 and the second compressor 22 are provided in series, another second compressor 22 downstream of one second compressor 22 is provided. The boil-off gas return line L62 may be provided to transfer the boil-off gas upstream.

Therefore, when a problem occurs in the compression of the first compressor 21, the boil-off gas is compressed by a head less than a predetermined value by any one of the second compressor 22, and then along the boil-off gas return line L62. One second compressor 22 may be further compressed by a head of less than or equal to a predetermined value and compressed to a state corresponding to the final pressure.

In addition, the boil-off gas return line L62 is provided upstream of the point where the boil-off gas branch line L61 branches so that the second compressor 22 backs up the first compressor 21, so that the second compressor 22 The compressed boil-off gas can be smoothly supplied to the power generation engine through the boil-off gas return line (L62).

In such a situation, the boil-off gas liquefaction line (L1) bypasses the first compressor 21 in the boil-off gas liquefaction line (L1) so that the boil-off gas does not flow into the second compressor (22). An evaporative gas bypass line L63 may be provided.

The boil-off gas distribution valve 23 is provided to distribute the boil-off gas from the boil-off gas liquefaction line L1 to the second compressors 22 arranged in parallel, and the boil-off gas return line L62 has an boil-off gas return valve ( 24 is provided, the boil-off gas bypass line (L63) is provided with the boil-off gas bypass valve (25).

For example, when a problem occurs in any one of the second compressor 22, the boil-off gas distribution valve 23 may transfer all of the boil-off gas to the second compressor 22 without any problem. Alternatively, when a problem occurs in the first compressor 21, the boil-off gas return valve 24 and the boil-off gas bypass valve 25 are opened, so that even if there is no compression by the first compressor 21, the second compressor 22 The final discharged boil-off gas can be compressed to two times or less (more than one time) the preset head of each compressor 20.

In this way, the first compressor 21 and the second compressor 22 are both in the liquefied gas storage tank 10 so that the plurality of second compressors 22 can back up each other while also backing up the first compressor 21. It may have a capacity capable of processing 100% of the generated boil-off gas.

The precooler 30 may be provided upstream of the liquefier 50 to precool the evaporated gas before heat exchange with the refrigerant to reduce the heat exchange burden of the refrigerant. In particular, the precooler 30 may be provided upstream of the second compressor 22 to reduce the volume of the boil-off gas flowing into the second compressor 22 to reduce the power of the second compressor 22.

The precooler 30 may cool the boil-off gas by using the liquid boil-off gas liquefied in the liquefier 50 similarly to those described in the above embodiments. At this time, the liquid evaporated gas heated in the precooler 30 may be further heated if necessary and then transferred to the demand destination 100 for consumption.

The precooler 30 is provided in the boil-off gas liquefaction line L1 in a parallel structure, and an auxiliary precooler 31 for backing up the precooler 30 may be provided. However, the auxiliary precooler 31 may lower the temperature of the boil-off gas by using a separate material such as fresh water or sea water, instead of using the boil-off gas unlike the pre-cooler 30.

The precooler 30 implements precooling using the evaporated gas delivered to the demand destination 100 after liquefaction. The amount of the liquefied evaporated gas is returned to the liquefied gas storage tank 10 and introduced into the precooler 30. If this is reduced, sufficient precooling may not be achieved in the precooler 30.

In order to solve this problem, an auxiliary precooler 31 using a material supplied regardless of the amount of boil-off gas or the operation of the demand source 100 may be provided. 31 may be omitted.

The liquefier 50 liquefies at least one part by heat-exchanging the boil-off gas compressed by the 2nd compressor 22 with a refrigerant. The cooling system used by the liquefier 50 is not particularly limited, and various refrigerants such as mixed refrigerants and the like may be used.

The boil-off gas liquefied in the liquefier 50 is delivered to the gas-liquid separator 60 along the boil-off gas liquefaction line (L1), the liquid gas storage tank 10 in the gas-liquid separator 60 through the liquid return line (L4). Can be returned.

Alternatively, the liquid evaporated gas delivered to the gas-liquid separator 60 may be supplied and consumed to the demand destination 100 such as the main engine along the evaporated gas supply line L6, in which case the flow flows to the evaporated gas supply line L6. The liquid boil-off gas may be via the precooler 30.

However, since the final pressure required by the main engine may be higher than the proper pressure required for reliquefaction, the pump 80 for compressing the liquid evaporated gas to the required pressure of the demand destination 100 is provided in the boil-off gas supply line L6. Can be.

In this case, the design pressure of the second compressor 22 may be a pressure suitable for reliquefaction but less than the required pressure of the main engine.

As described above, in the present embodiment, three compressors 20 having the same head can be provided while being able to process 100% of the evaporated gas generated in the liquefied gas storage tank 10, so that a problem occurs in one compressor 20. While the other two compressors 20 can process all of the evaporated gas, the required pressure of the liquefier 50 or the main engine can be adjusted without problems.

In addition, the present embodiment generates a pressure higher than 10bar by continuously operating two compressors 20 having a head of 10bar, one compressor 20 can reduce the overall pressure of the compressor 20 by lowering the design pressure.

The present invention is not limited to the above-described embodiments, and may include, as another embodiment, a combination of at least two or more of the above embodiments or a combination of at least one of the contents of the embodiments and a known technology. Of course.

The present invention has been described above with reference to the embodiments of the present invention. However, the present invention is only an example, and is not intended to limit the present invention. Those skilled in the art do not depart from the essential technical details of the present embodiment. It will be appreciated that various combinations or modifications and applications that are not exemplified in the embodiments are possible in scope. Therefore, technical matters related to modifications and applications easily derivable from the embodiments of the present invention should be interpreted as being included in the present invention.

1: boil-off gas cooling system 10: liquefied gas storage tank
20: compressor 21: first compressor
22: second compressor 23: boil off gas distribution valve
24: boil off gas return valve 25: boil off gas bypass valve
30: precooler 31: auxiliary precooler
40: separator 41: liquid return part
411: chamber 412: pressure vessel
413: valve portion 413a: first discharge valve
413b: second discharge valve 413c: first pressure regulating valve
413d: second pressure regulating valve 50: liquefier
60: gas-liquid separator 70: heat exchanger
80: pump 100: demand source
L1: boil off gas liquefaction line L2: liquid discharge line
L30: first pressure regulating line L31: second pressure regulating line
L4: Liquid Return Line L5: Liquid Delivery Line
L6: boil-off gas supply line L61: boil-off gas branch line
L62: boil off gas return line L63: boil off gas bypass line
L7: liquefied gas discharge line L8: liquefied gas supply line
L9: Gas Mixing Line

Claims (6)

A compressor for compressing the boil-off gas generated in the liquefied gas storage tank;
A precooler for cooling the boil-off gas upstream of the compressor;
A liquefier for liquefying the compressed boil-off gas; And
It includes a gas-liquid separator for gas-liquid separation of liquefied evaporated gas,
The precooler,
Evaporation gas cooling system characterized in that for cooling the evaporation gas using the liquid evaporation gas separated from the gas-liquid separator. The method of claim 1,
And a separator for separating liquid between the precooler and the compressor. The method of claim 2, wherein the separator,
Evaporative gas cooling system characterized in that it is provided to store without discharging the liquid. The method of claim 2,
An evaporative gas liquefaction line connected to the gas-liquid separator through the precooler, the separator, the compressor, and the liquefier in the liquefied gas storage tank;
A liquid return line connected to the liquefied gas storage tank in the gas-liquid separator; And
And a liquid delivery line branched from said liquid return line to said precooler. The method of claim 1, wherein the precooler,
Evaporating gas cooling system characterized in that for cooling the evaporated gas using a liquid evaporated gas having no or less ratio of heavy carbon in place of the liquefied gas. Ship having the boil-off gas cooling system according to any one of claims 1 to 5.

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