JP2009030675A - Device and method for re-liquefying gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method for re-liquefying a gas capable of reducing the generated amount of a boil-off gas to reduce power by positively utilizing cold of impurity components with low boiling points. <P>SOLUTION: This gas re-liquefying device 1 comprises a boil-off gas compressor 17 for introducing and compressing the boil-off gas vaporized in a storage tank 9 for storing a LNG2 containing nitrogen with a lower boiling point, a liquefier 7 for cooling and condensing the boil-off gas compressed by the boil-off gas compressor 17, and a separator 11 for separating the condensate by the liquefier 7 into a gas and a liquid. The liquid separated by the separator 11 is recirculated to the inside of the LNG2, and the gas is discharged to the outside. The device further comprises a methane rich gas pipe 19 for gasifying and supplying a part of the liquid near the liquid level 27 of the LNG2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gas reliquefaction apparatus and a gas reliquefaction method for reliquefying boil-off gas generated from a storage tank for storing liquefied gas.

  As such a gas reliquefaction device, for example, as disclosed in Patent Document 1, after boil-off gas generated from a storage tank is compressed and cooled, gas-liquid separation is performed and the liquefied component is returned to the storage tank. Things that do are used a lot.

JP 2001-132899 A

By the way, the liquefied natural gas (hereinafter referred to as LNG) loaded by the LNG ship contains, for example, 0.2 to 0.4 wt% of impurities such as nitrogen. Since nitrogen has a lower boiling point than LNG, nitrogen tends to be concentrated to about 5 to 15% in the boil-off gas.
When all the conventional boil-off gas is liquefied and returned to the tank, the power to liquefy nitrogen with no combustion heat and low commercial value is wasted, and the proportion of nitrogen in the boil-off gas increases with time, and waste is further reduced. There was a problem of becoming larger.
In order to suppress this, a part of the boil-off gas is liquefied and returned to the tank as in Patent Document 1, and the other part is discharged to the outside as a gas state (containing a lot of nitrogen that is difficult to liquefy) (fuel) Have been proposed). This can reduce the amount of nitrogen in the tank, but does not actively reduce the amount of boil-off gas itself, and does not have the effect of actively extracting nitrogen in LNG. Therefore, if this can be realized, the power can be further reduced.

  In view of the above points, the present invention actively utilizes the cold energy of low-boiling impurity components (for example, nitrogen), reduces the amount of boil-off gas generated, and reduces the power. An object is to provide a liquefaction method.

In order to solve the above problems, the present invention employs the following means.
That is, the gas reliquefaction apparatus according to the present invention is a compressor that introduces and compresses boil-off gas evaporated in a storage tank that stores a liquefied gas containing an impurity component having a lower boiling point, and is compressed by the compressor. A heat exchanger that cools and condenses the boil-off gas; and a gas-liquid separator that separates the condensed fluid condensed in the heat exchanger into a gas and a liquid, and separated by the gas-liquid separator. A gas re-liquefaction apparatus that recirculates liquid to the inside of the liquefied gas and discharges the gas to the outside, comprising supply means for gasifying a part of the liquid and supplying it near the liquid surface of the liquefied gas It is characterized by.

According to the present invention, the boil-off gas is compressed by the compressor and enters the heat exchanger and is condensed with a higher pressure than in the storage tank.
At the time of this condensation, since the liquid having a high boiling point is changed to a liquid, the liquid flowing into the gas-liquid separator is mainly a liquefied gas component.
Further, since the pressure is higher than in the storage tank, the ratio of the impurity components that can be contained in the gas is larger than in the storage tank.
For this reason, the liquid separated by the gas-liquid separator becomes a gas or liquid containing a low boiling point impurity component contained in the boil-off gas.

Since the supplying means gasifies a part of the liquid and supplies it near the liquid level of the liquefied gas, a contact surface where the gasified liquid and the liquefied gas come into contact is formed.
Since the components try to equilibrate at the contact surface where the gas and liquid are in contact, the impurity components contained in the liquefied gas move to the gasified liquid formed from the liquefied gas components that contain almost no impurity components, and gasification occurs. That is, it will evaporate.
When this impurity component evaporates, the ambient temperature is lowered by the latent heat of vaporization, so that the inside of the storage tank can be cooled. In this way, when the inside of the storage tank is cooled, the total amount of heat that enters the storage tank and heats the liquefied gas is reduced, so that the amount of boil-off gas generated can be reduced.
When the amount of boil-off gas generated is reduced, the total amount of gas liquefied by the gas reliquefaction device is reduced, so that the power for liquefying them can be reduced. In other words, the reliquefaction efficiency of the gas reliquefaction apparatus can be improved.

In addition, if the impurity component contained in the vicinity of the liquid level of the liquefied gas in the storage tank is selectively evaporated, the content ratio of the impurity component is reduced in this portion, but it tends to equilibrate in the liquefied gas. The impurity component moves from the vicinity of the liquid surface. Thereby, since the content rate of the impurity component in the vicinity of the liquid surface does not rapidly decrease, the above-described cooling effect can be maintained until the total amount of the impurity component is considerably reduced.
Furthermore, since the gas in the gas-liquid separator containing a large amount of impurity components is discharged to the outside, the impurity components gasified in the storage tank can be efficiently discharged.
As the “liquefied gas”, for example, liquefied natural gas (LNG) is suitable.
Further, “gasification” in the supply means means that gas is present. Therefore, the state supplied from the supply means includes a gas-liquid mixed state.
Furthermore, as the cold heat source of the heat exchanger, for example, an expander using nitrogen as a refrigerant is suitable.

  In the gas reliquefaction apparatus according to the present invention, the supply means is configured to supply the gasified liquid to the liquid level of the storage tank over a wide range.

  Thus, since the supply means is configured to supply the gasified liquid over a wide range, the contact area between the gasified liquid and the liquefied gas (for example, LNG) is widened, and the impurity components are evaporated. It can be done efficiently.

  Furthermore, in the gas reliquefaction apparatus according to the present invention, the gasification of the liquid in the supply means is performed using the amount of heat of the boil-off gas condensed in the heat exchanger, and the boil-off gas side is It is precooled.

  As described above, since the gasification of the liquid in the supply means is performed using the amount of heat of the boil-off gas condensed in the heat exchanger, the cold heat of the liquid is utilized for precooling and condensation of the boil-off gas. For this reason, the thermal efficiency of a gas reliquefaction apparatus can be improved further.

  In the gas reliquefaction apparatus according to the present invention, the gas discharged from the gas-liquid separator is configured to pass through the heat exchanger.

Thus, since the gas discharged | emitted from a gas-liquid separator is comprised so that a heat exchanger may be passed, the gas from the compressor which flows through a heat exchanger will be cooled further. Thus, since it decided to utilize effectively the cold of the gas discharged | emitted from a gas-liquid separator, a gas reliquefaction apparatus with high thermal efficiency can be provided.
In addition, the gas discharged | emitted outside by the discharge pipe line is normal temperature gas, For example, the method of carrying out a combustion process easily with the combustion apparatus provided outside can be taken.

  In the gas reliquefaction method according to the present invention, the boil-off gas evaporated in a storage tank for storing a liquefied gas containing an impurity component having a lower boiling point is taken out and compressed, and the compressed boil-off gas is cooled. A gas reliquefaction method for condensing, condensing condensed condensed fluid into gas and liquid, refluxing the separated liquid to the inside of the liquefied gas and discharging the gas to the outside, A part is gasified and supplied to the vicinity of the liquid level of the liquefied gas.

According to the invention, the boil-off gas is compressed and condensed with a higher pressure than in the storage tank.
At the time of this condensation, since the liquid having a high boiling point is changed to a liquid, the liquid contained in the condensed fluid is mainly composed of a high boiling point component (methane in the example of LNG).
Further, since the pressure is higher than in the storage tank, the proportion of low boiling point impurity components (nitrogen in the example of LNG) that can be contained in the gas is larger than in the storage tank.
For this reason, the liquid separated from the condensed fluid is composed of a liquefied gas component with reduced impurity components.

Since a part of the liquid is gasified and supplied to the vicinity of the liquid level of the liquefied gas, a contact surface where the gasified liquid and the liquefied gas come into contact is formed.
Since the components in the gas and liquid try to equilibrate at the contact surface where the gas and liquid are in contact, the impurity components contained in the liquefied gas move to the gasified liquid formed from the liquefied gas component that contains almost no impurity components. Gasification, that is, evaporation.
When this impurity component evaporates, the latent heat of evaporation removes ambient heat and lowers the temperature, so that the storage tank can be cooled. In this way, when the inside of the storage tank is cooled, the total amount of heat that enters the storage tank and heats the liquefied gas is reduced, so that the amount of boil-off gas generated can be reduced.
When the amount of boil-off gas generated is reduced, the total amount of gas liquefied by the gas reliquefaction method is reduced, so that the power for liquefying them can be reduced. In other words, reliquefaction efficiency can be improved.

In addition, when the impurity component contained in the vicinity of the liquid level of the liquefied gas in the storage tank is selectively evaporated, the content ratio of the impurity component is reduced in this portion, and the liquid temperature is also increased, so that the liquid with low low boiling point impurities is stored in the storage tank. It tends to stay in the surface layer. Due to the tendency of the components to equilibrate evenly in the liquefied gas, there is an effect that the impurity component moves from the other part to the vicinity of the liquid surface, but by actively circulating it using the liquefied gas transfer pump in the tank Thus, it can be avoided that the low boiling point impurities near the liquid surface are rapidly reduced and the extraction effect is hindered.
Furthermore, since the gas separated from the condensed fluid containing a large amount of impurity components is discharged to the outside, the impurity components gasified in the storage tank can be efficiently discharged out of the system.
In the present invention, “gasification” means that gas is present. Therefore, the supplied state includes a gas-liquid mixed state.

According to the present invention, since a part of the liquid composed of the liquefied gas component containing almost no impurity component is gasified and supplied to the vicinity of the liquid level of the liquefied gas, the contact surface between the gasified liquid and the liquefied gas is used. The impurity component contained in the liquefied gas moves and gasifies, that is, evaporates.
When this impurity component evaporates, the ambient temperature is lowered by the latent heat of vaporization, so that the total amount of heat that enters the storage tank and heats the liquefied gas can be reduced, and the amount of boil-off gas generated can be reduced.
When the amount of boil-off gas generated is reduced, the total amount of gas liquefied by the gas reliquefaction device is reduced, so that the power for liquefying them can be reduced.
Further, since the gas in the gas-liquid separator containing a large amount of impurity components is discharged to the outside, the impurity components gasified in the storage tank can be efficiently discharged.

Hereinafter, an embodiment in which the present invention is applied to an LNG ship gas reliquefaction apparatus will be described with reference to FIGS. 1 and 2. The LNG ship includes a plurality of storage tanks 9 that store liquefied natural gas (also referred to as liquefied gas: LNG) 2. There are various types of storage tanks 9. For example, a moss-type tank has a substantially spherical shape as shown in FIG.
The storage tank 9 is provided with a transfer line 10 for transferring the internal LNG 2 to another storage tank 9 or outboard by a transfer pump 8. At the upper part of the storage tank 9, there is provided a spray line 20 that is branched from the transfer line 10 and sprays LNG 2 by a spray header attached to the tip.
When the storage tank 2 is almost empty, the spray line 20 sprays the LNG 2 left at the bottom in order to keep the inside at a low temperature.
FIG. 1 is a block diagram showing an overall schematic configuration of a gas reliquefaction apparatus 1 of an LNG ship.
The gas reliquefaction apparatus 1 is provided with a liquefaction processing unit 3, a refrigeration cycle unit 5, and a liquefier (heat exchanger) 7.

The liquefaction processing unit 3 includes a boil-off gas supply pipe 13 for conveying a boil-off gas from the storage tank 9 to the separator (gas-liquid separator) 11, and a re-liquefied gas pipe 15 for sending the re-liquefied gas from the separator 11 to the storage tank 9. Is provided.
The boil-off gas supply pipe 13 includes a boil-off gas compressor (compressor) 17 that compresses the conveyed boil-off gas.
The boil-off gas supply pipe 13 is connected to the upper part of the side surface of the separator 11 through the condensing part G of the liquefier 7 after leaving the boil-off gas compressor 17.

The reliquefied gas pipe 15 is connected to the storage tank 9 from the lower part of the separator 11 through the supercooling part K of the heat exchanger 7. The reliquefied gas pipe 15 is opened at a lower position in the storage tank 9.
A methane rich gas pipe (supply means) 19 branched from a branch point A located upstream of the supercooling part K in the reliquefied gas pipe 15 and connected to the upper part of the storage tank 9 through the condensing part G is provided. ing.

A flow rate adjustment valve 21 is provided at an intermediate position of the methane rich gas pipe 19. The flow rate adjusting valve 21 has a function of adjusting the flow rate of the liquefied LNG flowing through the reliquefied gas pipe 15 while adjusting the flow rate of the methane rich gas flowing through the methane rich gas pipe 19.
In the vicinity of the storage tank 9 of the methane rich gas pipe 19, a pressure reducing valve 23 that reduces the pressure of the methane rich gas and matches the pressure in the storage tank 9 is provided.
At the end of the methane rich gas pipe 19 on the storage tank 9 side, a distributor 25 is provided that branches the methane rich gas and discharges it to a number of locations.

The distal end portion of the distributor 25 is located at a position substantially in contact with the liquid level 27 of the LNG 2 stored in the storage tank 9, that is, in the vicinity of the liquid level 27.
Depending on the level of the liquid level 27, the tip of the distributor 25 is located above the liquid level 27 and below the liquid level 27 as shown in FIG.
When positioned above the liquid level 27, the methane-rich gas is within a range that reaches the liquid level 27. When positioned below the liquid level 27, the methane-rich gas is within a range that is not liquefied by the LNG2. It is desirable to do.
Therefore, when the level of the liquid level 27 fluctuates greatly, it is desirable that the vertical position of the methane rich gas pipe 19 or the distributor 25 can be adjusted.

  An off-gas pipe 29 is connected to the top of the separator 11. The off-gas pipe 29 is connected to a predetermined place, for example, a gas combustion boiler, through the condensing part G of the vaporizer 7.

The refrigeration cycle unit 5 liquefies the cold heat of the refrigerant circulated through the refrigerant pipe 31 (for example, nitrogen is used as the refrigerant. In addition, for example, propane, hydrogen, and helium are targets). This is supplied to the container 7.
The refrigeration cycle unit 5 includes a refrigerant compressor 33, a first aftercooler 35, a booster compressor 37, a second aftercooler 39, and an expander 41.

The refrigerant compressor 33 sucks and compresses a low-temperature / low-pressure gaseous refrigerant to form a high-temperature / high-pressure gaseous refrigerant.
The first aftercooler 35 cools the high-temperature and high-pressure gaseous refrigerant from the refrigerant compressor 33 and lowers the temperature.
The booster compressor 37 compresses the refrigerant introduced from the first aftercooler 35 to make the refrigerant high temperature and high pressure.

The second aftercooler 39 cools the high-temperature and high-pressure gaseous refrigerant from the booster compressor 37 and lowers the temperature.
The expander 41 expands the refrigerant whose temperature has been lowered through the second aftercooler 39 by decompression to form a low-temperature and low-pressure gaseous refrigerant. The booster compressor 37 is rotated by using the force when the refrigerant expands as a rotational force.
The low-temperature and low-pressure gaseous refrigerant from the expander 41 is sent to the liquefier 7 through the refrigerant pipe 31 and is heat-exchanged through the supercooling part K and the condensing part G in order.

The liquefaction operation of the gas reliquefaction apparatus 1 according to the present embodiment described above will be described.
In the refrigeration cycle unit 5, the refrigerant compressor 33 is driven by a drive source (not shown), and compresses the low-temperature and low-pressure gaseous refrigerant introduced from the refrigerant pipe 31 to obtain a high-temperature and high-pressure gaseous refrigerant. This high-temperature and high-pressure gaseous refrigerant is cooled by the first aftercooler 35 and introduced into the booster compressor 37.
In the booster compressor 37, the introduced high-temperature and high-pressure gaseous refrigerant is compressed to a higher temperature and pressure. This refrigerant is cooled by the second aftercooler 39 and introduced into the expander 41.

The refrigerant introduced into the expander 41 is expanded by decompression to be a low-temperature / low-pressure gaseous refrigerant.
The low-temperature and low-pressure gaseous refrigerant is supplied to the liquefier 7 through the refrigerant pipe 31, and cools by supplying the cold to the surroundings when passing through the supercooling part and the condensing part G.
Thereafter, the refrigerant is sent to the refrigerant compressor 33 to complete one cycle. In the refrigeration cycle unit 5, by continuously performing this cycle, cold heat is provided in the supercooling unit K and the condensing unit G through which the refrigerant pipe 31 passes.

The LNG 2 is loaded into the storage tank 9 of the LNG ship at the loading base. The LNG 2 contains various impurity components in addition to the main component methane (CH ₄ : liquefied gas component).
As an impurity component, nitrogen (N ₂ ) having a boiling point lower than that of methane is included to some extent. The boiling point at atmospheric pressure is about −161 ° C. for methane, and −196 ° C. for nitrogen. The amount of nitrogen contained varies depending on the production area of LNG2.

Although the storage tank 9 has a heat insulating structure, heat still enters from the outside and warms the LNG 2, so that the LNG 2 evaporates and boil-off gas is generated in the upper space of the liquid surface 27. At this time, since the component having a low boiling point evaporates, the amount of nitrogen in the boil-off gas is concentrated and the content ratio is larger than that in LNG2.
The boil-off gas is introduced into the boil-off gas compressor 17 through the boil-off gas supply pipe 13. The introduced boil-off gas is compressed by the boil-off gas compressor 17 to a high temperature / high pressure state.

And it is sent to the condensing part G of the liquefier 7 from the boil-off gas compressor 17. In the condensing unit G, the boil-off gas is cooled and condensed by the low-temperature and low-pressure gaseous refrigerant flowing through the refrigerant pipe 31 of the refrigeration cycle unit 5. When the boil-off gas is condensed, it enters a saturated liquid (condensed fluid) state, that is, a state in which it is easily separated into gas and liquid, and is sent to the separator 11.
When the boil-off gas in the saturated liquid state enters the separator 11, the liquid component having a higher specific gravity moves to the lower part and the gas component having a lower specific gravity moves to the upper part, so that gas-liquid separation is performed.

At the time of this condensation, methane, which is a component with a high boiling point, becomes a liquid, so that nitrogen with a low boiling point remains as a gas. That is, the liquid condensed and separated by the separator 11 is mainly methane.
The pressure in the separator 11 is, for example, a gauge pressure: 0.3 to 0.4 MPa (3 to 4 bar), and is higher than that in the storage tank 9 that is substantially atmospheric pressure (gauge pressure: 0 MPa (0 bar)). Therefore, the ratio of nitrogen that can be contained in the gas is larger than that in the storage tank 9.

Thereby, most of the nitrogen contained in the boil-off gas is contained in the gas component (separated gas component) of the separator 11.
Therefore, the liquid component stored in the lower part of the separator 11, that is, the reliquefied gas is in a state in which nitrogen is hardly contained.
The reliquefied gas is sent through the reliquefied gas pipe 15 and is cooled to a supercooled state (for example, 162.5 ° C.) by the refrigerant passing through the refrigerant pipe 31 of the refrigeration cycle section 5 in the supercooling section K. It is returned to the inside of the LNG 2 of the storage tank 9.

On the other hand, a part of the reliquefied gas sent through the reliquefied gas pipe 15 is branched at the branch point A and sent to the methane rich gas pipe 19.
The reliquefied gas sent through the methane-rich gas pipe 19 is warmed and gasified by the boil-off gas that is being condensed and passes through the boil-off gas supply pipe 13 when passing through the condensing part G, and becomes methane-rich gas.
Since the methane-rich gas pipe 19 is disposed so as to be adjacent to the boil-off gas supply pipe 13 over substantially the entire length of the condensing part G, the methane-rich gas is gasified by receiving a sufficient amount of heat from the boil-off gas supply pipe 13. It is overheated.

  At this time, since the boil-off gas in the boil-off gas supply pipe 13 is cooled by the reliquefied gas flowing through the methane rich gas pipe 19, the cold heat of the reliquefied gas is utilized for condensing the boil-off gas. Therefore, since a part of cold heat is collected, the thermal efficiency of the gas reliquefaction apparatus 1 can be improved.

The methane-rich gas sent through the methane-rich gas pipe 19 is decompressed by the decompression valve 23 so as to substantially match the pressure in the storage tank 9.
The decompressed methane rich gas is injected from the distributor 25 toward the liquid level 27 of the LNG 2.
When the tip of the distributor 25 is substantially coincident with the liquid level 27 as shown in FIG. 1, the methane-rich gas is blown into the LNG 2 to form a contact surface where the methane-rich gas and the LNG 2 are in contact with each other.

When the tip of the distributor 25 is above the liquid level 27 as shown in FIG. 2, the methane rich gas is ejected so as to spread toward the LNG 2 and comes into contact with the liquid level 27, so that the methane rich gas and the LNG 2, that is, A contact surface with which gas and liquid come into contact is formed.
Since the components try to equilibrate at the contact surface in contact with this gas-liquid, the nitrogen contained in LNG2 moves to the methane-rich gas formed of methane containing almost no nitrogen, and gasification, that is, evaporation. Become.
When this nitrogen evaporates, the ambient temperature is lowered by the latent heat of vaporization, so that the storage tank 9 can be cooled.

As described above, when the inside of the storage tank 9 is cooled, the total amount of heat that enters the storage tank 9 and heats the LNG 2 is reduced, so that the amount of boil-off gas generated can be reduced.
When the amount of boil-off gas generated is reduced, the total amount of gas liquefied by the gas reliquefaction apparatus 1 is reduced, so that the amount of cold heat necessary for liquefying them can be reduced.
Thereby, since the amount of cold heat generated by the refrigeration cycle unit 5 can be reduced, the power of the refrigeration compressor 33 and the like can be reduced, and the reliquefaction efficiency of the gas reliquefaction apparatus 1 can be improved. Further, since nitrogen, which has been considered to be a disadvantage, is effectively used as a cold heat source, it is possible to provide a way to actively utilize LNG2 containing a large amount of nitrogen.

  Thus, when nitrogen contained in the vicinity of the liquid surface 27 of LNG2 is selectively evaporated, the nitrogen content in this portion is reduced, but the effect of equilibrating so as to be uniform in the liquid phase LNG2, or The LNG 2 is circulated by the spray line 20 using the transfer pump 8 in the storage tank 9, so that nitrogen in other parts moves to the vicinity of the liquid level 27. Thereby, since the content rate of nitrogen in the vicinity of the liquid surface 27 does not rapidly decrease, the above-described cooling effect can be maintained until the total amount of nitrogen is considerably reduced.

Further, since the methane-rich gas is supplied to a wide range of the liquid surface 27 by the distributor 25, a contact area between the methane-rich gas and the LNG 2 is formed wide, and nitrogen can be efficiently evaporated.
Note that the distributor 25 may not be used in some cases, as long as the methane-rich gas and the LNG 2 can be brought into contact with each other.

Moreover, in order to evaporate the nitrogen in LNG2 and to obtain latent heat, it is necessary for methane rich gas to maintain gas. In this sense, in this embodiment, it is preferable to control the methane-rich gas to a low humidity saturated state or an overheated state so as not to easily liquefy.
For example, the methane-rich gas pipe 19 may be configured as indicated by a two-dot chain line in FIG.
In this case, methane rich gas may be injected in a gas-liquid mixed state depending on the control situation.

The gas component at a low temperature (saturation temperature under the separator pressure, for example, −150 ° C.) accumulated in the upper portion of the separator 11 is discharged to the outside, for example, a gas combustion boiler or the like through the condensing part G by the off-gas piping 29.
Since this gas component contains a large amount of nitrogen, the nitrogen evaporated in the storage tank 9 can be efficiently discharged to the outside.
In addition, since a large amount of nitrogen is evaporated in the storage tank 9, the nitrogen contained in the LNG 2 can be discharged earlier than usual. For this reason, since only methane is reliquefied quickly, the power required for reliquefaction can be reduced. Moreover, LNG2 with few impurities can be delivered to the receiving base.

  The low-temperature gas component sent through the off-gas pipe 29 is warmed by the boil-off gas being condensed passing through the boil-off gas supply pipe 13 when passing through the condensing part G. On the other hand, the boil-off gas in the boil-off gas supply pipe 13 is cooled by the gas flowing through the off-gas pipe 29, so that the cold heat of the gas is used for condensing the boil-off gas. Therefore, since a part of cold heat is collected, the thermal efficiency of the gas reliquefaction apparatus 1 can be improved.

In addition, this invention is not limited to this embodiment, In the range which does not deviate from the summary of this invention, it can change suitably.
For example, although this embodiment is applied to the reliquefied gas apparatus 1 mounted on the LNG ship, it may be applied to the reliquefied gas apparatus 1 used for the LNG tank installed on land.
Moreover, as liquefied gas, not only LNG but appropriate things, such as LPG, can be made into object.

It is a block diagram which shows schematic structure of the gas reliquefaction apparatus of 1st embodiment of this invention. It is a fragmentary sectional view which shows the positional relationship with the liquid level of the distributor of 1st embodiment of this invention.

Explanation of symbols

1 Gas reliquefaction device 2 LNG
7 Liquidizer 9 Storage tank 11 Separator 17 Boil-off gas compressor 19 Methane rich gas piping 25 Distributor 27 Liquid level

Claims (5)

A compressor for introducing and compressing boil-off gas evaporated in a storage tank for storing a liquefied gas containing an impurity component having a lower boiling point;
A heat exchanger for cooling and condensing the boil-off gas compressed by the compressor;
A gas-liquid separator that separates the condensed fluid condensed in the heat exchanger into a gas and a liquid;
A gas re-liquefaction device that recirculates the liquid separated by the gas-liquid separator to the inside of the liquefied gas and discharges the gas to the outside,
A gas reliquefaction apparatus comprising supply means for gasifying a part of the liquid and supplying it to the vicinity of the liquid level of the liquefied gas.   2. The gas reliquefaction apparatus according to claim 1, wherein the supply means is configured to supply the gasified liquid to a liquid level of the storage tank over a wide range.   2. The gasification of the liquid in the supply means is performed using a heat quantity of the boil-off gas condensed in the heat exchanger, and the boil-off gas side is precooled at that time. Or the gas reliquefaction apparatus of 2.   The liquefied gas reliquefaction apparatus according to any one of claims 1 to 3, wherein the gas discharged from the gas-liquid separator is configured to pass through the heat exchanger. Remove and compress the boil-off gas that has evaporated in the storage tank that stores the liquefied gas containing the impurity component having a lower boiling point,
Cooling and condensing the compressed boil-off gas,
Separating condensed condensed fluid into gas and liquid,
A gas reliquefaction method for recirculating the separated liquid to the inside of the liquefied gas and discharging the gas to the outside,
A gas reliquefaction method characterized in that a part of the liquid is gasified and supplied to the vicinity of the liquid level of the liquefied gas.

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