JP2009204026A - Liquefied gas storage facility and ship or marine structure using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquefied gas storage facility capable of reducing the whole required motive power, by eliminating an evaporation loss in liquefied gas. <P>SOLUTION: This liquefied gas storage facility has a storage tank 3 for storing LNG 11, a reliquefying device 5 for returning reliquefied LNG to the storage tank 3 after taking out and reliquefying boil-off gas 13 evaporated in the storage tank 3, and a regasification plant 7 used by gasifying after increasing pressure of the LNG 11 taken out of the inside of the storage tank 3, and is characterized in that cold of the LNG in the regasification plant 7 can be used as a cold source of the reliquefying device 5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquefied gas storage facility and a ship or marine structure using the same.

Some recent liquefied natural gas (LNG) carriers (LNG ships) include, for example, a regasification plant that regasifies LNG using power in the ship as disclosed in Patent Document 1. . For example, when the LNG receiving terminal is not provided on land, the LNG ship regasifies LNG on the ship and directly supplies it to the land gas piping.
In order to send out the regasified natural gas through the gas pipe, it is necessary to set the pressure of the natural gas to a high pressure state of about 10 MPa (100 bar), for example.

For this reason, the regasification plant takes out the LNG in the storage tank, pressurizes it to a predetermined pressure by pumping in a liquid state, and then heats the pressurized LNG to gasify it.
Moreover, as a heat source which gasifies, there exist some which use seawater as shown by patent document 1, or what uses inboard steam.

Moreover, LNG stored in the storage tank in a substantially atmospheric pressure state is evaporated by heat input into the storage tank, and accumulates in the storage tank as boil-off gas. As a result, the pressure in the storage tank increases, and it is necessary to continuously extract a part of the pressure.
Even during regasification, the volume of the generated boil-off gas is generally larger than the volume of LNG removed from the storage tank, so it is the same for maintaining the internal pressure of the storage tank. It is necessary to process.

As this treatment, for example, boil-off gas may be compressed and directly supplied to the gas piping on land as high-pressure gas. However, in order to compress the gas to high pressure, a large-scale compressor such as a multistage compressor may be used. A compression facility is required, and a large amount of power is required to operate it, which is not only inferior to initial investment, but also disadvantageous in terms of operation costs. Even if it can be implemented, it is too expensive.
In addition, there is a fuel that is used as a fuel for a boiler that requires a low pressure and uses steam generated by the boiler as a heating source for heating LNG in a ship or a regasification plant.
Furthermore, as shown in Patent Document 2, it has also been proposed to reliquefy the boil-off gas and return it to the storage tank.

Special Table 2002-506960 JP 2005-265170 A

By the way, if the boil-off gas is used as the fuel for the boiler and the generated steam is used as a heating source for the LNG, the heat cycle is inefficient and the cold energy is not effectively utilized. Further, when the amount of boil-off gas exceeds the required heat amount, the surplus boil-off gas is discarded. Furthermore, the supply amount of natural gas is reduced by the amount of the boil-off gas that has been processed.
In the reliquefaction shown in Patent Document 2, there is no decrease in the natural gas supply amount due to evaporation loss, but power for liquefying the boil-off gas is required.
For regasification plants that require high pressure natural gas, an overall efficient system is required along with boil-off gas treatment.

  In view of the above, an object of the present invention is to provide a liquefied gas storage facility that can eliminate the loss of evaporation of liquefied gas and reduce the total required power, and a ship or an ocean structure using the liquefied gas storage facility.

In order to solve the above problems, the present invention employs the following means.
That is, the liquefied gas storage facility according to the present invention includes a storage tank for storing the liquefied gas, a boil-off gas evaporated in the storage tank, re-liquefied, and then returned to the storage tank. A liquefaction plant; and a regasification plant that is used after gasification after increasing the pressure of the liquefied gas taken out from the storage tank, and the regasification plant is used as a cooling heat source of the reliquefaction plant. The cold heat of the liquefied gas in is usable.

The reliquefaction plant takes out the boil-off gas evaporated in the storage tank from the storage tank, and compresses and cools it as necessary to reliquefy. The reliquefied liquefied gas is returned to the storage tank.
Thus, since the boil-off gas evaporated in the storage tank is reliquefied by the reliquefaction plant and returned to the storage tank, loss due to evaporation of the liquefied gas can be prevented.
In the regasification plant, the pressure of the liquefied gas taken out from the storage tank is increased by a pump in a liquid state, so that the liquefied gas can be boosted with a simple device and extremely little power consumption. Therefore, high-pressure gas can be generated efficiently. Since the generated gas is high pressure, it can be directly supplied to the gas piping on land, or can be directly supplied as fuel to a high-efficiency high-pressure gas injection type gas-fired diesel engine generator or the like. It can be supplied directly as fuel for onshore gas piping or high-pressure gas injection type gas-fired diesel engines.

At the same time, part of the heat source required by the regasification plant can be used as the cooling heat source of the reliquefaction plant. The gas will be cooled. In other words, the reliquefaction plant boil-off gas is cooled by the regasification plant liquefied gas, while the regasification plant liquefied gas is heated by the amount of heat of the reliquefaction plant boil-off gas, so The cooling power and the heating power for the regasification plant can be reduced, respectively.
The “liquefied gas” is preferably liquefied natural gas (LNG), liquefied petroleum gas (LPG), or the like.

  In addition, the liquefied gas storage facility according to the present invention is provided in the reliquefaction plant, and compresses the refrigerant while it is circulated along the refrigerant flow path, cools and then expands to a lower temperature state, A refrigeration cycle section that cools boil-off gas, a diversion channel that selectively diverts the refrigerant before being expanded in the refrigerant channel, the refrigerant that flows through the diversion channel, and the liquefaction of the regasification plant A heat exchanger that exchanges heat with the gas and condenses the refrigerant by the cold of the liquefied gas, and a low-temperature gaseous refrigerant generated by expanding the refrigerant condensed in the heat exchanger. And a merging channel that joins the low-temperature gaseous refrigerant after expansion in the refrigerant channel.

In the refrigeration cycle section, the refrigerant is circulated along the refrigerant flow path. While flowing along this refrigerant flow path, the refrigerant is compressed to a high temperature and high pressure, and then cooled by a lower temperature medium to a low temperature and high pressure state. The refrigerant that has been subjected to this at least once is expanded to be in a low pressure state and at a lower temperature.
This low-pressure, low-temperature refrigerant cools and liquefies the boil-off gas taken out from the storage tank. On the other hand, the refrigerant is heated by the boil-off gas, heated up, and returned to the compression process.

In the present invention, for example, when the regasification plant is operating, the refrigerant before being expanded in the refrigerant flow path is diverted by the diversion flow path. The branched refrigerant flowing through the diversion flow channel flows into the heat exchanger, where it is heat-exchanged with the liquefied gas flowing through the regasification plant and condensed. The condensed refrigerant is expanded and reduced in pressure and temperature. And the gas part of this refrigerant | coolant is made to merge with the refrigerant | coolant flow path after expansion | swelling through a confluence | merging flow path.
Thus, the refrigerant heated by the heat quantity of the boil-off gas is cooled by the cold heat of the liquefied gas flowing through the regasification plant. On the other hand, the liquefied gas flowing through the regasification plant is heated by the heat quantity of the boil-off gas through the refrigerant.
Therefore, the cooling power of the reliquefaction plant and the heating power of the regasification plant can be reduced, respectively.

  The liquefied gas storage facility according to the present invention includes an expansion member that expands the liquid refrigerant in the merging channel, and a gas-liquid separation that separates the refrigerant expanded and cooled by the expansion member into gas and liquid. And a vessel.

  When the liquid refrigerant is expanded, the temperature is lowered and the gaseous refrigerant and the liquid refrigerant are mixed. Since this is separated into gas and liquid by the gas-liquid separator, the gaseous refrigerant can be reliably joined to the refrigerant flow path.

Moreover, in the said invention, it is suitable for the storage container which stores the liquid refrigerant | coolant after the expansion formed in the said confluence | merging flow path.
If it does in this way, it can prevent that a liquid refrigerant accumulates in a gas-liquid separator too much, and it stops functioning.

  Further, the liquefied gas storage facility according to the invention is characterized in that a supply flow path for supplying the liquid refrigerant stored in the storage container to the heat exchanger is provided.

Since the liquid refrigerant stored in the storage container is expanded by the expansion member and the temperature is lowered, the refrigerant flowing through the branch flow path can be cooled and condensed. Thus, since the amount of cold heat in the heat exchanger increases, the amount of refrigerant branched into the diversion channel can be increased. As a result, the power for circulating the refrigerant in the refrigerant flow path can be further reduced.
In addition, if a sufficient amount of the liquid refrigerant can be ensured, the refrigerant diverted to the diversion channel can be sufficiently condensed by the amount of cold heat generated by the liquid refrigerant. In this way, for example, even if the operation of the regasification plant is stopped and the cold heat of the liquefied gas disappears, the power for circulating the refrigerant in the refrigerant flow path can be reduced.

  In the liquefied gas storage facility according to the invention, the reliquefaction plant is configured to reliquefy all boil-off gas taken out from the storage tank.

The reliquefaction plant takes out of the storage tank and reliquefies all the boil-off gas. Since the reliquefied liquefied gas is returned to the storage tank, loss due to evaporation of the liquefied gas can be prevented.
The necessary gas will be provided by regasifying the liquefied gas in the storage tank using a regasification plant. This gas is generally required to have a high pressure.
In the regasification plant, the pressure of the liquefied gas taken out from the storage tank is increased by a pump in a liquid state. Therefore, the liquefied gas can be boosted with a simple device with extremely little power consumption. Therefore, high-pressure gas can be generated efficiently.
As described above, the boil-off gas in a substantially atmospheric pressure state is not compressed for purposes other than reliquefaction, and the heat quantity is effectively utilized between the reliquefaction plant and the regasification plant. realizable.

  The ship according to the present invention prevents loss due to evaporation of the liquefied gas, can efficiently generate high-pressure gas, and can reduce the cooling power of the reliquefaction plant and the heating power of the regasification plant, respectively. It is equipped with storage equipment.

  According to the ship of the present invention, the transported liquefied gas can be utilized without loss. Moreover, since high-pressure gas can be generated efficiently, the gas can be supplied directly to the land gas piping. For example, a high-efficiency, high-pressure gas-injection gas-fired diesel engine generator or the like can be employed as the main engine or onboard power source.

  The offshore structure according to the present invention can prevent loss due to evaporation of liquefied gas, can efficiently generate high-pressure gas, and can reduce cooling power of the reliquefaction plant and heating power of the regasification plant, respectively. It is equipped with a liquefied gas storage facility.

  The offshore structure of the present invention can utilize, for example, liquefied gas supplied from a ship without loss. Moreover, since high-pressure gas can be generated efficiently, the gas can be supplied directly to the land gas piping. As the internal power source, a high efficiency, for example, a high pressure gas injection type gas fired diesel engine generator or the like can be adopted.

Thus, since the boil-off gas evaporated in the storage tank is reliquefied by the reliquefaction plant and returned to the storage tank, loss due to evaporation of the liquefied gas can be prevented.
The regasification plant raises the pressure of the liquefied gas taken out from the storage tank, so it can be supplied directly to the gas piping on land, and the high-pressure gas injection type gas-fired diesel engine generator, etc. with high efficiency Can be supplied as fuel.
And since the cold heat of the liquefied gas in the regasification plant can be used as the cold heat source of the reliquefaction plant, the cooling power of the reliquefaction plant and the heating power of the regasification plant can be reduced. .

Hereinafter, an embodiment in which the present invention is applied to a liquefied gas storage facility of an LNG ship will be described with reference to FIG.
FIG. 1 is a block diagram showing an overall schematic configuration of a liquefied gas storage facility 1 of an LNG ship.
The liquefied gas storage facility 1 takes out a storage tank 3 for storing a liquefied natural gas (liquefied gas: LNG) 11 containing methane as a main component, and a boil-off gas 13 evaporated in the storage tank 3 and reinjects it. A gas reliquefaction device 5 that liquefies, a regasification plant 7 that takes out the LNG 11 in the storage tank 3 and gasifies it into high-pressure natural gas, and a heat exchange unit 9 are provided.

There are various types of storage tanks 3, for example, a moss-type tank has a substantially spherical shape as shown in FIG.
The storage tank 3 has a heat insulating structure, and the LNG 11 is stored therein at a substantially atmospheric pressure. The boiling point of methane, which is the main component of the stored LNG 11 in this state, is about −161 ° C., but since heat enters the storage tank 3 from the outside and warms the LNG 11, the LNG 11 evaporates and boil-offs into the upper space. Gas 13 is produced.

The gas reliquefaction apparatus 3 includes a refrigeration cycle unit 15 and a liquefaction processing unit 17.
The refrigeration cycle unit 15 supplies cold heat of the refrigerant circulated through the refrigeration pipe (refrigerant flow path) 19 to the liquefaction processing unit 17. For example, nitrogen (N ₂ ) is used as the refrigerant. Other examples include hydrogen and helium.
The refrigeration cycle unit 15 includes a refrigerant compressor 21, a drive motor 23 that drives the refrigerant compressor 21, a first aftercooler 25, a booster compressor 27, a second aftercooler 29, an expander 31, and a supercooler. 33, the condenser 35, and the precooler 37 are provided as main elements.

The refrigeration cycle section 15 is provided with a refrigeration pipe 19 that forms a closed system by connecting these elements.
The refrigeration pipe 19 is connected to the compression cooling unit 39 from the refrigerant compressor 21 via the first aftercooler 25 to the booster compressor 27, the booster compressor 27, the second aftercooler 29, the precooler 37 and the condenser 35. A pre-cooling piping section 41 that enters the expander 31 and a cooling piping section 43 that enters the refrigerant compressor 21 via the expander 31, the supercooler 33, the condenser 35, and the precooler 37 are provided.

The refrigerant compressor 21 sucks and compresses a low-temperature / low-pressure gaseous (gaseous) refrigerant to form a high-temperature / high-pressure gaseous refrigerant.
The first aftercooler 25 cools the high-temperature and high-pressure gaseous refrigerant sent out from the refrigerant compressor 21.
The booster compressor 27 compresses the refrigerant introduced from the first aftercooler 25, changes the refrigerant to a high temperature and high pressure again, and supplies the refrigerant to the precooling piping section 41.

The second aftercooler 29 cools the high-temperature and high-pressure gaseous refrigerant sent out from the booster compressor 27.
The expander 31 expands the refrigerant whose temperature has been lowered through the second aftercooler 29, the precooler 37, and the condenser 35 by decompression to form a low-temperature and low-pressure gaseous refrigerant. Expander 31 The booster compressor 27 is rotated with the force when the refrigerant is expanded as a rotational force.
The low-temperature and low-pressure gaseous refrigerant from the expander 31 is sequentially sent to the supercooler 33, the condenser 35, and the precooler 37 through the cooling pipe portion 43 to exchange heat.

A branch portion A is provided between the first aftercooler 25 of the compression cooling unit 39 and the booster compressor 27. A first bypass passage 45 is provided between the precooling pipe portion 41 between the second aftercooler 29 and the precooler 37 and the branch portion A.
The first bypass passage 45 is provided with a check valve 47 that prevents the refrigerant from flowing from the precooling pipe section 41 to the compression cooling section 39 and selectively allows the refrigerant to flow in the reverse direction.
A second bypass channel 49 is provided between the precooling pipe 41 between the condenser 35 and the expander 31 and the cooling pipe 43 between the supercooler 33 and the condenser 35. ing.
The second bypass channel 49 is provided with a flow rate adjustment valve 51.
These are provided to form a flow path that bypasses the booster compressor 27 and the expander 31 when the refrigeration cycle unit 15 is started.

The liquefaction processing unit 17 is provided with a boil-off gas supply pipe 55 that conveys the boil-off gas 13 from the storage tank 3 to the separator 53, and a reliquefied gas pipe 57 that sends the re-liquefied gas from the separator 53 to the storage tank 3. .
The boil-off gas supply pipe 55 is provided with a moderate heat generator 59 that lowers the temperature of the boil-off gas 13 and a boil-off gas compressor 61 that compresses the boil-off gas 13 being conveyed.

The slow heatr 59 was mixed with low temperature gaseous natural gas and / or liquefied LNG sent from the separator 53 and the boil-off gas 13 sent from the storage tank 3 to lower the temperature. The boil-off gas 13 is sent to the boil-off gas compressor 61.
The boil-off gas compressor 61 compresses the boil-off gas 13 sent from the slow heat generator 59 to a high temperature and a high pressure.
The amount of gaseous natural gas and / or liquefied LNG is adjusted so that the temperature of the boil-off gas 13 introduced into the boil-off gas compressor 61 is constant.

The boil-off gas supply pipe 55 exits the boil-off gas compressor 61, passes through the condenser 35, and is connected to the upper portion of the separator 33.
The boil-off gas 13 is cooled and condensed by a cool gaseous refrigerant flowing through the cooling pipe 43 in the condenser 35.
The separator 53 has a function of separating the gas-liquid of the boil-off gas 13 condensed by the condenser 35 using a difference in weight.

The reliquefied gas pipe 57 is connected to the storage tank 3 from the lower part of the separator 53 through the supercooler 33. The reliquefied gas pipe 57 is provided with a reliquefied gas flow rate adjustment valve 63 on the downstream side of the supercooler 33.
The reliquefied gas flow rate adjustment valve 37 adjusts the liquid level of the separator 53 so as to be in a predetermined range.

  The regasification plant 7 includes a first container 65 that stores LNG 11, a second container 67 that stores LNG 11, a vaporizer (not shown), and a first LNG pipe that connects the inside of the storage tank 3 and the first container 65. 69, the second LNG pipe 71 connecting the first container 65 and the second container 67, the third LNG pipe 73 connecting the second container 67 and the vaporizer, and the first LNG installed in the storage tank 3. A liquefied gas transfer pump 75 for sending LNG to the first container 65 through the pipe 69, a pre-pump 77 installed in the first container 65 and for sending LNG to the second container 67 through the second LNG pipe 71, and the second container 67, and a booster pump 79 that sends LNG through a third LNG pipe 73.

The liquefied gas transfer pump 75 delivers LNG at a pressure of 0.3 to 0.4 MPa (3 to 4 bar).
The pre-pump 77 sends out LNG at a pressure sufficient to maintain the LNG state even when the temperature is raised by heat exchange with the refrigerant described later, for example, 1 MPa (10 bar).
The booster pump 79 sends out LNG at a pressure at which the natural gas gasified by the vaporizer becomes a required pressure. This required pressure is, for example, 10 to 12 MPa (100 to 120 bar) when supplying directly to a gas line on land, and 20 to 20 when using as a fuel for a high pressure gas injection type gas-fired diesel engine, for example. 30 MPa (200-300 bar).

The heat exchanging unit 9 includes a heat exchanger 81, an expansion valve 83, a gas-liquid separator 85, a storage container 87, a refrigerant diversion pipe (diversion flow path) 89, and a refrigerant confluence pipe (confluence flow path) 91. And a refrigerant storage pipe 93 and a refrigerant supply pipe (supply flow path) 95.
The heat exchanger 81 is a hollow sealed container, and the second LNG pipe 71 is passed through the inside.
The refrigerant distribution pipe 89 is a pipe that connects the branch part A of the compression cooling part 39 and the upper part of the heat exchanger 81 through the precooler 37 and the condenser 35, and a refrigerant flow rate adjustment valve 97 is installed on the way. Has been. The refrigerant distribution pipe 89 has a function of sending the refrigerant compressed by the refrigerant compressor 21 and cooled by the first aftercooler 25 to the heat exchanger 81.

A merging portion B is set in the cooling pipe 43 located between the expander 31 and the subcooler 33. The refrigerant junction pipe 91 is a pipe that connects the lower part inside the heat exchanger 81 and the junction B. An expansion valve (expansion member) 83 and a gas-liquid separator 85 are provided in the middle of the refrigerant junction pipe 91 in this order from the heat exchanger 81 side.
The expansion valve 83 has a Joule-Thompson effect and has a function of adiabatic expansion of the refrigerant condensed in the heat exchanger 81 to bring it into a low-temperature gas-liquid state. The pressure at the outlet of the expansion valve 83 is configured to be substantially equal to the pressure at the outlet of the expander 31.

The refrigerant storage pipe 93 is a pipe that connects the lower part of the gas-liquid separator 85 and the storage container 87.
The refrigerant supply pipe 95 is a pipe that connects the inside lower part of the storage container 87 and the inside of the heat exchanger 81. A pump 99 is installed in the middle of the refrigerant supply pipe 95.
A pipe connecting the storage container 87 and the refrigerant supply pipe 95 is provided with a heater 101 including an air pipe through which air passes.

Operation | movement of the gas storage installation 1 concerning this embodiment demonstrated above is demonstrated.
First, the case where the regasification plant 7 is not operating will be described. At this time, the refrigerant flow rate adjustment valve 97 is closed so that the refrigerant does not flow into the refrigerant distribution pipe 89.
In the refrigeration cycle unit 15, the refrigerant compressor 21 is driven by the drive motor 23 to compress the low-temperature / low-pressure gaseous refrigerant introduced from the refrigeration pipe 19 into a high-temperature / high-pressure gaseous refrigerant.
This high-temperature and high-pressure gaseous refrigerant is cooled by the first aftercooler 25 and introduced into the booster compressor 27. In the booster compressor 27, the introduced high-temperature and high-pressure gaseous refrigerant is compressed to a higher temperature and pressure. This refrigerant is sent to the preliminary cooling pipe section 41, cooled by the second aftercooler 29, and then cooled by the low-temperature and low-pressure gaseous refrigerant passing through the cooling pipe section 43 when passing through the precooler 37 and the condenser 35. Introduced into the expander 31.

The refrigerant introduced into the expander 31 is expanded by decompression to be a low-temperature and low-pressure gaseous refrigerant. And this low-temperature and low-pressure gaseous refrigerant is sent to the cooling piping part 43, and when passing through the subcooler 33, the condenser 35 and the precooler 37, it cools by giving the cold to the circumference.
Thereafter, the refrigerant is sent to the refrigerant compressor 21 to complete one cycle.
In the refrigeration cycle unit 15, by continuously performing this cycle, the supercooler 33, the condenser 35, and the precooler 13 through which the cooling pipe unit 43 passes provide cold heat.

The boil-off gas 13 sent from the storage tank 3 is adjusted so as to have a low predetermined temperature by the slow heat generator 59, then compressed by the boil-off gas compressor 61 and sent by the boil-off gas supply pipe 55 in a high temperature / high pressure state. .
In the condenser 35, the boil-off gas 13 is cooled by the low-temperature and low-pressure gaseous refrigerant flowing through the cooling piping unit 43 of the refrigeration cycle unit 15, and is separated in a saturated liquid state, that is, in a state where it is easily separated into gas and liquid. Sent to. That is, the low-pressure and low-temperature refrigerant cools and liquefies the boil-off gas taken out from the storage tank 3. On the contrary, the refrigerant is heated by the boil-off gas 13, heated up, and returned to the refrigerant compressor 21.

In the separator 53, the boil-off gas 13 in a saturated liquid state is gas-liquid separated, and the liquid component, that is, the reliquefied gas is separated at the lower part, and the gas component is separated at the upper part.
The reliquefied gas accumulated in the lower part of the separator 53 is sent through the reliquefied gas pipe 57 and is supercooled by the refrigerant passing through the cooling pipe section 43 of the refrigeration cycle section 15 in the supercooler 33 (for example, −162.5). ℃) and returned to the storage tank. Further, a part is sent to the slow heat generator 59 in order to adjust the temperature of the boil-off gas 13.

  A low-temperature (for example, −150 ° C.) gas component accumulated in the upper portion of the separator 33 is sent to a slow heat generator 59 to adjust the temperature of the boil-off gas 13, and a part thereof is, for example, a fuel such as a boiler. Is done.

  Thus, since the boil-off gas 13 evaporated in the storage tank 3 is reliquefied by the reliquefaction device 5 and returned to the storage tank 3, loss due to evaporation of the LNG 11 can be prevented.

Next, for example, a case where an LNG ship arrives at a place where natural gas is used and the regasification plant 7 is operated to supply natural gas directly to the pipeline on the ground will be described.
The liquefied gas transfer pump 75 sends out the LNG 11 stored in the storage tank 3 at substantially atmospheric pressure to the first container 65 through the first LNG pipe 69 at a pressure of 0.3 to 0.4 MPa (3 to 4 bar). .
The LNG 11 is stored in the first container 65 in a state where the pressure has returned to substantially atmospheric pressure due to an intermediate pressure loss.
The LNG 11 is pressurized to, for example, 1 MPa (10 bar) by the pre-pump 77 and is transported to the second container 67 through the second LNG pipe 71. At this time, the temperature of the LNG 11 is, for example, −160 ° C.

In order to keep the temperature of the condensed refrigerant at this level, it is necessary to keep the pressure at the junction B at a low pressure (for example, 0.4 to 0.6 MPa (4 to 6 bar)).
If the cold supply of the refrigerant junction pipe 91 increases, the burden on the refrigerant compressor 21 decreases, and the pressure at the junction B increases.
On the other hand, when the amount stored as liquid in the heat exchange unit 9 or the storage container 87 increases, the pressure in the junction B may decrease. Therefore, it is necessary to adjust the pressure by the supply / extraction line connected to the refrigerant storage tank 40.

On the other hand, the refrigerant flow rate adjustment valve 97 is opened, and the adjusted amount of the refrigerant flows from the branch portion A to the refrigerant distribution pipe 89 and is sent to the heat exchanger 81. The temperature of this refrigerant is, for example, −110 ° C.
Since the second LNG pipe 71 is inserted into the heat exchanger 81, the refrigerant flowing into the heat exchanger 81 is cooled and condensed by the LNG 11 flowing through the second LNG pipe 71. At this time, the temperature of the condensed refrigerant is, for example, −150 to −160 ° C.

The condensed refrigerant flows into the refrigerant joining pipe 91, is expanded by the expansion valve 83, and is reduced in pressure and temperature. The saturation temperature under this portion of pressure, for example, −170 ° C. is sent to the gas-liquid separator 85.
In the gas-liquid separator 85, it is separated into a gaseous refrigerant and a liquid refrigerant by weight. The gaseous refrigerant occupying the upper part of the gas-liquid separator 85 is sent to the junction B through the junction refrigerant pipe 91 and merged with the refrigerant having the substantially same temperature expanded by the expander 31.
The low-temperature refrigerant cools and condenses the boil-off gas 13 flowing through the boil-off gas supply pipe 55 in the condenser 35. On the other hand, the refrigerant is heated by the boil-off gas 13.

Thus, when the refrigerant from the refrigerant junction pipe 91 is added, the supply amount of the refrigerant by the expander 31 can be reduced. Thereby, since the refrigerant | coolant which passes through the expander 31 reduces relatively, the load of the expander 31 reduces. When the load on the expander 31 decreases, the load on the refrigerant compressor 21 that circulates the refrigerant decreases, so that the power of the drive motor 23 that drives the refrigerant compressor 21 can be reduced.
That is, the cooling power of the reliquefaction device 5 can be reduced.

The liquid refrigerant stored in the lower part of the gas-liquid separator 85 is sent to the storage container 87 through the refrigerant storage pipe 93 and stored.
When a predetermined amount or more is stored in the storage container 87, the stored liquid refrigerant is supplied to the heat exchanger 81 through the refrigerant supply pipe 95 by the pump 99.
Since the liquid refrigerant stored in the storage container 87 is expanded by the expansion valve 83 and is cooled, the refrigerant flowing through the refrigerant distribution pipe 89 can be cooled and condensed.

Thus, since the amount of cold heat in the heat exchanger 81 is increased, the amount of refrigerant diverted to the refrigerant diversion pipe 89 can be increased. Thereby, the power which circulates the refrigerant | coolant in the refrigerant | coolant cycle part 15 can be reduced further.
Further, if a sufficient amount of the liquid refrigerant can be secured, the refrigerant diverted to the refrigerant distribution pipe 89 can be sufficiently condensed by the amount of heat generated by the liquid refrigerant. For example, the regasification plant 7 Even if the operation of the LNG is stopped and the cold heat of the LNG disappears, the power for circulating the refrigerant in the refrigerant cycle unit 15 can be reduced.

On the other hand, the LNG passing through the second LNG pipe 71 is heated by the refrigerant flowing from the refrigerant distribution pipe 89 and is heated. At this time, the pre-pump 77 increases the pressure of the LNG 11 to such an extent that the LNG is not gasified even if the temperature is raised by the heat exchanger 81.
The LNG 11 flows into the second container 67 from the second LNG pipe 71 and is stored.
The LNG 11 stored in the second LNG container 67 is boosted to, for example, 10 MPa (100 bar) by the booster pump 79 and is transported to the vaporizer.
The LNG 11 is heated by a heat source provided separately in the vaporizer and gasified into natural gas. The gasified natural gas will be supplied to the above-ground pipeline.

Thus, since the regasification plant 7 raises the pressure of the LNG 11 taken out from the storage tank 3 by pumping, the LNG 11 can be easily boosted with a simple device.
Therefore, high-pressure gas can be generated efficiently and reliably.

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 gas storage facility 1 mounted on an LNG ship, it may be installed in a floating or fixed offshore structure, or installed on land. Also good.
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 one Embodiment of this invention.

Explanation of symbols

1 Gas storage equipment 3 Storage tank 5 Reliquefaction device 7 Regasification plant 11 LNG
13 Boil-off gas 15 Refrigeration cycle section 17 Liquefaction processing section 81 Heat exchanger 83 Expansion valve 85 Gas-liquid separator 87 Storage container 89 Refrigerant branch pipe 91 Refrigerant merge pipe 95 Refrigerant supply pipe

Claims (8)

A storage tank for storing liquefied gas;
A reliquefaction plant that takes out the boil-off gas evaporated in the storage tank and reliquefies it, and then returns the reliquefied liquefied gas to the storage tank;
A regasification plant for use after gasification after increasing the pressure of the liquefied gas taken out from the storage tank,
The liquefied gas storage facility characterized in that the chilled heat of the liquefied gas in the regasification plant can be used as a cold heat source of the reliquefaction plant. A refrigerating cycle unit that is provided in the reliquefaction plant, compresses the refrigerant while it is circulated along the refrigerant flow path, cools and then expands to a lower temperature state, and cools the boil-off gas;
A diversion channel that selectively diverts the refrigerant before being expanded in the refrigerant channel;
A heat exchanger that exchanges heat between the refrigerant flowing through the diversion flow path and the liquefied gas of the regasification plant, and condenses the refrigerant by cold heat of the liquefied gas;
A merging channel that joins the low-temperature gaseous refrigerant generated by expanding the refrigerant condensed in the heat exchanger to the low-temperature gaseous refrigerant after expansion in the refrigerant channel;
The liquefied gas storage facility according to claim 1, wherein the liquefied gas storage facility is provided. In the confluence channel, an expansion member that expands the liquid refrigerant,
A gas-liquid separator that separates the refrigerant expanded and cooled by the expansion member into gas-liquid; and
The liquefied gas storage facility according to claim 2, wherein the liquefied gas storage facility is provided.   The liquefied gas storage facility according to claim 2 or 3, further comprising a storage container for storing the expanded liquid refrigerant formed in the merging channel.   The liquefied gas storage facility according to claim 4, further comprising a supply flow path for supplying the liquid refrigerant stored in the storage container to the heat exchanger.   6. The liquefied gas storage facility according to claim 1, wherein the reliquefaction plant is configured to reliquefy all boil-off gas extracted from the storage tank. 6. .   A ship equipped with the liquefied gas storage facility according to any one of claims 1 to 6. An offshore structure equipped with the liquefied gas storage facility according to any one of claims 1 to 6.

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