KR102645626B1 - Shipping method of liquefied natural gas - Google Patents

Abstract

Provides technology to address boil-off gas surpluses that arise when shipping liquefied natural gas to a carrier.
When shipping liquefied natural gas from a floating facility (1) disposed on the water and equipped with a liquefaction device (2) for liquefying natural gas to a transport vessel (3), in the introduction quantity reduction process, before starting shipment of the liquefied natural gas. , the amount of natural gas introduced into the liquefaction device 2 is reduced, and in the shipping process, the liquefied natural gas is shipped from the reservoir 110 toward the transport ship 3. In the re-liquefaction process, when liquefied natural gas is shipped, boil-off gas generated on the transport ship 3 side is received into the liquefaction device 2 and re-liquefied.

Description

Shipping method of liquefied natural gas

The present invention relates to a technology for shipping liquefied natural gas from a floating facility placed on the water to a transport ship.

FLNG (Floating LNG) is a facility that liquefies natural gas (NG) produced from an underwater gas field. A floating body such as a ship is placed in the sea near the gas field, and a NG liquefaction device is provided on the floating body. ) A floating body facility called ) is known.

Liquefied Natural Gas (LNG) flowing out from the liquefaction device is stored in a tank provided in the floating body and then shipped toward the consumer via a transport ship such as an LNG tanker.

Part of the LNG shipped from the floating body facility to the transport ship is vaporized due to heat input from the transport ship side, and generates boil-off gas (BOG: Boil Off Gas). After the BOG generated in the transport ship is returned to the floating body facility, it is used as fuel gas or is re-liquefied in a liquefaction device to become LNG. Additionally, excess BOG that exceeds the processing capacity of the liquefaction device may be burned in the flare stack.

However, in some cases, floating equipment is provided in a location visible from inhabited coastal areas, and in some cases, it is required to minimize the opportunity for the flame of the flare stack to grow as small as possible. Additionally, from the viewpoint of environmental impact, it is desirable to suppress combustion of BOG in the flare stack.

Here, Patent Document 1 describes an introduction facility equipped with a gas engine that drives a generator using BOG generated on the storage tank side as fuel when unloading LNG from a transport ship (LNG tanker) to a storage tank provided on the ground. there is.

However, Patent Document 1 does not describe a technique for responding to an increase in the amount of BOG generated in a floating body facility isolated from the surroundings without providing special equipment.

International Publication No. 2015/12890

The present invention has been made against this background and provides a technology for coping with the surplus of BOG generated when shipping liquefied natural gas to a transport vessel.

The shipping method of liquefied natural gas of the present invention is a method of shipping liquefied natural gas from a floating body facility placed on the water to a transport ship,

The floating body facility is provided with a liquefaction device for liquefying natural gas received from the underwater side, and a reservoir for storing the liquefied natural gas liquefied in the liquefaction device,

an introduction amount reduction step of reducing the amount of natural gas introduced into the liquefaction device before starting shipment of the liquefied natural gas;

a shipping process of shipping liquefied natural gas from the reservoir to a transport ship;

When shipping the liquefied natural gas, a re-liquefaction process is included in which boil-off gas generated on the transport ship is received into the liquefaction device and re-liquefied.

The method for shipping liquefied natural gas may have the following features.

(a) In the introduction amount reduction step, the introduction of natural gas is reduced within ±10% of the amount equivalent to the liquefied natural gas obtained by re-liquefying the boil-off gas.

(b) In the shipping step, the shipping flow rate of the liquefied natural gas is adjusted to a value within the range of 3000 to 7500 m3/h.

(c) When carrying out the shipping process, among the boil-off gases received from the transport ship, a larger amount of boil-off gas than the volume of the gas phase space in the reservoir, which increases with the shipment of the liquefied gas, is returned to the reservoir. Including a rotating BOG storage process. During the period of carrying out the BOG storage process, the pressure in the reservoir is raised compared to other periods.

(d) Before starting shipment of the liquefied natural gas, a reservoir pressure reduction step of lowering the pressure within the reservoir to reduce the vapor pressure and temperature of the liquefied natural gas shipped from the reservoir.
The present invention includes a floating body facility that is placed on the water and ships liquefied natural gas to a transport ship, the floating body facility comprising:
A riser that receives natural gas with an adjusted introduction amount from the underwater side,
A liquefaction device for liquefying natural gas received through the riser,
a reservoir for storing liquefied natural gas liquefied in the liquefaction device;
Shipping facilities for shipping the liquefied natural gas stored in the reservoir toward a transport ship;
a boil-off gas introduction line that receives boil-off gas generated on the transport ship side into the liquefaction device when shipping the liquefied natural gas;
Before starting shipment of the liquefied natural gas, an introduction amount reduction step of reducing the amount of natural gas introduced into the liquefaction device, a shipping step of shipping the liquefied natural gas from the reservoir toward a transport ship by the shipping facility, and When shipping liquefied natural gas, the boil-off gas generated on the transport ship side through the boil-off gas introduction line is received into the liquefaction device and a re-liquefaction process is performed.
It is configured to reduce the introduction of natural gas within a range of ±10% of the amount equivalent to the liquefied natural gas obtained by re-liquefying the boil-off gas in the introduction amount reduction step.
In the shipping process, the shipping flow rate of the liquefied natural gas is configured to be adjusted to a value within the range of 3000 to 7500 m3/h.
The boil-off gas introduction line is configured to allow reception of the boil-off gas even in the low water level,
BOG for returning to the reservoir an amount of boil-off gas greater than the volume of the gas phase space in the reservoir, which increases with the shipment of the liquefied natural gas, among the boil-off gas received from the transport ship when performing the shipping process. It is configured to perform a storage process.
Provided with an end flash unit that adjusts the pressure in the reservoir,
During the period in which the BOG storage process is performed, the end flash unit is configured to increase the pressure in the reservoir compared to a period other than the period in which the BOG storage process is performed.
Provided with an end flash unit that adjusts the pressure in the reservoir,
Before starting shipment of the liquefied natural gas, a reservoir pressure reduction process of lowering the pressure within the reservoir is performed by the end flash unit in order to reduce the vapor pressure and temperature of the liquefied natural gas shipped from the reservoir. do.

The present invention reduces the amount of natural gas introduced into the liquefaction device from the underwater side before starting shipment of liquefied natural gas to the transport ship, thereby increasing the processing capacity of the liquefaction device and surplus that cannot be completely processed by the liquefaction device. The amount of BOG generated can be suppressed.

1 is a side view of an FLNG according to an embodiment.
Figure 2 is a top view of the FLNG.
Figure 3 is a block diagram of a liquefaction device provided in the FLNG.
Figure 4 is an explanatory diagram showing the flow of processing performed in the FLNG according to LNG shipment.

First, referring to FIGS. 1 to 3, a configuration example of FLNG 1 to which the LNG shipping method of this example is applied will be described. 1 and 2 are schematic configuration diagrams of the FLNG 1 viewed from the side and top sides, respectively.

As shown in FIG. 2, the FLNG 1 of this example includes a liquefaction device 2, a utility section 202, and a living section 13 on a ship body 11 having a planar shape that is longer in the captain direction than the ship width direction. ) is arranged in a configuration.

At the bow of the hull 11, a turret support portion 123 is provided so as to protrude in the transverse direction toward the front of the bow, and a turret 12 for mooring the hull 11 is installed on the turret support portion 123. there is.

From the turret 12, a plurality of mooring lines 122 are provided to extend downward to moor the hull 11. Additionally, a riser 121 is connected to the turret 12 for underwater transport of NG produced from an underwater gas field. NG received from this riser 121 is supplied to the liquefaction device 2 provided on the ship body 11.

When the bow where the turret 12 is provided is placed on one end side of the hull 11, on the hull 11, there is a liquefaction device 2, a utility section 202, and a residence section ( 13) are arranged in this order.

Here, the liquefaction device 2 is arranged on the ship body 11 with the equipment group included in each section 21 to 26 described later using FIG. 3 divided into a plurality of modules. A module is a division unit configured by embedding part or all of the equipment group included in each part 21 to 26 within a common furniture. Within each module, there are a number of connection pipes, such as static machines such as tower tanks and heat exchangers, synchronous machines such as pumps, and connection pipes that connect between each machine and synchronous machine or between the pipes on the pipe rack section 201 side. A group of devices is deployed. Here, the pipe rack portion 201 is a furniture structure that holds and supports a group of pipes through which various fluids handled within the liquefaction device 2 flow.

In addition, the hull 11 of the FLNG 1 includes a power generation turbine or generator, a power source for the turbine, a boiler that generates steam that becomes the heat source for each distillation column, or a heating system that heats a heat medium such as hot water or hot oil. A group of utility devices is available. In the FLNG 1 of this example, these utility device groups are arranged in organized areas. Hereinafter, the group of utility devices arranged and arranged in the relevant area is referred to as the utility unit 202.

Additionally, the hull 11 is provided with a living area 13 where workers who perform operations of the FLNG 1 etc. reside. For example, the residential area 13 is comprised of a multi-story reinforced concrete building or a steel-framed concrete building.

In addition, a flare stack 14 that burns gas discharged from the FLNG 1 is disposed at the bow of the starboard side of the hull 11, which is furthest from the living area 13.

In addition, as shown in FIG. 2, on the port side of the hull 11, which is opposite to the starboard side where the flare stack 14 is provided, for example, in the central area in the captain's direction of the hull 11, the hull ( 11) A shipping facility 15 is provided for shipping LNG from the reservoir 110 (not shown in FIGS. 1 and 2) formed in the tank toward the LNG tanker (transport ship) 3. The side of the area where the shipping facility 15 is provided becomes the docking position for docking the LNG tanker 3 with respect to the FLNG 1.

Next, referring to FIG. 3, the outline of the liquefaction device 2 will be described. As for NG received from the underwater side through the riser 121, the liquid contained in the NG is separated in the gas-liquid separation unit 21. Next, acid gas (carbon dioxide, hydrogen sulfide, etc.), moisture, and mercury are removed in the pretreatment unit 22.

The natural gas from which impurities have been removed is distilled and separated into methane and heavy hydrocarbons, which are liquid hydrocarbon components with a carbon number of 2 or more, in the distillation unit 23. In addition, in the pretreatment section 22, methane and the separated heavy hydrocarbons having 2 or more carbon atoms are sequentially distilled to obtain ethane, propane, butane, etc. Among the heavy hydrocarbons separated in this way, relatively light fractions with carbon atoms of 4 or less are sometimes reinjected into LNG.

The methane separated in the distillation unit 23 is cooled and liquefied in the liquefaction unit 24 to become liquefied natural gas (LNG). The liquefaction unit 24 has a Main Cryogenic Heat Exchanger (MCHE) for liquefying methane using the main refrigerant (a mixed refrigerant containing methane, ethane, propane, butane, and nitrogen, or a nitrogen refrigerant). It is provided. Additionally, the cryogenic heat exchanger (MCHE) refers to a heat exchanger such as a spiral wound type or cold box type.

The LNG immediately after being liquefied in the liquefaction unit 24 is at a higher pressure and temperature than the storage conditions in the reservoir 110. Therefore, the pressure of LNG is reduced to the pressure of the reservoir 110, and a part of the LNG is vaporized (end flash) to adjust the temperature and the components of the light content. LNG, whose temperature, pressure, and components have been adjusted by the end flash, is supplied to the reservoir 110 provided within the ship body 11, for example.

Additionally, the end flash gas or the gas evaporated from LNG in the reservoir 110 is pressurized as BOG in the boosting unit 26 including a compressor and the like. A part of the BOG is used as fuel gas, and the remainder is returned to the inlet side of the liquefaction unit 24 and re-liquefied. Additionally, the line that receives BOG from the reservoir 110 to the boosting unit 26 can also be used as a line for sending gas returned from the LNG tanker 3 to the reservoir 110. In addition, in the example shown in FIG. 3, the pressure of the end flash gas is boosted in the end flash unit 25, and in some cases, it is combined with the BOG pressurized in the booster unit 26 to obtain fuel gas.

Additionally, excess BOG that exceeds the processing capacity of the liquefaction unit 24 may be burned in the flare stack 14.

In the FLNG 1 having the above-described configuration, the LNG stored in the reservoir 110 is shipped toward the LNG tanker 3.

When shipping LNG, the LNG tanker 3 is docked at the docking position, the shipping facility 15 is connected to the LNG tanker 3, and then the LNG pump 111 provided in the tank 110 is used to pump LNG. The shipment of LNG to the tanker 3 begins.

Here, in normal times when LNG is not shipped, in the reservoir 110, (i) natural heat input to the reservoir 110, (ii) natural heat input to the pipe discharging LNG toward the reservoir 110, (iii) ) BOG is generated using the heat input accompanying the work of the pump (not shown) transporting LNG in the FLNG (1) as the main heat source.

In addition to these, at the time of shipping LNG, (iv) the heat input accompanying the work of the transport pump 111 of the reservoir 110, (v) the shipping piping of LNG or the shipping equipment 15 constituting the shipping facility 15. Natural heat input to the loading arm, (vi) heat input accompanying cooling the wall of the low water tank on the LNG tanker (3) side that has not yet cooled to the liquid temperature of LNG, etc. as the main heat sources, A large amount of BOG occurs within. On the other hand, LNG received from the FLNG 1 flows into the low tank on the side of the LNG tanker 3, and its liquid level rises, causing the BOG in the low tank to be extruded to the outside.

BOG generated in the reservoir on the LNG tanker 3 side and BOG extruded from this reservoir are combined, and the pressure is boosted by a compressor (not shown) provided in the LNG tanker 3 before being sent to the FLNG 1 side. In addition, part of the BOG may be used as fuel for the LNG tanker 3.

As shown in FIG. 3, BOG from the LNG tanker 3 side is conveyed to the FLNG 1 through the previously described shipping facility 15, and joins the BOG generated on the FLNG 1 side.

Therefore, the BOG generated on the LNG tanker 3 side during shipment of LNG is returned to the FLNG 1 and used as fuel gas together with the BOG generated within the FLNG 1 or reliquefied. On the other hand, compared to the BOG generated within the FLNG 1, the amount of BOG returned from the LNG tanker 3 is large, so the entire amount can be reduced simply by increasing the amount of fuel gas used or the amount of re-liquefaction in the liquefaction unit 24. There are cases where it may not be possible to process everything.

BOG that cannot be completely processed is burned in the flare stack (14). However, from the viewpoint of reducing the anxiety associated with the formation of a large flame in the flare stack 14 and suppressing the impact on the environment, there are cases where it is required to suppress the combustion of BOG in the flare stack 14 as much as possible. there is.

A method of reducing the opportunity to burn excess BOG in the flare stack 14 is to predict the re-liquefaction of BOG returned from the LNG tanker 3 and install a liquefaction unit 24 with sufficient processing capacity. A case may be considered, or a case where facilities dedicated to re-liquefaction of BOG may be provided. However, this response is often difficult to adopt because it requires investment in facilities.

Therefore, the FLNG 1 of this example reduces the processing of the BOG conveyed from the LNG tanker 3 in the flare stack 14 by adjusting the operation. Hereinafter, with reference to FIG. 4, the content of the processing performed as a countermeasure for BOG surplus at the time of LNG shipment will be described.

First, in the normal operation state (process P1), the FLNG 1 receives, for example, NG corresponding to the design flow rate of the liquefaction device 2 from the riser 121.

Then, in the preparation stage before the start of shipment of LNG, the opening degree of the choke valve 124 provided on the seabed upstream of the riser 121 is adjusted to reduce the amount of NG introduced. With this operation, the load on the liquefaction unit 24 is lowered and the production amount of LNG is lowered (process P2: introduction amount reduction process).

The LNG shipment schedule is set several weeks in advance, for example. Therefore, an operation to reduce the introduction amount of NG is started with the goal of the day before or half a day before shipment, and the load on the liquefaction unit 24 is kept in a reduced state when shipment of LNG is started.

The processing capacity of the liquefaction unit 24 obtained by reducing the amount of NG introduced can be used as the processing capacity of BOG conveyed from the LNG tanker 3 when LNG is shipped. From this point of view, the reduction amount of NG received from the riser 121 corresponds to an amount within ±10% of the amount equivalent to LNG obtained by re-liquefying the BOG returned from the LNG tanker 3 at the time of shipment of LNG. An example of this can be adjusted.

Additionally, during the storage period until the start of shipment, the storage pressure of the LNG stored in the reservoir 110 may be lowered to lower the vapor pressure and temperature of the LNG (process P3: reservoir pressure reduction process). For example, normally, when the pressure in the reservoir 110 is set within the range of 0.06 to 0.10 barg, the pressure is lowered to less than 0.06 barg and about 0.01 barg before starting LNG shipment.

A method of reducing the pressure of the reservoir 110 is to increase the amount of vaporization generated in the reservoir 110 and the end flash unit 25 within the range of the processing capacity of the boosting unit 26 and the liquefaction unit 24. It can be done by doing this. By lowering the pressure of the reservoir 110, the vapor pressure of the stored LNG can be lowered, and the liquid temperature of the LN can also be lowered to a temperature corresponding to the vapor pressure.

Meanwhile, when the LNG tanker 3 transporting LNG arrives, the LNG tanker 3 is docked at the FLNG 1, and the shipping facility 15 is docked at the LNG tanker 3. Then, shipment of LNG to the LNG tanker 3 is started in a state in which only the above-described process P2 is completed (if process P3 is not performed) or in a state in which processes P2 and P3 are completed (process P4: shipment) process).

Here, in the shipment of LNG to the standard LNG tanker 3, the shipment flow rate is often set within the range of 10000 to 12000 m3/h. On the other hand, in the LNG shipping method of this example, the shipping flow rate may be set to 5000 m3/h within the range of 3000 to 7500 m3/h. Since there is a proportional relationship between the shipment flow rate of LNG and the flow rate of BOG returned from the LNG tanker 3, the BOG returned to FLNG 1 can be reduced by reducing the shipment flow rate.

The longer shipping time due to lowering the shipping flow rate of LNG may be absorbed by adjusting the operation schedule of the LNG tanker 3, etc.

Also, at this time, with the implementation of the already described treatment P3, the vapor pressure of the LNG discharged toward the LNG tanker 3 decreases, so that compared to LNG without treatment P3, there is more pressure on the LNG tanker 3 side. Therefore, it is difficult for BOG to occur. In particular, the pressure of LNG in the low water on the LNG tanker 3 side is usually 0.06 to 0.10 barg, but in treatment P3, the pressure on the FLNG 1 side was lowered to less than 0.06 barg. In this case, the amount of BOG generated on the LNG tanker 3 side can be reduced by the pressure difference between the low water tank 110 on the FLNG 1 side and the low water tank 110 on the LNG tanker 3 side.

Moreover, because the temperature of LNG is lowered in the above-described treatment P3, BOG is less likely to occur on the LNG tanker 3 side compared to LNG that has not been subjected to treatment P3.

Almost the entire amount of BOG returned from the LNG tanker 3 can be processed in the liquefaction unit 24 with a reduced load by reducing the amount of NG introduced in process P1 (process P5-1: re-liquefaction process) ).

At this time, by reducing the load on the liquefaction unit 24 in advance, the amount of end flash gas generated in the end flash unit 25 is also reduced. As a result, the total amount of end flash gas and BOG is reduced, so the opportunity to burn off excess BOG in the flare stack 14 is further suppressed.

If the returned BOG is more surplus, the BOG may be sent to the reservoir 110. As shown in FIG. 3, part of the BOG transported from the LNG tanker 3 joins the LNG transported from the end flash portion 25 toward the reservoir 110. In the reservoir 110, the gas phase space increases with the shipment of LNG, so the BOG received in the reservoir 110 is stored within this gas phase space. From this point of view, it can be said that the reservoir 110 is utilized as a pressure accumulation tank for accumulating excess BOG.

As already explained, the normal set pressure of the reservoir 110 on the FLNG (1) side is 0.06 to 0.10 barg, but during the period when BOG is returned from the LNG tanker (3) to the FLNG (1), the set pressure is Make it high.

For example, in conventional design standards, the design pressure of the reservoir 110 is set to about 0.25 barg. In this case, the set pressure of the low tank 110 may be set to a value that is higher than the normal set pressure and within a range of less than 0.25 barg.

Additionally, it is also possible to design the reservoir 110 on the premise of using it as a pressure storage tank. In this case, according to the new design standard, it is possible to increase the design pressure of the reservoir 110 to, for example, 0.69 barg. In the low tank 110 designed based on such new design standards, the set pressure of the low water tank 110 may be set to a value that is higher than the normal set pressure and within a range of less than 0.69 barg.

As described above, by setting the set pressure of the reservoir 110 higher than usual, a larger amount of BOG than the volume of the gas phase space that increases with the shipment of LNG can be accepted into the reservoir 110. As a result, it is possible to accumulate BOG in the reservoir 110, as compared to the differential pressure during normal operation, and reduce the opportunity for excess BOG to be burned and disposed of in the flare stack 14. (Treatment P5-2: BOG storage process).

Once the shipment of LNG is completed, the amount of NG introduced is returned to its original state and the production volume of LNG is adjusted. Additionally, the BOG pressure accumulated in the reservoir 110 is used as fuel gas or is sent to the liquefaction unit 24 to be re-liquefied, and the pressure in the reservoir 110 is returned to the normal set pressure (process P6).

With these processes, FLNG 1 returns to normal operation and waits for the next LNG shipment timing (process P1).

The LNG shipping method according to this embodiment has the following effects. Before starting shipment of LNG to FLNG 1, the amount of NG introduced from the underwater side into the liquefaction device 2 is reduced, so the processing capacity of the liquefaction device 2 (liquefaction unit 24) increases, and the liquefaction The amount of excess BOG that cannot be completely processed by the device 2 can be suppressed.

Compared to FLNG (1) to which the LNG shipping method of this example is applied, for example, NG liquefaction devices installed on the ground generally have a large throughput. For this reason, the processing capacity of the liquefaction unit 24 is large, and the BOG returned when shipping LNG from a reservoir provided on the ground toward the LNG tanker 3 can be reused in the liquefaction unit 24 even without reducing the amount of NG introduced. In many cases, it can be liquefied.

From this viewpoint, the LNG shipping method of this example can be said to be a technology suitable for solving the problem (excess of BOG at the time of shipping LNG) unique to FLNG 1, which is a floating body facility.

Additionally, the configuration example of FLNG 1 to which the LNG shipping method of this example is applied can be changed as appropriate.

The FLNG (1) is changed to an external type (external turret) in which the turret (12) is provided outside the main body of the hull (11) illustrated in FIGS. 1 and 2, and the turret (12) is installed inside the main body of the hull (11). ) may be an internal type (internal turret) FLNG (1) provided. In addition, instead of the end flash unit 25 having an independent configuration from the reservoir 110 shown in FIG. 3, the end flash unit 25 may be integrated with the reservoir 110. Additionally, the layout of the liquefaction device 2, the utility section 202, and the living section 13 arranged on the ship body 11 can be changed as appropriate.

In addition, processes P3 (bottom pressure reduction process) and P5-2 (BOG storage process) further explained using FIG. 4 are processes for transferring energy from the LNG tanker 3 to the Floating Storage Unit (FSU) or Floating Storage and Regasification Unit (FSRU). It can also be applied to the shipment of LNG.

That is, in the implementation of process P3, LNG is transported with the pressure in the reservoir on the LNG tanker 3 side set to a pressure lower than 0.06 to 0.10 barg, docked at the FSU/FSRU, and LNG tanker 3 side. After connecting the shipping facility, LNG is shipped. In this example as well, the generation of BOG in the FSU/FSRU can be suppressed by shipping LNG with low vapor pressure and low temperature.

Additionally, when performing process P5-2, the set pressure on the FSU/FSRU side may be set to a value that is higher than the normal set pressure and within a range of less than 0.25 barg. In addition, in low water designed based on the new design standards already described, the pressure can be set higher than the normal setting pressure and within the range of less than 0.69 barg. Even in these cases, the differential pressure is as high as compared to normal operation, and by accumulating the BOG in the reservoir, the occurrence of opportunities to burn and dispose of the excess BOG in the flare stack can be reduced.

1: FLNG
110: low
121: riser
124: Choke valve
13: Residence Department
14: Flare Stack
15: Shipping equipment
2: Liquefaction device
24: Liquefaction unit
3: LNG tanker

Claims (12)

A method of shipping liquefied natural gas from a floating facility placed on the water to a transport ship,
The floating body facility is provided with a liquefaction device for liquefying natural gas received from the underwater side, and a reservoir for storing the liquefied natural gas liquefied in the liquefaction device,
an introduction amount reduction step of reducing the amount of natural gas introduced into the liquefaction device before starting shipment of the liquefied natural gas;
a shipping process of shipping liquefied natural gas from the reservoir to a transport ship;
When shipping the liquefied natural gas, it includes a re-liquefaction process of receiving boil-off gas generated on the transport ship into the liquefaction device and re-liquefying it,
BOG for returning to the reservoir a larger amount of boil-off gas than the volume of the gas phase space in the reservoir, which increases with the shipment of the liquefied natural gas, among the boil-off gas received from the transport ship when performing the shipping process. A method of shipping liquefied natural gas, comprising a storage process. The liquefied natural gas according to claim 1, wherein in the introduction amount reduction step, the introduction of natural gas is reduced within a range of ±10% of an amount equivalent to liquefied natural gas obtained by re-liquefying the boil-off gas. shipping method. The method of shipping liquefied natural gas according to claim 1, wherein in the shipping step, the shipping flow rate of the liquefied natural gas is adjusted to a value within the range of 3000 to 7500 m3/h. delete The method of shipping liquefied natural gas according to claim 1, wherein during the period during which the BOG storage process is performed, the pressure within the reservoir is increased compared to a period other than the period during which the BOG storage process is performed. The method of claim 1, further comprising a reservoir pressure reduction step of lowering the pressure within the reservoir to reduce the vapor pressure and temperature of the liquefied natural gas shipped from the reservoir before starting shipment of the liquefied natural gas. A method of shipping liquefied natural gas. It is a floating facility that is placed on the water and ships liquefied natural gas to a transport ship,
A riser that receives natural gas with an adjusted introduction amount from the underwater side,
A liquefaction device for liquefying natural gas received through the riser,
a reservoir for storing liquefied natural gas liquefied in the liquefaction device;
Shipping facilities for shipping the liquefied natural gas stored in the reservoir toward a transport ship;
a boil-off gas introduction line that receives boil-off gas generated on the transport ship side into the liquefaction device when shipping the liquefied natural gas;
Before starting shipment of the liquefied natural gas, an introduction amount reduction step of reducing the amount of natural gas introduced into the liquefaction device, a shipping step of shipping the liquefied natural gas from the reservoir toward a transport ship by the shipping facility, and When shipping liquefied natural gas, it is configured to perform a re-liquefaction process of receiving boil-off gas generated on the transport ship side through the boil-off gas introduction line into the liquefaction device and re-liquefying it,
The boil-off gas introduction line is configured to allow reception of the boil-off gas even in the low water level,
BOG for returning to the reservoir an amount of boil-off gas greater than the volume of the gas phase space in the reservoir, which increases with the shipment of the liquefied natural gas, among the boil-off gas received from the transport ship when performing the shipping process. A floating body facility characterized in that it is configured to perform a storage process. The floating body equipment according to claim 7, wherein the introduction of natural gas is reduced within a range of ±10% of the amount equivalent to liquefied natural gas obtained by re-liquefying the boil-off gas in the introduction amount reduction step. . The floating body equipment according to claim 7, wherein in the shipping process, the shipping flow rate of the liquefied natural gas is adjusted to a value within the range of 3000 to 7500 m3/h. delete The method of claim 7, comprising an end flash unit that adjusts the pressure in the reservoir,
Floating body equipment, characterized in that, during the period during which the BOG storage process is performed, the pressure in the reservoir is increased by the end flash unit compared to a period other than the period during which the BOG storage process is performed. The method of claim 7, comprising an end flash unit that adjusts the pressure in the reservoir,
Before starting shipment of the liquefied natural gas, a reservoir pressure reduction process of lowering the pressure within the reservoir is performed by the end flash unit in order to reduce the vapor pressure and temperature of the liquefied natural gas shipped from the reservoir. Floating body equipment characterized by being.

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