JPH102497A - Return gas system and return gas return feeding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the piping of a return gas pipe when LNG is received from an LNG carrier to the inside of LNG storage tanks arranged in a remote place in a receiving base where a plurality of LNG storage tanks is arranged, by interposing a return gas cooler by which BOG is cooled by treating LNG from one LNG storage tank as a cooling medium. SOLUTION: When LNG is received from a pier 2 to an LNG storage tank 10 arranged in a remote place, BOG in the LNG storage tank 10 is simultaneously fed to a return gas cooler 14. Further, LNG in the LNG storage tank 1 is fed from an LNG supply pipe 17 to the return gas cooler 14 by an LNG pump 18, and ejected from spray nozzles 21, 21 toward BOG, thereby BOG is cooled to less than the temperature of an gaseous phase in the LNG storage tank 1. Next, while cooled BOG is supplied to the LNG storage tank 1, return gas is returned from the LNG storage tank 1 to an LNG carrier 3 through a return gas pipe 7 by a return gas blower 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an LNG ship from an LNG ship.
The present invention relates to a return gas system and a return gas return method for returning return gas to the LNG ship in parallel with receiving LNG in the G storage tank.

[0002]

2. Description of the Related Art In general, at a liquefied natural gas (LNG) receiving base, when receiving LNG from an LNG ship into an LNG storage tank, the tank internal pressure of the LNG ship is kept substantially constant. LN from the LNG storage tank
Return gas is returned to Vessel G. FIG. 2 shows a conventional return gas system of this type.
Is an LNG storage tank installed at the receiving base. This LN
In the G storage tank 1, there is an LN placed beside the Yasu Bridge 2 at the receiving base.
A receiving pipe 4 for receiving LNG from the Vessel G is provided. Further, an evaporative gas (abbreviated as BOG) generated in the LNG storage tank 1 is compressed by a BOG compressor 5 and sent out. A BOG pipe 6 that joins with a vaporized gas from a vaporizer and supplies it to a boiler or the like is provided. A return gas pipe 7 is branched into the BOG pipe 6, and when receiving LNG from the LNG vessel 3 into the LNG storage tank 1, a return gas blower is provided to keep the tank internal pressure of the LNG vessel 3 substantially constant. 8 by LN
The return gas is returned from the G storage tank 1 to the LNG ship 3.

[0003]

However, in such a return gas system, the above-mentioned LNG storage system is required to install a large number of LNG storage tanks or to extend the receiving base.
When an additional LNG storage tank is to be added in addition to the storage tank 1, a return gas pipe 7 must be provided from each LNG storage tank to the bridge 2 of the LNG ship 3. However, the LNG storage tank installed in the area has a problem that the return gas pipe becomes extremely long and the capacity of the return gas blower becomes too large to be uneconomical. This has become a major constraint when planning the placement and expansion of the equipment.

The present invention has been made to effectively solve the problems of the above-mentioned conventional return gas system, and there is no need to pipe a return gas pipe from a remote LNG storage tank to a ridge bridge. It is an object of the present invention to provide a return gas system capable of greatly increasing the degree of freedom of an arrangement plan and a return gas returning method using the same.

[0005]

According to a first aspect of the present invention, there is provided a return gas system according to the present invention, comprising: a receiving base provided with a plurality of LNG storage tanks;
When receiving LNG into the storage tank,
A system for returning return gas to an NG ship, comprising: a return gas pipe for returning return gas from the one LNG storage tank to the LNG ship between the one LNG storage tank and the LNG ship. And the above one L
A BOG supply pipe for supplying the BOG in the other LNG storage tank to the one LNG storage tank is provided between the NG storage tank and another LNG storage tank that is more remote from the LNG ship than the one LNG storage tank. In addition, the BOG supply pipe is provided with a return gas cooler for cooling the BOG using the LNG from the one LNG storage tank as a cooling medium.

Here, a second aspect of the present invention is a BOG compressor in which a BOG pipe for extracting BOG generated in the LNG storage tank is provided in the other LNG storage tank, and the BOG is compressed in the BOG pipe. And the above BO
The G supply pipe is characterized by being branched to the discharge side of the BOG compressor of the BOG pipe.

[0007] Next, according to a third aspect of the present invention, there is provided a method of returning return gas according to the present invention, wherein at a receiving base provided with a plurality of LNG storage tanks, one LN near an LNG ship is provided.
A method of returning return gas to the LNG ship when receiving LNG in another LNG storage tank remote from the G storage tank, wherein the BOG in the other LNG storage tank is transferred to the one LNG storage tank.
After cooling by LNG in the NG storage tank, the one LN
The return gas is returned from the one LNG storage tank to the LNG ship while being supplied to the G storage tank.

In this case, the invention according to claim 4 is characterized in that the BOG is cooled to a temperature not higher than the gaseous phase temperature in the one LNG storage tank, and further according to claim 5. The invention is characterized in that the BOG is cooled to -150 ° C or lower.

[0009] By the way, from the one LNG storage tank, LNG
While returning the return gas to the ship and supplying the BOG in the other LNG storage tank to one LNG storage tank,
When OG is supplied to the one LNG storage tank, the gas phase temperature in the one LNG storage tank is -140C to -150C, whereas the temperature of the BOG is 30C to 40C, There is a possibility that excessive stress may be applied to the inner wall of the one LNG storage tank.

However, according to the return gas system according to the first or second aspect and the return gas returning method according to any one of the third to fifth aspects, the LN
While sending LNG to another LNG storage tank in a remote place from Vessel G, the BOG in the other LNG storage tank is transferred to the one LNG storage tank.
After being cooled by the LNG in the storage tank, it is supplied to the one LNG storage tank, and the return gas is returned from the one LNG storage tank to the LNG ship. Therefore, there is no possibility that excessive stress is applied to the one LNG storage tank. In addition, it is economical because there is no need to lay return gas pipes over a long distance from the Yasu Bridge to another remote LNG storage tank to the Yasu Bridge. As a result, when a large number of LNG storage tanks are placed on a large site, Or, especially when the location of the receiving base requires additional LNG storage tanks at a location away from the Yasu Bridge,
The degree of freedom in planning the arrangement of the LNG storage tank can be greatly expanded.

Here, according to the invention described in claim 2,
Since the BOG supply pipe for sending BOG from the other LNG storage tank to one LNG storage tank is branched to the discharge side of the BOG compressor of the BOG pipe, a separate BOG delivery blower or the like is not required, and It is economical because the length of the BOG supply pipe can be further reduced. Also, the above BOG is L
When cooling by NG spray is not sufficient, mist may be generated in the one LNG storage tank by the BOG. In this regard, claim 4
According to the invention described in (1), since the BOG is cooled to a temperature equal to or lower than the gas phase temperature in the one LNG storage tank, generation of the mist described above can be prevented. Therefore, as in the invention according to claim 5, the BOG is set to -150 in advance.
It is preferable that the mist is set to be cooled to not more than ℃ because the generation of the mist can be surely prevented.

[0012]

FIG. 1 shows an embodiment of a return gas system according to the present invention. The same components as those shown in FIG. 2 are denoted by the same reference numerals, and the description is simplified. Become In this figure, the illustration of the LNG receiving pipe 4 in the LNG storage tank (one LNG storage tank) 1 is omitted. In FIG. 1, this LNG
At the receiving base, the L
A return gas pipe 7 for returning return gas from the LNG storage tank 1 is provided between the NG storage tank 1 and the LNG ship, and the LNG storage tank 1 and the LNG
LNG storage tank (other L
NG storage tank 10 and the BO in the LNG storage tank 10
A BOG supply pipe 11 for supplying G to the LNG storage tank 1 is laid.

The LNG storage tank 10 contains LNG.
Like the storage tank 1, the BO generated in the LNG storage tank 10
A BOG tube 12 for extracting G is provided.
A BOG compressor 13 for compressing BOG is interposed in the G pipe 12. The BOG supply pipe 11 is connected to the BOG supply pipe 11.
A branch pipe is provided on the discharge side of the BOG compressor 13 of the G pipe 12. In the middle of the BOG supply pipe 11, the LN
A return gas cooler 14 for cooling the BOG sent from the G storage tank 10 is provided. A flow control valve 15 and a restriction orifice 16 are sequentially provided upstream of the return gas cooler 14.

On the other hand, the return gas cooler 14 is provided with an LNG supply pipe 17 for cooling the BOG.
The LNG supply pipe 17 is branched to a discharge-side pipe 18a of an LNG pump 18 in the LNG storage tank 1, and is further connected to the LNG supply pipe 17a.
An NG flow control valve 19 and an orifice 20 for cooling and circulating are interposed in parallel. And a plurality (2 in the figure)
Show a book. The LNG supply pipe 17 which is branched into the return gas cooler 14 and introduced into the return gas cooler 14 has L at a distal end toward the BOG flowing into the return gas cooler 14.
Spray nozzles 21 for injecting NG and cooling it are attached. Further, between the LNG storage tank 1 and the flow control valve 15 of the BOG supply pipe 11,
A control device 23 for controlling the opening and closing of the flow control valve 15 based on the pressure detected by the pressure detector 22 provided in the LNG storage tank 1 is provided. Reference numeral 24 in the figure denotes the LNG from the LNG ship 3 laid sideways on the Yasu Bridge 2.
It is a receiving pipe for receiving LNG in the NG storage tank 10.

Next, an embodiment of the return gas returning method of the present invention using the return gas system having the above configuration will be described. First, when LNG is received from the LNG ship 3 into the nearby LNG storage tank 1, the return gas blower 8 connects the return gas pipe 7 directly from the LNG storage tank 1 in parallel with the conventional manner. The return gas is returned to the LNG ship 3 through the above.
Next, when the LNG is received from the LNG ship 3 into the LNG storage tank 10 remote from the Yasu Bridge 2 via the receiving pipe 24, the BOG in the LNG storage tank 10 is sent to the return gas cooler 14 in parallel with this. send. Then, LNG in the LNG storage tank 1 is sent from the LNG supply pipe 17 to the return gas cooler 14 by the LNG pump 18, and the spray nozzle 2
The BOG is injected from 1, 21 toward the BOG, and the BOG is heated to a temperature equal to or lower than the gas phase temperature in the LNG storage tank, specifically, -150 ° C.
Cool below. Incidentally, the temperature control is performed by, for example, providing a temperature detector at the outlet side of the return gas cooler 14 of the BOG supply pipe 11 and controlling the opening and closing of the flow control valve 19 based on the temperature detected by the temperature detector. This is achieved by controlling the flow rate of the cooling LNG to the return gas cooler 14.

Next, while supplying the cooled BOG to the LNG storage tank 1, the LOG is returned from the LNG storage tank 1 by a return gas blower 8 through a return gas pipe 7.
Return the return gas to the NG ship 3. At this time, LNG
LNG storage tank 1 from storage tank 10 via return gas cooler 14
The amount of the cooled BOG sent to the LNG storage tank 1 is detected by the pressure detector 22 while controlling the opening and closing of the flow control valve 15 of the BOG supply pipe 11 by the controller 23 while detecting the pressure in the LNG storage tank 1. Is adjusted to be within a certain range.

As described above, according to the return gas system having the above structure and the method for returning the return gas using the same, the LNG storage tank 1 located at a place remote from the LNG ship 3
0 while sending LNG to the BOG in this LNG storage tank 10.
Is cooled to a temperature of −150 ° C. or lower in the return gas cooler 14 and then supplied to the LNG storage tank 1.
There is no risk of applying excessive stress to the LNG storage tank 1. Moreover, the LNG storage tank 1 is located near the LNG ship 3.
Returns the return gas from
It is economical because there is no need to lay return gas pipes over a long distance from the NG storage tank 10 to the above-mentioned ridge bridge 2. Therefore, when a large number of LNG storage tanks are arranged in a large site, especially in the location of the receiving base, Even in the case where it is necessary to add an LNG storage tank one to several kilometers away from the ridge bridge 2, the degree of freedom when planning the arrangement of the LNG storage tank can be greatly expanded.

A BOG supply pipe 11 for sending BOG from the LNG storage tank 10 to the LNG storage tank 1 is connected to the LNG storage tank 10.
Branch pipe on the discharge side of the BOG compressor 13 in the BOG pipe 12 does not require another blower or the like for sending the BOG, and the length of the BOG supply pipe 11 can be shortened. It is a target. In addition, since the BOG is cooled by the LNG injected from the spray nozzles 21 and 21 in the return gas cooler 14 to the gas phase temperature in the LNG storage tank 1 or lower, specifically to −150 ° C. or lower, When the BOG is supplied into the LNG storage tank 1, mist can be reliably prevented from being generated.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the return gas cooling system shown in FIG. 1, for example, a case of generating a return gas amount of 24000 Nm ³ / h will be described.
When the above-mentioned return gas cooling system is operated in parallel with receiving LNG, a certain amount of L at 20 t / h
The LNG in the NG storage tank 1 is sent to the return gas cooler 14 by the LNG pump 18, and the spray nozzles 21, 21
From BOG to BOG, and the BOG is -150
Cool to below ° C. At this time, in order to generate 24000 Nm ³ / h of a cooling gas of −150 ° C. or less, the returned BO
The amount of G is required to be 14000 Nm ³ / h. Actually, the amount of the return BOG is controlled by the pressure of the LNG storage tank 1. Therefore, when the internal pressure of the LNG storage tank 1 decreases, the controller 23 controls the opening and closing of the flow control valve 15 to control the return BOG.
The amount of G increases and the amount of return gas increases. Further, the restriction orifice 16 prevents BOG of 15000 Nm ³ / h or more from flowing even when the flow control valve 15 of the return BOG is fully opened. In addition, even when the return gas cooling system is not operated, the orifice 2
By keeping the LNG supply pipe 17 cooled by 0, bowing is prevented.

[0020]

As described above, according to the return gas system and the return gas return method using the same according to the present invention, the BOG in another LNG storage tank is replaced with one LNG.
After cooling by LNG in the G storage tank, the one LNG
Since the return gas is supplied to the storage tank and the return gas is returned from the one LNG storage tank to the LNG ship, there is no danger of applying excessive stress to the one LNG storage tank, and from another LNG storage tank located at a remote place from the Yasu Bridge. It is economical because there is no need to lay return gas pipes over a long distance up to the Yasu Bridge. Therefore, the LNG storage tank is required especially when it is necessary to add an LNG storage tank at a location remote from the Yasu Bridge due to the location of the receiving base. Can greatly expand the degree of freedom of the layout plan of the vehicle.

Further, according to the second aspect of the present invention, the length of the BOG supply pipe can be further shortened and the economy is excellent, and according to the fourth aspect of the present invention, the BOG supply pipe is provided. Is cooled by spraying LNG,
According to the invention as set forth in claim 5, it is possible to prevent the generation of mist in one LNG storage tank.
The effect that the generation of the mist can be reliably prevented is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a return gas system according to the present invention.

FIG. 2 is a schematic configuration diagram showing a return gas system in a conventional receiving terminal.

[Explanation of symbols]

 Reference Signs List 1 LNG storage tank (one LNG storage tank) 2 Yasuhashi 3 LNG ship 7 Return gas pipe 10 LNG storage tank (other LNG storage tank) 11 BOG supply pipe 12 BOG pipe 13 BOG compressor 14 Return gas cooler 17 LNG supply pipe 18 LNG pump 21 Spray nozzle

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasushi Kuno 3-3-3308, Shiomidai, Isogo-ku, Yokohama, Kanagawa Prefecture Construction Co., Ltd.

Claims (5)

[Claims] At a receiving base provided with a plurality of LNG storage tanks, a system for returning return gas to the LNG ship in parallel with receiving LNG from the LNG ship into the LNG storage tank. A return gas pipe for returning the return gas from the one LNG storage tank is disposed between the one LNG storage tank installed near the LNG ship and the LNG ship, and the one LNG storage tank is connected to the one LNG storage tank. , The LNG storage tank is more than the one LNG storage tank.
Between the other LNG storage tank remote from the ship,
B to supply BOG in the NG storage tank to the one LNG storage tank
An OG supply pipe is provided, and the BOG supply pipe is
A return gas system comprising a return gas cooler for cooling the BOG using LNG from the one LNG storage tank as a cooling medium. 2. A BOG pipe for extracting BOG generated in the LNG storage tank is provided in the other LNG storage tank,
A BOG compressor for compressing the BOG is interposed in the BOG pipe, and the BOG supply pipe is branched from a discharge side of the BOG pipe of the BOG pipe. 2. The return gas system according to 1. 3. A receiving base in which a plurality of LNG storage tanks are installed, when receiving LNG in another LNG storage tank remote from one LNG storage tank near the LNG ship,
A method of returning return gas to the LNG ship, wherein the BOG in the another LNG storage tank is cooled by the LNG in the one LNG storage tank, and then supplied to the one LNG storage tank while being supplied to the one LNG storage tank. And returning the return gas to the LNG ship from the ship. 4. The method according to claim 3, wherein the BOG is cooled to a temperature equal to or lower than a gas phase temperature in the one LNG storage tank. 5. The method according to claim 4, wherein the BOG is cooled to −150 ° C. or lower.