JPH0660720B2 - Method and apparatus for cooling evaporated gas in LNG plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an LN equipped with an LNG tank for storing LNG.
The present invention relates to a method and apparatus for cooling evaporative gas in a G plant.

[Prior Art] Generally, in an LNG plant (reception terminal) equipped with an LNG tank, a gas (BOG gas) that naturally evaporates in the tank.
The piping is made so that it can be taken out and cooled.

As shown in FIG. 2, in the conventional LNG plant of this type, an LNG discharge line 3 extending in one direction from each of a plurality of LNG tanks 1 containing LNG via a pressure pump 2 is provided. The water is vaporized by the seawater vaporizer 4 provided on the downstream side in the delivery direction A and is delivered to the demand side such as a thermal power plant.

On the other hand, each L is arranged so as to be parallel to the LNG discharge line 3.
BOG for connecting the top of NG tank 1 and collecting BOG gas
A line 5 is provided, and is compressed to a predetermined pressure by a BOG compressor 6 arranged at the end side thereof, and is brought to the same level as the vaporized LNG, and then joined to the extension of the LNG discharge line 3. .

A suction drum 8 having a spray pipe 7 for injecting LNG is provided on the upstream side in the delivery direction A of the BOG compressor 6, and the BOG gas is passed through the suction drum 8 to cool it.
The compression efficiency of the OG compressor 6 is improved.

A cooling LNG pipe 9 branched from the LNG discharge line 3 is connected to the spray pipe 7, and a part of the discharged LNG is introduced into the spray pipe 7. In addition, the LNG used for cooling is located below the suction drum 8.
A drain pump 10 and a drain pipe 11 for returning the oil to the LNG tank 1 are provided.

The suction drum 8 receives the LNG remaining in the receiving line (not shown) at the time of receiving the LNG tank 1
A pipe (not shown) for returning to the above is also provided.

Further, although omitted in FIG. 2, each LNG tank 1 is provided with a spray ring having an injection nozzle so that the LNG to be received can be injected from above.

[Problems to be Solved by the Invention] Although the temperature of the BOG gas is about the same as LNG (about -160 ° C) immediately after evaporation, the BOG collecting pipe 5
The temperature gradually rises as it passes through the inside, and becomes about -110 ° C on the terminal side.

For this reason, this BOG gas must be cooled significantly in order to increase the compression efficiency, the suction drum 8 must be made large, and two or more suction drums 8 are required depending on the plant scale. Therefore, in the LNG plant, BOG
There is a problem that a large space is required to cool the gas.

Therefore, in view of the above circumstances, the present invention was devised to provide a method for cooling an evaporative gas and an apparatus therefor, which can eliminate the need for a large suction drum in an LNG plant.

[Means for Solving the Problems] The first aspect of the present invention is to provide a plurality of Ls provided in an LNG plant.
Of the NG tanks, LNG spray is formed in a specific LNG tank, and the evaporative gas generated in each LNG tank is collected in a specific tank, passed through the spray and cooled, and then the evaporative gas is compressed. It is then sent out.

A second aspect of the present invention is an apparatus for carrying out the above method, which collects evaporative gas in each LNG tank and forms a collective pipe whose terminal side is communicated with the space of a specific LNG tank, A spray means for injecting LNG is provided in the space portion, and a transfer line extending from the space portion to the compressor for the evaporative gas is provided in the specific LNG tank.

[Operation] The vaporized gas collected by the above method is
It is cooled in the G tank to improve the compression efficiency.

Further, with the above configuration, the collecting pipe guides the vaporized gas collected from each LNG tank to the space portion of the specific LNG tank. The spray means forms a spray of LNG in the space and cools the vaporized gas passing through the spray. The transfer line guides the cooled vaporized gas to the compressor and compresses it to a desired pressure.

EXAMPLES Examples of the present invention will be described below with reference to the accompanying drawings.

First, referring to FIG. 1, an embodiment of a cooling device for an evaporative gas in an LNG plant according to the present invention will be described. In the figure, the same components as those of the related art are designated by the same reference numerals and the description thereof will be omitted.

This device collects the BOG gas, which is the evaporative gas, in each LNG tank 1, and the end side of the device collects a specific LNG tank 2
A collective pipe 23 communicating with one space 22 is formed, and a spray means 24 for injecting LNG into the space 22 is also provided in the specific LNG tank 21.
A transfer line 25 extending from 2 to the BOG compressor 6, which is a compressor for evaporative gas, is provided.

In the present embodiment, the specific LNG tanks 21 are formed as two groups located on the most downstream side in the delivery direction A among the large number of LNG tanks 1 of which only a part is illustrated.

The collecting pipe 23 is composed of a branch pipe 26 that is erected from the top of each LNG tank 1 and a main pipe 27 that connects them, and the main pipe 27 extends to the downstream side in the delivery direction A,
Each of them is connected to the upper part of the specific LNG tank 21.

The spray means 24 is a pipe 28 for injection which is branched from the LNG discharge line 3 and extended to the specific LNG tank 21.
And the specific LNG tank 21 connected to the injection pipe 28.
And a spray ring 29 provided on the upper side of the spray ring 29, and spray nozzles (not shown) opened to face the space 22 are attached to the spray ring 29 at appropriate intervals.

In the present embodiment, the spray ring 29 is also formed as a spray ring for injecting the LNG to be received from above. Further, the injection pipe 28 is provided with a flow rate control valve 30 for appropriately adjusting the flow rate.

The transfer line 25 is raised from a position opposite to the connecting position of the collecting pipe 23 in the radial direction of the tank, and allows the BOG gas collected by the collecting pipe 23 to pass through the space 22 and then BOG compression. It is designed to lead to machine 6. In the present embodiment, the transfer lines 25 respectively coming out from the two specific LNG tanks 21 are formed so as to join before the BOG compressor 6.

Next, one embodiment of the method for cooling the evaporative gas in the LNG plant according to the present invention will be described as the operation of the above configuration.

LNG in the LNG tank 1 including the specific LNG tank 21
Is guided to the downstream side in the delivery direction A by the LNG discharge line 3, gasified by the seawater vaporizer 4, and then delivered to the demand side such as a thermal power plant.

The BOG gas generated in each LNG tank 1 is collected by the collecting pipe 23, and the specific LN which is the end side thereof is collected.
It is introduced into the space 22 of the G tank 21.

On the other hand, in the space portion 22 of the two specific LNG tanks 21,
The spray of the spray ring 29 forms LNG spray, and the introduced BOG gas is cooled by passing through it.

The temperature of this LNG spray is about -160 ° C, and even if the BOG gas flowing through the collecting pipe 23 is heated to about -110 ° C, for example, it is reduced to about -150 ° C.

The cooled BOG gas and the BOG gas immediately after evaporation of the specific LNG tank 21 itself are efficiently compressed by the BOG compressor 6 via the transfer line 25, and the LNG discharge line 3
Of the gasified LNG and is sent out.

In this way, the spray means 2 is attached to the specific LNG tank 21.
4 and the transfer line 25 are provided, and BO from the collecting pipe 23
G gas is supplied to the LNG in the space 22 of the specific LNG tank 21.
Since it was passed through the spray, cooled, and then guided to the BOG compressor 6, a large suction drum conventionally provided for cooling, and an LNG pipe for cooling accompanying it,
Drain pump and drain pipe are not required. That is, LN
Space saving of G plant is achieved.

Further, since the spraying means 24 can utilize the spraying which is conventionally provided, and the collecting pipe 23 is not much different from the conventional BOG line, it is extremely practical.

Although omitted in FIG. 1, in the present invention, since the suction drum is abolished, a drum and a pump for returning the LNG remaining in the receiving line to the LNG tank 1 are separately required. This drum can be much smaller than conventional suction drums, with a volume of about one-fifth or less, and less impact on space saving.

Furthermore, although two specific LNG tanks are provided in this embodiment, one or more specific LNG tanks may be provided depending on the scale of the LNG plant.

[Effects of the Invention] In summary, according to the present invention, the following excellent effects are exhibited.

(1) According to the method of the present invention, in a specific LNG tank,
The evaporative gas immediately before being compressed can be cooled, the conventional cooling equipment is not required, and it can contribute to the space saving of the LNG plant.

(2) Further, according to the device of the present invention, the evaporative gas can be surely cooled with a simple structure, which is extremely versatile.

[Brief description of drawings]

FIG. 1 shows an embodiment of an evaporative gas cooling device in an LNG plant according to the present invention and a configuration diagram for explaining a method for evaporative gas cooling in an LNG plant, and FIG. 2 shows a conventional LNG plant. It is a block diagram. In the figure, 1 is an LNG tank, 6 is a BOG compressor as a compressor,
Reference numeral 21 is a specific LNG tank, 22 is a space portion thereof, 23 is a collecting pipe, 24 is a spray means, and 25 is a transfer line.

Claims (2)

[Claims] 1. A plurality of LNGs provided in an LNG plant
After LNG is sprayed in a specific LNG tank among the tanks, and the evaporative gas generated in each LNG tank is collected in the specific tank and passed through the spray to be cooled,
LN characterized by compressing and delivering this vaporized gas
Method for cooling evaporative gas in G plant. 2. A collecting pipe, which collects the vaporized gas in each LNG tank and has its end side communicated with a space of a specific LNG tank, and a spray means for injecting LNG in the space, A cooling device for an evaporative gas in an LNG plant, characterized in that a transfer line extending from the space to a compressor for the evaporative gas is provided in the specific LNG tank.