JP2000046295A - Bog re-liquefying device in low temperature liquefied gas tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To high-efficiently absorb a surplus of BOG generated in a low liquefied gas tank by low temperature liquefied gas. SOLUTION: A BOG return pipe 8 is branched and mounted on a BOG withdraw pipe to withdraw BOG from a low temperature liquefied gas tank 1. The BOG return pipe 8 is inserted in the low temperature liquefied gas tank 1 and a lower end outlet part 8a being a tip is opened to in low temperature liquefied gas 2 near a tank bottom. A net 12 is attached to the lower end outlet part 8a. When surplus BOG flows through the BOG return pipe and is injected in the low temperature liquefied gas 2 through the lower end outlet part 8a, the BOG forms small air bubbles 13 through a flow of it through the mesh of the net 12 for injection. Since the foam diameter of the injected BOG is small, a contact area with the low temperature liquefied gas 2 is increased by an amount equivalent to the decrease of the foam diameter and the BOG is high-efficiently liquefied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention blows out BOG (boil-off gas) generated in a tank for storing low-temperature liquefied gas such as LNG (liquefied natural gas) or LPG (liquefied petroleum gas) as bubbles in the low-temperature liquefied gas. The present invention relates to a BOG reliquefaction apparatus that reliquefies by absorbing and absorbing.

[0002]

2. Description of the Related Art A low-temperature liquefied gas tank 1 for storing a low-temperature liquefied gas such as LNG or LPG receives a low-temperature liquefied gas 2 into a low-temperature liquefied gas tank 1 as schematically shown in FIG. Low-temperature liquefied gas receiving pipe 3 is installed through the tank roof 1a, and a receiving lead pipe 4 having an upper end positioned in the gas layer I has a low-temperature liquefied gas receiving pipe 3 in a vertical state. 2, the lower end of the low-temperature liquefied gas receiving pipe 3 is positioned just above the funnel 5 at the upper end of the receiving lead pipe 4, and the low-temperature liquefied gas 2 is received from the low-temperature liquefied gas receiving pipe 3. It is caused to flow down through the pipe 4 and to flow out to the bottom of the low-temperature liquefied gas tank 1, and is generated by evaporating a part of the low-temperature liquefied gas 2 of the liquid layer II in the low-temperature liquefied gas tank 1 by heat of intrusion. Take BOG A BOG discharge pipe 6 for discharge is opened to the gas layer I through the tank roof 1a, and the BOG guided to the BOG discharge pipe 6 is compressed by a compressor 7 to be taken out and sent to a power plant and other demand destinations. It is like that.

The demand for the low-temperature liquefied gas stored in the low-temperature liquefied gas tank 1 having the above-described structure is different between daytime and nighttime, and during nighttime when demand is small, excess BOG is processed. Problem, surplus B
Burning and discarding OG wastes energy resources.

Therefore, as a means for preventing waste of energy resources by effectively processing surplus BOG in recent years, as shown in FIG. After branching the BOG return pipe 8 and penetrating the BOG return pipe 8 through the tank roof 1a, the BOG return pipe 8 is piped to the bottom of the low-temperature liquefied gas tank 1 and its tip is opened into the low-temperature liquefied gas 2 to remove excess BOG. BO
Attempts are made to eject BOG from the distal end through the G return pipe 8 into the low-temperature liquefied gas 2 so that BOG is absorbed by the low-temperature liquefied gas 2 and reliquefied. 9 is a pump, 10 and 11 are valves, and the other configuration is the same as that shown in FIG. 5, and the same components are denoted by the same reference numerals.

[0005]

However, the above BOG
A system in which the excess BOG is ejected as bubbles into the low-temperature liquefied gas 2 by the return pipe 8 to reliquefy it is effective because the excess BOG can be processed without waste and is effective. Since the diameter of the tip opening is large, and the tip opening is used as a nozzle to jet into the low-temperature liquefied gas 2, the bubble diameter of the BOG jetted from the tip of the BOG return pipe 8 becomes large, and therefore, it floats. There is a problem that the liquid cannot be efficiently liquefied due to the high speed, and the contact area between the liquid and the bubbles is small, so that the low-temperature liquefied gas 2 cannot be efficiently absorbed.

Accordingly, the present invention is intended to efficiently absorb BOG jetted into a low-temperature liquefied gas.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a BOG generated in a low-temperature liquefied gas tank.
A BOG return pipe is branched from the middle of the BOG extraction pipe for taking out the gas, the BOG return pipe is put into a low-temperature liquefied gas tank, the tip is opened near the bottom of the tank, and the lower end outlet which is the tip of the BOG return pipe is taken out. Then, a mesh for ejecting BOG as small-diameter bubbles was attached, and the BOG taken out of the BOG extraction pipe was ejected into the low-temperature liquefied gas as small-diameter bubbles through the net from inside the BOG return pipe. Configuration.

The surplus BOG is returned to the low-temperature liquefied gas tank through a BOG return pipe branched from the BOG extraction pipe, and is jetted out as bubbles into the low-temperature liquefied gas from the lower end outlet, which is the leading end. At this time, since a block having a net or an elongated flow path is attached to the lower end outlet of the BOG return pipe, the BOG bubbles ejected into the low-temperature liquefied gas have a small diameter. Thereby, the contact area with the low-temperature liquefied gas is increased, and the absorption into the low-temperature liquefied gas is performed efficiently.

By arranging a plurality of the above blocks side by side and displacing them slightly in the circumferential direction, the thin flow paths of each block are shifted and communicate with each other.
Advantageously, the OG bubbles can be reduced.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 (a) and 1 (b) show an embodiment of the present invention. As in the case of the low temperature liquefied gas tank 1 shown in FIG. In the configuration in which the BOG return pipe 8 is guided through the tank roof 1a to near the bottom of the low-temperature liquefied gas tank 1 and the tip is opened in the low-temperature liquefied gas 2,
A mesh 12 is attached to the lower end outlet 8a, which is the leading end of the return pipe 8, and when the BOG sent through the BOG return pipe 8 is blown out into the low-temperature liquefied gas 2 as bubbles 13,
By passing through a small eye, the diameter of the bubble 13 is reduced so as to be ejected. The material of the net 12 is arbitrary such as metal and resin.

The net 1 to the outlet 8a at the lower end of the BOG return pipe 8
2 is attached as shown in FIG. 1 (b).
In addition to the case where the net 12 formed into a circular shape in accordance with the inner surface of the BOG is fitted and attached from the tip of the BOG return pipe 8, the net 12 is connected to the BOG return pipe 8 as shown in FIG.
The fitting ring 14 is brought into contact with the front end face of
The OG return pipe 8 may be fitted to the outside from the front end side, and the periphery of the net may be sandwiched between the outer peripheral surface of the BOG return pipe 8 and the inner peripheral surface of the fitting ring 14.

When BOG is taken out from the gas layer I of the low temperature liquefied gas tank 1 in FIG. 6 to the BOG take-out pipe 6, the pump 9 is driven, the valve 10 is closed, and the valve 11 is opened to open the BOG inside the BOG take-out pipe 6. Into the low-temperature liquefied gas 2 from the lower end outlet 8a, which is the front end of the BOG return pipe 8, is blown out into the low-temperature liquefied gas 2 at this time. BOG drawn into the BOG return pipe 8 by the net 12 attached to
When the gas passes through the net 12, a large number of bubbles 13 having a small diameter are ejected. As a result, the contact area with the low-temperature liquefied gas becomes larger, and the bubbles 13 that have been made finer gradually become smaller while emitting heat to the low-temperature liquefied gas 2, thereby being absorbed by the low-temperature liquefied gas and liquefied. Will be.

FIGS. 2 (a), 2 (b) and 2 (c) show another embodiment of the present invention, in which a plurality of plates are vertically arranged inside a lower end outlet 8a which is a distal end of a BOG return pipe 8. Bubble distribution block 15 in which a large number of small flow paths 16 are formed in parallel in a grid and arranged in the horizontal and vertical directions.
Is inserted in the axial direction, and the tip of the BOG return pipe 8 is cut obliquely so that the outlet faces obliquely upward.

According to this embodiment, when the BOG sent in the BOG return pipe 8 is blown out from the tip of the BOG return pipe 8 as bubbles, it passes through the small flow paths 16 of the block 15. As a result, the diameter of the bubbles 13 is reduced, and the contact area with the low-temperature liquefied gas is correspondingly increased, so that efficient absorption into the low-temperature liquefied gas 2 is performed.

FIG. 3 shows B in the embodiment of FIG.
A number of small holes 17 penetrating inward and outward are formed in a lower end outlet 8a serving as a front end of the OG return pipe 8, and in addition to the bubble 13 being ejected from the opening of the lower end outlet 8a, the lower end outlet 8a is formed.
Small air bubbles are also ejected from the small holes 17 from the peripheral portion.

According to this embodiment, too, small-diameter bubbles are ejected from a wide range, so that B
OG absorption efficiency can be increased.

FIGS. 4 (a) and 4 (b) show still another embodiment of the present invention. In the embodiment of FIGS. 2 (a) and 2 (b), the lower end outlet portion of the BOG return pipe 8 is shown. The blocks 15 to be inserted into the inside 8a are arranged as two sets in the axial direction, and are arranged so as to be shifted from each other in the circumferential direction. As seen from the front, as shown in FIG. The road 16 is further reduced by two blocks 15 and 15a in front and rear.

According to this embodiment, the BOG divided into a large number of small flow paths 16 formed in the block 15a on the rear side (rear side from the outlet) enters the block on the front side (closer to the outlet). When entering the many small flow paths 16 formed in the BOG 15, the BOG ejected from the opening of the lower end outlet 8 a of the BOG return pipe 8 is further divided and entered. 2. The bubbles 13 are ejected as smaller bubbles 13 than in the case of each embodiment shown in FIG. 3, so that the BOG absorption efficiency to the low-temperature liquefied gas 2 can be further improved.

In the embodiment shown in FIG.
The lower end outlet portion of the OG return pipe 8 may be cut obliquely as shown in FIG. 2, and the mesh of FIG. 1, the block 15 of FIGS. 2 and 3, and the blocks 15 and 15a of FIG. The two blocks 15 and 15a are shown in FIG. 4, but two or more blocks may be used. In addition, various changes may be made without departing from the scope of the present invention. Of course.

[0021]

As described above, according to the BOG reliquefaction apparatus in the low-temperature liquefied gas tank of the present invention, the BOG return pipe is branched from the middle of the BOG extraction pipe for taking out the BOG generated in the low-temperature liquefied gas tank. A net for inserting the BOG return pipe into the low-temperature liquefied gas tank, opening the tip near the bottom of the tank, and ejecting BOG as small-diameter bubbles at the lower end outlet, which is the tip of the BOG return pipe. Attached to the BOG outlet tube
Since the OG is blown into the low-temperature liquefied gas as small-diameter bubbles through the net from the inside of the BOG return pipe, the BOG bubbles blown into the low-temperature liquefied gas become small, and the contact area with the low-temperature liquefied gas is reduced. It is possible to increase the efficiency of the absorption of the low-temperature liquefied gas, thereby effectively reliquefying the BOG. In addition, the blocks are arranged side by side in the axial direction, and the blocks are mutually phased in the circumferential direction. By displacing the BOG, the BOG flowing through the small flow paths in both blocks can be further dispersed, and can be ejected as bubbles having a smaller diameter, and the absorption efficiency of the BOG to the low-temperature liquefied gas can be improved. It is possible to achieve an excellent effect that it can be further increased.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a BOG reliquefaction apparatus in a low-temperature liquefied gas tank according to the present invention, in which (a) is a perspective view of the tip of a BOG return pipe, and (b) is a partial cut of (a). Side view,
(C) is a partially cut-away side view showing an example of attaching a net.

FIG. 2 shows another embodiment of the present invention.
FIG. 3 is a perspective view of the tip of the BOG return pipe, (b) is a partially cut-away side view of (a), and (c) is an example of a block.

FIG. 3 is a perspective view showing an example in which a fine hole is provided at the tip of the BOG return pipe shown in FIG.

FIG. 4 shows still another embodiment of the present invention.
(A) is a partially cut side view of the tip of the BOG return pipe, (b)
Is a front view.

FIG. 5 is a schematic view showing an example of a conventional low-temperature liquefied gas tank.

FIG. 6 is a schematic diagram showing a state in which a conventional BOG reliquefaction apparatus is provided in a low-temperature liquefied gas tank.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Low temperature liquefied gas tank 2 Low temperature liquefied gas 6 BOG extraction pipe 8 BOG return pipe 8a Lower end outlet 9 Pump 12 Net 13 Bubbles 15, 15a Block 16 Flow path

Claims (3)

[Claims] 1. BOG generated in a low-temperature liquefied gas tank
A BOG return pipe is branched from the middle of the BOG extraction pipe for taking out the gas, the BOG return pipe is put into a low-temperature liquefied gas tank, the tip is opened near the bottom of the tank, and the lower end outlet which is the tip of the BOG return pipe is taken out. Then, a mesh for ejecting BOG as small-diameter bubbles was attached, and the BOG taken out of the BOG extraction pipe was ejected into the low-temperature liquefied gas as small-diameter bubbles through the net from inside the BOG return pipe. A BOG re-liquefaction apparatus in a low-temperature liquefied gas tank. 2. Instead of a net, a block formed by forming a large number of elongated small channels in parallel is used, and the block is formed by BOG.
2. The apparatus for reliquefying BOG in a low-temperature liquefied gas tank according to claim 1, wherein the apparatus is provided inside a return pipe. 3. A low-temperature liquefaction apparatus according to claim 2, wherein a plurality of blocks are arranged and provided at the end of the BOG return pipe, and each block is shifted in the circumferential direction so that the flow paths of the blocks are shifted and communicate with each other. BOG reliquefaction device in gas tank.