JP3467953B2 - Boil-off gas entrainment prevention device for low temperature liquefied gas tank - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boil-off gas (BOG) entrainment prevention device used in a low temperature liquefied gas tank in which a low temperature liquefied gas is received in a liquid layer from above through a tank roof.

[0002]

Liquefied natural gas LNG and liquefied petroleum gas LP
The low temperature liquefied gas tank for receiving the low temperature liquid such as G and storing it for a required period is a low temperature liquefied gas receiving tank for receiving the low temperature liquefied gas 2 into the low temperature liquefied gas tank 1 as shown in FIG. 5 and FIG. Pipe 3 to tank roof 1
The low temperature liquefied gas tank 1 has
The receiving lead tube 4 which is installed so as to be positioned in the inner gas layer I and has a diameter slightly larger than that of the low temperature liquefied gas receiving tube 3 is provided at a position immediately below the low temperature liquefied gas receiving tube 3 and has its lower end. Is placed vertically so as to be submerged in the liquid layer II, and the funnel portion 5 is provided at the upper end of the receiving lead tube, and the low temperature sent to the low temperature liquefied gas tank 1 through the low temperature liquefied gas receiving tube 3 is provided. The liquefied gas 2 is made to flow down from the outlet of the gas receiving pipe 3 toward the funnel portion 5 of the receiving lead pipe 4 so as to flow out to the tank bottom through the receiving lead pipe 4.
Further, a boil-off gas (hereinafter referred to as BOG) generated by vaporizing a part of the low temperature liquefied gas 2 stored in the liquid layer II.
A BOG take-out pipe 6 for taking out water is connected to the top of the tank roof 1a, and a BOG compressor 7 is provided at an intermediate position of the BOG take-out pipe 6.

[0003]

However, in the above-mentioned low temperature liquefied gas tank, the low temperature liquefied gas 2 flowing down from the low temperature liquefied gas receiving pipe 3 is simply provided with the funnel portion 5 at the upper end of the receiving lead pipe 4 in the conventional case. Since the low temperature liquefied gas 2 is violently flown from the outlet of the low temperature liquefied gas receiving pipe 3 toward the funnel portion 5 of the receiving lead pipe 4, as shown in an enlarged view in FIG. A lot of turbulence is generated on the outside of the low temperature liquefied gas 2 flowing down to the surrounding air to enclose the surrounding gas, and due to this, when the low temperature liquefied gas is transferred from the low temperature liquefied gas receiving pipe 3 to the receiving lead pipe 4, it becomes When a certain amount of BOG is involved, and further, a lot of turbulence is generated outside the low temperature liquefied gas 2, the low temperature liquid flowing down to the liquid surface of the low temperature liquefied gas 2 in the receiving lead tube 4 It becomes choppy state occurs severe disturbance in liquid level when gas 2 has reached, sometimes BOG Here are caught in the liquid in the receiving lead pipe 4. The entrained BOG condenses when it enters the liquid layer II, so the gas layer I
The amount of BOG diffused therein decreases, and the gas pressure in the gas phase I of the low temperature liquefied gas tank 1 decreases. When the pressure of the BOG in the low temperature liquefied gas tank 1 is lowered, it is not compressed by the BOG compressor 7 provided at an intermediate position of the BOG extraction pipe 6 connected to the top part of the tank roof 1a, and conversely the BOG compression is performed. BO from machine 7 into the tank
There is also a problem that G may enter, and when the low-temperature liquefied gas tank 1 becomes large, the low-temperature liquefied gas tank 1 may be buckled due to external pressure due to a decrease in BOG pressure.

In view of the above, the present invention provides a boil-off gas winding of a low temperature liquefied gas tank which can prevent BOG from being entrained when the low temperature liquefied gas is transferred from the low temperature liquefied gas receiving pipe to the receiving lead pipe and received in the low temperature liquefied gas tank. The present invention aims to provide an anti-locking device.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a low temperature liquefied gas receiving pipe through a tank roof to a gas layer in a tank, and a lower end of the liquid in the tank. The low temperature of the low temperature liquefied gas tank in which the inlet of the receiving reed tube installed so as to be submerged in the layer is faced to the outlet of the low temperature liquefied gas receiving tube to receive the low temperature liquefied gas into the tank through the receiving reed tube A receiving lead tube in which the inner diameter of the inlet is smaller than the inner diameter of the outlet of the low temperature liquefied gas receiving pipe by providing a narrowed part at the upper end immediately below the liquefied gas receiving pipe or by using a narrow diameter And at the upper end of the receiving lead tube,
A liquid storage container for storing the low-temperature liquefied gas that has not flowed directly into the receiving lead pipe out of the low-temperature liquefied gas receiving pipe, and the upper side surface of the liquid storage container is the inlet of the receiving lead pipe. It is configured to be fixed so that it is higher than the above.

When the low-temperature liquefied gas starts to flow from the low-temperature liquefied gas receiving pipe toward the receiving lead pipe, only the undisturbed inner flow flows into the receiving lead pipe. The outside flow becomes a curtain shape to keep the inlet of the receiving reed tube isolated from the gas layer in the low temperature liquefied gas tank, and the liquid level of the low temperature liquefied gas stored in the liquid storage container is When it rises and becomes higher than the inlet of the receiving lead tube, the low temperature liquefied gas in the liquid storage container overflows and gradually flows into the receiving lead tube from the vicinity of the inlet and the inlet of the receiving lead tube becomes Since it can be kept in a state of being separated from the gas layer in the low temperature liquefied gas tank, the low temperature liquefied gas which is about to flow into the receiving lead tube and the B in the gas layer
The contact with the OG can be cut off, and the entrainment of the surrounding BOG due to the flow of the low temperature liquefied gas from the low temperature liquefied gas receiving pipe to the receiving lead pipe can be suppressed.

In the above, a liquid level gauge for detecting the liquid level of the low temperature liquefied gas accumulated in the liquid storage container is installed in the liquid storage container, and a control valve is arranged at an intermediate position of the low temperature liquefied gas receiving pipe. When the opening / closing degree of the control valve is operated according to the detection level from the liquid level gauge to adjust the flow rate of the low temperature liquefied gas, the liquid level of the low temperature liquefied gas stored in the liquid storage container can be adjusted to a required width. Can be kept between.

Further, the low temperature liquefied gas receiving pipe is penetrated through the tank roof to the gas layer in the tank, and the lower end of the receiving reed pipe is installed so as to be immersed in the liquid layer in the tank. At the side of the lower end of the low temperature liquefied gas receiving pipe in the low temperature liquefied gas tank in which the low temperature liquefied gas is received inside the tank through the receiving reed pipe. Install the receiving lead tube eccentrically so that the upper end of the tube is located,
And, at the upper end of the receiving lead tube, a liquid storage container for accumulating the low temperature liquefied gas flowing down from the low temperature liquefied gas receiving tube and causing it to overflow and flow into the receiving lead tube is attached, The lower end of the low-temperature liquefied gas receiving pipe is located in the reservoir, and the low-temperature liquefied gas that has flowed down from the outlet of the low-temperature liquefied gas receiving pipe is stored in the reservoir and overflowed to receive lead. It can also be accommodated through a tube into a cryogenic liquefied gas tank.

In this case, the low temperature liquefied gas which has overflowed from the liquid reservoir and has flowed into the receiving lead tube is
Since the flow is gently lowered along the inner surface of the receiving lead tube, it is possible to prevent the flow of intense turbulence from entraining a large amount of the surrounding BOG.

Further, in the above, the side surface of the liquid storage container is located at a position between the lower end of the low temperature liquefied gas receiving pipe and the upper end of the receiving lead pipe inside the liquid storage container and higher than the inlet of the receiving lead pipe. A weir whose height is lower than the upper part,
The low-temperature liquefied gas may be installed in a single layer or multiple layers so as to surround the receiving lead tube so that the low-temperature liquefied gas overflows in multiple stages. As a result, the flow of the low-temperature liquefied gas stored in the liquid storage container overflows. Since the temperature of the liquefied gas is gradually decreased, the surrounding BOG can be further suppressed from being entrained by the low-temperature liquefied gas receiving pipe from the low-temperature liquefied gas receiving pipe to the receiving lead pipe.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1A and 1B show an embodiment of a boil-off gas entrainment prevention device for a low temperature liquefied gas tank of the present invention, which is fed into a low temperature liquefied gas tank 1 through a low temperature liquefied gas receiving pipe 3. The low temperature liquefied gas 2 that has been received, the receiving lead pipe 4 arranged immediately below the low temperature liquefied gas receiving pipe 3
In the structure in which the cold lead gas flows toward the bottom of the low temperature liquefied gas tank 1 through the receiving lead pipe 4, the upper end of the receiving lead pipe 4 has an inner diameter d of the inlet at the upper end thereof. Inner diameter D of the lower end outlet of 3
A tapered reservoir 8 having a smaller diameter is provided, and a basin-shaped liquid reservoir 9 is provided such that the upper portion of the side surface of the reservoir 9 is higher than the inlet of the throttle 8 of the receiving lead tube 4. In this way, the diaphragm 8 is fixed on the lower boundary line.

Further, a liquid level gauge 10 for detecting the liquid level of the low temperature liquefied gas 2 stored in the liquid storage container 9 is provided inside the liquid storage container 9, and the low temperature liquefied gas receiving pipe is also provided. A control valve 11 is arranged at an intermediate position of 3, and the liquid level gauge 1
The degree of opening and closing of the control valve 11 is operated based on the detection signal from 0 to control the flow rate of the low temperature liquefied gas 2 flowing from the low temperature liquefied gas receiving pipe 3 toward the receiving lead pipe 4. The configuration. Reference numeral 12 is a controller for giving a command to the control valve 11 based on a signal from the liquid level gauge 10.

When the low-temperature liquefied gas 2 is started to be received in the low-temperature liquefied gas tank 1, the low-temperature liquefied gas 2 is sent through the low-temperature liquefied gas receiving pipe 3 and begins to flow down from the outlet, the upper end of the receiving lead pipe 4 is tapered. Since the narrowed portion 8 having a shape is provided, the flow 2a of the low temperature liquefied gas 2 flowing down the central portion of the low temperature liquefied gas receiving pipe 3 is received through the inlet of the receiving lead pipe 4 as shown in FIG. While flowing directly into the lead pipe 4, the outside flow 2b along the pipe wall of the low temperature liquefied gas receiving pipe 3 flows down along the outside of the receiving lead pipe 4 and is stored in the liquid reservoir 9. . As a result, only the undisturbed inner flow 2a flows into the receiving lead tube 4, and the outer flow becomes a curtain shape so that the low-temperature liquefied gas receiving tube 3 and the narrowed portion 8 of the receiving lead tube 4 are formed. Since the space is enclosed, the gas layer I in the low-temperature liquefied gas tank 1 and the inlet of the receiving reed tube 4 can be separated by the curtain of the low-temperature liquefied gas, and the surrounding BOG and the receiving lead can be made. The contact with the flow 2a entering the tube 4 can be cut off and the entrainment of BOG can be prevented.

After that, the low temperature liquefied gas 2 is accumulated in the liquid reservoir 9 by the outer flow 2b, and the low temperature liquefied gas 2 is introduced from the inlet of the narrowed portion 8 of the receiving lead tube 4 as shown in FIG. When the liquid level of the low temperature liquefied gas becomes high, all the low temperature liquefied gas 2 that has flowed down from the low temperature liquefied gas receiving pipe 3 is received.
The liquid is not directly flowed into the liquid storage container 9, but is received by the liquid storage container 9 and is once stored in the liquid storage container 9, and the low temperature liquefied gas 2 in the liquid storage container 9 is in an overflow state, and the low temperature liquefied gas of the receiving lead pipe 4 From the vicinity of the inlet, it will flow into the receiving lead tube 4 in sequence. At this time, a layer of the low temperature liquefied gas 2 is formed between the inlet of the receiving lead tube 4 and the gas layer I of the low temperature liquefied gas tank 1. Since it is formed, the inlet of the receiving lead tube 4 can be kept isolated from the gas layer I.

Therefore, in the present invention, the gas layer I of the low temperature liquefied gas tank 1 and the inlet of the receiving reed tube 4 are completely isolated immediately after the start of receiving the low temperature liquefied gas 2 and after the required time has elapsed. Since it can be kept in a stable state, the contact between the low temperature liquefied gas 2 which is about to flow into the receiving lead tube 4 and the BOG in the gas phase I can be cut off, and the low temperature liquefied gas receiving tube 3 receives Surrounding BOG accompanying the flow of low temperature liquefied gas 2 toward the lead tube 4.
Can be suppressed.

In the above, the controller 12 operates the control valve 11 of the low-temperature liquefied gas receiving pipe 3 to adjust the flow rate of the low-temperature liquefied gas 2 based on the detection signal of the liquid level gauge 10 provided in the liquid reservoir 9. Since this is done, the liquid storage container 9
It is possible to keep the liquid level within a required width, the flow rate of the low temperature liquefied gas 2 is too high, and the low temperature liquefied gas 2 overflows from the liquid storage container 9, or the flow rate of the low temperature liquefied gas 2 is low. It is also possible to prevent the layer of the low temperature liquefied gas 2 from disappearing from above the inlet of the receiving lead tube 4 after passing.

Next, FIG. 2 shows another embodiment of the present invention, in which a tapered narrowed portion 8 is provided at the upper end of the receiving lead tube 4 shown in FIGS. In place of the system in which the inlet of the lead tube 4 has a smaller diameter than the outlet of the low temperature liquefied gas receiving tube 3, a small diameter receiving lead tube having an inner diameter d smaller than the inner diameter D of the outlet of the low temperature liquefied gas receiving tube 3 Four
And a liquid reservoir 9 at the upper end of the receiving lead tube 4.
Is fixed such that the upper part of the side surface of the liquid reservoir 9 is higher than the inlet of the receiving lead tube 4. In the figure,
The same components as those in FIGS. 1A and 1B are designated by the same reference numerals.

In the case of the embodiment shown in FIG. 2, when the low-temperature liquefied gas 2 starts to be received and the low-temperature liquefied gas 2 starts to flow down from the outlet of the low-temperature liquefied gas receiving pipe 3, the center of the low-temperature liquefied gas receiving pipe 3 Since the partial flow 2a directly flows down into the receiving lead pipe 4, the outside flow 2b serves as a curtain and is enclosed between the low temperature liquefied gas receiving pipe 3 and the upper end of the receiving lead pipe 4, The gas layer I in the low temperature liquefied gas tank 1 and the inlet of the receiving reed tube 4 can be made to be in an isolated state, and the low temperature stored in the liquid storage container 9 as shown by the two-dot chain line in the figure. When the liquid level of the liquefied gas 2 becomes higher than the upper end of the receiving lead tube 4, the low-temperature liquefied gas 2 in an overflow state is sequentially flown into the receiving lead tube 4, and the low-temperature liquefied gas is provided above the receiving lead tube 4. 2 layers are formed and received Since the inlet of the cold tube 4 can be kept isolated from the gas phase I, the surrounding BOG is entrained as the low temperature liquefied gas 2 flows from the low temperature liquefied gas receiving tube 3 toward the receiving lead tube 4. Can be prevented
Further, since the receiving lead tube 4 having a small diameter is used, the receiving lead tube 4 can be easily manufactured and supported and fixed.

Next, FIG. 3 shows another embodiment of the present invention. A low temperature liquefied gas is placed below the low temperature liquefied gas receiving pipe 3 at a position eccentric from the center line of the low temperature liquefied gas receiving pipe 3. The receiving lead tube 4 having a diameter slightly larger than that of the receiving tube 3,
The receiving lead tube 4 and the low temperature liquefied gas receiving tube 3 are installed so that the upper end portion of the receiving lead tube 4 and the lower end portion of the receiving lead tube 4 overlap each other by a required length, and a liquid reservoir 9 is provided at the upper end portion of the receiving lead tube 4. The container 9 is fixed so that the upper portion of the side surface of the container 9 is higher than the inlet of the receiving lead tube 4 and the lower end of the low temperature liquefied gas receiving tube 3 is housed inside.

In the case of the embodiment shown in FIG. 3, the low temperature liquefied gas tank 1 starts to receive the low temperature liquefied gas 2 and is sent through the low temperature liquefied gas receiving pipe 3 to be stored in the liquid reservoir 9 at a low temperature. When the liquid level of the liquefied gas 2 becomes higher than the inlet of the receiving lead tube 4, the low temperature liquefied gas 2 in an overflow state is flown into the receiving lead tube 4 and is gradually lowered along the inner surface of the receiving lead tube 4. Therefore, it is possible to prevent the flow of the low temperature liquefied gas 2 from being significantly disturbed and entraining a large amount of the surrounding BOG.

Further, FIG. 4 shows an application example of the embodiment shown in FIG. 3. In the same configuration as that shown in FIG. 3, the lower end portion of the low temperature liquefied gas receiving pipe 3 inside the liquid reservoir 9 is A weir 13 having a height higher than the inlet of the receiving lead tube 4 and lower than the upper side surface of the liquid storage container 9 is provided between the upper end portion of the receiving lead tube 4 and the upper end portion of the receiving lead tube 4. Around the circumference of, the double arrangement is made such that the height gradually increases from the one arranged inside to the one arranged outside.

In this case, since the weir 13 is doubly provided between the low temperature liquefied gas receiving pipe 3 and the receiving lead pipe 4, the low temperature liquefied gas 2 sent through the low temperature liquefied gas receiving pipe 3 has three stages. Since the cold liquefied gas 2 is made to flow more slowly each time the overflow is repeated, the cold liquefied gas 2 flows from the low temperature liquefied gas receiving pipe 3 to the receiving lead pipe 4. It is possible to further suppress the entrainment of the surrounding BOG due to the low-temperature liquefied gas 2 flowing toward the air.

The present invention is not limited to the above-described embodiment. For example, in the embodiment shown in FIG. 1, the tapered lead portion 8 is provided at the upper end portion of the receiving lead tube 4. This is the low temperature liquefied gas receiving pipe 3
It is also possible to provide a straight-cylindrical narrowed portion 8 having an inner diameter smaller than that, in short, the inner diameter of the inlet of the receiving lead tube 4 is smaller than the inner diameter of the outlet of the low temperature liquefied gas receiving tube 3. Any shape of the narrowed portion 8 may be used, and the embodiment shown in FIG. 4 shows a case in which the weir 13 is double provided around the receiving lead tube 4. The number of weirs 13 may be increased or decreased in accordance with the horizontal distance between the low temperature liquefied gas receiving pipe 3 and the receiving lead pipe 4, and the present invention may be modified in various ways without departing from the scope of the invention. Of course.

[0025]

As described above, according to the boil-off gas entrainment prevention device for low-temperature liquefied gas of the present invention, it is sent to the low-temperature liquefied gas tank through the low-temperature liquefied gas receiving pipe and is discharged from the outlet of the low-temperature liquefied gas receiving pipe. The inside diameter of the inlet of the receiving lead tube is low by squeezing the low temperature liquefied gas that flows down to the bottom of the tank by providing a narrowing part at the upper end of the receiving lead tube or by using a small diameter receiving lead tube. While making it smaller than the inner diameter of the outlet of the receiving pipe,
A liquid storage container is fixed to the upper end portion of the receiving lead tube so that the vapor layer in the low temperature liquefied gas tank and the inlet of the receiving lead tube can be isolated by using the low temperature liquefied gas when receiving the low temperature liquefied gas. Since it is made possible, it is possible to suppress the entrainment of the surrounding BOG due to the flow of the low temperature liquefied gas from the low temperature liquefied gas receiving pipe to the receiving lead pipe, and further, to provide a liquid level meter provided in the liquid reservoir. When the control valve placed in the middle of the low-temperature liquefied gas receiving pipe is operated by the detection signal of the low-temperature liquefied gas to adjust the flow rate of the low-temperature liquefied gas, the liquid level of the low-temperature liquefied gas stored in the liquid reservoir can be adjusted to the required width. Can be kept in between.

Further, the receiving lead pipe is installed at an eccentric position below the low temperature liquefied gas receiving pipe, and the liquid reservoir is fixed to the upper end portion of the receiving lead pipe, so that the low temperature liquid flowing down from the outlet of the low temperature liquefied gas receiving pipe is supplied. If the liquefied gas is once stored in the liquid container and then overflowed to flow into the receiving lead tube, the low-temperature liquefied gas is gently dropped along the inner surface of the receiving lead tube, resulting in a violent flow. It is possible to prevent the occurrence of turbulence and to entrain a large amount of surrounding BOG. Furthermore, between the lower end of the low temperature liquefied gas receiving pipe and the upper end of the receiving reed pipe inside the liquid storage container. If weirs are installed in a single position or in multiple positions, the flow of the low temperature liquefied gas stored in the liquid storage container becomes gentle due to repeated overflows. Entrainment from the gas receiving conduit of BOG surrounding accompanying stream of low-temperature liquefied gas towards the receiving lead pipe can be further suppressed to.

As a result, the decrease in the amount of BOG diffused in the gas phase in the low temperature liquefied gas tank can be suppressed and the decrease in the BOG pressure in the low temperature liquefied gas tank can be prevented.
It is possible to prevent suction failure of the BOG compressor, backflow from the BOG compressor, and the like, and it is possible to eliminate the possibility of buckling of the low temperature liquefied gas tank due to external pressure.
Exerts an excellent effect.

[Brief description of drawings]

1 shows an embodiment of a boil-off gas entrainment prevention device for a low-temperature liquefied gas tank of the present invention, (a) is a sectional side view showing a state immediately after starting the reception of low-temperature liquefied gas, and (b) is a It is a cutting side view showing a state after a required time has elapsed.

FIG. 2 is a cut side view showing another embodiment of the present invention.

FIG. 3 is a cut side view showing another embodiment of the present invention.

FIG. 4 is a cut side view showing an application example of the present invention.

FIG. 5 is an overall view showing an example of a low temperature liquefied gas tank.

6 is a view showing a relationship between a low temperature liquefied gas receiving pipe and a receiving lead pipe, and is an enlarged view of a portion A of FIG.

[Explanation of symbols]

1 Low temperature liquefied gas tank 1a Tank roof 2 Low temperature liquefied gas 3 Low-temperature liquefied gas receiving pipe 4 Acceptance lead tube 8 throttle 9 Liquid storage container 10 level gauge 11 Control valve 13 weir

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masasuke Nakajima 1 Shin-Nakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa Ishikawajima Harima Heavy Industries, Ltd. Technical Research Institute (72) Inventor Mikio Morioka 3-2 Toyosu, Koto-ku, Tokyo No. 16 Ishikawajima Harima Heavy Industries Co., Ltd.Toyosu General Office (72) Inventor Shinya Suguri No. 1 Shin-Nakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa Ishikawajima-Harima Heavy Industries Co., Ltd. Technical Research Institute (56) Reference JP 1 -126500 (JP, A) Actual development Sho-23-23399 (JP, U) Actual development 4-117295 (JP, U) Actual development 4-116097 (JP, U) (58) Fields investigated (Int.Cl) . ^7, DB name) F17C 13/00 302

Claims (6)

(57) [Claims] 1. An inlet of a receiving lead pipe, wherein a low-temperature liquefied gas receiving pipe is penetrated through a tank roof to a gas layer in the tank, and a lower end is installed so as to be submerged in a liquid layer in the tank. To the outlet of the low temperature liquefied gas receiving pipe to receive the low temperature liquefied gas inside the tank through the receiving lead pipe, at a position directly below the low temperature liquefied gas receiving pipe in the low temperature liquefied gas receiving pipe. The receiving lead pipe having the inner diameter of the inlet smaller than the inner diameter of the outlet is installed, and the low temperature liquefied gas received from the low temperature liquefied gas receiving pipe is received at the upper end of the receiving lead pipe. A liquid storage container for storing what has not directly flown into the lead tube, the side surface of the liquid storage container being fixed to be higher than the inlet of the receiving lead tube. Boil-off gas entrapment prevention device for low temperature liquefied gas tanks. 2. The boil-off of a low temperature liquefied gas tank according to claim 1, wherein a narrowed portion is provided at an upper end of the receiving lead tube so that an inner diameter of an inlet of the receiving lead tube becomes smaller than an inner diameter of an outlet of the low temperature liquefied gas receiving tube. Gas entrapment prevention device. 3. A boil-off gas for a low temperature liquefied gas tank according to claim 1, wherein the inner diameter of the inlet of the receiving lead tube is smaller than the inner diameter of the outlet of the low temperature liquefied gas receiving tube by using a small diameter receiving lead tube. Entrainment prevention device. 4. A liquid level gauge for detecting the liquid level of the low temperature liquefied gas accumulated in the liquid sump container is installed in the liquid sump container, and a control valve is arranged at an intermediate position of the low temperature liquefied gas receiving pipe.
The boil-off gas entrainment of a low temperature liquefied gas tank according to claim 1, 2 or 3, wherein the flow rate of the low temperature liquefied gas is adjusted by operating the opening / closing degree of the control valve according to the detection level from the liquid level gauge. Prevention device. 5. An inlet of a receiving lead pipe, wherein a low temperature liquefied gas receiving pipe is penetrated through a tank roof to a gas layer in the tank, and a lower end is installed so as to be submerged in a liquid layer in the tank. At the side of the lower end of the low temperature liquefied gas receiving pipe in the low temperature liquefied gas tank in which the low temperature liquefied gas is received inside the tank through the receiving reed pipe. The receiving lead tube is eccentrically installed so that the upper end of the tube is positioned, and the low temperature liquefied gas that has flowed down from the low temperature liquefied gas receiving tube is accumulated at the upper end of the receiving lead tube and then overflowed and received. A liquid storage container for allowing the liquid to flow into the lead pipe is attached, and the lower end of the low temperature liquefied gas receiving pipe is positioned in the liquid storage container. A device for preventing boil-off gas entrainment in a low-temperature liquefied gas tank, characterized in that the low-temperature liquefied gas that has flowed down is stored in a liquid storage container and then overflowed to be received in a low-temperature liquefied gas tank through a receiving lead pipe. . 6. A position between the lower end of the low temperature liquefied gas receiving pipe and the upper end of the receiving lead pipe inside the liquid holding container, higher than the inlet of the receiving lead pipe and higher than the upper side surface of the liquid holding container. The boil-off gas for a low-temperature liquefied gas tank according to claim 5, wherein the weir having a height that becomes low is installed in a single or multiple manner so as to surround the circumference of the receiving reed tube so that the low-temperature liquefied gas overflows in multiple stages. Entrainment prevention device.