JPH067279Y2 - Gythering prevention device for low temperature tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is intended for cooling and holding a liquid receiving pipe having a horizontal portion and a rising portion in a low temperature tank for storing a low temperature liquid such as LNG (liquefied natural gas). The present invention relates to a device for preventing Gethering of a low temperature saturated liquid to be put therein, and particularly to prevent heat accumulation due to heat input from a horizontal portion.

[Conventional technology]

When the cryogenic liquid contained in the vertical pipe is heated without being sufficiently mixed, the liquid inside the pipe is subjected to pressure according to the height of its liquid column and its boiling point rises. When the liquid is removed or the temperature of the liquid rises above the saturation temperature corresponding to the above pressure with the passage of time, a sudden boiling state may occur, and this phenomenon is called Geyser ring.

For example, even in the low temperature storage facility for storing LNG shown in FIG. 2, a liquid receiving pipe 2 is provided in the LNG tank 1 for receiving LNG carried by a ship, and an end of a horizontal portion 2a parallel to the ground is provided. A rising portion 2b that is vertically raised is formed to communicate with the roof, and LNG is stored from the upper portion of the LNG tank 1. The liquid receiving pipe 2 has an LN
There is a rising portion 2b that is parallel to and perpendicular to the side wall of the G tank 1.

In such a liquid receiving pipe 2, LNG flowing inside is -16.
Since it is a low temperature saturated liquid of about 3 ° C., it is necessary to cool it to a low temperature state at the time of receiving it. Normally, the LNG bottom receiving pipe 3 is provided between the lower part of the LNG tank 1 and the horizontal part 2a of the liquid receiving pipe 2 to obtain the LNG. It keeps it cool by keeping it inside.

Therefore, the vertical rising portion 2b of the liquid receiving pipe 2 always contains LNG which is a low temperature saturated liquid, and the rising portion 2b
There is invasion heat not only from b but also from the horizontal portion 2a.

In the horizontal portion 2a where the low temperature saturated liquid in the liquid receiving pipe 2 is heated, the heated liquid accumulates above the center line,
This flows toward the free surface of the rising portion 2b. In the rising portion 2b, an ascending flow further heated at the outer peripheral portion is generated,
On the other hand, a downflow is generated in the central part.

Therefore, at the lower end of the rising portion 2b of the liquid receiving pipe 2, a horizontal flow in the horizontal portion 2a collides with a downward flow of the rising portion 2b, smooth convection does not occur, and a Geysering phenomenon may occur. is there.

[Problems to be solved by the invention] However, when a Geysering phenomenon occurs in the liquid receiving pipe 2 of the LNG cryogenic storage facility, a large amount of LNG is pushed up by the boiling gas and the gas entering the LNG tank 1 There is a problem that the internal pressure rises or the LNG that is pushed up and then dropped causes a water hammer phenomenon to vibrate the LNG tank 1 and the liquid receiving pipe 2.

Therefore, as a method of preventing Geyser ring, a part of LNG discharged from the LNG tank 1 is diverted and put into the liquid receiving pipe 2 for forced circulation, or a small-diameter heating pipe is provided below the liquid receiving pipe. In some cases, a part of LNG in the liquid receiving pipe is heated by outside air or another heating source and stirred by boiling gas (Jitsuko Sho 62-31756).
issue).

However, in the case of forced circulation of LNG, the liquid receiving pipe 2
Because of the large diameter of LNG, it is necessary to circulate a large amount of LNG, and there is a problem that the power cost of the pump and the like required for this will be incurred annually. Therefore, when a pipe for heating is installed, the size of the liquid receiving pipe must be large. Depending on the situation, if the outside air is used as the heat source, it may be difficult to secure the necessary stirring gas, or a heating source must be provided separately.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a Geysering preventive device for a low temperature tank that can easily prevent Geysering by smoothly performing convection in the liquid receiving tube caused by intrusion heat. Is.

[Means for Solving the Problems]

In order to solve the problems of the above-mentioned prior art, the device for preventing Geyzer ring of a low temperature tank of the present invention is a low temperature equipped with a liquid receiving pipe having a horizontal portion for cooling and holding the low temperature saturated liquid and a rising portion rising therefrom. In the tank, an inner pipe for rectifying upflow and downflow is provided in the rising part of the liquid receiving pipe, and the lower end of this inner pipe is located in the center of the horizontal part, while the liquid level of the cryogenic tank is set in this inner pipe. It is characterized in that a communication hole for forming a free liquid surface corresponding to the above is formed.

[Action]

One of the causes of the Geysering phenomenon is that not only the heat input from the rising part of the liquid receiving pipe but also the heat input from the horizontal part cannot be released smoothly, and the heat is accumulated in the lower end part of the rising pipe. To be

Therefore, according to the Geysering prevention device for this low temperature tank, the inner pipe is mounted in the rising portion of the liquid receiving pipe, and the lower end portion thereof is below the center of the horizontal pipe to form the double pipe structure, and The communication hole is formed so that the liquid surface in the rising portion moves according to the liquid surface in the low temperature tank.

Therefore, the liquid in the horizontal portion and the rising portion heated by the invasion heat can be raised on the outer peripheral side of the inner pipe, and the heat is released to cause the heavy liquid to flow on the inner peripheral side of the inner pipe. Therefore, heat is released at the free liquid surface of the horizontal portion and the rising portion to prevent Geyser ring.

Further, it is possible to prevent the occurrence of Geyser ring without changing the external shape of the liquid receiving tube.

〔Example〕

An embodiment of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 (a) and 1 (b) relate to an embodiment of a Geyser ring prevention device for a cryogenic tank according to the present invention. FIG. 1 (a) is a schematic configuration diagram, and FIG. 1 (b) is an enlarged liquid receiving pipe. FIG.

In this Geyser ring prevention device 10, the inner pipe 11 is mounted in the vertical rising portion 2b of the liquid receiving pipe 2 of the LNG tank 1 to have a double pipe structure, and the lower end of the inner pipe 11 is the horizontal portion 2
It is located at the center of a.

Further, the inner pipe 11 has a predetermined gap formed between the inner pipe 11 and the inner portion of the liquid receiving pipe 2, and the outer peripheral portion of the inner pipe 11 serves as an ascending flow path for the heated LNG. Are arranged so as to form a descending flow path of LNG that releases heat.

Further, in the inner pipe 11, a large number of communication holes 12 are formed in the side wall along the semicircle of the spiral so as to overlap at least at one position in the pipe axial direction, and depending on the liquid level of the LNG in the LNG tank 1. Regardless of the changing liquid level in the rising pipe 2b,
The liquid level in the inner pipe 11 is always the same as that of the rising pipe 2b, and a fin 12a having an open upper end is attached to the outer side of the communication hole 12 so that the fluid that rises along the inner pipe 11 is attached. Therefore, the descending fluid can be drawn into the inner peripheral portion of the inner pipe 11.

The inner pipe 11 is made of the same material as the liquid receiving pipe 2 such that it does not interfere with the low temperature liquid.

On the other hand, the lower end portion of the rising pipe 2b is formed with a bulging portion in order to compensate for the decrease in the cross-sectional area of the horizontal portion 2a due to the insertion of the inner pipe 11, so that the flow of the heated LNG flowing in the horizontal portion 2a is not hindered. I am doing it.

According to the Geysering prevention device 10 for such a low temperature tank, when the low temperature saturated liquid is completely received from the ship and then the receiving port is closed, the LNG bottom receiving pipe 3 fills the liquid receiving pipe 2 with the stored liquid. It will be in the state of being always
The liquid surface of the tank 1 and the liquid surface of the inner pipe 11 in which the rising pipe 2b and the communication hole 12 are formed are the same.

In such a state, the horizontal portion 2a of the liquid receiving pipe 2 is exposed to the outside air.
When the low temperature saturated liquid in the rising portion 2b is heated, natural convection causes a fluid having a high temperature to flow upward from the central portion toward the rising pipe 2b in the horizontal portion 2a.

On the other hand, in the rising portion 2b, the heated fluid having a high temperature rises in the outer peripheral portion, and the fluid having a low temperature drawn into the inner pipe 11 through the communication hole 12 descends in the inner peripheral portion.

In this case, since the inner pipe 11 is provided in the rising portion 2b and the lower end of the inner pipe 11 is located at the center of the horizontal portion 2a, the liquid having a high temperature flowing in the horizontal portion 2a is not connected to the outer circumference of the inner pipe 11. The fluid that has risen between the rising portions 2b and whose heat input is released at the free liquid surface passes through the communication hole 12 and the inner pipe 1
A circulating flow is generated which descends from the inner peripheral portion of 1 and flows from the lower end portion to the tip portion of the liquid receiving tube 2 below the central portion of the horizontal portion 2a.

Therefore, the two fluids flowing in the horizontal portion 2a and the rising portion 2b of the liquid receiving pipe 2 do not collide with each other at the lower end portion of the rising pipe 2b, flow in a state of being rectified by the inner pipe 11, and are caused by the heat entering from the outside. Convection is smoothed to prevent heat accumulation in the fluid and prevent Geiser ring.

In the above embodiment, the liquid receiving pipe of the LNG low temperature tank has been described, but the present invention is not limited to this, and can be widely applied to a liquid receiving pipe for keeping a low temperature saturated liquid such as an LPG low temperature tank. .

Further, the lower end of the inner pipe has only to be located at the center of the horizontal portion, that is, near the center, and is not necessarily located at the center.

Further, the communication hole is not limited to the combination of the spiral hole and the fin as in the embodiment, and it is sufficient to form a hole that continuously communicates in the axial direction of the pipe, and the fin is not necessarily provided. good.

Further, in the above-mentioned embodiment, the lower end of the liquid receiving pipe is thickened to secure the cross-sectional area of the flow path. However, when the diameter of the pipe is large, it is not necessary to particularly thicken it.

[Effect of device]

As described above in detail with reference to the embodiment, according to the Geysering prevention device for a cryogenic tank of the present invention, the inner pipe is mounted in the rising part of the liquid receiving pipe, and the lower end of the inner pipe is lower than the center of the horizontal pipe. Since it has a double pipe structure so that it is on the side, and the communication hole is formed so that the liquid level in the rising part moves according to the liquid level in the low temperature tank, the horizontal part and the rising part heated by the intrusion heat are formed. Liquid can be raised on the outer peripheral side of the inner pipe, and heat can be released and the lightened liquid can flow on the inner peripheral side of the inner pipe, rectifying the flow of the horizontal part and the rising part, It is possible to prevent the collision and to release the heat at the free liquid surface of the rising portion to prevent Geisering.

Further, only by mounting the inner tube inside the liquid receiving tube, there is no need to change the external shape, and it is possible to easily prevent the occurrence of Geyser ring without problems such as securing a mounting space.

[Brief description of drawings]

FIGS. 1 (a) and 1 (b) relate to an embodiment of a Geyser ring prevention device for a cryogenic tank according to the present invention. FIG. 1 (a) is a schematic configuration diagram, and FIG. 1 (b) is an enlarged liquid receiving pipe. Sectional view, second
FIG. 1 is a schematic configuration diagram of an LNG cryogenic tank which is one application example of the present invention. 1: LNG tank, 2: Liquid receiving pipe, 2a: Horizontal part, 2
b: rising part, 3: LNG bottom receiving pipe, 10: low temperature tank geisering prevention device, 11: inner pipe, 12: communication hole, 12a: fin.

Claims (1)

[Scope of utility model registration request] 1. A liquid receiving pipe having a horizontal portion for cooling and holding a low-temperature saturated liquid and a rising portion rising therefrom, the free liquid surface of the rising portion being at the same level as the liquid surface of a tank. In a low-temperature tank provided with an inner pipe for rectifying an ascending flow and a descending flow in the rising part of the liquid receiving pipe,
The lower end of the inner pipe is located below the center of the horizontal part, and at the same time, the inner pipe is formed with a communication hole that communicates the inside and outside of the inner pipe with the free liquid surface at any liquid surface position in the rising portion. Anti-geyzering device for low temperature tanks.