JPS6014240B2 - Underground storage tank for low temperature liquefied gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an underground storage tank for storing low-temperature liquefied gas such as LNG and LPG, and more specifically, the underground storage tank is This invention relates to an underground storage tank for low-temperature liquefied gas that is equipped with a temperature control device to prevent the ground in which it is buried from freezing and the moat to develop unnecessarily and to keep the growth of the moat to a finite limit.

In underground storage tanks that store low-temperature liquefied gases such as LNG and LPG, the ground around the underground storage tanks freezes due to the cold heat of the stored liquid.

This ground freezing phenomenon is not necessarily disadvantageous for underground storage tanks; in fact, freezing systems developed around storage tanks are of high value from the safety standpoint. This is because when the ground freezes, its strength increases and it also becomes liquid-tight and air-tight. However, on the other hand, when soil freezes, an expansion action called freeze expansion occurs, and this freeze expansion causes various harmful phenomena. That is, external pressure acting on the storage tank, movement of equipment surrounding the storage tank, frost heaving of the storage tank itself, etc. For this reason, the ground around the underground storage tank for low-temperature liquefied gas needs to be frozen to suppress the development of frozen soil and prevent freeze expansion. Conventionally,
As a method to control the development of such moated soil, there is a known method of burying a heater in the ground with a predetermined distance between it and the storage tank, and preventing the moat from spreading beyond the area where the heater is buried due to the amount of heat generated by this heater. It is being However, this type of heat fence method, which controls the temperature of the ground around the storage tank by applying heater heat to the storage tank from outside the storage tank, can reliably prevent the moat from spreading unnecessarily. but,
On the one hand, the ground between the storage tank and the heater is heated from the side where the heater is buried, and on the other hand, the cold heat of the stored liquid is directly transferred to the ground near the storage tank and is cooled from the storage tank side. When heated from one side and cooled from the other side, an ice mass (ice lens) is formed within this ground,
It is also possible that the ice layer continues to grow, causing freeze expansion. The present invention has been made in order to solve such conventional problems, and the ground around the main body is heated to a predetermined temperature of 0°C on the wall of the main body of the underground tank for low-temperature liquefied gas or on the ground adjacent to this main body. Freezing of the ground surrounding the underground storage tank is achieved by installing a temperature control device buried therein, and using a plurality of underground temperature sensors buried in a predetermined array in the ground surrounding the underground storage tank. By precisely controlling this from the storage tank itself, we can proactively utilize the benefits of the cryostat, reliably suppress freeze expansion, and control harmful phenomena that occur due to freeze expansion. An object of the present invention is to provide an underground storage tank for low-temperature liquefied gas that prevents the gas from spreading unnecessarily.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In the figure, 1 is a concrete circular underground storage tank body buried in the ground 2 with its upper part protruding above the ground. Although it is not covered, a heat insulating material is attached, and a membrane is placed on this heat insulating material, allowing LNG and LP to be stored inside.
A low-temperature liquefied gas such as G is accommodated. A plurality of temperature control pipes 5 are embedded in the side wall 4 of the storage tank body 1, each extending approximately the entire length of the side wall 4 and spaced apart from each other at approximately equal intervals along the circumferential direction. Each of these control pipes 5 is
Outer pipes 5 each having an open upper end and a closed lower end.
The inner pipe 5b has a double pipe structure in which an inner pipe 5b whose upper and lower ends are closed is inserted into the inside of the outer pipe 5a (the inner circumferential surface of the outer pipe 5a and the inner pipe The lotus is suitable for the gap between 5b and the outer peripheral surface. The upper portions of both the pipes 5a and 5b respectively protrude outward from the upper end of the side wall 4, and the protruding upper end of the inner pipe 5b is connected to the antifreeze supply pipe 8 that passes the pump 7, and the outer pipe The protruding upper ends of the tubes 5a are connected to antifreeze discharge pipes 9, and one end of the antifreeze supply channel pipe 8 is connected to an antifreeze tank (not shown), and the antifreeze in this tank is supplied by the operation of the pump 7. The liquid flows into the inner pipe 5b through the pipe 8, flows through the outer pipe 5a from the lower end entrance 6, and is then discharged into the discharge pipe 9. The pump 7 is operated according to instructions from a pump automatic control unit 11 according to the temperature at a predetermined location in the ground 2 detected by an underground temperature sensor 10 buried in the ground 2 on the side of the storage tank body 1. ,
Its capacity is varied so that the flow rate of the antifreeze fluid is automatically controlled. The underground overflow sensor 10 is a first
As is clear from the figure, a plurality of them are buried at intervals along the direction away from the storage tank body 1. In other words, these underground temperature sensors 10 are buried in an array form along the thickness direction of the base plate 2a extending from the periphery of the storage tank body 1. Next, the operation of the underground storage tank for low temperature liquefied gas having the above configuration will be explained.

First, by operating the pump 7, antifreeze such as prine is caused to flow from the antifreeze tank into the inner pipe 5b through the supply pipe 8, and then from the lower end entrance 6 to the outer pipe 5a and into the discharge pipe 9. In this way, the antifreeze liquid is circulated within the temperature control pipe 5. In this case, the antifreeze solution circulates at a temperature of 0° C. or lower and higher than the temperature of the liquid stored in the underground storage tank body 1 for low-temperature liquefied gas, such as LNG or LPG. As a result, the cold heat of the liquid stored in the storage tank body 1 is transferred to the wall body, but a part of the cold heat transferred to the side wall 4 is heat exchanged with the antifreeze flowing in the pipe 5, and is absorbed by the antifreeze. It is carried outside of Ground 2.

Therefore, all of the cold heat of the stored liquid is prevented from being directly transmitted to the ground 2 from the wall of the storage tank main body 1, and the flow rate of the antifreeze liquid is ``determined by the temperature, etc., below 0°C and higher than the storage liquid temperature. The amount of heat at a predetermined temperature that is appropriately controlled depending on the condition of the ground 2 is transferred, and the ground 2 around the storage tank body 1 is thereby frozen.In this case, the leakage temperature sensor 10 buried in the ground 2: 2. The temperature at a predetermined location is measured, and the thickness of the loose soil 2a is measured. Based on the instructions, the automatic control device 11 operates to adjust the capacity of the pump 7 and the flow rate of the antifreeze. A plurality of underground temperature sensors 10 arranged along the thickness direction of the frozen soil 2a measure the temperature of each buried location.Therefore, from these measurement signals, it is possible to know changes in the thickness of the frozen soil 2a in extremely detailed manner. Moreover, the derived situation, that is, the change in the state of the frozen soil 2a, can be known in detail one by one.Therefore, the automatic control device 11 finely adjusts the capacity of the pump 2 based on this information, and The development of the loose soil 2a can be reliably controlled.In this respect, the automatic control device 11 can be said to be a control unit that controls the temperature. If only one underground temperature sensor is installed at the same location, the accuracy of detecting the thickness of Chishi 2a will be low, and the
The ability to control the development of children will be impaired. In this way,
The automatic control device 11 performs detailed and accurate temperature control based on detection signals from the plurality of underground temperature sensors 10.

As a result, the amount of cold heat from the storage tank body 1 into the ground 2 can be freely controlled, the development of the ice cubes 2a is controlled, the thickness of the ice cubes 2 is kept constant, and the formation of ice blocks (ice lenses) is controlled. , growth is controlled and freeze expansion is reliably suppressed. Therefore, the underground tank for low-temperature liquefied gas is stably supported by the moat 2a, which has high strength and is liquid-tight and air-tight, without being subjected to harmful effects such as frost heaving caused by freezing and expansion. Ru. In the above embodiment, the temperature control pipe was buried only in the side wall of the storage tank body, but it is also possible to bury the temperature control pipe in the bottom wall of the storage tank body. Instead of burying the control pipe, the pipe may be buried in a U-shape, a serpentine shape, etc.

Furthermore, the temperature control device is not limited to one with a pipe structure, and can be modified in various ways. It will be done in such a way that it will be done. Further, in the above embodiment, the temperature control pipe is buried in the side wall of the storage tank body, but the temperature control device is not limited to this, and the temperature control device may be buried in the ground close to the storage tank body. Various modifications may be made without departing from the gist of the invention.
As explained above, the present invention has a temperature control device buried in the wall of the main body of an underground storage tank for low-temperature liquefied gas or in the ground adjacent to the main body of the underground storage tank to control the ground around the main body to a predetermined temperature of 000 or less. , the freezing of the ground around the main body is controlled from the main body side, and a plurality of underground temperature sensors are arranged in the ground around the main body in a direction away from the main body. Bury it,
Since the temperature control device is configured to be controlled based on the detection signals from the plurality of underground temperature sensors, changes in the thickness of the refrigeration layer can be controlled based on the detection signals from the plurality of underground temperature sensors. It is possible to perform detailed temperature control based on detailed information, and as a result, it is possible to reliably prevent the unnecessarily developing of the freezing layer around the storage tank body, maintain a constant thickness of the freezing layer, and reduce backlogs. This method has advantages such as being able to reliably suppress freezing expansion and preventing harmful phenomena that occur due to freezing expansion, and making it possible to effectively utilize the benefits of a cryotechnologist.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG.
It is a sectional view along line 0-0 of FIG. 1... Underground storage tank body for low temperature liquefied gas, 2...
...Ground, 2a...Soji, 4...Side wall, 5...Temperature control pipe. Figure 1 Figure 2

Claims (1)

[Claims] 1. Has a temperature control device buried in the wall of the underground storage tank body for low-temperature liquefied gas or in the ground adjacent to the underground storage tank body, and this temperature control device keeps the ground around the underground storage tank body at a temperature of 0°C or less. In an underground storage tank for low-temperature liquefied gas, where the temperature is controlled to a predetermined level to maintain a constant thickness of frozen soil in the ground surrounding the underground storage tank body, the temperature in the ground around the underground storage tank body is measured. A plurality of underground temperature sensors are buried at intervals along the direction away from the underground storage tank body, and the temperature is controlled by measuring the thickness of the frozen soil based on the detection signals of these underground temperature sensors. An underground storage tank for low-temperature liquefied gas, characterized in that it has a control section that controls the temperature of the device.