JPS6231240B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating method for preventing freezing of soil around underground tanks storing cryogenic liquids such as liquefied natural gas.

Tanks for storing low-temperature liquids such as liquefied natural gas are often built underground for safety or construction reasons.

These tanks store liquids at temperatures exceeding -160°C, which freezes the surrounding soil.

If this freeze expands, it may affect the foundations of other structures.

As a countermeasure to this problem, it is considered that heating objects such as hot water pipes and heating wires are placed around the tank to prevent cold air from being discharged from the tank.

Furthermore, creating a cylindrical groove surrounding the tank to create a gap between the tank and the surrounding soil is effective in terms of thermal insulation, and the combination of this and the heating medium Consideration has been given to taking countermeasures.

When this cavity and a heating medium are combined, the heating medium is installed inside or outside the groove, but the air or other fluid in the cavity is heated by the heating, and the bottom and top of the groove are heated by convection. However, there is a problem in that a considerable temperature difference occurs, and the heating is not uniformly propagated in the circumferential direction, but only the upper part is heated, making it impossible to perform efficient heating.

The purpose of the present invention is to eliminate the drawbacks of the prior art described above, eliminate the difference in temperature in the cylindrical groove around the tank, and uniformly propagate the amount of heating without requiring any complicated auxiliary equipment. The purpose is to provide a new heating method that can effectively heat the surrounding area of a tank. Moreover, a groove is provided that is in a sealed or nearly sealed state, and a heating object is placed inside or outside the groove, and a vertical partition wall is provided to heat the interior space of the groove that is in a sealed or nearly sealed state. The present invention provides a method for heating a peripheral area of a low-temperature liquid storage underground tank, which is characterized by forcibly circulating a fluid by only heating the fluid.

The heating method of the present invention will be described below with reference to the accompanying drawings.

Figure 1 shows a storage system in which a tank 1 is completely buried underground.A cylindrical groove 3 is provided in a concrete foundation 2 around the tank 1 to surround the tank 1. 1 and the surrounding soil, and can also function as a protective groove in the event that low-temperature liquid leaks.

A heating element 4, 4' such as a heater or hot water is inserted into the concrete foundation 2 on the inside or outside of the groove 3.

By adopting such a configuration, it is possible to freeze the surrounding soil and cut off the cold air of the low-temperature liquid that affects the foundations of the surrounding structures.

FIG. 2 shows a semi-underground storage tank, and the same parts as in FIG. 1 are given the same reference numerals.

Figure 3 shows the A-A' section in Figure 1 or the second B-
It shows a cross section B', and the same parts as in FIGS. 1 and 2 are given the same reference numerals.

FIG. 4 is a detailed view of the groove 3 provided in the foundation 2 at the periphery of the cryogenic liquid storage underground tank 1 as described above, and the groove 3 is sealed by closing the opening at the upper end with a suitable lid. In this sealed groove 3, a vertical partition wall 6 is installed vertically with its top and bottom separated from the inner surface of the groove.

With this configuration, the fluid such as air in the groove 3 is forcibly circulated around the vertical partition wall 6 in the direction of the arrow by the heating of the heating element 4' provided along the groove 3. This eliminates the temperature difference between the upper and lower portions of the groove 3, making it possible to achieve uniform heating.

In order to demonstrate such uniform heating, first, for the purpose of comparison with the method of the present invention, a heating experiment was conducted by vertically inserting a heater into a 5 m tube with an inner diameter of 50 mmφ.

It was found that when the heater surface was heated to about 100℃, the temperature difference between the top and bottom of the tube reached 15 to 20 degrees.

Therefore, it is clear that in the groove 3, which is as long as 20 to 30 meters, there will naturally be a large temperature difference between the upper and lower sides.

In the above experiment, when a partition wall 6 was provided inside the tube in its longitudinal direction, a substantially uniform temperature was obtained from above and below, and it was confirmed that the effect of the partition wall was obtained.

According to the heating method of the present invention as described above, the convection of the fluid in the cylindrical and sealed groove around the tank provided in combination with the heating medium is caused by the convection of the fluid in the vertical groove provided in the groove. Because it is forcibly circulated up and down the groove by heating along the bulkhead, it is extremely simple and does not require large-scale incidental equipment such as installing new forced circulation equipment with a separate circulator. This process eliminates the temperature difference between the top and bottom of the groove and enables uniform heating in the circumferential direction of the tank.Therefore, it is of great industrial value as an economical and efficient heating method for the surrounding area of this type of tank. There is something big.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional explanatory diagram showing an embodiment of a tank for storing low-temperature liquids in a fully underground method; FIG. 2 is a cross-sectional explanatory diagram showing an example of a tank for storing low-temperature liquids in a semi-underground method; The figure is A- in Figure 1.
A' or a cross-sectional explanatory diagram taken along the line B-B' in Fig. 2,
FIG. 4 is a cross-sectional explanatory diagram showing an embodiment of the method of heating the peripheral area of a tank according to the present invention. 1: Tank, 2: Concrete foundation, 3:
Groove, 4, 4': heating object, 6: longitudinal partition.

Claims (1)

[Claims] 1. A cylindrical groove surrounding an underground tank for storage of low-temperature liquids is provided around the tank, and the groove is sealed or nearly sealed, and a heated object is placed inside or outside the groove. , Heating of the surrounding area of an underground tank for storing low temperature liquids, characterized in that the internal space of the trench is closed or close to closed, and a vertical partition is provided to forcefully circulate the heated fluid only by the heating. Method.