JPS6131359B2 - - Google Patents

Description

[Detailed Description of the Invention] In recent years, petroleum has gradually been replaced as an energy source.
It is well known that the demand for LPG, LNG, etc. is increasing, and that LNG is especially attracting attention as it is non-polluting and high in calories. these
When storing LPG, LNG, etc., it is generally more economical to store them as liquids rather than gases, so it is common to store them in liquefied form. Tanks for storing these low-temperature liquids (for example, in LNG, the main component is methane, and the gas turns into a liquid at -162°C) can be either single-shelled or double-shelled depending on the temperature of the substance's content. However, in any case, a cold storage structure is used to suppress intrusion heat during storage and prevent evaporation loss. Tanks with a double shell cold storage structure are suitable for storing substances such as LNG, LPG, ethylene, oxygen, nitrogen, etc. whose boiling points are below -40 degrees Celsius, and there are tank types such as spherical and flat-bottom cylindrical types.

For example, a tank with a double shell dome roof type structure shown in FIG. 1 is well known as a typical tank for storing LNG at present.

The present invention relates to an improvement of this double shell dome roof type cold storage tank, and aims to provide a tank that is safer and easier to maintain and inspect than conventional tanks.

Now, as for the current double shell flat bottom cylindrical tank,
One example is the double dome roof tank shown in Figure 1 as mentioned above.In this type of tank, mild steel is generally used for the outer tank A and the inner tank B.
For low temperature materials, 9% Ni steel, stainless steel, aluminum alloy, aluminum killed steel, etc. are mainly used. In this case, the inner tank has an air-tight and liquid-tight structure, and the outer tank A has a structure that holds the cold insulator and maintains the airtightness of the inert gas. That is, the cold insulation space between the outer tank A and the inner tank B is generally filled with powdered pearlite C, but since this powdered pearlite is hygroscopic,
The structure is such that an inert gas such as nitrogen is injected to prevent the intrusion of large particles, and also to prevent ignition due to minute leakage of contents. This type of tank with a double dome roof is generally constructed in earthquake-prone countries such as Japan.

Another type of double shell flat bottom cylindrical tank is a suspended roof type double tank in which the inner tank roof D is not dome-shaped but is suspended from the outer tank roof E, as shown in Figure 2. This structure is a shell tank, and this structure is advantageous in terms of economy when the tank becomes larger, and is often constructed in areas where there is no risk of earthquakes. In a tank having this structure, the vapor contained in the liquid is kept airtight in the outer tank. Insulating material F is also placed uniformly on the suspended roof to provide insulation. Furthermore, in recent years, it has become more common to store the above-mentioned low-temperature liquids underground, and one example of this is the membrane-type underground tank G, which has a good track record in Japan, as shown in Figure 3. The roof part is the same as the above-ground type shown in Figure 2, but the concrete frame H in the underground part is used as a strength member, and the membrane J installed through the insulation material is installed as an airtight and liquid-tight material. ing.

The advantages of this type of underground tank include that even if a leakage accident occurs, the liquid can be prevented from flowing out, a dike is required, and the psychological impact on residents is alleviated. However, at present, there is still a demand for above-ground tanks because the construction cost is relatively high compared to above-ground tanks of the same capacity, and because they are strongly affected by soil quality, there are difficulties in dealing with the effects of soil pressure. There are many.

The present application essentially relates to an improvement of the above-mentioned above-mentioned above-ground double dome type cryogenic liquid storage tank, which improves the various drawbacks of the conventional tanks shown in Figs. 1, 2 and 3. This invention relates to a storage tank.

Now, to explain one example, a floating bed foundation 2 is provided on the site 1, and a tank bottom foundation 3 is placed on the floating bed foundation 2.
An outer tank bottom plate 4 is fixed on the tank bottom foundation 3, and a cylindrical outer tank side plate 5 is fixed upright on the outer tank bottom plate 4. ) A bottom heat insulating material 6 is provided on the outer tank bottom plate 4, a bottom heat insulating layer 7 is laid inside the annular bottom heat insulating material 6, and an inner tank bottom plate 8 is provided over the entire surface of the annular bottom heat insulating material 6 and the bottom heat insulating layer 7. At the same time, a cylindrical inner tank side plate 9 is erected and fixed on the inner tank bottom plate 8.

The bottom heat insulating material 6 is made of a material with relatively high thermal conductivity or has a structure that allows forced heat supply.

A cylindrical liquid storage tank side plate 10 having a diameter smaller than that of the inner tank side plate 9 is provided inside the inner tank side plate 9. However, in order to provide the liquid storage tank side plate 10, a cylinder slightly larger than the diameter of the liquid storage tank side plate 10 is placed on the inner tank bottom plate 8. An anti-slip material 11 with a diameter of
2, and the liquid storage tank side plate 10 is erected and fixed on the liquid storage tank bottom plate 12.

A dome-shaped inner tank roof 13 is located at the upper end of the inner tank side plate 9.
is fixed, and a heat insulating material 1 is placed between the outer tank side plate 5 and the inner tank side plate 9.
Further, a dome-shaped outer tank roof 15 is fixed to the upper end of the outer tank side plate 5, and a heat insulating material 16 is also filled between the inner tank roof 13 and the outer tank roof 15.

Furthermore, bumpers 17 are provided in several stages vertically and in a cylindrical direction between the inner tank side plate 9 and the liquid storage tank side plate 10,
The base of the bumper 17 is fixed to the inner tank side plate 9.

Further, a sealing plate 18 is fixed to the end of the liquid storage tank bottom plate 12 and the inner tank bottom plate 8 to keep the anti-slip member 11 airtight.

19 is a bottom drain nozzle that opens into the inner tank bottom plate 8 between the inner tank side plate 9 and the liquid storage tank side plate 10, and a valve 20
The storage liquid 21 is drawn out to the outside through the storage liquid 21 so that it can be recovered in the event that a large amount of the stored liquid 21 leaks. 22
One end is fixed to the lower part of the inner tank side plate 9 with an anchor, and the other end is fixed to the tank bottom foundation 3.

In addition, it is effective to use a bumper 17 that has some elasticity, and in this case, it is necessary to apply stress so that when the liquid storage tank side plate 10 is deformed by an earthquake or the like and the bumper 17 is contracted, it can be restored. It is something that works.

26 is the top garter.

In addition, the liquid storage tank 25 is formed of a strength member that is liquid-tight, and the inner tank 23 is normally a primary barrier against stored liquid vapor, and a secondary barrier to liquid-tightness in the event that liquid leaks from the liquid storage tank side plate 10. It is made of a strength member designed as a barrier.

The outer tank 24 plays the role of holding heat insulating material and keeping inert gas airtight, and is designed to be used at room temperature. Liquid storage tank 25
If the bottom plate 12 of the inner tank 23 and the bottom plate 8 of the inner tank 23 are used as a single-layer bottom plate, there is a risk that high stress will be generated at the joint between the lower part of the side plate 10 and the bottom plate, and the effect of the secondary barrier will be reduced. It is made up of three layers with an anti-slip material 11 such as asphalt felt interposed between them.

There is no insulation material between the inner tank 23 and the liquid storage tank 25, and the space is filled with the vapor of the stored liquid, and the temperature approaches the storage temperature. If liquid leaks from the inner tank 25, the inner tank 23 becomes a secondary barrier that maintains liquid tightness.

The outer tank 24 is also effective as a secondary barrier against vapor leakage.

Due to the above-mentioned configuration, in the present application, when liquid leaks from the liquid storage tank 25, the inner tank 23 maintains the liquid tightness, and there is no instantaneous mass evaporation due to leakage, and there is no risk that the internal pressure of the inner tank 23 will rise rapidly. The inner tank 23 is a stable structure and can prevent secondary damage due to gas diffusion, and is effective as a secondary barrier in terms of airtightness.

Next, when the tank according to the present application is subjected to an earthquake force, it is common to have a structure that prevents liquid from overflowing due to the sloshing phenomenon, but since there is a secondary barrier against leakage, overflow is actively caused and the side plate The extra space at the top can be reduced.

In this respect, the structure shown in Figure 2 has the disadvantage that the inner tank roof D is destroyed and the insulation material F falls, and depending on the release speed, it may be released to the outside of the inner tank B, destroying the outer tank A and causing the side In addition to disasters caused by leakage of insulation material C,
There is also a risk of secondary damage due to poor insulation.

Furthermore, with the structure of the present invention, deformation of the tank that occurs due to sloshing can be prevented by the upper bumper 17 attached to the inner tank 23 without providing a large top girder.

However, the bumper 17 can be attached in multiple stages depending on the expected deformation.

In addition, during an earthquake, the liquid storage tank 25 moves separately from the bottom plate 8 on the anti-slip material 11 at the bottom, which is effective against the sliding phenomenon.
It can be attenuated by

The lower bumper 17 is attached to the inner tank 23, but since it has almost the same temperature as the liquid storage tank 25, it can be provided in contact with the side plate 10 of the liquid storage tank 25, thereby reducing deformation of the side plate 10 due to liquid pressure. This makes it possible to reduce local stress generated at the joint between the side plate 10 and the bottom plate 12.

The present application is also concerned with leakage from the top of the liquid storage tank 25 due to sloshing, which is relatively likely to occur.
The liquid accumulated between the inner tank 23 and the inner tank 23 can be evaporated by making the bottom insulation material 6 provided under this space a material with relatively high thermal conductivity or a structure that can forcibly supply heat. Recovery is possible by

Furthermore, by providing the drain nozzle 19 at the bottom of the space between the inner tank 23 and the liquid storage tank 25, it is possible to easily recover a large amount of leakage using the drain nozzle 19 without installing an expensive pump or the like.

In the present application, since the liquid storage tank 25 is further provided inside the inner tank 23, it is easy to open and inspect the inner and outer surfaces of the side plate 10 after draining the liquid in the liquid storage tank 25, and it is possible to inspect both sides of the primary barrier at a low cost. It is.

Additionally, an outer tank 24, an inner tank 23, and a liquid storage tank 25
The triple shell structure eliminates the need for a dike K, resulting in savings in construction costs.

The present application relates to a double dome type tank in which the bottom side and the upper part are double-layered inside and outside with a heat insulating layer interposed therebetween, and a liquid storage tank bottom plate is provided on the inner tank bottom plate with an anti-slip material interposed therebetween, and the liquid The liquid storage tank side plate is erected and fixed on the storage tank bottom plate at a constant distance from the inner tank side plate, and the height of the liquid storage tank side plate is set to a height that is maintained at a constant distance from the inner tank roof, so it has the following characteristics.

The air-tight outer tank acts as a secondary barrier against vapor, and the air-tight and liquid-tight inner tank acts as a primary barrier against vapor and a secondary barrier against liquid. The storage tank acts as a primary barrier against liquid, and has three layers: an outer tank that acts as a secondary barrier against vapor, an inner tank that acts as a primary barrier against vapor and a secondary barrier against liquid, and a liquid storage tank that acts as a primary barrier against liquid. Since it has a shell structure, it has double safety against liquid and airtightness, and a liquid storage tank bottom plate 12 is provided on the inner tank bottom plate with an anti-slip material,
The liquid storage tank can slide on the anti-slip material separately from the inner tank bottom plate, and can absorb the horizontal force during an earthquake without restricting the movement of the liquid storage tank bottom plate.

In addition, since the liquid storage tanks are formed at regular intervals within the inner tank, it is easy to inspect the interior, and the triple shell structure prevents large amounts of evaporation due to liquid leakage, making it safe in terms of gas diffusion. Because of its structure, there is no need for a dike, which can save construction costs and land.

Although the above-ground floating floor type cylindrical tank is shown in the embodiment of the present invention, the present invention also applies to a so-called underground type floating floor tank in which the tank of the embodiment is directly buried from above ground to underground. Although it is applicable and does not affect the structure of the present invention in any way, it is applicable not only to the floating floor type of this embodiment as a tank foundation but also to a flat foundation with a heater. There is no question that even in the case of a flat foundation with a heater, it can be applied not only to above-ground tanks but also to underground tanks.

[Brief explanation of the drawing]

1 to 3 are sectional views of a conventional storage tank, FIG. 4 is a sectional view of the storage tank of the present invention, and FIG. 5 is a partially enlarged sectional view of FIG. 4.

Claims (1)

[Claims] 1. In a double dome type tank in which the bottom side and the upper part are formed double inside and outside with a heat insulating layer in between, a liquid storage tank bottom plate is provided on the inner tank bottom plate with an anti-slip material in between, and the inner tank is placed on the liquid storage tank bottom plate. The liquid storage tank side plate is erected and fixed at a constant distance from the side plate, the height of the liquid storage tank side plate is set to a height that maintains a constant distance from the inner tank roof plate, and the liquid storage tank bottom plate slides at least separately from the anti-slip material. A low temperature liquid storage tank comprising: