JPH0416054Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to a cold storage structure for a cryogenic tank for storing cryogenic liquids, particularly a double-shell cryogenic tank in which an inner tank and an outer tank are arranged concentrically. .

(Prior Art) FIG. 2 is a sectional view showing a conventional cold insulation structure of this type of double-shell cryogenic tank.

That is, by filling the space formed between the inner tank 22 that substantially accommodates the cold and hot liquid 21 and the outer tank 23 disposed outside the inner tank 22 with a granular cold insulating material 24 such as perlite powder, cold storage is achieved. It maintained its functionality.

However, it is difficult to fill the space between the inner and outer tanks with the granular cold insulating material at a uniform density, and the granular cold insulating material settles and consolidates over time, causing unnecessary stress to be applied to the inner tank 22. In some cases, the inner tank may be destroyed. In addition, due to sedimentation and compaction, voids are generated in the upper part of the granular cold insulating material layer, resulting in a significant decrease in heat insulation properties.

Furthermore, in low-temperature tanks with conventional structures, once the granular cold insulating material is filled, it is difficult to remove it. However, it was not possible to inspect directly from the outside, and it was necessary to remove a huge amount of cold insulation material in advance.

In addition, in conventional double-shell low-temperature tanks, in the unlikely event that the inner tank 2
2, the low-temperature storage liquid 21 is ejected into the space between the inner and outer tanks while removing the cold insulating material around the broken part, and instantaneously reaches and contacts the outer tank 23.

At this time, the outer tank 23, which is made of ordinary steel that does not have low-temperature toughness, contracts and breaks due to the thermal shock, and the low-temperature liquid 21 flows out of the tank, resulting in secondary,
There was also the risk of inviting a third disaster.

Furthermore, if a fire breaks out outside the tank, there is a fatal flaw in that it is easily affected by the heat. In other words, in double-shell low-temperature tanks in which urethane foam is placed directly on the inner surface of the outer tank as an insulating material, the urethane is damaged by the heat of the outer tank, which has become hot due to heat radiation from a fire, and the insulation function is lost. A large amount of boil-off gas is generated due to the intrusion of heat.

Note that even if the outer tank 23 is not damaged, the low-temperature liquid that leaked between the inner and outer tanks pushes the granular cold insulating material 24, which has a light specific gravity (the apparent specific gravity of perlite powder is about 0.07), upward. At the same time, the flammable gas evaporates, increasing the pressure in the space between the inner and outer tanks, damaging the roof that is equipped with many attached equipment, and further igniting the flammable gas that leaks outside.
There was a risk of explosion or fire.

In addition, all of the stored liquid that has been gasified in the space between the inner and outer tanks is collected by the leakage gas exhaust device and safety device installed on the roof, and then guided to the flare stack or vent stack installed outside the tank, so that it can be thoroughly disposed of. If planned, the scale of the equipment and the diameter of the piping would be enormous, requiring huge equipment costs, which would be uneconomical.

(Problems to be Solved by the Invention) The purpose of the present invention is to solve the problems of the double-shell cryogenic tank having a cold insulation structure based on the above-mentioned conventional technology. In other words, even though it is assumed that the low-temperature storage liquid will inevitably leak out from the inner tank due to unforeseen circumstances, the leaked liquid can be stored reliably and safely in the space between the inner and outer tanks, and heat input from the outside can be prevented as much as possible. This is a safe cold storage structure that suppresses the vaporization of the effluent liquid, prevents destruction of the tank body, and prevents vaporized gas from dissipating to the outside, and provides a cold storage structure that is easy to construct.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention is a low-temperature tank consisting of a double shell of an inner and outer tank. A cold insulation layer of hard polyurethane foam is further formed on the inner surface of the heat insulating layer to maintain a predetermined maintenance space from the inner tank.

In other words, on the inner surface of the outer tank, a heat-resistant layer, a heat-insulating layer, and
It has a three-layer structure with a cold insulation layer, and a predetermined maintenance space is provided between the cold insulation layer and the inner tank.

(Function) As mentioned above, the cold storage structure of the double-shell low-temperature tank of the present invention includes a heat-resistant layer, a heat-insulating layer, and a heat-insulating layer on the inner surface of the outer tank.
In addition to the three-layer structure of the cold insulation layer, the cold storage structure consists of a maintenance space formed between the cold insulation layer and the inner tank, so even if the low-temperature storage liquid in the inner tank leaks into the space, it will come into contact with the cold storage layer. The outer tank will not be subjected to low-temperature thermal shock, and even if the outer tank heats up due to a fire near the tank, the heat-resistant layer and heat insulating layer will protect the urethane cold insulation layer, and the urethane cold insulation layer will not be damaged. Since heat intrusion into the inner tank is prevented without causing heat leakage, the amount of boil-off from the liquid stored in the inner tank is suppressed.

Furthermore, even when the heat insulating layer is formed of flat foamed glass, the flat foamed glass is attached to the inner surface of the outer tank through a heat-resistant layer of glass wool, so even if the outer tank is distorted, With the help of the elastic heat-resistant layer, the heat insulating layer can be attached closely to the outer tank without creating any gaps that would cause variations in the heat insulating effect.

Further, the space provided between the cold insulation layer and the inner tank is used for maintenance and inspection of the inner tank during tank operation without removing the cold insulation layer.

(Example) Next, an example of the present invention will be described based on the drawings.

FIG. 1 is a sectional view of a low-temperature tank implementing the cold storage structure of the present invention.

Reference numeral 1 denotes an inner tank that substantially contains a low-temperature liquid 7 such as liquefied gas, and is made of low-temperature steel such as 9% nickel steel or aluminum killed steel, which has excellent low-temperature toughness. An outer tank 2 is installed to cover the inner tank 1 at a predetermined distance from the inner tank 1, and is made of ordinary steel or the same low-temperature steel material as the inner tank 1 described above.

3 is a heat-resistant layer of glass wool attached to the inner surface of the outer tank 2, and usually has a thickness of about 10 to 30 mm.

Note that the material of the heat-resistant layer 3 may be any heat-resistant material having elasticity, and for example, rock wool or the like may be used.

4 is a heat insulating layer of foam glass, such as Foam Glass (manufactured by Pittsburgh Corning), which is attached to the inner surface of the heat-resistant layer 3. The material is usually formed into a flat plate with a thickness of about 50 mm, and is assembled in sequence. To construct. The material is fixed by a locking metal fitting 6 protruding from the inner surface of the outer tank 2.

Here, the heat-resistant layer 3 not only has the function of blocking heat flowing into and out of the tank, but also has the function of absorbing construction errors in the distance between the outer tank 2 and the heat insulating layer 4. That is,
The size of the gap between the outer tank 2 and the heat insulating layer 4 due to the distortion caused during the assembly process and the difference in curvature between the outer tank 2 and the heat insulating layer 4 can be fixed by filling the gap with elastic glass wool. Therefore, the influence of the gap on heat transfer can be reduced.

Reference numeral 5 denotes a cold insulation layer made of hard polyurethane foam formed on the inner surface of the heat insulating layer 4, and is usually constructed to a thickness of about 300 mm. This cold insulation layer 5 may be assembled by stacking ready-made blocks, but the
After installing a foam mold 8 made of a thin metal plate at a position of a predetermined thickness as shown in the figure, the gap between the foam mold 8 and the heat insulating layer 4 may be formed by foaming urethane at the assembly site.

H is a maintenance space provided between the inner tank 1 and the cold insulation layer 5, and when inspecting and repairing the inner tank 1 from the outside, it is wide enough (usually 900 to 1000mm).

By the way, the inner surface of the outer tank 2 of the double-shell low-temperature tank has a three-layer structure consisting of a heat-resistant layer 3, a heat-insulating layer 4, and a cold-insulating layer 5, and a maintenance space H is provided between the inner tank 1 and the cold-insulating layer 5. By using the built-in cold storage structure, even if the inner tank were to crack or damage during operation and the stored liquid leaked into the maintenance space H, the ejected dynamic pressure would be formed in a solid form. It only contacts the cold insulation layer 5 made of polyurethane and does not directly apply low-temperature thermal shock to the outer tank 2. As a material for the outer tank 2, low-temperature resistance is not necessary, and inexpensive ordinary steel is sufficient, but if you dare to use expensive low-temperature steel as the material for the outer tank 2,
The three-layer structure of heat resistance, heat insulation, and cold storage, together with the outer tank 2 made of low-temperature steel, double prevents the low-temperature storage liquid from leaking out, thereby providing double safety.

(Effects of the invention) As mentioned above, the cold insulation structure of the double-shell cryogenic tank of the present invention consists of a heat-resistant layer, a heat insulation layer, and a cold insulation layer assembled in this order on the inner surface of the outer tank, and between the cold insulation layer and the inner tank. Since it has a cold storage structure with a maintenance space, it has the following effects.

First, the cold insulation layer of Utan foam, which is relatively heat-resistant, is protected by a heat-resistant layer of glass wool and a heat-insulating layer of foam glass, so if a fire breaks out near the tank, the radiant heat from the fire will raise the temperature of the outer tank to a high temperature. However, the heat is blocked by the heat resistant layer and the heat insulating layer, and its influence is less likely to affect the urethane cold insulation layer. Therefore, the amount of heat that enters the inner tank is small, and the amount of boil-off of low-temperature liquid is suppressed as much as possible, making it possible to reduce the amount of gas generated in the event of an accident and emergency. The capacity of an exhaust gas treatment device such as a stack can be set small, and the equipment cost can be reduced.

Furthermore, the cold storage structure of the present invention uses a structure in which the foam glass insulation layer is attached to the inner surface of the outer tank via the glass wool heat-resistant layer, so the adhesion of the insulation layer to the outer tank is excellent. And success is easy.

In other words, the outer tank is constructed by rolling a metal plate material to a certain curvature and then welding it on site, so distortion due to welding is unavoidable.On the other hand, commercially available foam glass insulation materials are made of almost flat plates. Because they are molded into a shape, if they are pasted together directly, there will be variations in size in the gap, making it difficult to achieve uniform insulation performance.However, in this invention, the gap is filled with elastic glass wool. By forming the heat-resistant layer, both the outer tank and the heat insulating layer can be formed without gaps, and the heat insulating performance becomes uniform.

In addition, in this invention, a maintenance space is provided between the inner tank and the cold storage layer, so even when the tank is in operation,
The inner tank can be inspected without removing the cold insulation layer.

As is clear from the above explanation, the cold storage structure of the present invention is excellent in safety and workability, and has structural features not found in conventional double-shell cryogenic tanks.

[Brief explanation of the drawing]

Figure 1 is an enlarged sectional view showing the cold insulation structure of the double-shell cryogenic tank of the present invention, and Figure 2 is the cold insulation structure of the conventional double-shell cold tank (granular pearlite cold insulation material).
FIG. 1...Inner tank, 2...Outer tank, 3...Heat-resistant layer of glass wool, 4...Insulating layer of foam glass, 5...Cold layer of polyurethane foam, 6...Locking metal fittings,
7... Low temperature liquid, 8... Form frame, H... Maintenance space, 21... Low temperature liquid, 22... Inner tank, 23
... Outer tank, 24 ... Granular cold insulation material.

Claims (1)

[Scope of utility model registration request] In a double-shell cryogenic tank, an outer tank is provided on the outside of an inner tank that houses a low-temperature liquid, and covers the inner tank at a predetermined interval.A heat-resistant layer of glass wool is interposed on the inner surface of the outer tank, and a heat-insulating layer of foam glass is placed on the inner surface of the outer tank. A cold insulation structure for a double-shell low temperature tank, characterized in that a cold insulation layer of hard polyurethane foam is formed on the inner surface of the heat insulation layer, maintaining a predetermined maintenance space from the inner tank.