JP2020186790A - Thermal insulation material for liquefied natural gas tank and method for constructing the same, and liquefied natural gas tank - Google Patents

Abstract

To provide a thermal insulation material for a liquefied natural gas tank which is controlled from cracking, detachment or the like even when a significant thermal shrinkage occurs in a steel plate of a liquefied natural gas tank, and is facilitated in construction.SOLUTION: A thermal insulation material 20 is provided at an outside surface of a tank steel plate 121 for a liquefied natural gas tank. The thermal insulation material 20 includes resin foam 22, 24. The thermal insulation material 20 has a density gradient of the resin foam 22, 24 where the density decreases from a side of the tank steel plate 121 toward the outside.SELECTED DRAWING: Figure 2

Description

The present invention relates to a heat insulating material for a liquefied natural gas tank, a method of constructing the same, and a liquefied natural gas tank. The present invention relates to a heat insulating material for a liquefied natural gas tank, a construction method thereof, and a liquefied natural gas tank provided with the heat insulating material.

An LNG carrier that transports or uses liquefied natural gas (hereinafter sometimes referred to as LNG) is equipped with an LNG tank that stores a cryogenic LNG as high as -163 ° C. Standards for LNG tanks have been set by the International Maritime Organization (IMO), of which the self-supporting tank system is a complete secondary barrier type A, a partial secondary barrier type B, and a pressure vessel that does not require a secondary barrier. There are each type C LNG tank.

The type C LNG tank is generally mounted on a non-large vessel and is made of steel that can sufficiently withstand the internal pressure of the LNG. Further, since LNG has an extremely low temperature as described above, a large number of heat insulating material boards made of, for example, resin foam are provided on the outer surface of the type C LNG tank.

However, the conventional heat insulating material board has a problem that cracks and peeling are likely to occur. The reason is that the steel LNG tank contracts remarkably due to the cryogenic LNG existing inside, and the heat insulating board cannot follow the contracted steel.
On the other hand, if a large number of heat insulating material panels are provided on the outer surface of the LNG tank, there is also a problem that the heat insulating effect is lowered due to the fixing portion between the LNG tank and the heat insulating material panel and the joint portion of the heat insulating material panel.

In order to solve such a problem, for example, in Patent Document 1 (Japanese Unexamined Patent Publication No. 6-74394), glass wool is attached to the outer surface of the tank steel plate, and glass cloth is attached and fixed on the glass wool. A metal tank for low-temperature storage, which comprises spraying a resin foam material on the glass cloth, attaching a wire mesh made of a corrosion-resistant metal on the sprayed resin foam material, and spraying the resin foam material again from the wire mesh. The cold insulation structure of is disclosed.
However, even with the technique disclosed in Patent Document 1, there are still problems of cracking and peeling of the resin foam material due to shrinkage of the steel sheet, and there is a problem that the construction is also expensive.

Japanese Unexamined Patent Publication No. 6-74394

Therefore, an object of the present invention is to provide a heat insulating material for a liquefied natural gas tank and a method for constructing the same, in which cracks and peeling are suppressed even when a remarkable heat shrinkage occurs in the steel plate of the liquefied natural gas tank, and construction is easy. ..
Another object of the present invention is to provide a liquefied natural gas tank provided with the heat insulating material in which cracks, peeling and the like are suppressed even when a remarkable heat shrinkage occurs in the steel plate of the liquefied natural gas tank.

As a result of intensive research, the present inventors have found that the above problems can be solved by using a resin foam whose density decreases from the tank steel plate side to the outside as a heat insulating material, and have completed the present invention. It was.
That is, the present invention is as follows.

1. 1. A heat insulating material provided on the outer surface of the steel plate of a liquefied natural gas tank.
The heat insulating material contains a resin foam and contains.
The heat insulating material is a heat insulating material for a liquefied natural gas tank, which has a density gradient in which the density of the resin foam decreases from the tank steel plate side to the outside.
2. 2. The heat insulating material for a liquefied natural gas tank according to 1 above, wherein the resin foam is a polyurethane foam.
3. 3. The insulation is outward from the tank steel plate side, the 1 or 2, characterized in that it has a density gradient that density decreases in the range of 80kg ^/ m ³ ~30kg / m 3 resin foam The heat insulating material for the liquefied natural gas tank described.
4. The heat insulating material for a liquefied natural gas tank according to any one of 1 to 3 above, wherein the thickness of the heat insulating material is in the range of 300 mm to 500 mm.
5. The heat insulating material has a density gradient in which the density of the resin foam gradually decreases from the tank steel plate side to the outside by being composed of a plurality of layers of resin foam having different densities in the thickness direction. The heat insulating material for a liquefied natural gas tank according to any one of 1 to 4 above.
6. The heat insulating material for a liquefied natural gas tank according to any one of 1 to 5, wherein a glass mesh is provided so as to have a plane in a direction orthogonal to the thickness direction of the heat insulating material.
7. It has a heat insulating material forming step of providing a heat insulating material containing a resin foam on the outer surface of the tank steel plate of the liquefied natural gas tank.
A method for constructing a heat insulating material for a liquefied natural gas tank, wherein the heat insulating material has a density gradient in which the density of the resin foam decreases from the tank steel plate side to the outside by the heat insulating material forming step.
8. The resin foam is a polyurethane foam and
The heat insulating material forming step includes a spraying step of spraying the polyurethane foam.
In the spraying step, polyurethane foams having different densities are sprayed a plurality of times to form a heat insulating material on the outer surface of the tank steel sheet.
The heat insulating material for a liquefied natural gas tank according to the above 7, wherein the heat insulating material forms a density gradient in which the density of the polyurethane foam decreases from the tank steel plate side to the outside by the spraying step. Construction method.
9. The heat insulating material for a liquefied natural gas tank according to any one of 1 to 5 is provided on the outer surface of the tank steel plate, and the heat insulating material has a density in which the density of the polyurethane foam decreases from the tank steel plate side to the outside. A liquefied natural gas tank characterized by having a gradient.
10. The liquefied natural gas tank according to 9 above, which is fixed to a ship.
11. The liquefied natural gas tank according to the above 10, which is a type C.

The heat insulating material for a liquefied natural gas tank of the present invention is provided on the outer surface of the tank steel plate of the liquefied natural gas tank, contains a resin foam, and has a density gradient in which the density of the resin foam decreases from the tank steel plate side to the outside. Therefore, even if the steel sheet of the liquefied natural gas tank undergoes remarkable heat shrinkage, the high-density resin foam follows the heat shrinkage of the steel sheet and suppresses cracking and peeling of the heat insulating material. it can. Further, the high-density resin foam lowers the heat insulating property, but the low-density resin foam has excellent heat insulating property, so that the above-mentioned drawbacks of the high-density resin foam can be compensated. Further, since the density of the resin foam can be easily controlled by the amount of the foaming agent, the workability is also excellent.
Further, the method for constructing the heat insulating material for a liquefied natural gas tank of the present invention includes a heat insulating material forming step of providing a heat insulating material containing a resin foam on the outer surface of the tank steel plate of the liquefied natural gas tank, and the heat insulating material forming step is used. The heat insulating material is characterized by having a density gradient in which the density of the resin foam decreases from the tank steel plate side to the outside, so that the construction is easy and the cost is excellent. Further, even when a remarkable heat shrinkage occurs in the steel plate of the liquefied natural gas tank, cracks and peeling of the heat insulating material can be suppressed.
Further, since the liquefied natural gas tank of the present invention is characterized by providing the heat insulating material of the present invention, cracks and peeling are suppressed even when a remarkable heat shrinkage occurs in the steel plate of the liquefied natural gas tank. It also has excellent heat insulation and workability.

It is a figure for demonstrating the type C liquefied natural gas tank which can be applied to this invention. It is sectional drawing for demonstrating the heat insulating material for a liquefied natural gas tank of this invention. It is sectional drawing for demonstrating another form of the heat insulating material for a liquefied natural gas tank of this invention. It is sectional drawing for demonstrating another form of the heat insulating material for a liquefied natural gas tank of this invention.

Hereinafter, embodiments of the present invention will be further described with reference to the drawings.
1A and 1B are views for explaining a type C liquefied natural gas tank that can be applied to the present invention, FIG. 1A is a longitudinal side view of the liquefied natural gas tank, and FIG. 1B is a liquefied natural gas tank. It is a front view in the radial direction of.

In FIG. 1, the type C liquefied natural gas tank (LNG tank) 1 includes a cylindrical pressure vessel 12, and the pressure vessel 12 is supported by a gantry 14. Generally, a type C LNG tank has a capacity of 30 to 10,000 m ³ , and the number of tanks is one or more. The pressure vessel 12 is made of a steel plate such as aluminum, stainless steel, or nickel steel.

As an example of the thermal expansion / contraction characteristics of a steel plate in the pressure vessel 12, when LNG having an extremely low temperature of -163 ° C. is stored in a pressure vessel made of stainless steel, the stainless steel is thermally shrunk by about 3 mm per 1 m.

The heat insulating material of the present invention is provided on the outer surface of the pressure vessel 12.
FIG. 2 is a cross-sectional view for explaining the heat insulating material of the present invention.
In FIG. 2, in the heat insulating material 20 of the present invention, resin foams 22 and 24 are provided on the steel plate 121 of the pressure vessel from the steel plate 121 side toward the outside (A direction), and the density of the resin foam 24 is determined. It is set lower than the density of the resin foam 22. That is, the heat insulating material 20 of the present invention has a density gradient in which the density of the resin foam decreases from the steel plate 121 side of the pressure vessel toward the outside (A direction). Further, a reinforcing layer 26 made of FRP (fiber reinforced plastic) or polyurea resin may be provided on the upper portion of the resin foam 24, that is, on the outermost surface side of the heat insulating material, for the purpose of further suppressing cracks and peeling.

In the present invention, the heat insulating member 20 is outwardly from the steel plate 121 ^side, preferably has a density gradient where the density of the resin foam is reduced in the range of ^{80kg / m 3 ~30kg / m 3} . By setting the density in this way, cracks and peeling of the heat insulating material can be further suppressed.

The density referred to in the present invention is generally measured by JIS K 7222 "Foam Plastics and Rubber-How to Obtain Apparent Density".

For example, in the embodiment shown in FIG. 2, the density of the resin foam 22 is, for ^{example, 35kg / m 3 ~80kg / m 3} , preferably from ^{50kg / m 3 ~65g / m 3} . The density of the resin foam 24 is, for example, ^{30kg / m 3 ~55kg / m 3} , preferably from ^{35kg / m 3 ~50kg / m 3} . The density difference between the resin foam 22 and 24 is, for example, ^{5kg / m 3 ~25kg / m 3} , preferably from ^{10kg / m 3 ~20kg / m 3} .

The total thickness of the heat insulating material 20 of the present invention is preferably 300 mm to 500 mm, more preferably 350 mm to 450 mm.

In the form shown in FIG. 2, the thickness of the resin foam 22 is, for example, 20 mm to 100 mm, preferably 40 mm to 80 mm. The thickness of the resin foam 24 is, for example, 200 mm to 480 mm, preferably 250 mm to 450 mm.

The heat insulating material of the present invention is not limited to the form shown in FIG. For example, as shown in FIG. 3, n layers of heat insulating material are interposed between the resin foam 22 and the resin foam 24, and the density of the resin foam gradually decreases from the steel plate 121 side to the outside. It may have a density gradient. In this form, it is possible to deal with pressure vessels of various shapes, and it is possible to suppress cracking and peeling of the heat insulating material. In addition, n is preferably 0 to 4.

As described above, the heat insulating material of the present invention is composed of a plurality of layers of resin foams having different densities in the thickness direction, so that the density of the resin foams gradually decreases from the tank steel plate side to the outside. It is preferable to have a density gradient. According to such a form, the construction is easy and the cracking and peeling of the heat insulating material can be satisfactorily suppressed.

Further, according to another aspect of the present invention, the glass mesh may be provided so as to have a plane in a direction orthogonal to the thickness direction of the heat insulating material. According to such a form, cracking and peeling of the heat insulating material are further suppressed. FIG. 4 is a cross-sectional view for explaining the heat insulating material of the present invention provided with the glass mesh. A glass mesh 42 is provided between the resin foam 22 and the resin foam 24. The mesh width of the glass mesh 42 is, for example, 5 mm to 15 mm, preferably 7.5 mm to 12.5 mm. In such a glass mesh 42, when n layers of heat insulating material are interposed between the resin foam 22 and the resin foam 24 as shown in FIG. 3, layers having different densities are laminated. The glass mesh 42 may be installed each time.

The resin foams 22 and 24 are preferably two-component polyurethane foams from the viewpoint of good followability to heat shrinkage of the steel sheet 121 and from the viewpoint of excellent workability.

The density of the polyurethane foam can be controlled by the injection amount of a foaming agent (for example, hydrofluorocarbon HFC, water, etc.).

The tensile strength of the resin foam 22 is preferably 20 to 55 N / cm ² at room temperature (20 ° C.), for example, from the viewpoint of further suppressing cracking and peeling, and the tensile strength of the resin foam 24 is , 10 to 35 N / cm ² , preferably.
Tensile strength is generally measured by JIS A 9511 "foamed plastic thermal insulation material".

The method for constructing the heat insulating material for a liquefied natural gas tank of the present invention includes a heat insulating material forming step of providing a heat insulating material containing a resin foam on the outer surface of the tank steel plate of the liquefied natural gas tank, and the heat insulating material forming step is described. The heat insulating material is characterized by having a density gradient in which the density of the resin foam decreases from the tank steel plate side to the outside.
In a particularly preferable construction method, the resin foam is a polyurethane foam, the heat insulating material forming step includes a spraying step of spraying the polyurethane foam, and the spraying step involves spraying polyurethane foams having different densities a plurality of times. A heat insulating material is formed on the outer surface of the tank steel plate by spraying, and the heat insulating material forms a density gradient in which the density of the polyurethane foam decreases from the tank steel plate side to the outside by the spraying step. It is that.
Known techniques can be applied to the spraying of polyurethane foam. For example, a method in which polyurethane foam is made into a two-component type, the two-component is agitated while controlling pressure and temperature, and sprayed by spraying can be mentioned.

Further, for example, the resin foams 22 and 24 may be formed by spraying the resin foams 22 and 24 a plurality of times until the respective foams have a predetermined thickness. For example, when the thickness of the resin foam 22 is thick (for example, about 100 mm), the thickness of one spray is 40 mm or less, and by repeating this spraying a plurality of times, the resin foam 22 is formed to a predetermined thickness (100 mm). can do. The same applies to the layers of other foams.

The liquefied natural gas tank of the present invention is characterized by comprising the heat insulating material of the present invention. That is, the heat insulating material of the present invention is provided on the outer surface of the tank steel plate, and the heat insulating material has a density gradient in which the density of the polyurethane foam decreases from the tank steel plate side to the outside. The LNG tank of the present invention is preferably a type C LNG tank fixed to a ship. As described above, the type C LNG tank can take various shapes depending on the size of the ship, etc., but when the heat insulating material of the present invention is applied, the steel plate of the LNG tank undergoes remarkable heat shrinkage. However, cracks and peeling are suppressed.

By storing LNG in a type C LNG tank and using a heat insulating material having a density gradient in which the density of the resin foam decreases from the steel plate side of the pressure vessel to the outside, the present inventors can make the steel plate. It has been confirmed that the heat insulating material does not crack or peel even when heat-shrinked.
Specifically, in the form shown in FIG. 2, two-component polyurethane foams are used as the resin foams 22 and 24, the density of the resin foam 22 is 60 kg / m ³ , and the density of the resin foam 24 is 40 kg / m. ^It has been confirmed that when the total thickness of the heat insulating material is set to ³ and the total thickness of the heat insulating material is 400 mm, the heat insulating material does not crack or peel even if the steel plate is thermally shrunk.

1 Type C liquefied natural gas tank 12 Pressure vessel 14 Stand 20 Insulation material 22 of the present invention Resin foam 24 Resin foam 26 Reinforcing layer 121 Steel plate 42 Glass mesh

Claims (11)

A heat insulating material provided on the outer surface of the steel plate of a liquefied natural gas tank.
The heat insulating material contains a resin foam and contains.
The heat insulating material is a heat insulating material for a liquefied natural gas tank, which has a density gradient in which the density of the resin foam decreases from the tank steel plate side to the outside. The heat insulating material for a liquefied natural gas tank according to claim 1, wherein the resin foam is a polyurethane foam. The insulation is from said tank steel plate side toward the outside, 80 kg / m 3 30 kg ^/ claims density of the resin foam in the range of m ³ is characterized by having a density gradient that decreases 1 or 2 Insulation material for liquefied natural gas tanks described in. The heat insulating material for a liquefied natural gas tank according to any one of claims 1 to 3, wherein the thickness of the heat insulating material is in the range of 300 mm to 500 mm. The heat insulating material has a density gradient in which the density of the resin foam gradually decreases from the tank steel plate side to the outside by being composed of a plurality of layers of resin foam having different densities in the thickness direction. The heat insulating material for a liquefied natural gas tank according to any one of claims 1 to 4. The heat insulating material for a liquefied natural gas tank according to any one of claims 1 to 5, wherein a glass mesh is provided so as to have a plane in a direction orthogonal to the thickness direction of the heat insulating material. It has a heat insulating material forming step of providing a heat insulating material containing a resin foam on the outer surface of the tank steel plate of the liquefied natural gas tank.
A method for constructing a heat insulating material for a liquefied natural gas tank, wherein the heat insulating material has a density gradient in which the density of the resin foam decreases from the tank steel plate side to the outside by the heat insulating material forming step. The resin foam is a polyurethane foam and
The heat insulating material forming step includes a spraying step of spraying the polyurethane foam.
In the spraying step, polyurethane foams having different densities are sprayed a plurality of times to form a heat insulating material on the outer surface of the tank steel sheet.
The heat insulating material for a liquefied natural gas tank according to claim 7, wherein the heat insulating material forms a density gradient in which the density of the polyurethane foam decreases from the tank steel plate side to the outside by the spraying step. Construction method. The heat insulating material for a liquefied natural gas tank according to any one of claims 1 to 5 is provided on the outer surface of the tank steel plate, and the density of the polyurethane foam of the heat insulating material decreases from the tank steel plate side to the outside. A liquefied natural gas tank characterized by having a density gradient. The liquefied natural gas tank according to claim 9, which is fixed to a ship. The liquefied natural gas tank according to claim 10, which is of type C.

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