JP2020104884A - Double shell tank - Google Patents

Abstract

To provide a double shell tank which can achieve both of forming a heat insulation layer between an inner tank and an outer tank by a granular heat insulation material, and of holding a heat insulation layer having a suitable thickness at a tank top part even after the granular heat insulation material has settled due to shrinkage deformation of the inner tank.SOLUTION: A double shell tank comprises: a spherical shell-shaped inner tank in which a storage part for storing a liquid in a tightly closed state is formed; an outer tank which covers the inner tank; and a granular heat insulation material which is filled in a space surrounded by an external wall of the inner tank and an internal wall of the outer tank, and forms a heat insulation layer. A size of an apex gap between the inner tank and the outer tank is a value, in which a level difference of the granular heat insulation material between the state that the inner tank is empty and the state that the inner tank accommodates the liquid is added to a size of a bottom gap between the inner tank and the outer tank, or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to the structure of a double shell tank including an outer tank and an inner tank.

Conventionally, a double-shell tank has been known as a tank for storing a low temperature liquid. The double-shell tank is generally formed between an inner tank that substantially contains a cryogenic liquid, an outer tank that covers the inner tank from the outside at a predetermined interval, and an inner tank and an outer tank. And a heat insulating layer. The heat insulating layer is formed of, for example, a granular heat insulating material filled between the inner tank and the outer tank, and pearlite is used as the granular heat insulating material.

During the construction of the double shell tank, after the inner tank and the outer tank are completed, the granular heat insulating material is filled so as to fill the space between the inner tank and the outer tank with the inner tank being empty. Therefore, when the low temperature liquid is supplied to the inner tank and the inner tank thermally contracts, the gap between the inner tank and the outer tank widens, and the granular heat insulating material filled between the inner tank and the outer tank may settle. There is a nature. When the granular heat insulating material settles, a space free of the granular heat insulating material is created at the tank top of the double shell tank, and the thickness of the heat insulating layer at the tank top is reduced. When a portion of the double-shell tank where the thickness of the heat insulating layer is insufficient occurs, the heat insulating property of the portion deteriorates. Due to the decrease in heat insulation, the cold heat of the inner tank may be transferred to the outer tank, and the outer tank may be frosted to cause corrosion of the outer tank. Further, if the heat input to the inner tank increases due to the decrease in heat insulation, the amount of boil-off gas of the low-temperature liquid may increase, and the pressure in the inner tank may become excessive.

Therefore, in the double shell tank of Patent Document 1, an inner heat insulating layer formed of a stretchable material (glass wool) that can expand and contract in the radial direction of the inner tank, and an outer heat insulating layer formed of a filler (perlite) The heat insulating layer is composed of two inner and outer layers. In this double-shell tank, the expansion material expands the gap generated in the heat insulation layer due to the thermal contraction of the inner tank, and the sedimentation of the filler is suppressed.

JP, 2013-238285, A

Especially for double shell tanks installed outdoors, it is important to suppress the heat input to the top of the tank due to solar radiation. Nevertheless, if the heat insulating layer between the inner tank and the outer tank is formed by the granular heat insulating material, the heat insulating property of the tank top is lowered by the sedimentation of the granular heat insulating material as described above.

According to the double-shell tank of Patent Document 1, although the settling of the granular heat insulating material (filler) can be suppressed, the cost increases due to the large use of glass wool, which is more expensive than perlite.

The present invention has been made in view of the above circumstances, and an object thereof is to form a heat insulating layer between an inner tank and an outer tank by means of a granular heat insulating material, and to reduce the particle size due to shrinkage deformation of the inner tank. It is an object of the present invention to provide a double-shell tank capable of maintaining a heat insulating layer having an appropriate thickness on the tank top even after the heat insulating material has settled.

The double shell tank according to one aspect of the present invention is
A spherical shell-shaped inner tank in which a storage unit for storing liquid in a sealed state is formed,
An outer tank covering the inner tank,
A granular heat insulating material filled in a space surrounded by the outer wall of the inner tank and the inner wall of the outer tank to form a heat insulating layer,
The size of the top clearance between the inner tank and the outer tank is the size of the bottom clearance between the inner tank and the outer tank, and the inner tank is empty and the inner tank contains the liquid. And the level difference of the granular heat insulating material are added or more.

According to the above double-shell tank, since the size of the top gap is larger than the size of the bottom gap, a heat insulating layer that is thicker than the bottom of the tank is formed on the top of the tank when the inner tank is empty. Then, when the low temperature liquid is supplied to the inner tank and the inner tank contracts, the gap between the inner tank and the outer tank widens, and the granular heat insulating material filled between the inner tank and the outer tank sinks, Even when the granular heat insulating material is settled, a heat insulating layer having a sufficient thickness is retained on the top of the tank. Therefore, according to the above double-shell tank, the heat insulating layer is formed between the inner tank and the outer tank by the granular heat insulating material, and the tank is maintained even after the granular heat insulating material is settled due to the contraction deformation of the inner tank. It is possible to maintain the heat insulating layer having an appropriate thickness on the top.

In the double shell tank, the outer tank may have a spherical shell shape, and the center of the outer tank may be located above the center of the inner tank.

In this way, by eccentricizing the center of the inner tank downward with respect to the center of the outer tank, both the outer tank and the inner tank have a spherical shell shape with excellent strength, but the top clearance between the inner tank and the outer tank is reduced. The size can be made larger than the size of the bottom clearance between the inner tank and the outer tank.

Alternatively, in the double-shell tank, the outer tank includes a lower hemispherical shell portion, an upper hemispherical shell portion, and a tubular body portion connecting the lower hemispherical shell portion and the upper hemispherical shell portion, The center of the tank and the center of the lower hemispherical shell may coincide with each other.

As a result, below the equator of the inner tank, a heat insulating layer having a constant thickness is formed around the equator. A heat insulating layer thicker than the heat insulating layer below the equator of the inner tank is formed above the equator of the inner tank. The outer tank has a shape similar to a spherical shell, and the outer tank can have sufficient strength.

Alternatively, in the double-shell tank, the outer tank is composed of a main body having a spherical shell shape and a dome portion provided on the top of the main body and filled with the granular heat insulating material, and the center of the inner tank. The center of the main body may be aligned.

In this way, since the dome portion filled with the granular heat insulating material is provided on the top of the main body portion of the outer tank, the inner tank is contracted and deformed to be filled between the inner tank and the main body portion of the outer tank. Even if the granular heat insulating material settles, the settled portion is supplemented by the granular heat insulating material filled in the dome portion. Therefore, even when the granular heat insulating material is settled, the heat insulating layer having a sufficient thickness is retained at the top of the tank.

According to the present invention, a heat insulating layer is formed between the inner tank and the outer tank by the granular heat insulating material, and an appropriate thickness is provided on the tank top even after the granular heat insulating material is settled due to the shrinkage deformation of the inner tank. It is possible to provide a double-shell tank that is compatible with maintaining the heat insulating layer of the shell.

FIG. 1 is a sectional view showing the overall configuration of an empty double shell tank according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view of the double shell tank showing a state in which the low temperature liquid is supplied to the inner tank shown in FIG. FIG. 3 is a cross-sectional view showing the overall configuration of an empty double shell tank according to the second embodiment of the present invention. FIG. 4 is a cross-sectional view of the double shell tank showing a state where the low temperature liquid is supplied to the inner tank shown in FIG. FIG. 5: is sectional drawing which shows the whole structure of the empty double shell tank which concerns on 3rd Embodiment of this invention. FIG. 6 is a cross-sectional view of the double shell tank showing a state in which the low temperature liquid is supplied to the inner tank shown in FIG.

[First Embodiment]
Next, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the overall structure of an empty double-shell tank 1A according to the first embodiment of the present invention, and FIG. 2 is a view in which a low temperature liquid 7 is supplied to an inner tank 2 shown in FIG. It is sectional drawing of the double shell tank 1A which shows the opened state.

The double shell tank 1A shown in FIGS. 1 and 2 is a tank for storing a low temperature liquid 7 such as liquid hydrogen, liquid nitrogen, and liquefied natural gas. The double-shell tank 1A is installed on the hull, the ground, or the like while being supported by a skirt or a pillar (not shown).

The double shell tank 1A includes an inner tank 2, an outer tank 3 that covers the inner tank 2, a granular heat insulating material 4 that is filled between the inner tank 2 and the outer tank 3 to form a heat insulating layer, and an inner tank 2 A vacuum pump 6 for vacuuming the space between the outer tank 3 and the outer tank 3 is provided.

The inner tank 2 has a hollow spherical shell shape, and is formed by welding a large number of SUS panels, for example. Inside the inner tank 2, a storage section 21 for storing the low temperature liquid 7 in a sealed state is formed. The inner tank 2 can allow the contraction deformation and the deformation recovery due to the temperature difference between the room temperature when the tank is constructed and the low temperature when the low temperature liquid 7 is stored.

The outer tank 3 has a hollow spherical shell shape slightly larger than the inner tank 2, and is formed by welding a large number of steel plates, for example. The diameter of the outer tank 3 is larger than the diameter of the inner tank 2. The inner tank 2 is supported by the outer tank 3 by a rod or the like (not shown) that connects the outer wall of the inner tank 2 and the inner wall of the outer tank 3.

The granular heat insulating material 4 is packed in a space surrounded by the outer wall of the inner tank 2 and the outer tank 3 in a compressed state. The granular heat insulating material 4 is, for example, granular pearlite. However, as the granular heat insulating material 4, a known granular heat insulating material other than pearlite may be adopted.

The space filled with the granular heat insulating material 4 between the inner tank 2 and the outer tank 3 is forcibly evacuated by the vacuum pump 6 to be in a substantially vacuum state. In this way, the space filled with the granular heat insulating material 4 is brought into a substantially vacuum state, whereby the heat insulating effect is further enhanced.

The vertical line passing through the center 3c of the outer tank 3 and the vertical line passing through the center 2c of the inner tank 2 coincide with the tank center line C of the double shell tank 1A. At the bottom of the tank, the gap between the inner wall of the outer tub 3 and the outer wall of the inner tub 2 on the tank centerline C is referred to as “bottom gap G1”. In addition, a gap between the inner wall of the outer tub 3 and the outer wall of the inner tub 2 on the tank centerline C at the tank top is referred to as a “top gap G2”.

In the double shell tank 1A according to the present embodiment, the inner tank 2 and the outer tank 3 are arranged so that the top clearance G2 is larger than the bottom clearance G1. That is, the inner tank 2 and the outer tank 3 are arranged so that the center 3c of the outer tank 3 is located above the center 2c of the inner tank 2. The center 3c of the outer tank 3 is the spherical shell-shaped center of the outer tank 3, and the center 2c of the inner tank 2 is the spherical shell-shaped center of the inner tank 2.

The size L2 of the top gap G2 is the size L1 of the bottom gap G1 when the inner tank 2 is empty (FIG. 1) and when the inner tank 2 contains the low temperature liquid 7 (FIG. 2). It is equal to or more than the value obtained by adding the level difference ΔL of the heat insulating material 4. That is, the following expression 1 is established.
L2>L1+ΔL (Equation 1)
The level difference ΔL (that is, the settling amount of the granular heat insulating material 4) can be obtained by calculation or simulation.

As described above, the double-shell tank 1A according to the present embodiment includes the inner tank 2 having a spherical shell shape in which the storage portion 21 that stores the low-temperature liquid 7 in a sealed state is formed, and the inner tank 2. An outer tank 3 that covers and a granular heat insulating material 4 that forms a heat insulating layer by filling a space surrounded by the outer wall of the inner tank 2 and the inner wall of the outer tank 3 are provided. The size L2 of the top clearance G2 between the inner tank 2 and the outer tank 3 is equal to the size L1 of the bottom clearance G1 between the inner tank 2 and the outer tank 3, and the inner tank 2 is empty and the inner tank 2 is It is equal to or more than a value obtained by adding the level difference ΔL between the granular heat insulating material 4 and the state in which the low temperature liquid 7 is contained.

In the double shell tank 1A, since the size L2 of the top gap G2 is larger than the size L1 of the bottom gap G1, a heat insulating layer thicker than the tank bottom is formed on the tank top when the inner tank 2 is empty. (See FIG. 1). Then, when the low temperature liquid 7 is supplied to the inner tank 2 and the inner tank 2 contracts, the gap between the inner tank 2 and the outer tank 3 widens, and the granular particles filled between the inner tank 2 and the outer tank 3 are filled. Although the heat insulating material 4 is settled, even when the granular heat insulating material 4 is settled, a heat insulating layer having a sufficient thickness L2′ is retained on the top of the tank (see FIG. 2).

As described above, according to the double-shell tank 1A according to the present embodiment, the granular heat insulating material 4 forms the heat insulating layer between the inner tank 2 and the outer tank 3 and the shrinkage deformation of the inner tank 2 causes Thus, even after the granular heat insulating material 4 has settled, it is possible to maintain the heat insulating layer having an appropriate thickness L2' at the tank top.

In the double-shell tank 1A according to the present embodiment, the outer tank 3 has a spherical shell shape, and the center 3c of the outer tank 3 is located above the center 2c of the inner tank 2.

In this way, by eccentricizing the center 2c of the inner tank 2 downward with respect to the center 3c of the outer tank 3, both the outer tank 3 and the inner tank 2 have a spherical shell shape with excellent strength, The size L2 of the top gap G2 from the outer tub 3 can be made larger than the size L1 of the bottom gap G1 between the inner tub 2 and the outer tub 3.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 3 is a sectional view showing the overall configuration of an empty double shell tank 1B according to the second embodiment of the present invention. FIG. 4 is a cross-sectional view of the double shell tank 1B showing a state where the low temperature liquid 7 is supplied to the inner tank 2 shown in FIG. In the description of the present embodiment, the same or similar members as those in the first embodiment described above will be denoted by the same reference numerals in the drawings, and detailed description thereof will be omitted.

As shown in FIGS. 3 and 4, the double-shell tank 1B according to the present embodiment has a spherical shell-shaped inner tank 2 in which a storage portion 21 for storing the low temperature liquid 7 in a sealed state is formed, An outer tank 3 that covers the inner tank 2 and a granular heat insulating material 4 that fills a space surrounded by the outer wall of the inner tank 2 and the inner wall of the outer tank 3 to form a heat insulating layer are provided.

The outer tub 3 includes a lower hemisphere shell portion 31, an upper hemisphere shell portion 32, and a tubular body portion 33 that connects the lower hemisphere shell portion 31 and the upper hemisphere shell portion 32 in the vertical direction. The lower hemispherical shell portion 31, the upper hemispherical shell portion 32, and the body portion 33 have the same diameter, and their values are larger than the diameter of the inner tank 2.

The inner tank 2 and the outer tank 3 are arranged so that the center 2c of the inner tank 2 and the center 31c of the lower hemispherical shell portion 31 coincide with each other. The inner tank 2 is supported by the outer tank 3 by a rod or the like (not shown) that connects the outer wall of the inner tank 2 and the inner wall of the outer tank 3.

As described above, in the double shell tank 1B according to the present embodiment, the outer tank 3 connects the lower hemisphere shell portion 31, the upper hemisphere shell portion 32, and the lower hemisphere shell portion 31 and the upper hemisphere shell portion 32. It is composed of a tubular body portion 33, and the center 2c of the inner tank 2 and the center 31c of the lower hemispherical shell portion 31 coincide with each other.

In the double shell tank 1B, a heat insulating layer having a constant thickness is formed around the inner tank 2 below the equator, and above the equator of the inner tank 2 around the inner tank 2 below the equator. A heat insulating layer thicker than the heat insulating layer is formed. In this way, the size L2 of the top gap G2 between the inner tank 2 and the outer tank 3 becomes equal to the size L1 of the bottom gap G1 between the inner tank 2 and the outer tank 3, and the inner tank 2 is empty. The double shell tank 1B having a value equal to or more than the value obtained by adding the level difference ΔL of the granular heat insulating material 4 to the state in which the tank 2 contains the low temperature liquid 7 is realized by a simple structure. Moreover, although the inner tank 2 has a spherical shell shape and the outer tank 3 is not a spherical shell, it can have a shape close to a spherical shell, and the outer tank 3 can have sufficient strength.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 5: is sectional drawing which shows the whole structure of the empty double shell tank 1C which concerns on 3rd Embodiment of this invention. FIG. 6 is a cross-sectional view of the double shell tank 1C showing a state where the low temperature liquid 7 is supplied to the inner tank 2 shown in FIG. In the description of the present embodiment, the same or similar members as those in the first embodiment described above will be denoted by the same reference numerals in the drawings, and detailed description thereof will be omitted.

As shown in FIGS. 5 and 6, the double-shell tank 1C according to the present embodiment has a spherical shell-shaped inner tank 2 in which a storage section 21 for storing the low-temperature liquid 7 in a sealed state is formed, An outer tank 3 that covers the inner tank 2 and a granular heat insulating material 4 that fills a space surrounded by the outer wall of the inner tank 2 and the inner wall of the outer tank 3 to form a heat insulating layer are provided.

The outer tub 3 includes a main body portion 35 having a spherical shell shape and a dome portion 36 provided on the top of the main body portion 35. The shape of the dome portion 36 is not particularly limited, but may be, for example, a shape in which the pod is turned upside down. Assuming that the dome portion 36 does not exist, the volume of the void generated at the top of the main body portion 35 is set to ΔV as the granular heat insulating material 4 of the main body portion 35 sinks as the inner tank 2 contracts and deforms. The volume of the dome portion 36 is larger than ΔV. That is, the dome portion 36 is filled with the granular heat insulating material 4 having a volume larger than ΔV.

The inner tub 2 and the outer tub 3 are arranged so that the center 2c of the inner tub 2 and the center 35c of the main body portion 35 coincide with each other. The inner tank 2 is supported by the outer tank 3 by a rod or the like (not shown) that connects the outer wall of the inner tank 2 and the inner wall of the outer tank 3.

As described above, in the double-shell tank 1C according to the present embodiment, the outer tank 3 includes the main body portion 35 having a spherical shell shape, and the dome portion 36 provided on the top portion of the main body portion 35. The center 2c of the tank 2 and the center 35c of the main body portion 35 coincide with each other.

In the double shell tank 1C, the dome portion 36 filled with the granular heat insulating material 4 is provided on the top of the main body 3 of the outer tub 3. In this way, the size L2 of the top gap G2 between the inner tank 2 and the outer tank 3 becomes equal to the size L1 of the bottom gap G1 between the inner tank 2 and the outer tank 3, and the inner tank 2 is empty. The double shell tank 1B having a value equal to or more than the value obtained by adding the level difference ΔL of the granular heat insulating material 4 to the state in which the tank 2 contains the low temperature liquid 7 is realized by a simple structure.

In the double shell tank 1C, even if the inner tub 2 contracts and deforms and the granular heat insulating material 4 filled between the inner tub 2 and the main body portion 35 of the outer tub 3 is settled, the settling Are supplemented by the granular heat insulating material 4 filled in the dome portion 36. Therefore, even when the granular heat insulating material 4 is settled, a heat insulating layer having a sufficient thickness L2' is retained at the top of the tank.

Although the preferred embodiment of the present invention has been described above, the present invention may be modified in the details of the specific structure and/or function of the above embodiment without departing from the spirit of the present invention. ..

1A, 1B, 1C: Double shell tank 2: Inner tank 2c: Inner tank center 3: Outer tank 3c: Outer tank center 4: Granular heat insulating material 6: Vacuum pump 7: Low temperature liquid 21: Storage part 31: Bottom Hemispherical shell part 31c: Lower hemispherical shell part center 32: Upper hemispherical shell part 33: Body part 35: Main body part 35c: Main body part center 36: Dome part C: Tank center line G1: Bottom clearance G2: Top clearance ΔL: Level difference

Claims (4)

A spherical shell-shaped inner tank in which a storage unit for storing liquid in a sealed state is formed,
An outer tank covering the inner tank,
A granular heat insulating material filled in a space surrounded by the outer wall of the inner tank and the inner wall of the outer tank to form a heat insulating layer,
The size of the top clearance between the inner tank and the outer tank is the size of the bottom clearance between the inner tank and the outer tank, and the inner tank is empty and the inner tank contains the liquid. And a value equal to or greater than the level difference of the granular heat insulating material,
Double shell tank. The outer tank has a spherical shell shape, and the center of the outer tank is located above the center of the inner tank.
The double shell tank according to claim 1. The outer tank is composed of a lower hemispherical shell portion, an upper hemispherical shell portion, and a cylindrical body connecting the lower hemispherical shell portion and the upper hemispherical shell portion, and the center of the inner tank and the lower hemispherical shell portion. Coincides with the center of
The double shell tank according to claim 1. The outer tank comprises a main body having a spherical shell shape and a dome portion provided on the top of the main body and filled with the granular heat insulating material, and the center of the inner tank and the center of the main body coincide with each other. ,
The double shell tank according to claim 1.

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