EP4174360A1

EP4174360A1 - Double-shell tank

Info

Publication number: EP4174360A1
Application number: EP20941713.8A
Authority: EP
Inventors: Takahiro Yamaguchi; Satoshi HORINO; Akira Yamaguchi; Tomomi KUMANO
Original assignee: Kawasaki Heavy Industries Ltd; Kawasaki Jukogyo KK
Current assignee: Kawasaki Heavy Industries Ltd; Kawasaki Motors Ltd
Priority date: 2020-06-26
Filing date: 2020-06-26
Publication date: 2023-05-03
Also published as: CN115720615A; KR20230024370A; EP4174360A4; WO2021260946A1

Abstract

A double-shell tank includes: an inner shell having a spherical shell shape and including therein a storing portion that stores a liquid in a sealed state; an outer shell that covers the inner shell; and powdered thermal insulation that is filled in a space surrounded by an outer wall of the inner shell and an inner wall of the outer shell to become a heat insulating layer. A size of a top portion gap between the inner shell and the outer shell is equal to or more than a value obtained by adding a level difference to a size of a bottom portion gap between the inner shell and the outer shell, the level difference being a level difference between the powdered thermal insulation when the inner shell is in an empty state and the powdered thermal insulation when the liquid is in the inner shell.

Description

Technical Field

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

Background Art

Double-shell tanks have been known as tanks that store low temperature liquids. Generally, the double-shell tank includes: an inner shell that practically stores a low temperature liquid; an outer shell that covers the inner shell from an outside and is located away from the inner shell by a predetermined distance; and a heat insulating layer between the inner shell and the outer shell. For example, the heat insulating layer is made of powdered thermal insulation filled in between the inner shell and the outer shell. Pearlite is used as the powdered thermal insulation.
When constructing the double-shell tank, the inner shell and the outer shell are completed, and then, the powdered thermal insulation is filled in between the inner shell in an empty state and the outer shell. Therefore, when the low temperature liquid is supplied to the inner shell, and this causes thermal contraction of the inner shell, the gap between the inner shell and the outer shell may increase, and the powdered thermal insulation filled in between the inner shell and the outer shell may move downward. When the powdered thermal insulation moves downward, a space in which the powdered thermal insulation does not exist is generated at a tank top portion of the double-shell tank, and the thickness of the heat insulating layer at the tank top portion decreases. When a portion where the thickness of the heat insulating layer is inadequate is generated in the double-shell tank, the heat insulating property of this portion deteriorates. By the deterioration of the heat insulating property, cold heat of the inner shell may be transferred to the outer shell, and this may generate frost on the outer shell. Thus, the corrosion of the outer shell may be caused. Moreover, when the amount of heat input to the inner shell increases by the deterioration of the heat insulating property, the amount of boil off gas of the low temperature liquid may increase, and the pressure of the inner shell may become excessive.
Therefore, the double-shell tank of PTL 1 includes the heat insulating layer including two layers, i.e., inner and outer layers that are an inside heat insulating layer made of a stretchable material (glass wool) that is stretchable in a radial direction of the inner shell and an outside heat insulating layer made of filler (pearlite). According to this double-shell tank, a space generated in the heat insulating layer by the thermal contraction of the inner shell is filled with the expanded stretchable material, and this suppresses the downward movement of the filler.

Citation List

Patent Literature

PTL 1: Japanese Laid-Open Patent Application Publication No. 2013-238285

Summary of Invention

Technical Problem

Especially in the case of the double-shell tank located outdoors, it is important to reduce the amount of heat input to the tank top portion by solar radiation. However, when the heat insulating layer between the inner shell and the outer shell is made of the powdered thermal insulation, the heat insulating property of the tank top portion deteriorates by the downward movement of the powdered thermal insulation as described above.
According to the double-shell tank of PTL 1, the downward movement of the powdered thermal insulation (filler) can be suppressed. However, since a large amount of glass wool that is more expensive than pearlite is used, the cost is high.
The present disclosure was made under these circumstances, and an object of the present disclosure is to provide a double-shell tank which realizes both forming a heat insulating layer between an inner shell and an outer shell by powdered thermal insulation and maintaining the heat insulating layer having an appropriate thickness at a tank top portion even after the powdered thermal insulation moves downward by contraction deformation of the inner shell.

Solution to Problem

A double-shell tank according to one aspect of the present disclosure includes: an inner shell having a spherical shell shape and including therein a storing portion that stores a liquid in a sealed state; an outer shell that covers the inner shell; and powdered thermal insulation that is filled in a space surrounded by an outer wall of the inner shell and an inner wall of the outer shell to become a heat insulating layer. A size of a top portion gap between the inner shell and the outer shell when the inner shell is in an empty state is equal to or more than a value obtained by adding a level difference to a size of a bottom portion gap between the inner shell and the outer shell, the level difference being a level difference between the powdered thermal insulation when the inner shell is in the empty state and the powdered thermal insulation when the liquid is in the inner shell.
According to the above double-shell tank, the size of the top portion gap is larger than the size of the bottom portion gap. Therefore, when the inner shell is in the empty state, the heat insulating layer that is thicker than the heat insulating layer at the tank bottom portion is located at the tank top portion. Then, when the low temperature liquid is supplied to the inner shell, and this contracts the inner shell, the gap between the inner shell and the outer shell increases, and the powdered thermal insulation filled in between the inner shell and the outer shell moves downward. However, even after the powdered thermal insulation moves downward, the heat insulating layer having an adequate thickness is maintained at the tank top portion. Therefore, the above double-shell tank can realize both forming the heat insulating layer between the inner shell and the outer shell by the powdered thermal insulation and maintaining the heat insulating layer having an appropriate thickness at the tank top portion even after the powdered thermal insulation moves downward by the contraction deformation of the inner shell.
In the above double-shell tank, the outer shell may have a spherical shell shape, and a center of the outer shell may be located higher than a center of the inner shell.
Since the center of the inner shell is located lower than the center of the outer shell as above, the size of the top portion gap between the inner shell and the outer shell can be made larger than the size of the bottom portion gap between the inner shell and the outer shell in a state where each of the outer shell and the inner shell has a spherical shell shape that excels in strength.
Or, in the above double-shell tank, the outer shell may include 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, and a center of the inner shell and a center of the lower hemispherical shell portion may coincide with each other.
With this, at a lower side of the equator of the inner shell, the heat insulating layer having a fixed thickness is located around the inner shell. Moreover, at an upper side of the equator of the inner shell, the heat insulating layer thicker than the heat insulating layer located at the lower side of the equator of the inner shell is located around the inner shell. Then, the outer shell has a shape similar to the spherical shell shape and can obtain adequate strength.
Or, in the above double-shell tank, the outer shell may include a main body portion having a spherical shell shape and a dome portion that is located at a top portion of the main body portion and is filled with the powdered thermal insulation, and a center of the inner shell and a center of the main body portion may coincide with each other.
As above, the dome portion filled with the powdered thermal insulation is located at the top portion of the main body portion of the outer shell. Therefore, even when the powdered thermal insulation filled in between the inner shell and the main body portion of the outer shell moves downward by the contraction deformation of the inner shell, the downward movement of the powdered thermal insulation 4 is compensated by the powdered thermal insulation filled in the dome portion. Therefore, even when the powdered thermal insulation moves downward, the heat insulating layer having an adequate thickness is maintained at the tank top portion.

Advantageous Effects of Invention

The present disclosure can provide the double-shell tank which realizes both forming the heat insulating layer between the inner shell and the outer shell by the powdered thermal insulation and maintaining the heat insulating layer having an appropriate thickness at the tank top portion even after the powdered thermal insulation moves downward by the contraction deformation of the inner shell.

Brief Description of Drawings

FIG. 1 is a sectional view showing the entire configuration of an empty double-shell tank according to Embodiment 1 of the present disclosure.
FIG. 2 is a sectional view showing the double-shell tank in which a low temperature liquid is in an inner shell shown in FIG. 1.
FIG. 3 is a sectional view showing the entire configuration of the empty double-shell tank according to Embodiment 2 of the present disclosure.
FIG. 4 is a sectional view showing the double-shell tank in which the low temperature liquid is in the inner shell shown in FIG. 3.
FIG. 5 is a sectional view showing the entire configuration of the empty double-shell tank according to Embodiment 3 of the present disclosure.
FIG. 6 is a sectional view showing the double-shell tank in which the low temperature liquid is in the inner shell shown in FIG. 5.

Description of Embodiments

Embodiment 1

Next, Embodiment 1 of the present disclosure will be described with reference to the drawings. FIG. 1 is a sectional view showing the entire configuration of an empty double-shell tank 1A according to Embodiment 1 of the present disclosure. FIG. 2 is a sectional view showing the double-shell tank 1A in which a low temperature liquid 7 is in an inner shell 2 shown in FIG. 1.
The double-shell tank 1A shown in FIGS. 1 and 2 is a tank that stores the low temperature liquid 7, such as liquid hydrogen, liquid nitrogen, or liquefied natural gas. The double-shell tank 1A is supported by a skirt or a post (not shown) and is located on a hull, the ground, or the like.
The double-shell tank 1A includes: the inner shell 2; an outer shell 3 that covers the inner shell 2; powdered thermal insulation 4 that is filled in between the inner shell 2 and the outer shell 3 to become a heat insulating layer; and a vacuum pump 6 that performs vacuum drawing with respect to a space between the inner shell 2 and the outer shell 3.
The inner shell 2 has a hollow spherical shell shape and includes, for example, a large number of SUS panels welded to each other. A storing portion 21 that stores the low temperature liquid 7 in a sealed state is inside the inner shell 2. The inner shell 2 allows contraction deformation and deformation recovery which are caused by a temperature difference between normal temperature at the time of tank construction and low temperature at the time when the low temperature liquid 7 is in the inner shell 2.
The outer shell 3 has a hollow spherical shell shape larger than the inner shell 2 by one size and includes, for example, a large number of steel plates welded to each other. The diameter of the outer shell 3 is larger than the diameter of the inner shell 2. The inner shell 2 is supported by the outer shell 3 through, for example, a rod (not shown) that connects an outer wall of the inner shell 2 and an inner wall of the outer shell 3.
The powdered thermal insulation 4 is filled in a pressure sealed state in the space surrounded by the outer wall of the inner shell 2 and the inner wall of the outer shell 3. The powdered thermal insulation 4 is, for example, granular pearlite. The powdered thermal insulation 4 may be a known powdered thermal insulation other than pearlite.
The space which is between the inner shell 2 and the outer shell 3 and is filled with the powdered thermal insulation 4 is subjected to forced air exhaustion by the vacuum pump 6, and therefore, is substantially in a vacuum state. Since the space filled with the powdered thermal insulation 4 is substantially in a vacuum state, the heat insulating effect can be further improved.
A vertical line passing through a center 3c of the outer shell 3 and a vertical line passing through a center 2c of the inner shell 2 coincide with a tank center line C of the double-shell tank 1A. A gap between the inner wall of the outer shell 3 and the outer wall of the inner shell 2 on the tank center line C at the tank bottom portion is referred to as a "bottom portion gap G1". Moreover, a gap between the inner wall of the outer shell 3 and the outer wall of the inner shell 2 on the tank center line C at the tank top portion is referred to as a "top portion gap G2".
In the double-shell tank 1A according to the present embodiment, the inner shell 2 and the outer shell 3 are located such that the top portion gap G2 is larger than the bottom portion gap G1. To be specific, the inner shell 2 and the outer shell 3 are located such that the center 3c of the outer shell 3 is located higher than the center 2c of the inner shell 2. The center 3c of the outer shell 3 is a center of the spherical shell shape of the outer shell 3, and the center 2c of the inner shell 2 is a center of the spherical shell shape of the inner shell 2.
Then, a size L2 of the top portion gap G2 when the inner shell 2 is in an empty state is equal to or more than a value obtained by adding a level difference ΔL to a size L1 of the bottom portion gap G1, the level difference ΔL being a level difference between the powdered thermal insulation 4 when the inner shell 2 is in the empty state (FIG. 1) and the powdered thermal insulation 4 when the low temperature liquid 7 is in the inner shell 2 (FIG. 2). To be specific, Formula 1 below is satisfied. The above expression "when the low temperature liquid 7 is in the inner shell 2" may be a state where the low temperature liquid 7 is in the storing portion 21 to a predetermined full liquid level (or, any reference liquid level). $L 2 > L 1 + Δ L$
The level difference ΔL (i.e., the amount of downward movement of the powdered thermal insulation 4) can be obtained by calculation or simulation.
As described above, the double-shell tank 1A according to the present embodiment includes: the inner shell 2 having a spherical shell shape and including therein the storing portion 21 that stores the low temperature liquid 7 in a sealed state; the outer shell 3 that covers the inner shell 2; and the powdered thermal insulation 4 that is filled in the space surrounded by the outer wall of the inner shell 2 and the inner wall of the outer shell 3 to become the heat insulating layer. Then, the size L2 of the top portion gap G2 between the inner shell 2 and the outer shell 3 is equal to or more than a value obtained by adding the level difference ΔL to the size L1 of the bottom portion gap G1 between the inner shell 2 and the outer shell 3, the level difference ΔL being a level difference between the powdered thermal insulation 4 when the inner shell 2 is in the empty state and the powdered thermal insulation 4 when the low temperature liquid 7 is in the inner shell 2.
In the double-shell tank 1A, the size L2 of the top portion gap G2 is larger than the size L1 of the bottom portion gap G1. Therefore, when the inner shell 2 is in the empty state, the heat insulating layer that is thicker than the heat insulating layer at the tank bottom portion is located at the tank top portion (see FIG. 1). Then, when the low temperature liquid 7 is supplied to the inner shell 2, and this contracts the inner shell 2, the gap between the inner shell 2 and the outer shell 3 increases, and the powdered thermal insulation 4 filled in between the inner shell 2 and the outer shell 3 moves downward. However, even after the powdered thermal insulation 4 moves downward, the heat insulating layer having an adequate thickness L2' is maintained at the tank top portion (see FIG. 2).
As above, the double-shell tank 1A according to the present embodiment can realize both forming the heat insulating layer between the inner shell 2 and the outer shell 3 by the powdered thermal insulation 4 and maintaining the heat insulating layer having the appropriate thickness L2' at the tank top portion even after the powdered thermal insulation 4 moves downward by the contraction deformation of the inner shell 2.
Moreover, in the double-shell tank 1A according to the present embodiment, the outer shell 3 has a spherical shell shape, and the center 3c of the outer shell 3 is located higher than the center 2c of the inner shell 2.
Since the center 2c of the inner shell 2 is located lower than the center 3c of the outer shell 3 as above, the size L2 of the top portion gap G2 between the inner shell 2 and the outer shell 3 can be made larger than the size L1 of the bottom portion gap G1 between the inner shell 2 and the outer shell 3 in a state where each of the outer shell 3 and the inner shell 2 has a spherical shell shape that excels in strength.

Embodiment 2

Next, Embodiment 2 of the present disclosure will be described. FIG. 3 is a sectional view showing the entire configuration of an empty double-shell tank 1B according to Embodiment 2 of the present disclosure. FIG. 4 is a sectional view showing the double-shell tank 1B in which the low temperature liquid 7 is in the inner shell 2 shown in FIG. 3. In the description of the present embodiment, the same reference signs are used for the same or similar components as or to those in Embodiment 1, and the repetition of the same explanation is avoided.
As shown in FIGS. 3 and 4, the double-shell tank 1B according to the present embodiment includes: the inner shell 2 having a spherical shell shape and including therein the storing portion 21 that stores the low temperature liquid 7 in a sealed state; the outer shell 3 that covers the inner shell 2; and the powdered thermal insulation 4 that is filled in the space surrounded by the outer wall of the inner shell 2 and the inner wall of the outer shell 3 to become the heat insulating layer.
The outer shell 3 includes: a lower hemispherical shell portion 31; an upper hemispherical shell portion 32; and a tubular body portion 33 that connects the lower hemispherical shell portion 31 and the upper hemispherical shell portion 32 in an upper-lower direction. The diameter of the lower hemispherical shell portion 31, the diameter of the upper hemispherical shell portion 32, and the diameter of the body portion 33 are equal to each other, and this diameter is larger than the diameter of the inner shell 2.
The inner shell 2 and the outer shell 3 are located such that the center 2c of the inner shell 2 and a center 31c of the lower hemispherical shell portion 31 coincide with each other. The inner shell 2 is supported by the outer shell 3 through, for example, a rod (not shown) that connects the outer wall of the inner shell 2 and the inner wall of the outer shell 3.
As described above, in the double-shell tank 1B according to the present embodiment, the outer shell 3 includes the lower hemispherical shell portion 31, the upper hemispherical shell portion 32, and the tubular body portion 33 connecting the lower hemispherical shell portion 31 and the upper hemispherical shell portion 32, and the center 2c of the inner shell 2 and the center 31c of the lower hemispherical shell portion 31 coincide with each other.
In the double-shell tank 1B, at a lower side of the equator of the inner shell 2, the heat insulating layer having a fixed thickness is located around the inner shell 2. Moreover, at an upper side of the equator of the inner shell 2, the heat insulating layer thicker than the heat insulating layer located at the lower side of the equator of the inner shell 2 is located around the inner shell 2. As above, the double-shell tank 1B is realized by a simple structure such that the size L2 of the top portion gap G2 between the inner shell 2 and the outer shell 3 is equal to or more than a value obtained by adding the level difference ΔL to the size L1 of the bottom portion gap G1 between the inner shell 2 and the outer shell 3, the level difference ΔL being a level difference between the powdered thermal insulation 4 when the inner shell 2 is in the empty state and the powdered thermal insulation 4 when the low temperature liquid 7 is in the inner shell 2. In addition, the inner shell 2 has a spherical shell shape, and the outer shell 3 does not have a spherical shell shape but has a shape similar to the spherical shell shape. The outer shell 3 can obtain adequate strength.

Embodiment 3

Next, Embodiment 3 of the present disclosure will be described. FIG. 5 is a sectional view showing the entire configuration of an empty double-shell tank 1C according to Embodiment 3 of the present disclosure. FIG. 6 is a sectional view showing the double-shell tank 1C in which the low temperature liquid 7 is in the inner shell 2 shown in FIG. 5. In the description of the present embodiment, the same reference signs are used for the same or similar components as or to those in Embodiment 1, and the repetition of the same explanation is avoided.
As shown in FIGS. 5 and 6, the double-shell tank 1C according to the present embodiment includes: the inner shell 2 having a spherical shell shape and including therein the storing portion 21 that stores the low temperature liquid 7 in a sealed state; the outer shell 3 that covers the inner shell 2; and the powdered thermal insulation 4 that is filled in the space surrounded by the outer wall of the inner shell 2 and the inner wall of the outer shell 3 to become the heat insulating layer.
The outer shell 3 includes: a main body portion 35 having a spherical shell shape; and a dome portion 36 located at a top portion of the main body portion 35. The shape of the dome portion 36 is not especially limited, and for example, may have a shape obtained by vertically inverting a pot. When it is assumed that there is no dome portion 36, the volume of a void generated at the top portion of the main body portion 35 by the downward movement of the powdered thermal insulation 4 of the main body portion 35 due to the contraction deformation of the inner shell 2 is represented by ΔV. The capacity of the dome portion 36 is larger than ΔV. To be specific, the powdered thermal insulation 4 having the volume larger than ΔV is filled in the dome portion 36.
The inner shell 2 and the outer shell 3 are located such that the center 2c of the inner shell 2 and a center 35c of the main body portion 35 coincide with each other. The inner shell 2 is supported by the outer shell 3 through, for example, a rod (not shown) that connects the outer wall of the inner shell 2 and the inner wall of the outer shell 3.
As described above, in the double-shell tank 1C according to the present embodiment, the outer shell 3 includes: the main body portion 35 having a spherical shell shape; and the dome portion 36 located at the top portion of the main body portion 35, and the center 2c of the inner shell 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 in which the powdered thermal insulation 4 is filled is located at the top portion of the main body portion of the outer shell 3. As above, the double-shell tank 1B is realized by a simple structure such that the size L2 of the top portion gap G2 between the inner shell 2 and the outer shell 3 is equal to or more than a value obtained by adding the level difference ΔL to the size L1 of the bottom portion gap G1 between the inner shell 2 and the outer shell 3, the level difference ΔL being a level difference between the powdered thermal insulation 4 when the inner shell 2 is in the empty state and the powdered thermal insulation 4 when the low temperature liquid 7 is in the inner shell 2.
Then, according to the double-shell tank 1C, even when the powdered thermal insulation 4 filled in between the inner shell 2 and the main body portion 35 of the outer shell 3 moves downward by the contraction deformation of the inner shell 2, the downward movement of the powdered thermal insulation 4 is compensated by the powdered thermal insulation 4 filled in the dome portion 36. Therefore, even when the powdered thermal insulation 4 moves downward, the heat insulating layer having an adequate thickness L2' is maintained at the tank top portion.
The foregoing has described preferred embodiments of the present disclosure. Modifications of specific structures and/or functional details of the above embodiments may be included in the present disclosure as long as they are within the scope of the present disclosure.

Reference Signs List

1A, 1B, 1C: double-shell tank
2: inner shell
2c: center of inner shell
3: outer shell
3c: center of outer shell
4: powdered thermal insulation
6: vacuum pump
7: low temperature liquid
21: storing portion
31: lower hemispherical shell portion
31c: center of lower hemispherical shell portion
32: upper hemispherical shell portion
33: body portion
35: main body portion
35c: center of main body portion
36: dome portion
C: tank center line
G1: bottom portion gap
G2: top portion gap
ΔL: level difference

Claims

A double-shell tank comprising:
an inner shell having a spherical shell shape and including therein a storing portion that stores a liquid in a sealed state;

an outer shell that covers the inner shell; and

powdered thermal insulation that is filled in a space surrounded by an outer wall of the inner shell and an inner wall of the outer shell to become a heat insulating layer, wherein

a size of a top portion gap between the inner shell and the outer shell when the inner shell is in an empty state is equal to or more than a value obtained by adding a level difference to a size of a bottom portion gap between the inner shell and the outer shell, the level difference being a level difference between the powdered thermal insulation when the inner shell is in the empty state and the powdered thermal insulation when the liquid is in the inner shell.
The double-shell tank according to claim 1, wherein:
the outer shell has a spherical shell shape; and

a center of the outer shell is located higher than a center of the inner shell.
The double-shell tank according to claim 1, wherein:
the outer shell 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; and

a center of the inner shell and a center of the lower hemispherical shell portion coincide with each other.
The double-shell tank according to claim 1, wherein:
the outer shell includes
a main body portion having a spherical shell shape and

a dome portion that is located at a top portion of the main body portion and is filled with the powdered thermal insulation; and

a center of the inner shell and a center of the main body portion coincide with each other.