LIQUEFIED GAS TANK

Abstract

 A liquefied gas tank includes: a tank body that stores liquefied gas; a protruding part protruding upward from the tank body, the protruding part being a hollow part whose interior communicates with an interior of the tank body; a first thermal insulation layer that encompasses the tank body; a cylindrical second thermal insulation layer that encompasses the protruding part except a distal end portion of the protruding part; and a plurality of discs disposed in a region in the interior of the protruding part, the region overlapping the second thermal insulation layer, the discs partitioning off the interior of the protruding part into a plurality of cells that are arranged in a protruding direction of the protruding part.

Description

Technical Field

[0001] The present invention relates to a liquefied gas tank.

Background Art

[0002] Conventionally, there is a known liquefied gas tank for low-temperature liquefied gas. For example, Patent Literature 1 discloses a liquefied gas tank 100 as shown in FIG. 3.

[0003] The liquefied gas tank 100 includes a tank body 110 and a protruding part 120. The tank body 110 stores liquefied gas, and the protruding part 120 protrudes upward from the tank body 110. The protruding part 120 is a hollow part, and the interior of the protruding part 120 communicates with the interior of the tank body 110. The tank body 110 is encompassed by a first thermal insulation layer 130. The protruding part 120 is, except its distal end portion, encompassed by a cylindrical second thermal insulation layer 140.

[0004] A thermal insulation member 150 is disposed in a region in the interior of the protruding part 120, the region overlapping the second thermal insulation layer 140. The thermal insulation member 150 is a metal disc-shaped box filled with a foamed material.

Citation List

Patent Literature

[0005] PTL 1: Japanese Laid-Open Utility Model Application Publication No. S55-89898

Summary of Invention

Technical Problem

[0006] Although the protruding part 120 of the liquefied gas tank 100 disclosed in Patent Literature 1 has sufficient thermal insulation performance, there is a demand for further improving the thermal insulation performance of the protruding part 120.

[0007] In view of the above, an object of the present invention is to provide a liquefied gas tank that makes it possible to improve the thermal insulation performance of the protruding part as compared to the conventional art.

Solution to Problem

[0008] In order to solve the above-described problems, the inventors of the present invention have paid attention to the fact that, in the protruding part, vaporized gas resulting from vaporization of the liquefied gas flows convectively. Then, the inventors of the present invention have found that, by suppressing this convective flow, the thermal insulation performance of the protruding part can be improved. The present invention has been made from such a technological point of view.

[0009] Specifically, a liquefied gas tank according to the present invention includes: a tank body that stores liquefied gas; a protruding part protruding upward from the tank body, the protruding part being a hollow part whose interior communicates with an interior of the tank body; a first thermal insulation layer that encompasses the tank body; a cylindrical second thermal insulation layer that encompasses the protruding part except a distal end portion of the protruding part; and a plurality of discs disposed in a region in the interior of the protruding part, the region overlapping the second thermal insulation layer, the discs partitioning off the interior of the protruding part into a plurality of cells that are arranged in a protruding direction of the protruding part.

[0010] According to the above configuration, only a small convective flow is generated in each cell in the protruding part. Consequently, the entry of outside heat into the interior of the tank body in a manner to penetrate all the discs can be suppressed. This makes it possible to improve the thermal insulation performance of the protruding part.

[0011] The distal end portion of the protruding part may be provided with a manhole. Each of the plurality of discs may be provided with a manhole and mounted with a manhole cover by which the manhole is opened and closed. This configuration allows a worker to access and inspect the interior of the tank body through the interior of the protruding part.

[0012] Among the plurality of discs, except the disc located at an uppermost position, each disc may be mounted with the manhole cover such that the manhole cover is slidable along the disc. According to this configuration, the discs can be disposed at a small pitch.

[0013] For example, the protruding part may include: a peripheral wall that rises from the tank body; and a ceiling wall that seals an upper opening of the peripheral wall. The plurality of discs may be mounted to an inner circumferential surface of the peripheral wall.

[0014] Each of the plurality of discs may be a metal plate. Alternatively, each of the discs may be a metal disc-shaped box filled with a foamed material. However, if each of the discs is a metal plate, the cost can be lowered.

[0015] The first thermal insulation layer may include: an outer shell that surrounds the tank body while being spaced apart from the tank body; and a first vacuum space formed between the outer shell and the tank body. The second thermal insulation layer may include: an outer cylinder that rises from the outer shell and surrounds the protruding part except a distal end portion of the protruding part; a ring plate that couples an upper end of the outer cylinder and the protruding part; and a second vacuum space formed between the outer cylinder and the protruding part. According to this configuration, the tank body and the first thermal insulation layer constitute a vacuum double-shell structure, and also, the protruding part and the second thermal insulation layer constitute a vacuum double-shell structure. This makes it possible to further suppress the entry of outside heat into the interior of the tank body.

Advantageous Effects of Invention

[0016] The present invention makes it possible to improve the thermal insulation performance of the protruding part of the liquefied gas tank as compared to the conventional art.

Brief Description of Drawings

[0017] 

FIG. 1 is a longitudinal sectional view of a part of a liquefied gas tank according to one embodiment of the present invention.

FIG. 2 is a transverse sectional view taken along line II-II of FIG. 1.

FIG. 3 is a longitudinal sectional view of a part of a conventional liquefied gas tank.

Description of Embodiments

[0018] FIG. 1 and FIG. 2 show a liquefied gas tank 1 according to one embodiment of the present invention. The liquefied gas tank 1 includes a tank body 2 and a protruding part 3. The tank body 2 stores liquefied gas, and the protruding part 3 protrudes upward from the tank body 2. The liquefied gas tank 1 may be installed in a ship such as a liquefied gas carrier, or may be installed on the ground.

[0019] For example, the liquefied gas is liquefied petroleum gas (LPG, about -45°C), liquefied ethylene gas (LEG, about -100°C), liquefied natural gas (LNG, about -160°C), liquefied hydrogen (LH₂, about -250°C), or liquefied helium (LHe, about -270°C).

[0020] The shape of the tank body 2 is not particularly limited. The tank body 2 may have a spherical shape, a horizontally-long cylindrical shape, or a vertically-long cylindrical shape. Alternatively, the tank body 2 may have a cubic or rectangular parallelepiped shape.

[0021] In the present embodiment, the protruding direction of the protruding part 3 is parallel to the vertical direction. Alternatively, the protruding direction of the protruding part 3 may be slightly inclined relative to the vertical direction. In the present embodiment, the protruding part 3 is a dome that is penetrated by a plurality of (in the illustrated example, two) pipes 7. One of the pipes 7 is a pipe for leading, to the outside, the liquefied gas that is pumped up by a pump disposed in the tank body 2.

[0022] The protruding part 3 is a hollow part, and the interior of the protruding part 3 communicates with the interior of the tank body 2. To be more specific, the protruding part 3 includes a peripheral wall 31 and a ceiling wall 32. The peripheral wall 31 rises from the tank body 2, and the ceiling wall 32 seals the upper opening of the peripheral wall 31. The aforementioned pipes 7 extend in the vertical direction, and penetrate the ceiling wall 32. The upper end portion of the peripheral wall 31 and the ceiling wall 32 constitute the distal end portion of the protruding part 3.

[0023] In the present embodiment, the ceiling wall 32 (the distal end portion) of the protruding part 3 is provided with a manhole 33. The manhole 33 is formed by a manhole cylinder 34 joined to the ceiling wall 32, and is opened and closed by a manhole cover 35. When closing the manhole 33, the manhole cover 35 is fixed by bolts or the like to a flange provided on the upper end of the manhole cylinder 34. When opening the manhole 33, the manhole cover 35 is removed from the manhole cylinder 34. It should be noted that, in addition to the manhole 33, the distal end portion of the protruding part 3 may be further provided with an opening through which equipment such as a pump is carried into or out of the interior of the tank body 2, the opening being opened and closed by a door or cover.

[0024] The tank body 2 is encompassed by a first thermal insulation layer 4. The protruding part 3 is, except its distal end portion, encompassed by a cylindrical second thermal insulation layer 5. In the present embodiment, each of the first thermal insulation layer 4 and the second thermal insulation layer 5 includes a vacuum space. It should be noted that each of the first thermal insulation layer 4 and the second thermal insulation layer 5 may be constituted by a plurality of thermal insulators (e.g., vacuum insulation panels) arranged on the surface of the tank body 2 or the surface of the protruding part 3. Alternatively, each of the first thermal insulation layer 4 and the second thermal insulation layer 5 may simply be a foamed body. In this case, each of the first thermal insulation layer 4 and the second thermal insulation layer 5 may be constituted by a plurality of foamed panels.

[0025] Specifically, the first thermal insulation layer 4 includes an outer shell 41 and a first vacuum space 42. The outer shell 41 surrounds the tank body 2 while being spaced apart from the tank body 2. The first vacuum space 42 is formed between the outer shell 41 and the tank body 2. The second thermal insulation layer 5 includes an outer cylinder 51, a ring plate 52, and a second vacuum space 53. The outer cylinder 51 rises from the outer shell 41, and surrounds the protruding part 3 except the distal end portion of the protruding part 3. The ring plate 52 couples the upper end of the outer cylinder 51 and the protruding part 3, and is flat in a direction (in the present embodiment, the horizontal direction) orthogonal to the protruding direction of the protruding part 3. The second vacuum space 53 is formed between the outer cylinder 51 and the protruding part 3. The second vacuum space 53 communicates with the first vacuum space 42.

[0026] In a region in the interior of the protruding part 3, the region overlapping the second thermal insulation layer 5, i.e., the region being positioned below the upper end of the second thermal insulation layer 5, three discs 6A to 6C are disposed such that they are arranged in the protruding direction of the protruding part 3. It should be noted that the number of discs is not particularly limited, so long as the number of discs is plural. The discs 6A to 6C are penetrated by the aforementioned pipes 7.

[0027] Each of the discs 6A to 6C is flat in the direction orthogonal to the protruding direction of the protruding part 3, and is mounted to the inner circumferential surface of the peripheral wall 31 of the protruding part 3. The interior of the protruding part 3 is partitioned off by these discs 6A to 6C into a plurality of cells 30, which are arranged in the protruding direction of the protruding part 3.

[0028] Various mounting methods are adoptable for mounting each disc to the inner circumferential surface of the peripheral wall 31. For example, each disc may be directly mounted to the inner circumferential surface of the peripheral wall 31, or may be indirectly mounted to the inner circumferential surface of the peripheral wall 31 via, for example, a member that has an L-shaped cross section (not shown).

[0029] In the present embodiment, each of the discs 6A to 6C is a metal plate. Alternatively, each of the discs 6A to 6C may be a metal disc-shaped box filled with a foamed material. However, if each of the discs 6Ato 6C is a metal plate, the cost can be lowered.

[0030] Each of the discs 6A to 6C is provided with a manhole 61 at a position corresponding to the above-described manhole 33. Also, each of the discs 6A to 6C is mounted with a manhole cover 62, by which the manhole 61 is opened and closed.

[0031] To be more specific, the disc 6A, which is located at the uppermost position among the discs 6A to 6C, is mounted with the manhole cover 62 such that the manhole cover 62 is swingable via an unshown hinge. The other discs 6B and 6C are each mounted with the manhole cover 62 such that the manhole cover 62 is slidable via an unshown slide mechanism.

[0032] Since the liquefied gas tank 1 according to the present embodiment is configured as above, only a small convective flow is generated in each cell 30 in the protruding part 3. Consequently, the entry of outside heat into the interior of the tank body 2 in a manner to penetrate all the discs 6A to 6C can be suppressed. This makes it possible to improve the thermal insulation performance of the protruding part 3. It should be noted that this advantageous effect can be obtained regardless of the configuration of the discs 6A to 6C (e.g., regardless of whether the discs 6A to 6C are metal plates or metal disc-shaped boxes filled with a foamed material).

[0033] Further, in the present embodiment, since the distal end portion of the protruding part 3 and the discs 6A to 6C are provided with the manhole 33 and the manholes 61, a worker can access and inspect the interior of the tank body 2 through the interior of the protruding part 3.

[0034] Still further, in the present embodiment, the manhole cover 62 mounted to the uppermost disc 6A can be readily operated by swinging the manhole cover 62. Also, since the manhole covers 62 mounted to the other respective discs 6B and 6C are slidable, the discs 6A to 6C can be disposed at a small pitch. Alternatively, the discs 6Ato 6C may be disposed at a large pitch, and the manhole covers 62 mounted to the respective discs 6B and 6C may be configured as swingable manhole covers. Further alternatively, all the manhole covers 62 mounted to the respective discs 6A to 6C may be configured as slidable manhole covers.

[0035] Still further, in the present embodiment, the tank body 2 and the first thermal insulation layer 4 constitute a vacuum double-shell structure, and also, the protruding part 3 and the second thermal insulation layer 5 constitute a vacuum double-shell structure. This makes it possible to further suppress the entry of outside heat into the interior of the tank body 2.

(Variations)

[0036] The present invention is not limited to the above-described embodiment. Various modifications can be made without departing from the scope of the present invention.

[0037] For example, the protruding part 3 need not be a dome penetrated by the pipes 7, but may be a manhole part that is smaller than the dome. In this case, the protruding part 3 may be constituted only by the manhole cylinder 34 and the manhole cover 35.

Reference Signs List

[0038] 

1

liquefied gas tank

2

tank body

3

protruding part

30

cell

31

peripheral wall

32

ceiling wall

4

first thermal insulation layer

41

outer shell

42

first vacuum space

5

second thermal insulation layer

51

outer cylinder

52

ring plate

53

second vacuum space

6A to 6C

disc

61

manhole

62

manhole cover

7

pipe

Claims

1. A liquefied gas tank comprising:

a tank body that stores liquefied gas;

a protruding part protruding upward from the tank body, the protruding part being a hollow part whose interior communicates with an interior of the tank body;

a first thermal insulation layer that encompasses the tank body;

a cylindrical second thermal insulation layer that encompasses the protruding part except a distal end portion of the protruding part; and

a plurality of discs disposed in a region in the interior of the protruding part, the region overlapping the second thermal insulation layer, the discs partitioning off the interior of the protruding part into a plurality of cells that are arranged in a protruding direction of the protruding part.

2. The liquefied gas tank according to claim 1, wherein
the distal end portion of the protruding part is provided with a manhole, and
each of the plurality of discs is provided with a manhole and mounted with a manhole cover by which the manhole is opened and closed.

3. The liquefied gas tank according to claim 2, wherein
among the plurality of discs, except the disc located at an uppermost position, each disc is mounted with the manhole cover such that the manhole cover is slidable along the disc.

4. The liquefied gas tank according to any one of claims 1 to 3, wherein
the protruding part includes:

a peripheral wall that rises from the tank body; and

a ceiling wall that seals an upper opening of the peripheral wall, and

the plurality of discs are mounted to an inner circumferential surface of the peripheral wall.

5. The liquefied gas tank according to any one of claims 1 to 4, wherein
each of the plurality of discs is a metal plate.

6. The liquefied gas tank according to claims 1 to 5, wherein
the first thermal insulation layer includes:

an outer shell that surrounds the tank body while being spaced apart from the tank body; and

a first vacuum space formed between the outer shell and the tank body, and

the second thermal insulation layer includes:

an outer cylinder that rises from the outer shell and surrounds the protruding part except a distal end portion of the protruding part;

a ring plate that couples an upper end of the outer cylinder and the protruding part; and

a second vacuum space formed between the outer cylinder and the protruding part.

Drawing