JPS6223199B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a double-structured storage tank, and more particularly to an overflow control device for a double-structured storage tank.

[Conventional technology]

In double-walled cryogenic liquid storage tanks, product may enter the annular space between the walls due to any of the following conditions: (1) overfilling of the inner tank; (2) overfilling of the inner tank wall; and (3) leakage from the bottom. In case of leakage through the walls or the bottom, liquid will accumulate at the bottom of the annular space.

In known forms of double-walled cryogenic liquid storage tanks, the annular space between the two walls is filled with a granular insulation material, usually perlite or the like. As liquid accumulates at the bottom of the annulus in a leakage condition and gradually increases in height, this liquid removes the sensible heat stored in it from any component it comes in contact with; and the temperature difference between the components in question and the weight of that component. By acquiring this sensible heat, the low temperature liquid evaporates, thereby transforming from the liquid phase to the gas phase. Depending on the amount of heat gained and the amount of liquid overfill or leakage, large amounts of steam can be generated. At the initial stage, all components in contact with the cold liquid undergo a large temperature drop, so the initial vapor generation rate is very high. Therefore,
A device is needed that can process a large amount of gas without damaging any parts of the tank.

[Problem that the invention seeks to solve]

Granular materials create a very large resistance to gas flow, especially if the product entering the interior of the annulus is due to leakage from the bottom or walls of the inner tank, and at the same time there is a small amount of product inside the tank. This condition is very dangerous for the inner tank if only certain products are present. Resistance to gas flow results in an increase in pressure below the inner tank, which can raise the bottom of the tank and compromise the structural integrity of the inner tank.

This pressure increase can also cause damage to the inner tank walls in the following manner. The gas in the granular material takes the form of fine bubbles that rise between the granular materials while disturbing the state of the granular material.
Although the generation of small bubbles is almost unavoidable,
A point is reached where the bubble becomes too large, at which point it expands between the walls of the annulus and acts like a piston, propelling the particulate material forward until it suddenly ruptures at its surface. This phenomenon is known as "slugging".

If a slugging condition is reached when the inner tank is not fully filled with product, the pressure increase may exceed the design external pressure of the inner tank. Such a pressure increase can lead to buckling of the inner tank walls creating an unusual hazard.

Therefore, in the event that a liquid, particularly a low-temperature liquid such as an ultra-low-temperature liquid, overflows into the annular body of such a double-walled tank, a device is needed to prevent the pressure increase of the gas in the double-walled tank. is necessary.

[Means for solving problems]

The present invention provides an apparatus for controlling the vapor generated when liquid overflows from a double-walled tank into its annular body.

This vapor usually comes from leaks that occur under overfill conditions, and therefore the device of the present invention will be referred to as an overflow (control) device or a leak control device for convenience. However, such terms are not intended to be limited to sources of liquid that produce vapor.

The apparatus of the invention includes an overflow conduit connecting the inner tank and the annulus in communication at or near the overflow level and the bottom of the tank, respectively. Overflow liquid, such as cryogenic fluid, is thus forced into the toroid by the device.

The steam control device included in this overflow control device is
The vapor generated from the liquid exiting the overflow conduit is flowed back into the inner tank for treatment by the tank's vapor control system.

Alternative embodiments include specialized vapor pumping equipment, liquid control equipment, and the like.

In case of overfilling, the liquid flows into a weir located at the top of the inner tank and accumulates at the bottom of the annular space through an overflow treatment device provided in case of such leakage.

The steam control device provides a flow path for steam that has less flow resistance than the path within the particulate material in the annulus. Such low flow resistance is achieved by including a fiberglass bracket in the steam control device. This blanket provides compaction control and has less resistance to gas than granular material.

However, these blankets do not have sufficient capacity to handle the full flow of gas that occurs in leak conditions. For this purpose, the gas passages for this ventilation are mechanically designed to provide even less resistance to air flow than in the case of a glass fiber blanket, and have an area equal to the required design area for the expected steam flow rate. This result is achieved by incorporating a metal cage around the inner tank wall and between this wall and the blanket of the fiberglass compaction control device. The cage forms an annular space or vapor duct for receiving the air flow between the inner tank wall and the blanket, where the only resistance to flow is friction and no other impediments.
These cages have openings large enough to allow a fiberglass blanket to be inserted into the airflow path to obstruct the airflow. Therefore, this too has a low resistance to airflow and is provided with a load distribution device covering the opening of the cage device. In a preferred embodiment, the cover includes a layer of expanded metal overlying the cage. This expanded metal has low resistance to airflow and also has good load holding and load dispersion properties. The fiberglass blanket serves three functions: (1) compaction control, (2) provides one air flow path, and (3) provides a filter for gases flowing through the aerator, and the particulate material This has the function of preventing air from falling into the air and thereby blocking airflow.

Furthermore, the gas flow resistance in the blanket is further reduced by providing folds to the blanket. This fold is normally given in a trapezoidal shape along the circumferential direction of the inner tank, but
This fold significantly increases the area through which gas passes, and therefore greatly reduces the gas flow resistance.

Materials with lower resistance to gas flow are
At the bottom of the toroid, it is used in place of granular insulation for certain parts of the toroid. The design criteria for such materials is that they are good insulators compared to granular insulators. This design criterion is achieved by replacing some of the granular insulation at the bottom of the annulus with a glass fiber material that is a good insulator and has very low resistance to airflow. The glass fibers serve to direct the large amount of gas generated during the initial evaporation of the overflow fluid into the gas passage or evaporation channel.

In a preferred embodiment, a glass fiber filter is provided on top of the glass fibers located at the bottom of the annular body. The glass fibers located at the bottom of the annulus are assembled in such a way that the fibers are parallel to the inner and outer walls of the tank. Therefore, the resistance to airflow is lower when the airflow is in the direction of fiber orientation. Furthermore, the compressive strength of glass fibers increases with respect to the direction of orientation of such fibers, which is a further characteristic since the glass fibers are subjected to large loads of particulate material. Also, if the glass fibers are provided without a filter, particles from the particulate material will flow into the steam duct and block it, thereby impeding the flow of gas through the steam duct.

Once the gas has risen through the steam duct, it flows into the inner tank through an opening in the top of the wall of the inner tank. These openings have an area exactly equal to the cross-sectional area of the steam duct. Also, the top of the fiberglass blanket surface of the compaction control device in contact with the granular insulation is covered with a gas baffle to direct gas through the fiberglass blanket and steam duct into the inner tank. The gas baffle extends approximately 8 to 10 feet from the top of the tank and ends there, leaving the remainder of the blanket in contact with the granular insulation. This prevents cold gas from flowing through the top portion of the granular insulation and coming into contact with the dome roof structure, which would otherwise endanger the roof structure and thus create a very dangerous situation. Become.

Finally, the vent gas that has reached the inner tank is discharged from the inner tank by means of an emergency release device which connects this inner tank to the dome roof via a suspended flat roof.

Furthermore, from the point of view of safety in double-walled tanks, it is not only the equipment that handles large amounts of gas that is most important. Another very important device for reducing the quantitative vapor generation rate is a device for reducing the volume of overflow liquid. Reducing the volume of overflow liquid will reduce the volume of vapor generated.

Other embodiments of the device therefore include means for reducing the volume of overflow liquid. Such other embodiments include means for pumping liquid out of the annulus. As previously mentioned, the annulus of a double-walled tank is generally completely filled with granular insulation. Many problems are encountered when pumping liquid out of granular insulation. Pumping the slurry of granular insulation results in failure of the pumping equipment. In order to avoid situations that lead to such failures, filtration devices are provided. As previously mentioned, the bottom area of the toroid is replaced with glass fibers. Glass fibers are used as filters for the pump inlet pipes. Fiberglass insulation around the pump is also supported in this embodiment. Therefore, a cage made of expanded metal is attached to the end of the pump inlet tube. This cage is empty and acts as a sump to collect the leaking liquid, from which it can be pumped out without any problems. This liquid may not be as clear as the liquid in the inner tank. Therefore, subsequent use and/or
It is necessary to filter it prior to storage, and suitable filter devices can be used to ensure this filtration step.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a dual structure storage tank 20 that includes a base 22, walls 24, and a dome-shaped roof 26. The liquid flow device associated with tank 20 includes liquid inlet pipe 2
8 and a steam outlet pipe 30.

As shown in FIGS. 2 and 3, the tank 20 is separated by a metal outer tank bottom 44.
It includes a concrete bottom 40 that supports a pair of load-bearing bottom insulation layers 42 . Also shown in FIG. 2 is a support ring 46 made of concrete. tank 2
0 is an outer wall surface 5 formed from concrete or the like
0 and a metal inner tank 52 having walls 54 and a bottom 56 . The foamed polyurethane layer
Liner 5 attached to the inner surface of the outer wall surface 50
It is attached to 9.

The inner tank wall 54 is spaced apart from the outer wall 50 so as to define an annular body 60 therebetween. This annular body 60 is filled with a granular heat insulating material 62 such as perlite.

A suspended ceiling board (decker) 70 is placed within the tank, and a heat insulator 72 is placed on top of this deck. The tank also includes a deck suspension member 74 and a heat insulating support member 76.

One embodiment of the overflow control device 80 is shown in FIGS. 2 and 3. This overflow control device 80 has one end 84
Inner tank 52 via an overflow port 86 defined in inner tank wall 54 near the top thereof at
including a flow pipe 82 connected in communication with the interior of the
and includes a central portion 88 extending vertically downwardly near and away from the inner tank wall surface 54 . The flow tube 82 has a lower end 90 with an outlet end 92. The outlet end 92 is oriented away from the inner tank 52 so that liquid from the downflow tube enters the insulation 62 disposed within the annulus 60 adjacent the lower end of the tank. 60
located within.

Rim girder 100 includes a base 102 and a flange 104 that forms a weir to control flow. The interior 106 of this girder has an overflow port 8
It communicates with 6. The rim girder 100 is thus operated at the normal operating level 11 shown in FIG.
2, which is of course above the overflow level 110.

The liquid held within the tank 52 overflows the weir and flows into the downflow tube 82, which is also referred to as an overflow tube and is therefore located near the base of the tank. The small gap between the downflow tube and the tank wall 54 prevents, or at least inhibits, the formation of steam within the downflow tube.

As shown in FIGS. 2 and 3, overflow control system 80 includes a steam duct 130 and a compaction control effect blanket 120. As shown in FIGS. blanket 120
is wrapped around the inner tank wall 54 and is preferably fiberglass. Blanket 12
0 has at least three functions as described above.
As shown in FIGS. 2, 3, 7, and 13, the layer 124 preferably has a height of 2.4 mm.
The blanket 120 is measured over a range of 8 to 10 feet. In other embodiments, the blanket covers only a portion of the tank wall. With these embodiments it is possible to coat only said portions of the tank wall above or below a certain height.

As shown in FIG. 3, a plurality of ducts 130 are formed by folding the blanket 120, with adjacent portions of the blanket 120 in contact with or in close contact with the tank wall 54.
This fold and therefore the duct 130 extends over almost the entire height of the tank. Support member 132 acts to define the folds that form duct 130.

Support member 132 is best shown in FIG.
Bases 136 each resting on tank wall 54
and a chevron bracket 134 having a back portion 138 extending outwardly therefrom. At least two chevron brackets 134 are used for each duct 130. A pair of vertical stiffeners 140 are each attached to the back 138 of the chevron bracket 134 and extend generally vertically to support the edges of each duct 130. The support means for each duct 130 also includes a support bar 142, a plurality of horizontal support bars 144, and a cross tether 145.

As shown in FIGS. 3 and 4, the downflow tubes 82 are positioned at the folds of a pair of adjacent ducts 130, with the top of the inner tank wall 54 extending over each duct 130, as best shown in FIG. An adjacent cut is made to define a steam opening 146. Therefore, duct 130 is a steam duct. It is desirable that there be a plurality of downstream pipes 82.

Annular filter 150 is formed similarly to compaction control blanket 120 and is disposed horizontally within toroid 60. The filter 150 is made of granular heat insulating material 6
2 and provides an element for flow control of steam generated at or near the base of tank 52 by discharging liquid from tank 52 to granular insulation 62 as described above. Fibers that are parallel to the tank walls 50, 54 can be placed adjacent the outlet tube end 92 of the tube so that the resistance to the air flow is reduced when the air flow is parallel to the tank wall. . The fibers within filter 150 can also be oriented to provide suitable flow resistance. Outer layer 124 is attached to the outer portion of the top of compaction control blanket 120 to act as a vapor baffle that allows gas to flow into tank 52 through opening 146.

As shown in FIGS. 2-4, when the liquid level in tank 52 rises above the overflow level, some of this liquid overflows the weir and flows into interior space 106. When there is sufficient liquid in space 106, a portion of this liquid will flow into downflow tube 82 through overflow port 86, as indicated by arrow L in FIG.

The liquid then exits the flow tube 82 through the end 92 and is discharged into the annulus 60. This discharged liquid creates a vapor V which tends to rise into the annular space 60. Since there is a difference in the flow resistance of the tube between the upward path within the granular heat insulating material 62 and the upward path within the steam duct 130, steam flows into the steam duct 130 as shown in FIG. Steam within each steam duct 130 flows upwardly adjacent wall 54 and through steam openings 146 into duct 130.
flows out from.

Steam exiting the steam opening 146 returns to the tank 52 and is processed by the steam control system associated with the kunk. The steam control system associated with the inner tank may include the steam piping 30 shown in FIG. 1 and may include suitable pumping means. As previously mentioned, suitable filters are included to ensure that particulate material is not entrained in the steam flowing through the steam control device.

As shown in FIG. 4, expanded metal in the form of a grid E supports the compaction blankets 120, but perforated plates could also be used instead of this metal plate for the support of these compaction control blankets. . Two forms of perforated plates that can be used are shown in Figures 5 and 6, respectively. Other forms of perforated plates can also be used. Plate 170 in FIG.
may have any other shape, but the blanket 12
Circular hole 172 and polygonal hole 1 must be small enough to prevent 0 from entering the flow path.
It has 74. The plate 176 shown in FIG. 6 has a plurality of equal circular holes 178.

It should also be noted that while the preferred shape of the steam duct is trapezoidal, other shapes such as rectangular can also be used. Furthermore, in other forms of overflow arrangement a single continuous annular steam duct may be used instead of any number of steam ducts, in which case the downflow tube 82 or multiple downflow tubes may be It is located in an annular space defined by an annular steam duct.

It should be noted that while the preferred location for the downflow tube 82 is outside the blanket 120, the tube 82 could also be placed within the blanket.

If a compaction control device is not used, a fibrous layer 122' can be used on the cage surface as shown in FIG.

In another embodiment of the invention, as shown in FIG. 10, means D for forming ducts on the outer wall surface 50 are provided. This duct-forming means D provided on the outer wall surface 50 also has folds in this embodiment of the invention. This fold defines a steam duct, similar to steam duct 130, within tank 52 such that steam flowing upward in the duct on wall 50 flows into tank 52 and is processed by the tank's steam control system. It is communicated with. As shown in FIG. 10, a steel liner 184 is attached to the inside of the outer tank wall 50, and a foamed polyurethane layer 183 is provided thereon. Cage defining means 185, similar to the cage defining means shown in FIG. 4, are placed over the foam layer 183 to define the folds. A metal grid E is placed on the cage definition device 185 and a layer 186 of cloth fibers or the like covers the grid E. A granular heat insulating material 62 is placed inside the annular body, and a glass fiber layer 187 is placed on the inner wall of the tank.

The inner surface of the outer tank metal liner 184 has surface protective insulation over its entire height, or in other embodiments over a portion of its height.

Yet another embodiment of the overflow control system includes a separate steam treatment system. In this embodiment, vapor is collected in a vapor flow channel and processed by equipment separate from the equipment used for processing the vapor from tank 52.

In another embodiment of the invention, the inner tank 5
2 has a domed roof instead of the hanging deck shown in FIG. In this embodiment, the inner tank does not overflow and the venting gas in the annular body 60 flows through the opening 14.
The steam is not evacuated into the inner tank through a notched steam opening such as 6, but instead a preconfigured steam control system is used which in one form includes a separate piping system.

7 and 8 show yet another embodiment of the overflow control device of the present invention. As shown in FIG. 7, a liquid control device 190 is included along with an overflow control device 80. The liquid control device 190 removes liquid from the annular space 60 and includes a plurality of liquid product traps 202 that are mounted on the tank base 22 and receive overflow tube ends 92. Each trap 202 includes a polygonal cage 204 having an outer layer 206 of sheet metal and having compacting glass fibers 208 on the outer surface of this layer 206.
The liquid riser tube 210 is placed with its lower end 212 on the wall of the tank within the cage 204 . A tube 210 extends upwardly from cage 204;
A liquid pump device 25 that is preferably located outside the annular body 60 and outside the tank 20
2 and connected in communication with each other. A submersible pump 253 is placed near the bottom of the tube 210 to pump liquid into the tube. As mentioned above, the cage 204 is
It can be covered with glass fibers with the fibers oriented in the appropriate direction.

Liquid control device 190 prevents liquid buildup. The lower end of riser tube 210 is spaced from base 22 by a sufficient distance to prevent undue liquid accumulation. This liquid control device 190 operates in conjunction with a vapor control device that discharges vapor.

FIG. 13 shows a variation of the liquid control device 190, designated by reference number 190'. The liquid control device 190' includes a sump 26 located adjacent the overflow tube end 92 that receives liquid.
Includes a gravity drainage device such as 0. This device 190'
further includes a tube 262 that connects to the sump 260.
is preferably buried below the level of the tank base 22 where it is coupled in communication with the liquid pumping device 266. This liquid pump device 266 is preferably located outside the tank 20 as shown in FIG. Filter 268 covers sump 260 to prevent particulate insulation from entering liquid control device 190'. A filter 268 can be inserted into the tube 262 so that the particulate material flows through the pump device 26.
6 can be prevented from entering.

The sump 260 may include a plurality of sump or may be a continuous sump surrounding the tank 20 having a plurality of tubes 262 connecting the single continuous sump to a liquid pumping device 266. If there is more than one sump, each sump is connected in communication to a separate or single pumping device, suitably by a separate tube 262 and a filter 268.
are arranged accordingly. Thus, each of the plurality of sumps has an individual filter, and a single successive sump has a single successive filter above it. The number of sump can correspond to the number of downflow tubes as required.

In the embodiment described above, the filter 268 includes a metal grid coated with a woven fabric, such as a fiberglass blanket or woven glass fabric, although other materials may also be used. 7th
The lower surface area of the filter in the illustrated embodiment has a filtration material located within it and outside of the cage 204.

The tank 20 is shown in FIG. 13 and is surrounded by dogbashiri B. Also, although the outer wall surface 50 is disclosed herein as concrete, other materials such as steel, etc. may also be used without departing from the scope of the invention.

A further embodiment of the overflow control device is shown in FIGS. 11 and 12. The overflow control device shown in these figures includes a fiberglass compaction control blanket 120'', designated by reference numeral 80', having an inner layer 122'' attached at various locations on the inner tank wall 54; The outer layer 124'' is in contact with the granular insulation 62 and preferably extends over a tank height range of about 8 to 10 feet, as described above.
Blanket 120'' is similar in function and effect to the above-mentioned blanket 120, but is slightly different in structure.
and 120', with a plurality of holes provided in the inner layer 122''. As best shown in FIG. 12, the blanket 120'' is defined by the folds. A plurality of vertically spaced vapor communication ports 280 are formed in the wall 282 of the vapor duct 130''.Furthermore, the wall 54 of the tank
Vapor holes 146'' are provided in the ports 280 to allow vapor to flow back into the inner tank 52 for treatment by suitable vapor treatment equipment.
0'' and inside the tank 52 and is treated as described above.

A plurality of liquid ports 284 are formed in the inner tank wall 54 near its top. This port is coupled in communication with liquid duct 130'' and is located at a remote location below steam port 146'' near the top of wall 54 such that liquid flows through port 284 and vapor flows within port 146''. The ports 284 correspond to the ports 86 that couple the interior 106 of the rim girder in communication with the downflow tube 82. As shown in FIG.
Steam port 280 extends substantially the entire length of wall 282 to or near the bottom of the inner tank. One liquid port 284 is associated with a liquid duct forming the fold of the blanket as shown in FIGS. 11 and 12.

Liquid flows downwardly within each duct 130 while vapor flows upwardly within the ducts 130''. Thus, in the embodiment of FIG.
There is no downflow tube similar to downflow tube 88. Second
A filter similar to filter 150 shown in the figure can be used to divert vapor back into duct 130''.

Each of the above-mentioned variations in the blanket structure etc. may be adapted to other embodiments as well. Other variations also fall within the scope of the invention.

〔Effect of the invention〕

As explained above, the present invention provides a conduit path for overflow liquid from the inner tank to the annular body and a passage with low resistance for evaporated vapor returning from the annular body to the inner tank, and the granular insulation material acts as a filter. The provision of an overflow control device consisting of a vapor channel with a blanket that prevents rapid pressure build-up due to evaporation of overflow liquid in the annulus and thus dangerous slugging of the granular insulation;
Alternatively, it prevents overcooling of the dome, prevents damage to the tank due to this, and has a great effect of increasing the safety of the tank.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a double structure tank constructed according to the present invention, FIG. 2 is a sectional elevation view of an overflow control device used in the double structure tank of FIG. 1, and FIG. 3 is a perspective view showing a double structure tank constructed according to the present invention. is a cross-sectional view taken along line 3-3 in FIG.
4 is a perspective view of the overflow control device of FIGS. 2 and 3; FIG. 5 is an elevational view of a cover for the cage used in the overflow control device of FIG. 4; and FIG. FIG. 4 is an elevational view showing a further cover for the cage used in the overflow control system of FIG. 4; FIG. 8 is a cross-sectional view taken along line 8--8 of FIG. 7; and FIG. 9 is a detail illustrating a further embodiment of the dual tank overflow control system of the present invention. 10 is a detailed sectional view showing another embodiment of the overflow control device for a double structure tank of the present invention, and FIG. 11 is a detailed sectional view showing another embodiment of the overflow control device for a double structure tank of the present invention. 12 is a cross-sectional view taken along line 12-12 of FIG. 11, and FIG. 13 is a further embodiment of the tank overflow control used in the double-walled tank of FIG. 1. FIG. 2 is a cross-sectional elevational view of the device. 20...Tank, 22...Base, 24...Wall surface, 26...Dome-shaped roof, 28...Inlet pipe, 3
0... Outlet pipe, 40... Concrete bottom, 42
...Insulation layer, 44...Outer tank bottom, 50...
Outer wall surface, 52... Inner tank, 60... Annular body, 80, 80'... Overflow control device, 82... Downflow pipe, 120, 120''... Compaction control blanket, 124, 124''... Glass fiber layer, 13
0...Steam duct, 132...Support part, 150...
... Filter, 170, 176 ... Perforated plate, 19
0,190'...Liquid control device, 204...Liquid trap cage, 210...Riser pipe, 25
3...Liquid pump.

Claims (1)

[Claims] 1. A double-walled tank for storing low-temperature liquids having an inner wall surface, an outer wall surface, and an annular body between which a granular heat insulating material is mainly filled, including the following: from the inner tank to the annular body. a liquid flow of
an overflow control device for regulating the vapor generated by the liquid, the overflow control device having a conduit for conveying the overflow liquid from the inner tank to the annulus and retaining the liquid and vapor at the bottom of the annulus; an overflow weir located at the overflow level of the tank; an overflow port and a flow path for the flow of flowing liquid, said area having a low resistance to the flow of vapor, said vapor channel extending in the annular body around the circumference of the inner or outer wall of the tank; a steam duct provided along the tank, extending vertically from the bottom of the tank to the top of the tank, and having an opening that communicates with the upper space of the tank at the top; and between the heat insulating material of the annular body and the steam duct, or the heat insulating material of the annular body; and a blanket provided between the steam duct and an inner or outer side wall of the tank, providing a path with low flow resistance for steam. 2. A double-walled tank according to claim 1, wherein said area is free space. 3. The double-walled tank according to claim 1, wherein the area is a space filled with an inorganic fiber material. 4. The double-walled tank according to any one of claims 1 to 3, wherein the bracket is folded into a trapezoidal shape along the circumferential direction. 5. The double-walled tank according to claim 4, wherein the folded portion is held by a support member. 6. The double blanket according to any one of claims 1 to 5, wherein the blanket is provided with an outer layer of any one of an expanded metal grid, a perforated plate, and a glass fiber layer. wall tank. 7. Claims 1 to 6, characterized in that the blanket includes a filter disposed within the annular body that serves to regulate the flow rate of vapor generated by the liquid flowing out of the conduit. The double-walled tank according to any one of paragraphs. 8. Any one of claims 1 to 7, characterized in that a baffle plate is provided on the circumferential side surface of a part of the upper part of the inner tank between the blanket and the granular heat insulating material to stiffen the blanket. Double-walled tanks as described in Section. 9. A double-walled tank according to any one of claims 1 to 8, characterized in that the overflow device includes a liquid control device for causing fluid to flow out of the annular body. 10. The double-walled device according to claim 9, wherein the liquid control device includes a riser pipe and a submerged pump provided in a liquid trap cage disposed in the annular body. tank.