JP7320434B2 - Cryogenic liquid storage tank, manufacturing method thereof, and construction method of side cold-heat resistance relaxation layer - Google Patents

Description

The present invention relates to a low-temperature liquid storage tank in which low-temperature liquid of 0°C or lower is stored, a method for manufacturing the same, and a method for constructing a side cooling-heat resistance relaxation layer for protecting the liquid barrier of the low-temperature liquid storage tank from thermal shock.

A conventional low-temperature liquid storage tank includes an inner tank for storing a low-temperature liquid inside and an outer tank for covering the inner tank from the outside. As a side cold-heat resistance relaxation layer, there is known one in which a reinforcing sheet having a mesh structure is provided on the surface of rigid urethane foam (see, for example, Patent Document 1).

Patent No. 3044605 (paragraph [0002], Fig. 4)

In the above-mentioned conventional low-temperature liquid storage tank, if the reinforcing sheet floats or peels off from the surface of the rigid urethane foam, there is a problem that the leaked low-temperature liquid exposes the rigid urethane foam to thermal shock. There has been a demand for mitigation of thermal shock transmitted to the hard urethane foam of the layer.

In the invention of claim 1, which has been made to solve the above problems, a cold insulation layer is arranged between an inner tank in which a low temperature liquid of 0 ° C. or less is stored and an outer tank that covers the outside thereof, and the outer tank While the outer surface of the tank is covered with a concrete liquid barrier, the inner surface of the outer tank contains rigid urethane foam as the cooling layer to suppress leakage of the low-temperature liquid and mitigate thermal shock. A low-temperature liquid storage tank coated with a side cold-heat resistance mitigating layer having a heat insulating layer, wherein the side cold-heat resistance mitigating layer is provided on the inner surface of the heat insulating layer and directs the low-temperature liquid in the surface direction of the outer tank. A cryogenic liquid reservoir having a diffusion layer for diffusion.

The invention of claim 2 is the low-temperature liquid storage tank according to claim 1, wherein the diffusion layer has higher air permeability than the heat insulating layer.

In the invention of claim 3, the air permeability (JIS K 6400-7 B method: 2012/ISO 7231:2010) in the thickness direction of the diffusion layer at the core portion of the diffusion layer is 0.05 to 30 ml/cm ² . /s.

The invention of claim 4 is the low-temperature liquid storage tank according to any one of claims 1 to 3, wherein the diffusion layer is made of urethane foam.

The invention of claim 5 is the low-temperature liquid storage tank according to any one of claims 1 to 4, wherein the diffusion layer is a low-density rigid urethane foam having a density lower than that of the heat insulating layer.

The invention according to claim 6 is the low-temperature liquid storage tank according to claim 5, wherein the diffusion layer made of the low-density rigid urethane foam is directly fixed to the heat insulating layer.

In the invention of claim 7, a cold insulation layer is arranged between an inner tank in which a low-temperature liquid of 0°C or less is stored and an outer tank covering the outside thereof, and the outer surface of the outer tank is made of concrete. A side having a heat insulating layer containing rigid urethane foam as the cold insulating layer on the inner surface of the outer tank in the cold liquid storage tank covered with the liquid bank, in order to suppress the leakage of the cold liquid and mitigate the thermal shock. A first step of applying a urethane foam raw material to the inner surface of the outer tank and foaming and curing it to form a heat insulating layer, and on the inner surface of the heat insulating layer, and a second step of laminating a diffusion layer for diffusing the low-temperature liquid in the surface direction of the outer tank, so that the side cold-heat resistance relaxation layer including the heat insulating layer and the diffusion layer is formed inside the outer tank. This is the construction method of the side cold-heat resistance relaxation layer to be coated on the side.

In the invention of claim 8, a cold insulating layer is arranged between an inner tank in which a low-temperature liquid of 0°C or less is stored and an outer tank covering the outside thereof, and the outer surface of the outer tank is made of concrete. A side having a heat insulating layer containing rigid urethane foam as the cold insulating layer on the inner surface of the outer tank in the cold liquid storage tank covered with the liquid bank, in order to suppress the leakage of the cold liquid and mitigate the thermal shock. A first step of applying a first urethane foam raw material to the inner surface of the outer tank and foaming and curing to form a heat insulating layer, and an inner surface of the heat insulating layer. a second step of applying a second urethane foam raw material and foaming and curing to form a diffusion layer made of low-density rigid urethane foam having higher air permeability and lower density than the heat insulating layer; A method for constructing a side cooling-heat resistance reducing layer, in which the side cooling-heat resistance reducing layer including the heat insulating layer and the diffusion layer is coated on the inner surface of the outer tank.

A ninth aspect of the invention is a method for manufacturing a low-temperature liquid storage tank using the method for constructing a side cold-heat resistance relaxation layer according to claim 7 or 8.

According to the inventions of claims 1, 4, 7, and 9, the leaked low-temperature liquid contacts the diffusion layer before the heat insulating layer containing the rigid urethane foam, and the low-temperature liquid contacts the diffusion layer not only in the thickness direction of the diffusion layer, but also in the diffusion layer. It is also diffused in the surface direction of the outer tank. In the diffusion layer, the low-temperature liquid is diffused in the surface direction of the outer tank, so that the heat insulating layer is prevented from being rapidly cooled locally, and the low-temperature liquid spreading in the surface direction cools down slowly over time. Cooled. As a result, the thermal shock caused by the low-temperature liquid is mitigated by the diffusion layer, and abrupt transmission to the heat insulating layer is reduced.

Then, if the diffusion layer is configured to have higher air permeability than the heat insulating layer as in the inventions of claims 2 and 3, the low temperature liquid flows through the diffusion layer in the plane direction before the low temperature liquid reaches the heat insulating layer. can be diffused. For example, as in claims 5 and 8, if the diffusion layer is made of low-density rigid urethane foam, the low-temperature liquid enters the interior of the low-density rigid urethane foam in contact. At this time, the low-temperature liquid diffuses in the surface direction of the outer tank through the interconnected pores inside the low-density rigid urethane foam.

In addition, by providing the diffusion layer, as described above, the hard urethane foam of the heat insulating layer can be protected from the thermal shock of the low-temperature liquid. No reinforcing sheet may be provided (invention of claim 6).

1 is a cutaway front view of a cryogenic liquid storage tank according to an embodiment of the present disclosure; FIG. Enlarged sectional view of the tank Cross-sectional view of the side thermal resistance mitigating layer Schematic diagram showing the flow of liquefied natural gas entering the diffusion layer made of low-density rigid urethane foam. A diagram showing the state of construction of the side cold-heat resistance relaxation layer on the inner surface of the outer tank Diagram showing the flow of construction method for the side thermal resistance mitigating layer

An embodiment of the present disclosure will be described below with reference to FIGS. 1 to 4. FIG. As shown in FIG. 1, the cryogenic liquid storage tank 100 of this embodiment includes a hollow cylindrical tank portion 40 having an inner tank 20 and an outer tank 30, and a cylindrical liquid barrier surrounding the tank portion 40. 50. The tank part 40 stores the liquefied natural gas L inside the inner tank 20 . Incidentally, the capacity of the low-temperature liquid storage tank 100 is generally 140,000 to 230,000 kL. becomes.

The inner tub 20 and the outer tub 30 are provided with ceiling portions 21 and 31, respectively, and have a structure in which the inside thereof is shut off from the outside. The ceiling portions 21 and 31 have a dome shape with a swollen central portion, and form a space filled with vaporized liquefied natural gas L. Both the inner tank 20 and the outer tank 30 are made of metal. For example, from the viewpoint of low temperature toughness, iron or steel is preferable. In particular, since the inner tank 20 is always exposed to extremely low temperatures, an alloy such as nickel containing iron as a main component, which is excellent in low-temperature toughness, is preferable.

The dike 50 is installed to prevent the diffusion of the liquefied natural gas L in the event of an accidental leakage of the liquefied natural gas L. In this embodiment, the inner surface of the dike 50 is superimposed on The dike 50 is made of prestressed concrete that is hard to crack.

In the tank part 40, the space K formed between the inner tank 20 and the outer tank 30 is provided with a cooling layer 60 for keeping the liquefied natural gas L at about -160°C and reducing the vaporization of the liquefied natural gas L. are provided. The cold insulation layer 60 is composed of a ceiling cold insulation layer 61 , a side cold insulation layer 62 and a bottom cold insulation layer 63 .

Specifically, the space K formed in the ceiling portions 21 and 31 of the inner tank 20 and the outer tank 30 is filled with granular perlite or the like having heat insulating performance as the ceiling cold insulation layer 61 . In the space K formed in the side portions 22 and 32 of the inner tub 20 and the outer tub 30, the inner surface 30S of the outer tub 30 is coated with the side thermal resistance reducing layer 10 as the side cold insulation layer 62. In addition, granular perlite or the like is filled between the side cold-heat resistance relaxation layer 10 and the inner tank 20 in the same manner as the ceiling cold insulation layer 61 . In the space K formed in the bottoms 23 and 33 of the inner tank 20 and the outer tank 30, perlite concrete, lightweight cellular concrete, or the like having load-bearing performance and heat insulation performance is disposed as the bottom cold insulation layer 63. ing. The side cooling-heat resistance reducing layer 10 is formed in order to prevent the cooling-heat shock of the leaked liquefied natural gas L from being rapidly transmitted to the liquid barrier 50 . Here, the side cooling layer 62 corresponds to the "cooling layer" of the present disclosure.

As shown in FIG. 2, the side thermal resistance reducing layer 10 includes the side thermal resistance reducing layer 10S covering the entire inner surface 30S of the outer tank 30 and the inner bottom surface 30T of the outer tank 30. It consists of an annular bottom thermal resistance relaxation layer 10T that covers the entire surface. The outer edge of the bottom thermal resistance reducing layer 10T is continuous with the lower end of the side thermal resistance reducing layer 10S, and the inner edge is bent upward so that the end surface abuts the end surface of the bottom cold insulation layer 63 covering the inner bottom surface 30T. It is Even if the liquefied natural gas L flows into the outer tank 30, the thermal shock can be relieved inside the outer tank 30 without reaching the liquid barrier 50 for a predetermined period.

FIG. 3 shows the cross-sectional structure of the side thermal resistance reducing layer 10 of this embodiment. The side thermal resistance relaxation layer 10 is formed by stacking an underblown layer 12, a heat insulating layer 13 (13A, 13B), and a diffusion layer 14 on the inner surface (inner side surface 30S and inner bottom surface 30T) of the outer tub 30. As shown in FIG.

The heat insulating layer 13 is laminated on the underblown layer 12 and is made of rigid urethane foam formed by foaming and curing a raw material of urethane foam. The heat insulating layer 13 needs to mitigate the thermal shock of the liquefied natural gas L and suppress the impact of the thermal shock on the liquid barrier 50 . Therefore, it is preferable that the rigid urethane foam has excellent heat insulating performance and compressive strength, and that the thickness is thin from the viewpoint of efficient use of space. Specifically, it preferably has a density of 40 to 90 kg/m ³ , air permeability of 1 ml/cm ² /s or less, thermal conductivity of 0.040 W/mK or less, compressive strength of 360 kPa or more, and a thickness of 40 mm. More than 60 mm or less is preferable. In this embodiment, the heat insulating layer 13 is composed of two layers (13A, 13B), but it may be composed of one layer, or may be composed of three or more layers. Here, the skin layer of the heat insulating layer 13 is a high-density urethane layer, and since the ratio of urethane resin is increased compared to the core portion, the heat conductivity is increased and the heat insulation performance is lowered. Therefore, the number of layers constituting the heat insulating layer is preferably as small as possible, and it is more preferable that the heat insulating layer is composed of one or two layers.

The heat insulating layer 13 of this embodiment has a density of 65 kg/m ³ , air permeability of 0.01 ml/cm ² /s or less, thermal conductivity of 0.022 W/mK, and compressive strength of 520 KPa. A method of measurement and a method of preparing a sample for measurement will be described later.

The compressive strength required for the heat insulating layer 13 is determined by setting the height of the dike to 40 m (230,000 kL low-temperature liquid storage tank), and calculated with a safety factor of 2.0 according to "8.4.4 Cold resistance relaxation material", it is about 360 KPa. Therefore, the compressive strength required for the heat insulating layer 13 is 360 KPa or more.

The underblown layer 12 is a layer directly laminated on the inner surface of the outer tank 30 and serves as a primer for ensuring the adhesion of the heat insulating layer 13 . The lower layer 12 is made of the same hard urethane foam as the heat insulating layer 13, and is formed by spraying the same urethane foam raw material as the heat insulating layer 13 onto the inner surface of the outer tank 30 and curing or foaming. The thickness of the underblown layer 12 is preferably 0.1 to 5 mm.

The diffusion layer 14 is laminated on the inner surface of the heat insulating layer 13, constitutes the outermost surface of the side thermal resistance reducing layer 10, and serves as a protective layer that protects the heat insulating layer 13 from thermal shock. Like the heat insulating layer 13, the diffusion layer 14 is formed by foaming and curing a raw material of urethane foam.

In this embodiment, the diffusion layer 14 is made of hard urethane foam with a lower density and higher air permeability than the heat insulating layer 13, but it may be made of soft urethane foam or a fibrous body. When these materials are used, the thickness, basis weight, etc. may be set such that the liquefied natural gas L is difficult to permeate in the thickness direction of the diffusion layer 14 . In addition, in order to facilitate diffusion in the surface direction of the diffusion layer 14, soft urethane foam is heat-press molded so that the major axis of the cells is substantially parallel to the inner surface of the outer tank 30. In the case of a fibrous body, the coating amount (basis weight) and coating method of the binder (adhesive) may be adjusted so that the direction in which the fibers are arranged is substantially parallel to the inner surface of the outer tank 30 . In any case, the liquefied natural gas L can be easily diffused in the surface direction of the diffusion layer 14 by making the air permeability higher than that of the heat insulation layer 13 .

Here, the rigid urethane foam forming the diffusion layer 14 and the heat insulating layer 13 will be described. As shown in FIG. 4, both rigid urethane foams are porous bodies having cells (cells) with a closed cell structure in which each cell P is independent, and the gas enclosed in the cells P is independent. This makes it difficult for the temperature change to be transmitted to the gas in the adjacent bubbles P, thereby exhibiting excellent heat insulating performance. However, the rigid urethane foam that constitutes the heat insulating layer 13 has more cells P having a closed cell structure than the low-density rigid urethane foam that constitutes the diffusion layer 14. The low-density rigid urethane foam has more cells Q having an open cell structure in which some of the cells Q communicate with each other than cells P having a closed cell structure. In other words, the diffusion layer 14 having a higher ratio of the open-celled cells Q has a higher air permeability than the heat insulating layer 13 .

Now, when the liquefied natural gas L leaks from the inner tank 20 , the liquefied natural gas L contacts the diffusion layer 14 before the heat insulating layer 13 . The diffusion layer 14 is locally exposed to rapid cooling, and the liquefied natural gas L enters the inside from the surface (skin layer). Here, since the diffusion layer 14 made of low-density rigid urethane foam has a high ratio of cells Q with an open-cell structure, the liquefied natural gas L passes through the interior of the communicating cells Q and flows through the diffusion layer 14 to the outer tank 30. It can spread laterally. That is, the communicating bubble Q group not only advances the liquefied natural gas L in the thickness direction of the diffusion layer 14 (hereinafter referred to as the “second direction H2”), but also in the direction along the surface of the outer tank 30 (hereinafter referred to as the “second direction H2”). (referred to as “first direction H1”). As a result, the thermal shock of the liquefied natural gas L can be dispersed in the diffusion layer 14 to soften it. As a result, the heat insulating layer 13 is slowly cooled by the liquefied natural gas L diffused in the diffusion layer 14 without being locally subjected to rapid cooling, and thermal shock transmitted to the heat insulating layer 13 is alleviated.

That is, as described above, the liquefied natural gas L that has entered the diffusion layer 14 is diffused in the first direction H1, so that the thermal insulation layer 13 can be prevented from being locally and rapidly cooled. That is, if the diffusion of the liquefied natural gas L in the first direction H1 is not effectively performed, the liquefied natural gas L advances in the second direction H2 at once, exposing the heat insulating layer 13 to local rapid cooling. It will happen. From this point of view, it is necessary to use a material with high liquid diffusibility in the first direction H1 as the diffusion layer 14 of the present disclosure. Materials with high liquid diffusibility in the first direction H1 include materials with high air permeability, such as the low-density rigid urethane foam of the present embodiment. On the other hand, if the air permeability of the diffusion layer 14 is made too high, the speed at which the liquefied natural gas L diffuses in the second direction H2 also increases, and the thermal shock may reach the heat insulating layer 13 at once. Therefore, in addition to low-density rigid urethane foam, for example, in the case of flexible polyurethane foam, by appropriately setting the density, air permeability, the direction of the major axis of cells, etc., the first direction H1 and the second direction The diffusion rate of liquefied natural gas L into H2 can be adjusted. In addition, even in the case of a fibrous body, the diffusion rate of the liquefied natural gas L in the first direction H1 and the second direction H2 can be increased by appropriately setting the basis weight of the binder, the application method, the orientation of each fiber, and the like. can be adjusted.

As the diffusion layer 14 that satisfies the high liquid diffusibility in the first direction H1 as described above, the density of the low-density rigid urethane foam is 7 to 40 kg/m ³ , and the diffusion layer in the core portion has air permeability in the thickness direction. It is preferably 0.05 to 30 ml/cm ² /s and has a compressive strength of 15 to 150 KPa. Moreover, the thickness is preferably 10 mm or more, and is preferably 60 mm or less from an economical viewpoint.

The diffusion layer 14 made of low-density rigid urethane foam used in this embodiment has a density of 10 kg/m ³ , air permeability of 0.3 ml/cm ² /s, and compressive strength of 30 KPa.

Here, regarding the heat insulating layer 13 and the diffusion layer 14 of this embodiment, the density is measured based on JIS K 7222:2005/ISO 845:1988, and the air permeability is measured according to JIS K 6400-7 B method: 2012. / ISO 7231: Measured in accordance with 2010, thermal conductivity was measured in accordance with JIS A 1412-2: 1999 / ISO 8301: 1999, compressive strength was measured in accordance with JIS K 7220: 2006 / ISO 844 : 2004.

Specifically, the following measurement samples were prepared based on JIS A9526:2015 and measured. The sample for measurement is an aluminum plate of 900 mm square and 5 mm thick. Using urethane foam raw material for the heat insulating layer 13, a lower blowing layer 12 of about 3 mm is sprayed, and then two heat insulating layers of about 25 mm are laminated. A heat insulating layer 13 having a thickness of about 50 mm was produced. For the diffusion layer 14 as well, similarly to the heat insulating layer 13, a measurement sample was prepared using the urethane foam raw material for the diffusion layer 14. FIG.

The density was measured by cutting a measurement sample into a 100 mm square×30 mm thickness (no skin layer over the entire surface) so as to include the skin layer of the first heat insulating layer 13A in the thickness direction. The thermal conductivity was measured by cutting a sample for measurement into a 200 mm square×25 mm thick (no skin layer on the entire surface) so as to include the skin layer of the first heat insulating layer 13A in the thickness direction. Compressive strength was measured by cutting out a measurement sample into a 50 mm square×30 mm thickness (no skin layer on the entire surface) so as to include the skin layer of the first heat insulating layer 13A in the thickness direction. The air permeability was produced by cutting out a 220 mm square×10 mm thick (no skin layer over the entire surface) from the second heat insulating layer 13B of the measurement sample. The air permeability was measured in the core portion without including the skin layers of the first heat insulating layer 13A and the second heat insulating layer 13B in the thickness direction.

Next, a method for constructing the side thermal resistance reducing layer 10 will be described with reference to FIGS. Construction of the side thermal resistance relaxation layer 10 is performed by placing the side portions 22 and 32 of the inner tank 20 and the outer tank 30 in the space K in a state where the inner tank 20, the outer tank 30 and the liquid barrier 50 are almost completed. This is done before the granular perlite as the side cooling layer 62 is filled. Therefore, as shown in FIG. 6, workers M, N, and O enter a narrow space K between the side portion 22 of the inner tank 20 and the side portion 32 of the outer tank 30 to carry out construction. At this time, since the bottom cold insulation layer 63 is arranged on the outer tank 30 and the inner tank 20 is arranged thereon, the entrance is normally provided in the ceiling (not shown). The width of the side portion 22 of the inner bath 20 and the side portion 32 of the outer bath 30 is 1000 mm to 2000 mm, and the height is about 45 m.

Of the side thermal resistance mitigating layers 10, the side thermal resistance mitigating layers 10S provided on the inner surface 30S of the outer tank 30 are constructed by attaching to a trolley beam installed on the ceiling (not shown) as shown in FIG. Construction is performed by a worker M or N who has boarded the gondola 70 . The gondola 70 is suspended along the inner side surface 30S of the outer tank 30 in the space K so as to be vertically movable and horizontally movable.

The construction of the side thermal resistance relaxation layer 10 is performed for each of a plurality of construction areas W obtained by dividing the inner side surface 30S and the inner bottom surface 30T of the outer tub 30 at predetermined intervals in the vertical direction. In the construction of the side thermal resistance relaxation layer 10S, the worker M or N who got into the gondola 70 constructs the construction area W in order from the upper end or the lower end. When the construction of a certain construction area W is completed, it moves horizontally to the adjacent construction area W, and similarly construction is repeatedly performed from the upper end or the lower end. It should be noted that when construction is performed on the construction area W in order from the upper end or the lower end, an area that cannot be constructed from the gondola 70 is moved horizontally to the adjacent construction area W without performing construction. As shown in FIG. 5, the area of the side thermal resistance relaxation layer 10S that cannot be constructed from the gondola 70 and the bottom thermal resistance relaxation layer 10T are performed by the worker O after the construction of the side thermal resistance relaxation layer 10S is completed, as shown in FIG. . Alternatively, M or N may get off the gondola 70 each time and work continuously.

FIG. 6 shows the flow of construction of the side thermal resistance reducing layer 10 . As shown in the figure, in the construction of the side thermal resistance reducing layer 10, a first step S1 is first performed by an operator M. As shown in FIG. After that, the second step S2 is performed by the worker N so as to follow the worker M.

In the first step S1, the heat insulating layer 13 is formed by spraying a urethane foam raw material onto the inner surface of the outer tank 30 by a spraying method and foaming and curing the raw material. At this time, before forming the heat insulating layer 13, the under-blown layer 12 is formed by the same spray method.

Specifically, in the first step S1, the worker M sprays the spray gun 90 that he is carrying toward the inner surface of the outer tank 30 to form the lower layer 12, and then sprays again to form the heat insulating layer 13. It is formed to have a predetermined thickness. In this embodiment, the two heat insulating layers 13A and 13B are formed by performing the spraying in two steps. This is because even if it is attempted to form a predetermined thickness with a single spray, the sprayed urethane foam raw material may drip and the predetermined thickness may not be obtained. In this case, after the first spraying is completed, the second spraying is carried out after the hardening progresses and the tackiness (stickiness) of the surface disappears. The first heat insulating layer 13A and the second heat insulating layer 13B are formed so as to have substantially the same thickness.

In this embodiment, the underblown layer 12 is formed by applying the same urethane foam raw material as the heat insulating layer 13 . The presence of the underblown layer 12 can improve the adhesiveness of the first heat insulating layer 13A to the inner surface 30S of the outer tank 30 . In this case as well, after the under-blown layer 12 has been sprayed, it is sprayed after curing progresses and the tackiness of the surface disappears. If the heat-insulating layer 13 is formed directly on the inner surface of the outer tank 30 without providing the under-blown layer 12, the heat is taken away from the portion adhering to the inner surface of the outer tank 30, which is made of metal and has high thermal conductivity. There is a risk that the degree of foaming will be insufficient, or the adhesion between the outer tub 30 and the heat insulating layer 13 will be reduced, and the heat insulating layer 13 will be peeled off from the outer tub 30 .

In the second step S2, the worker N sprays the heat insulating layer 13 with the spray gun 90 that he is carrying to form the diffusion layer 14 made of low-density rigid urethane foam to a predetermined thickness. At this time, a urethane foam raw material that forms a rigid urethane foam having a density lower than that of the heat insulating layer 13 is sprayed.

The configuration of the side thermal resistance reducing layer 10 of the present embodiment and the construction method thereof have been described above. Next, the effects of the side thermal resistance reducing layer 10 and its construction method will be described.

In the side thermal resistance reducing layer 10 of the present embodiment, the heat insulating layer 13 is covered with the diffusion layer 14, and the liquefied natural gas L leaking from the inner tank 20 contacts the diffusion layer 14 before the heat insulating layer 13. do. As the diffusion layer 14 is rapidly cooled locally, the liquefied natural gas L enters from the surface (skin layer) to the inside. Here, since the diffusion layer 14 is made of low-density rigid urethane foam and has many open-cell structures, the liquefied natural gas L spreads in the first direction H1 through the inside of the group of communicating cells Q. , and is diffused into diffusion layer 14 . As a result, the thermal shock is mitigated, the heat insulating layer 13 is no longer exposed to local abrupt cooling, and the thermal shock transmitted to the heat insulating layer 13 is mitigated.

In addition, since the heat insulating layer 13 can be protected from the thermal shock of the liquefied natural gas L by providing the diffusion layer 14, the reinforcing sheet of the mesh structure for reinforcing the surface of the heat insulating layer 13 is not provided as in the conventional art. may

Specifically, in the configuration in which the reinforcing sheet is laminated on the surface of the heat insulating layer 13, the reinforcing sheet is attached to the surface of the heat insulating layer 13 with an adhesive or the like after the first step S1. At this time, there is a risk that the reinforcing sheet will float or come off from the surface of the heat insulating layer 13 due to its rigidity. Therefore, a step of cutting and flattening the surface of the heat insulating layer 13 is required. This process must be performed manually for all the construction areas W, and requires a huge amount of man-hours and costs. Moreover, man-hours and costs for removing the dust are required. Furthermore, dust from cutting chips generated during cutting not only worsens the working environment, but also poses the risk of dust explosion. On the other hand, in the present embodiment, since this step is not required, such problems do not occur and workability can be improved.

Further, since the purpose of the cutting process is to flatten the surface, it is necessary to perform the cutting process after the heat insulating layer 13 is foamed and hardened to develop sufficient strength. If processing such as cutting or grounding is performed before sufficient strength is developed, there is a risk that the material may not be cut flat or may tear. As a guideline, it takes about 24 hours (one day) to develop sufficient strength, which requires an extra number of days, resulting in an increase in cost. On the other hand, in the present embodiment, the second step S2 can be performed after the hardening in the first step S1 has progressed and the tack on the surface has disappeared. This eliminates the time required to wait for foaming and curing of the heat insulating layer 13 in the first step S1. Therefore, the above problem does not occur, and workability can be improved.

[Confirmation experiment]
Regarding the side thermal resistance mitigating layer 10 of the above embodiment, by protecting the heat insulating layer 13 made of rigid urethane foam with the diffusion layer 14 made of low-density rigid urethane foam, the thermal shock can be mitigated. was confirmed by experiments. In this experiment, the side cold-heat resistance relaxation layer 10 was produced in the metal mold, and liquid nitrogen was poured over it to confirm whether or not the heat insulation layer 13 made of rigid urethane foam cracked. The temperature of liquid nitrogen is -196.degree. In addition, since nitrogen is an inert gas and has no risk of fire or the like, it was used as an alternative liquid for experiments.

Specifically, a dismantleable metal mold having internal dimensions of 1600 mm length×700 mm width×100 mm thickness and having an open upper side is prepared. A metal mold is erected (with the length direction and thickness direction as the bottom surface), the bottom surface of the metal mold (the side opposite to the open surface) is regarded as the outer tank 30, and the urethane foam raw material for the heat insulating layer 13 is sprayed to a depth of about 3 mm. After forming the blown layer 12, a heat insulating layer 13 made of rigid urethane foam and having a thickness of 50 mm (a two-layer structure, each layer having a thickness of 25 mm) was formed. Further, a urethane foam raw material for the diffusion layer 14 was sprayed thereon to form a diffusion layer 14 made of low-density rigid urethane foam having a thickness of 10 mm (single-layer structure) to prepare a test piece. Then, the prepared test piece is laid down (the length direction and the width direction are the bottom surface), liquid nitrogen is poured from above (the diffusion layer 14 side), and the liquid surface of the liquid nitrogen is 20 to 30 mm from the diffusion layer 14. height. Thereafter, the liquid nitrogen was replenished at any time so that the liquid level of the liquid nitrogen became 20 to 30 mm, and the liquid nitrogen was allowed to pass for 2 hours. After 2 hours had passed, the liquid nitrogen was removed from the metal mold, and the presence or absence of cracks was visually confirmed. When cracks were generated, a solvent-diluted dye was dripped from the surface of the cracks with a dropper and allowed to stand for about 1 hour to color the cracks. After that, the metal mold was dismantled, a test piece was taken out, the test piece was cut, and the cross section of the cut was visually observed to confirm the presence or absence of cracks in the heat insulating layer 13 made of rigid urethane foam. For comparison, a comparison sample with only a heat insulating layer (50 mm thick (two-layer structure, thickness of each layer is 25 mm)) without the diffusion layer 14 made of low-density rigid urethane foam, and for reference, a heat insulating layer (50 mm A reference sample (conventional configuration) was prepared by fixing a reinforcing sheet adhesive to the surface of a thickness (two-layer structure, each layer having a thickness of 25 mm).

As a result, the thermal insulation layer 13 of the side thermal resistance relaxation layer 10 provided with the diffusion layer 14 made of low-density rigid urethane foam and the thermal insulation layer of the conventional side thermal resistance relaxation layer having a reinforcing sheet on the surface of the thermal insulation layer , no cracks occurred. On the other hand, the heat insulating layer of the comparative sample had many cracks. From this experiment, it was found that by protecting the heat insulating layer 13 made of rigid urethane foam with the diffusion layer 14 made of low-density rigid urethane foam, it is possible to suppress the occurrence of cracks in the hard urethane foam of the heat insulating layer 13 when subjected to thermal shock. was confirmed. In addition, it was confirmed that the side thermal resistance mitigating layer of the present disclosure mitigates thermal shock in the same manner as a conventional side thermal resistance mitigating layer having a reinforcing sheet on the surface of a heat insulating layer.

[Other embodiments]
(1) In the above embodiment, the low-temperature liquid storage tank 100 stores liquefied natural gas L, but other low-temperature liquid such as liquefied propane gas may be used.

(2) In the above embodiment, the tank part 40 has the ceiling parts 21 and 31, but it may have a structure in which a lid is provided and the top is open.

(3) In the above embodiment, the diffusion layer 14 made of low-density rigid urethane foam is one layer, but multiple layers may be laminated.

(4) In the above embodiment, a reinforcing sheet having a mesh structure may be laminated between the heat insulating layer 13 and the diffusion layer 14 .

At this time, a step S12 of laminating a reinforcing sheet on the heat insulating layer 13 is performed between the first step S1 and the second step S2. In step S12, the reinforcing sheet is superimposed on the heat insulating layer 13 and temporarily fixed with a tucker or the like, and then the second step S2 is performed, whereby the heat insulating layer is formed so that the reinforcing sheet is included in the low-density rigid urethane foam as the diffusion layer 14. 13 may be fixed. This eliminates the need for an adhesive for attaching the reinforcing sheet to the heat-insulating layer 13, and also eliminates the need for the step of flattening the heat-insulating layer 13.

(5) The diffusion layer of the present disclosure is not limited to the diffusion layer 14 made of a low-density rigid urethane foam layer as long as it diffuses the entering liquefied natural gas L in the first direction H1. For example, a fibrous body may be mentioned, and a glass mat or a non-woven fabric or the like may be used, the heat insulating layer 13 side of which is treated to inhibit the permeation of the low-temperature liquid.

Moreover, a flexible urethane foam may be used. In this case, by adjusting the density, air permeability, etc. of the flexible urethane foam, it is possible to diffuse in the first direction H1 while suppressing permeation in the second direction H2. In particular, by hot-pressing the soft urethane foam, the internal air bubbles (cells) can be collapsed and extended in the first direction H1, making it easier for the liquefied natural gas L to diffuse in the first direction H1.

REFERENCE SIGNS LIST 10 side thermal resistance relaxation layer 13 heat insulating layer 14 diffusion layer 20 inner tank 30 outer tank 62 side cold insulation layer (cold insulation layer)
50 Liquid barrier 100 Cryogenic liquid storage tank L Liquefied natural gas (Cryogenic liquid)

Claims (9)

A cold insulation layer is arranged between an inner tank in which a low-temperature liquid of 0° C. or less is stored and an outer tank that covers the outside thereof, and the outer surface of the outer tank is covered with a concrete liquid barrier, The inner surface of the outer tank is coated with a side cold-heat resistance relaxation layer having a heat-insulating layer containing rigid urethane foam in order to suppress leakage of the low-temperature liquid and mitigate cold-heat shock as the cold-insulating layer. a liquid reservoir,
The low-temperature liquid storage tank, wherein the side cold-heat resistance relaxation layer has a diffusion layer on the inner surface of the heat insulating layer for diffusing the low-temperature liquid in the surface direction of the outer tank. 2. The cryogenic liquid storage tank according to claim 1, wherein said diffusion layer has higher air permeability than said heat insulating layer. The air permeability (JIS K 6400-7 B method: 2012/ISO 7231:2010) in the thickness direction of the diffusion layer at the core portion of the diffusion layer is 0.05 to 30 ml/cm ² /s. 3. The cryogenic liquid storage tank according to 1 or 2. 4. The cryogenic liquid storage tank according to any one of claims 1 to 3, wherein said diffusion layer is urethane foam. 5. The cryogenic liquid storage tank according to any one of claims 1 to 4, wherein said diffusion layer is a low-density rigid urethane foam having a density lower than that of said heat insulating layer. 6. The cryogenic liquid storage tank according to claim 5, wherein said diffusion layer made of said low-density rigid urethane foam is directly attached to said heat insulating layer. A cooling layer is arranged between an inner tank in which a low-temperature liquid of 0°C or less is stored and an outer tank covering the outside thereof, and the outer surface of the outer tank is covered with a concrete dike. The inner surface of the outer tank of the low-temperature liquid storage tank is coated with a side cold-heat resistance relaxation layer having a heat-insulating layer containing rigid urethane foam as the cold-insulating layer, in order to suppress leakage of the low-temperature liquid and mitigate thermal shock. A construction method for
A first step of applying a urethane foam raw material to the inner surface of the outer tank and foaming and curing it to form a heat insulating layer;
a second step of laminating a diffusion layer for diffusing the low-temperature liquid in the surface direction of the outer tank on the inner surface of the heat insulating layer,
A method for constructing a side cooling-heat resistance reducing layer, in which the side cooling-heat resistance reducing layer including the heat insulating layer and the diffusion layer is coated on the inner surface of the outer tub. A cooling layer is arranged between an inner tank in which a low-temperature liquid of 0°C or less is stored and an outer tank covering the outside thereof, and the outer surface of the outer tank is covered with a concrete dike. The inner surface of the outer tank of the low-temperature liquid storage tank is coated with a side cold-heat resistance relaxation layer having a heat-insulating layer containing rigid urethane foam as the cold-insulating layer, in order to suppress leakage of the low-temperature liquid and mitigate thermal shock. A construction method for
A first step of applying a first urethane foam raw material to the inner surface of the outer tank and foaming and curing to form a heat insulating layer;
A second urethane foam raw material is applied to the inner surface of the heat insulating layer and foamed and cured to form a diffusion layer made of low-density rigid urethane foam having higher air permeability and lower density than the heat insulating layer. go through the process and
A method for constructing a side cooling-heat resistance reducing layer, in which the side cooling-heat resistance reducing layer including the heat insulating layer and the diffusion layer is coated on the inner surface of the outer tank. A method for manufacturing a low-temperature liquid storage tank using the method for constructing a side cold-heat resistance relaxation layer according to claim 7 or 8.

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