A three-step thermal insulation enclosure system suitable for large cryogenic liquid tanks

Abstract

This invention provides a three-tiered thermal insulation enclosure system suitable for large cryogenic liquid tanks. Each insulation panel unit is integrally formed into a three-tiered structure that tapers away from the surface of the large cryogenic liquid tank. The tiered structures of several interconnected insulation panel units together constitute a low-level insulation layer, a middle-level insulation layer, and a high-level insulation layer. Buffer units are disposed between the insulation layers of adjacent insulation panel units. The elasticity of the buffer units corresponding to the low-level and high-level insulation layers is greater than that of the buffer unit corresponding to the middle-level insulation layer. Fixing units secure each insulation panel unit to the surface of the large cryogenic liquid tank. According to this invention, the problem of relative displacement between insulation layers is avoided, making the overall structure of the thermal insulation enclosure system more stable. It provides buffer compensation for insulation layer deformation to prevent deformation and cracking of insulation panel units and gaps between adjacent insulation panel units that would affect the insulation effect, while minimizing the waste of buffer performance.

Description

Technical Field

[0001] This utility model relates to the field of tank enclosure technology, and in particular to a three-step thermal insulation enclosure system suitable for large cryogenic liquid tanks. Background Technology

[0002] Against the backdrop of the rapid development of the new energy industry, the market demand for LNG (liquefied natural gas), an important clean energy source, is also growing rapidly. The production and transportation of LNG mainly rely on its liquefied state storage within large cryogenic tanks, thus placing high demands on the insulation and enclosure systems of these tanks. Current technology involves cutting insulation panels into rectangular or symmetrical shapes, arranging several panels in an array on the tank surface, and inserting buffer strips into the gaps between adjacent panels. However, because the cryogenic temperature transferred from the large cryogenic tank to the insulation panels has a gradient—meaning the insulation panels experience even lower temperatures closer to the tank surface—they undergo greater deformation due to the low temperature. Therefore, the buffer strips need to provide higher cushioning performance. On one hand, this cushioning performance prevents gaps from forming between adjacent insulation panels during use due to temperature deformation, thus affecting the insulation effect on the large cryogenic tank. On the other hand, because the insulation material has a larger coefficient of linear expansion than steel, the cushioning performance is also used to prevent the insulation panels from deforming and cracking. Consequently, this results in a waste of cushioning performance in areas far from the tank surface.

[0003] To address this issue, existing technology has developed stepped insulation panels, consisting of three layers of insulation panels with progressively smaller dimensions facing away from the surface of the large liquid tank. These three layers are stacked and assembled to form a three-layer insulation system. By differentiating the buffer strips corresponding to each of the three insulation layers, the problem of wasted buffering performance is solved. However, due to the issue of connection strength between the three insulation layers, some displacement can occur between them. Existing buffer strip designs only consider the case of displacement between the three insulation layers. If the stepped insulation panel is integrally molded, eliminating the displacement issue, the buffer strip design cannot meet the requirement, as displacement directly affects the effectiveness of the buffering performance. Furthermore, during the hoisting of large cryogenic liquid tanks, external forces can deform the insulation panels, leading to a decrease in the insulation performance of the system. Existing buffer strip designs do not consider this situation. Utility Model Content

[0004] To solve at least one of the aforementioned problems, this utility model provides a three-step thermal insulation enclosure system suitable for large cryogenic liquid tanks.

[0005] Specifically, this utility model is achieved through the following technical solution:

[0006] This utility model provides a three-step thermal insulation enclosure system suitable for large cryogenic liquid tanks, including: thermal insulation panel units, a plurality of thermal insulation panel units are fixed in a horizontal and vertical array on the surface of the large cryogenic liquid tank, each thermal insulation panel unit is integrally formed into a three-step structure that gradually tapers away from the surface of the large cryogenic liquid tank, so that the stepped structures of the plurality of thermal insulation panel units spliced ​​together constitute a low-level thermal insulation layer, a middle-level thermal insulation layer and a high-level thermal insulation layer, wherein the low-level thermal insulation layer is close to the surface of the large cryogenic liquid tank, the high-level thermal insulation layer is away from the surface of the large cryogenic liquid tank, and the middle-level thermal insulation layer is located between the low-level thermal insulation layer and the high-level thermal insulation layer;

[0007] Buffer units are set between the insulation layers of adjacent insulation board units. The buffer units corresponding to the low insulation layer and the high insulation layer have greater elasticity than the buffer units corresponding to the middle insulation layer.

[0008] The fixing unit secures each insulation panel unit to the surface of the large cryogenic liquid tank.

[0009] In some embodiments, between adjacent insulation board units of the low-level insulation layer, the buffer unit is a first buffer strip in a compressed state.

[0010] In some embodiments, in mutually orthogonal first buffer strips, a first buffer strip in one direction extends the entire length, while a first buffer strip in another direction intermittently abuts against the side of the first buffer strip in the one direction.

[0011] In some embodiments, between adjacent insulation board units of the high-level insulation layer, the buffer unit is a third buffer strip. Among the mutually orthogonal third buffer strips, the third buffer strip in one direction extends the entire length, while the third buffer strip in another direction intermittently abuts against the side of the third buffer strip in the first direction.

[0012] In some embodiments, between adjacent insulation board units of the intermediate insulation layer, the buffer unit is a second buffer strip and a buffer block. In the mutually orthogonal second buffer strips, the second buffer strips in two directions abut against the side of the buffer block.

[0013] In some embodiments, the second buffer strip is provided with a buffer base strip, and an elastic groove is provided in the buffer base strip, so that the second buffer strip can be elastically deformed in the horizontal direction; or, the second buffer strip is provided with a buffer base strip, and elastic strips are provided on both sides of the buffer base strip, so that the second buffer strip can be elastically deformed in the horizontal direction.

[0014] In some embodiments, a sealing layer is adhered between the insulation layers of adjacent insulation units on the corresponding stepped structure surface.

[0015] In some embodiments, the fixing unit is configured as a connecting column, the insulation board unit has a through hole that penetrates the thickness of the board, the connecting column passes through the insulation board unit through the through hole, and the two ends of the connecting column are fixed to the surface of the large cryogenic liquid tank and the end piece, respectively. The through hole forms a stepped hole at the end away from the surface of the large cryogenic liquid tank, and a baffle and a sealing insulation block are sequentially arranged in the stepped hole.

[0016] In some embodiments, the first buffer strip is glass wool or elastic felt compressed at a compression ratio of 2.5-3.8 times, wherein the elastic felt has a resilience coefficient K of not less than 44% and a thermal conductivity of not more than 0.04 W / (m·K); or, the buffer base strip of the second buffer strip is made of the same material as the insulation board unit.

[0017] In some embodiments, the buffer base strip of the second buffer strip is made of glass fiber reinforced polyurethane material, and the insulation board unit is made of polyurethane material.

[0018] According to the embodiments of this utility model, the insulation board unit is configured as a three-tiered stepped structure formed by integral molding, which avoids the problem of mutual positional movement between insulation layers and makes the overall structure of the insulation enclosure system more stable. For the integrally molded three-tiered stepped structure, the buffer unit corresponding to the low-temperature insulation layer is configured with high elasticity, so that when the low-level insulation layer causes a large amount of deformation due to low temperature, the high-elasticity buffer unit can compensate for the deformation of the gaps between the insulation board units in real time. By configuring the buffer unit corresponding to the high-level insulation layer with high elasticity, when the high-level insulation layer causes a large amount of deformation due to hoisting, the high-elasticity buffer unit can compensate for the deformation of the gaps between the insulation board units in real time. By configuring the buffer unit corresponding to the middle insulation layer with low elasticity, since the deformation of the middle insulation layer area is relatively small, the waste of buffer performance is avoided to the greatest extent, and the deformation and cracking of the insulation board unit and the gaps between adjacent insulation board units are avoided, thus ensuring the insulation effect of the large low-temperature liquid tank.

[0019] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0021] Figure 1 This is a schematic diagram of a three-step thermal insulation enclosure system suitable for large cryogenic liquid tanks according to one embodiment of the present invention.

[0022] Figure 2 This is an exploded view of a three-step thermal insulation enclosure system suitable for large cryogenic liquid tanks according to one embodiment of this utility model.

[0023] Figure 3 This is a cross-sectional view of a three-step thermal insulation enclosure system for large cryogenic liquid tanks according to one embodiment of the present invention.

[0024] Figure 4 yes Figure 3 A magnified view of a section at point A in the middle;

[0025] Figure 5 This is a partial cross-sectional view of a three-step thermal insulation enclosure system suitable for large cryogenic liquid tanks according to another embodiment of the present invention.

[0026] Figure 6 yes Figure 3 A magnified view of a section at point B in the middle;

[0027] Figure 7 This is a deformation-load test diagram of the elastic felt in one embodiment of the present invention.

[0028] Figure label:

[0029] 10: Insulation board unit; 11: Low-level insulation layer; 12: Mid-level insulation layer; 13: High-level insulation layer;

[0030] 21: First buffer strip; 22: Second buffer strip; 221: Elastic groove; 222: Buffer base strip; 223: Elastic strip; 23: Third buffer strip; 24: Buffer block;

[0031] 31: First sealing layer; 32: Second sealing layer; 33: Third sealing layer;

[0032] 41: Connecting post; 42: End piece; 43: Baffle plate; 44: Sealing and insulation block;

[0033] 50: Tank body. Detailed Implementation

[0034] The present invention will now be discussed with reference to several embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and thus implement the present invention, and are not intended to imply any limitation on the scope of the present invention.

[0035] As used herein, the term "comprising" and its variations are to be interpreted as open-ended terms meaning "including but not limited to"; the terms "embodiment" and "one embodiment" are to be interpreted as "at least one embodiment"; the term "another embodiment" is to be interpreted as "at least one other embodiment"; the terms "first," "second," etc., may refer to different or the same objects; the term "setup" is not limited to direct or indirect connections, nor to specific connection methods. Other explicit and implicit definitions may also be included below.

[0036] Specific numerical values ​​or ranges may be mentioned in the following description. It should be understood that these values ​​and ranges are merely exemplary and may be helpful in putting the ideas of this invention into practice. However, the description of these examples is not intended to limit the scope of this invention in any way. These values ​​or ranges may be set differently depending on the specific application scenario and requirements.

[0037] As mentioned above, existing thermal insulation enclosure systems cannot provide sufficient buffering for the integrally molded stepped structure of the insulation panel, or for the deformation of the insulation panel during hoisting. The three-step thermal insulation enclosure system for large cryogenic liquid tanks proposed in this invention at least partially solves the above problems. The following will refer to... Figures 1-7 This invention describes the structure and working principle of a three-step thermal insulation enclosure system for large cryogenic liquid tanks according to an exemplary embodiment of the present invention. The three-step thermal insulation enclosure system for large cryogenic liquid tanks according to this embodiment mainly includes insulation panel units 10, buffer units, sealing units, and fixing units. Multiple insulation panel units 10 are arranged in a horizontal and vertical array and fixed to the surface of the large cryogenic liquid tank, thus jointly forming the main thermal insulation functional part of the enclosure structure. The buffer units are disposed in the gaps between adjacent insulation panel units 10 to absorb gaps caused by processing errors and deformation of the insulation panels during use. The sealing units provide a sealing and moisture-proof function between the insulation layers. The fixing units fix the insulation panel units 10 to the surface of the large cryogenic liquid tank.

[0038] It should be noted that the three-step thermal insulation enclosure system of this utility model embodiment can be used in any cryogenic liquid tank insulation application, for example, cryogenic storage tanks for chemical raw materials, pharmaceutical raw materials, LNG, etc. For ease of description, the following uses an LNG cryogenic liquid tank corresponding to a type B independent liquid cargo tank as an example to explain the structure and principle of this utility model embodiment. Those skilled in the art will understand that this structure and principle are also applicable to marine type A and type C independent liquid tanks, as well as non-independent integral liquid tanks, internally insulated storage tanks, and also to non-marine large cryogenic liquid tanks.

[0039] The insulation panel unit 10 is integrally molded from insulation material into a three-layer stepped structure. The insulation panel closest to the surface of the large cryogenic liquid tank has the largest size, maximizing the insulation area of ​​the resulting lower insulation layer 11. The insulation panel furthest from the surface of the large cryogenic liquid tank has the smallest size. This arrangement maximizes the insulation effect of the insulation panel material and avoids material waste. Furthermore, to improve the manufacturability of the integral molding process, the size of the middle step is also positioned between the two.

[0040] In one embodiment, the insulation board unit 10 can be made of polyurethane, foam glass, foam ceramic, rock wool, calcium silicate, polystyrene (EPS) or vacuum insulation board. Preferably, polyurethane (PUF) not only has the function of heat preservation, but also provides sufficient strength and deformation capacity, so that the heat preservation enclosure system has better overall structural strength and heat preservation performance.

[0041] In one embodiment, the stepped structure of the insulation board unit 10 is directly cut from a rectangular insulation board. The three-layer stepped structure after molding is stably connected to each other and will not move relative to each other.

[0042] Multiple insulation panel units 10 are spliced ​​together, and the three-layer stepped structure constitutes three insulation layers. From the direction closest to the large cryogenic liquid tank to the direction furthest away from the large cryogenic liquid tank, they are successively the low-level insulation layer 11, the middle-level insulation layer 12, and the high-level insulation layer 13. Among them, the low-level insulation layer 11 bears the lowest temperature, resulting in the largest amount of insulation panel deformation. The high-level insulation layer 13 bears the highest temperature, but the amount of deformation caused by the hoisting external force is the largest. Therefore, the buffer units corresponding to the low-level insulation layer 11 and the high-level insulation layer 13 should also have the greatest elasticity to compensate for the gap changes between adjacent insulation panel units 10.

[0043] Specifically, the buffer unit corresponding to the low-level insulation layer 11 is the first buffer strip 21. Since the insulation board unit 10 in the low-level insulation layer 11 area is the largest and the gap between adjacent insulation board units 10 is the smallest, the first buffer strip 21 that needs to be inserted is in the form of a thin sheet. To ensure sufficient buffering capacity, glass wool is selected and compressed to approximately 2.5-3.8 times its original size before being inserted into the gap. For example, 50mm glass wool is compressed to 13-20mm before being inserted into the gap, thereby giving the glass wool sufficient elastic recovery capacity.

[0044] In another embodiment, to achieve better elastic recovery, an elastic felt with superior resilience can be selected. This felt possesses excellent compression and resilience properties, high tensile strength, and good thermal insulation performance. The elastic felt is constructed from glass fiber through a three-dimensional fiber structure and fixed at high temperature. The resilience coefficient of the elastic felt directly affects its buffering performance in the gaps between insulation board units, and the thermal conductivity of the elastic felt directly affects its temperature transmission barrier performance in the gap area between insulation board units. Therefore, the elastic felt selected in this embodiment has a resilience coefficient K ≥ 44% and a thermal conductivity ≤ 0.04 W / (m·K) (average temperature 0℃). The deformation-load test results of this elastic felt are as follows... Figure 7As shown. In this embodiment of the invention, the elastic felt is compressed to approximately 2.5-3.8 times and then stuffed into the gap. For example, 50mm glass wool is compressed to 13-20mm and then stuffed into the gap, thereby giving the elastic felt sufficient cushioning performance and temperature transmission barrier performance.

[0045] In one embodiment, such as Figure 1 and Figure 2 Taking the four adjacent insulation board units 10 shown as an example, the four insulation board units 10 together form a "+" shaped gap, that is, two mutually orthogonal gaps. In the lower insulation layer 11, the first buffer strip 21 in one direction extends the whole length, and the first buffer strip 21 in the other direction intermittently abuts against its side. With this arrangement, as mentioned above, the deformation of the lower insulation layer 11 is relatively large, and the first buffer strip 21 will also be deformed in its length extension direction due to the lower position. The full-length first buffer strip 21 can compensate for this deformation.

[0046] The buffer unit corresponding to the high-level insulation layer 13 is the third buffer strip 23. The insulation board unit 10 in the high-level insulation layer 13 area is the smallest, and the insulation area of ​​the high-level insulation layer 13 is also the smallest, saving insulation board material. As mentioned above, the high-level insulation layer 13 is subject to large deformation under the action of hoisting external force. The third buffer strip 23 is also made of a highly elastic material, which can ensure sufficient buffering capacity for the gaps between adjacent insulation board units 10 in the high-level insulation layer 13 area. For example, the third buffer strip 23 is made of polyethylene (PEF) material, which can provide sufficient elastic recovery capacity.

[0047] In one embodiment, such as Figure 1 and Figure 2 As shown, in the high-level insulation layer 13, a third buffer strip 23 extends along its entire length in one direction, and a third buffer strip 23 in another direction intermittently abuts against its side. With this arrangement, as mentioned above, the high-level insulation layer 13 is subjected to a large amount of deformation due to the external force of hoisting, and the third buffer strip 23 will also deform in its length extension direction due to the high position. The continuous third buffer strip 23 can compensate for this amount of deformation.

[0048] The buffer unit corresponding to the middle insulation layer 12 is the second buffer strip 22. As mentioned above, the temperature of the middle insulation layer 12 has increased appropriately after the temperature of the lower insulation layer 11. The deformation of the insulation board in this area is relatively small due to temperature. At the same time, the deformation caused by the external force of hoisting is also relatively small. In order to avoid wasting the buffer performance, the second buffer strip 22 is selected as an insulation material with low elastic recovery ability or no elastic recovery ability but with a certain strength support ability. For example, polyurethane (PUF) can provide insulation capacity. At the same time, it is matched with the insulation board unit 10 which also uses polyurethane (PUF) to make the overall insulation performance of the entire middle insulation layer 12 balanced.

[0049] In another embodiment, considering the gap buffer sealing problem between insulation board units, the second buffer strip 22 is made of glass fiber reinforced polyurethane (RPUF), while the insulation board unit is made of polyurethane (PUF) with better insulation effect. Glass fiber reinforced polyurethane has greater strength and requires less at the gaps, so it has little impact on the overall insulation performance of the enclosure system, but it can compensate for the mechanical properties at the gaps.

[0050] As mentioned earlier, due to the small deformation of the intermediate insulation layer 12, such as Figure 1 and Figure 2 As shown, a buffer block 24 is positioned at the center of the "+" shaped gap formed by the four insulation panel units 10. Four second buffer strips 22 abut against the four sides of the buffer block 24. This arrangement simplifies the installation process of the insulation enclosure system. First, the buffer block 24 is inserted into the center position, and then the four second buffer strips 22 are inserted into the gap and abut against its sides. For example, the buffer block 24 can also be made of polyurethane (PUF) material.

[0051] Although the required cushioning performance of the second buffer strip 22 is not overly demanding, in the optimal design, the second buffer strip 22 should ideally possess a certain degree of elastic recovery capability, at least in the horizontal direction. Here, "horizontal direction" refers to the direction along the step surface of the stepped structure of the insulation board unit 10.

[0052] In one embodiment, the second buffer strip 22 is configured to have a buffer base strip 222, within which an elastic groove 221 is formed. The elastic groove 221 can be continuous or discontinuous in the extending direction of the buffer base strip 222, and the extending direction of the elastic groove 221 is orthogonal to the horizontal direction, thereby providing the second buffer strip 22 with elastic deformation capability in the horizontal direction. For example, the number of elastic grooves 221 can be one, two, or more, such as... Figure 4 The two elastic grooves 221 are respectively opened on the buffer base strip 222 near the two sides.

[0053] In one embodiment, such as Figure 5 As shown, the second buffer strip 22 has additional elastic strips 223 on both sides of the buffer base strip 222. The buffer base strip 222 provides thermal insulation. The buffer base strip 222 can be made of the same material as the insulation board unit. For example, the buffer base strip 222 is made of polyurethane (PUF). The elastic strip 223 provides elastic recovery capability. For example, the elastic strip 223 is made of polyethylene (PEF), so that the second buffer strip 22 has buffering capability in the horizontal direction. The buffer base strip 222 can also be made of a different material than the insulation board unit. For example, the insulation board unit is made of polyurethane (PUF), and the buffer base strip 222 is made of glass fiber reinforced polyurethane (RPUF).

[0054] In one embodiment, the sealing unit includes a first sealing layer 31, a second sealing layer 32, and a third sealing layer 33. The first sealing layer 31 is adhered to the stepped structure surface above the first buffer strip 21 to prevent moisture between the lower insulation layer 11 and the middle insulation layer 12. The second sealing layer 32 is adhered to the stepped structure surface above the second buffer strip 22 to prevent moisture between the middle insulation layer 12 and the upper insulation layer 13. The third sealing layer 33 is adhered to the stepped structure surface above the third buffer strip 23 to prevent moisture between the upper insulation layer 13 and the external environment. In one embodiment, the first sealing layer 31, the second sealing layer 32, and the third sealing layer 33 can be selected as a CAC composite film, i.e., a fiberglass composite film with aluminum foil. The CAC composite film is composed of three layers: fiberglass cloth, aluminum foil, and fiberglass cloth, laminated together with an adhesive.

[0055] In another embodiment, the sealing unit may include only one or two of the first sealing layer 31, the second sealing layer 32 and the third sealing layer 33. That is, it is not necessary to provide moisture-proof function between every two spaces of the low insulation layer 11 gap, the middle insulation layer 12 gap, the high insulation layer 13 gap and the external environment.

[0056] In one embodiment, the sealing unit can be bonded to the surface of the stepped structure by adhesive or by hot pressing.

[0057] In one embodiment, each insulation panel unit 10 is fixed to the surface of a large cryogenic liquid tank by a fixing unit. For example... Figure 6 As shown, the fixing unit includes a connecting post 41 and an end piece 42. The connecting post 41 passes through a through hole formed in the insulation plate unit 10. One end of the connecting post 41 is directly fixed to the tank body 50 of the large cryogenic liquid tank. A partition plate can also be placed between the insulation plate unit and the tank body 50. The connecting post 41 passes through a hole opened in the partition plate. For example, the partition plate can be a wooden board. The end piece 42 is connected to the connecting post 41 from the other end. For example, the end piece 42 can be a nut. The end of the connecting post 41 can have a matching external thread. For example, the connecting post 41 can be a connecting screw made of wooden material.

[0058] In one embodiment, the through hole forms a stepped hole at the end away from the surface of the large cryogenic tank. A baffle 43 and a sealing insulation block 44 are sequentially arranged inside the stepped hole. The end piece 42 is pressed against the stepped surface of the stepped hole by the baffle 43. For example, the baffle 43 is made of wood. The sealing insulation block 44 is then inserted above the baffle 43 and the end piece 42 to provide a seal for the through hole and to provide buffer compensation for the stepped hole. For example, the sealing insulation block 44 can be made of the same material as the insulation board unit, or it can be made of compressed glass wool with a proportion of about 50%.

[0059] The description of the embodiments herein, including any references to directions and orientations, is for ease of description only and should not be construed as limiting the scope of protection of this utility model. The description of preferred embodiments involves combinations of features, which may exist independently or in combination; this utility model is not particularly limited to the preferred embodiments. The scope of this utility model is defined by the claims.

[0060] The above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A three-step thermal insulation enclosure system suitable for large cryogenic liquid tanks, characterized in that, include: Insulation panel units, several insulation panel units are arranged in a horizontal and vertical array and fixed on the surface of a large cryogenic liquid tank. Each insulation panel unit is integrally formed into a three-stage stepped structure that gradually tapers away from the surface of the large cryogenic liquid tank. Thus, the stepped structures of several interconnected insulation panel units together form a low-level insulation layer, a middle-level insulation layer and a high-level insulation layer. The low-level insulation layer is close to the surface of the large cryogenic liquid tank, the high-level insulation layer is away from the surface of the large cryogenic liquid tank, and the middle-level insulation layer is located between the low-level insulation layer and the high-level insulation layer. Buffer units are set between the insulation layers of adjacent insulation board units. The buffer units corresponding to the low insulation layer and the high insulation layer have greater elasticity than the buffer units corresponding to the middle insulation layer. The fixing unit secures each insulation panel unit to the surface of the large cryogenic liquid tank.

2. The three-step thermal insulation enclosure system for large cryogenic liquid tanks according to claim 1, characterized in that, Between adjacent insulation board units in the low-level insulation layer, the buffer unit is the first buffer strip in a compressed state.

3. The three-step thermal insulation enclosure system for large cryogenic liquid tanks according to claim 2, characterized in that, In the first buffer strips that are orthogonal to each other, the first buffer strip in one direction extends the entire length, while the first buffer strip in the other direction intermittently abuts against the side of the first buffer strip in the one-way direction.

4. The three-step thermal insulation enclosure system for large cryogenic liquid tanks according to claim 3, characterized in that, Between adjacent insulation board units of the high-level insulation layer, the buffer unit is a third buffer strip. Among the mutually orthogonal third buffer strips, the third buffer strip in one direction extends the entire length, while the third buffer strip in the other direction intermittently abuts against the side of the third buffer strip in the first direction.

5. The three-step thermal insulation enclosure system for large cryogenic liquid tanks according to claim 4, characterized in that, Between adjacent insulation board units in the middle insulation layer, the buffer unit consists of a second buffer strip and a buffer block. In the mutually orthogonal second buffer strips, the second buffer strips in two directions abut against the side of the buffer block.

6. The three-step thermal insulation enclosure system for large cryogenic liquid tanks according to claim 5, characterized in that, The second buffer strip is provided with a buffer base strip, and an elastic groove is provided inside the buffer base strip, so that the second buffer strip can be elastically deformed in the horizontal direction; Alternatively, the second buffer strip may be provided with a buffer base strip, and elastic strips may be provided on both sides of the buffer base strip, so that the second buffer strip can be elastically deformed in the horizontal direction.

7. The three-step thermal insulation enclosure system for large cryogenic liquid tanks according to claim 1, characterized in that, A sealing layer is applied between the insulation layers of adjacent insulation units on the corresponding step structure surface.

8. The three-step thermal insulation enclosure system for large cryogenic liquid tanks according to claim 1, characterized in that, The fixing unit is set as a connecting column, and the insulation board unit has a through hole that penetrates the thickness of the board. The connecting column passes through the insulation board unit through the through hole. The two ends of the connecting column are fixed to the surface of the large cryogenic liquid tank and the end piece, respectively. The through hole forms a stepped hole at the end away from the surface of the large cryogenic liquid tank. A baffle and a sealing insulation block are sequentially installed in the stepped hole.

9. The three-step thermal insulation enclosure system for large cryogenic liquid tanks according to claim 6, characterized in that, The first buffer strip is glass wool or elastic felt compressed at a compression rate of 2.5-3.8 times, wherein the elastic felt has a resilience coefficient K of not less than 44% and a thermal conductivity of not more than 0.04 W / (m·K). Alternatively, the buffer base strip of the second buffer strip may be made of the same material as the insulation board unit.

10. The three-step thermal insulation enclosure system for large cryogenic liquid tanks according to claim 6, characterized in that, The second buffer strip's base strip is made of glass fiber reinforced polyurethane material, and the insulation board unit is made of polyurethane material.

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