A low-temperature composite insulation layer and its preparation method and its application in vehicle-mounted low-temperature hydrogen storage tank

Abstract

The present invention proposes a low-temperature composite insulation layer, a preparation method thereof, and an application in a vehicle-mounted low-temperature hydrogen storage tank. The composite insulation layer includes a hollow microsphere layer and a multi-layer insulation layer; the hollow microsphere layer includes a support body and a hollow microsphere powder; the hollow microsphere powder is filled inside the support body to form a hollow microsphere layer; the multi-layer insulation layer includes at least one of a uniform density multi-layer insulation material layer, a variable density multi-layer insulation material layer, a uniform density integrated insulation film, and a variable density integrated insulation film. The composite insulation layer is a composite of a hollow microsphere layer and a multi-layer insulation layer, giving full play to the advantages of the two insulation layers. In a high vacuum, the point-contact hollow microspheres can extend the solid heat conduction path and minimize solid heat transfer. The multi-layer insulation layer can effectively block radiation heat transfer. The two are combined to form a composite insulation layer, which has better insulation performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-temperature thermal insulation, and in particular relates to a composite thermal insulation layer and a preparation method thereof, and application in a vehicle-mounted low-temperature hydrogen storage tank. Background Art

[0002] Hydrogen can be produced from water, and its combustion product is water. Therefore, hydrogen energy is a renewable energy and also a clean energy. It has a high calorific value of combustion. The heat generated by burning the same mass of hydrogen is about three times that of gasoline. In recent years, with the rapid development of hydrogen energy technology, its application in automobiles has become increasingly mature. The storage of on-board hydrogen energy is crucial, which determines the mileage, safety and cost of the car. The storage of on-board hydrogen energy can be divided into chemical storage, gas compression storage and cryogenic storage. Chemical storage has limited hydrogen storage and high cost. It is currently in the research stage and is less used. The pressure required for gas compression storage is high, and the pressure resistance of the storage tank is high, resulting in a high cost of the storage tank and is not conducive to driving safety. Cryogenic storage has a high energy density and low storage pressure. It is a promising on-board hydrogen energy storage method. In cryogenic storage, in order to reduce the evaporation of liquid hydrogen, the application of cryogenic insulation system is key, and an efficient cryogenic insulation system is essential for saving energy and protecting the environment.

[0003] At present, the main material used in low-temperature insulation is multi-layer insulation material, which has extremely low thermal conductivity (1×10 -5 W / m·K), and is known as a "super insulation material". Multilayer insulation materials have excellent insulation performance under high vacuum conditions, but their insulation performance is highly dependent on the vacuum degree. When trace gases enter the insulation layer, their insulation performance will drop significantly. In low vacuum (1×10 -3 -1Pa), as trace amounts of gas enter the insulation layer, gas thermal conductivity gradually increases and becomes the main heat transfer method. At this point, the thermal conductivity of the multilayer insulation material will drop by 1-2 orders of magnitude.

[0004] When the high vacuum environment is lost, the thermal insulation performance of the multi-layer insulation material will drop sharply, especially in the atmospheric pressure environment, the multi-layer insulation material almost loses its thermal insulation performance. At atmospheric pressure, organic foam materials have a low low-temperature thermal conductivity of about 0.015W / m·K, so organic foam and multi-layer insulation materials can be used to form a composite insulation layer. Foam mainly plays an insulating role at atmospheric pressure, and multi-layer insulation materials mainly play an insulating role at high vacuum. The design and preparation of cryogenic hydrogen storage tanks are mainly based on high vacuum environments to ensure the best insulation effect. Therefore, when cryogenic hydrogen storage tanks are used normally, organic foam has almost no insulation effect.

[0005] However, for cryogenic hydrogen storage tanks, the thermal insulation performance of the insulation layer under atmospheric pressure is also very important. Once the insulation layer is damaged, such as when a car is involved in a traffic accident or a vacuum valve is damaged, air enters the insulation layer. Due to the strong gas thermal conductivity and convection heat transfer, the cryogenic hydrogen will expand rapidly after absorbing heat, and the pressure in the storage tank will increase rapidly, making it difficult to ensure safety, especially for flammable and explosive gases such as hydrogen. Therefore, in order to improve the safety of hydrogen storage tanks under atmospheric pressure, the low-temperature insulation layer needs to have certain thermal insulation performance under atmospheric pressure. Therefore, there is a need for an insulation layer that ensures insulation under atmospheric pressure while having better thermal insulation performance in high vacuum to low vacuum environments. Summary of the invention

[0006] In order to improve the deficiencies of the prior art, the present invention provides a composite thermal insulation layer including a hollow microsphere layer and a multi-layer thermal insulation layer, and a preparation method thereof, and an application in a vehicle-mounted low-temperature hydrogen storage tank in view of the defect that organic foams such as polyurethane in the existing composite thermal insulation layer almost lose their thermal insulation performance under high vacuum to low vacuum environments. The composite thermal insulation layer can effectively solve the shortcomings of the above-mentioned prior art. The thermal insulation performance of the composite thermal insulation layer at atmospheric pressure (normal pressure) is equivalent to that of the existing composite thermal insulation layer; at high vacuum to low vacuum, the thermal insulation performance of the composite thermal insulation layer is significantly better than that of the existing composite thermal insulation layer. While ensuring the thermal insulation effect at atmospheric pressure, the composite thermal insulation layer can achieve a better thermal insulation effect in the range of high vacuum to low vacuum.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A composite thermal insulation layer, comprising a hollow microsphere layer and a multi-layer thermal insulation layer;

[0009] The hollow microsphere layer comprises a support and hollow microsphere powder; the hollow microsphere powder is filled inside the support to form a hollow microsphere layer;

[0010] According to the present invention, the multi-layer insulation layer comprises at least one of a uniform density multi-layer insulation material layer, a variable density multi-layer insulation material layer, a uniform density integrated insulation film and a variable density integrated insulation film.

[0011] According to the present invention, the thickness of the hollow microsphere layer is 5-50 mm, for example, 10-30 mm, such as 5 mm, 10 mm, 15 mm, 20 mm, 30 mm, 40 mm, 50 mm.

[0012] According to the present invention, the material of the support is a material with low thermal conductivity, good air permeability, small pore size and certain strength, such as non-woven fabric. The support can be a breathable cloth bag, and the shape can be block or strip; the support is used to wrap the loose hollow microsphere powder to prevent it from leaking out during use and losing its insulation performance.

[0013] According to the present invention, the size of the support is not particularly limited. For example, the maximum thickness of the support is the same as the thickness of the hollow microsphere layer. For example, when the thickness of the support is half the thickness of the hollow microsphere layer, two support structures can be provided, and the hollow microsphere powder is filled inside each support structure, and the thickness of the central microsphere layer is regulated by controlling the filling rate of the hollow microsphere powder. Similarly, the length and width of the support can be adjusted according to the required size of the composite insulation layer.

[0014] According to the present invention, the hollow microsphere powder includes a mixture of one or more of hollow glass microspheres, hollow ceramic microspheres, polymer hollow microspheres, and silicon oxide hollow microspheres.

[0015] According to the present invention, in the hollow microsphere layer, the filling volume of the hollow microsphere powder is 75%-95%, wherein the filling volume is the percentage of the hollow microsphere powder in the total volume of the support.

[0016] According to the present invention, the hollow microsphere powder is selected from commercially available hollow microspheres; for example, selected from the hollow glass microspheres disclosed in Chinese patent document CN201210056295.5.

[0017] For example, the true density of the hollow microsphere powder is 0.10-0.50 g / cm 3 ; The particle size of the hollow microsphere powder is 10-200μm; the compressive strength of the hollow microsphere powder is 1-55MPa, or 1-30MPa.

[0018] According to the present invention, a getter can be added to the hollow microsphere powder; the amount of the getter is 0-5 vol% of the volume of the hollow microsphere powder; the getter is selected from activated carbon, molecular sieve and the like.

[0019] As described above, the multi-layer insulation layer includes at least one of a uniform density multi-layer insulation material layer, a variable density multi-layer insulation material layer, a uniform density integrated insulation film, and a variable density integrated insulation film.

[0020] According to one embodiment of the present invention, the uniform density multilayer thermal insulation material layer includes a reflective layer and a spacer layer; the reflective layer and the spacer layer are alternately stacked, specifically, the reflective layer and the spacer layer are alternately stacked in a ratio of 1:1, that is, a layer of reflective layer, a layer of spacer layer, a layer of reflective layer, a layer of spacer layer, ... are arranged in this way to form a uniform density multilayer thermal insulation material layer.

[0021] Exemplarily, the uniform-density multilayer thermal insulation material layer includes 30 reflective layers and 30 spacer layers; the 30 reflective layers and the 30 spacer layers are alternately stacked to form a uniform-density multilayer thermal insulation material layer.

[0022] According to one embodiment of the present invention, the uniform density multilayer thermal insulation material layer includes a thermal insulation material unit layer, and the thermal insulation material unit layer includes a reflective layer and a spacer layer; the reflective layer and the spacer layer are alternately stacked; the reflective layer and the spacer layer are alternately stacked in a 1:1 ratio, that is, a layer of reflective layer, a layer of spacer layer, a layer of reflective layer, a layer of spacer layer, ... are arranged and sewn in this way to form a thermal insulation material unit layer, and several thermal insulation material unit layers are stacked to form a uniform density multilayer thermal insulation material layer.

[0023] Exemplarily, the uniform density multilayer insulation material layer includes 6 insulation material unit layers, each insulation material unit layer includes 10 reflective layers and 10 spacer layers; the 10 reflective layers and the 10 spacer layers are alternately stacked; the insulation material unit layer including 10 reflective layers and 10 spacer layers is arranged and sewn in this way to form a uniform density multilayer insulation material layer. The 6 insulation material unit layers are stacked to form a uniform density multilayer insulation material layer.

[0024] According to one embodiment of the present invention, the variable density multilayer insulation material layer includes a reflective layer and a spacer layer; the reflective layer and the spacer layer are alternately stacked, specifically, the reflective layer and the spacer layer are alternately stacked in a ratio of 1:N (N is a positive integer and 1≤N≤10), that is, one reflective layer, N spacer layers, one reflective layer, N spacer layers, ... are arranged, and the number of adjacent spacer layers can be the same or different, that is, N is the same or different, and is independently selected from 1≤N≤10, and the variable density multilayer insulation material layer is arranged and formed in this way.

[0025] Exemplarily, the variable density multilayer insulation material layer includes 7 reflective layers and 42 spacer layers; the ratio of the reflective layers to the spacer layers is 1:6; that is, 1 reflective layer and 6 spacer layers are stacked to form a variable density multilayer insulation material layer.

[0026] Exemplarily, the variable density multilayer insulation material layer includes 30 reflective layers and 120 spacer layers; the ratio of the reflective layers to the spacer layers is 1:6, 1:4 and 1:2; the 1-10 layers are arranged in a stacked manner of 1 reflective layer and 6 spacer layers, the 11-20 layers are arranged in a stacked manner of 1 reflective layer and 4 spacer layers, and the 21-30 layers are arranged in a stacked manner of 1 reflective layer and 2 spacer layers, to form a variable density multilayer insulation material layer.

[0027] According to one embodiment of the present invention, the variable density multi-layer insulation material layer includes an insulation material unit layer, and the insulation material unit layer includes a reflective layer and a spacer layer; the reflective layer and the spacer layer are alternately stacked; the reflective layer and the spacer layer are alternately stacked in a ratio of 1:N (N is a positive integer and 1≤N≤10), that is, one reflective layer, N spacer layers, one reflective layer, N spacer layers, ... are arranged, and the number of adjacent spacer layers can be the same or different, that is, N is the same or different, and is independently selected from 1≤N≤10, and the insulation material unit layer is formed by arranging and stitching in this way, and several insulation material unit layers are stacked to form a variable density multi-layer insulation material layer.

[0028] Exemplarily, the variable-density multi-layer insulation material layer includes 7 insulation material unit layers, each insulation material unit layer includes 1 reflective layer and 6 spacer layers; the ratio of the number of reflective layers to the spacer layers is 1:6; that is, 1 reflective layer and 6 spacer layers are stacked and arranged, and are arranged and stitched in this way to form an insulation material unit layer including 1 reflective layer and 6 spacer layers, and the 7 insulation material unit layers are stacked to form a variable-density multi-layer insulation material layer.

[0029] Exemplarily, the variable density multilayer insulation material layer includes 3 insulation material unit layers, the first insulation material unit layer includes 1 reflective layer and 6 spacer layers; the ratio of the number of reflective layers to the spacer layers is 1:6; that is, 1 reflective layer and 6 spacer layers are stacked and arranged in such a way that they are arranged and stitched to form an insulation material unit layer including 1 reflective layer and 6 spacer layers, the second insulation material unit layer includes 1 reflective layer and 4 spacer layers; the ratio of the number of reflective layers to the spacer layers is 1:4; that is, 1 reflective layer The reflective layer and four spacing layers are stacked and arranged in such a way that they are arranged and sewn to form a heat-insulating material unit layer including one reflective layer and four spacing layers; the third heat-insulating material unit layer includes one reflective layer and two spacing layers; the ratio of the number of reflective layers to the spacing layers is 1:2; that is, one reflective layer and two spacing layers are stacked and arranged in such a way that they are arranged and sewn to form a heat-insulating material unit layer including one reflective layer and two spacing layers, and three heat-insulating material unit layers are stacked to form a variable-density multi-layer heat-insulating material layer.

[0030] In one embodiment, the total number of the uniform density multi-layer thermal insulation material layers is 10-100 layers.

[0031] In one embodiment, the total number of layers of the variable-density multi-layer thermal insulation material layer is 10-100 layers.

[0032] According to the present invention, the thickness of each reflective layer is 0.01-0.03 mm, such as 0.01 mm, 0.02 mm, 0.03 mm; the thickness of each spacer layer is 0.1-0.3 mm, such as 0.1 mm, 0.2 mm, 0.3 mm.

[0033] According to the present invention, the reflective layer is selected from aluminum foil or aluminum-plated polyester film; the spacer layer is selected from polyester mesh, nylon mesh or glass fiber paper.

[0034] According to the present invention, the integrated thermal insulation film includes a reflective screen and a spacer attached to the reflective screen.

[0035] According to the present invention, the integrated thermal insulation film can be prepared into a uniform density integrated thermal insulation film or a variable density integrated thermal insulation film according to the height of the spacer;

[0036] Among them, if multiple integrated insulation films with the same spacer height are arranged together, a uniform density integrated insulation film is formed; if multiple integrated insulation films with different spacer heights are arranged together, a variable density integrated insulation film is formed.

[0037] In one embodiment, the total number of layers of the uniform density integrated thermal insulation film is 10-100 layers.

[0038] In one embodiment, the total number of layers of the variable density integrated thermal insulation film is 10-100 layers.

[0039] According to the present invention, the thickness of the reflective screen is 0.01-0.03 mm, for example, 0.01 mm, 0.02 mm, 0.03 mm, and the reflective screen is selected from one of aluminum foil, gold foil, silver foil, copper foil, nickel foil, and metal-plated polymer film.

[0040] According to the present invention, the thickness of the spacer is 0.01-10 mm, and the spacer comprises hollow microspheres and an adhesive, wherein the adhesive is an organic adhesive or an inorganic adhesive.

[0041] According to the present invention, the spacers may be distributed on the reflective screen in a matrix form.

[0042] According to the present invention, the composite thermal insulation layer further comprises a vacuum cover for sealing the composite thermal insulation layer.

[0043] According to the present invention, the vacuum cover has a vacuum hole, and the vacuum degree inside the vacuum cover is preferably 1×10 -3 Pa or above.

[0044] The present invention also provides a method for preparing the composite thermal insulation layer, comprising the following steps:

[0045] 1) filling the hollow microsphere powder inside the support to prepare a hollow microsphere layer;

[0046] 2) preparing a multi-layer insulation layer; preferably, the multi-layer insulation layer is at least one of a uniform density multi-layer insulation layer, a variable density multi-layer insulation layer, a uniform density integrated insulation film, and a variable density integrated insulation film;

[0047] 3) Arranging the hollow microsphere layer and the multi-layer thermal insulation layer together to obtain a composite thermal insulation layer.

[0048] Exemplarily, the preparation of the uniform density multi-layer insulation layer includes the following method:

[0049] a) Preparation of a uniform density multi-layer insulation layer: The reflective layer and the spacer layer are alternately stacked in a ratio of 1:1, that is, M layers of reflective layers, M layers of spacer layers, M layers of reflective layers, M layers of spacer layers, ... are arranged in this way to form a uniform density multi-layer insulation material layer, wherein M is an integer greater than or equal to 1, for example, M is an integer between 1-10.

[0050] Wherein, the total number of layers of the uniform density multi-layer insulation layer is 10-100 layers.

[0051] Exemplarily, the preparation of the variable density multi-layer insulation layer includes the following method:

[0052] b) Preparation of variable density multi-layer insulation layer: reflective layers and spacer layers are alternately stacked in a ratio of 1:N (N is a positive integer and 1≤N≤10), that is, one reflective layer, N spacer layers, one reflective layer, N spacer layers, ... are arranged, and the number of adjacent spacer layers can be the same or different, that is, N is the same or different, and is independently selected from 1≤N≤10, and a variable density multi-layer insulation material layer is arranged and formed in this way.

[0053] Wherein, the total number of layers of the variable-density multi-layer insulation layer is 10-100 layers.

[0054] Exemplarily, the preparation of the uniform density integrated thermal insulation film includes the following method:

[0055] c) Preparation of uniform density integrated thermal insulation film: The integrated thermal insulation films with spacers of the same height are stacked together to obtain a uniform density integrated thermal insulation film.

[0056] Exemplarily, the preparation of the variable density integrated thermal insulation film includes the following method:

[0057] d) Preparation of variable density integrated thermal insulation film: integrated thermal insulation films with spacers of different heights are stacked together to obtain a variable density integrated thermal insulation film.

[0058] The preparation method of the integrated heat-insulating film is as follows: spacers are arranged on a reflective screen, and solidified to obtain an integrated heat-insulating film with spacers attached to the surface of the reflective screen.

[0059] The arrangement method is selected from one or more combinations of 3D printing, screen printing, roller coating, spraying, scraping, dotting and screen printing.

[0060] The integrated thermal insulation film can be made into a uniform density integrated thermal insulation film or a variable density integrated thermal insulation film according to the change of the spacer height.

[0061] Furthermore, the composite insulation layer is formed into a vacuum environment. Preferably, the vacuum degree is 1×10 -3 Pa or above.

[0062] Exemplarily, the composite thermal insulation layer is sealed with a vacuum cover. A vacuum pump is connected to the vacuum hole on the vacuum cover to evacuate the composite thermal insulation layer to a high vacuum. After reaching a high vacuum, the vacuum hole is sealed. The vacuum cover and the vacuum hole must have good airtightness and can maintain a high vacuum for a long time. In order to extend the service life of the thermal insulation layer, a certain amount of getter can also be added inside the composite thermal insulation layer.

[0063] The present invention also provides application of the composite thermal insulation layer in a vehicle-mounted low-temperature hydrogen storage tank.

[0064] The present invention also provides a vehicle-mounted cryogenic hydrogen storage tank, which comprises a hydrogen storage tank and the above-mentioned composite insulation layer.

[0065] According to the present invention, one side of the hollow microsphere layer in the composite thermal insulation layer is in contact with the outer wall of the hydrogen storage tank.

[0066] According to the present invention, the vehicle-mounted cryogenic hydrogen storage tank is sealed with a vacuum cover.

[0067] In the present invention, the low temperature, unless otherwise specified, refers to a temperature in the range of 20K-100K.

[0068] Beneficial effects of the present invention:

[0069] The present invention proposes a composite thermal insulation layer including a hollow microsphere layer and a multi-layer thermal insulation layer, a preparation method thereof, and an application in a vehicle-mounted low-temperature hydrogen storage tank. The composite thermal insulation layer is a composite of a hollow microsphere layer and a multi-layer thermal insulation layer, which brings out the advantages of the two thermal insulation layers. The details are as follows:

[0070] (1) In high vacuum, the point-contact hollow microspheres can extend the solid heat conduction path and minimize solid heat transfer. The multi-layer insulation layer can effectively block radiation heat transfer. The combination of the two to prepare a composite insulation layer has a more excellent insulation performance.

[0071] (2) In low vacuum, the hollow microspheres are not sensitive to the degree of vacuum, and the thermal conductivity only increases slightly under low vacuum. The multi-layer insulation layer is sensitive to the degree of vacuum, and the thermal conductivity increases significantly under low vacuum. The composite insulation layer formed by combining the two still has good insulation performance under low vacuum. The addition of the hollow microsphere layer greatly expands the vacuum range of the composite insulation layer, and extends the high vacuum of the composite insulation layer to high and low vacuum. When it is used in a vehicle-mounted cryogenic hydrogen storage tank, it can not only reduce the production cost of the vehicle-mounted cryogenic hydrogen storage tank, but also extend the service life of the vehicle-mounted cryogenic hydrogen storage tank. For example: the service life of a cryogenic hydrogen storage tank with only a multi-layer insulation layer is 4-5 years, while the service life of a cryogenic hydrogen storage tank containing the composite insulation layer of the present invention can be 8-10 years.

[0072] (3) At atmospheric pressure, the thermal conductivity of the hollow microspheres is similar to that of organic foam materials such as polyurethane foam, and the multi-layer insulation layer loses its insulation performance. The composite insulation layer composed of the two can ensure the insulation performance of the low-temperature hydrogen storage tank at atmospheric pressure. Therefore, the composite insulation layer composed of the hollow microsphere layer and the multi-layer insulation layer will achieve a better insulation effect in the range of high vacuum to low vacuum while ensuring the insulation effect at atmospheric pressure.

[0073] The following is an example of hollow glass microspheres:

[0074] Hollow glass microspheres are a new type of powder insulation material. They are composed of spherical thin-walled (0.5-2.0μm) glass particles with a diameter of 1-200μm. They are closed microspheres filled with gases such as CO2. Hollow glass microspheres have the advantages of low density, low thermal conductivity, high chemical stability, high mechanical strength, and good flame retardancy. They are a type of low-temperature insulation material with great application value. Hollow glass microspheres have excellent low-temperature insulation performance. In high vacuum (1×10 -3 Pa) liquid nitrogen-room temperature range (77K-300K), its thermal conductivity can be as low as 6.5×10 -4 W / m·K, much lower than polyurethane foam insulation material (1×10 - 2 W / m·K); in the atmospheric pressure (1atm) liquid nitrogen-room temperature range (77K-300K), its thermal conductivity is 2.1×10 -2W / m·K, which is equivalent to polyurethane foam insulation materials. The above data are all experimental data when hollow glass microsphere powder is kept warm in liquid nitrogen (77K). The thermal conductivity of hollow glass microspheres will further decrease with the decrease of temperature, that is, hollow glass microspheres have better insulation performance in liquid hydrogen (20K) and liquid helium (4.2K) temperature zones. Hollow glass microspheres are not sensitive to vacuum. In high vacuum, the thermal conductivity of hollow glass microspheres reaches the lowest value. In low vacuum, due to the slight increase in gas, the thermal conductivity of hollow glass microspheres only increases slightly. In the low vacuum (1Pa) liquid nitrogen-room temperature zone (77K-300K), its thermal conductivity can be as low as 8.5×10 -4 W / m·K, and the multi-layer insulation layer is more sensitive to the vacuum degree, especially when the vacuum degree is greater than 1Pa, the thermal conductivity of the multi-layer insulation layer is higher than that of the hollow glass microspheres. At atmospheric pressure, the thermal conductivity of the hollow microspheres is similar to that of polyurethane foam, and the multi-layer insulation layer loses its insulation performance. The composite insulation layer formed by combining the two can ensure the insulation performance of the low-temperature storage tank under atmospheric pressure. It can be seen that the composite insulation layer will have great advantages in high vacuum, low vacuum and atmospheric pressure when the hollow microsphere layer is combined with the multi-layer insulation layer. In addition, the composition of the hollow glass microspheres is similar to that of glass, and it is non-flammable and flame-retardant. It is not easy to deflate and has good vacuum retention ability, which is suitable for the application of low-temperature hydrogen storage tanks.

[0075] In summary, from high vacuum to low vacuum, the thermal insulation performance of the composite thermal insulation layer will be much better than that of the existing composite thermal insulation layer; at atmospheric pressure, the thermal insulation performance of the composite thermal insulation layer is equivalent to that of the existing composite thermal insulation layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 It is a schematic diagram of the structure of the composite insulation layer composed of the hollow microsphere layer and the uniform density multi-layer insulation material layer of Example 1.

[0077] Figure 2 It is a schematic structural diagram of a composite thermal insulation layer composed of a hollow microsphere layer and a variable density multi-layer thermal insulation material layer in Example 2.

[0078] Figure 3 It is a schematic diagram of the structure of the composite insulation layer composed of the hollow microsphere layer and the uniform density integrated insulation film of Example 3.

[0079] Figure 4 It is a schematic diagram of the structure of the composite insulation layer composed of the hollow microsphere layer and the variable density integrated insulation film of Example 4.

[0080] Figure numerals: 1. Cryogenic liquid, 2. Outer wall of storage tank, 3. Hollow microsphere powder, 4. Support body, 5. Spacer layer, 6. Reflection layer, 7. Integrated insulation film spacer, 8. Integrated insulation film reflective layer, 9. Uniform density multi-layer insulation material layer, 10. Variable density multi-layer insulation material layer, 11. Uniform density integrated insulation film, 12. Variable density integrated insulation film, 13. Vacuum cover, 14. External environment. DETAILED DESCRIPTION

[0081] The preparation method of the present invention will be described in further detail below in conjunction with specific examples. It should be understood that the following examples are only exemplary illustrations and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0082] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the reagents, materials, etc. used in the following examples, unless otherwise specified, can be obtained from commercial channels.

[0083] In the description of the present invention, it should be noted that the terms "first", "second", etc. are only used for descriptive purposes, and do not indicate or imply relative importance.

[0084] The hollow glass microspheres used in the following examples were prepared by referring to the method disclosed in Chinese patent document CN201210056295.5.

[0085] The foam used in the following examples is polyurethane foam, and the volume density of the polyurethane foam is 50 kg / m 3 .

[0086] Example 1

[0087] The thermal insulation structure of the composite thermal insulation layer of this embodiment is as follows Figure 1 As shown, the composite insulation layer of this embodiment is applied to a vehicle-mounted liquid hydrogen (20K) storage tank. The external environment temperature of the storage tank is 300K, and the temperature at both ends of the composite insulation layer is 20K-300K.

[0088] The on-board liquid hydrogen storage tank is a cylindrical storage tank with ellipsoidal heads at both ends. The inner tank of the storage tank stores liquid hydrogen, and the outer shell is a vacuum cover. A composite insulation layer is formed between the inner tank and the outer shell. There is a pipeline between the inner tank and the outer shell to introduce hydrogen into the combustion chamber of the automobile engine. In the composite insulation layer, a composite insulation layer of a 10mm thick hollow microsphere layer and 30 layers of uniform density multi-layer insulation layers is prepared. The preparation method is as follows:

[0089] 1. Preparation of hollow microsphere layer:

[0090] 1) Hollow microsphere powder is hollow glass microsphere, and the density of the hollow glass microsphere is 0.20g / cm 3 , compressive strength is 3.5MPa, particle size is 20-80μm, average particle size (D 50 ) is 36μm.

[0091] 2) Select a non-woven fabric with a pore size of 20 μm as the support body, and cut the non-woven fabric into a shape that fits the storage tank. For the cylindrical storage tank with ellipsoidal heads at both ends, the non-woven fabric support body can be divided into three parts: the upper ellipsoidal part, the middle cylindrical part and the lower ellipsoidal part.

[0092] 3) For the upper and lower ellipsoidal parts: combine two layers of non-woven fabrics and sew them into a fan shape. The upper and lower supports have 8 fans each, and each fan has a reserved filling port for hollow glass microspheres.

[0093] 4) For the middle cylindrical part: combine two layers of non-woven fabric and sew them into strips (similar to the strips of down jackets), so that the interval between two adjacent seams is 8 cm, and at the same time reserve a filling port for hollow glass microspheres.

[0094] 5) For the upper, middle and lower parts, a hollow glass microsphere filling unit is formed between the two seams and the two layers of non-woven fabric. The hollow glass microspheres are mixed with an activated carbon getter with a volume fraction of 2%, and filled into the space of each filling unit through the filling port. The thickness is controlled by the filling volume. The filling volume is 75%, forming a 10mm thick hollow microsphere layer, and the reserved filling port of each filling unit is sewn.

[0095] 6) The upper, middle and lower parts of the hollow microsphere layer are arranged on the outer wall of the on-board liquid hydrogen storage tank, and the three parts are sewn together to prepare the hollow microsphere layer.

[0096] 2. Preparation of 30 layers of uniform density multi-layer insulation layer:

[0097] The reflective layer of the uniform density multi-layer insulation is aluminized polyester film with a thickness of 0.02mm, and the spacer layer is polyester mesh with a thickness of 0.1mm.

[0098] 1) A layer of aluminized polyester film and a layer of polyester mesh is defined as a layer of uniform density multi-layer insulation material. Each layer of the multi-layer insulation material is cut into a size that can wrap the hollow microsphere layer.

[0099] 2) Arrange 10 layers of uniform density multi-layer insulation materials and sew them into a uniform density multi-layer unit, for a total of three uniform density multi-layer units.

[0100] 3) Three uniform density multi-layer units are sequentially arranged on the outside of the hollow microsphere layer, and are sewn and spliced, and the excess parts are cut off to form a uniform density multi-layer insulation material layer.

[0101] 3. The hollow microsphere layer and the multi-layer insulation layer are stacked together to obtain a composite insulation layer.

[0102] 4. Use a vacuum pump to connect the vacuum hole of the insulation layer on the vacuum cover to evacuate the composite insulation layer to a vacuum degree of 1×10 -3 Pa or more, after reaching high vacuum, seal the vacuum hole of the composite insulation layer. The vacuum cover and vacuum hole should have good air tightness and be able to maintain high vacuum for a long time.

[0103] The composite insulation layer in this embodiment is used to insulate the vehicle-mounted liquid hydrogen storage tank, and the temperature range at both ends of the composite insulation layer is 20K-300K. The heat flux density of the composite insulation layer prepared in the above embodiment 1 is tested, and the test results are shown in the following table, which lists the heat flux density of the composite insulation layer composed of the 10mm hollow glass microsphere layer and 30 layers of uniform density multilayer, the composite insulation layer composed of 10mm foam + 30 layers of uniform density multilayer, and the hollow glass microsphere insulation layer having the same thickness as the above composite insulation layer under high vacuum to low vacuum conditions.

[0104]

[0105] Judging from the above test results, the heat flux density of the liquid hydrogen storage tank using the composite insulation layer of the present application is the lowest and is suitable for high and low vacuum conditions. Specifically, under high vacuum conditions, the heat flux density increases by 35%; under low vacuum conditions, the heat flux density increases by 40%. Generally, the insulation layer of the liquid hydrogen storage tank has a high vacuum after preparation. However, it has a certain leakage rate. As the service life increases, generally 3-4 years, the high vacuum inside the insulation layer gradually becomes a low vacuum. When multiple layers of insulation are used, the thermal insulation effect becomes worse. However, when using the composite insulation layer of the present application, since the hollow glass microspheres are not sensitive to vacuum, they can still maintain good insulation performance. The composite insulation layer can have better performance under high vacuum to low vacuum. On the one hand, it can reduce the manufacturing cost of the storage tank; on the other hand, it can extend the service life of the storage tank to 8-10 years.

[0106] Example 2

[0107] The thermal insulation structure of the composite thermal insulation layer of this embodiment is as follows Figure 2 As shown, the composite thermal insulation layer of this embodiment is applied to a vehicle-mounted liquid hydrogen (40K) storage tank. The external environment temperature of the storage tank is 300K, and the temperature at both ends of the composite thermal insulation layer is 40K-300K.

[0108] The vehicle-mounted hydrogen storage tank is the same as in Example 1, except that in the composite insulation layer, a composite insulation layer of a 20 mm thick hollow microsphere insulation layer and 30 layers of variable density multi-layer insulation layers is prepared, and the preparation method is as follows:

[0109] 1. Preparation of hollow microsphere layer:

[0110] 1) Hollow microsphere powder is hollow glass microspheres, and the density of the hollow glass microspheres is 0.25 g / cm 3 , compressive strength is 5.2MPa, particle size is 20-80μm, average particle size (D 50 ) is 40μm.

[0111] 2) Other aspects are the same as in Example 1, except that a non-woven fabric with a pore size of 10 μm is selected as the support.

[0112] 3) The upper and lower ellipsoidal parts are the same as in Example 1, except that the upper and lower supporting bodies each have 4 sectors.

[0113] 4) The middle cylindrical part is the same as in Example 1, except that the interval between two adjacent seams is 6 cm.

[0114] 5) The upper, middle and lower parts are the same as in Example 1, except that the hollow glass microspheres are mixed with a molecular sieve getter with a volume fraction of 3%, and filled into the space of each filling unit through the filling port. The thickness is controlled by the filling volume. The filling volume is 80%, forming a 20 mm thick hollow microsphere layer, and the reserved filling port of each filling unit is sewn.

[0115] 6) Same as Example 1.

[0116] 2. Preparation of 30 layers of variable density multi-layer insulation layer:

[0117] The reflective layer of the variable density multi-layer insulation is an aluminized polyester film with a thickness of 0.02mm, and the spacer layer is a polyester mesh with a thickness of 0.15mm.

[0118] 1) One layer of aluminized polyester film and N layers of polyester mesh is defined as one layer of variable density multilayer thermal insulation material. 1-5 layers, each layer has 1 layer of aluminized polyester film and 4 layers of polyester mesh; 6-15 layers, each layer has 1 layer of aluminized polyester film and 2 layers of polyester mesh; 16-30 layers, each layer has 1 layer of aluminized polyester film and 1 layer of polyester mesh. Each layer of variable density multilayer thermal insulation material is cut into a size that can wrap the hollow microsphere layer.

[0119] 2) Arrange the variable-density multi-layer insulation materials of each density segment (1-5 layers, 6-15 layers, 16-30 layers) respectively, sew them into variable-density multi-layer units, and sew three variable-density multi-layer units in total.

[0120] 3) The three variable-density multi-layer units are sequentially arranged on the outside of the hollow microsphere layer, and are sewn and spliced, and the excess parts are cut off to form a variable-density multi-layer insulation material layer.

[0121] 3. Same as Example 1.

[0122] 4. Same as Example 1.

[0123] The heat flux density of the composite thermal insulation layer prepared in Example 2 was tested, and the test results are as follows:

[0124]

[0125] From the above test results, the heat flux density of the liquid hydrogen storage tank using the composite insulation layer of the present application is the lowest and is suitable for high and low vacuum conditions. Specifically, under high vacuum conditions, the heat flux density is increased by 30%; under low vacuum conditions, the heat flux density is increased by 44%.

[0126] Example 3

[0127] The thermal insulation structure of the composite thermal insulation layer of this embodiment is as follows Figure 3 As shown, the composite thermal insulation layer of this embodiment is applied to a vehicle-mounted liquid hydrogen (60K) storage tank. The external environment temperature of the storage tank is 300K, and the temperature at both ends of the composite thermal insulation layer is 60K-300K.

[0128] The vehicle-mounted hydrogen storage tank is the same as in Example 1, except that in the composite insulation layer, a composite insulation layer of a 30 mm thick hollow microsphere layer insulation layer and 30 layers of uniform density integrated insulation film is prepared, and the preparation method is as follows:

[0129] 1. Preparation of hollow microsphere layer:

[0130] 1) Hollow microsphere powder is hollow glass microsphere, and the density of the hollow glass microsphere is 0.16g / cm 3 , compressive strength is 1.8MPa, particle size is 20-100μm, average particle size (D 50 ) is 50μm.

[0131] 2) Other aspects are the same as in Example 1, except that a non-woven fabric with a pore size of 15 μm is selected as the support.

[0132] 3) In this embodiment, the thickness of the hollow microsphere layer is 30 mm. Referring to Embodiment 1 and Embodiment 2, hollow microsphere layers with a thickness of 10 mm and a thickness of 20 mm are respectively prepared, and then stacked to obtain a hollow microsphere layer with a thickness of 30 mm.

[0133] 4) The upper and lower ellipsoidal parts are the same as in Example 1, except that the upper and lower supporting bodies each have 6 sectors.

[0134] 5) The rest of the middle cylindrical part is the same as in Example 1, except that the interval between two adjacent seams is 4 cm.

[0135] 6) The other parts of the upper, middle and lower parts are the same as those in Example 1, except that the hollow glass microspheres are mixed with an activated carbon adsorbent with a volume fraction of 1%, and filled into the space of each filling unit through the filling port. The thickness is controlled by the filling volume. The filling volume is 90%, and hollow microsphere layers of 10 mm and 20 mm thick are formed respectively. The reserved filling port of each filling unit is sewn.

[0136] 7) The upper, middle and lower parts of the hollow microsphere layer are arranged on the outer wall of the on-board liquid hydrogen storage tank, and the three parts are sewn together to prepare the hollow microsphere layer.

[0137] 2. Preparation of 30 layers of uniform density integrated thermal insulation film:

[0138] The uniform density integrated heat insulation film comprises a reflective screen and a spacer. The reflective screen is an aluminum-plated polyester film with a thickness of 0.01 mm. The spacer is an epoxy resin-hollow glass microsphere composite material with a height of 0.2 mm.

[0139] 1) Cut each layer of uniform density integrated thermal insulation film into a size that can wrap the hollow microsphere layer.

[0140] 2) Arrange every 10 layers of uniform density integrated thermal insulation film, and sew the arranged uniform density integrated thermal insulation film into a unit, for a total of three units.

[0141] 3) Three uniform density integrated thermal insulation film units are sequentially arranged on the outside of the hollow microsphere layer, and are sewn and spliced, and the excess parts are cut off to form a uniform density integrated thermal insulation film layer.

[0142] 3. Same as Example 1.

[0143] 4. Same as Example 1.

[0144] The heat flux density of the composite thermal insulation layer prepared in the above Example 3 was tested, and the test results are as follows:

[0145]

[0146] From the above test results, the heat flux density of the liquid hydrogen storage tank using the composite insulation layer of the present application is the lowest and is suitable for high and low vacuum conditions. Specifically, under high vacuum conditions, the heat flux density is increased by 46%; under low vacuum conditions, the heat flux density is increased by 54%.

[0147] Example 4

[0148] The thermal insulation structure of the composite thermal insulation layer of this embodiment is as follows Figure 4 As shown, the composite thermal insulation layer of this embodiment is applied to a vehicle-mounted liquid hydrogen (80K) storage tank. The external environment temperature of the storage tank is 300K, and the temperature at both ends of the composite thermal insulation layer is 80K-300K.

[0149] The vehicle-mounted hydrogen storage tank is the same as Example 1, except that in the composite insulation layer, a composite insulation layer of a 40 mm thick hollow microsphere layer insulation layer and 30 layers of variable density integrated insulation film is prepared, and the preparation method is as follows:

[0150] 1. Preparation of hollow microsphere layer:

[0151] 1) Hollow microsphere powder is hollow glass microsphere, and the density of the hollow glass microsphere is 0.30g / cm 3 , compressive strength is 12MPa, particle size is 20-90μm, average particle size (D 50 ) is 45μm.

[0152] 2) Other aspects are the same as in Example 1, except that a non-woven fabric with a pore size of 10 μm is selected as the support.

[0153] 3) In this embodiment, the insulating layer of the hollow microsphere layer is 40 mm, and referring to Example 2, two hollow microsphere layers with a thickness of 20 mm are prepared respectively, and then stacked to obtain a hollow microsphere layer with a thickness of 40 mm.

[0154] 4) The upper and lower ellipsoidal parts are the same as in Example 1, except that the upper and lower supporting bodies each have 5 sectors.

[0155] 5) The rest of the middle cylindrical part is the same as in Example 1, except that the interval between two adjacent seams is 5 cm.

[0156] 6) The other parts of the upper, middle and lower parts are the same as those in Example 1, except that the hollow glass microspheres are mixed with a molecular sieve getter with a volume fraction of 4%, and filled into the space of each filling unit through the filling port. The thickness is controlled by the filling volume, and the filling volume is 95%. Two 20 mm thick hollow microsphere layers are formed, and the reserved filling port of each filling unit is sewn.

[0157] 7) The upper, middle and lower parts of the hollow microsphere layer are arranged on the outer wall of the storage tank, and the three parts are sewn together to prepare the hollow microsphere layer.

[0158] 2. Preparation of 30-layer variable density integrated thermal insulation film:

[0159] The reflective screen of the variable density integrated thermal insulation film is an aluminum-coated polyester film, and the spacer is an epoxy resin-hollow glass microsphere composite material. The thickness of the reflective screen is 0.01mm, of which the height of the spacer for 1-5 layers is 1.0mm; the height of the spacer for 6-15 layers is 0.6mm; the height of the spacer for 16-30 layers is 0.2mm.

[0160] 1) Cut each layer of variable density integrated thermal insulation film into a size that can wrap the hollow microsphere layer.

[0161] 2) Arrange each variable density integrated thermal insulation film segment and sew the arranged variable density integrated thermal insulation films into one unit, for a total of three units.

[0162] 3) Arrange three variable density integrated thermal insulation film units in sequence on the outside of the hollow microsphere layer, sew and splice them, cut off the excess parts, and form a variable density integrated thermal insulation film layer.

[0163] 3. The hollow microsphere layer and the variable density integrated thermal insulation film layer are superimposed together to obtain a composite thermal insulation layer.

[0164] 4. Same as Example 1.

[0165] The heat flux density of the composite thermal insulation layer prepared in Example 4 was tested, and the test results are as follows:

[0166]

[0167]

[0168] From the above test results, the heat flux density of the liquid hydrogen storage tank using the composite insulation layer of the present application is the lowest and is suitable for high and low vacuum conditions. Specifically, under high vacuum conditions, the heat flux density is increased by 30%; under low vacuum conditions, the heat flux density is increased by 50%.

[0169] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A composite thermal insulation layer, comprising a hollow microsphere layer and a multi-layer thermal insulation layer; The hollow microsphere layer comprises a support and hollow microsphere powder; the hollow microsphere powder is filled inside the support to form a hollow microsphere layer; The multi-layer insulation layer comprises at least one of a uniform density multi-layer insulation material layer, a variable density multi-layer insulation material layer, a uniform density integrated insulation film, and a variable density integrated insulation film; The thickness of the hollow microsphere layer is 5-50 mm; In the hollow microsphere layer, the filling volume of the hollow microsphere powder is 75%-95%; The uniform density multilayer heat insulating material layer comprises a reflective layer and a spacer layer; the reflective layer and the spacer layer are alternately stacked in a ratio of 1:1; The variable density multilayer thermal insulation material layer comprises a reflective layer and a spacer layer; the reflective layer and the spacer layer are alternately stacked in a ratio of 1:N, where N is the same or different, is a positive integer and 1≤N≤10; The thickness of each reflective layer is 0.01-0.03 mm; the thickness of each spacer layer is 0.1-0.3 mm; The reflective layer is selected from aluminum foil or aluminum-plated polyester film; the spacer layer is selected from polyester mesh, nylon mesh or glass fiber paper; The uniform density integrated thermal insulation film comprises a reflective screen and a spacer attached to the reflective screen, and the uniform density integrated thermal insulation film is composed of a plurality of integrated thermal insulation films with the same spacer height; the variable density integrated thermal insulation film comprises a reflective screen and a spacer attached to the reflective screen, and the variable density integrated thermal insulation film is composed of a plurality of integrated thermal insulation films with different spacer heights; The thickness of the reflective screen is 0.01-0.03 mm, and the reflective screen is selected from one of aluminum foil, gold foil, silver foil, copper foil, nickel foil, and metal-plated polymer film; The thickness of the spacer is 0.01-10 mm, and the spacer comprises hollow microspheres and an adhesive.

2. The composite thermal insulation layer according to claim 1, wherein: The hollow microsphere powder includes a mixture of one or more of hollow glass microspheres, hollow ceramic microspheres, polymer hollow microspheres, and silicon oxide hollow microspheres.

3. The composite thermal insulation layer according to claim 1, wherein: A getter is also added to the hollow microsphere powder; the amount of the getter is 0-5 vol% of the volume of the hollow microsphere powder; the getter is selected from activated carbon or molecular sieve.

4. The composite thermal insulation layer according to claim 1, wherein: The uniform density multi-layer thermal insulation material layer includes a thermal insulation material unit layer, and the thermal insulation material unit layer includes a reflective layer and a spacer layer; the reflective layer and the spacer layer are alternately stacked; the reflective layer and the spacer layer are alternately stacked in a 1:1 ratio and sewn to form a thermal insulation material unit layer, and a plurality of thermal insulation material unit layers are stacked to form a uniform density multi-layer thermal insulation material layer.

5. The composite thermal insulation layer according to claim 1, wherein: The variable density multilayer thermal insulation material layer includes a thermal insulation material unit layer, and the thermal insulation material unit layer includes a reflective layer and a spacer layer; the reflective layer and the spacer layer are alternately stacked; the reflective layer and the spacer layer are alternately stacked and sewn in a ratio of 1:N to form a thermal insulation material unit layer, and several thermal insulation material unit layers are stacked to form a variable density multilayer thermal insulation material layer, N is the same or different, is a positive integer and 1≤N≤10.

6. The composite thermal insulation layer according to claim 1, wherein: The total number of layers of the uniform density multi-layer thermal insulation material layer is 10-100 layers.

7. The composite thermal insulation layer according to claim 1, wherein: The total number of layers of the variable-density multi-layer thermal insulation material layer is 10-100 layers.

8. The composite thermal insulation layer according to claim 1, wherein: The adhesive is an organic adhesive or an inorganic adhesive.

9. The composite thermal insulation layer according to any one of claims 1 to 8, wherein: The composite thermal insulation layer further comprises a vacuum cover enclosing the composite thermal insulation layer.

10. The composite thermal insulation layer according to claim 9, wherein: The vacuum cover has a vacuum hole.

11. The composite thermal insulation layer according to claim 9, wherein: The vacuum degree inside the vacuum cover is 1×10 -3 Pa or above.

12. The method for preparing the composite thermal insulation layer according to any one of claims 1 to 11, comprising the following steps: 1) Filling the hollow microsphere powder inside the support to prepare a hollow microsphere layer; 2) preparing a multi-layer thermal insulation layer; the multi-layer thermal insulation layer is at least one of a uniform density multi-layer thermal insulation layer, a variable density multi-layer thermal insulation layer, a uniform density integrated thermal insulation film, and a variable density integrated thermal insulation film; 3) Arranging the hollow microsphere layer and the multi-layer thermal insulation layer together to obtain a composite thermal insulation layer.

13. The preparation method according to claim 12, wherein: The composite thermal insulation layer forms a vacuum environment.

14. The preparation method according to claim 12, wherein: The vacuum degree is 1×10 -3 Pa or above.

15. The preparation method according to claim 12, wherein: The composite insulation layer is sealed with a vacuum cover.

16. Use of the composite thermal insulation layer according to any one of claims 1 to 11 in a vehicle-mounted cryogenic hydrogen storage tank.

17. A vehicle-mounted cryogenic hydrogen storage tank, comprising a hydrogen storage tank and the composite insulation layer according to any one of claims 1 to 11.

18. The vehicle-mounted cryogenic hydrogen storage tank according to claim 17, wherein: One side of the hollow microsphere layer in the composite thermal insulation layer is in contact with the outer wall of the hydrogen storage tank.

19. The vehicle-mounted cryogenic hydrogen storage tank according to claim 17, wherein: The on-board cryogenic hydrogen storage tank is sealed with a vacuum cover.

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