Adsorptive heat storage material with multi-stage hierarchical pore structure and method for producing same

Abstract

The application discloses an adsorption heat storage material with a multi-stage gradient pore structure and a preparation method thereof. The material combines a metal foam substrate with a multi-stage pore structure, significantly improving the heat storage and release efficiency. Specifically, the metal foam substrate is composed of multiple metal foam layers with different porosities, and the porosity increases step by step along the heat source direction, thereby effectively reducing the thermal resistance and accelerating the diffusion of the adsorbate. The adsorbent coating is formed by coating an adsorbent material mixture containing a template agent, drying and calcining, forming a multi-stage pore structure including macropores, mesopores and micropores, improving the adsorption diffusion speed and adsorption capacity. The material not only improves the heat storage and release capacity, but also optimizes the diffusion rate of the adsorbate. The preparation method reduces the production cost through simple processes such as splicing of the metal foam layer and adsorbent coating, and the preparation process is efficient and controllable, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of efficient energy storage, and relates to the preparation of adsorption heat storage materials, more particularly to an adsorption heat storage material with a multi-stage hierarchical pore structure and a preparation method thereof. The material is prepared by combining metal foams with different porosities and coating a multi-stage porous adsorbent coating on the surface of the metal foams, aiming to improve the efficiency of heat storage and release and solve the problem of poor heat and mass transfer performance of traditional adsorption heat storage materials. BACKGROUND

[0002] Due to the extensive use of traditional fossil energy, energy and environmental problems are becoming increasingly serious, and energy saving and emission reduction and the improvement of renewable energy utilization are extremely urgent. In energy utilization, heat supply accounts for a high proportion of terminal energy consumption, and therefore it is extremely necessary to realize clean and low-carbon heat supply technology. Through efficient heat storage technology, as much industrial waste heat and renewable energy as possible can be collected, which is expected to solve the problem of temporal and spatial mismatch of heat supply and demand and provide clean heat for industry and buildings.

[0003] Adsorption thermal energy storage (ATES) is a technology that stores and releases heat through the reversible adsorption and desorption process of solid porous adsorbents and working fluids such as water vapor and ammonia. It has the advantages of high heat storage density and low heat loss, and has broad application prospects. This technology can efficiently collect industrial waste heat and renewable energy (such as solar energy and geothermal energy), realize temporal and spatial transfer of heat energy, and has potential value in the fields of building heating, industrial waste heat recovery and mobile energy systems.

[0004] However, although adsorption heat storage has great potential, it also has many problems. For example, the solid porous adsorbents commonly used in adsorption heat storage (such as zeolites, silica gels, molecular sieves and alumina) usually have low thermal conductivity, only 0.1-0.3 W / K·m. This low thermal conductivity results in slow heat transfer in the heat storage material, thus prolonging the heat storage and release time, which greatly limits its application in fast heat transfer scenarios. In addition, the pores in the existing porous adsorbents are mostly nanoscale micropores with a pore size usually less than 2 nanometers. Although this structure has the advantage of providing a large specific surface area, the adsorption and diffusion speed of the working fluid in the internal pores is slow, which limits the migration rate of the working fluid in the adsorbent, and also results in slow heat storage and release, making it difficult to apply to fast heat storage and release scenarios.

[0005] Currently, the improvement of adsorbent structure is usually achieved by adding high thermal conductivity materials (such as graphene, metal particles, etc.) in the adsorbent, or pressing the powder / particle adsorbent into a sheet, etc. to improve its thermal conductivity and adsorption speed. However, since the above methods only improve the local thermal conductivity, and do not essentially change the pore size of the adsorbent, the internal diffusion resistance of the adsorbent is not reduced, and the thermal resistance between the adsorbent particles, the adsorbent and the high thermal conductivity material, and the adsorbent and the heating source is still huge. Moreover, the adsorption performance may be partially lost during the sheet pressing process, which affects its actual effect. Therefore, the existing improved adsorbent cannot meet the application scenarios of fast heat storage, and there is still a large room for improvement. In addition, the preparation process of traditional adsorbents usually requires complex processes and high costs. In order to optimize the performance of the adsorbent, it is often necessary to introduce various additives (such as binders, template agents, etc.) and go through a multi-step complex processing process (such as high-temperature calcination, ultrasonic dispersion, etc.). Although this method can improve the performance of the adsorbent to some extent, the complexity of the preparation process and the increase in cost limit the feasibility of its large-scale promotion.

[0006] In summary, the adsorption heat storage material has significant limitations in heat and mass transfer performance, structure design, and preparation process, etc., which limits its application in the field of fast heat energy storage and release. How to effectively improve the thermal conductivity and adsorption performance of the adsorption heat storage material, optimize its pore structure design, and simplify the preparation process and reduce the cost has become a technical problem to be solved. These technical improvements are of great significance for promoting the application of adsorption heat storage technology in the field of clean energy and industrial energy saving. SUMMARY

[0007] (I) Invention purposes

[0008] In view of the defects and deficiencies of the prior art, such as poor thermal conductivity of the adsorption heat storage material, limited diffusion of the adsorbate, slow heat storage and release speed, etc., in order to solve at least one of the above and other technical problems in the prior art, the purpose of the present application is to provide an adsorption heat storage material with multi-level hierarchical pores for adsorption heat storage and a preparation method thereof. By introducing metal foams with different porosities into the adsorption heat storage material, a multi-level hierarchical pore structure composed of metal foams with different porosities is adopted, and an adsorbent coating containing macropores, mesopores and micropores is coated, the pore structure of the material is optimized, the internal thermal resistance of the material is significantly reduced, the diffusion speed of the adsorbate is improved, and the heat energy storage and release rate is significantly improved. By reasonably designing the porosity gradient of the metal foam, the thermal conductivity of the material is enhanced, and by coating the multi-level pore coating, the adsorption and desorption efficiency of the adsorbent is improved, the heat energy storage and release rate is greatly improved, thereby realizing the wide application in the application scenario of fast heat energy storage and release. This technical solution not only improves the performance of the adsorption heat storage material, but also simplifies the preparation process of the material, and has good practical application prospect.

[0009] (II) Technical Solution

[0010] To achieve the object of the present application and solve the technical problems, the present application adopts the following technical solution:

[0011] The first object of the present application is to provide an adsorption heat storage material with a multi-stage hierarchical pore structure for efficient heat storage and rapid release, especially providing excellent performance in rapid heat storage and release application scenarios, comprising at least a metal foam substrate and an adsorbent coating, wherein:

[0012] The metal foam substrate is used for conducting heat and providing structural support, and comprises at least multiple layers of metal foam with different porosities, the thermal conductivity of the metal foam material in each layer is not less than 0.5 W / m·K, and the porosity of the multiple layers of metal foam increases step by step along the direction of the heat source, the porosity of the metal foam layer closest to the heat source is the smallest, which is controlled within the range of 30%~50% to optimize the heat conduction efficiency and reduce the thermal resistance, and the porosity of the metal foam layer farthest from the heat source is the largest, which is controlled within the range of 60%~85% to increase the diffusion rate of the adsorbate and enhance the adsorption capacity, the porosity of the metal foam material in each layer is controlled by precisely adjusting the manufacturing process of the metal foam to ensure that the heat conduction and diffusion between different layers are balanced, and the adjacent metal foam layers are connected by welding at the interface to form a stable multi-layer structure, ensuring the mechanical stability and thermal conductivity of the metal foam substrate under high temperature and multiple thermal cycles;

[0013] The adsorbent coating is used for adsorbing and releasing the working medium and uniformly coated on the surface of the metal foam substrate, and the overall thickness is controlled within the range of 100~1000 μm to ensure that the coating has good adsorption capacity and heat transfer performance, and the adsorbent coating is formed into a multi-stage pore structure composed of a large number of large pores, mesopores and micropores to facilitate the acceleration of the diffusion rate of the adsorbate and improve the adsorption and desorption efficiency, wherein: the pore size range of the large pores is controlled within 50~200 nm to promote the rapid diffusion of the working medium and the rapid transfer of heat, the pore size range of the mesopores is controlled within 2~50 nm to provide a larger specific surface area and enhance the adsorption capacity, and the pore size of the micropores is controlled to be less than 2 nm to improve the adsorption density and storage capacity of the adsorbate;

[0014] The combination of the metal foam substrate and the adsorbent coating enables the prepared adsorption heat storage material to have high efficient heat conduction and adsorption performance during the heat storage and release process, effectively reduces the thermal resistance through the hierarchical pore structure of the metal foam substrate, and at the same time improves the diffusion rate of the adsorbate through the multi-stage pore structure in the adsorbent coating, thereby improving the heat storage and release efficiency of the adsorption heat storage material and meeting the application requirements of rapid heat storage and release.

[0015] The second inventive objective of the present application is to provide a preparation method of the adsorptive heat storage material with the multi-stage hierarchical pore structure, which comprises at least the following steps when implemented:

[0016] SS1. Preparation of the metal foam substrate

[0017] Two to five metal foam layers with different porosities are selected, the thermal conductivity of the metal foam material in each metal foam layer is not less than 0.5 W / m·K, and the selected metal foam layers are arranged from small to large porosity from bottom to top to form a hierarchical pore structure, wherein the porosity of the lowermost metal foam layer is the smallest, and the porosity is controlled within the range of 30% to 50%, the porosity of the uppermost metal foam layer is the largest, and the porosity is controlled within the range of 60% to 85%, and the adjacent metal foam layers are connected by welding at the interface joint to form a stable multi-layer structure;

[0018] SS2. Cleaning and drying of the metal foam substrate

[0019] The metal foam substrate prepared in step SS1 is cleaned by using organic solvents and deionized water combined with ultrasonic cleaning or acid pickling treatment to wash off impurities, oil stains and oxides attached to the surface of the metal foam substrate, and then dried at a temperature of 60 to 80°C for 2 to 10 hours to ensure that the surface of the metal foam substrate is free of moisture and organic residues, obtaining a clean and dry metal foam substrate for standby use;

[0020] SS3. Preparation of the adsorbent coating slurry

[0021] The adsorbent, deionized water, binder and pore former are mixed in appropriate proportions to form a slurry, and the proportioning of the slurry is optimized according to experimental data to ensure uniform distribution of the adsorbent particles and moderate bonding force between the binder and the adsorbent, wherein the adsorbent is selected from at least one of zeolite, silica gel, alumina, and molecular sieve, the binder is selected from at least one of silica sol, aluminum sol, titanium sol, organic silicone resin, yellow dextrin, and sesbania powder, and the pore former is selected from at least one of cellulose, nano-graphite sheet, ammonium bicarbonate, and acrylic resin, and the slurry is ground in a glue mill for 1 to 3 hours after mixing to homogenize the slurry composition and improve the fineness of the particles, ensuring that the average particle size of the slurry is controlled within the range of 30 to 50 nm;

[0022] SS4. Coating of the adsorbent coating

[0023] The prepared slurry is uniformly coated on the surface of the metal foam substrate obtained in step SS2 by dip coating or spray coating, wherein when the dip coating process is used, the metal foam substrate is immersed in the slurry to ensure uniform coating of the coating, and when the spray coating is used, a special spray gun is used to spray the slurry to the surface of the metal foam substrate to ensure uniform thickness of the coating, and after drying and curing at 70-90 ℃, a coating is formed, and one or more coatings are coated until the desired coating thickness is reached, and the overall thickness of the coating is controlled to be 100-1000 μm;

[0024] SS5. Calcination treatment of adsorbent coating

[0025] The metal foam substrate coated with the adsorbent coating is calcined at a temperature of 500-600 ℃ for 1-6 hours, and the organic solvent, moisture and pore-forming agent in the adsorbent coating are removed by calcination to form a multi-level pore structure containing a large number of micropores, mesopores and macropores in the adsorbent coating, thereby obtaining an adsorption heat storage material with a multi-level hierarchical pore structure;

[0026] SS6. Performance test (optional step) of adsorption heat storage material

[0027] The prepared adsorption heat storage material is subjected to performance tests, including determination of the thermal conductivity, adsorption capacity and adsorption rate of the material, wherein the thermal conductivity test uses the transient plane heat source method and the test temperature is 30 ℃, and the adsorption performance test is carried out under standard test conditions of 1.27 kPa water vapor pressure and 30 ℃ temperature, and the change in adsorption amount within 60 minutes is recorded to ensure that the water vapor adsorption amount of the prepared adsorption heat storage material is not less than 0.35 g / g, the average adsorption speed is not less than 1.2 g / min, and the thermal conductivity is not less than 0.85 W / m·K.

[0028] (Three) Technical effects

[0029] Compared with the prior art, the adsorption heat storage material with a multi-level hierarchical pore structure and the preparation method thereof have the following beneficial and significant technical effects:

[0030] (1) The preparation method of the adsorption heat storage material with a multi-level hierarchical pore structure provided by the present application can prepare an adsorption heat storage material with good adsorption performance through innovative design and production process, which can significantly improve the heat and mass transfer performance during heat storage process, greatly improve the heat energy storage and release speed, and reduce the preparation cost, and has high efficient and stable heat energy conversion capacity.

[0031] (2) The adsorption heat storage material with stepped porosity provided by the present application can increase the adsorption speed by arranging the metal foams with porosity gradually increasing along the direction of heat source, while reducing the thermal resistance, so that the adsorbent can quickly reach the bottom along the stepped porosity. In particular, the metal foam layer with smaller porosity in the lowermost layer ensures the rapid heat transfer to the farther layer through lower thermal resistance, and the upper metal foam layer with larger porosity provides more space for the diffusion of the adsorbent, thereby significantly improving the efficiency and speed of heat storage and release. The design not only optimizes the heat conduction performance, but also increases the transmission path of the adsorbent, effectively shortening the time of heat storage and release.

[0032] (3) The adsorption heat storage material with multi-level porosity provided by the present application can obtain a multi-level porosity coating containing a large number of large pores, mesopores and micropores on the surface of the metal foam through coating the adsorbent mixture containing a template agent, drying and calcining, which greatly improves the specific surface area and the adsorption and diffusion speed of the working medium compared with the simple microporous adsorbent. The large pores and mesopores help to accelerate the entry and desorption process of the adsorbent, and the micropores improve the adsorption density and storage capacity. Through the design of the multi-level porosity structure, the diffusion rate of the adsorbent is significantly improved, thereby enhancing the adsorption capacity and heat storage capacity of the material.

[0033] (4) The preparation method of the adsorption heat storage material with multi-level stepped porosity provided by the present application can efficiently prepare the adsorption heat storage material with fast heat storage and release capacity by splicing metal foam layers with different porosities and coating, drying and calcining the adsorbent. In addition, through the calcination treatment, the organic solvent and water in the adsorbent coating are effectively removed, and the pore-forming agent in the coating is also treated, forming a multi-level porosity network with high strength structure. The multi-level porosity structure not only enhances the adsorption performance of the adsorbent, but also improves the thermal stability of the material. The combination between the metal foam substrate and the coating is firm, which can maintain stability during high temperature and multiple heat cycles, avoiding the peeling or performance degradation of the coating. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is the arrangement diagram of the multi-layer metal foam layer in the adsorption heat storage material of the present application;

[0035] Figure 2 is the schematic diagram of the adsorbent coating with multi-level porosity in the adsorption heat storage material of the present application;

[0036] Figure 3 is the preparation flow chart of the adsorption heat storage material with multi-level stepped porosity of the present application. DETAILED DESCRIPTION

[0037] For the purposes of making the objects, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below with reference to the drawings in the embodiments of the present application. The described embodiments are part of the embodiments of the present application, rather than all the embodiments. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0038] The present application aims to provide an adsorption heat storage material with multi-stage hierarchical porosity applied to adsorption heat storage and a preparation method thereof. By introducing metal foams with different porosities into the adsorption heat storage material, using a multi-stage hierarchical porosity structure composed of metal foams with different porosities, and by coating an adsorbent coating containing macropores, mesopores and micropores, the porosity structure of the material is optimized, the internal thermal resistance of the material is significantly reduced, and the diffusion speed of the adsorbate is improved, significantly improving the heat energy storage and release rate.

[0039] Embodiment 1

[0040] As a specific example, as shown in Figure 1 , 2 , the adsorption heat storage material with multi-stage hierarchical porosity provided by the present application includes a metal foam substrate 10 and an adsorbent coating 20, wherein the metal foam substrate 10 is used to conduct heat energy and provide structural support, as shown in Figure 1 , including multiple layers (for example, 2-5 layers, and 3 layers are shown in the figure) of metal foam layers 11-13 with different porosities, the thermal conductivity of the metal foam material in each layer is not less than 0.5 W / m·K, and the porosity of the multiple layers of metal foam layers 11-13 increases step by step along the direction of the heat source, the porosity of the metal foam layer 13 closest to the heat source is the smallest, and the porosity is controlled within the range of 30%-50% to optimize the conduction efficiency of heat energy and reduce the thermal resistance, the porosity of the metal foam layer 11 farthest from the heat source is the largest, and the porosity is controlled within the range of 60%-85% to improve the diffusion rate of the adsorbate and enhance the adsorption capacity, the porosity range of the intermediate metal foam layer 12 is in the transition range, the porosity of the metal foam material in each layer is controlled by precisely adjusting the manufacturing process of the metal foam to ensure that the conduction and diffusion of heat energy between different layers are balanced, and the adjacent metal foam layers are connected by welding at the interface to form a stable multi-layer structure, ensuring the mechanical stability and thermal conductivity of the metal foam substrate under high temperature and multiple thermal cycles.

[0041] As preferred, the metal foam substrate 10 is composed of 2-5 metal foam layers with different porosities, the metal foam material in each metal foam layer can be one or more combinations of foam copper, foam aluminum, foam nickel, foam iron, foam titanium, the porosity of each metal foam layer is precisely controlled by adjusting the manufacturing process of the metal foam material, including adjusting the type and adding amount of foaming agent, controlling the melting temperature of the metal foam and the foam generation time, so as to realize the porosity control of each layer of metal foam material and ensure that the joint of different porosity metal foam layers has good mechanical stability and thermal conductivity.

[0042] In addition, the porosity difference in each layer of metal foam material of the metal foam substrate 10 is realized by controlling the gas release rate and cooling rate during the forming process of the foam metal, and specifically by accelerating the gas release rate to increase the foam porosity, and by slow cooling to reduce the porosity of the foam metal, and finally achieving a porosity gradient gradually increasing along the direction of the heat source.

[0043] As preferred, the multi-layer structure of the metal foam substrate 10 adopts a step-by-step welding or brazing process, so that the combination between each layer of metal foam material is not only physically stable, but also has good continuity in thermal conduction, so that the heat transfer in the metal foam substrate is more efficient, effectively reducing the heat loss and improving the thermal response speed of the material.

[0044] As shown in Figure 2 The adsorbent coating 20 is used to adsorb and release the heat energy working substance and is uniformly coated on the surface of the metal foam substrate, and the overall thickness is controlled in the range of 100-1000 μm to ensure that the coating has good adsorption capacity and heat transfer performance, and the adsorbent coating 20 is formed in a multi-level porosity structure composed of a large number of large pores, mesopores and micropores to facilitate the acceleration of the diffusion rate of the adsorbate and improve the adsorption and desorption efficiency, wherein the pore size range of the large pores is controlled in the range of 50-200 nm to facilitate the rapid diffusion of the working substance and the rapid transfer of heat, the pore size range of the mesopores is controlled in the range of 2-50 nm to provide a larger specific surface area and enhance the adsorption capacity, and the pore size of the micropores is controlled to be less than 2 nm to improve the adsorption density and storage capacity of the adsorbate.

[0045] As preferred, the adsorbent coating 20 is composed of an adsorbent, a binder and a pore former, wherein the adsorbent can be one or more combinations of zeolite, silica gel, alumina, molecular sieve, the binder is selected from one or more combinations of silica sol, aluminum sol, titanium sol, organic silicone resin, yellow dextrin, sesbania powder, the pore former is selected from one or more combinations of cellulose, nano-graphite sheet, ammonium bicarbonate, acrylic resin, and the components are reasonably matched to ensure the adsorption performance and structural stability of the coating.

[0046] The adsorption heat storage material with multi-stage stepped porosity provided by the present application has high efficient heat conduction and adsorption performance in the heat storage and release process, effectively reduces the thermal resistance through the stepped porosity structure of the metal foam substrate, and improves the diffusion rate of the adsorbate through the multi-stage porosity structure in the adsorbent coating, thereby improving the heat energy storage and release efficiency of the adsorption heat storage material and meeting the application requirement of rapid heat energy storage and release.

[0047] Embodiment 2

[0048] Based on the above embodiment 1, the present embodiment 2 further details the preparation method of the adsorption heat storage material with multi-stage stepped porosity of the present application, as shown in the following formula: Figure 3 The method includes the following steps when implemented:

[0049] SS1. Preparation of metal foam substrate

[0050] Select 2-5 metal foam layers with different porosities, and the thermal conductivity of the metal foam material in each metal foam layer is not less than 0.5 W / m·K. Arrange the selected metal foam layers from small to large porosity to form a stepped porosity structure, wherein the porosity of the lowermost metal foam layer is the smallest, and the porosity is controlled within the range of 30%-50%, and the porosity of the uppermost metal foam layer is the largest, and the porosity is controlled within the range of 60%-85%. The interface between adjacent metal foam layers is connected by welding to form a stable multi-layer structure.

[0051] As a preferred, when forming each metal foam layer, the selected metal material is heated to a molten state, the foaming process of the molten metal, the addition amount of the foaming agent and the foam cooling speed are controlled to form metal foams with different porosities. The thickness of each metal foam layer can be adjusted according to the actual application requirement and is controlled within the range of 10-50 mm, and the porosity difference between adjacent metal foam layers is controlled within the range of 5%-15% to achieve the best heat conduction and material transmission effect.

[0052] SS2. Cleaning and drying of metal foam substrate

[0053] The metal foam substrate prepared in step SS1 is cleaned by using organic solvents and deionized water combined with ultrasonic cleaning or acid pickling treatment to wash off impurities, oil stains and oxides attached to the surface of the metal foam substrate. Subsequently, drying treatment is performed at a temperature of 60-80°C for 2-10 hours to ensure that the surface of the metal foam substrate is free of water and organic residues, and a clean and dry metal foam substrate is obtained for standby use.

[0054] As preferred, the organic solvent is acetone, and the cleaning process comprises immersing the metal foam substrate into acetone and deionized water for 3 times respectively, each time for no less than 10 minutes, and auxiliary ultrasonic cleaning is used to improve the cleaning effect; the drying process is performed in a vacuum drying oven under the conditions of 60-80 °C and a pressure no higher than 0.1 MPa, so as to ensure that the water and organic solvent residues in the internal pores of the metal foam substrate are fully removed, and a clean substrate is provided for the subsequent coating.

[0055] SS3. Preparation of adsorbent coating slurry

[0056] The adsorbent, deionized water, binder and pore-forming agent are mixed into a slurry in appropriate proportions, and the proportioning of the slurry is determined according to experimental data to ensure uniform distribution of the adsorbent particles and moderate binding force between the binder and the adsorbent, wherein the adsorbent is selected from at least one of zeolite, silica gel, alumina and molecular sieve, the binder is selected from at least one of silica sol, aluminum sol, titanium sol, organic silicone resin, yellow dextrin and sesbania powder, and the pore-forming agent is selected from at least one of cellulose, nano-graphite sheet, ammonium bicarbonate and acrylic resin; and the slurry is ground in a colloid mill for 1-3 hours after mixing to homogenize the slurry components and improve the fineness of the particles, so as to ensure that the average particle size of the slurry is controlled within the range of 30-50 nm;

[0057] As preferred, the mass ratio of the adsorbent, deionized water, binder and pore-forming agent is 1:1:0.1-0.2:0.02-0.1, wherein the adsorbent is 13X molecular sieve, the binder is silica sol, and the pore-forming agent is cellulose; in the slurry preparation process, the adsorbent is first mixed with deionized water and stirred for 30 minutes, then the binder is added and stirred for another 30 minutes, and finally the pore-forming agent is added and stirred uniformly; the slurry is ground at a speed of 300-500 rpm for 2 hours after mixing to ensure the uniformity and stability of the slurry.

[0058] SS4. Coating of adsorbent coating

[0059] The prepared slurry is uniformly coated on the surface of the metal foam substrate obtained in step SS2 by dip coating or spray coating, wherein when the dip coating process is used, the metal foam substrate is immersed in the slurry to ensure uniform coating of the coating, and when the spray coating is used, a special spray gun is used to spray the slurry onto the surface of the metal foam substrate to ensure uniform thickness of the coating, and the coating is formed after drying and curing at 70-90 °C, and the coating is coated once or more times until the desired coating thickness is reached, and the overall thickness of the coating is controlled within the range of 100-1000 μm.

[0060] As preferred, the coating is performed by spraying, using a pneumatic spray gun, with a spraying pressure controlled at 0.2-0.3 MPa and a spraying distance maintained at 15-20 cm; after each spraying, drying is performed at 80°C for 30 minutes, and the spraying is repeated for 3-5 times to achieve a coating with a desired thickness; after the last spraying, pre-curing is performed at 85°C for 2 hours, followed by post-curing at 120°C for 1 hour to ensure the bonding strength between the coating and the metal foam substrate; the final thickness of the coating is controlled at 300±50 μm.

[0061] SS5. Calcination treatment of the adsorbent coating

[0062] The metal foam substrate coated with the adsorbent coating is subjected to a calcination treatment at a temperature of 500-600°C for 1-6 hours, so as to remove the organic solvents, moisture and pore-forming agent in the adsorbent coating through the calcination treatment, to form a multi-level pore structure containing a large number of micropores, mesopores and macropores in the adsorbent coating, thereby obtaining an adsorptive heat storage material with a multi-level hierarchical pore structure.

[0063] As preferred, the calcination process is performed in a programmed temperature mode, with a temperature rising rate of 2°C / min from room temperature to 300°C and a holding time of 1 hour to remove residual moisture, then to 400°C and a holding time of 1 hour to decompose organic matter, and finally to 550°C and a holding time of 3 hours to completely remove the pore-forming agent and form a stable multi-level pore structure; the cooling process is performed by natural cooling, with a cooling rate not exceeding 5°C / min to avoid cracking or peeling of the coating due to thermal stress.

[0064] SS6. Performance test of the adsorptive heat storage material (preferred steps)

[0065] The prepared adsorptive heat storage material is subjected to performance tests, including determination of the thermal conductivity, adsorption capacity and adsorption rate of the material, wherein the thermal conductivity test is performed by the transient plane source method with a test temperature of 30°C, and the adsorption performance test is performed under standard test conditions of 1.27 kPa water vapor pressure and 30°C temperature, and the change in the adsorption amount within 60 minutes is recorded to ensure that the water vapor adsorption amount of the prepared adsorptive heat storage material is not less than 0.35 g / g, the average adsorption speed is not less than 1.2 g / min, and the thermal conductivity is not less than 0.85 W / m·K, to meet the actual application requirements.

[0066] Technical effect verification:

[0067] Example: Based on the preparation method shown in the above Example 2, three kinds of foamed copper with porosities of 50%, 75% and 95% (all with a size of 50*50*5mm) are arranged from small to large porosity from bottom to top, connected at the joint by welding, cleaned with acetone and deionized water for 3 times respectively, and then dried at 80℃ for 6 hours. 13X molecular sieve adsorbent, deionized water, silica sol, cellulose are mixed in a mass ratio of 1:1:0.2:0.1, and ground in a glue mill for 2 hours to obtain a slurry, which is sprayed on the metal foam assembly, and then dried and solidified at 90℃, repeated spraying 3 times, so that the average thickness of the coating on the metal foam reaches 300 microns, and the pore-forming agent is removed by calcination at 600℃ for 3 hours to obtain an adsorption heat storage material with multi-level hierarchical porosity.

[0068] Comparative Example: Foamed copper with a porosity of 75% (all with a size of 50*50*15mm) is cleaned with acetone and deionized water for 3 times respectively, and then dried at 80℃ for 6 hours. 13X molecular sieve adsorbent, deionized water, silica sol are mixed in a mass ratio of 1:1:0.2, and ground in a glue mill for 2 hours to obtain a slurry, which is sprayed on the metal foam assembly, and then dried and solidified at 90℃, repeated spraying 3 times, so that the average thickness of the coating on the metal foam reaches 300 microns, and the pore-forming agent is removed by calcination at 600℃ for 3 hours to obtain a comparative adsorption heat storage material.

[0069] Test Result Comparison: Under the conditions of 1.27 kPa water partial pressure and 30℃ temperature, the water adsorption capacity, average adsorption speed and thermal conductivity of the adsorption heat storage materials obtained in the examples and the comparative example are tested, and the results are shown in Table 1. It can be seen that the adsorption speed and thermal conductivity of the examples of the present application are significantly higher than those of the comparative example.

[0070] Table 1

[0071]

[0072] Through the above examples, the purpose of the present application is completely effectively achieved. Those skilled in the art can understand that the present application includes but is not limited to what is described in the drawings and the above specific embodiments. Although the present application has been described with respect to the presently preferred and most advantageous embodiments, it should be understood that the present application is not limited to the disclosed embodiments, and any modification that does not deviate from the functional and structural principles of the present application will be included in the scope of the claims.

Claims

1. An adsorptive thermal storage material with multi-stage hierarchical porous structure for efficient thermal energy storage and rapid release, comprising at least a metal foam substrate and an adsorbent coating, characterized in that, the metal foam substrate is used for conducting thermal energy and providing structural support, comprising at least multiple layers of metal foam with different porosities, the thermal conductivity of the metal foam material in each layer is not less than 0.5 W / m·K, and the porosities of the multiple layers of metal foam increase step by step along the direction of the heat source, the porosity of the metal foam layer closest to the heat source is the smallest, which is controlled within the range of 30%~50% to optimize the conduction efficiency of thermal energy and reduce thermal resistance, the porosity of the metal foam layer farthest from the heat source is the largest, which is controlled within the range of 60%~85% to increase the diffusion rate of adsorbate and enhance the adsorption capacity, the porosity of each layer of metal foam material is controlled by precisely adjusting the manufacturing process of metal foam to ensure that the conduction and diffusion of thermal energy between different layers are balanced, and the adjacent metal foam layers are connected by welding at the interface to form a stable multi-layer structure, ensuring the mechanical stability and thermal conductivity of the metal foam substrate under high temperature and multiple thermal cycles; the adsorbent coating is used for adsorbing and releasing working fluid and uniformly coated on the surface of the metal foam substrate, the overall thickness is controlled within the range of 100~1000 μm to ensure that the coating has good adsorption capacity and heat transfer performance, and the adsorbent coating is formed in a multi-stage porous structure composed of a large number of large pores, mesopores and micropores to facilitate the acceleration of the diffusion rate of adsorbate and improve the adsorption and desorption efficiency, wherein: the pore size range of the large pores is controlled within 50~200 nm to promote the rapid diffusion of working fluid and the rapid transfer of heat, the pore size range of the mesopores is controlled within 2~50 nm to provide a larger specific surface area and enhance the adsorption capacity, and the pore size of the micropores is controlled to be less than 2 nm to improve the adsorption density and storage capacity of the adsorbate; the combination of the metal foam substrate and the adsorbent coating makes the prepared adsorptive thermal storage material have high efficient heat conduction and adsorption performance during the heat storage and release process, the thermal resistance is effectively reduced through the hierarchical porous structure of the metal foam substrate, and the diffusion rate of the adsorbate is improved through the multi-stage porous structure in the adsorbent coating, thereby improving the thermal energy storage and release efficiency of the adsorptive thermal storage material.

2. The adsorptive heat storage material having a multi-stage hierarchical porosity according to claim 1, characterized in that, the metal foam substrate is composed of 2-5 layers of metal foam with different porosities, the metal foam material in each metal foam layer is one or a combination of foam copper, foam aluminum, foam nickel, foam iron, foam titanium, the porosity of each metal foam layer is precisely controlled by adjusting the manufacturing process of the metal foam material, including adjusting the type and adding amount of foaming agent, controlling the melting temperature of the metal foam and the foam generation time, thereby realizing the porosity control of each layer of metal foam material and ensuring that the combination of different porosity metal foam layers has good mechanical stability and thermal conductivity.

3. The adsorptive heat storage material having a multi-stage hierarchical porosity according to claim 2, characterized in that, The porosity difference in each layer of metal foam material of the metal foam substrate is realized by controlling the gas release rate and cooling rate in the process of forming the metal foam, and specifically by accelerating the gas release rate to increase the foam porosity, and by slow cooling to reduce the porosity of the metal foam, and finally achieving a porosity gradient gradually increasing in the direction of the heat source.

4. The adsorptive heat storage material having a multi-stage hierarchical porosity according to claim 1, characterized in that, The adsorbent coating is composed of an adsorbent, a binder and a pore former, wherein the adsorbent is one or a combination of zeolite, silica gel, alumina, molecular sieve, the binder is selected from one or a combination of silica sol, aluminum sol, titanium sol, organic silicone resin, yellow dextrin, sesbania powder, and the pore former is selected from one or a combination of cellulose, nano-graphite sheet, ammonium bicarbonate, acrylic resin, and each component is reasonably proportioned to ensure the adsorption performance and structural stability of the coating.

5. The adsorptive heat storage material having a multi-stage hierarchical porosity according to claim 1, characterized in that, The multi-layer structure of the metal foam substrate adopts a step-by-step welding or brazing process, so that the combination between each layer of metal foam material is not only physically stable, but also has good continuity in heat conduction, so that the heat transfer in the metal foam substrate is more efficient.

6. A method for producing the adsorbing heat accumulating material having a multi-stage hierarchical pore structure according to any one of claims 1 to 5, characterized by, The preparation method at least includes the following steps when implemented: SS1. Preparation of the metal foam substrate: selecting 2-5 metal foam layers with different porosities, the thermal conductivity of the metal foam material in each metal foam layer is not less than 0.5 W / m·K, arranging the selected metal foam layers from small to large porosity to form a stepped porosity structure, wherein the porosity of the lowermost metal foam layer is the smallest, and the porosity is controlled within the range of 30%-50%, the porosity of the uppermost metal foam layer is the largest, and the porosity is controlled within the range of 60%-85%, and the adjacent metal foam layers are connected by welding at the interface, forming a stable multi-layer structure; SS2. Cleaning and drying of the metal foam substrate: using organic solvents and deionized water combined with ultrasonic cleaning or acid pickling treatment, the metal foam substrate prepared in step SS1 is cleaned to remove impurities, oil stains and oxides attached to the surface of the metal foam substrate, and then dried at a temperature of 60-80℃ for 2-10 hours to ensure that the surface of the metal foam substrate is free of water and organic residues; SS3. Preparation of adsorbent coating slurry: mix the adsorbent, deionized water, binder and pore former in appropriate proportions to form a slurry, the proportioning of the slurry is optimized according to experimental data to ensure uniform distribution of the adsorbent particles and moderate bonding force between the binder and the adsorbent, wherein the adsorbent is at least one of zeolite, silica gel, alumina, and molecular sieve, the binder is at least one of silica sol, aluminum sol, titanium sol, organic silicone resin, yellow dextrin, and sesbania powder, and the pore former is at least one of cellulose, nano-graphite sheet, ammonium bicarbonate, and acrylic resin, and the slurry is ground in a glue mill for 1-3 hours to ensure that the average particle size of the slurry is controlled within the range of 30-50 nm; SS4. Coating of the adsorbent coating: the prepared slurry is uniformly coated on the surface of the metal foam substrate obtained in step SS2 by dip coating or spray coating, wherein in the dip coating process, the metal foam substrate is immersed in the slurry to ensure uniform coating of the coating, and in the spray coating, a special spray gun is used to spray the slurry onto the surface of the metal foam substrate, and after drying and curing at 70-90 ℃, a coating is formed, and one or more coatings are applied until the desired coating thickness is reached, and the overall thickness of the coating is controlled to be 100-1000 μm; SS5. Calcination treatment of the adsorbent coating: the metal foam substrate coated with the adsorbent coating is calcined at a temperature of 500-600 ℃ for 1-6 hours, and the organic solvent, moisture and pore-forming agent in the adsorbent coating are removed by calcination treatment to form a multi-level pore structure containing a large number of micropores, mesopores and macropores in the adsorbent coating, thereby obtaining an adsorption and heat storage material with a multi-level hierarchical pore structure.

7. The production method according to claim 6, wherein In step SS1, when forming each metal foam layer, the selected metal material is heated to a molten state, the foaming process of the molten metal, the amount of foaming agent added and the foam cooling speed are controlled to form metal foams with different porosities; and the thickness of each metal foam layer can be adjusted according to actual application requirements, controlled within the range of 10-50 mm, and the difference in porosity between adjacent metal foam layers is controlled within the range of 5%-15%.

8. The preparation method according to claim 6, characterized in that, In step SS2, the organic solvent is acetone, and the cleaning process includes immersing the metal foam substrate in acetone and deionized water for 3 times each, with each immersion time not less than 10 minutes, and ultrasonic cleaning is used to improve the cleaning effect; the drying process uses a vacuum drying oven, which is carried out at 60-80 ℃ and a pressure not higher than 0.1 MPa to ensure that the moisture and organic solvent residues in the internal pores of the metal foam substrate are fully removed.

9. The preparation method according to claim 6, characterized in that, In step SS3, the mass ratio of adsorbent, deionized water, binder and pore-forming agent is 1:1:0.1-0.2:0.02-0.1, wherein the adsorbent is selected from 13X molecular sieve, the binder is selected from silica sol, and the pore-forming agent is selected from cellulose; in the slurry preparation process, the adsorbent is first mixed with deionized water and stirred for 30 minutes, then the binder is added and stirred for another 30 minutes, and finally the pore-forming agent is added and stirred uniformly; after the slurry is obtained, it is ground at a speed of 300-500 rpm for 2 hours to ensure the uniformity and stability of the slurry.

10. The method of claim 6, wherein, In step SS4, spray coating is used, a pneumatic spray gun is used, the spray pressure is controlled at 0.2-0.3 MPa, and the spray distance is maintained at 15-20 cm; after each spray, dry at 80 ℃ for 30 minutes, repeat the spray 3-5 times to achieve the required thickness of the coating; after the last spray, pre-cure at 85 ℃ for 2 hours, and then post-cure at 120 ℃ for 1 hour to ensure the bonding strength between the coating and the metal foam substrate; the final thickness of the coating is controlled to be 300±50 μm.

11. The preparation method according to claim 6, characterized in that, In step SS5, the sintering process adopts a programmed temperature rising mode, the temperature is raised from room temperature to 300℃ at a rate of 2℃ / min and kept for 1 hour to remove residual moisture, then raised to 400℃ and kept for 1 hour to decompose organic matter, finally raised to 550℃ and kept for 3 hours to completely remove the pore-forming agent, and the cooling process adopts natural cooling, the cooling rate is not more than 5℃ / min to avoid coating cracking or falling off due to thermal stress.

12. The method of claim 6, wherein, After step SS5, step SS6 of testing the performance of the prepared adsorption heat storage material is further included, including testing the thermal conductivity, adsorption capacity and adsorption rate of the material, wherein the thermal conductivity test adopts the transient plane heat source method and the test temperature is 30℃, the adsorption performance test is carried out under the standard test conditions of 1.27 kPa water pressure and 30℃ temperature, the change of adsorption amount within 60 minutes is recorded, and the water vapor adsorption amount of the adsorption heat storage material is ensured to be not less than 0.35 g / g, the average adsorption speed is not less than 1.2 g / min, and the thermal conductivity is not less than 0.85 W / m·K, to meet the actual application requirements.

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