High-heat-storage-density stable thermochemical-adsorption composite heat storage material and preparation method thereof

Abstract

The invention discloses a high heat storage density stable thermochemical adsorption composite heat storage material and a preparation method thereof, the high heat storage density stable thermochemical adsorption composite heat storage material comprises 54%-57% by mass of mixed salt and 43%-46% by mass of a porous material, the mixed salt comprises MgSO4 and MgCl2, the mass ratio of MgSO4 to MgCl2 is 9: 1-6: 4, and the porous material is expanded perlite modified by nano alumina or a silane coupling agent. The high-heat-storage-density stable thermochemical-adsorption composite heat storage material provided by the invention is simple in preparation method, and the modified expanded perlite is used as a carrier of the mixed hydrated salt; the obtained composite heat storage material has excellent performance: the salt-containing load rate is 114-121%, the water absorption rate is 1.2-1.28 g / g, the heat storage density is 1123.5-1208.6 kJ / kg, the heat storage temperature is 133.4-141.3 DEG C, the structural strength is 10.346-12.631 kPa, the structural stability is 99.27-99.53%, and the stability is 79.7-83.3% after circulation for 30 times, that is, the composite heat storage material is high in heat storage density, high in water absorption rate, low in heat storage temperature, high in strength and not easy to scatter and fall off, and the composite heat storage material is suitable for large-scale production. And the material also has relatively good cycling stability.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and more specifically, to a high heat storage density stable thermochemical adsorption composite heat storage material and its preparation method. Background Technology

[0002] Thermal energy storage technology is a technique that stores excess energy in the form of heat, cold, or a combination thereof in a medium, and utilizes it directly or indirectly through energy conversion processes when needed. It effectively addresses the mismatch between solar energy supply and demand in time and space. With the continued advancement of dual-carbon goals and the vigorous development of clean energy, thermal energy storage technology is gradually becoming a key link in achieving efficient energy utilization and stable supply. The government has already introduced a series of policies to support the development of energy storage and renewable energy, and may further increase policy support in the future, providing more development opportunities for the thermal energy storage industry. The thermal energy storage industry will also deeply integrate with other industries to form a more complete industrial chain, achieving diversified energy utilization and efficient management.

[0003] Existing thermal storage technologies can be divided into sensible thermal storage, latent thermal storage, and thermochemical thermal storage.

[0004] Sensible thermal energy storage utilizes the inherent heat capacity of materials to store and release thermal energy during heating and cooling processes. Commonly used storage media include water, soil, rock, concrete, and molten salt. Sensible thermal energy storage technology is simple and low-cost, making it the most mature and only commercially viable thermal energy storage technology. However, sensible thermal storage methods have low energy density (e.g., the heat density (HSD) of water at a 50°C temperature difference is 210 kJ / kg), significant heat loss, and are unsuitable for long-term storage.

[0005] Latent heat storage utilizes the absorption or release of latent heat during a phase change in the storage material to store and release energy; hence, it is also called phase change thermal energy storage. Commonly used phase change materials include ice-water, hydrated salts, molten salts, paraffin wax, and fatty acids. Compared to sensible heat storage, phase change materials have a higher energy density (HSD of 150–250 kJ / kg), and the material remains approximately at an isothermal temperature during heat release. However, in practical applications, they are limited by problems such as phase separation, low thermal conductivity, large supercooling, and strong corrosivity.

[0006] Thermochemical energy storage utilizes the interconversion of thermal and chemical energy in reversible chemical reactions to store energy. During heating, thermal energy is converted into chemical energy, and during cooling, chemical energy is converted back into thermal energy. It offers advantages such as high energy storage density (800–2000 kJ / kg), long-term lossless energy storage, long-distance transportation, and zero pollution. Commonly used thermochemical energy storage materials mainly include hydrated salts, ammonium salts, and metal oxides.

[0007] Chinese patent application CN 113652206 A discloses a calcium-magnesium-based thermochemical adsorption thermal storage material and its preparation method. The material comprises 10%-30% porous material, 42%-54% CaCl2, and 28%-36% MgSO4 by mass. The preparation steps include inorganic salt mixing, porous material grinding, preparation of a composite thermal storage material suspension, drying of the composite thermal storage material, pressing of the composite thermal storage material, and testing of the composite thermal storage material. The prepared calcium-magnesium-based thermochemical thermal storage material achieves a thermal storage density of 1400 kJ / kg, but its peak temperature exhibits multiple peaks, indicating that thermal storage is carried out in stages, requiring a temperature as high as 226℃ to complete. The water absorption rate is low, with the highest adsorption capacity reaching only 0.45 g / g. Furthermore, the material exhibits unstable molding, poor cycle stability, and is prone to clumping after cycling.

[0008] Chinese patent application CN116904168A discloses a thermochemical adsorption composite thermal storage material and its preparation method. The material comprises 10% by mass of porous material (13X molecular sieve and modified expanded graphite in a mass ratio of 8:2 to 2:8), 90% by mass of mixed salt (MgSO4 and MgCl2 in a mass ratio of 9:1), and high-concentration silica sol. The preparation steps include: modification of expanded graphite, grinding of 13X molecular sieve, mixing of inorganic salts, preparation of a composite thermal storage material suspension, drying, bonding, and pressing. The prepared composite thermal storage material achieves a thermal storage density of 979.2 kJ / kg and a thermal storage temperature below 85℃, but has a low water absorption rate, with a maximum adsorption capacity of only 0.756 g / g. Even after 40 cycles, it can still maintain a thermal storage density of over 67%. However, the molding process is unstable and prone to lumps; the pressing process is complex. Summary of the Invention

[0009] To overcome the shortcomings of existing technologies, this invention provides a thermochemical adsorption thermal storage material and its preparation method. The problems to be solved are: the thermochemical adsorption composite thermal storage material has a low water absorption rate, and the briquetting process is complex and the molding is unstable; how to reduce the material preparation cost and simplify the preparation process, and improve the structural stability and thermal adsorption stability of the composite thermochemical adsorption thermal storage material, are still the key issues facing current thermochemical thermal storage materials.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A high-density, stable thermochemical adsorption composite thermal storage material comprises 54%-57% by mass of a mixed salt and 43%-46% by mass of a porous material. The mixed salt is MgSO4 and MgCl2, with a mass ratio of MgSO4 to MgCl2 of 9:1-6:4. The porous material is modified expanded perlite, which exhibits good structural strength and a high salt loading rate. The high-density, stable thermochemical adsorption composite thermal storage material provided by this technical solution has the following advantages: high thermal storage density, high water absorption rate, low thermal storage temperature, high strength and resistance to clumping and powdering, good cycle stability, and the ability to achieve long-term, heat-loss-free thermal storage under sealed conditions, as well as cross-seasonal heat storage and long-distance heat transfer.

[0012] Based on the above technical solution, as an improvement to the high heat storage density stable thermochemical adsorption composite heat storage material, the mixed salt is composed of MgSO4 and MgCl2 in a mass ratio of 9:1, 8:2, 7:3, or 6:4.

[0013] Based on the above technical solution, as an improvement to the high heat storage density stable thermochemical adsorption composite heat storage material, the modified expanded perlite is expanded perlite modified with 3-aminopropyltriethoxysilane (analytical grade, MW=221.37).

[0014] Based on the above technical solution, as an improvement to the high heat storage density stable thermochemical adsorption composite heat storage material, the expanded perlite is expanded perlite modified with nano alumina (γ phase, 20nm, MW=101.96).

[0015] A method for preparing a high heat storage density stable thermochemical adsorption composite thermal storage material, used to prepare the high heat storage density stable thermochemical adsorption composite thermal storage material in the above technical solution, includes the following steps: modifying expanded perlite, preparing a composite inorganic salt solution, mixing the modified expanded perlite with the composite inorganic salt solution and impregnating at high temperature, and drying at constant temperature.

[0016] Based on the above technical solution, as an improvement to the above preparation method, when using 3-aminopropyltriethoxysilane (analytical grade, MW = 221.37) to modify expanded perlite, the preparation steps include the following:

[0017] Step 1: Drying expanded perlite: Weigh a certain amount of expanded perlite, wash it, and then place it in a constant temperature drying oven to dry.

[0018] Step 2, Modification of Expanded Perlite: Dissolve 3-aminopropyltriethoxysilane in ethanol and stir until homogeneous to obtain a silane coupling agent solution. Add the dried expanded perlite from Step 1 to the silane coupling agent solution and stir to ensure that the 3-aminopropyltriethoxysilane molecules are evenly distributed on the surface of the expanded perlite. Then, allow it to stand at room temperature and place it in a drying oven for gradient drying to promote the formation of covalent bonds between 3-aminopropyltriethoxysilane and the surface of the expanded perlite, thus obtaining modified expanded perlite.

[0019] Step 3: Inorganic salt mixing: Add MgSO4 and MgCl2 to deionized water according to the specified ratio and stir to obtain a salt solution with a concentration of 25wt%.

[0020] Step 4: Prepare the suspension: Mix the modified expanded perlite obtained in Step 2 with the salt solution obtained in Step 3 to form a suspension, and then impregnate the solid-liquid mixture at high temperature.

[0021] Step 5, Drying: After filtering the suspension prepared in Step 4, place it in a drying oven and dry at a constant temperature to obtain the finished product.

[0022] Based on the above technical solution, as an improvement to the above preparation method, the solubility of 3-aminopropyltriethoxysilane in the silane coupling agent solution is 2.5% to 10%.

[0023] Based on the above technical solution, as an improvement to the above preparation method, the drying temperature in step one is 150℃ and the drying time is 2 hours; the gradient drying in step two includes drying at 80℃ for 2 hours first, and then heating to 120℃ and holding for 1 hour; the high-temperature impregnation temperature in step four is 80℃ and the impregnation time is 24 hours; the constant temperature drying temperature in step five is 150℃ and the drying time is 2 hours.

[0024] Based on the above technical solution, as an improvement to the above preparation method, when using nano-alumina (γ phase, 20 nm, MW = 101.96) to modify expanded perlite, the preparation steps include the following:

[0025] Step 1: Drying expanded perlite: Weigh a certain amount of expanded perlite, wash it, and then place it in a constant temperature drying oven to dry.

[0026] Step 2, Modification of Expanded Perlite: Disperse nano-alumina in deionized water and use an ultrasonic processor to uniformly disperse it to prepare a nano-alumina dispersion. Immerse the expanded perlite dried in Step 1 in the nano-alumina dispersion and stir evenly to ensure that the nano-alumina particles are evenly distributed on the surface of the expanded perlite. After filtering out excess liquid, transfer it to a drying oven to dry. Finally, calcine it in a tube furnace to firmly bond the nano-alumina with the surface of the expanded perlite to form a high-strength surface layer, thus obtaining modified expanded perlite.

[0027] Step 3: Inorganic salt mixing: Add MgSO4 and MgCl2 to deionized water according to the specified ratio and stir to obtain a salt solution with a concentration of 25wt%.

[0028] Step 4: Prepare the suspension: Mix the modified expanded perlite obtained in Step 2 with the solution in Step 3 to form a suspension, and then impregnate the solid-liquid mixture at high temperature.

[0029] Step 5: Drying: After filtering the suspension prepared in Step 4, place it in a constant temperature drying oven to dry and obtain the finished product.

[0030] Based on the above technical solution, as an improvement to the above preparation method, the concentration of nano-alumina in the nano-alumina dispersion is 2.5% to 10%; the drying temperature in step one is 150℃ and the drying time is 2 hours; in step two, the ultrasonic dispersion time is 10 minutes, the stirring time is 30 minutes, the drying temperature is 80℃ and the drying time is 2 hours, and the calcination temperature is 400℃ and the calcination time is 1 hour; the high-temperature impregnation temperature in step four is 80℃ and the time is 24 hours; and the constant temperature drying temperature in step five is 150℃ and the drying time is 2 hours.

[0031] The method for testing composite thermal storage materials according to the present invention is as follows:

[0032] The prepared high-density, stable thermochemical adsorption composite thermal storage material was subjected to adsorption performance tests, thermal storage performance tests, cycle stability tests, and strength tests. Adsorption performance was tested using a constant temperature and humidity chamber. Thermal storage performance was tested using differential scanning calorimetry (DSC). Physical properties were analyzed using X-ray diffraction (XRD). Cyclic stability was tested using a constant temperature and humidity chamber for 30 cycles.

[0033] Test results show that the beneficial effects of this invention are as follows:

[0034] The porous material utilized in this invention, expanded perlite, possesses good structural strength. As a granular natural porous material, it serves as a matrix material for loading hydrated salts, ensuring a good morphological structure and thus good stability. Furthermore, expanded perlite has large pores, exhibiting excellent salt adsorption and storage capabilities, with a maximum salt loading rate of 1.32 g / g, a capability not found in most thermochemical heat storage materials. This excellent salt adsorption capacity provides a strong guarantee for subsequent dehumidification. However, in thermochemical heat storage materials loaded with expanded perlite, hydrated salts are prone to leakage during use, resulting in powder shedding. Therefore, this patent employs silane coupling agents or nano-Al2O3 to modify expanded perlite, improving the powder shedding problem after loading hydrated salts. The modified composite thermal storage material exhibits superior performance: a salt loading rate of 114-121%, a water absorption rate of 1.2-1.28 g / g, a thermal storage density of 1123.5-1208.6 kJ / kg, a thermal storage temperature of 133.4-141.3℃, a structural strength of 10.346-12.631 kPa, a structural stability of 99.27-99.53%, and a stability of 79.7%-83.3% after 30 cycles. This means it possesses high thermal storage density, high water absorption, low thermal storage temperature, high strength, and is not prone to clumping or powdering. It also exhibits good cycle stability, enabling long-term, heat-loss-free thermal storage under sealed conditions, and facilitating cross-seasonal heat storage and long-distance heat transfer.

[0035] The high thermal density stable thermochemical adsorption composite thermal storage material provided by this invention helps achieve energy conservation and efficient utilization. By storing a large amount of thermal energy and releasing it when needed, this technology can effectively balance the time difference between energy supply and demand, reducing energy waste. This plays a positive role in alleviating energy pressure, improving energy utilization efficiency, and reducing energy costs. The high thermal density stable thermochemical adsorption composite thermal storage material also helps promote the widespread application of renewable energy. Because renewable energy sources such as solar and geothermal energy are intermittent and unstable, their large-scale utilization is limited. The high thermal density stable thermochemical adsorption composite thermal storage material can solve this problem by storing renewable energy to provide a stable thermal energy supply when needed. This helps promote the popularization and development of renewable energy, reduce dependence on traditional energy sources, and thus optimize and upgrade the energy structure. Attached Figure Description

[0036] Figure 1 A schematic diagram of the preparation method of high heat storage density composite thermochemical adsorption heat storage material;

[0037] (a) is the preparation process of unmodified expanded perlite composite thermal storage material;

[0038] (b) is the preparation process of expanded perlite composite thermal storage material modified with nano-Al2O3.

[0039] (c) is the preparation process of expanded perlite composite thermal storage material modified with silane coupling agent.

[0040] Figure 2 Adsorption curves of high thermal density composite thermochemical adsorption heat storage materials;

[0041] (a) shows the adsorption curves of MCP1, MCP2, MCP3, and MCP4;

[0042] (b) shows the adsorption curves of EP@2.5%Si, EP@5%Si, EP@7.5%Si, and EP@10%Si;

[0043] (c) shows the adsorption curves of EP@2.5%Al2O3, EP@2.5%Al2O3, EP@2.5%Al2O3, and EP@2.5%Al2O3.

[0044] Figure 3 XRD patterns of MgSO4, MgCl2, expanded perlite, MCP1, MCP2, MCP3, and MCP4;

[0045] The XRD pattern shows the characteristic peaks of MgSO4, MgCl2, expanded perlite, MCP1, MCP2, MCP3, and MCP4.

[0046] Figure 4 DSC diagram of high heat storage density composite thermochemical adsorption heat storage material;

[0047] (a) is the DSC diagram of MgSO4 and MgCl2;

[0048] (b) DSC plots for MgSO4:MgCl2 = 9:1, 8:2, 7:3, and 6:4;

[0049] (c) is the DSC diagram of MCP1, MCP2, MCP3, and MCP4;

[0050] (d) DSC plots of EP@2.5%Al2O3, EP@2.5%Al2O3, EP@2.5%Al2O3, and EP@2.5%Al2O3;

[0051] (e) DSC diagrams of EP@2.5%Si, EP@5%Si, EP@7.5%Si, EP@10%Si.

[0052] Figure 5 This is a graph showing the cyclic stability test results of the composite material.

[0053] (a) is a graph showing the cyclic stability test of MCP4.

[0054] (b) is a graph showing the cyclic stability test of EP@5%Al2O3;

[0055] (c) is a graph showing the cyclic stability test of EP@7.5%Si;

[0056] Figure 6 Pressure breakage test diagrams for high thermal density thermochemical adsorption heat storage materials MCP4, EP@5%Al2O3, and EP@7.5%Si;

[0057] (a) is a schematic diagram of the pressure breakage test process;

[0058] (b) Graph of pressure breakage test results.

[0059] Figure 7 The structural stability (weight retention rate of intact particles) of composite thermal storage materials MCP4, EP@5%Al2O3, and EP@7.5%Si after ultrasonic vibration is shown in the figure.

[0060] (a) shows the structural stability test diagram of MCP4;

[0061] (b) shows the structural stability test results of EP@5%Al2O3;

[0062] (c) is a structural stability test diagram of EP@7.5%Si;

[0063] (d) is a statistical chart showing the retention rate of intact particles of MCP4, EP@5%Al2O3, and EP@7.5%Si after ultrasonic vibration.

[0064] Figure 8 This is an image showing the appearance of a high-density composite thermochemical adsorption thermal storage material.

[0065] In the above figures:

[0066] Expanded perlite was named EP.

[0067] The high heat storage density composite thermochemical adsorption heat storage materials obtained by impregnation with pure MgSO4 and MgCl2 were named MCPS and MCPC, respectively.

[0068] The high thermal storage density composite thermochemical adsorption thermal storage materials obtained by impregnating unmodified expanded perlite with a MgSO4:MgCl2 mixed salt ratio of 9:1, 8:2, 7:3, and 6:4 were named MCP1, MCP2, MCP3, and MCP4, respectively.

[0069] The high heat storage density composite thermochemical adsorption heat storage materials obtained by modification with 2.5%, 5%, 7.5%, and 10% of 3-aminopropyltriethoxysilane (analytical grade, MW=221.37) were named EP@2.5%Si, EP@5%Si, EP@7.5%Si, and EP@10%Si, respectively.

[0070] The high heat storage density composite thermochemical adsorption heat storage materials obtained by modification with 2.5%, 5%, 7.5%, and 10% nano-alumina (γ phase, 20nm, MW=101.96) were named EP@2.5%Al2O3, EP@5%Al2O3, EP@7.5%Al2O3, and EP@10%Al2O3, respectively. Detailed Implementation

[0071] This invention discloses a porous thermochemical adsorption heat storage material and its preparation method, comprising 43%-46% porous material by mass, and 54%-57% of a binary mixed salt of MgCl2 and MgSO4, wherein the mass ratio of MgSO4 to MgCl2 is 9:1-6:4. The porous material is modified expanded perlite, wherein MgCl2 accounts for 5.7%-22.8% and MgSO4 accounts for 34.2%-51.3%. The preparation steps include modifying the expanded perlite, preparing a composite inorganic salt solution, mixing the modified expanded perlite with the composite inorganic salt solution and impregnating at high temperature, and drying at a constant temperature.

[0072] The following describes specific embodiments and... Figures 1 to 8 Further explanation of the present invention:

[0073] A high thermal storage density stable thermochemical adsorption composite thermal storage material comprises 54%-57% by mass of a mixed salt and 43%-46% by mass of a porous material. The mixed salt is MgSO4 and MgCl2, with a mass ratio of MgSO4 to MgCl2 of 9:1-6:4. The porous material is modified expanded perlite, which has good structural strength and outstanding salt loading rate.

[0074] The high heat storage density stable thermochemical adsorption composite heat storage material provided by this technical solution has the following advantages: high heat storage density, high water absorption rate, low heat storage temperature, high strength and not easy to break apart or shed powder. It also has good cycle stability, can achieve long-term heat storage without heat loss under environmental conditions, and can realize cross-seasonal heat storage and long-distance transmission.

[0075] Based on the above technical solution, as an improvement to the high heat storage density stable thermochemical adsorption composite heat storage material, the mixed salt is composed of MgSO4 and MgCl2 in a mass ratio of 9:1, 8:2, 7:3, or 6:4.

[0076] Based on the above technical solution, as an improvement to the high heat storage density stable thermochemical adsorption composite thermal storage material, the modified expanded perlite is expanded perlite modified with 3-aminopropyltriethoxysilane (analytical grade, MW = 221.37). Preferably, the solubility of 3-aminopropyltriethoxysilane in the solution is 2.5-10%. Preferably, the solubility of 3-aminopropyltriethoxysilane is 7.5%, but any other concentration within the range of 2.5-10% can also be used.

[0077] Based on the above technical solution, as an improvement to the high heat storage density stable thermochemical adsorption composite thermal storage material, the expanded perlite is expanded perlite modified with nano-alumina (γ phase, 20nm, MW=101.96). Preferably, the concentration of nano-alumina in the nano-alumina dispersion is 2.5-10%, but any other concentration within the 2.5-10% range can also be used.

[0078] There are two modification methods for expanded perlite: one is to use nano-alumina, and the other is to use a silane coupling agent, preferably 3-aminopropyltriethoxysilane. Regardless of the modifier used, the concentration of the modifier can be one of the following four preferred concentrations: 2.5%, 5%, 7.5%, and 10%.

[0079] A method for preparing a high heat storage density stable thermochemical adsorption composite thermal storage material, used to prepare the high heat storage density stable thermochemical adsorption composite thermal storage material in the above technical solution, includes the following steps: modifying expanded perlite, preparing a composite inorganic salt solution, mixing the modified expanded perlite with the composite inorganic salt solution and impregnating at high temperature, and drying at constant temperature.

[0080] Based on the above technical solution, as an improvement to the above preparation method, when using 3-aminopropyltriethoxysilane (analytical grade, MW = 221.37) to modify expanded perlite, the preparation steps include the following:

[0081] Step 1: Drying expanded perlite: Weigh a certain amount of expanded perlite, wash it, and then place it in a constant temperature drying oven to dry.

[0082] Step 2, Modification of Expanded Perlite: Dissolve 3-aminopropyltriethoxysilane in ethanol and stir until homogeneous to obtain a silane coupling agent solution. Add the dried expanded perlite from Step 1 to the silane coupling agent solution and stir to ensure that the 3-aminopropyltriethoxysilane molecules are evenly distributed on the surface of the expanded perlite. Then, allow it to stand at room temperature and place it in a drying oven for gradient drying to promote the formation of covalent bonds between 3-aminopropyltriethoxysilane and the surface of the expanded perlite, thus obtaining modified expanded perlite.

[0083] Step 3: Inorganic salt mixing: Add MgSO4 and MgCl2 to deionized water according to the specified ratio and stir to obtain a salt solution with a concentration of 25wt%.

[0084] Step 4: Prepare the suspension: Mix the modified expanded perlite obtained in Step 2 with the salt solution obtained in Step 3 to form a suspension, and then impregnate the solid-liquid mixture at high temperature.

[0085] Step 5, Drying: After filtering the suspension prepared in Step 4, place it in a drying oven and dry at a constant temperature to obtain the finished product.

[0086] Based on the above technical solution, as an improvement to the above preparation method, the solubility of 3-aminopropyltriethoxysilane in the silane coupling agent solution is 2.5% to 10%.

[0087] Based on the above technical solution, as an improvement to the above preparation method, the drying temperature in step one is 150℃ and the drying time is 2 hours; the gradient drying in step two includes drying at 80℃ for 2 hours first, and then heating to 120℃ and holding for 1 hour; the high-temperature impregnation temperature in step four is 80℃ and the impregnation time is 24 hours; the constant temperature drying temperature in step five is 150℃ and the drying time is 2 hours.

[0088] Based on the above technical solution, as an improvement to the above preparation method, when using nano-alumina (γ phase, 20 nm, MW = 101.96) to modify expanded perlite, the preparation steps include the following:

[0089] Step 1: Drying expanded perlite: Weigh a certain amount of expanded perlite, wash it, and then place it in a constant temperature drying oven to dry.

[0090] Step 2, Modification of Expanded Perlite: Disperse nano-alumina in deionized water and use an ultrasonic processor to uniformly disperse it to prepare a nano-alumina dispersion. Immerse the expanded perlite dried in Step 1 in the nano-alumina dispersion and stir evenly to ensure that the nano-alumina particles are evenly distributed on the surface of the expanded perlite. After filtering out excess liquid, transfer it to a drying oven to dry. Finally, calcine it in a tube furnace to firmly bond the nano-alumina with the surface of the expanded perlite to form a high-strength surface layer, thus obtaining modified expanded perlite.

[0091] Step 3: Inorganic salt mixing: Add MgSO4 and MgCl2 to deionized water according to the specified ratio and stir to obtain a salt solution with a concentration of 25wt%.

[0092] Step 4: Prepare the suspension: Mix the modified expanded perlite obtained in Step 2 with the solution in Step 3 to form a suspension, and then impregnate the solid-liquid mixture at high temperature.

[0093] Step 5: Drying: After filtering the suspension prepared in Step 4, place it in a constant temperature drying oven to dry and obtain the finished product.

[0094] Based on the above technical solution, as an improvement to the above preparation method, the concentration of nano-alumina in the nano-alumina dispersion is 2.5% to 10%; the drying temperature in step one is 150℃ and the drying time is 2 hours; in step two, the ultrasonic dispersion time is 10 minutes, the stirring time is 30 minutes, the drying temperature is 80℃ and the drying time is 2 hours, and the calcination temperature is 400℃ and the calcination time is 1 hour; the high-temperature impregnation temperature in step four is 80℃ and the time is 24 hours; and the constant temperature drying temperature in step five is 150℃ and the drying time is 2 hours.

[0095] Example 1

[0096] The high thermal storage density stable thermochemical adsorption composite thermal storage material in this embodiment includes 43% by mass of modified expanded perlite and 57% by mass of a binary mixed salt of MgSO4 and MgCl2. The modified expanded perlite is modified with 3-aminopropyltriethoxysilane (analytical grade, MW=221.37), and the mass ratio of MgSO4 to MgCl2 is 9:1.

[0097] The preparation method of the high heat storage density stable thermochemical adsorption composite heat storage material in this embodiment is as follows:

[0098] Step 1: Drying expanded perlite: Weigh a certain amount of expanded perlite, wash it, and place it in a constant temperature drying oven to dry at 150℃ for 2 hours.

[0099] Step 2, Modification of Expanded Perlite: Different masses of silane coupling agent (3-aminopropyltriethoxysilane) were dissolved in ethanol and stirred evenly to obtain four different concentrations (2.5%, 5.0%, 7.5%, and 10%) of silane coupling agent solutions. The expanded perlite dried in Step 1 was added to the silane coupling agent solutions and stirred for 30 minutes to ensure that 3-aminopropyltriethoxysilane molecules were evenly distributed on the surface of the expanded perlite. After standing at room temperature for 1 hour, it was placed in a drying oven for gradient drying. Gradient drying included drying at 80°C for 2 hours to remove ethanol, and then heating to 120°C and holding for 1 hour to promote the formation of covalent bonds between 3-aminopropyltriethoxysilane and the surface of the expanded perlite. Four expanded perlite solutions modified with different concentrations of silane coupling agent were prepared.

[0100] Step 3: Inorganic salt mixing: Add MgSO4 and MgCl2 to deionized water in a ratio of 9:1 and stir to obtain a salt solution with a concentration of 25wt%.

[0101] Step 4: Prepare the suspension: Mix the modified expanded perlite obtained in Step 2 with the salt solution obtained in Step 3 to form a suspension, and then perform high-temperature impregnation of the solid-liquid mixture; the high-temperature impregnation temperature is 80℃ and the impregnation time is 24 hours.

[0102] Step 5, Drying: After filtering the suspension prepared in Step 4, place it in a drying oven for constant temperature drying at 150℃ for 2 hours to obtain composite thermal storage materials modified with four different concentrations of silane coupling agent (2.5%, 5.0%, 7.5%, and 10%), which are named EP@2.5%Si, EP@5.0%Si, EP@7.5%Si, and EP@10%Si.

[0103] Example 2

[0104] The high thermal storage density stable thermochemical adsorption composite thermal storage material in this embodiment includes 44% by mass of modified expanded perlite and 56% by mass of a binary mixed salt of MgSO4 and MgCl2. The modified expanded perlite is modified with 3-aminopropyltriethoxysilane (analytical grade, MW=221.37), and the mass ratio of MgSO4 to MgCl2 is 8:2.

[0105] The preparation method of the high heat storage density stable thermochemical adsorption composite heat storage material in this embodiment is as follows:

[0106] Step 1: Drying expanded perlite: Weigh a certain amount of expanded perlite, wash it, and place it in a constant temperature drying oven to dry at 150℃ for 2 hours.

[0107] Step 2, Modification of Expanded Perlite: Different masses of silane coupling agent (3-aminopropyltriethoxysilane) were dissolved in ethanol and stirred evenly to obtain four different concentrations (2.5%, 5.0%, 7.5%, and 10%) of silane coupling agent solutions. The expanded perlite dried in Step 1 was added to the silane coupling agent solutions and stirred for 30 minutes to ensure that 3-aminopropyltriethoxysilane molecules were evenly distributed on the surface of the expanded perlite. After standing at room temperature for 1 hour, it was placed in a drying oven for gradient drying. Gradient drying included drying at 80°C for 2 hours to remove ethanol, and then heating to 120°C and holding for 1 hour to promote the formation of covalent bonds between 3-aminopropyltriethoxysilane and the surface of the expanded perlite. Four expanded perlite solutions modified with different concentrations of silane coupling agent were prepared.

[0108] Step 3: Inorganic salt mixing: Add MgSO4 and MgCl2 to deionized water in a ratio of 8:2 and stir to obtain a salt solution with a concentration of 25wt%.

[0109] Step 4: Prepare the suspension: Mix the modified expanded perlite obtained in Step 2 with the salt solution obtained in Step 3 to form a suspension, and then perform high-temperature impregnation of the solid-liquid mixture; the high-temperature impregnation temperature is 80℃ and the impregnation time is 24 hours.

[0110] Step 5, Drying: After filtering the suspension prepared in Step 4, place it in a drying oven for constant temperature drying at 150℃ for 2 hours to obtain composite thermal storage materials modified with four different concentrations of silane coupling agent (2.5%, 5.0%, 7.5%, and 10%), which are named EP@2.5%Si, EP@5.0%Si, EP@7.5%Si, and EP@10%Si.

[0111] Example 3

[0112] The high thermal storage density stable thermochemical adsorption composite thermal storage material in this embodiment includes 45% modified expanded perlite and 55% binary mixed salt of MgSO4 and MgCl2 by mass percentage. The modified expanded perlite is modified with 3-aminopropyltriethoxysilane (analytical grade, MW=221.37), and the mass ratio of MgSO4 to MgCl2 is 7:3.

[0113] The preparation method of the high heat storage density stable thermochemical adsorption composite heat storage material in this embodiment is as follows:

[0114] Step 1: Drying expanded perlite: Weigh a certain amount of expanded perlite, wash it, and place it in a constant temperature drying oven to dry at 150℃ for 2 hours.

[0115] Step 2, Modification of Expanded Perlite: Different masses of silane coupling agent (3-aminopropyltriethoxysilane) were dissolved in ethanol and stirred evenly to obtain four different concentrations (2.5%, 5.0%, 7.5%, and 10%) of silane coupling agent solutions. The expanded perlite dried in Step 1 was added to the silane coupling agent solutions and stirred for 30 minutes to ensure that 3-aminopropyltriethoxysilane molecules were evenly distributed on the surface of the expanded perlite. After standing at room temperature for 1 hour, it was placed in a drying oven for gradient drying. Gradient drying included drying at 80°C for 2 hours to remove ethanol, and then heating to 120°C and holding for 1 hour to promote the formation of covalent bonds between 3-aminopropyltriethoxysilane and the surface of the expanded perlite. Four expanded perlite solutions modified with different concentrations of silane coupling agent were prepared.

[0116] Step 3: Inorganic salt mixing: Add MgSO4 and MgCl2 to deionized water in a ratio of 7:3 and stir to obtain a salt solution with a concentration of 25wt%.

[0117] Step 4: Prepare the suspension: Mix the modified expanded perlite obtained in Step 2 with the salt solution obtained in Step 3 to form a suspension, and then perform high-temperature impregnation of the solid-liquid mixture; the high-temperature impregnation temperature is 80℃ and the impregnation time is 24 hours.

[0118] Step 5, Drying: After filtering the suspension prepared in Step 4, place it in a drying oven for constant temperature drying at 150℃ for 2 hours to obtain composite thermal storage materials modified with four different concentrations of silane coupling agent (2.5%, 5.0%, 7.5%, and 10%), which are named EP@2.5%Si, EP@5.0%Si, EP@7.5%Si, and EP@10%Si.

[0119] Example 4

[0120] The high thermal storage density stable thermochemical adsorption composite thermal storage material in this embodiment includes 46% by mass of modified expanded perlite and 53% by mass of a binary mixed salt of MgSO4 and MgCl2. The modified expanded perlite is modified with 3-aminopropyltriethoxysilane (analytical grade, MW=221.37), and the mass ratio of MgSO4 to MgCl2 is 6:4.

[0121] The preparation method of the high heat storage density stable thermochemical adsorption composite heat storage material in this embodiment is as follows:

[0122] Step 1: Drying expanded perlite: Weigh a certain amount of expanded perlite, wash it, and place it in a constant temperature drying oven to dry at 150℃ for 2 hours.

[0123] Step 2, Modification of Expanded Perlite: Different masses of silane coupling agent (3-aminopropyltriethoxysilane) were dissolved in ethanol and stirred evenly to obtain four different concentrations (2.5%, 5.0%, 7.5%, and 10%) of silane coupling agent solutions. The expanded perlite dried in Step 1 was added to the silane coupling agent solutions and stirred for 30 minutes to ensure that 3-aminopropyltriethoxysilane molecules were evenly distributed on the surface of the expanded perlite. After standing at room temperature for 1 hour, it was placed in a drying oven for gradient drying. Gradient drying included drying at 80°C for 2 hours to remove ethanol, and then heating to 120°C and holding for 1 hour to promote the formation of covalent bonds between 3-aminopropyltriethoxysilane and the surface of the expanded perlite. Four expanded perlite solutions modified with different concentrations of silane coupling agent were prepared.

[0124] Step 3: Inorganic salt mixing: Add MgSO4 and MgCl2 to deionized water in a ratio of 6:4 and stir to obtain a salt solution with a concentration of 25wt%.

[0125] Step 4: Prepare the suspension: Mix the modified expanded perlite obtained in Step 2 with the salt solution obtained in Step 3 to form a suspension, and then perform high-temperature impregnation of the solid-liquid mixture; the high-temperature impregnation temperature is 80℃ and the impregnation time is 24 hours.

[0126] Step 5, Drying: After filtering the suspension prepared in Step 4, place it in a drying oven for constant temperature drying at 150℃ for 2 hours to obtain composite thermal storage materials modified with four different concentrations of silane coupling agent (2.5%, 5.0%, 7.5%, and 10%), which are named EP@2.5%Si, EP@5.0%Si, EP@7.5%Si, and EP@10%Si.

[0127] Example 5

[0128] The high thermal storage density stable thermochemical adsorption composite thermal storage material in this embodiment includes 43% by mass of modified expanded perlite and 57% by mass of a binary mixed salt of MgSO4 and MgCl2. The modified expanded perlite is modified with nano-alumina (γ phase, 20nm, MW=101.96), and the mass ratio of MgSO4 to MgCl2 is 9:1.

[0129] The preparation method of the high heat storage density stable thermochemical adsorption composite heat storage material in this embodiment is as follows:

[0130] Step 1: Drying expanded perlite: Weigh a certain amount of expanded perlite, wash it, and place it in a constant temperature drying oven to dry at 150℃ for 2 hours.

[0131] Step 2: Modification of expanded perlite: Different masses of nano-alumina were dispersed in deionized water and uniformly dispersed for 10 minutes using an ultrasonic processor to prepare four different concentrations (2.5%, 5.0%, 7.5%, and 10%) of nano-Al2O3 dispersions. The expanded perlite dried in Step 1 was immersed in the nano-Al2O3 dispersions and stirred for 30 minutes until homogeneous, so that the nano-alumina particles were evenly distributed on the surface of the expanded perlite. After filtering out excess liquid, the perlite was transferred to a drying oven and dried at 80°C for 2 hours. Finally, it was sintered in a tube furnace at 400°C for 1 hour to firmly bond the nano-alumina with the surface of the expanded perlite to form a high-strength surface layer, resulting in four different concentrations of Al2O3-modified expanded perlite.

[0132] Step 3: Inorganic salt mixing: Add MgSO4 and MgCl2 to deionized water in a ratio of 9:1 and stir to obtain a salt solution with a concentration of 25wt%.

[0133] Step 4: Prepare the suspension: Mix the modified expanded perlite obtained in Step 2 with the salt solution obtained in Step 3 to form a suspension, and then perform high-temperature impregnation of the solid-liquid mixture; the high-temperature impregnation temperature is 80℃ and the impregnation time is 24 hours.

[0134] Step 5, Drying: After filtering the suspension prepared in Step 4, place it in a drying oven for constant temperature drying at 150℃ for 2 hours to obtain four composite thermal storage materials modified with different concentrations of nano-Al2O3 (2.5%, 5.0%, 7.5%, and 10%), which are named EP@2.5% Al2O3, EP@5.0% Al2O3, EP@7.5% Al2O3, and EP@10% Al2O3.

[0135] Example 6

[0136] The high thermal storage density stable thermochemical adsorption composite thermal storage material in this embodiment includes 44% by mass of modified expanded perlite and 56% by mass of a binary mixed salt of MgSO4 and MgCl2. The modified expanded perlite is modified with nano-alumina (γ phase, 20nm, MW=101.96), and the mass ratio of MgSO4 to MgCl2 is 8:2.

[0137] The preparation method of the high heat storage density stable thermochemical adsorption composite heat storage material in this embodiment is as follows:

[0138] Step 1: Drying expanded perlite: Weigh a certain amount of expanded perlite, wash it, and place it in a constant temperature drying oven to dry at 150℃ for 2 hours.

[0139] Step 2: Modification of expanded perlite: Different masses of nano-alumina were dispersed in deionized water and uniformly dispersed for 10 minutes using an ultrasonic processor to prepare four different concentrations (2.5%, 5.0%, 7.5%, and 10%) of nano-Al2O3 dispersions. The expanded perlite dried in Step 1 was immersed in the nano-Al2O3 dispersions and stirred for 30 minutes until homogeneous, so that the nano-alumina particles were evenly distributed on the surface of the expanded perlite. After filtering out excess liquid, the perlite was transferred to a drying oven and dried at 80°C for 2 hours. Finally, it was sintered in a tube furnace at 400°C for 1 hour to firmly bond the nano-alumina with the surface of the expanded perlite to form a high-strength surface layer, resulting in four different concentrations of Al2O3-modified expanded perlite.

[0140] Step 3: Inorganic salt mixing: Add MgSO4 and MgCl2 to deionized water in a ratio of 8:2 and stir to obtain a salt solution with a concentration of 25wt%.

[0141] Step 4: Prepare the suspension: Mix the modified expanded perlite obtained in Step 2 with the salt solution obtained in Step 3 to form a suspension, and then perform high-temperature impregnation of the solid-liquid mixture; the high-temperature impregnation temperature is 80℃ and the impregnation time is 24 hours.

[0142] Step 5, Drying: After filtering the suspension prepared in Step 4, place it in a drying oven for constant temperature drying at 150℃ for 2 hours to obtain four composite thermal storage materials modified with different concentrations of nano-Al2O3 (2.5%, 5.0%, 7.5%, and 10%), which are named EP@2.5% Al2O3, EP@5.0% Al2O3, EP@7.5% Al2O3, and EP@10% Al2O3.

[0143] Example 7

[0144] The high thermal storage density stable thermochemical adsorption composite thermal storage material in this embodiment includes 45% modified expanded perlite and 55% binary mixed salt of MgSO4 and MgCl2 by mass percentage. The modified expanded perlite is modified with nano-alumina (γ phase, 20nm, MW=101.96), and the mass ratio of MgSO4 to MgCl2 is 7:3.

[0145] The preparation method of the high heat storage density stable thermochemical adsorption composite heat storage material in this embodiment is as follows:

[0146] Step 1: Drying expanded perlite: Weigh a certain amount of expanded perlite, wash it, and place it in a constant temperature drying oven to dry at 150℃ for 2 hours.

[0147] Step 2: Modification of expanded perlite: Different masses of nano-alumina were dispersed in deionized water and uniformly dispersed for 10 minutes using an ultrasonic processor to prepare four different concentrations (2.5%, 5.0%, 7.5%, and 10%) of nano-Al2O3 dispersions. The expanded perlite dried in Step 1 was immersed in the nano-Al2O3 dispersions and stirred for 30 minutes until homogeneous, so that the nano-alumina particles were evenly distributed on the surface of the expanded perlite. After filtering out excess liquid, the perlite was transferred to a drying oven and dried at 80°C for 2 hours. Finally, it was sintered in a tube furnace at 400°C for 1 hour to firmly bond the nano-alumina with the surface of the expanded perlite to form a high-strength surface layer, resulting in four different concentrations of Al2O3-modified expanded perlite.

[0148] Step 3: Inorganic salt mixing: Add MgSO4 and MgCl2 to deionized water in a ratio of 7:3 and stir to obtain a salt solution with a concentration of 25wt%.

[0149] Step 4: Prepare the suspension: Mix the modified expanded perlite obtained in Step 2 with the salt solution obtained in Step 3 to form a suspension, and then perform high-temperature impregnation of the solid-liquid mixture; the high-temperature impregnation temperature is 80℃ and the impregnation time is 24 hours.

[0150] Step 5, Drying: After filtering the suspension prepared in Step 4, place it in a drying oven for constant temperature drying at 150℃ for 2 hours to obtain four composite thermal storage materials modified with different concentrations of nano-Al2O3 (2.5%, 5.0%, 7.5%, and 10%), which are named EP@2.5% Al2O3, EP@5.0% Al2O3, EP@7.5% Al2O3, and EP@10% Al2O3.

[0151] Example 8

[0152] The high thermal storage density stable thermochemical adsorption composite thermal storage material in this embodiment includes 46% by mass of modified expanded perlite and 54% by mass of a binary mixed salt of MgSO4 and MgCl2. The modified expanded perlite is modified with nano-alumina (γ phase, 20nm, MW=101.96), and the mass ratio of MgSO4 to MgCl2 is 6:4.

[0153] The preparation method of the high heat storage density stable thermochemical adsorption composite heat storage material in this embodiment is as follows:

[0154] Step 1: Drying expanded perlite: Weigh a certain amount of expanded perlite, wash it, and place it in a constant temperature drying oven to dry at 150℃ for 2 hours.

[0155] Step 2: Modification of expanded perlite: Different masses of nano-alumina were dispersed in deionized water and uniformly dispersed for 10 minutes using an ultrasonic processor to prepare four different concentrations (2.5%, 5.0%, 7.5%, and 10%) of nano-Al2O3 dispersions. The expanded perlite dried in Step 1 was immersed in the nano-Al2O3 dispersions and stirred for 30 minutes until homogeneous, so that the nano-alumina particles were evenly distributed on the surface of the expanded perlite. After filtering out excess liquid, the perlite was transferred to a drying oven and dried at 80°C for 2 hours. Finally, it was sintered in a tube furnace at 400°C for 1 hour to firmly bond the nano-alumina with the surface of the expanded perlite to form a high-strength surface layer, resulting in four different concentrations of Al2O3-modified expanded perlite.

[0156] Step 3: Inorganic salt mixing: Add MgSO4 and MgCl2 to deionized water in a ratio of 6:4 and stir to obtain a salt solution with a concentration of 25wt%.

[0157] Step 4: Prepare the suspension: Mix the modified expanded perlite obtained in Step 2 with the salt solution obtained in Step 3 to form a suspension, and then perform high-temperature impregnation of the solid-liquid mixture; the high-temperature impregnation temperature is 80℃ and the impregnation time is 24 hours.

[0158] Step 5, Drying: After filtering the suspension prepared in Step 4, place it in a drying oven for constant temperature drying at 150℃ for 2 hours to obtain four composite thermal storage materials modified with different concentrations of nano-Al2O3 (2.5%, 5.0%, 7.5%, and 10%), which are named EP@2.5% Al2O3, EP@5.0% Al2O3, EP@7.5% Al2O3, and EP@10% Al2O3.

[0159] Comparative Example 1

[0160] The high thermal storage density stable thermochemical adsorption composite thermal storage material in this embodiment includes 47% expanded perlite and 53% binary mixed salt of MgSO4 and MgCl2 by mass percentage. The expanded perlite is unmodified, and the mass ratio of MgSO4 to MgCl2 is divided into four types: 9:1, 8:2, 7:3, and 6:4.

[0161] The preparation method of the composite material includes matrix drying, solution preparation, high-temperature impregnation, filtration, and drying. A measured amount of expanded perlite was weighed and placed in a constant-temperature drying oven, dried at 150℃ for 2 hours to remove moisture and impurity gases. MgSO4 and MgCl2 were mixed in ratios (9:1, 8:2, 7:3, 6:4), and then deionized water was added and stirred to obtain a saturated salt solution (25wt%). The dried expanded perlite (EP) was then impregnated in solutions of different ratios, maintained at 80℃ under normal pressure for 24 hours to ensure the solution fully penetrated the pores of the expanded perlite. Finally, the expanded perlite was filtered from the solution and surface-washed with deionized water to remove surface-adhered salts, and then placed in a constant-temperature drying oven at 150℃ for 2 hours until the sample quality stabilized and no longer changed, ensuring complete removal of excess moisture. Based on this, expanded perlite / MgSO4-MgCl2 composite materials with different salt contents were obtained. According to the ratio of MgSO4 to MgCl2 during the impregnation process from high to low (9:1, 8:2, 7:3, 6:4), the four composite materials were named MCP1, MCP2, MCP3, and MCP4, respectively.

[0162] Comparative Example 2

[0163] For unmodified expanded perlite (EP), without impregnation with MgSO4 and MgCl2 solutions, the results in the attached figure show that the sample has a drawback: loss of water absorption properties.

[0164] Comparative Example 3

[0165] Replace the binary mixed salt in any one of Examples 1-8 with a monobasic salt, and the other implementation methods are the same as in any one of Examples 1-8 to obtain the finished products MCPS and MCPC. As can be seen from the results in the attached figure, the sample has a disadvantage: the water absorption rate is too high or too low.

[0166] Comparative Example 4

[0167] The hot impregnation in any of Examples 1-8 is replaced with vacuum impregnation, that is: first, the expanded perlite is placed in a vacuum pump and vacuumed, and then it is mixed with a mixed salt solution to prepare a composite thermal storage material solution. Other implementation methods are the same as any of Examples 1-8. This sample has the following disadvantages: the salt loading rate is low and the adsorption rate is 0.874 g / g.

[0168] Comparative Example 5

[0169] The hot impregnation in any of Examples 1-8 is replaced with room temperature impregnation, that is: the expanded perlite is not heated before mixing with the mixed salt solution. The other implementation methods are the same as any of Examples 1-8. The sample has the disadvantage of low salt loading rate.

[0170] The method for testing composite thermal storage materials according to the present invention is as follows:

[0171] The prepared high-density, stable thermochemical adsorption composite thermal storage material was subjected to adsorption performance tests, thermal storage performance tests, cycle stability tests, and strength tests. The adsorption performance of the composite thermal storage material was tested using a constant temperature and humidity chamber. The thermal storage performance was tested using differential scanning calorimetry (DSC). The physical properties of the composite thermal storage material were analyzed using X-ray diffraction (XRD). The cycle stability of the composite thermal storage material was tested using a constant temperature and humidity chamber for 30 cycles. The results are shown in Table 1.

[0172] Table 1: Performance Test Results of MCP4, EP@5%Al2O3, and EP@7.5%Si

[0173]

[0174] The performance parameters of MCP4 are as follows: salt loading rate of 132%, water absorption rate of 1.2 g / g, thermal storage density of 1116.3 kJ / kg, thermal storage temperature of 143.3℃, ​​structural strength of 7.668 kPa, structural stability of 97.07%, and stability after 30 cycles of 83.75%. The performance parameters of MCP1, MCP2, and MCP3 are similar.

[0175] The performance parameters of EP@5%Al2O3 are as follows: salt loading rate of 114%, water absorption rate of 1.28 g / g, heat storage density of 1123.5 kJ / kg, heat storage temperature of 141.3℃, structural strength of 10.346 kPa, structural stability of 99.53%, and stability after 30 cycles of 79.7%. The performance parameters of EP@2.5%Al2O3, EP@5%Al2O3, EP@7.5%Al2O3, and EP@10%Al2O3 are similar.

[0176] The performance parameters of EP@7.5%Si are as follows: salt loading rate of 121%, water absorption rate of 1.2 g / g, heat storage density of 1208.6 kJ / kg, heat storage temperature of 133.4℃, structural strength of 12.631 kPa, structural stability of 99.27%, and stability after 30 cycles of 83.3%. The high heat storage density composite thermochemical adsorption heat storage materials obtained by 10% modification, named EP@2.5%Si, EP@5%Si, and EP@10%Si, have similar performance parameters.

[0177] Among the three optimized materials obtained, EP@7.5%Si showed the best results due to its highest heat storage density, lowest heat storage temperature, best structural strength, and best overall structural and cycling stability. However, Al2O3 modification also yielded good results, significantly improving structural strength and stability, but slightly decreasing cycling stability.

[0178] like Figure 1 As shown, the preparation method of the high heat storage density composite thermochemical adsorption heat storage material provided by the present invention is simple; for example... Figure 2 As shown, the high heat storage density composite thermochemical adsorption heat storage material provided by this invention has a high and stable water absorption rate, which can reach 1.2 g / g-1.4 g / g; for example... Figure 3 As shown, the high thermal density composite thermochemical adsorption thermal storage material provided by this invention is a composite material obtained by physically mixing two salt materials and one porous material without any chemical reaction; as shown Figure 4 As shown, the high heat storage density composite thermochemical adsorption heat storage material provided by this invention has a heat storage density of 1208.6 kJ / kg, but its peak temperature shows multiple peaks, indicating that heat storage is carried out in steps and stages, and 133.4℃ is required to complete the heat storage; as Figure 5 As shown, the high heat storage density composite thermochemical adsorption heat storage material provided by this invention exhibits a gradual decrease in adsorption and desorption mass relative to the initial value. After 30 cycles, it reaches approximately 80% of the initial adsorption and desorption values. The performance of EP@5.0%Al2O3 and EP@7.5%Si after 30 cycles is approximately 79.7% and 83.3% of their initial adsorption and desorption values, respectively, representing a decrease of only 4.05% and 0.45% compared to unmodified MCP4. Figure 6 As shown, the high heat storage density composite thermochemical adsorption heat storage material provided by this invention has excellent compressive strength and is not easily broken into pieces; for example... Figure 7 and Figure 8 As shown, the high heat storage density composite thermochemical adsorption heat storage material provided by the present invention has excellent structural strength and structural stability, and is not prone to powder shedding.

[0179] The above are merely preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any embodiment that achieves the technical effect of the present invention by the same or similar means should fall within the protection scope of the present invention. The above technical solutions only embody the preferred technical solutions of the present invention. Any modifications that may be made by those skilled in the art to certain parts thereof embody the principles of the present invention and fall within the protection scope of the present invention.

Claims

1. A high-density, stable thermochemical adsorption composite thermal storage material, characterized in that: It comprises 54%-57% mixed salt and 43%-46% porous material by mass, wherein the mixed salt is MgSO4 and MgCl2, and the mass ratio of MgSO4 to MgCl2 is 9:1-6:4, and the porous material is modified expanded perlite.

2. The high heat storage density stable thermochemical adsorption composite heat storage material according to claim 1, characterized in that: The mixed salt is composed of MgSO4 and MgCl2 in a mass ratio of 9:1, 8:2, 7:3, or 6:

4.

3. The high heat storage density stable thermochemical adsorption composite thermal storage material according to claim 1 or 2, characterized in that: The modified expanded perlite is expanded perlite modified with 3-aminopropyltriethoxysilane (analytical grade, MW = 221.37).

4. The high heat storage density stable thermochemical adsorption composite heat storage material according to claim 3, characterized in that: The expanded perlite is expanded perlite modified with nano-alumina (γ phase, 20 nm, MW = 101.96).

5. A method for preparing a high-density, stable thermochemical adsorption composite thermal storage material, characterized in that: The method for preparing the high heat storage density stable thermochemical adsorption composite heat storage material according to any one of claims 1-4 includes the following steps: modifying expanded perlite, preparing a composite inorganic salt solution, mixing the modified expanded perlite with the composite inorganic salt solution and impregnating at high temperature, and drying at a constant temperature.

6. The preparation method of the high heat storage density stable thermochemical adsorption composite heat storage material according to claim 5, characterized in that: The preparation steps for modifying expanded perlite with 3-aminopropyltriethoxysilane (analytical grade, MW = 221.37) include the following: Step 1: Drying expanded perlite: Weigh a certain amount of expanded perlite, wash it, and then place it in a constant temperature drying oven to dry. Step 2, Modification of Expanded Perlite: Dissolve 3-aminopropyltriethoxysilane in ethanol and stir until homogeneous to obtain a silane coupling agent solution. Add the dried expanded perlite from Step 1 to the silane coupling agent solution and stir to ensure that 3-aminopropyltriethoxysilane molecules are evenly distributed on the surface of the expanded perlite. Then, allow it to stand at room temperature and place it in a drying oven for gradient drying to promote the formation of covalent bonds between 3-aminopropyltriethoxysilane and the surface of the expanded perlite, thus obtaining modified expanded perlite. Step 3: Inorganic salt mixing: Add MgSO4 and MgCl2 to deionized water according to the specified ratio and stir to obtain a salt solution with a concentration of 25wt%. Step 4: Prepare the suspension: Mix the modified expanded perlite obtained in Step 2 with the salt solution obtained in Step 3 to form a suspension, and then perform high-temperature impregnation of the solid-liquid mixture. Step 5, Drying: After filtering the suspension prepared in Step 4, place it in a drying oven and dry at a constant temperature to obtain the finished product.

7. The preparation method of the high heat storage density stable thermochemical adsorption composite heat storage material according to claim 6, characterized in that: The solubility of 3-aminopropyltriethoxysilane in the silane coupling agent solution is 2.5% to 10%.

8. The preparation method of the high heat storage density stable thermochemical adsorption composite thermal storage material according to claim 6 or 7, characterized in that: The drying temperature in step one is 150℃ and the drying time is 2 hours; the gradient drying in step two includes drying at 80℃ for 2 hours, and then heating to 120℃ and holding for 1 hour; the high-temperature impregnation temperature in step four is 80℃ and the impregnation time is 24 hours; the constant temperature drying temperature in step five is 150℃ and the drying time is 2 hours.

9. The preparation method of the high heat storage density stable thermochemical adsorption composite heat storage material according to claim 5, characterized in that: The preparation steps for modifying expanded perlite with nano-alumina (γ phase, 20 nm, MW = 101.96) include: Step 1: Drying expanded perlite: Weigh a certain amount of expanded perlite, wash it, and then place it in a constant temperature drying oven to dry. Step 2, Modification of Expanded Perlite: Disperse nano-alumina in deionized water and use an ultrasonic processor to uniformly disperse it to prepare a nano-alumina dispersion. Immerse the expanded perlite dried in Step 1 in the nano-alumina dispersion and stir evenly to ensure that the nano-alumina particles are evenly distributed on the surface of the expanded perlite. After filtering out excess liquid, transfer it to a drying oven to dry. Finally, calcine it in a tube furnace to firmly bond the nano-alumina with the surface of the expanded perlite to form a high-strength surface layer, thus obtaining modified expanded perlite. Step 3: Inorganic salt mixing: Add MgSO4 and MgCl2 to deionized water according to the specified ratio and stir to obtain a salt solution with a concentration of 25wt%. Step 4: Prepare the suspension: Mix the modified expanded perlite obtained in Step 2 with the solution in Step 3 to form a suspension, and then perform high-temperature impregnation of the solid-liquid mixture. Step 5: Drying: After filtering the suspension prepared in Step 4, place it in a constant temperature drying oven to dry and obtain the finished product.

10. The preparation method of the high heat storage density stable thermochemical adsorption composite heat storage material according to claim 9, characterized in that: The concentration of nano-alumina in the nano-alumina dispersion is 2.5% to 10%; the drying temperature in step one is 150℃ and the drying time is 2 hours; in step two, the ultrasonic dispersion time is 10 minutes, the stirring time is 30 minutes, the drying temperature is 80℃ and the drying time is 2 hours, and the calcination temperature is 400℃ and the calcination time is 1 hour; the high-temperature impregnation temperature in step four is 80℃ and the time is 24 hours; the constant temperature drying temperature in step five is 150℃ and the drying time is 2 hours.

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