Solid heat storage material and preparation method thereof

Abstract

The present invention specifically relates to a solid heat storage material and a preparation method thereof. The technical solution is as follows: magnesite tailings fine powder, bauxite tailings fine powder, quartz sand fine powder, used magnesium carbon brick fine powder, and barium sulfate fine powder are mixed to obtain a premixed powder. Magnesite tailings particles with a particle size of 5 to 3 mm, bauxite tailings particles with a particle size of 3 to 1 mm, quartz sand particles with a particle size of 3 to 1 mm, and magnesite tailings particles with a particle size of ≤1 mm are mixed to obtain a granular material. The granular material and the premixed powder are mixed to obtain a mixture; polyvinyl alcohol solution is added, the mixture is evenly mixed, pressed and formed, dried, and then heat-treated at 1300 to 1500°C for 5 to 8 hours to obtain a solid heat storage material. The solid heat storage material prepared by the present invention has high thermal conductivity, large heat storage capacity, high thermal shock stability, and high compressive strength.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid heat storage materials, and specifically relates to a solid heat storage material and a preparation method thereof. Background Art

[0002] Thermal storage technology has attracted significant attention due to its multiple advantages: it not only promotes the use of renewable energy and effectively reduces greenhouse gas emissions; it also stores waste heat, improving primary energy efficiency; and it also offers peak load shifting, helping to maintain stable grid operation. The development of thermal storage technology enables the efficient utilization of renewable energy sources such as solar energy, which suffer from poor stability and uneven spatial and temporal distribution, thereby alleviating pollution and improving energy security. Currently, commonly used thermal storage technologies in engineering include solid thermal storage, water thermal storage, and phase change thermal storage.

[0003] Furthermore, the rapid increase in solid waste, such as post-consumer MgO-C bricks and tailings, generated by industries like industry and construction has placed enormous pressure on land resources and environmental protection. To alleviate this problem, a common practice is to use these solid wastes, such as post-consumer MgO-C bricks and tailings, to fill abandoned tunnels. However, how to fully utilize and leverage the unique composition and structure of these solid wastes has become a major concern for those skilled in the relevant fields.

[0004] The patented technology "A heat storage material made from solid waste such as fly ash and slag (CN202111147752.7)" seals molten salt in the heat storage material, which increases the service life of the heat storage material. However, the thermal shock stability and strength of the heat storage material are poor, which limits its large-scale application.

[0005] The patented technology "A method for preparing a solid thermal storage material and a solid thermal storage material (CN202111618298.9)" uses solid waste such as fly ash, boiler slag, and desulfurization gypsum to prepare a solid thermal storage material. However, the prepared thermal storage material has problems such as low mechanical strength, low thermal conductivity, and poor thermal shock stability.

[0006] The patented technology "A solid thermal storage material, preparation method and application (CN201710172467.8)" is low-cost and has an adjustable thermal conductivity, but its compressive strength and thermal storage capacity are relatively low.

[0007] The patented technology "A solid thermal storage material and its preparation method (CN202310588356.0)" has a simple preparation process, low cost, and high thermal storage capacity, but its thermal shock stability is poor;

[0008] The patented technology of "Solid heat storage material and its preparation method and application (202310880468.3)" uses different raw materials to prepare solid heat storage materials. Although it reduces production costs and improves the heat storage capacity and refractoriness of the heat storage body, its compressive strength is relatively low.

[0009] In summary, the solid thermal storage materials in the existing technology have the following technical defects: poor thermal shock stability, low thermal conductivity, low compressive strength and poor thermal storage capacity, as well as insufficient utilization of solid waste and tailings. Summary of the Invention

[0010] The present invention aims to solve the deficiencies of the prior art and aims to provide a method for preparing solid thermal storage materials using solid waste and tailings. The solid thermal storage materials prepared by this method have high thermal shock stability, high thermal conductivity, large heat storage capacity and high compressive strength.

[0011] To achieve the above object, the specific steps of the technical solution adopted by the present invention are:

[0012] Step 1: 17-30 wt% of magnesite tailings fine powder, 20-35 wt% of bauxite tailings fine powder, 20-35 wt% of quartz sand fine powder, 10-15 wt% of used magnesia carbon brick fine powder and 7-15 wt% of barium sulfate fine powder are mixed to obtain a premixed powder.

[0013] Step 2: 10-18 wt% of magnesite tailing particles with a particle size of 5-3 mm, 15-25 wt% of bauxite tailing particles with a particle size of 3-1 mm, 20-30 wt% of quartz sand particles with a particle size of 3-1 mm, and 35-45 wt% of magnesite tailing particles with a particle size of ≤1 mm are mixed to obtain a granular material.

[0014] Step 3: Mix 65-80 wt% of the granular material and 20-35 wt% of the premixed powder to obtain a mixture; add 8-14 wt% of polyvinyl alcohol solution to the mixture, mix evenly, press into shape at 80-120 MPa, dry at 80-110°C for 12-24 hours, and then heat treat at 1300-1500°C for 5-8 hours to obtain a solid thermal storage material.

[0015] The chemical composition of the magnesite tailings fine powder is: MgO content is greater than 47wt%, SiO2 content is greater than 3wt%; the particle size of the magnesite tailings fine powder is less than 0.088mm; the chemical composition of the magnesite tailings particles is the same as the chemical composition of the magnesite tailings fine powder.

[0016] The chemical composition of the bauxite tailings fine powder is: the content of Al2O3 is greater than 45wt.%, the content of SiO2 is greater than 30wt%; the particle size of the bauxite tailings fine powder is less than 0.088mm; the chemical composition of the bauxite tailings particles is the same as the chemical composition of the bauxite tailings fine powder.

[0017] The chemical composition of the quartz sand fine powder is: SiO2 content is greater than 95wt%, Al2O3 content is less than 1.50wt%; the particle size of the quartz sand fine powder is less than 0.088mm; the chemical composition of the quartz sand particles is the same as the chemical composition of the quartz sand fine powder.

[0018] The chemical composition of the used magnesia carbon brick fine powder is: MgO content greater than 70wt%, Al2O3 content less than 3wt%, SiC content greater than 5wt%, and C content greater than 8wt%. The used magnesia carbon brick fine powder is: discarded used magnesia carbon bricks are crushed, deironed, hydrated, dried, and then sieved, and the particle size of the used magnesia carbon brick fine powder is less than 0.088mm.

[0019] The BaSO4 content of the barium sulfate fine powder is greater than 99 wt.%.

[0020] The concentration of the polyvinyl alcohol solution is 5 wt %.

[0021] Due to the adoption of the above technical solution, the present invention has the following positive effects compared with the prior art:

[0022] (1) Because the present invention utilizes the accumulation of particles of different particle sizes between different raw materials, during the heat treatment process at 1300°C to 1500°C, the magnesite tailings react with raw materials such as quartz sand in situ to form forsterite, strengthening the bond between the different raw material particles. Furthermore, forsterite has a high specific heat capacity. Therefore, the solid thermal storage material prepared by the present invention has a high thermal storage capacity and high compressive strength.

[0023] (2) The present invention makes full use of the high-temperature reactivity between different raw materials. Magnesium ore tailings react with raw materials such as quartz sand in situ to form forsterite, and barium sulfate reacts with raw materials such as bauxite tailings in situ to form celsium feldspar, thereby strengthening the bonding between different particles of different raw materials. The volume expansion generated by the in-situ formation of forsterite and celsium feldspar reduces the pore size between particles, greatly avoiding the high-temperature oxidation of silicon carbide, carbon, etc. in the fine powder of magnesium carbon bricks after use. The high thermal shock properties of forsterite, celsium feldspar, silicon carbide, carbon and small pore structure characteristics give the solid thermal storage material high thermal shock stability. Therefore, the solid thermal storage material prepared by the present invention has high compressive strength and thermal shock stability.

[0024] (3) The present invention utilizes the in-situ formation of forsterite and celsium feldspar to generate volume expansion and reduce the pore size between particles, thereby greatly avoiding the high-temperature oxidation of silicon carbide, carbon, etc. in the fine powder of magnesium carbon bricks after use, thereby maintaining its high thermal conductivity. Therefore, the solid thermal storage material prepared by the present invention has excellent thermal conductivity.

[0025] The solid thermal storage material prepared by the present invention has been tested: the volume density is ≥3.00g / cm 3 Thermal conductivity (800-1000℃, average value) ≥26W / (m·K); Specific heat capacity (800-1000℃, average value) ≥1.8J / (g·K); Thermal shock stability ≥15 times (1100℃, air cooling); Compressive strength is 170~200MPa.

[0026] Therefore, the solid heat storage material prepared by the present invention has high thermal conductivity, large heat storage capacity, high thermal shock stability and high compressive strength. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with specific embodiments, which does not limit the scope of protection thereof.

[0028] A solid heat storage material and its preparation method. The preparation method described in this specific embodiment is:

[0029] Step 1: 17-30 wt% of magnesite tailings fine powder, 20-35 wt% of bauxite tailings fine powder, 20-35 wt% of quartz sand fine powder, 10-15 wt% of used magnesia carbon brick fine powder and 7-15 wt% of barium sulfate fine powder are mixed to obtain a premixed powder.

[0030] Step 2: 10-18 wt% of magnesite tailing particles with a particle size of 5-3 mm, 15-25 wt% of bauxite tailing particles with a particle size of 3-1 mm, 20-30 wt% of quartz sand particles with a particle size of 3-1 mm, and 35-45 wt% of magnesite tailing particles with a particle size of ≤1 mm are mixed to obtain a granular material.

[0031] Step 3: Mix 65-80 wt% of the granular material and 20-35 wt% of the premixed powder to obtain a mixture; add 8-14 wt% of polyvinyl alcohol solution to the mixture, mix evenly, press into shape at 80-120 MPa, dry at 80-110°C for 12-24 hours, and then heat treat at 1300-1500°C for 5-8 hours to obtain a solid thermal storage material.

[0032] The chemical composition of the magnesite tailings fine powder is: MgO content is greater than 47wt%, SiO2 content is greater than 3wt%;

[0033] The chemical composition of the bauxite tailings fine powder is: Al2O3 content is greater than 45wt.%, SiO2 content is greater than 30wt%;

[0034] The chemical composition of the quartz sand fine powder is: the content of SiO2 is greater than 95wt%, and the content of Al2O3 is less than 1.50wt%;

[0035] The chemical composition of the used magnesia carbon brick fine powder is as follows: MgO content is greater than 70wt%, Al2O3 content is less than 3wt%, SiC content is greater than 5wt%, and C content is greater than 8wt%.

[0036] In this specific implementation mode:

[0037] The particle size of the magnesite tailings fine powder is less than 0.088 mm; the chemical composition of the magnesite tailings particles is the same as the chemical composition of the magnesite tailings fine powder;

[0038] The particle size of the bauxite tailings fine powder is less than 0.088 mm; the chemical composition of the bauxite tailings particles is the same as the chemical composition of the bauxite tailings fine powder;

[0039] The particle size of the quartz sand fine powder is less than 0.088 mm; the chemical composition of the quartz sand particles is the same as the chemical composition of the quartz sand fine powder;

[0040] The used magnesia carbon brick fine powder is obtained by crushing, deironing, hydrating, drying and then screening the discarded used magnesia carbon bricks. The particle size of the used magnesia carbon brick fine powder is less than 0.088mm.

[0041] The BaSO4 content of the barium sulfate fine powder is greater than 99wt.%;

[0042] The concentration of the polyvinyl alcohol solution is 5 wt %.

[0043] The details will not be described in detail in the embodiments.

[0044] Example 1

[0045] A solid heat storage material and its preparation method. The preparation method described in this embodiment is:

[0046] Step 1: 26 wt% of magnesite tailings fine powder, 30 wt% of bauxite tailings fine powder, 22 wt% of quartz sand fine powder, 15 wt% of used magnesia carbon brick fine powder and 7 wt% of barium sulfate fine powder are mixed to obtain a premixed powder.

[0047] Step 2: 14 wt% of magnesite tailing particles with a particle size of 5 to 3 mm, 24 wt% of bauxite tailing particles with a particle size of 3 to 1 mm, 20 wt% of quartz sand particles with a particle size of 3 to 1 mm, and 42 wt% of magnesite tailing particles with a particle size of ≤1 mm are mixed to obtain a granular material.

[0048] Step 3: Mix 65wt% of the granular material and 35wt% of the premixed powder to obtain a mixture; add 14wt% polyvinyl alcohol solution of the mixture, mix evenly, press into shape under 80MPa conditions, then dry at 80℃ for 24h, and then heat treat at 1300℃ for 8h to obtain a solid thermal storage material.

[0049] The chemical composition of the magnesite tailings fine powder is: MgO content is 47.3wt%, SiO2 content is 3.1wt%;

[0050] The chemical composition of the bauxite tailings fine powder is: Al2O3 content is 45.6wt%, SiO2 content is 30.5wt%;

[0051] The chemical composition of the quartz sand fine powder is: SiO2 content is 95.2wt%, Al2O3 content is 1.31wt%;

[0052] The chemical composition of the used magnesia carbon brick fine powder is as follows: MgO content is 70.8wt%, Al2O3 content is 2.8wt%, SiC content is 5.2wt%, and C content is 8.3wt%.

[0053] The solid thermal storage material prepared in this embodiment was tested: the volume density was 3.1g / cm 3 Thermal conductivity (800-1000℃, average value) 32W / (m·K); specific heat capacity (800-1000℃, average value) 2.1J / (g·K); thermal shock stability 15 times (1100℃, air cooling); compressive strength 170MPa.

[0054] Example 2

[0055] A solid heat storage material and its preparation method. The preparation method described in this embodiment is:

[0056] Step 1: 20 wt% of magnesite tailings fine powder, 35 wt% of bauxite tailings fine powder, 25 wt% of quartz sand fine powder, 10 wt% of used magnesia carbon brick fine powder and 10 wt% of barium sulfate fine powder are mixed to obtain a premixed powder.

[0057] Step 2: 16 wt% of magnesite tailing particles with a particle size of 5 to 3 mm, 25 wt% of bauxite tailing particles with a particle size of 3 to 1 mm, 24 wt% of quartz sand particles with a particle size of 3 to 1 mm, and 35 wt% of magnesite tailing particles with a particle size of ≤1 mm are mixed to obtain a granular material.

[0058] Step 3: Mix 80 wt% of the granular material and 20 wt% of the premixed powder to obtain a mixture; add 10 wt% of polyvinyl alcohol solution to the mixture, mix evenly, press into shape under 100 MPa, dry at 90°C for 20 hours, and then heat treat at 1400°C for 7 hours to obtain a solid thermal storage material.

[0059] The chemical composition of the magnesite tailings fine powder is: MgO content is 47.1wt%, SiO2 content is 3.2wt%;

[0060] The chemical composition of the bauxite tailings fine powder is: Al2O3 content is 45.4wt%, SiO2 content is 30.6wt%;

[0061] The chemical composition of the quartz sand fine powder is: SiO2 content is 95.6wt%, Al2O3 content is 1.35wt%;

[0062] The chemical composition of the used magnesia carbon brick fine powder is as follows: MgO content is 71wt%, Al2O3 content is 2.85wt%, SiC content is 5.1wt%, and C content is 8.5wt%.

[0063] The solid thermal storage material prepared in this embodiment was tested: the volume density is 3.3g / cm 3 Thermal conductivity (800-1000℃, average value) 26W / (m·K); specific heat capacity (800-1000℃, average value) 1.8J / (g·K); thermal shock stability 20 times (1100℃, air cooling); compressive strength 178MPa.

[0064] Example 3

[0065] A solid heat storage material and its preparation method. The preparation method described in this embodiment is:

[0066] Step 1: 30 wt% of magnesite tailings fine powder, 25 wt% of bauxite tailings fine powder, 20 wt% of quartz sand fine powder, 12 wt% of used magnesia carbon brick fine powder and 13 wt% of barium sulfate fine powder are mixed to obtain a premixed powder.

[0067] Step 2: 10 wt% of magnesite tailing particles with a particle size of 5 to 3 mm, 18 wt% of bauxite tailing particles with a particle size of 3 to 1 mm, 27 wt% of quartz sand particles with a particle size of 3 to 1 mm, and 45 wt% of magnesite tailing particles with a particle size of ≤1 mm are mixed to obtain a granular material.

[0068] Step 3: Mix 75 wt% of the granular material and 25 wt% of the premixed powder to obtain a mixture; add 8 wt% of polyvinyl alcohol solution to the mixture, mix evenly, press into shape under 110 MPa, dry at 100°C for 16 hours, and then heat treat at 1450°C for 6 hours to obtain a solid thermal storage material.

[0069] The chemical composition of the magnesite tailings fine powder is: MgO content is 48wt%, SiO2 content is 3.9wt%;

[0070] The chemical composition of the bauxite tailings fine powder is: Al2O3 content is 46wt.%, SiO2 content is 31wt%;

[0071] The chemical composition of the quartz sand fine powder is: SiO2 content is 95.8wt%, Al2O3 content is 1.38wt%;

[0072] The chemical composition of the used magnesia carbon brick fine powder is as follows: MgO content is 70.7wt%, Al2O3 content is 2.9wt%, SiC content is 5.7wt%, and C content is 8.8wt%.

[0073] The solid thermal storage material prepared in this embodiment was tested: the volume density is 3.2g / cm 3 Thermal conductivity (800-1000℃, average value) 29W / (m·K); specific heat capacity (800-1000℃, average value) 2.3J / (g·K); thermal shock stability 18 times (1100℃, air cooling); compressive strength 186MPa.

[0074] Example 4

[0075] A solid heat storage material and its preparation method. The preparation method described in this embodiment is:

[0076] Step 1: 17 wt% of magnesite tailings fine powder, 20 wt% of bauxite tailings fine powder, 35 wt% of quartz sand fine powder, 13 wt% of used magnesia carbon brick fine powder and 15 wt% of barium sulfate fine powder are mixed to obtain a premixed powder.

[0077] Step 2: 18 wt% of magnesite tailing particles with a particle size of 5 to 3 mm, 15 wt% of bauxite tailing particles with a particle size of 3 to 1 mm, 30 wt% of quartz sand particles with a particle size of 3 to 1 mm, and 37 wt% of magnesite tailing particles with a particle size of ≤1 mm are mixed to obtain a granular material.

[0078] Step 3: Mix 70 wt% of the granular material and 30 wt% of the premixed powder to obtain a mixture; add 12 wt% of polyvinyl alcohol solution to the mixture, mix evenly, press into shape under 120 MPa, dry at 110°C for 12 hours, and then heat treat at 1500°C for 5 hours to obtain a solid thermal storage material.

[0079] The chemical composition of the magnesite tailings fine powder is: MgO content is 48.5wt%, SiO2 content is 4wt%;

[0080] The chemical composition of the bauxite tailings fine powder is: Al2O3 content is 47wt.%, SiO2 content is 32wt%;

[0081] The chemical composition of the quartz sand fine powder is: SiO2 content is 96wt%, Al2O3 content is 1.3wt%;

[0082] The chemical composition of the used magnesia carbon brick fine powder is as follows: MgO content is 71.7wt%, Al2O3 content is 2.89wt%, SiC content is 6.2wt%, and C content is 9wt%.

[0083] The solid thermal storage material prepared in this embodiment was tested: the volume density is 3.5g / cm 3 Thermal conductivity (800-1000℃, average value) 35W / (m·K); specific heat capacity (800-1000℃, average value) 2.4J / (g·K); thermal shock stability 22 times (1100℃, air cooling); compressive strength 200MPa.

[0084] Compared with the prior art, this embodiment has the following positive effects:

[0085] (1) Because this embodiment utilizes the accumulation of particles of different particle sizes between different raw materials, during the heat treatment process at 1300°C to 1500°C, the magnesite tailings react with raw materials such as quartz sand in situ to form forsterite, strengthening the bond between the different raw material particles. Furthermore, forsterite has a high specific heat capacity. Therefore, the solid thermal storage material prepared in this embodiment has a high thermal storage capacity and high compressive strength.

[0086] (2) This specific embodiment makes full use of the high-temperature reactivity between different raw materials. Magnesium ore tailings react with raw materials such as quartz sand in situ to form forsterite, and barium sulfate reacts with raw materials such as bauxite tailings in situ to form celsium feldspar, thereby strengthening the bonding between different particles of different raw materials. The volume expansion caused by the in-situ formation of forsterite and celsium feldspar reduces the pore size between particles, greatly avoiding the high-temperature oxidation of silicon carbide, carbon, etc. in the fine powder of magnesium carbon bricks after use. The high thermal shock properties of forsterite, celsium feldspar, silicon carbide, carbon and small pore structure characteristics give the solid thermal storage material high thermal shock stability. Therefore, the solid thermal storage material prepared by this specific embodiment has high compressive strength and thermal shock stability.

[0087] (3) This embodiment utilizes the in-situ formation of forsterite and celsium feldspar to generate volume expansion, reducing the size of the pores between the particles. This significantly avoids the high-temperature oxidation of silicon carbide, carbon, and other components in the magnesium-carbon brick fine powder after use, maintaining its high thermal conductivity. Therefore, the solid thermal storage material prepared in this embodiment has excellent thermal conductivity.

[0088] The solid thermal storage material prepared in this embodiment has been tested: the volume density is ≥3.00g / cm 3 Thermal conductivity (800-1000℃, average value) ≥26W / (m·K); Specific heat capacity (800-1000℃, average value) ≥1.8J / (g·K); Thermal shock stability ≥15 times (1100℃, air cooling); Compressive strength is 170~200MPa.

[0089] The test standards for the performance indicators involved in this specific implementation method are: bulk density is measured in accordance with GB / T2999-2016; thermal conductivity is measured in accordance with GB / T5990-2021 standard; specific heat capacity is measured in accordance with GB / T5990-2021; thermal shock stability is measured in accordance with GB / T30873-2014; and compressive strength is measured in accordance with GB / T5072-2008.

[0090] Therefore, the solid thermal storage material prepared in this specific embodiment has high thermal conductivity, large heat storage capacity, high thermal shock stability and high compressive strength.

Claims

1. A method for preparing a solid thermal storage material, characterized in that The steps of the preparation method are: Step 1: 17-30 wt% of magnesite tailings fine powder, 20-35 wt% of bauxite tailings fine powder, 20-35 wt% of quartz sand fine powder, 10-15 wt% of used magnesia carbon brick fine powder and 7-15 wt% of barium sulfate fine powder are mixed to obtain a premixed powder; Step 2: 10-18 wt% of magnesite tailing particles with a particle size of 5-3 mm, 15-25 wt% of bauxite tailing particles with a particle size of 3-1 mm, 20-30 wt% of quartz sand particles with a particle size of 3-1 mm, and 35-45 wt% of magnesite tailing particles with a particle size of ≤1 mm are mixed to obtain a granular material; Step 3: Mix 65-80 wt% of the granular material and 20-35 wt% of the premixed powder to obtain a mixture; add 8-14 wt% of polyvinyl alcohol solution to the mixture, mix evenly, press into shape at 80-120 MPa, dry at 80-110°C for 12-24 hours, and then heat treat at 1300-1500°C for 5-8 hours to obtain a solid thermal storage material.

2. The method for preparing a solid thermal storage material according to claim 1, wherein: The chemical composition of the magnesite tailings fine powder is: MgO content is greater than 47wt%, SiO2 content is greater than 3wt%; the particle size of the magnesite tailings fine powder is less than 0.088mm; the chemical composition of the magnesite tailings particles is the same as the chemical composition of the magnesite tailings fine powder.

3. The method for preparing a solid thermal storage material according to claim 1, wherein: The chemical composition of the bauxite tailings fine powder is: the content of Al2O3 is greater than 45wt.%, the content of SiO2 is greater than 30wt%; the particle size of the bauxite tailings fine powder is less than 0.088mm; the chemical composition of the bauxite tailings particles is the same as the chemical composition of the bauxite tailings fine powder.

4. The method for preparing a solid thermal storage material according to claim 1, wherein: The chemical composition of the quartz sand fine powder is: SiO2 content is greater than 95wt%, Al2O3 content is less than 1.50wt%; the particle size of the quartz sand fine powder is less than 0.088mm; the chemical composition of the quartz sand particles is the same as the chemical composition of the quartz sand fine powder.

5. The method for preparing a solid thermal storage material according to claim 1, wherein: The chemical composition of the used magnesia carbon brick fine powder is: MgO content greater than 70wt%, Al2O3 content less than 3wt%, SiC content greater than 5wt%, and C content greater than 8wt%. The used magnesia carbon brick fine powder is: discarded used magnesia carbon bricks are crushed, deironed, hydrated, dried, and then sieved, and the particle size of the used magnesia carbon brick fine powder is less than 0.088mm.

6. The method for preparing a solid thermal storage material according to claim 1, wherein: The BaSO4 content of the barium sulfate fine powder is greater than 99 wt.%.

7. The method for preparing a solid thermal storage material according to claim 1, wherein: The concentration of the polyvinyl alcohol solution is 5 wt %.

8. A solid heat storage material, characterized in that The solid heat storage material is a solid heat storage material prepared by the method for preparing a solid heat storage material according to any one of claims 1 to 7.