Solar energy absorption and storage ceramic based on iron-rich metallurgical slag and preparation method thereof

Abstract

The application relates to a solar energy absorption and storage ceramic based on iron-rich metallurgical slag and a preparation method thereof, and the technical scheme is as follows: 50-70wt% of iron-rich metallurgical slag, 15-35wt% of fused magnesia and 3-16wt% of industrial alumina are mixed, or 60-80wt% of iron-rich metallurgical slag and 20-40wt% of fused magnesia are mixed to obtain a mixture, the mixture is wet ground to obtain a slurry; the slurry is dried, ground and screened, and is pressed into a green body; the green body is heated to 1250-1500 DEG C in an air atmosphere, is kept for 1-4h, is cooled in a furnace, and the solar energy absorption and storage ceramic based on the iron-rich metallurgical slag is prepared. The application has the characteristics of low raw material cost, simple process and utilization of large industrial solid waste; the prepared solar energy absorption and storage ceramic based on the iron-rich metallurgical slag has the advantages of high light-heat conversion efficiency, high heat storage density, high mechanical strength, long service life, high use temperature, good thermal shock resistance and excellent high-temperature wear resistance.

Description

Technical Field

[0001] This invention belongs to the field of solar energy absorption and storage ceramic technology. Specifically, it relates to a solar energy absorption and storage ceramic based on iron-rich metallurgical slag and its preparation method. Background Technology

[0002] Solar thermal power generation, with its advantages in energy storage and peak shaving, has become a key technology for building new power systems. Existing commercial power plants mostly use molten salt as the heat transfer and storage medium, but it suffers from high corrosivity, easy solidification, a narrow operating temperature range (<600℃), and leakage risks, making it difficult to meet the high-temperature and high-efficiency requirements of next-generation systems. In contrast, solid particles offer advantages such as high operating temperature (>800℃), stable physicochemical properties, no solidification risk, and high environmental safety, and are considered an important development direction for solar thermal technology. Ideal solid particles should possess high light absorption, high heat storage density, and high thermal conductivity, as well as excellent high-temperature structural stability, thermal shock resistance, and wear resistance to adapt to harsh cyclic transport and impact conditions. Therefore, the development of high-performance solid particle materials has become a research hotspot in this field.

[0003] While solar thermal absorption and storage ceramic particle materials are developing towards high performance and low cost, the global metallurgical industry generates a large amount of iron-rich metallurgical slag annually. This type of solid waste not only occupies land during storage but also poses environmental hazards such as dust dispersion and heavy metal dissolution and seepage. Therefore, researchers have been developing and researching the preparation of solar thermal absorption and storage ceramic particles using metallurgical slag. Yang et al. (Lili Yang, Mingli Zhang, Yimin Zhang, etc., Environmentally responsible steel-slag-based solid particles for highly efficient and durable solar selective absorptance and thermal storage[J]. Journal of Cleaner Production, 2024, 434: 139962.) prepared solid particles using steel slag as a matrix and adding various oxides. Although they showed high absorption rates, the additive system was complex, and the relatively low melting point of the material resulted in a low service temperature.

[0004] Xu et al. (Xiaohong Xu, Jianli Ma, Yali Wang etc., Preparation and characterization of solar absorption and thermal storage integrated ceramics from calcium and iron-richsteelslag[J]. Ceramics International, 2023, 49: 17228-17237.) Synthesis of MgFe2O4 / CaMgSiO4 by adding magnesite to calcium- and iron-rich steel slag. The ceramics have a solar absorption rate of only 84.7%, and their photothermal conversion efficiency is still insufficient, resulting in poor mechanical properties.

[0005] Currently, there is also a large amount of research on preparing solar energy absorption and storage ceramic particles using other materials, such as: The patent application CN111253158B, entitled "Integrated Solar Thermal Power Generation Absorption / Storage Corundum / SiC Ceramic Material and its Preparation Method Thereof," discloses a method for preparing thermal absorption and storage ceramics using silicon carbide (SiC) and corundum as the main raw materials. While this method utilizes the high thermal conductivity of silicon carbide to improve the material's heat transfer rate and mechanical strength, the high silicon carbide content (50-90%) increases the raw material cost. Furthermore, the sintering process requires a complex "powder embedding process" (using graphite powder to create a reducing atmosphere) to prevent SiC oxidation, resulting in a cumbersome process and difficulty in achieving large-scale continuous production. Simultaneously, the material's infrared emissivity is over 99%, leading to severe radiative heat loss at high temperatures, making it difficult to meet the spectral selectivity requirements of "high absorption-low emission" for the medium in solar thermal systems, resulting in low photothermal conversion efficiency.

[0006] CN113831135A discloses a method for preparing spherical solar thermal absorption and storage ceramics with in-situ generated cordierite-bonded SiC as the main raw material and additives such as black corundum, talc, and cobalt oxide. While this method achieves high solar energy absorption (>95%) and thermal conductivity (8.0-8.5 W / (m·K)) by introducing highly thermally conductive silicon carbide (60-80%) and black oxide additives, it suffers from high raw material costs (heavily dependent on expensive silicon carbide powder and cobalt oxide colorants), and the material is prone to oxidation, wear, and has insufficient mechanical strength and a short service life.

[0007] The patented technology, "A Full-Spectrum Photothermal Conversion Thermal Storage Material and Its Preparation Method (CN109735310B)," uses aluminum nitrate, calcium carbonate, and cobalt nitrate as solutes to prepare composite calcium-based thermochemical thermal storage particles with a porous structure via a sol-gel method. While this material achieves the coupling of photothermal conversion and thermochemical thermal storage functions and possesses a wide spectral absorption range, it requires maintaining a loose and porous microstructure to preserve thermochemical reactivity. This results in significantly lower mechanical strength compared to dense ceramics, making it highly susceptible to wear and pulverization during circulating fluidization, and thus unsuitable for the harsh operating conditions of particle receivers. Summary of the Invention

[0008] This invention aims to overcome the shortcomings of existing technologies and provides a method for preparing solar thermal absorption and storage ceramics based on iron-rich metallurgical slag that is low in raw material cost, simple in process, and can utilize large quantities of industrial solid waste. The solar thermal absorption and storage ceramics based on iron-rich metallurgical slag prepared by this method exhibit high photothermal conversion efficiency, high heat storage density, high mechanical strength, long service life, high operating temperature, good thermal shock resistance, and excellent high-temperature wear resistance.

[0009] To achieve the above objectives, the technical solution adopted by the present invention comprises the following steps: Step 1: Mix 50-70 wt% of iron-rich metallurgical slag, 15-35 wt% of fused magnesia and 3-16 wt% of industrial alumina, or mix 60-80 wt% of the iron-rich metallurgical slag and 20-40 wt% of the fused magnesia to obtain a mixture, then ball mill it to obtain a slurry.

[0010] Step 2: Dry, grind and sieve the slurry to obtain dry powder; then press the dry powder into shape to obtain a green body.

[0011] Step 3: In an air atmosphere, heat the green body to 1250~1500℃, hold for 1~4 hours, and cool with the furnace to obtain solar energy absorption and storage ceramics based on iron-rich metallurgical slag.

[0012] The main components of the iron-rich metallurgical slag are: CaO 1~10wt%, SiO2 20~35wt%, Fe2O3 25~60wt%, Al2O3 1~10wt%, and MgO 1~10wt%; the particle size of the iron-rich metallurgical slag is ≤0.1mm.

[0013] The fused magnesia has an MgO content > 90 wt% and a particle size < 0.1 mm.

[0014] The industrial alumina has an Al2O3 content > 90 wt% and a particle size < 0.1 mm.

[0015] The ball mill rotates at 100-400 rpm for 3-16 hours; the mass ratio of the mixture to the deionized water to the ball milling media is 1:1-2:1-2.

[0016] The drying temperature is 80~110℃, and the drying time is 10~15h.

[0017] The particle size of the dry powder is less than 0.01 mm.

[0018] The pressure during the pressing process is 20~100MPa.

[0019] The heating rate is 3~5℃ / min.

[0020] By adopting the above technical solution, the present invention has the following beneficial effects compared with the new technology: 1. High-value utilization of solid waste: This invention uses iron-rich metallurgical slag from industrial solid waste as the main raw material (content exceeding 50%), realizing the resource utilization and high-value utilization of solid waste, which aligns with the concept of green and sustainable development. The entire preparation process is simple, requiring no complex equipment or special atmosphere, and is low in cost, making it easy to achieve industrial-scale production.

[0021] 2. This invention utilizes phase design to generate a multiphase ceramic with spinel and olivine as the main crystalline phases. The spinel phase provides excellent selective absorption of sunlight and high thermal conductivity, while the olivine phase contributes high heat storage density and structural stability, resulting in a high operating temperature. The final solar absorber-storage ceramic based on iron-rich metallurgical slag achieves an average solar absorption rate of over 90% and an emissivity of approximately 75% at 800°C, exhibiting both high light absorption and relatively low heat radiation loss. Simultaneously, this solar absorber-storage ceramic based on iron-rich metallurgical slag possesses both high specific heat capacity and high thermal conductivity, significantly improving heat storage density and facilitating efficient energy storage and transfer. In terms of service performance, the resulting solar absorber-storage ceramic based on iron-rich metallurgical slag exhibits excellent thermal shock resistance and wear resistance, capable of withstanding frequent hot and cold cycles and severe interparticle erosion in concentrated solar thermal power generation systems, resulting in a long service life.

[0022] 3. This invention, by introducing fused magnesia, effectively promotes the transformation of the glassy phase to a stable crystalline phase in iron-rich metallurgical slag, forming easily doped spinel. This significantly improves the high-temperature performance of the solar energy absorption-storage ceramic based on iron-rich metallurgical slag. Simultaneously, by controlling the amount of alumina added, Al³⁺ is achieved. +Doping modification of the spinel structure not only optimizes sintering behavior but also effectively regulates grain boundary phases and microstructure, further enhancing the photothermal performance and mechanical strength of solar energy absorption-storage ceramics based on iron-rich metallurgical slag. This is because the present invention, through the synergistic regulation of MgO / Al2O3, transforms the initially disordered Fe–Al–Si–O glass network of the iron-rich metallurgical slag system into a structure composed of Mg(Fe)O2O3. x Al 2-x The stable multiphase structure composed of O4 spinel and Mg2SiO4 olivine significantly improves the light absorption capacity and high-temperature structural stability of solar energy absorption-storage ceramics based on iron-rich metallurgical slag. The addition of MgO promotes structural rearrangement of the system at high temperatures, transforming the original structure into a multiphase structure with crystalline spinel and olivine, providing a foundation for constructing a stable high-temperature resistant structure.

[0023] 4. This invention allows for the addition of Al2O3 when the Al2O3 content in the iron-rich metallurgical slag is low (1~3wt%), or when the Al2O3 content in the iron-rich metallurgical slag is high (3~10wt%), without the need to add additional alumina. Solid solution can occur during sintering, resulting in smaller radius Al³⁺ particles. + Preferential entry into the B-sites (octahedral sites) of spinel causes shrinkage of the corresponding MO octahedra, reducing local lattice symmetry, redistributing the coordination environment, and continuously decreasing spinel cell parameters with increasing doping concentration. This solid solution behavior leads to a systematic adjustment of bond lengths, bond angles, and local crystal field strength within the octahedra, resulting in simultaneous coordination rearrangement and lattice shrinkage in the spinel structure at both long-range and short-range scales, thus enhancing structural stability. Simultaneously, Al³⁺… + Solid solution can also introduce charge imbalance, causing oxygen vacancies to form in the system at high temperatures and promoting the oxidation state transformation of some Fe³ to form Fe²⁺. + Oxygen vacancies and Fe²⁺ + The coexistence of these elements generates intermediate energy levels in the crystal band structure, altering the electronic structure of the Fe-O coordination units and enhancing the hybridization of Fe3d and O2p orbitals. This increases the probability of dd transitions, resulting in higher solar absorption capacity in the visible to near-infrared band for solar-powered heat-absorbing and storing ceramics based on iron-rich metallurgical slag, and further reducing the effective bandgap of these ceramics. This invention, through the synergistic effects of crystal structure reconstruction, cation occupancy regulation, and defect engineering, successfully constructs a composite spinel ceramic material system with high solar absorption rate, high thermal stability, and excellent physical service performance.

[0024] The solar thermal absorption and storage ceramic based on iron-rich metallurgical slag prepared by this invention has a main crystalline phase of spinel and olivine, which is a multiphase ceramic. The material has excellent thermophysical properties and can work for a long time in high temperature and complex environment, and has great application potential in the field of concentrated solar power generation.

[0025] Therefore, this invention features low raw material costs, simple processes, and the ability to utilize large quantities of industrial solid waste. The prepared solar thermal absorption-storage ceramic based on iron-rich metallurgical slag exhibits high photothermal conversion efficiency, high thermal storage density, high mechanical strength, long service life, high operating temperature, good thermal shock resistance, and excellent high-temperature wear resistance. Attached Figure Description

[0026] Figure 1 X-ray diffraction patterns of four solar energy absorbing and storing ceramics based on iron-rich metallurgical slag prepared in this invention; Figure 2 for Figure 1 A schematic diagram of the backscattering structure of the first solar energy absorption-storage ceramic based on iron-rich metallurgical slag in China. Figure 3 for Figure 1 A schematic diagram of the backscattering structure of the second type of solar energy absorption-storage ceramic based on iron-rich metallurgical slag. Figure 4 for Figure 1 A schematic diagram of the backscattering structure of the third type of solar energy absorption-storage ceramic based on iron-rich metallurgical slag. Figure 5 for Figure 1 A schematic diagram of the backscattering structure of the fourth type of solar energy absorption-storage ceramic based on iron-rich metallurgical slag. Figure 6 for Figure 1 Solar absorptivity spectra of the four types of solar thermal absorption and storage ceramics based on iron-rich metallurgical slag. Figure 7 for Figure 1 High-temperature emissivity spectra of the four types of solar thermal absorption and storage ceramics based on iron-rich metallurgical slag. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of protection thereof.

[0028] A solar thermal absorption and storage ceramic based on iron-rich metallurgical slag and its preparation method. The preparation method described in this specific embodiment is as follows: Step 1: Mix 50-70 wt% of iron-rich metallurgical slag, 15-35 wt% of fused magnesia and 3-16 wt% of industrial alumina, or mix 60-80 wt% of the iron-rich metallurgical slag and 20-40 wt% of the fused magnesia to obtain a mixture, then ball mill it to obtain a slurry.

[0029] Step 2: Dry, grind and sieve the slurry to obtain dry powder; then press the dry powder into shape to obtain a green body.

[0030] Step 3: In an air atmosphere, heat the green body to 1250~1500℃, hold for 1~4 hours, and cool with the furnace to obtain solar energy absorption and storage ceramics based on iron-rich metallurgical slag.

[0031] The main components of the iron-rich metallurgical slag are: CaO 1~10wt%, SiO2 20~35wt%, Fe2O3 25~60wt%, Al2O3 1~10wt%, and MgO 1~10wt%; the particle size of the iron-rich metallurgical slag is ≤0.1mm.

[0032] The fused magnesia contains >90wt% MgO.

[0033] The Al2O3 content of the industrial alumina is >90wt%.

[0034] The ball mill rotates at 100-400 rpm for 3-16 hours; the mass ratio of the mixture to the deionized water to the ball milling media is 1:1-2:1-2.

[0035] The drying temperature is 80~110℃, and the drying time is 10~15h.

[0036] The pressure during the pressing process is 20~100MPa.

[0037] The heating rate is 3~5℃ / min.

[0038] In this specific implementation: The particle size of the iron-rich metallurgical slag is ≤0.1mm; The particle size of the fused magnesia is <0.1 mm; The particle size of the industrial alumina is <0.1 mm; The particle size of the dry powder is less than 0.01 mm.

[0039] The details will not be repeated in the examples.

[0040] Example 1 A solar thermal absorption and storage ceramic based on iron-rich metallurgical slag and its preparation method. The preparation method described in this embodiment is as follows: Step 1: Mix 50wt% of iron-rich metallurgical slag, 34wt% of fused magnesia and 16wt% of industrial alumina to obtain a mixture, then ball mill it to obtain a slurry.

[0041] Step 2: Dry, grind and sieve the slurry to obtain dry powder; then press the dry powder into shape to obtain a green body.

[0042] Step 3: In an air atmosphere, heat the green body to 1250°C, hold for 1 hour, and cool with the furnace to obtain a solar energy absorption and storage ceramic based on iron-rich metallurgical slag.

[0043] The main components of the iron-rich metallurgical slag are: CaO 4.12wt%, SiO2 20.15wt%, Fe2O3 59.85wt%, Al2O3 1.55wt%, and MgO 4.25wt%.

[0044] The fused magnesia has an MgO content of 90.32 wt%.

[0045] The industrial alumina has an Al2O3 content of 95.31 wt%.

[0046] The ball mill rotates at 100 rpm for 3 hours; the mass ratio of the mixture to deionized water to the ball milling media is 1:1:1.

[0047] The drying temperature is 80℃, and the drying time is 10 hours.

[0048] The pressure during the pressing process is 20 MPa.

[0049] The heating rate is 3°C / min.

[0050] Example 2 A solar thermal absorption and storage ceramic based on iron-rich metallurgical slag and its preparation method. The preparation method described in this embodiment is as follows: Step 1: Mix 62wt% of iron-rich metallurgical slag, 35wt% of fused magnesia and 3wt% of industrial alumina to obtain a mixture, then ball mill it to obtain a slurry.

[0051] Step 2: Dry, grind and sieve the slurry to obtain dry powder; then press the dry powder into shape to obtain a green body.

[0052] Step 3: In an air atmosphere, heat the green body to 1350°C, hold for 2 hours, and cool with the furnace to obtain a solar energy absorption and storage ceramic based on iron-rich metallurgical slag.

[0053] The main components of the iron-rich metallurgical slag are: CaO 1.38wt%, SiO2 24.45wt%, Fe2O3 55.12wt%, Al2O3 1.28wt%, and MgO 7.72wt%.

[0054] The fused magnesia has an MgO content of 94.51 wt%.

[0055] The industrial alumina has an Al2O3 content of 90.88 wt%.

[0056] The ball milling speed is 100~400 rpm, and the milling time is 3~16 h; the mass ratio of the mixture to deionized water to the milling media is 1:1:1.5. The drying temperature is 90℃, and the drying time is 12 h.

[0057] The pressure during the pressing process is 40 MPa.

[0058] The heating rate is 4°C / min.

[0059] Example 3 A solar thermal absorption and storage ceramic based on iron-rich metallurgical slag and its preparation method. The preparation method described in this embodiment is as follows: Step 1: Mix 65wt% of iron-rich metallurgical slag, 25wt% of fused magnesia and 10wt% of industrial alumina to obtain a mixture, then ball mill it to obtain a slurry.

[0060] Step 2: Dry, grind and sieve the slurry to obtain dry powder; then press the dry powder into shape to obtain a green body.

[0061] Step 3: In an air atmosphere, heat the green body to 1450°C, hold for 3 hours, and cool with the furnace to obtain a solar energy absorption and storage ceramic based on iron-rich metallurgical slag.

[0062] The main components of the iron-rich metallurgical slag are: CaO 7.15wt%, SiO2 24.88wt%, Fe2O3 49.65wt%, Al2O3 2.45wt%, and MgO 6.75wt%.

[0063] The fused magnesia has an MgO content of 93.48 wt%.

[0064] The industrial alumina has an Al2O3 content of 96.21 wt%.

[0065] The ball mill rotates at 300 rpm for 13 hours; the mass ratio of the mixture to deionized water to the milling media is 1:1:2.

[0066] The drying temperature is 100℃ and the drying time is 14 hours.

[0067] The pressure during the pressing process is 80 MPa.

[0068] The heating rate is 5°C / min.

[0069] Example 4 A solar thermal absorption and storage ceramic based on iron-rich metallurgical slag and its preparation method. The preparation method described in this embodiment is as follows: Step 1: Mix 70wt% of iron-rich metallurgical slag, 15wt% of fused magnesia and 15wt% of industrial alumina to obtain a mixture, then ball mill it to obtain a slurry.

[0070] Step 2: Dry, grind and sieve the slurry to obtain dry powder; then press the dry powder into shape to obtain a green body.

[0071] Step 3: In an air atmosphere, heat the green body to 1500°C, hold for 4 hours, and cool with the furnace to obtain a solar energy absorption and storage ceramic based on iron-rich metallurgical slag.

[0072] The main components of the iron-rich metallurgical slag are: CaO 8.95wt%, SiO2 26.12wt%, Fe2O3 43.25wt%, Al2O3 2.95wt%, and MgO 8.65wt%.

[0073] The fused magnesia has an MgO content of 96.32 wt%.

[0074] The industrial alumina has an Al2O3 content of 98.12 wt%.

[0075] The ball mill operates at a speed of 400 rpm for 16 hours; the mass ratio of the mixture to deionized water to the milling media is 1:1.5:1.

[0076] The drying temperature is 110℃, and the drying time is 15 hours.

[0077] The pressure during the pressing process is 100 MPa.

[0078] The heating rate is 5°C / min.

[0079] Example 5 A solar thermal absorption and storage ceramic based on iron-rich metallurgical slag and its preparation method. The preparation method described in this embodiment is as follows: Step 1: Mix 80wt% of iron-rich metallurgical slag and 20wt% of fused magnesia to obtain a mixture, then ball mill it to obtain a slurry.

[0080] Step 2: Dry, grind and sieve the slurry to obtain dry powder; then press the dry powder into shape to obtain a green body.

[0081] Step 3: In an air atmosphere, heat the green body to 1250°C, hold for 1 hour, and cool with the furnace to obtain a solar energy absorption and storage ceramic based on iron-rich metallurgical slag.

[0082] The main components of the iron-rich metallurgical slag are: CaO 9.15wt%, SiO2 31.45wt%, Fe2O3 41.55wt%, Al2O3 7.85wt%, and MgO 1.15wt%.

[0083] The fused magnesia has an MgO content of 90.51 wt%.

[0084] The industrial alumina has an Al2O3 content of 98.34 wt%.

[0085] The ball mill operates at a speed of 100 rpm for 3 hours; the mass ratio of the mixture to deionized water to the milling media is 1:1.5:2.

[0086] The drying temperature is 80℃, and the drying time is 10 hours.

[0087] The pressure during the pressing process is 20 MPa.

[0088] The heating rate is 3°C / min.

[0089] Example 6 A solar thermal absorption and storage ceramic based on iron-rich metallurgical slag and its preparation method. The preparation method described in this embodiment is as follows: Step 1: Mix 70wt% of iron-rich metallurgical slag and 30wt% of fused magnesia to obtain a mixture, then ball mill it to obtain a slurry.

[0090] Step 2: Dry, grind and sieve the slurry to obtain dry powder; then press the dry powder into shape to obtain a green body.

[0091] Step 3: In an air atmosphere, heat the green body to 1400°C, hold for 3 hours, and cool with the furnace to obtain a solar energy absorption and storage ceramic based on iron-rich metallurgical slag.

[0092] The main components of the iron-rich metallurgical slag are: CaO 9.55wt%, SiO2 32.15wt%, Fe2O3 32.85wt%, Al2O3 8.45wt%, and MgO 8.12wt%.

[0093] The fused magnesia has an MgO content of 95.58 wt%.

[0094] The industrial alumina has an Al2O3 content of 90.21 wt%.

[0095] The ball mill rotates at 200 rpm for 9 hours; the mass ratio of the mixture to deionized water to the milling media is 1:2:1.

[0096] The drying temperature is 90℃, and the drying time is 13 hours.

[0097] The pressure during the pressing process is 50 MPa.

[0098] The heating rate is 4°C / min.

[0099] Example 7 A solar thermal absorption and storage ceramic based on iron-rich metallurgical slag and its preparation method. The preparation method described in this embodiment is as follows: Step 1: Mix 60wt% of iron-rich metallurgical slag and 40wt% of fused magnesia to obtain a mixture, then ball mill it to obtain a slurry.

[0100] Step 2: Dry, grind and sieve the slurry to obtain dry powder; then press the dry powder into shape to obtain a green body.

[0101] Step 3: In an air atmosphere, heat the green body to 1500°C, hold for 4 hours, and cool with the furnace to obtain a solar energy absorption and storage ceramic based on iron-rich metallurgical slag.

[0102] The main components of the iron-rich metallurgical slag are: CaO 9.92wt%, SiO2 34.88wt%, Fe2O3 25.42wt%, Al2O3 9.88wt%, and MgO 9.85wt%.

[0103] The fused magnesia has an MgO content of 92.67 wt%.

[0104] The industrial alumina has an Al2O3 content of 95.98 wt%.

[0105] The ball mill rotates at 400 rpm for 16 hours; the mass ratio of the mixture to deionized water to the milling media is 1:2:2.

[0106] The drying temperature is 110℃, and the drying time is 15 hours.

[0107] The pressure during the pressing process is 100 MPa.

[0108] The heating rate is 5°C / min.

[0109] This specific implementation method has the following advantages compared with the prior art: 1. High-value utilization of solid waste: This specific implementation method uses iron-rich metallurgical slag from industrial solid waste as the main raw material (content is as high as 50% or more), realizing the resource utilization and high-value utilization of solid waste, which is in line with the concept of green and sustainable development. The entire preparation process is simple, requires no complex equipment or special atmosphere, is low in cost, and is easy to realize industrial production.

[0110] 2. This specific embodiment utilizes phase design to generate a multiphase ceramic with spinel and olivine as the main crystalline phases. The spinel phase provides excellent selective absorption of sunlight and high thermal conductivity, while the olivine phase contributes high heat storage density and structural stability, resulting in a high operating temperature. The final solar absorber-storage ceramic based on iron-rich metallurgical slag achieves an average solar absorption rate of over 90% and an emissivity of approximately 75% at 800°C, exhibiting both high light absorption and relatively low heat radiation loss. Simultaneously, this solar absorber-storage ceramic based on iron-rich metallurgical slag possesses both high specific heat capacity and high thermal conductivity, significantly improving heat storage density and facilitating efficient energy storage and transfer. In terms of service performance, the prepared solar absorber-storage ceramic based on iron-rich metallurgical slag exhibits excellent thermal shock resistance and wear resistance, capable of withstanding frequent hot and cold cycles and severe interparticle erosion in concentrated solar thermal power generation systems, resulting in a long service life.

[0111] 3. This specific embodiment effectively promotes the transformation of the glassy phase to a stable crystalline phase in iron-rich metallurgical slag by introducing fused magnesia, forming easily doped spinel. This significantly improves the high-temperature performance of the prepared solar energy absorption-storage ceramic based on iron-rich metallurgical slag. Simultaneously, by controlling the amount of alumina added, Al³⁺ is achieved. + Doping modification of spinel structure can not only optimize sintering behavior, but also effectively regulate grain boundary phase and microstructure, further improving the photothermal performance and mechanical strength of solar thermal absorption and storage ceramics based on iron-rich metallurgical slag.

[0112] The solar thermal absorption and storage ceramic based on iron-rich metallurgical slag prepared by this specific method is shown in the attached figure: Figure 1 X-ray diffraction patterns of solar energy absorbing and storing ceramics based on iron-rich metallurgical slag prepared in Examples 1, 2, 6 and 7; Figure 2 for Figure 1 A schematic diagram of the backscattering structure of the solar energy absorption-storage ceramic based on iron-rich metallurgical slag prepared in Example 1. Figure 3 for Figure 1 A schematic diagram of the backscattering structure of the solar energy absorption-storage ceramic based on iron-rich metallurgical slag prepared in Example 2. Figure 4 for Figure 1 A schematic diagram of the backscattering structure of the solar energy absorption-storage ceramic based on iron-rich metallurgical slag prepared in Example 6. Figure 5 for Figure 1 A schematic diagram of the backscattering structure of the solar energy absorption-storage ceramic based on iron-rich metallurgical slag prepared in Example 7. Figure 6 for Figure 1 The solar absorptivity spectra of four types of solar thermal absorption-storage ceramics based on iron-rich metallurgical slag are shown. Figure 7 for Figure 1 The high-temperature emissivity spectra of four types of solar thermal absorption and storage ceramics based on iron-rich metallurgical slag are shown.

[0113] from Figure 1 It can be seen that the main crystalline phases of the solar energy absorption-storage ceramics based on iron-rich metallurgical slag prepared in Examples 1, 2, 6, and 7 are all spinel and olivine high-temperature resistant phases; from Figures 2-5 It can be seen that the main crystalline phases of the solar thermal absorption-storage ceramics based on iron-rich metallurgical slag prepared in Examples 1, 2, 6, and 7 are all spinel and olivine high-temperature resistant phases, as well as a small amount of glass phase; from Figures 6-7 It can be seen that the solar thermal absorption and storage ceramics based on iron-rich metallurgical slag prepared in Examples 1, 2, 6 and 7 have good selective absorption effect of sunlight.

[0114] This specific implementation method, through the synergistic regulation of MgO / Al2O3, transforms the initially disordered Fe–Al–Si–O glass network of the iron-rich metallurgical slag system into a network composed of Mg(Fe) x Al 2-x The stable multiphase structure composed of O4 spinel and Mg2SiO4 olivine significantly improves the light absorption capacity and high-temperature structural stability of solar energy absorption-storage ceramics based on iron-rich metallurgical slag. The addition of MgO promotes structural rearrangement of the system at high temperatures, transforming the original structure into a multiphase structure with crystalline spinel and olivine, providing a foundation for constructing a stable high-temperature resistant structure.

[0115] 4. This specific method allows for the addition of Al2O3 when the Al2O3 content in the iron-rich metallurgical slag is low (1~3wt%), or when the alumina content in the iron-rich metallurgical slag is high (3~10wt%), eliminating the need for additional alumina addition. Solid solution can occur during sintering, resulting in smaller radius Al³⁺ particles. + Preferential entry into the B-sites (octahedral sites) of spinel causes shrinkage of the corresponding MO octahedra, reducing local lattice symmetry, redistributing the coordination environment, and continuously decreasing spinel cell parameters with increasing doping concentration. This solid solution behavior leads to a systematic adjustment of bond lengths, bond angles, and local crystal field strength within the octahedra, resulting in simultaneous coordination rearrangement and lattice shrinkage in the spinel structure at both long-range and short-range scales, thus enhancing structural stability. Simultaneously, Al³⁺… + Solid solution can also introduce charge imbalance, causing oxygen vacancies to form in the system at high temperatures and promoting the oxidation state transformation of some Fe³ to form Fe²⁺. + Oxygen vacancies and Fe²⁺ +The coexistence of these elements generates intermediate energy levels in the crystal band structure, altering the electronic structure of the Fe-O coordination units and enhancing the hybridization of Fe3d and O2p orbitals. This increases the probability of dd transitions, resulting in higher solar absorption capacity in the visible to near-infrared band for solar-powered heat-absorbing and storing ceramics based on iron-rich metallurgical slag, and further reducing the effective bandgap of these ceramics. This specific embodiment successfully constructs a composite spinel ceramic material system with high solar absorption rate, high thermal stability, and excellent physical service performance through the synergistic effects of crystal structure reconstruction, cation occupancy control, and defect engineering.

[0116] The solar thermal absorption and storage ceramic based on iron-rich metallurgical slag prepared in this specific embodiment has a main crystalline phase of spinel and olivine, which is a multiphase ceramic. The material has excellent thermophysical properties and can work for a long time in high-temperature and complex environments, and has great application potential in the field of concentrated solar power generation.

[0117] Therefore, this specific embodiment features low raw material costs, simple process, and the ability to utilize large quantities of industrial solid waste. The prepared solar thermal absorption-storage ceramic based on iron-rich metallurgical slag exhibits high photothermal conversion efficiency, high heat storage density, high mechanical strength, long service life, high operating temperature, good thermal shock resistance, and excellent high-temperature wear resistance.

Claims

1. A method for preparing solar energy absorption-storage ceramics based on iron-rich metallurgical slag, characterized in that, The preparation method comprises the following steps: Step 1: Mix 50-70 wt% of iron-rich metallurgical slag, 15-35 wt% of fused magnesia and 3-16 wt% of industrial alumina, or mix 60-80 wt% of the iron-rich metallurgical slag and 20-40 wt% of the fused magnesia to obtain a mixture, then ball mill it to obtain a slurry. Step 2: Dry, grind and sieve the slurry to obtain dry powder; then press the dry powder into shape to obtain a green body; Step 3: In an air atmosphere, heat the green body to 1250~1500℃, hold for 1~4 hours, and cool with the furnace to obtain solar energy absorption and storage ceramics based on iron-rich metallurgical slag.

2. The preparation method of solar thermal absorption and storage ceramics based on iron-rich metallurgical slag according to claim 1, characterized in that, The main components of the iron-rich metallurgical slag are: CaO 1~10wt%, SiO2 20~35wt%, Fe2O3 25~60wt%, Al2O3 1~10wt%, and MgO 1~10wt%; the particle size of the iron-rich metallurgical slag is ≤0.1mm.

3. The method for preparing solar thermal absorption and storage ceramics based on iron-rich metallurgical slag according to claim 1, characterized in that, The fused magnesia has an MgO content > 90 wt% and a particle size < 0.1 mm.

4. The preparation method of solar thermal absorption and storage ceramics based on iron-rich metallurgical slag according to claim 1, characterized in that, The industrial alumina has an Al2O3 content > 90 wt% and a particle size < 0.1 mm.

5. The method for preparing solar thermal absorption and storage ceramics based on iron-rich metallurgical slag according to claim 1, characterized in that, The ball mill rotates at 100-400 rpm for 3-16 hours; the mass ratio of the mixture to the deionized water to the ball milling media is 1:1-2:1-2.

6. The method for preparing solar thermal absorption and storage ceramics based on iron-rich metallurgical slag according to claim 1, characterized in that, The drying temperature is 80~110℃, and the drying time is 10~15h.

7. The method for preparing solar thermal absorption and storage ceramics based on iron-rich metallurgical slag according to claim 1, characterized in that, The particle size of the dry powder is less than 0.01 mm.

8. The method for preparing solar thermal absorption and storage ceramics based on iron-rich metallurgical slag according to claim 1, characterized in that, The pressure during the pressing process is 20~100MPa.

9. The method for preparing solar thermal absorption and storage ceramics based on iron-rich metallurgical slag according to claim 1, characterized in that, The heating rate is 3~5℃ / min.

10. A solar energy absorption-storage ceramic based on iron-rich metallurgical slag, characterized in that, The solar thermal absorption and storage ceramic based on iron-rich metallurgical slag is the solar thermal absorption and storage ceramic based on iron-rich metallurgical slag prepared according to any one of claims 1 to 9.

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