A modified steel slag-based solar selective absorption and heat storage ceramic particle and its preparation method

Abstract

This invention discloses a modified steel slag-based solar selective absorption and thermal storage ceramic particle and its preparation method. The raw materials, by mass percentage, consist of the following components: 40-80 wt% steel slag, 15-25 wt% alumina, 5-18 wt% ferric oxide, 0-7 wt% manganese dioxide, and 0-10 wt% titanium dioxide. The above raw material powder is mixed evenly, shaped, and calcined at high temperature to obtain the solar tower thermal power generation thermal storage ceramic particle. The solid ceramic particle prepared by this invention achieves high-efficiency absorption of solar radiation while also exhibiting low infrared emission, stable performance at high temperatures, and lower cost.

Description

Technical Field

[0001] This invention relates to the field of solar thermal power generation, specifically to a modified steel slag-based solar selective absorption and heat storage ceramic particle and its preparation method. Background Technology

[0002] Solar thermal power generation uses concentrated solar energy as a heat source, converting solar radiation into heat energy through a heat collection medium to drive a steam turbine for power generation. This technology effectively addresses the imbalances in solar energy across time, space, and intensity, improving the peak-shaving capacity of the power system, reducing power production costs, and enabling continuous power generation. Among heat collection and storage media, solid ceramic particles are gaining increasing attention due to their low cost, simple technology, and high operating temperature. Currently, alumina-based and silicon carbide-based ceramic heat collection and storage materials are widely used, but they suffer from high radiative heat loss, poor high-temperature stability, and high cost, limiting their further application in the field of solar thermal power generation.

[0003] The optical properties of solid ceramic particles directly affect the thermoelectric conversion efficiency of thermal power generation systems. Increasing the absorptivity of solid particles to absorb more solar energy, while reducing thermal emissivity to minimize radiative heat loss, can directly improve the overall efficiency of thermal power generation systems. Current research on improving the optical performance of solid particles mainly focuses on enhancing their solar radiation absorption capacity through methods such as doping with metal powders like Al, Fe, Cr, Cu, and Ti, and surface coatings. However, this often results in increased emissivity in the infrared band. Furthermore, the high-temperature thermal stability of solar collector particles is another key factor affecting the long-term, efficient, and stable operation of particle collectors. Researchers have attempted to improve absorptivity by coating natural minerals with substances such as carbon black, iron-manganese pigments, and black spinel; however, these methods have all resulted in varying degrees of coating peeling and performance degradation after heat treatment. The CARBO series of commercially available ceramic proppants exhibits a high absorptivity of 0.93, but after being kept at 1000℃ for 192 hours, the absorptivity drops to only 0.84, showing significant degradation. Besides the physical properties of solid particles, cost is another crucial factor that must be considered for commercialization. Sand has attracted some attention due to its wide availability and low cost, but its thermophysical and optical properties are poor. Other common candidate particles such as bauxite, alumina and silicon carbide have good optical and thermophysical properties, but their higher cost hinders their further application. Summary of the Invention

[0004] The purpose of this invention is to provide a modified steel slag-based solar thermal power generation heat collection and storage ceramic particle and its preparation method. The prepared ceramic particle not only has a high working temperature, high mechanical strength, simple process, low cost, and green environmental protection, but also has excellent optical properties, selective absorption performance of solar radiation and high temperature thermal stability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A modified steel slag-based solar selective absorption and heat storage ceramic particle, whose raw materials are composed of the following components by mass percentage: 40-80 wt% steel slag, 15-25 wt% aluminum oxide, 5-18 wt% ferric oxide, 0-7 wt% manganese dioxide, and 0-10 wt% titanium dioxide.

[0007] Preferably, the steel slag composition by mass percentage is: CaCO3 10-20wt%, SiO2 10-22wt%, Fe2O3 2-5wt%, FeO 10-22wt%, CaO 40-60wt%, Al2O3 4-16wt%, MnO 0-4wt%, MgO 5-15wt%.

[0008] Preferably, the particle size of the raw materials is ≤0.075mm.

[0009] Preferably, the aluminum oxide can be obtained by oxidation of elemental aluminum or high-temperature decomposition of aluminum hydroxide or aluminum nitrate; the ferric oxide can be obtained by oxidation-reduction of iron oxides or high-temperature decomposition of ferric hydroxide or ferric nitrate.

[0010] A method for preparing modified steel slag-based solar selective absorption and heat storage ceramic particles includes the following steps:

[0011] Step S1: Weigh the raw material powder and mix it evenly;

[0012] Step S2: Spray water or use a binder onto the raw material powder mixed in step S1 to obtain a blank with a moisture content of 20%-45%.

[0013] Step S3: The blank obtained in step S2 is shaped using a molding device;

[0014] Step S4: Sinter the blank formed in step S3 to obtain selectively absorbing and heat-storing ceramic particles.

[0015] Preferably, in step S2, the binder is polyvinyl alcohol or carboxymethyl cellulose, and is in solid or solution form, with the solid content of the binder being 3-6 wt% of the raw material powder content.

[0016] Preferably, in step S3, the blank is formed into a granular shape, or a block, cylinder, cuboid, arc, or other complex shape by molding equipment.

[0017] In step S3, when the blank is formed into a block, cylinder, cuboid, or arc shape by the molding equipment, the pressing pressure is 0.3-40 MPa.

[0018] Preferably, in step S3, when the raw material is formed into granules by the molding equipment, the molding equipment used is an extrusion rounding machine, a pot granulator, or a rotary kiln granulator, and the granule shape is round, elliptical, or cylindrical, with a particle size range of 0.2-2mm.

[0019] Preferably, in step S4, sintering is carried out in an air atmosphere, and the sintering procedure is as follows: heating rate 3-8℃ / min; holding the highest temperature point for 2-10 hours; the highest temperature point is 1200-1360℃; and finally, cooling with the furnace.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. The selective absorption and heat storage ceramic of the present invention has a steel slag content of up to 66.0%, which not only helps to dispose of steelmaking waste and is environmentally friendly, but also reduces production costs. Its raw material cost is lower than that of foreign CARBO commercial proppant particles, which helps to realize large-scale application in the field of solar thermal power generation.

[0022] 2. The selective absorption heat storage ceramic particles of the present invention have selective absorption performance, with an average absorptivity of 93.0% and an emissivity of only 68.0%, which realizes a significant reduction in radiative heat loss while achieving efficient heat collection, overcoming the problem of high emissivity and high absorptivity coexisting in solar heat storage ceramics.

[0023] 3. The selective absorption and heat storage ceramic particles of the present invention have the advantage of stable high-temperature performance. The prepared particles are kept in a muffle furnace at 1000℃ for 120 hours, and their excellent performance of high absorption and low emission remains almost unchanged. Attached Figure Description

[0024] Figure 1 These are photographs of the appearance of samples from Embodiments 1, 2, and 3 of the present invention;

[0025] Figure 2 This is a flowchart of the preparation of selectively absorbing and heat-storing ceramic particles by extrusion spheroidization in Embodiment 1 of the present invention;

[0026] Figure 3 The absorptivity and emissivity curves of the selective absorption and thermal storage ceramic particles prepared in Example 1 of this invention;

[0027] Figure 4 The bar chart shows the changes in the absorptivity and emissivity of the ceramic particles prepared in Example 1 of this invention with heat treatment time. Implementation

[0028] To make the present invention clearer and easier to understand, the present invention is further illustrated below with reference to specific embodiments and accompanying drawings. It should be understood that the embodiments described below are for explanation and illustration only and are not intended to limit the present invention. Example

[0029] The raw material composition of the selective absorption and heat storage ceramic particles in this embodiment is shown in Table 1 below:

[0030] Table 1

[0031] name steel slag <![CDATA[α-Al2O3]]> <![CDATA[Fe2O3]]> <![CDATA[MnO2]]> Percentage (wt%) 66.7 23.3 6.7 3.3

[0032] The chemical composition of the steel slag is shown in Table 2 below:

[0033] Table 2

[0034] name <![CDATA[CaCO3]]> <![CDATA[SiO2]]> FeO <![CDATA[(CaO) 12 (Al2O3)7]]> <![CDATA[Ca2SiO4]]> <![CDATA[Ca2Al2SiO7]]> Percentage (wt%) 15.3 7.2 27.0 5.9 34.3 10.3

[0035] The preparation method includes the following steps:

[0036] 1. Raw material proportioning and mixing: pass steel slag powder through a 200-mesh sieve and other raw material powders through a 600-mesh sieve. Weigh them according to the mass ratio and ball mill for 1 hour to obtain uniform powder.

[0037] 2. Granulation: Add water to the mixed raw material powder, the amount of water being 35% of the total weight of the powder. Mix thoroughly to ensure uniform moisture content, then feed into the extrusion rounding machine to form granules and obtain raw granules. The extrusion rounding machine uses a 1.0mm perforated plate.

[0038] 3. High-temperature sintering: After drying, the raw pellets are placed into a high-temperature muffle furnace and calcined in an air atmosphere. The temperature is raised to 1310℃ at a rate of 4.5℃ / min and held for 10 hours, and then cooled with the furnace.

[0039] Tests showed that the prepared ceramic particles had an absorptivity of 93.0%, an emissivity of 68.0%, and a single-particle crushing strength of 28.9 N. After being held in a muffle furnace at 1000℃ in air for 120 hours, the absorptivity became 93.2%, with the high absorptivity remaining almost unchanged. The emissivity was 68.1%, and the single-particle crushing strength was 26.2 N. These properties can meet the requirements of the thermal power generation system for continuous and efficient utilization of solar energy and reduce maintenance costs.

[0040] like Figure 3 As shown, the selective absorption and heat storage ceramic particles prepared in Example 1 have extremely high absorptivity in the 0.28-1μm band where solar irradiance is strongest, and low emissivity in the 8.0-12.0μm band where spectral radiation energy is high at room temperature, thereby achieving a significant reduction in radiative heat loss while maintaining high absorptivity.

[0041] like Figure 4As shown, the selective absorption and thermal storage ceramic particles prepared in Example 1, after being kept at a high temperature of 1000℃ for 120 hours, showed almost no change in their optical properties. Their excellent high-temperature stability can not only effectively resist local failures caused by uneven energy flux density of the collector, but also reduce maintenance costs and ensure the continuous and efficient utilization of solar energy by the thermal power generation system. Example

[0042] Unlike Example 1, the composition of the selectively absorbing and heat-storing ceramic particles is shown in Table 3 below, and the maximum calcination temperature is 1220℃.

[0043] Table 3

[0044] name steel slag <![CDATA[α-Al2O3]]> <![CDATA[Fe2O3]]> <![CDATA[MnO2]]> <![CDATA[TiO2]]> Percentage (wt%) 62.5 15.6 6.3 9.4 6.2

[0045] Tests showed that the prepared ceramic particles had an absorptivity of 92.7%, an emissivity of 69.3%, and a single-particle breaking strength of 48.5 N. After being held in a muffle furnace at 1000℃ in air for 82 hours, the absorptivity became 92.9%, the emissivity 69.3%, and the single-particle breaking strength 46.4 N, which meets the performance requirements of ceramic materials for solar thermal power generation systems. Example

[0046] Unlike Example 1, the forming process of the selective absorption and heat storage ceramic disc is as follows: the uniform powder obtained by ball milling is pressed into a circular blank with a diameter of Φ12.7×3mm by a hydraulic press.

[0047] The prepared ceramic discs were tested and found to have an absorptivity of 92%, an emissivity of 68.2%, and a bulk density of 3.1 g / cm³. 3 The room temperature thermal conductivity is 2.2 W / (mK), which meets the performance requirements of ceramic materials for solar thermal power generation systems.

[0048] The above description represents preferred embodiments of the present invention and does not constitute a limitation on the scope of protection of the present invention. Any other corresponding modifications, equivalent substitutions, and improvements made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A modified steel slag-based solar selective absorption and heat storage ceramic particle, characterized in that, According to mass percentage, its raw materials consist of the following components: 40-80 wt% steel slag, 15-25 wt% aluminum oxide, 5-18 wt% ferric oxide, 0-7 wt% manganese dioxide (but not 0), and 0-10 wt% titanium dioxide.

2. The modified steel slag-based solar selective absorption and heat storage ceramic particles according to claim 1, characterized in that, The steel slag, by mass percentage, is composed of: CaCO3 10-20wt%, SiO2 10-22wt%, Fe2O3 2-5wt%, FeO 10-22wt%, CaO 40-60wt%, Al2O3 4-16wt%, MnO 0-4wt%, and MgO 5-15wt%.

3. The modified steel slag-based solar selective absorption and heat storage ceramic particles according to claim 1, characterized in that, The particle size of the raw materials is ≤0.075mm.

4. The method for preparing modified steel slag-based solar selective absorption and heat storage ceramic particles according to any one of claims 1-3, characterized in that, Includes the following steps: Step S1: Weigh the raw material powder and mix it evenly; Step S2: Spray water or use a binder onto the raw material powder mixed in step S1 to obtain a blank with a moisture content of 20%-45%. Step S3: The blank obtained in step S2 is shaped using a molding device; Step S4: Sinter the blank formed in step S3 to obtain selectively absorbing and heat-storing ceramic particles.

5. The method for preparing modified steel slag-based solar selective absorption and heat storage ceramic particles according to claim 4, characterized in that, In step S2, the binder is polyvinyl alcohol or carboxymethyl cellulose, in solid or solution form, and the solid content of the binder is 3-6 wt% of the raw material powder content.

6. The method for preparing modified steel slag-based solar selective absorption and heat storage ceramic particles according to claim 4, characterized in that, In step S3, the blank is formed into granular shape or block by molding equipment.

7. The method for preparing modified steel slag-based solar selective absorption and heat storage ceramic particles according to claim 6, characterized in that, In step S3, when the blank is formed into a block by the molding equipment, the pressing pressure is 0.3-40MPa.

8. The method for preparing modified steel slag-based solar selective absorption and heat storage ceramic particles according to claim 6, characterized in that, In step S3, when the raw material is formed into granules by the molding equipment, the molding equipment used is an extrusion spheroidizer, a pot granulator, or a rotary kiln granulator. The granules are round, elliptical, or cylindrical, and the particle size ranges from 0.2 to 2 mm.

9. The method for preparing modified steel slag-based solar selective absorption and heat storage ceramic particles according to claim 4, characterized in that, In step S4, sintering is carried out in an air atmosphere, and the sintering procedure is as follows: heating rate 3-8℃ / min; holding the highest temperature point for 2-10h; the highest temperature point is 1200-1360℃; and finally, cooling with the furnace.

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