Multi-source solid waste collaborative modified gradient structure heat storage material and low-temperature preparation method

Abstract

The present disclosure provides a multi-source solid waste synergistically modified gradient structure heat storage material and a low-temperature preparation method thereof, and belongs to the technical field of solid waste resource utilization, energy storage and harmless disposal. The gradient structure heat storage material comprises a substrate layer, an interface layer and a heat storage layer which are sequentially stacked from top to bottom; wherein the substrate layer is an oxide mainly composed of steel slag; the heat storage layer comprises a tailing phase change material and paraffin microcapsules coated on the surface of the tailing phase change material; and the interface layer is a cementing material. Through the three-layer design of "substrate-interface-heat storage", the characteristics of multi-source solid waste are synergistically utilized to realize the synergistic optimization of thermal stability and heat storage density. At the same time, a low-temperature staged sintering process is adopted to significantly reduce energy consumption, improve heavy metal solidification efficiency, and comprehensively improve the performance of the heat storage material.

Description

Technical Field

[0001] This disclosure belongs to the technical field of solid waste resource utilization, energy storage and harmless disposal, specifically involving a gradient structure thermal storage material for synergistic modification of multi-source solid waste and a low-temperature preparation method. Background Technology

[0002] In the fields of solid waste resource utilization and thermal storage material research and development, existing technologies have shown significant results. For example, one of the existing technologies, Chinese patent application CN116969756A, proposes a super-thermal conductive thermal storage material based on industrial solid waste melting and reconstruction technology and its preparation method. This method improves the high-temperature oxidation resistance of the super-thermal conductive material through particle coating, and the prepared thermal storage material has high flexural strength, large thermal storage density, and high thermal conductivity, making it suitable for medium and high temperature environments. However, the high-temperature sintering process of this method (temperature ≥1200°C) results in high energy consumption and does not fully consider the synergistic effect of multi-source solid waste, limiting its application in the field of low-temperature thermal storage.

[0003] In addition, Chinese patent application CN119431001A, one of the existing technologies, provides a method for preparing a lightweight, pressure-resistant, heat-insulating, and noise-reducing material. This material has low density and thermal conductivity, making it suitable for heat insulation and noise reduction. However, this material is mainly designed for medium and low temperature environments, and its preparation process does not fully exploit the gradient heat storage potential of solid waste, failing to achieve breakthroughs in high-temperature heat storage density and thermal cycling stability.

[0004] To address the aforementioned technical shortcomings, this application proposes a gradient structure thermal storage material with multi-source solid waste synergistic modification and its low-temperature preparation method, aiming to solve the problems of high energy consumption, insufficient thermal storage density, and poor thermal cycling stability of existing high-temperature thermal storage materials. Summary of the Invention

[0005] This disclosure aims to at least address one of the technical problems existing in the prior art: high cost, poor performance, and inability to be applied on a large scale. It provides a gradient structure thermal storage material with multi-source solid waste synergistic modification and its low-temperature preparation method.

[0006] One aspect of this disclosure provides a gradient structure thermal storage material for synergistic modification of multi-source solid waste, the gradient structure thermal storage material comprising: a matrix layer, an interface layer, and a thermal storage layer stacked sequentially from top to bottom; wherein, The substrate layer is an oxide mainly composed of steel slag; The thermal storage layer includes tailings phase change material and paraffin microcapsules coated on the surface of the tailings phase change material. The interface layer is a cementitious material. Optionally, the mass of the matrix layer accounts for 55-65% of the total mass of the gradient structure thermal storage material; The mass of the thermal storage layer accounts for 25-35% of the total mass of the gradient structure thermal storage material; The mass of the interface layer accounts for 9-11% of the total mass of the gradient structure thermal storage material.

[0007] Optionally, the tailings phase change material is tailings containing the FeO / MnO eutectic phase.

[0008] Optionally, the cementing material includes water glass, a strong alkaline activator, and nano-SiC.

[0009] Optionally, the particle size of the nano-SiC is 20-50 nm.

[0010] In another aspect, this disclosure provides a low-temperature preparation method for the gradient structure thermal storage material described above, the low-temperature preparation method comprising: The steel slag is crushed and sieved, and the tailings phase change material is microwave activated. The treated steel slag and tailings phase change material are mixed to form a first mixture. The first mixture is dried, sintered, ground and sieved to obtain a first powder. After melting paraffin wax, stearic acid is added and stirred to obtain a second mixture. Water is added to the second mixture and dispersed to obtain a paraffin microcapsule precursor slurry. The paraffin microcapsule precursor slurry is uniformly impregnated into the treated first powder. After stirring evenly, it is subjected to static treatment, drying treatment and grinding and sieving treatment to form a heat storage layer on the matrix layer, thus obtaining the second powder. A gelling agent is prepared by mixing water glass and a strong alkaline activator and adding nano-SiC under stirring conditions. The second powder is mixed with the gelling agent, granulated and pressed into a cylindrical shape, and then subjected to segmented sintering treatment to obtain a gradient structure thermal storage material with synergistic modification of multi-source solid waste.

[0011] Optionally, the drying temperature of the first mixture is 100-120℃ and the time is 10-14h, and the sintering temperature is 900-1000℃ and the time is 1-3h. In the segmented low-temperature sintering process of cylindrical green blanks, the temperature of the first low-temperature sintering stage is 600-700℃ and the time is 0.5-1.5h, and the temperature of the second low-temperature sintering stage is 900-1000℃ and the time is 1.5-2.5h.

[0012] Optionally, the mass ratio of stearic acid to paraffin is (15-20):1.

[0013] Optionally, the mass ratio of the water glass to the strong alkaline activator is (2.5-3.5):1.

[0014] Optionally, the mass ratio of the second powder to the gelling agent is 1:(0.15-0.25).

[0015] This disclosure proposes a gradient structure thermal storage material for synergistic modification of multi-source solid waste and its low-temperature preparation method. The gradient structure thermal storage material includes a matrix layer, an interface layer, and a thermal storage layer stacked sequentially from top to bottom; wherein, the matrix layer is mainly composed of steel slag oxides; the thermal storage layer includes tailings phase change material and paraffin microcapsules coated on the surface of the tailings phase change material; and the interface layer is a cementing material. This disclosure utilizes the characteristics of multi-source solid waste through a three-layer design of "matrix-interface-thermal storage" to achieve synergistic optimization of thermal stability and thermal storage density. Simultaneously, the low-temperature segmented sintering process significantly reduces energy consumption and improves the efficiency of heavy metal solidification, thus achieving a comprehensive improvement in the performance of the thermal storage material. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the gradient structure thermal storage material for synergistic modification of multi-source solid waste according to a specific embodiment of this disclosure; Figure 2 This is a schematic flowchart illustrating the preparation method of gradient structure thermal storage material for synergistic modification of multi-source solid waste, which is a specific embodiment of this disclosure. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0018] like Figure 1 As shown, one aspect of this disclosure proposes a gradient structure thermal storage material for synergistic modification of multi-source solid waste. The gradient structure thermal storage material includes a matrix layer 110, an interface layer 120, and a thermal storage layer 130 stacked sequentially from top to bottom. The matrix layer 110 is an oxide mainly composed of steel slag. The thermal storage layer 130 includes tailings phase change material and paraffin microcapsules coated on the surface of the tailings phase change material. The interface layer 120 is a cementing material. This implementation method utilizes a three-layer design of "matrix-interface-heat storage" to synergistically leverage the characteristics of multi-source solid waste, thereby achieving synergistic optimization of thermal stability and heat storage density. At the same time, it adopts a low-temperature segmented sintering process to significantly reduce energy consumption and improve the efficiency of heavy metal solidification, thus achieving a comprehensive improvement in the performance of heat storage materials.

[0019] It should be noted that the matrix layer uses steel slag as the main component and exists in the form of oxides. After magnetic separation, the Fe content of the steel slag is ≤1%. For example, CaO accounts for the main component of the steel slag and AlO accounts for at least 2.5% of the mass.

[0020] It should be further noted that the thermal storage layer uses tailings as the main carrier and exists in the form of silicon dioxide. For example, the tailings phase change material is tailings containing FeO / MnO eutectic phase.

[0021] It should be noted that the cementing material includes water glass, a strong alkaline activator, and SiC, and the particle size of the nano-SiC particles is preferably 20-50 nm. In other words, the interface layer uses an alkaline activator composed of water glass and NaOH as a binder, and nano-SiC particles with a particle size ≤50 nm are added. This nano-SiC can significantly enhance the thermal insulation performance of steel slag within the 400-1000°C range.

[0022] It should be noted that, for the total mass of the gradient structure thermal storage material, the steel slag mass ratio of the matrix layer is 55-65%, for example, preferably 58-52%, and even more preferably 60%; the mass ratio of the interface layer components (water glass + alkali activator + nano SiC) is 9-11%, for example, preferably 10%; and the mass ratio of the thermal storage layer components (tailings phase change material + paraffin microcapsules) is 25-35%, for example, preferably 28-32%, and even more preferably 30%.

[0023] In this embodiment, based on the characteristics of diversified and low-cost solid waste, a stepped structure is constructed using steel slag as the main matrix. Alkaline heavy insoluble oxides are used to suppress the expansion / contraction stress of the phase change material and weaken the interfacial thermal resistance in the interface transition zone. Furthermore, an exogenous thermally conductive enhancing phase is used to improve heat transfer performance and compensate for the shortcomings of endogenous thermal conductivity, ultimately achieving low-cost multi-element synergistic modification of solid waste. Specifically, this embodiment proposes for the first time a red mud spherical [Ca(FeMn)(SiO)] thermal storage material with steel slag as the main core, exhibiting a honeycomb structure and a high morphology fraction of 68.4%, which effectively ensures the material's strength.

[0024] Furthermore, the gradient structure thermal storage material synergistically modified from multi-source solid waste in this embodiment possesses excellent thermal inertia performance and stable physicochemical properties.

[0025] like Figure 2 As shown, another aspect of this disclosure provides a low-temperature preparation method for a gradient structure thermal storage material, specifically including the following steps: First, the steel slag is crushed and sieved, and the tailings phase change material is microwave activated. The treated steel slag and tailings phase change material are mixed to form a first mixture. The first mixture is dried, sintered, ground and sieved to obtain a first powder.

[0026] Specifically, the above process includes the following specific steps: S1. Raw material pretreatment: The steel slag is crushed until it passes through a 400-mesh sieve, and the tailings are activated by 800W microwave for 5 minutes until the specific surface area is ≥500m² / kg. S2. Mixing: Mix the steel slag and tailings processed in step S1 at a mass ratio of 1:1. S3. Drying and calcining: The mixture is dried at 100-120℃ for 10-14h, and then sintered in a muffle furnace at 900-1000℃ for 1-3h to obtain matrix layer I; S4. Grinding: Grind the matrix layer I until it passes through a 200-mesh sieve to obtain the first powder.

[0027] It should be noted that in the first step mentioned above, the steel slag, which is the main raw material of the matrix layer, and the tailings, which is the phase change material of the heat storage layer, are pre-mixed and sintered in a certain proportion. The first powder obtained is an intermediate product of the two composites, which lays the foundation for the subsequent construction of the gradient functional layer.

[0028] In other preferred embodiments, 4-6 wt.% of water glass may be added during the mixing of steel slag and tailings in step S2.

[0029] Second, after melting paraffin wax, add stearic acid and stir to obtain a second mixture. Add water to the second mixture and disperse to obtain a paraffin microcapsule precursor slurry. The paraffin microcapsule precursor slurry is uniformly impregnated into the treated first powder. After stirring evenly, it is subjected to static treatment, drying treatment and grinding and sieving treatment to form a heat storage layer on the matrix layer, thus obtaining the second powder.

[0030] Specifically, the above process includes the following specific steps: S5. Preparation of paraffin microcapsules: Weigh paraffin and melt it in a vacuum oven at 65-75°C. Add stearic acid and stir for 10-20 minutes until fully mixed to obtain a mixture of paraffin and stearic acid. Then weigh the above mixture, add water, and disperse it in a high-speed disperser for 60 minutes to obtain a paraffin microcapsule precursor slurry. In step S5, the mass ratio of stearic acid to paraffin is (15-20):1, for example, (17-19):1 is preferred, and 18:1 is optimal.

[0031] S6. Impregnation: Weigh the paraffin microcapsule precursor slurry obtained in S5 and impregnate it evenly into the first powder obtained in step S4. After stirring thoroughly and letting it stand for 12 hours, dry and grind it until it passes through a 200-mesh sieve to obtain heat storage layer II, i.e., the second powder, on the substrate layer.

[0032] It should be noted that this step is equivalent to coating the surface of the tailings phase change material in the heat storage layer prepared in the previous step with a layer of paraffin microcapsules to protect the phase change material.

[0033] In other preferred embodiments, the mass ratio of stearic acid to paraffin in step S5 is 18:1.

[0034] Third, water glass and a strong alkaline activator are mixed, and nano-SiC is added under stirring conditions to obtain a gelling agent. The second powder is mixed with the gelling agent, granulated, and pressed into a cylindrical shape to obtain a gradient structure thermal storage material with synergistic modification of multi-source solid waste.

[0035] Specifically, the above process includes the following specific steps: S7. Preparation of gelling agent: Water glass and strong alkaline activator are mixed at a mass ratio of (2.5-3.5):1, and nano-SiC is added under stirring conditions to obtain gelling agent; In step S7, the mass ratio of water glass to strong alkaline activator is preferably (2.8-3.2):1, and optimally 3:1.

[0036] In step S7, the water glass used has a modulus of 13.4 and the nano-SiC particle size range is 20-50 nm.

[0037] S8. Extrusion Molding: The second powder obtained in S6 is mixed with the gelling agent prepared in S7 at a weight ratio of 1:(0.15-0.25), granulated, and pressed into cylindrical green bodies (diameter 10-20mm, height 5-15mm). The green bodies are then placed in a muffle furnace for segmented sintering. The first stage involves heating at 3°C / min to 600-700°C and holding for 0.5-1.5 hours to promote the formation of the calcium-iron garnet phase. The second stage involves further heating at 5°C / min to 900-1000°C and holding for 1.5-2.5 hours to trigger the in-situ reaction of the glass phase and achieve the stabilization and solidification of heavy metals, thus creating a gradient structure thermal storage material synergistically modified from multi-source solid waste.

[0038] In step S8, the mass ratio of the second powder to the gelling agent is 1:(0.18-0.22), with the optimal ratio being 1:0.2.

[0039] This embodiment proposes for the first time the synergistic modification of steel slag and tailings, with staged control of the roasting temperature. This allows the surface oxidation of the steel slag to fully react with the sulfides in the bulk phase, ultimately resulting in a stable phase (such as calcium iron garnet and a glassy phase) and a dense structure formed by sintering. This yields a thermal storage material with Ca iron garnet and CaO-Al2O3 as the main phases, exhibiting a lower sintering temperature and significantly reducing energy consumption. In other words, this embodiment breaks through the limitations of conventional thinking by employing a gradient structure thermal storage material preparation method. It combines materials with different performance characteristics using a two-stage sintering and in-situ reaction approach, ultimately achieving the production and application of low-cost, high-performance gradient structure thermal storage materials.

[0040] Furthermore, during the preparation process, this gradient structural design was adopted, selecting high calcium-to-aluminum ratio steel slag as the main body of matrix layer I to efficiently utilize the large specific surface area and high calcium content of steel slag, selecting tailings containing FeO / MnO eutectic phase as phase change material to store heat, selecting water glass with low thermal conductivity and strong alkaline activator as the cementing system, and nano-SiC as the reinforcing phase change material. The components complement each other and work together to achieve low-cost multi-element synergistic modification of solid waste.

[0041] The following will further illustrate the gradient structure thermal storage material and its preparation method based on specific embodiments: Example 1 The preparation method of gradient structure thermal storage material synergistically modified from multi-source solid waste in this example includes the following steps: First, the preparation of a first powder comprising a matrix layer and tailings composite powder includes the following steps: S1. Raw material pretreatment: Steel slag is magnetically separated to reduce Fe content to ≤1%. Its main chemical components are: CaO (45-50 wt%), SiO2 (25-30 wt%), Al2O3 (5-7 wt%), and MgO (3-5 wt%). It is then crushed using a jaw crusher and a double roll crusher, and passed through a 400-mesh standard sieve (particle size ≤38μm). Additionally, tailings from an iron ore mine, whose main mineral phases are quartz, hematite, and trace amounts of MnO, are selected. After grinding with a planetary ball mill, the tailings are microwave-activated at 800W for 5 minutes to achieve a specific surface area ≥500 m² / kg. S2. Mixing: Weigh the treated steel slag powder and tailings powder at a mass ratio of 1:1, and dry mix them in a planetary ball mill for 2 hours to ensure they are fully and evenly mixed. S3. Drying and calcining: The mixture is dried at 110°C for 12 hours to completely remove moisture, and then sintered in a muffle furnace at 950°C for 2 hours. After natural cooling, sintered blocks are obtained. S4. Grinding: The sintered block is put back into the planetary ball mill for grinding and passed through a 200-mesh sieve (particle size ≤74μm) to obtain the first powder; Second, construct the thermal storage layer, including the following steps: S5. Preparation of paraffin microcapsules: Weigh 50g of paraffin (model 58#, melting range 58-60°C) and melt it in a 70°C vacuum oven. Add 900g of stearic acid and stir for 15 minutes until fully mixed to obtain a mixture of paraffin and stearic acid. Then add 1900g of deionized water to the above mixture and place it in a high-speed disperser at a speed of 5000rpm for 60 minutes to obtain a milky white paraffin microcapsule precursor slurry. S6. Impregnation: Weigh 1000g of the first powder obtained in S4, place it in the above slurry, mechanically stir for 2 hours to ensure uniform impregnation, let it stand for 12 hours, transfer the mixture to an oven at 110°C to dry, grind it and pass it through a 200-mesh sieve to obtain the second powder. Third, shaping and final sintering, including the following steps: S7. Preparation of gelling agent: Water glass (modulus 3.3, Baume degree 40°Bé) and strong alkaline activator are mixed in a ratio of 3:1. 2% nano-SiC (average particle size 30nm) is added under stirring and stirred for 30 minutes until uniform to obtain gelling agent. S8. Extrusion Molding: 1000g of the second powder obtained in step S6 and 200g of the gelling agent prepared in step S7 are mixed at a weight ratio of 1:0.2 and granulated. The mixture is then cold-pressed at 20MPa to form a cylindrical green body (15mm in diameter, 10mm in height). This cylindrical green body is then subjected to low-temperature segmented sintering. The first stage of the low-temperature segmented sintering process involves heating at 3°C / min to 650°C and holding for 1 hour to promote the formation of calcium iron garnet (∑CaO-Al2O3-SiO2). The second stage involves further heating at 5°C / min to 950°C and holding for 2 hours to trigger the in-situ reaction of the CaO-Al2O3-SiO2 glass phase, achieving the stabilization and solidification of heavy metals (Cr). 6+ →Cr 3+ The material is cooled to room temperature in the furnace to obtain the final gradient structure thermal storage material with synergistic modification of multi-source solid waste.

[0042] It should be noted that in the first step mentioned above, the steel slag, which is the main raw material of the matrix layer, and the tailings, which is the phase change material of the heat storage layer, are pre-mixed and sintered in a certain proportion. The first powder obtained is an intermediate product of the two composites, which lays the foundation for the subsequent construction of the gradient functional layer.

[0043] As shown in Table 1, the performance of the samples prepared in Example 1 was further tested under the following conditions and methods: Thermal conductivity: Tested using a Netzsch LFA 467 HyperFlash® laser thermal conductivity meter. Before testing, the samples were coated with graphite layers on both sides. The test temperature range was 25-600°C. The value measured at 25°C was 3.48 W / (m·K) (average of three tests, standard deviation ±0.05).

[0044] Heat storage density and enthalpy: Tests were performed using a DSC 250 differential scanning calorimeter from TA Instruments (USA). A 10.00 mg sample was weighed and scanned from 30°C to 700°C at a rate of 10°C / min under a high-purity N2 atmosphere at a flow rate of 50 ml / min. Calculations using analytical software yielded a volumetric heat storage density of 1.22 MJ / m³, a mass heat storage enthalpy of 643 kJ / kg, and an average specific heat capacity of 3.04 × 10³ J / (kg·K) (3040 J / (kg·K)).

[0045] Thermal cycling stability: The sample was placed in a box furnace and subjected to 100 thermal cycles between 25°C and 600°C (heating rate 10°C / min, holding at both high and low temperatures for 10 minutes each). A DSC test was performed after every 20 cycles. After 100 cycles, the heat storage density decayed by 3.0%.

[0046] Thermal inertia fraction: The thermal inertia index P is calculated using the formula P=(kρc)^0.5 (where k is the thermal conductivity, ρ is the bulk density (measured as 2850 kg / m³ using the Archimedes displacement method), and c is the specific heat capacity). The calculated result is compared with the P value of the reference material (magnesia brick), yielding a thermal inertia fraction of 92.3%.

[0047] Environmental friendliness (heavy metal solidification rate): Samples were crushed to ≤75μm and subjected to toxicity leaching tests according to the US EPA TCLP 1311 standard method. The leachate was analyzed using ICP-MS, and the results showed hexavalent chromium (Cr). 6+ The solidification rate was >99.5%, and the leaching concentration of other heavy metal ions was far below the limit of the "Identification Standard for Hazardous Waste".

[0048] Table 1 Material property parameters of Example 1

[0049] This disclosure proposes a gradient structure thermal storage material with synergistic modification of multi-source solid waste and a low-temperature preparation method, which has the following advantages compared with the prior art: First, based on the characteristics of diversified and low-cost solid waste, this disclosure constructs a stepped structure with steel slag as the main matrix. It suppresses the expansion / contraction stress of phase change materials and weakens the interfacial thermal resistance in the interface transition zone through alkaline heavy insoluble oxides. It also improves the heat transfer performance by using exogenous thermally conductive enhancement phases to compensate for the lack of endogenous thermal conductivity. Ultimately, it achieves low-cost multi-element synergistic modification of solid waste. It is the first to propose the idea and method of preparing gradient structure thermal storage materials with multi-source solid waste synergistic modification, breaking through the traditional single-property modification concepts such as conditioning, doping, and coating.

[0050] Secondly, regarding the gradient structure design, this disclosure selects high calcium-to-aluminum ratio steel slag as the main body of matrix layer I to efficiently utilize the large specific surface area and high calcium content of steel slag, selects tailings containing FeO / MnO eutectic phase as phase change material to store heat, selects water glass with low thermal conductivity and strong alkaline activator as cementing system and nano-SiC as reinforcing phase change material. The components complement each other and work together to achieve low-cost multi-element synergistic modification of solid waste.

[0051] Third, this disclosure is the first to propose the synergistic modification of steel slag and tailings, and the segmented control of roasting temperature, so that the surface oxidation of steel slag and the sulfides in the bulk phase can fully react. The heat storage material with Ca ferrogarnet and CaO-Al2O3 as the main phase has a lower sintering temperature, which significantly reduces energy consumption. That is, it is the first time that solid waste has been applied on a large scale and industrially, optimizing thermal management capabilities and improving the technical and economic value of solid waste resource utilization.

[0052] Fourth, this disclosure proposes for the first time a red mud spherical [Ca(FeMn)(SiO)] thermal storage material with steel slag as the main core, which has a high morphology fraction of 68.4%, effectively ensuring the strength of the material. At the same time, the preparation method of the gradient structure thermal storage material breaks through the limitations of conventional thinking, and adopts the idea of ​​two-stage sintering and in-situ reaction to fuse and match materials with different performance characteristics, ultimately realizing the production and application of low-cost, high-performance gradient structure thermal storage materials.

[0053] Fifth, the gradient structure thermal storage material produced by the multi-source solid waste synergistic modification disclosed herein has excellent thermal inertia performance and stable physicochemical properties.

[0054] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A gradient structure thermal storage material synergistically modified from multi-source solid waste, characterized in that, The gradient structure thermal storage material comprises: a matrix layer, an interface layer, and a thermal storage layer, stacked sequentially from top to bottom; wherein... The substrate layer is an oxide mainly composed of steel slag; The thermal storage layer includes tailings phase change material and paraffin microcapsules coated on the surface of the tailings phase change material. The interface layer is a cementitious material.

2. The gradient structure thermal storage material for synergistic modification of multi-source solid waste according to claim 1, characterized in that, The mass of the matrix layer accounts for 55-65% of the total mass of the gradient structure thermal storage material; The mass of the thermal storage layer accounts for 25-35% of the total mass of the gradient structure thermal storage material; The mass of the interface layer accounts for 9-11% of the total mass of the gradient structure thermal storage material.

3. The gradient structure thermal storage material for synergistic modification of multi-source solid waste according to claim 1, characterized in that, The tailings phase change material is tailings containing the FeO / MnO eutectic phase.

4. The gradient structure thermal storage material for synergistic modification of multi-source solid waste according to claim 1, characterized in that, The cementing material includes water glass, a strong alkaline activator, and nano-SiC.

5. The gradient structure thermal storage material for synergistic modification of multi-source solid waste according to claim 4, characterized in that, The particle size of the nano-SiC is 20-50 nm.

6. A method for low-temperature preparation of a gradient structure thermal storage material as described in any one of claims 1-5, characterized in that, The low-temperature preparation method includes: The steel slag is crushed and sieved, and the tailings phase change material is microwave activated. The treated steel slag and tailings phase change material are mixed to form a first mixture. The first mixture is dried, sintered, ground and sieved to obtain a first powder. After melting paraffin wax, stearic acid is added and stirred to obtain a second mixture. Water is added to the second mixture and dispersed to obtain a paraffin microcapsule precursor slurry. The paraffin microcapsule precursor slurry is uniformly impregnated into the treated first powder. After stirring evenly, it is subjected to static treatment, drying treatment and grinding and sieving treatment to form a heat storage layer on the matrix layer, thus obtaining the second powder. Water glass and a strong alkaline activator are mixed, and nano-SiC is added under stirring conditions to obtain a gelling agent. The second powder is mixed with the gelling agent, granulated, and pressed into a cylindrical green body. The cylindrical green body is subjected to segmented low-temperature sintering treatment to obtain a gradient structure thermal storage material with multi-source solid waste synergistic modification.

7. The low-temperature preparation method according to claim 6, characterized in that, The drying temperature of the first mixture is 100-120℃ and the time is 10-14h; the sintering temperature is 900-1000℃ and the time is 1-3h. In the segmented low-temperature sintering process of cylindrical green blanks, the temperature of the first low-temperature sintering stage is 600-700℃ and the time is 0.5-1.5h, and the temperature of the second low-temperature sintering stage is 900-1000℃ and the time is 1.5-2.5h.

8. The low-temperature preparation method according to claim 6, characterized in that, The mass ratio of stearic acid to paraffin is (15-20):

1.

9. The low-temperature preparation method according to claim 6, characterized in that, The mass ratio of the water glass to the strong alkaline activator is (2.5-3.5):

1.

10. The low-temperature preparation method according to claim 6, characterized in that, The mass ratio of the second powder to the gelling agent is 1:(0.15-0.25).

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