Method for microwave sintering of aluminum dross

Abstract

The application discloses a method for microwave sintering and resource utilization of aluminum ash, which comprises the following steps: mixing aluminum ash with part of calcium-containing raw materials (including quicklime and limestone) to obtain a ball-mixed mixture; mixing the ball-mixed mixture with the remaining calcium-containing raw materials and microwave-assisted heating materials, and then uniformly mixing, briquetting and drying to obtain briquettes; sintering the briquettes in a microwave field; and cooling and crushing the sintered product to obtain a calcium aluminate product. The method can not only obtain a high-quality calcium aluminate product, but also effectively remove salts and harmful elements such as nitrogen in the aluminum ash; harmful element fluorine is solidified into calcium fluoride in the calcium aluminate product and serves as a useful component of a steelmaking desulfurizer. The method realizes harmless and resource utilization of the hazardous waste aluminum ash, and is simple in operation and friendly to the environment.

Description

Technical Field

[0001] This invention relates to a method for the resource utilization of aluminum ash, and more particularly to a method for the resource utilization of aluminum ash using microwave sintering, belonging to the technical field of metal recycling and comprehensive utilization of hazardous waste. Background Technology

[0002] Aluminum ash is a solid waste unavoidable during the production and processing of alumina and recycled aluminum. Because aluminum ash contains toxic and harmful substances such as aluminum nitride, aluminum carbide, and fluorides, it easily generates corrosive and flammable gases, as well as fluoride-containing wastewater, during storage and disposal. The large-scale stockpiling of aluminum ash not only occupies land resources but also poses a significant threat to the environment and public health.

[0003] Meanwhile, aluminum ash contains 30-70% aluminum, far exceeding the aluminum content in natural aluminum-bearing ores, making it extremely valuable for utilization. With the large-scale mining of bauxite, high-quality bauxite resources are becoming increasingly scarce. Therefore, recovering valuable element Al from aluminum ash can not only reduce the environmental harm caused by aluminum ash storage but also maximize the utilization of aluminum resources.

[0004] Currently, the comprehensive utilization processes for aluminum ash can be broadly classified into two categories: wet and pyrometallurgical processes. Wet processes utilize acid or alkali solutions for leaching and washing to remove nitrides, fluorides, and salts. Valuable aluminum mainly enters the product as metallic Al, Al₂O₃, Al(OH)₃, Al₂(SO₄)₃, polyaluminum chloride, and aluminates. However, wet processes require sophisticated equipment; the ammonia gas generated during the reaction needs to be absorbed in a dedicated reaction tower, and the wastewater may contain sulfur dioxide (F₂O₃). - It needs to be treated before it can be discharged. Pyrometallurgical processes are mainly divided into two approaches: the recovery and extraction of metallic aluminum and the synthesis of materials using aluminum ash. The recovery and extraction of metallic aluminum utilizes the low melting point of aluminum, heating it at high temperatures to melt it and thus separating the metallic aluminum. The synthesis of materials using aluminum ash mainly utilizes the elements such as Al, Ca, Mg, Si, and N in the ash, along with auxiliary materials, to sinter and produce high-value-added products such as calcium aluminate steelmaking desulfurizers, refractory materials, silon composite materials, and ceramic clear water bricks.

[0005] Due to the large demand for desulfurizing agents in the steel industry, synthesizing calcium aluminate-type steelmaking desulfurizing agents from aluminum ash can effectively solve the problem of large-scale aluminum ash stockpiling. Existing research mainly focuses on using traditional heating methods. Traditional heating involves a heat source transferring energy to the heated material through a medium. This method is slow, has significant heat loss, is unevenly heated, and suffers from heating lag, leading to reduced production efficiency and increased costs. Summary of the Invention

[0006] To address the main problems existing in current aluminum ash comprehensive utilization processes, the purpose of this invention is to provide a microwave sintering method for the resource utilization of aluminum ash. This method not only yields high-quality calcium aluminate products, but also effectively removes salts and harmful nitrogen elements from the aluminum ash. Harmful element fluorine is solidified into the calcium aluminate product in the form of calcium fluoride, serving as a useful component in steelmaking desulfurization agents. This method achieves the harmless and resource-based utilization of hazardous waste aluminum ash, and is simple to operate and environmentally friendly.

[0007] To achieve the above-mentioned technical objectives, this invention provides a method for the resource utilization of aluminum ash by microwave sintering. The method involves ball milling aluminum ash with a portion of calcium-containing raw materials to obtain a ball-milled mixture; the ball-milled mixture is then mixed with the remaining calcium-containing raw materials and microwave-assisted heating materials, followed by mixing, pressing, and drying to obtain lumps; the lumps are placed in a microwave field for sintering, and the sintered product is cooled and crushed to obtain calcium aluminate; the calcium-containing raw materials include quicklime and limestone.

[0008] The key to the technical solution of this invention lies in two aspects. Firstly, the calcium-containing raw materials used include quicklime and limestone. While both quicklime and limestone serve as calcium sources, their roles differ fundamentally. Quicklime plays a crucial role in the ball milling process. Mechanical ball milling fully exposes the aluminum nitride encapsulated in the aluminum ash. However, aluminum nitride readily reacts with moisture in the air, releasing harmful gases. By ball milling the aluminum ash together with a small amount of calcium-containing raw materials, quicklime prevents the hydrolysis of aluminum nitride during the ball milling process, thus avoiding the release of harmful gases. Secondly, limestone plays a vital role in the sintering process. Limestone can decompose at high temperatures, releasing carbon dioxide and forming gas channels, which is beneficial for the thorough sintering within the agglomerates. Simultaneously, limestone can fix and convert fluorine into stable calcium fluoride. Thirdly, the use of ball milling, through mechanical ball milling, fully activates the aluminum ash and calcium-containing raw materials, improving the subsequent sintering effect and the distribution of aluminum ash and calcium-containing raw materials. This facilitates the formation of gas channels within the agglomerates during sintering, promoting internal sintering. Thirdly, aluminum nitride in aluminum ash and the introduction of microwave-assisted heating materials can be used to improve the sintering effect of aluminum ash and calcium-containing raw materials. Based on the good thermal conductivity of aluminum nitride in aluminum ash (approximately 320 W / m·K), it is very beneficial for the subsequent microwave sintering process not to remove aluminum nitride in advance. Aluminum nitride and microwave-assisted heating materials have a synergistic effect, which can improve the heating rate of microwave sintering and improve the microwave sintering effect.

[0009] As a preferred embodiment, the calcium-containing raw material is composed of quicklime and limestone in a mass ratio of 1:

[0010] Composition (0.4~0.6). Quicklime and limestone, as calcium-containing raw materials, can both react with Al2O3 in aluminum ash to produce calcium aluminate. However, the introduction of an appropriate amount of limestone is highly beneficial for the conversion of AlN in aluminum ash. This is because AlN and metallic Al react with O2 in the air in the following ways: 1) 4Al + 3O2(g) = 2Al2O3 2) 4AlN + 3O2(g) = 2Al2O3 + 2N2(g). The generated Al2O3 forms a dense layer on the outside of the agglomerates, thus preventing external O2 from entering the agglomerates, making further removal of AlN from the agglomerates difficult. However, when using an appropriate proportion of limestone, at a temperature of around 850℃, CaCO3 begins to decompose, generating highly reactive CaO and CO2. This highly reactive CaO reacts with Al2O3 to produce calcium aluminate, and the release of CO2 forms gas channels within the agglomerates, which helps promote the complete removal of AlN from the agglomerates. Simultaneously, at high temperatures, CaCO3 reacts with F... - It readily reacts to produce CaF2, while also acting as a fluorine fixation agent. However, the amount of limestone added should not be too high, because the decomposition of CaCO3 is an endothermic reaction, and excessive limestone will lower the system temperature, causing heat loss.

[0011] As a preferred embodiment, the particle size of the aluminum ash is less than 0.1 mm.

[0012] As a preferred embodiment, the microwave-assisted heating material comprises silicon carbide and / or FeSiAl micro powder. Silicon carbide or FeSiAl micro powder is preferred as the microwave-assisted heating material primarily because of its excellent microwave absorption and attenuation capabilities, which reduces its addition amount in agglomerates. Furthermore, AlN has a high thermal conductivity, and by using silicon carbide or FeSiAl micro powder, which have good microwave absorption properties, the synergistic effect of both can achieve good microwave-assisted heating and denitrification. As a more preferred embodiment, the mass of the microwave-assisted heating material is 0.5% to 1% of the total mass of aluminum ash and calcium-containing raw materials.

[0013] As a preferred embodiment, the ratio of aluminum ash to the total mass of calcium-containing raw materials is controlled to be 1:(1.69~1.74) molar ratio of Al2O3 to CaO. Under the preferred ratio, high-quality calcium aluminate can be obtained from aluminum ash and calcium-containing raw materials, mainly producing a calcium aluminate-based steelmaking desulfurizing agent with 12CaO·7Al2O3 as the main phase.

[0014] As a preferred embodiment, the mass of calcium-containing raw material in the ball mill mixture accounts for 10-20% of the total mass of calcium-containing raw materials. The main purpose of ball milling a portion of the calcium-containing raw material together with aluminum ash is to prevent the AlN in the aluminum ash from reacting with water in the air to generate NH3. However, an excessively high proportion of calcium-containing raw material will reduce ball milling efficiency and increase energy consumption, which is detrimental to enterprise production.

[0015] As a preferred embodiment, the ball-milled mixture has a particle size distribution of 70-80% of particles smaller than 0.074 mm. This is primarily based on extensive research showing that AlN in aluminum ash is mainly distributed in finer particles, but some AlN is encapsulated by Al2O3, making it difficult to react directly with O2. By ball milling to an appropriate particle size, the specific surface area of ​​the aluminum ash can be significantly increased, exposing the AlN encapsulated within Al2O3. Simultaneously, ball milling enhances the activity of calcium oxide, facilitating the removal of nitrogen and the formation of calcium aluminate and CaF2. By controlling the grinding particle size of the aluminum ash, the distribution of fine particles within the compressed agglomerates can be improved. The +0.074 mm aluminum ash particles improve particle size matching within the agglomerates, contributing to the formation of gas diffusion channels during CaCO3 decomposition and AlN oxidation, significantly promoting nitrogen removal.

[0016] As a preferred embodiment, the sintering conditions are as follows: heating to 900–1200°C via microwave heating at a rate of 20–50°C / min, sintering first under a protective atmosphere for 20–60 min, and then sintering under an air atmosphere for 30–90 min. Based on the good thermal conductivity (approximately 320 W / m·K) and excellent electrical properties of aluminum nitride in aluminum ash, its presence can be fully utilized to improve microwave sintering in the early stages of sintering. In the later stages of sintering, primarily to form calcium aluminate and improve its grade, aluminum nitride is oxidized. Aluminum nitride not only decomposes into aluminum oxide, which then reacts with calcium oxide to form calcium aluminate, but also releases heat during oxidation, saving energy. If the calcination time under a protective atmosphere is too short, the heating rate will slow down due to premature oxidation of aluminum nitride. If the calcination time under a protective atmosphere is too long, it will affect the subsequent formation of calcium aluminate. If the calcination time under an air atmosphere is too short, some aluminum nitride will not be completely oxidized and converted into calcium aluminate, while if the calcination time under an air atmosphere is too long, it will increase sintering energy consumption. The protective atmosphere can be nitrogen or an inert atmosphere, such as argon. The calcination equipment used is a 2.45GHz vacuum microwave oven MW-L0316HV.

[0017] Compared with the prior art, the technical solution of the present invention brings the following beneficial technical effects:

[0018] 1) This invention adds calcium source in two steps. Quicklime and limestone work together to achieve good denitrification and fluorine fixation effect. N is mainly converted into N2 and F is mainly converted into CaF2. At the same time, a calcium aluminate-based steelmaking desulfurizer with 12CaO·7Al2O3 as the main phase is prepared, realizing the harmless and resource-based utilization of aluminum ash.

[0019] 2) By improving the grinding process, this invention avoids the oxidation of AlN during grinding, reduces the corrosion of equipment caused by NH3 emissions, and also improves the distribution of particles inside the agglomerates, which plays a good role in promoting the formation of gas channels.

[0020] 3) This invention utilizes the characteristics of microwave heating speed, uniform heating and high energy utilization, which greatly shortens the sintering time and significantly improves production efficiency. Attached Figure Description

[0021] Figure 1 The image shows the XRD pattern of the calcium aluminate product from Example 1. Detailed Implementation

[0022] The following examples are intended to further illustrate the present invention, but not to limit the scope of protection of the claims of the present invention.

[0023] Comparative Example 1

[0024] Using aluminum ash (Al2O3 content 77.1%, AlN content 21.4%, F content 3.0%), quicklime, and FeSiAl micro powder from a recycled aluminum plant as raw materials, the total addition ratio of aluminum ash to quicklime was controlled at an Al2O3 to CaO molar ratio of 1:1.70. 20% of the total quicklime was mixed with the aluminum ash and ball-milled until the particle size was less than 0.074 mm, reaching a proportion of 75%. Then, the remaining quicklime and silicon carbide were added to the ball-milled material, with the silicon carbide addition amount being 1% of the total mass of aluminum ash and quicklime. The mixture was thoroughly mixed, pressed into briquettes, and dried. Finally, the pressed briquettes were placed in a microwave field for sintering. The heating rate was controlled at 30℃ / min, the sintering temperature at 1100℃, the first stage of nitrogen atmosphere protection time was 30 min, and the second stage of air atmosphere heat preservation time was 60 min. The calcined product was naturally cooled and crushed to obtain a calcium aluminate-based steelmaking desulfurizing agent. Tests showed that the product contained 93.1% calcium aluminate, 78.2% nitrogen removal rate, and 75.8% fluoride curing rate.

[0025] Comparative Example 2

[0026] Using aluminum ash (Al2O3 content 77.1%, AlN content 21.4%, F content 3.0%), limestone, and FeSiAl micro powder from a recycled aluminum plant as raw materials; the total addition ratio of aluminum ash and limestone was controlled to have a molar ratio of Al2O3 to CaO of 1:1.70; 20% of the total limestone was mixed with the aluminum ash and ball-milled until the particle size was less than 0.074 mm, accounting for 75%; then the remaining limestone and silicon carbide were added to the ball-milled material, with the silicon carbide addition amount being 1% of the total mass of aluminum ash and quicklime; the mixture was thoroughly mixed, pressed into lumps, and dried; finally, the pressed lumps were placed in a microwave field for sintering; the heating rate was controlled at 30℃ / min, the sintering temperature was 1100℃, the first stage nitrogen atmosphere protection time was 30min, and the second stage air atmosphere heat preservation time was 60min; the calcined product was naturally cooled and crushed to obtain a calcium aluminate-based steelmaking desulfurizing agent product. Tests showed that the product contained 91.7% calcium aluminate, 73.1% nitrogen removal rate, and 79.2% fluoride curing rate.

[0027] Comparative Example 3

[0028] Using aluminum ash (Al2O3 content 77.1%, AlN content 21.4%, F content 3.0%) produced by a recycled aluminum plant and calcium-containing raw materials as raw materials; the calcium-containing raw materials consist of quicklime and limestone, with a controlled mass ratio of quicklime:limestone = 1:0.5; the total addition ratio of aluminum ash and calcium-containing raw materials is controlled at an Al2O3 to CaO molar ratio of 1:1.70; 20% of the total addition of calcium-containing raw materials is mixed with aluminum ash and ball-milled until the particle size is less than 0.074mm, accounting for 75%; then, this part of the material is thoroughly mixed with the remaining calcium-containing raw materials, pressed into lumps, and dried; finally, the pressed lumps are placed in a microwave field for sintering; the heating rate is controlled at 30℃ / min, the sintering temperature is 1100℃, the first stage nitrogen atmosphere protection time is 30min, and the second stage air atmosphere heat preservation time is 60min; the calcined product is naturally cooled and crushed to obtain calcium aluminate-based steelmaking desulfurizing agent. Tests showed that the product contained 72.9% calcium aluminate, 68.5% nitrogen removal, and 70.7% fluoride curing.

[0029] Comparative Example 4

[0030] Using aluminum ash (Al2O3 content 77.1%, AlN content 21.4%, F content 3.0%) produced by a recycled aluminum plant, along with calcium-containing raw materials and FeSiAl micro powder, as raw materials; the calcium-containing raw materials consist of quicklime and limestone, with a controlled mass ratio of quicklime:limestone = 1:0.5; the total addition ratio of aluminum ash to calcium-containing raw materials is controlled, with an Al2O3 to CaO molar ratio of 1:1.70; 20% of the total addition of calcium-containing raw materials is mixed with aluminum ash and ball-milled until the particle size is less than 0.074 mm. For example, the content of calcium-containing raw materials is 50%; then the remaining calcium-containing raw materials and silicon carbide are added to the ball-milled material, with the silicon carbide addition amount being 1% of the total mass of aluminum ash and calcium-containing raw materials; the mixture is thoroughly mixed, pressed into briquettes, and dried; finally, the pressed briquettes are placed in a microwave field for sintering; the heating rate is controlled at 30℃ / min, the sintering temperature is 1100℃, the first stage nitrogen atmosphere protection time is 30min, and the second stage air atmosphere holding time is 60min; the calcined product is naturally cooled and crushed to obtain a calcium aluminate-based steelmaking desulfurizing agent product. Testing shows that the theoretical calcium aluminate content in the product is 88.4%, the nitrogen removal rate is 68.5%, and the fluoride curing rate is 71.2%.

[0031] Comparative Example 5

[0032] Aluminum ash (Al2O3 content 77.1%, AlN content 21.4%, F content 3.0%) produced by a recycled aluminum plant, along with calcium-containing raw materials and FeSiAl micro powder, were used as raw materials. The calcium-containing raw materials consisted of quicklime and limestone, with a controlled mass ratio of quicklime:limestone = 1:0.5. The total addition ratio of aluminum ash to calcium-containing raw materials was controlled, with the molar ratio of Al2O3 to CaO being 1:1.70. 20% of the total addition of calcium-containing raw materials was mixed with aluminum ash and ball-milled until the particle size was less than 0.074 mm, accounting for 75%. Then, the remaining calcium-containing raw materials and silicon carbide were added to the ball-milled material, with the silicon carbide addition amount being 1% of the total mass of aluminum ash and calcium-containing raw materials. The mixture was thoroughly mixed, pressed into lumps, and dried. Finally, the pressed lumps were placed in a microwave field for sintering, with the heating rate controlled at 30℃ / min and the sintering temperature at 1100℃, all under an air atmosphere. The calcined product was naturally cooled and crushed to obtain a calcium aluminate-based steelmaking desulfurizing agent. Tests showed that the product contained 92.3% calcium aluminate, 76.8% nitrogen removal rate, and 81.5% fluoride curing rate.

[0033] Example 1

[0034] Using aluminum ash (Al2O3 content 77.1%, AlN content 21.4%, F content 3.0%) produced by a recycled aluminum plant, along with calcium-containing raw materials and FeSiAl micro powder, as raw materials; the calcium-containing raw materials consist of quicklime and limestone, with a controlled mass ratio of quicklime:limestone = 1:0.5; the total addition ratio of aluminum ash to calcium-containing raw materials is controlled, with an Al2O3 to CaO molar ratio of 1:1.70; 20% of the total addition of calcium-containing raw materials is mixed with aluminum ash and ball-milled until the particle size is less than 0.074 mm. For example, the content of calcium-containing raw materials is 75%. Then, the remaining calcium-containing raw materials and silicon carbide are added to the ball-milled material. The amount of silicon carbide added is 1% of the total mass of aluminum ash and calcium-containing raw materials. The mixture is thoroughly mixed, pressed into briquettes, and dried. Finally, the pressed briquettes are placed in a microwave field for sintering. The heating rate is controlled at 30℃ / min, the sintering temperature is 1100℃, the first stage nitrogen atmosphere protection time is 30min, and the second stage air atmosphere holding time is 60min. After natural cooling and crushing, the calcined product is obtained as a calcium aluminate-based steelmaking desulfurizing agent. The product has a theoretical calcium aluminate content of 98.2%, a nitrogen removal rate of 99.1%, and a fluoride curing rate of 99.7%.

[0035] Example 2

[0036] Aluminum ash (Al₂O₃ content 77.1%, AlN content 21.4%, F content 3.0%) produced by a recycled aluminum plant, along with calcium-containing raw materials and silicon carbide, were used as raw materials. The calcium-containing raw materials consisted of quicklime and limestone, with a controlled mass ratio of quicklime:limestone = 1:0.4. The total addition ratio of aluminum ash to calcium-containing raw materials was controlled, with an Al₂O₃ to CaO molar ratio of 1:1.73. 18% of the total calcium-containing raw materials were mixed with the aluminum ash and ball-milled until the particle size was less than 0.074 mm, resulting in a ratio of 70:1. %; then the remaining calcium-containing raw materials and silicon carbide were added to the ball-milled material, with the silicon carbide addition amount being 0.5% of the total mass of aluminum ash and calcium-containing raw materials; thoroughly mixed, pressed into briquettes, and dried; finally, the pressed briquettes were placed in a microwave field for sintering; the heating rate was controlled at 20℃ / min, the sintering temperature was 1200℃, the first stage nitrogen atmosphere protection time was 30min, and the second stage air atmosphere holding time was 60min; the calcined product was naturally cooled and crushed to obtain a calcium aluminate-based steelmaking desulfurizing agent product. Testing showed that the theoretical calcium aluminate content in the product was 99.0%, the nitrogen removal rate was 99.6%, and the fluoride curing rate was 99.8%.

[0037] Example 3

[0038] Using aluminum ash (Al₂O₃ content 77.1%, AlN content 21.4%, F content 3.0%) produced by a recycled aluminum plant, along with calcium-containing raw materials and FeSiAl micro powder, as raw materials; the calcium-containing raw materials consist of quicklime and limestone, with a controlled mass ratio of quicklime:limestone = 1:0.6; the total addition ratio of aluminum ash to calcium-containing raw materials is controlled at an Al₂O₃ to CaO molar ratio of 1:1.69; 12% of the total addition of calcium-containing raw materials is mixed with aluminum ash and ball-milled until the particle size is less than 0.074 mm. For example, the content of calcium-containing raw materials was 73%. Then, the remaining calcium-containing raw materials and silicon carbide were added to the ball-milled material. The amount of silicon carbide added was 1% of the total mass of aluminum ash and calcium-containing raw materials. The mixture was thoroughly mixed, pressed into briquettes, and dried. Finally, the pressed briquettes were placed in a microwave field for sintering. The heating rate was controlled at 50℃ / min, the sintering temperature was 900℃, the first stage of nitrogen atmosphere protection time was 30 min, and the second stage of air atmosphere holding time was 60 min. After natural cooling and crushing, the calcined product was obtained as a calcium aluminate-based steelmaking desulfurizing agent. Testing showed that the theoretical calcium aluminate content in the product was 97.8%, the nitrogen removal rate was 98.6%, and the fluoride curing rate was 99.4%.

[0039] Example 4

[0040] Aluminum ash (Al₂O₃ content 77.1%, AlN content 21.4%, F content 3.0%) produced by a recycled aluminum plant, along with calcium-containing raw materials and silicon carbide, were used as raw materials. The calcium-containing raw materials consisted of quicklime and limestone, with a controlled mass ratio of quicklime:limestone = 1:0.4. The total addition ratio of aluminum ash to calcium-containing raw materials was controlled, with an Al₂O₃ to CaO molar ratio of 1:1.74. 15% of the total calcium-containing raw materials were mixed with the aluminum ash and ball-milled until the particle size was less than 0.074 mm, resulting in a ratio of 80:1. %; then the remaining calcium-containing raw materials and silicon carbide were added to the ball-milled material, with the silicon carbide addition amount being 0.6% of the total mass of aluminum ash and calcium-containing raw materials; thoroughly mixed, pressed into briquettes, and dried; finally, the pressed briquettes were placed in a microwave field for sintering; the heating rate was controlled at 40℃ / min, the sintering temperature was 1000℃, the first stage nitrogen atmosphere protection time was 30min, and the second stage air atmosphere holding time was 60min; the calcined product was naturally cooled and crushed to obtain a calcium aluminate-based steelmaking desulfurizing agent product. Testing showed that the theoretical calcium aluminate content in the product was 98.5%, the nitrogen removal rate was 99.3%, and the fluoride curing rate was 99.7%.

[0041] Example 5

[0042] Using aluminum ash (Al2O3 content 77.1%, AlN content 21.4%, F content 3.0%) produced by a recycled aluminum plant, along with calcium-containing raw materials and FeSiAl micro powder, as raw materials; the calcium-containing raw materials consist of quicklime and limestone, with a controlled mass ratio of quicklime:limestone = 1:0.5; the total addition ratio of aluminum ash to calcium-containing raw materials is controlled, with an Al2O3 to CaO molar ratio of 1:1.71; 10% of the total addition of calcium-containing raw materials is mixed with aluminum ash and ball-milled until the particle size is less than 0.074 mm. The content of calcium-containing raw materials was 78%. Then, the remaining calcium-containing raw materials and silicon carbide were added to the ball-milled material, with the silicon carbide addition amount being 0.8% of the total mass of aluminum ash and calcium-containing raw materials. The mixture was thoroughly mixed, pressed into briquettes, and dried. Finally, the pressed briquettes were placed in a microwave field for sintering. The heating rate was controlled at 30℃ / min, the sintering temperature was 1100℃, the first stage of nitrogen atmosphere protection time was 30min, and the second stage of air atmosphere holding time was 60min. After natural cooling and crushing, the calcined product was obtained as a calcium aluminate-based steelmaking desulfurizing agent. Testing showed that the theoretical calcium aluminate content in the product was 98.9%, the nitrogen removal rate was 99.1%, and the fluoride curing rate was 99.5%.

Claims

1. A method for the resource utilization of aluminum ash by microwave sintering, characterized in that: Aluminum ash is mixed with some calcium-containing raw materials by ball milling to obtain a ball-milled mixture. The ball-milled mixture is then mixed with the remaining calcium-containing raw materials and microwave-assisted heating materials, and successively mixed, pressed into lumps, and dried to obtain lumps. The lumps are then placed in a microwave field for sintering. The sintered product is cooled and crushed to obtain calcium aluminate. The calcium-containing raw materials consist of quicklime and limestone. The mass of calcium-containing raw materials in the ball mill mixture accounts for 10-20% of the total mass of calcium-containing raw materials; The calcium-containing raw material is composed of quicklime and limestone in a mass ratio of 1:(0.4~0.6); The sintering conditions are as follows: heating to 900-1200°C by microwave heating at a heating rate of 20-50°C / min, sintering for 20-60 min under a protective atmosphere, and then sintering for 30-90 min under an air atmosphere. The ball milled mixture has a particle size of less than 0.074 mm with a mass ratio of 70-80%.

2. The method for the resource utilization of aluminum ash by microwave sintering according to claim 1, characterized in that: The particle size of the aluminum ash is less than 0.1 mm.

3. The method for the resource utilization of aluminum ash by microwave sintering according to claim 1, characterized in that: The microwave-assisted heating material includes silicon carbide and / or FeSiAl micro powder.

4. A method for the resource utilization of aluminum ash by microwave sintering according to any one of claims 1 to 3, characterized in that: The ratio of aluminum ash to the total mass of calcium-containing raw materials is controlled to be 1:(1.69~1.74) molar ratio of Al2O3 to CaO.

5. A method for the resource utilization of aluminum ash by microwave sintering according to claim 1 or 3, characterized in that: The mass of the microwave-assisted heating material is 0.5-1% of the total mass of aluminum ash and calcium-containing raw materials.

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