Method for preparing Al-Si-Ca alloy, AlF3 and MgF2 through regeneration of cut silicon waste and CaF2-MgO waste residues

Abstract

The invention discloses a method for preparing low-oxygen Al-Si-Ca alloy, AlF3 and MgF2 through regeneration of diamond wire cutting silicon waste and CaF2-MgO waste residues, and belongs to the technical field of secondary utilization of solid waste resources. The method comprises the following steps: (1) uniformly mixing the diamond wire cutting silicon waste material, CaF2-MgO waste residue and metal Al particles to obtain a mixed material; (2) the mixed material obtained in the step (1) is placed under the micro-negative pressure condition formed by inert atmosphere adjustment, electromagnetic induction heating is conducted to enable the mixed material to be molten, constant-temperature reduction smelting is conducted, and a uniform Al-Si-Ca alloy melt, molten residues and volatile products AlF3 and MgF2 are obtained; and (3) the volatile products AlF3 and MgF2 are condensed and collected, and after the Al-Si-Ca alloy melt and molten residues are cooled, a low-oxygen Al-Si-Ca alloy ingot and reduction residues are obtained through slag-gold separation. According to the method, various wastes are comprehensively utilized in a simple, convenient, efficient and clean manner, diversified high-added-value products are obtained, resource consumption is saved, and environmental pollution is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of secondary utilization of solid waste resources, and relates to a method for cutting silicon waste and CaF2-MgO waste slag to regenerate and prepare Al-Si-Ca alloy, AlF3 and MgF2. Background Art

[0002] With the rapid development of the photovoltaic industry, solar energy has been widely used as a clean energy source, and the demand for solar-grade crystalline silicon wafers has increased significantly. However, in the manufacturing process of silicon wafers, about 35% to 40% of crystalline silicon becomes diamond wire cutting silicon waste. Because its particle size is smaller than PM2.5 particulate matter, it is considered to be a solid waste that is harmful to the environment and human health. Diamond wire cutting silicon waste is mainly composed of Si and O elements, in which oxygen usually exists in the form of SiO2. If it is not recovered and treated in time, it will not only cause environmental pollution, but also waste precious Si resources. At present, a variety of methods have been explored for exploring the recycling of diamond wire cutting silicon waste, such as vacuum refining, induction melting, Al-Si alloying, H2SO4 or HCl pickling, etc. However, the existing methods have limited effects in removing O impurities (removing the SiO2 layer on the surface of diamond wire cutting silicon waste) and have not yet been widely used in industrial production.

[0003] At present, fluorine-containing slag is widely used in metallurgical processes such as ladle metallurgy, secondary metallurgy and electroslag refining (ESR). Among them, CaF2-MgO slag and CaF2-CaO-MgO slag can effectively remove S and P impurities in the steelmaking process. After steelmaking, the slag containing impurities will form CaF2-MgO waste slag containing F element. If the waste slag is not recycled, it will not only cause environmental pollution, but also waste Ca and Mg resources.

[0004] Al-Si-Ca alloy has the advantages of corrosion resistance, heat resistance and long-lasting strength. It has been widely used in aerospace, electrical appliances and building structural materials. However, the production of Al-Si-Ca alloy usually requires the smelting of high-purity Al, Si and Ca raw materials, and the production process is costly. AlF3 as a flux can reduce the melting point of Al2O3, enhance the conductivity of the electrolyte, and improve the efficiency and quality of aluminum production. MgF2 has excellent corrosion resistance and optical properties and is suitable for the manufacture of infrared windows and resonators. AlF3 is generally prepared by a low-temperature heat treatment growth method, while MgF2 is synthesized by dissolving magnesium chloride in hydrofluoric acid (HF) and deionized water by a fluoridation method. The above methods for preparing AlF3 and MgF2 will produce waste acid, causing environmental problems.

[0005] At present, there is no clean and efficient method for simultaneously recycling diamond wire cutting silicon waste and CaF2-MgO waste slag to prepare low-oxygen Al-Si-Ca alloy, AlF3 and MgF2.

[0006] Therefore, it is necessary to provide a method for regenerating diamond wire cutting silicon waste and CaF2-MgO waste slag to prepare low-oxygen Al-Si-Ca alloy, AlF3, and MgF2, so as to recycle multiple wastes at the same time in an efficient and clean manner to obtain rich and diverse recycled resources, on the one hand, providing a new way to reduce resource consumption and save resources; on the other hand, providing a new idea for reducing environmental pollution and truly achieving waste treatment with waste. Summary of the invention

[0007] In order to overcome the problems in the background technology, the present invention uses Si in diamond wire cutting silicon waste as the Si source for preparing Al-Si alloy, and uses CaF2-MgO waste slag to deoxidize diamond wire cutting silicon waste, introduces Ca in the slag into the alloy, and fixes F in the slag by Al and Mg, which can simultaneously achieve deoxidation, Ca doping and F fixation, thereby preparing three products of low-oxygen Al-Si-Ca alloy, AlF3 and MgF2. The present invention simultaneously utilizes multiple waste materials in a clean, simple and efficient manner, obtains diversified reuse resources, helps to save resource consumption, improves environmental friendliness, and truly achieves waste treatment.

[0008] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0009] The method comprises the following steps:

[0010] (1) Diamond wire cutting silicon waste, CaF2-MgO waste slag and metal Al particles are uniformly mixed to obtain a mixed material;

[0011] (2) placing the mixed material obtained in step (1) under a slightly negative pressure condition formed by adjusting an inert atmosphere, performing electromagnetic induction heating to melt the mixed material, and performing constant temperature reduction smelting to obtain a uniform Al-Si-Ca alloy melt, a molten residue, and volatile products AlF3 and MgF2.

[0012] (3) The volatile products AlF3 and MgF2 are condensed and collected, and after the Al-Si-Ca alloy melt and the molten residue are cooled to room temperature, low-oxygen Al-Si-Ca alloy ingots and reduced residues are obtained after slag-gold separation.

[0013] Preferably, in step (1), the mass of silicon waste from diamond wire cutting accounts for 25-40% of the total mass of the mixed material, the mass of CaF2-MgO waste slag added accounts for 15-30% of the total mass of the mixed material, and the mass of metal Al particles added accounts for 45-50% of the total mass of the mixed material.

[0014] Preferably, in the CaF2-MgO waste slag, the content of MgO accounts for 12 to 30% of the total mass of the CaF2-MgO waste slag.

[0015] Preferably, in step (2), the reduction smelting temperature is 1450-1500° C., and the reduction smelting time is 2 hours.

[0016] Preferably, in step (2), the inert atmosphere is adjusted to form a slight negative pressure in the range of 6.5×10 3 ~4×10 4 Pa.

[0017] Preferably, in step (3), the volatile products AlF3 and MgF2 are collected when they are condensed to 700-850°C.

[0018] Preferably, in step (3), the Al-Si-Ca alloy ingot and the reduction residue are separated by mechanical cutting or wire cutting.

[0019] Preferably, the diamond wire cutting silicon waste contains both SiO2 and Si, and SiO2 is wrapped on the surface of single substance Si.

[0020] At high temperature, a reduction reaction occurs between Al, CaF2 and SiO2, generating Si and Ca, which are then incorporated into the alloy to form an Al-Si-Ca alloy. At the same time, AlF3 volatilizes and Al2O3 is incorporated into the slag. Next, the formed Ca reduces MgO to obtain Mg and CaO. Mg acts as a reducing agent to reduce CaF2 to form CaO and MgF2. AlF3 and MgF2 can be collected by volatilization. Finally, CaO and Al2O3 further react to form CaAl2O4 slag. In addition, induction heating is used in the reduction smelting process to apply electromagnetic force to the reduction process. Since the electrical conductivity of the Al-Si-Ca alloy is much greater than that of the slag, the alloy melt moves in the direction of the electromagnetic force, while the slag migrates in the opposite direction of the electromagnetic force, promoting the separation of the alloy and the slag.

[0021] Beneficial effects of the present invention:

[0022] 1. The present invention can utilize diamond wire cutting silicon waste and CaF2-MgO waste slag materials to carry out Al reduction smelting to prepare three high value-added products, Al-Si-Ca alloy, AlF3 and MgF2, while recycling and reusing a variety of waste materials, and outputting relatively abundant high value-added products, with excellent comprehensive utilization effect and good waste treatment effect.

[0023] 2. In the method of the present invention, since the alloy melt is affected by the Lorentz force, electromagnetic stirring is generated in the container, Si and Ca are evenly distributed in the alloy during the heat and mass transfer process, the alloy melt and slag are affected differently by the electromagnetic force during the smelting process and can be well separated, and reduction smelting is carried out under slightly negative pressure conditions combined with induction heating, which is conducive to the volatilization of the products AlF3 and MgF2 and their collection in the condenser.

[0024] 3. The present invention realizes the low-cost and environmentally friendly recycling of diamond wire cutting silicon waste and CaF2-MgO waste slag.

[0025] 4. The method of the present invention is simple, has a high utilization rate of waste materials, and the obtained high value-added products are of good quality, which is suitable for industrial promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the process flow of the present invention;

[0027] Figure 2 This is a longitudinal macroscopic physical picture of the separation of alloy and slag after electromagnetic induction melting in Example 1 of the present invention;

[0028] Figure 3 This is the EDS-Mapping of the separation interface between the Al-Si-Ca alloy and the residue in Example 1 of the present invention;

[0029] Figure 4 This is a diagram showing the XRD analysis results of the volatiles in Example 1 of the present invention;

[0030] Figure 5 EDS-Mapping of the separation interface between the Al-Si-Ca alloy and the residue in Example 2 of the present invention;

[0031] Figure 6 This is a diagram showing the XRD analysis results of the oxygen-enriched residue in Example 2 of the present invention. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the described contents.

[0033] All chemical reagents not specifically described in the examples of the present invention were commercially available analytically pure.

[0034] In the embodiment of the present invention, the masses of diamond wire cut silicon waste, CaF2-MgO waste slag, and metal Al particles are shown in Table 1.

[0035] Table 1

[0036]

[0037] Example 1

[0038] A method for cutting silicon waste and regenerating CaF2-MgO waste slag to prepare Al-Si-Ca alloy, AlF3, MgF2 (see Figure 1 ), the specific steps are as follows:

[0039] (1) Diamond wire cutting silicon waste (oxygen content of 4.7%) with a purity of 94.3% and CaF2-MgO waste slag (MgO content of 12 wt.%) were mixed evenly using a vibration mill, and metal Al particles (purity of 99.9%) were added to obtain a mixed material.

[0040] (2) The mixed material is placed in 1×10 4 Under slightly negative pressure of Pa (inert atmosphere adjustment), electromagnetic induction heating to a temperature of 1450°C is used to completely melt it, and constant temperature reduction smelting is performed for 2 hours to obtain a uniform Al-Si-Ca alloy melt, molten residue, and volatile products AlF3 and MgF2.

[0041] (3) After the volatile products AlF3 and MgF2 are condensed to 700°C, they are collected in a condenser. After the Al-Si-Ca alloy melt and the molten residue are cooled to room temperature, they are separated by mechanical cutting or wire cutting to obtain a low-oxygen Al-Si-Ca alloy ingot and a reduced residue.

[0042] Macroscopic image of the separation of Al-Si-Ca alloy and molten residue after electromagnetic induction melting is shown in Figure 2 ,from Figure 2 It can be seen that the oxygen impurities in the diamond wire sawing silicon waste are enriched in the residue, and no oxygen-rich residue is observed in the alloy.

[0043] The EDS-Mapping analysis results of the separation interface between the Al-Si-Ca alloy and the residue in this embodiment are shown in Figure 3 ,pass Figure 3 It can be seen that no oxygen element was obviously detected inside the alloy, and the oxygen impurities in the diamond wire cutting silicon waste were enriched in the residue; the F element was enriched in the same position as the oxygen impurities, proving that F did not enter and pollute the alloy; the Ca element was not only enriched in the residue, but also distributed in the alloy.

[0044] The XRD analysis results of the volatiles in this example are shown in Figure 4 ,pass Figure 4 It can be seen that in this embodiment, the volatiles are indeed AlF3 and MgF2.

[0045] After testing and analysis, the main components of the Al-Si-Ca alloy in this embodiment are Al, Si and Ca, and their contents are respectively Al: 72.99wt.%, Si: 17.98wt.%, Ca: 9.03wt.%; the oxygen content is 0.0065wt.%. The purity of the mixture of AlF3 and MgF2 is 98.2wt.%, and its main components are respectively F: 37.23wt.%, Mg: 13.62wt.%, Al: 47.31wt.%; the main impurities and their contents are respectively Si: 0.54wt.%, Ca: 1.30wt.%.

[0046] It can be seen from the above component detection results that the high value-added products (Al-Si-Ca alloy, AlF3 and MgF2) prepared from waste materials in the present invention have very low impurity content and high product quality.

[0047] Example 2

[0048] A method for preparing Al-Si-Ca alloy, AlF3 and MgF2 by cutting silicon waste and regenerating CaF2-MgO waste slag, the specific steps are as follows:

[0049] (1) Diamond wire cutting silicon waste (oxygen content of 4.7%) with a purity of 94.3% and CaF2-MgO waste slag (MgO content of 15 wt.%) were mixed evenly using a vibration mill, and metal Al particles (purity of 99.9%) were added to obtain a mixed material.

[0050] (2) Place the mixed material at 6.5×10 3 Pa (inert atmosphere adjustment, the inert atmosphere is Ar gas) is subjected to electromagnetic induction heating to 1470°C to completely melt it, and then isothermal reduction smelting is performed for 2 hours to obtain a uniform Al-Si-Ca alloy melt, molten residue, and volatile product AlF3.

[0051] (3) After the volatile product AlF3 is condensed to 800°C, it is collected in a condenser. After the Al-Si-Ca alloy melt and the molten residue are cooled to room temperature, they are separated by mechanical cutting or wire cutting to obtain a low-oxygen Al-Si-Ca alloy ingot and a reduced residue.

[0052] The EDS-Mapping analysis results of the separation interface between the Al-Si-Ca alloy and the residue in this embodiment are shown in Figure 5 ,pass Figure 5 It can be seen that no oxygen element was obviously detected inside the alloy, but a large amount of oxygen impurities were detected in the residue; the F element was enriched in the same position as the oxygen impurities, proving that F did not enter the alloy and cause alloy contamination; the Ca element was not only enriched in the residue, but also distributed in the alloy.

[0053] The XRD analysis results of the oxygen-enriched residue in this example are shown in Figure 6 ,pass Figure 6 It can be seen that the main phases in the oxygen-rich residue are CaF2 and CaAl2O4, indicating that the oxygen impurities in the diamond wire sawing silicon waste are separated into the residue through the reduction smelting process.

[0054] The alloy ingot is cut and separated along the slag-gold interface to obtain Al-Si-Ca alloy and oxygen-rich residue; after detection and analysis, the main components of the Al-Si-Ca alloy in this embodiment are Al, Si and Ca, and their contents are respectively Al: 73.53wt.%, Si: 18.52wt.%, Ca: 7.95wt.%; the oxygen content is 0.0035wt.%. The purity of the mixture of AlF3 and MgF2 is 97.7wt.%, and its main components are respectively F: 38.21wt.%, Mg: 10.02wt.%, Al: 49.49wt.%; the main impurities and their contents are respectively Si: 0.40wt.%, Ca: 1.88wt.%.

[0055] Example 3

[0056] A method for preparing Al-Si-Ca alloy, AlF3 and MgF2 by cutting silicon waste and regenerating CaF2-MgO waste slag, the specific steps are as follows:

[0057] (1) Diamond wire cutting silicon waste (oxygen content of 4.7%) with a purity of 94.3% and CaF2-MgO waste slag (MgO content of 18 wt.%) were mixed evenly using a vibration mill, and metal Al particles (purity of 99.9%) were added to obtain a mixed material.

[0058] (2) The mixed material is placed in 4×10 4 Under the condition of slightly negative pressure of Pa (adjusted by inert atmosphere), electromagnetic induction heating is performed to a temperature of 1480°C to completely melt the alloy, and then constant temperature reduction smelting is performed for 2 hours to obtain a uniform Al-Si-Ca alloy melt, molten residue, and volatile products AlF3 and MgF2;

[0059] (3) After the volatile products AlF3 and MgF2 are condensed to 850°C, they are collected in a condenser. After the Al-Si-Ca alloy melt and the molten residue are cooled to room temperature, they are separated by mechanical cutting or wire cutting to obtain a low-oxygen Al-Si-Ca alloy ingot and a reduced residue.

[0060] After testing and analysis, the main components of the Al-Si-Ca alloy in this embodiment are Al, Si and Ca, and their contents are respectively Al: 73.94wt.%, Si: 19.21wt.%, Ca: 6.85wt.%; the oxygen content is 0.0031wt.%. The purity of the mixture of AlF3 and MgF2 is 99.3wt.%, and its main components are respectively F: 33.92wt.%, Mg: 19.48wt.%, Al: 45.93wt.%; the main impurities and their contents are respectively Si: 0.29wt.%, Ca: 0.38wt.%.

[0061] Example 4

[0062] A method for preparing Al-Si-Ca alloy, AlF3 and MgF2 by cutting silicon waste and regenerating CaF2-MgO waste slag, the specific steps are as follows:

[0063] (1) Diamond wire cutting silicon waste (oxygen content of 4.7%) with a purity of 94.3% and CaF2-MgO waste slag (MgO content of 24 wt.%) were mixed evenly using a vibration mill, and metal Al particles (purity of 99.9%) were added to obtain a mixed material.

[0064] (2) The mixed material is placed in 9×10 3 Under the condition of slightly negative pressure of Pa (inert atmosphere adjustment), electromagnetic induction heating to the temperature of 1490℃ is used to make it completely melted, and constant temperature reduction smelting is carried out for 2h to obtain a uniform Al-Si-Ca alloy melt, molten residue, and volatile products AlF3 and MgF2.

[0065] (3) After the volatile products AlF3 and MgF2 are condensed to 750°C, they are collected in a condenser. After the Al-Si-Ca alloy melt and the molten residue are cooled to room temperature, they are separated by mechanical cutting or wire cutting to obtain a low-oxygen Al-Si-Ca alloy ingot and a reduced residue.

[0066] After testing and analysis, the main components of the Al-Si-Ca alloy in this embodiment are Al, Si and Ca, and their contents are respectively Al: 74.42wt.%, Si: 20.25wt.%, Ca: 5.33wt.%; the oxygen content is 0.0022wt.%. The purity of the mixture of AlF3 and MgF2 is 99.4wt.%, and its main components are respectively F: 28.02wt.%, Mg: 23.64wt.%, Al: 47.79wt.%; the main impurities and their contents are respectively Si: 0.08wt.%, Ca: 0.47wt.%.

[0067] Example 5

[0068] A method for preparing Al-Si-Ca alloy, AlF3 and MgF2 by cutting silicon waste and regenerating CaF2-MgO waste slag, the specific steps are as follows:

[0069] (1) Diamond wire cutting silicon waste (oxygen content of 4.7%) with a purity of 94.3% and CaF2-MgO waste slag (MgO content of 30 wt.%) were mixed evenly using a vibration mill, and metal Al particles (purity of 99.9%) were added to obtain a mixed material.

[0070] (2) The mixed material is placed in 2×10 4 Under the condition of slightly negative pressure of Pa (inert atmosphere adjustment), electromagnetic induction heating to a temperature of 1500°C is used to completely melt it, and constant temperature reduction smelting is carried out for 2 hours to obtain a uniform Al-Si-Ca alloy melt, molten residue, and volatile products AlF3 and MgF2.

[0071] (3) After the volatile products AlF3 and MgF2 are condensed to 780°C, they are collected in a condenser. After the Al-Si-Ca alloy melt and the molten residue are cooled to room temperature, they are separated by mechanical cutting or wire cutting to obtain a low-oxygen Al-Si-Ca alloy ingot and a reduced residue.

[0072] After testing and analysis, the main components of the Al-Si-Ca alloy in this embodiment are Al, Si and Ca, and their contents are respectively Al: 74.35wt.%, Si: 20.39wt.%, Ca: 4.26wt.%; the oxygen content is 0.0020wt.%. The purity of the mixture of AlF3 and MgF2 is 96.7wt.%, and its main components are respectively F: 26.50wt.%, Mg: 34.96wt.%, Al: 35.32wt.%; the main impurities and their contents are respectively Si: 2.71wt.%, Ca: 0.51wt.%.

[0073] In summary, the present invention can fully utilize diamond wire cutting silicon waste and CaF2-MgO waste slag in a simple, efficient and clean way to obtain high-quality Al-Si-Ca alloy and AlF3, MgF2 products, truly achieving waste treatment with waste.

[0074] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing Al-Si-Ca alloy, AlF3 and MgF2 by cutting silicon waste and regenerating CaF2-MgO waste residue, characterized in that: The method comprises the following steps: (1) mixing diamond wire cutting silicon waste and CaF2-MgO waste slag uniformly and adding metal Al particles to obtain a mixed material; (2) placing the mixed material obtained in step (1) under a slightly negative pressure condition formed by adjusting an inert atmosphere, performing electromagnetic induction heating to melt the mixed material, and performing constant temperature reduction smelting to obtain a uniform Al-Si-Ca alloy melt, a molten residue, and volatile products AlF3 and MgF2; (3) The volatile products AlF3 and MgF2 are condensed and collected, and after the Al-Si-Ca alloy melt and the molten residue are cooled to room temperature, low-oxygen Al-Si-Ca alloy ingots and reduced residues are obtained after slag-gold separation.

2. The method according to claim 1, characterized in that: In the step (1), the mass of the silicon waste from diamond wire cutting accounts for 25-40% of the total mass of the mixed material, the mass of the CaF2-MgO waste slag added accounts for 15-30% of the total mass of the mixed material, and the mass of the metal Al particles added accounts for 45-50% of the total mass of the mixed material.

3. The method according to claim 2, characterized in that: In the CaF2-MgO waste slag, the content of MgO accounts for 12-30% of the total mass of the CaF2-MgO waste slag.

4. The method according to claim 1, characterized in that: In the step (2), the reduction smelting temperature is 1450-1500° C., and the reduction smelting time is 2 hours.

5. The method according to claim 1, characterized in that: In step (2), the inert atmosphere is adjusted to form a slight negative pressure in the range of 6.5×10 3 ~4×10 4 Pa.

6. The method according to claim 1, characterized in that: In the step (3), the volatile products AlF3 and MgF2 are collected when they are condensed to 700-850°C.

7. The method according to claim 1, characterized in that: In the step (3), the Al-Si-Ca alloy ingot and the reduction residue are separated by mechanical cutting or wire cutting.

8. The method according to any one of claims 1 to 7, characterized in that: The silicon waste cut by diamond wire contains SiO2 and Si at the same time, and SiO2 is wrapped on the surface of single substance Si.

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