Method for preparing titanium-containing Si-Fe alloy by recycling coal gangue and diamond cutting silicon waste

Abstract

The invention discloses a method for preparing a titanium-containing Si-Fe alloy by recycling coal gangue and diamond cutting silicon waste, and belongs to the technical field of resource regeneration and alloy preparation. The method comprises the following steps: (1) crushing and grinding coal gangue to obtain a coal gangue powdery material; (2) uniformly mixing the coal gangue powdery material and a slag former, and sintering to obtain a mixed sintered material; (3) the diamond cutting silicon waste is subjected to vacuum drying, and dried diamond cutting silicon waste is obtained; (4) uniformly mixing the mixed sintering material and the dried diamond cutting silicon waste according to a ratio, and heating under an inert atmosphere condition for reduction smelting to obtain a titanium-containing Si-Fe alloy melt and slag; and (5) the titanium-containing Si-Fe alloy melt and the slag are subjected to slag-gold separation, and then the titanium-containing Si-Fe alloy and reduction residues are obtained. According to the method, the coal gangue and the diamond cutting silicon waste are synergistically recycled, so that the two solid wastes are synergistically recycled, and the purpose of preparing a high-added-value product by utilizing the low-value solid wastes is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of resource regeneration and alloy preparation, and relates to a method for preparing a titanium-containing Si-Fe alloy by synergistically recovering coal gangue and diamond-cut silicon waste. Background Art

[0002] Ferrosilicon alloys usually contain about 75wt.% to 90wt.% silicon. They are mainly used as deoxidizers and alloy additives in the steel manufacturing process, which can significantly reduce the oxygen content in steel and improve the performance of the product. In addition, ferrosilicon alloys are also used in non-ferrous metal industries, such as the manufacture of silicon steel. Therefore, ferrosilicon alloys are very important in modern industrial production.

[0003] Gangue is solid waste generated during the coal production process such as mining, tunneling and coal washing. The amount of gangue produced in my country accounts for about 10wt.% to 15wt.% of the total coal mining volume. At present, the cumulative stockpile of gangue in my country exceeds 7 billion tons, covering an area of ​​about 150 square kilometers, and is increasing at a rate of about 200 million tons per year. The stacking of gangue not only occupies a large amount of land resources, but also may produce dust, sulfur dioxide (SO2), nitrogen oxides (NO x ), carbon monoxide (CO) and other oxides, polluting the air. Therefore, promoting the comprehensive utilization of coal gangue can not only enhance its economic value, but also help reduce land occupation and ease environmental pressure.

[0004] Diamond wire cutting silicon waste is generated in the process of diamond wire cutting 6N solar grade silicon ingots (SoG-Si). According to production surveys and estimates, the production of 1GW silicon wafers will generate about 1,000 tons of diamond wire cutting silicon waste, and my country discharges nearly 350,000 tons of diamond wire cutting silicon waste each year. Since the particle size of diamond wire cutting silicon waste is smaller than PM2.5, it is regarded as a solid waste that is harmful to the environment and human health. On the other hand, diamond wire cutting silicon waste contains more than 85wt.% of elemental Si, and the price is only 25-30% of industrial silicon. Therefore, it is considered a valuable raw material for the production of high-purity silicon and a cheap silicon reducing agent.

[0005] At present, extracting and utilizing the rich aluminum, silicon and iron in coal gangue to prepare aluminum-silicon-iron alloy is one of the important directions for its high-value utilization. However, most of the current coal gangue utilization processes use C as a reducing agent, which not only leads to high reduction temperatures (above 2100℃), causing increased energy consumption and costs, but also produces CO2 waste gas, polluting the environment.

[0006] Therefore, it is necessary to provide a method for synergistically recycling coal gangue and diamond-cut silicon waste to prepare titanium-containing Si-Fe alloy, and to simultaneously utilize coal gangue and diamond-cut silicon waste in a high-value manner through a green, environmentally friendly, and low-cost process. By treating waste with waste, resource consumption can be reduced, environmental pressure can be alleviated, and the economic value of resource recycling and regeneration can be improved. Summary of the invention

[0007] In order to overcome the problems in the background technology, the present invention uses the oxide slag in the coal gangue as a refining agent to remove oxygen impurities (SiO2) in the silicon waste and extract the elemental silicon therein; the extracted elemental silicon can be used as a reducing agent to reduce the oxides of iron and titanium in the coal gangue (the reduction temperature is about 1600°C, which is much lower than 2100°C), extract iron and titanium, and prepare titanium-containing Si-Fe alloy, thereby realizing the coordinated recycling of these two solid wastes and achieving the purpose of preparing high value-added products from low-value solid wastes. In addition, compared with carbon thermal reduction, silicon thermal reduction reduces energy consumption and carbon gas emissions, and is more economical and environmentally friendly.

[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) crushing and grinding the coal gangue to obtain coal gangue powder material;

[0011] (2) uniformly mixing the gangue powder material obtained in step (1) and a slag-forming agent and then sintering the mixture to obtain a mixed sintered material;

[0012] (3) vacuum drying the diamond-cut silicon waste to obtain dry diamond-cut silicon waste;

[0013] (4) mixing the mixed sintered material obtained in step (2) and the dried diamond-cut silicon waste obtained in step (3) in a uniform proportion, heating and reducing smelting under an inert atmosphere to obtain a titanium-containing Si-Fe alloy melt and slag;

[0014] (5) After the titanium-containing Si-Fe alloy melt and slag obtained in step (4) are cooled to room temperature, the titanium-containing Si-Fe alloy and the reduction residue are obtained after slag-gold separation. During the reduction smelting process, the alloy melt and the slag have been concentrated in different areas. After cooling to a solid, the alloy melt and the slag can be directly separated by mechanical cutting or wire cutting.

[0015] Preferably, in step (2), the slag-forming agent is at least two of Al2O3, CaO and MgO, wherein the mass of Al2O3 is 5% to 15% of the mass of the coal gangue, the mass of CaO is 20% to 40% of the mass of the coal gangue, and the mass of MgO is 15% to 25% of the mass of the coal gangue.

[0016] Preferably, in step (2), the sintering temperature of the mixture of the coal gangue powder material and the slag-forming agent is 1050-1250° C., and the sintering time is 1.5-3 h.

[0017] Preferably, in step (3), the vacuum degree is 10-50 Pa, the drying temperature is 80-120° C., and the drying time is 15-24 h.

[0018] Preferably, in step (4), the mass ratio of the mixed sintered material to the diamond-cut silicon waste is mixed sintered material: diamond-cut silicon waste = 4:1 to 2:1.

[0019] Preferably, in step (4), the reduction smelting temperature is 1550-1750° C., and the reduction smelting time is 40-240 min.

[0020] Preferably, in step (5), the reduction residue is returned to step (1) for recycling as a slag-forming agent.

[0021] Beneficial effects of the present invention:

[0022] 1. High resource utilization rate: The present invention synergistically recycles two solid wastes, coal gangue and diamond wire cutting silicon waste, to prepare titanium-containing Si-Fe alloy, thereby reducing the accumulation of solid waste and environmental pollution and improving the utilization rate of waste resources.

[0023] 2. High economic efficiency: The present invention produces high value-added titanium-containing Si-Fe alloy by extracting and utilizing useful components (iron, titanium and silicon) in coal gangue and silicon waste, thereby increasing the economic value of low-value solid waste and reducing the preparation cost of titanium-containing Si-Fe alloy.

[0024] 3. Environmentally friendly process: The present invention adopts silicon thermal reduction to replace the traditional carbon thermal reduction process, which greatly reduces the reduction temperature (energy consumption) and carbon gas emissions, making it more economical and green.

[0025] 4. The titanium-containing Si-Fe alloy prepared by the present invention has high purity and good quality, which can lay a good foundation for subsequent utilization.

[0026] 5. The reduction residue obtained by the present invention can be recycled, which further reduces resource consumption and is conducive to further reducing the preparation cost of titanium-containing Si-Fe alloy.

[0027] 6. The present invention reduces the viscosity of the slag by selecting a suitable slag-forming agent, and finally, under the density difference, the slag-metal separation can be achieved relatively easily and better.

[0028] 7. The process of the present invention is simple, easy to operate, and suitable for industrial promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a macroscopic morphology of the titanium-containing Si-Fe alloy and the reduction residue separated from each other prepared in Example 1 of the present invention;

[0030] Figure 2 This is the XRD analysis diagram of coal gangue;

[0031] Figure 3 This is the XRD analysis diagram of the reduction 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] The XRD analysis results of coal gangue are as follows: Figure 2 As shown, through Figure 2 It can be seen that the iron-rich phase it contains is Fe3FeSiO4(OH)5.

[0035] Example 1

[0036] A method for preparing a titanium-containing Si-Fe alloy by recycling coal gangue and diamond-cut silicon waste, the specific steps are as follows:

[0037] (1) Coal gangue (Fe2O3 content of 10.4wt.%, TiO2 content of 2.2wt.%) was crushed and ground to obtain a coal gangue powder material with an average particle size of 200 meshes.

[0038] (2) The coal gangue powder material and the slag-making agent are uniformly mixed in a mass ratio of coal gangue: CaO: Al2O3: MgO = 1:0.4:0.05:0.15, and sintered at 1050°C for 3 hours to obtain a mixed sintered material.

[0039] (3) The diamond-cut silicon waste is vacuum dried at 120° C. for 15 hours under a vacuum environment of 10 Pa to remove moisture and obtain dry diamond wire-cut silicon waste.

[0040] (4) Mix the dried diamond wire-cut silicon waste and the mixed sintered material in a mass ratio of sintered material: diamond wire-cut silicon waste = 2:1 and mix them evenly. Then, place them in an induction melting furnace and heat them to 1550°C. Perform reduction melting in an argon atmosphere for 60 minutes to obtain a titanium-containing Si-Fe alloy and slag (reduction residue). The macroscopic morphology of the cross section of the titanium-containing Si-Fe alloy and the reduction residue is shown in FIG. Figure 1 As shown, the alloy and the reduction residue were well separated.

[0041] (5) After the reduction smelting is completed, a titanium-containing Si-Fe alloy and a reduction residue are obtained after slag-gold separation. The reduction residue can be returned to step (1) as a slag-forming agent for recycling.

[0042] The composition of the titanium-containing Si-Fe alloy is shown in Table 1, and its main components are 90.6wt.% Si, 6.93wt.% Fe (iron extraction rate is 97.3%), 1.4wt.% Ti, 0.5wt.% Ca, 0.2wt.% Al and 0.1wt.% Mg; the XRF analysis results of the reduced residue show that the Fe2O3 content in the residue is 0.37wt.%, and the TiO2 content is 0.14wt.%, indicating that most of the Fe and Ti in the coal gangue are extracted into the alloy; the nitrogen and oxygen analysis shows that the oxygen content in the alloy is 0.12wt.%, which indicates that the oxygen impurities in the diamond wire cutting silicon waste are well removed by the coal gangue slag agent.

[0043] Table 1

[0044]

[0045] Embodiment 2:

[0046] A method for preparing a titanium-containing Si-Fe alloy by recycling coal gangue and diamond-cut silicon waste, the specific steps are as follows:

[0047] (1) Coal gangue (Fe2O3 content of 10.4wt.%, TiO2 content of 2.2wt.%) was crushed and ground to obtain a coal gangue powder material with an average particle size of 300 meshes.

[0048] (2) The gangue powder material and the slag-making agent are uniformly mixed in a mass ratio of gangue:CaO:Al2O3=1:0.2:0.15, and sintered at 1250°C for 1.5 hours to obtain a mixed sintered material.

[0049] (3) The diamond-cut silicon waste is vacuum dried at 80° C. for 24 hours under a 50 Pa vacuum environment to remove moisture and obtain dry diamond wire-cut silicon waste.

[0050] (4) Mix the dried silicon waste from diamond wire cutting and the mixed sintering material in a mass ratio of sintering material: diamond wire cutting silicon waste = 4:1, mix them evenly, then place them in an induction melting furnace and heat them to 1750° C., and perform reduction melting in an argon atmosphere for 40 minutes to obtain a titanium-containing Si—Fe alloy and slag.

[0051] (5) After the reduction smelting is completed, a titanium-containing Si-Fe alloy and a reduction residue are obtained after slag-gold separation. The reduction residue can be returned to step (1) as a slag-forming agent for recycling.

[0052] The composition of the titanium-containing Si-Fe alloy of this embodiment is shown in Table 1. Its main components are 76.8wt.% Si, 18.4wt.% Fe (iron extraction rate is 95.9%), 3.6wt.% Ti, 0.7wt.% Ca and 0.4wt.% Al. The XRD analysis results of the reduced residue are shown in Table 1. Figure 3 As shown, through Figure 3 It can be seen that in this embodiment, the main phase of the reduced residue is CaAl2Si2O8, and no iron-containing phase is detected; the XRF analysis results of the reduced residue show that the Fe2O3 content in the residue is 0.25wt.%, and the TiO2 content is 0.07wt.%, indicating that the Fe and Ti oxides in the gangue are efficiently extracted through silicon reduction smelting; nitrogen and oxygen analysis show that the oxygen content in the alloy is 0.05wt.%, indicating that the oxygen impurities in the diamond wire cutting silicon waste are well removed by the gangue slag agent.

[0053] Embodiment 3:

[0054] A method for preparing a titanium-containing Si-Fe alloy by recycling coal gangue and diamond-cut silicon waste, the specific steps are as follows:

[0055] (1) Coal gangue (Fe2O3 content of 10.4wt.%, TiO2 content of 2.2wt.%) was crushed and ground to obtain a coal gangue powder material with an average particle size of 200 meshes.

[0056] (2) The gangue powder material and the slag-making agent are uniformly mixed in a mass ratio of gangue:CaO:MgO=1:0.25:0.25, and sintered at 1150°C for 2 hours to obtain a mixed sintered material.

[0057] (3) The diamond-cut silicon waste is vacuum dried at 100° C. for 20 hours under a vacuum environment of 30 Pa to remove moisture and obtain dry diamond-wire-cut silicon waste.

[0058] (4) The dried diamond wire-cut silicon waste and the mixed sintering material are mixed and evenly mixed in a mass ratio of sintering material: diamond wire-cut silicon waste = 3:1, and then placed in an induction melting furnace and heated to 1650° C., and reduction smelting is performed in an argon atmosphere for 240 minutes to obtain a titanium-containing Si—Fe alloy and slag.

[0059] (5) After the reduction smelting is completed, a titanium-containing Si-Fe alloy and a reduction residue are obtained after slag-gold separation. The reduction residue can be returned to step (1) as a slag-forming agent for recycling.

[0060] In this embodiment, the composition of the titanium-containing Si-Fe alloy is shown in Table 1, and its main components are 81.2wt.% Si, 13.3wt.% Fe (iron extraction rate is 96.4wt.%), 2.3wt.% Ti, 0.6wt.% Ca and 0.4wt.% Mg; the XRF analysis results of the reduced residue show that the Fe2O3 content in the residue is 0.38wt.%, and the TiO2 content is 0.11wt.%, indicating that most of the Fe and Ti in the coal gangue have been extracted into the alloy; nitrogen and oxygen analysis shows that the oxygen content in the alloy is 0.09wt.%, which indicates that the oxygen impurities in the diamond wire cutting silicon waste are well removed by the coal gangue slag agent.

[0061] Embodiment 4:

[0062] A method for preparing a titanium-containing Si-Fe alloy by recycling coal gangue and diamond-cut silicon waste, the specific steps are as follows:

[0063] (1) Coal gangue (Fe2O3 content of 10.4wt.%, TiO2 content of 2.2wt.%) was crushed and ground to obtain a coal gangue powder material with an average particle size of 300 meshes.

[0064] (2) The coal gangue powder material and the slag-making agent are uniformly mixed in a mass ratio of coal gangue: Al2O3:MgO=1:0.1:0.25, and sintered at 1200°C for 2h to obtain a mixed sintered material.

[0065] (3) The diamond-cut silicon waste is vacuum dried at 110° C. for 18 hours under a vacuum environment of 20 Pa to remove moisture and obtain dry diamond wire-cut silicon waste.

[0066] (4) Dry diamond wire-cut silicon waste and mixed sintering material are mixed and evenly mixed in a mass ratio of sintering material: diamond wire-cut silicon waste = 3:1, and then placed in an induction melting furnace and heated to 1600° C., and reduction smelting is performed in an argon atmosphere for 50 minutes to obtain a titanium-containing Si-Fe alloy and slag.

[0067] (5) After the reduction smelting is completed, a titanium-containing Si-Fe alloy and a reduction residue are obtained after slag-gold separation. The reduction residue can be returned to step (1) as a slag-forming agent for recycling.

[0068] In this embodiment, the composition of the titanium-containing Si-Fe alloy is shown in Table 1, and its main components are 80.5wt.% Si, 13.7wt.% Fe (iron extraction rate is 96.1wt.%), 2.2wt.% Ti, 0.9wt.% Ca and 0.3wt.% Al; the XRF analysis results of the reduced residue show that the Fe2O3 content in the residue is 0.42wt.%, and the TiO2 content is 0.13wt.%, indicating that most of the Fe and Ti oxides in the coal gangue have been reduced into the alloy; nitrogen and oxygen analysis shows that the oxygen content in the alloy is 0.11wt.%, which indicates that the oxygen impurities in the diamond wire cutting silicon waste are well removed by the coal gangue slag agent.

[0069] In summary, the present invention achieves the goal of preparing a titanium-containing Si-Fe alloy with high purity by mixing and smelting coal gangue and diamond-cut silicon waste, effectively utilizing coal gangue to remove oxygen impurities in diamond-cut silicon waste, and simultaneously utilizing elemental silicon to reduce iron and titanium oxides in the coal gangue, extracting iron and titanium, and allowing iron and titanium to enter the alloy, thereby effectively realizing the coordinated recycling of the two solid wastes and achieving the purpose of preparing high value-added products using low-value solid waste.

[0070] 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 a titanium-containing Si-Fe alloy by recycling coal gangue and diamond-cut silicon waste, characterized in that: The method comprises the following steps: (1) crushing and grinding the coal gangue to obtain coal gangue powder material; (2) uniformly mixing the gangue powder material obtained in step (1) and a slag-forming agent and then sintering the mixture to obtain a mixed sintered material; (3) vacuum drying the diamond-cut silicon waste to obtain dry diamond-cut silicon waste; (4) mixing the mixed sintered material obtained in step (2) and the dried diamond-cut silicon waste obtained in step (3) in a uniform proportion, heating and reducing smelting under an inert atmosphere to obtain a titanium-containing Si-Fe alloy melt and slag; (5) After the titanium-containing Si-Fe alloy melt and slag obtained in step (4) are cooled to room temperature, the titanium-containing Si-Fe alloy and a reduced residue are obtained after slag-gold separation.

2. The method according to claim 1, characterized in that: In the step (2), the slag-forming agent is at least two of Al2O3, CaO and MgO, wherein the mass of Al2O3 is 5% to 15% of the mass of the coal gangue, the mass of CaO is 20% to 40% of the mass of the coal gangue, and the mass of MgO is 15% to 25% of the mass of the coal gangue.

3. The method according to claim 1, characterized in that: In the step (2), the sintering temperature of the mixture of the coal gangue powder material and the slag-forming agent is 1050-1250° C., and the sintering time is 1.5-3 hours.

4. The method according to claim 1, characterized in that: In the step (3), the vacuum degree is 10-50 Pa, the drying temperature is 80-120° C., and the drying time is 15-24 h.

5. The method according to claim 1, characterized in that: In the step (4), the mass ratio of the mixed sintered material to the diamond-cut silicon waste is mixed sintered material: diamond-cut silicon waste = 4:1 to 2:

1.

6. The method according to claim 1 or 5, characterized in that: In the step (4), the reduction smelting temperature is 1550-1750° C., and the reduction smelting time is 40-240 min.

7. The method according to any one of claims 1, 2, 3, 4, and 5, characterized in that: In the step (5), the reduction residue is returned to the step (1) for recycling as a slag-forming agent.

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