Method for preparing titanium-containing Si-Fe alloys from recycled coal gangue and diamond cutting silicon waste

Abstract

This invention discloses a method for preparing titanium-containing Si-Fe alloys from recycled coal gangue and diamond cutting silicon waste, belonging to the field of resource recycling and alloy preparation technology. The invention includes: (1) crushing and grinding coal gangue to obtain coal gangue powder; (2) mixing the coal gangue powder with a slagging agent and then sintering it to obtain a mixed sintered material; (3) vacuum drying the diamond cutting silicon waste to obtain dry diamond cutting silicon waste; (4) mixing the mixed sintered material and the dry diamond cutting silicon waste in a specific ratio, and then heating and reducing the mixture under an inert atmosphere to obtain a titanium-containing Si-Fe alloy melt and slag; (5) separating the titanium-containing Si-Fe alloy melt and slag to obtain a titanium-containing Si-Fe alloy and reduction residue. This invention achieves the synergistic recycling of coal gangue and diamond cutting silicon waste, realizing the purpose of preparing high-value-added products from low-value solid waste.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling and alloy preparation technology, and relates to a method for preparing titanium-containing Si-Fe alloys by synergistically recycling coal gangue and diamond-cut silicon waste. Background Technology

[0002] Ferrosilicon alloys typically contain approximately 75 wt.% to 90 wt.% silicon. They are primarily used as deoxidizers and alloying additives in steel manufacturing processes, significantly reducing the oxygen content in steel and thus improving product performance. Furthermore, ferrosilicon alloys also have applications in non-ferrous metal industries, such as in the manufacture of silicon steel. Therefore, ferrosilicon alloys are very important in modern industrial production.

[0003] Coal gangue is a solid waste generated during coal production processes such as mining, tunneling, and coal washing. In my country, coal gangue accounts for approximately 10 to 15% of total coal mining output. Currently, the accumulated stockpile of coal gangue in my country exceeds 7 billion tons, covering an area of ​​approximately 150 square kilometers, and is increasing at a rate of about 200 million tons per year. Coal gangue stockpiles not only occupy significant land resources but may also generate dust, sulfur dioxide (SO2), and nitrogen oxides (NOx) due to spontaneous combustion. x Coal gangue produces 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 alleviate environmental pressure.

[0004] Diamond wire-cut silicon waste is generated during the diamond wire cutting process of 6N solar-grade silicon ingots (SoG-Si). According to production surveys, it is estimated that producing 1GW of silicon wafers generates approximately 1000 tons of diamond wire-cut silicon waste, with my country emitting nearly 350,000 tons annually. Because the particle size of diamond wire-cut silicon waste is smaller than PM2.5, it is considered a type of solid waste harmful to the environment and human health. On the other hand, diamond wire-cut silicon waste contains more than 85 wt.% elemental silicon and its price is only 25-30% of that of industrial silicon; therefore, it is considered a valuable raw material for producing high-purity silicon and an inexpensive silicon reducing agent.

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

[0006] Therefore, it is necessary to provide a method for the synergistic recycling of coal gangue and diamond cutting silicon waste to prepare titanium-containing Si-Fe alloys. This method utilizes coal gangue and diamond cutting silicon waste simultaneously in a green, environmentally friendly, and low-cost manner to achieve high-value utilization. By treating waste with waste, it reduces resource consumption, alleviates environmental pressure, and increases the economic value of resource recycling and regeneration. Summary of the Invention

[0007] To overcome the problems in the prior art, this invention uses oxide slag from coal gangue as a refining agent to remove oxygen impurities (SiO2) from silicon waste, extracting elemental silicon. The extracted elemental silicon can then be used as a reducing agent to reduce iron and titanium oxides in the coal gangue (reduction temperature approximately 1600℃, far below 2100℃), extracting iron and titanium to prepare titanium-containing Si-Fe alloys. This achieves the synergistic recycling of these two types of solid waste, realizing the goal of using low-value solid waste to produce high-value-added products. Furthermore, compared to carbothermal reduction, siliconothermal reduction reduces energy consumption and carbon emissions, making it more economical and environmentally friendly.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0009] The method includes the following steps:

[0010] (1) The coal gangue is crushed and ground to obtain coal gangue powder;

[0011] (2) The coal gangue powder obtained in step (1) and the slag-forming agent are mixed evenly and then sintered to obtain a mixed sintered material;

[0012] (3) Vacuum dry the silicon waste from diamond cutting to obtain dried silicon waste from diamond cutting;

[0013] (4) After mixing the mixed sintering material obtained in step (2) and the dry diamond cutting silicon waste obtained in step (3) in proportion, heat them under an inert atmosphere to carry out reduction smelting to obtain 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 reduction residue are obtained after slag-gold separation. During the reduction smelting process, the alloy melt and slag have been concentrated in different areas. After cooling into solids, the alloy melt and slag can be separated directly 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 coal gangue, the mass of CaO is 20% to 40% of the mass of coal gangue, and the mass of MgO is 15% to 25% of the mass of coal gangue.

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

[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 sintering material to the diamond-cut silicon waste is 4:1 to 2:1.

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

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

[0021] The beneficial effects of this invention are:

[0022] 1. High resource utilization rate: This invention uses two types of solid waste, coal gangue and silicon waste from diamond wire cutting, to prepare titanium-containing Si-Fe alloy, which reduces the accumulation of solid waste and environmental pollution, and improves the utilization rate of waste resources.

[0023] 2. High economic efficiency: This invention extracts and utilizes useful components (iron, titanium and silicon) from coal gangue and silicon waste to produce high-value-added titanium-containing Si-Fe alloys, thereby increasing the economic value of low-value solid waste and reducing the preparation cost of titanium-containing Si-Fe alloys.

[0024] 3. Environmentally friendly process: This invention uses silicon thermal reduction instead of the traditional carbothermal reduction process, which greatly reduces the reduction temperature (energy consumption) and carbon emissions, making it more economical and green.

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

[0026] 5. The reduction residue obtained by this invention can be recycled, further reducing resource consumption and helping to further reduce the preparation cost of titanium-containing Si-Fe alloys.

[0027] 6. By selecting a suitable slag-forming agent, the viscosity of the molten slag is reduced, and ultimately, under the density difference, slag-gold separation can be achieved more easily and effectively.

[0028] 7. The process of this invention is simple, easy to operate, and suitable for industrial application. Attached Figure Description

[0029] Figure 1 The image shows the macroscopic morphology of the titanium-containing Si-Fe alloy and the reduction residue obtained in Example 1 of this invention.

[0030] Figure 2 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 Implementation

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

[0033] Unless otherwise specified, all chemical reagents used in the embodiments of this invention are commercially available analytical grade reagents.

[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 titanium-containing Si-Fe alloys by recycling coal gangue and diamond cutting silicon waste, the specific steps of which are as follows:

[0037] (1) The coal gangue (Fe2O3 content is 10.4wt.% and TiO2 content is 2.2wt.%) was crushed and ground to obtain coal gangue powder with an average particle size of 200 mesh.

[0038] (2) After mixing the coal gangue powder and slag-forming agent in a mass ratio of coal gangue:CaO:Al2O3:MgO=1:0.4:0.05:0.15, the mixture is sintered at 1050℃ for 3 hours to obtain the mixed sintered material.

[0039] (3) The silicon waste from diamond cutting was dried at 120°C for 15 hours under a vacuum of 10Pa to remove moisture and obtain dried silicon waste from diamond wire cutting.

[0040] (4) The dried diamond wire-cut silicon waste and the mixed sintering material were mixed at a mass ratio of 2:1 (material:diamond wire-cut silicon waste) and mixed evenly. The mixture was then placed in an induction melting furnace and heated to 1550℃. Reduction melting was carried out in an argon atmosphere for 60 minutes to obtain a titanium-containing Si-Fe alloy and slag (reduction residue). Macroscopic morphology images of the cross-sections of the titanium-containing Si-Fe alloy and the reduction residue are shown below. Figure 1 As shown, the alloy and reduction residue were well separated.

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

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

[0043] Table 1

[0044]

[0045] Example 2:

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

[0047] (1) The coal gangue (Fe2O3 content is 10.4wt.% and TiO2 content is 2.2wt.%) was crushed and ground to obtain coal gangue powder with an average particle size of 300 mesh.

[0048] (2) After mixing the coal gangue powder and slag-forming agent in a mass ratio of coal gangue:CaO:Al2O3 = 1:0.2:0.15, the mixture is sintered at 1250℃ for 1.5h to obtain the mixed sintered material.

[0049] (3) The silicon waste from diamond cutting was dried at 80°C for 24 hours under a vacuum environment of 50Pa to remove moisture and obtain dried silicon waste from diamond wire cutting.

[0050] (4) The dried diamond wire-cut silicon waste and the mixed sintering material are mixed in a mass ratio of 4:1. The mixture is then placed in an induction melting furnace and heated to 1750°C. The mixture is then reduced and melted 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, titanium-containing Si-Fe alloy and reduction residue are obtained after slag-gold separation. The reduction residue can be returned to step (1) for recycling as a slag-forming agent.

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

[0053] Example 3:

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

[0055] (1) The coal gangue (Fe2O3 content is 10.4wt.% and TiO2 content is 2.2wt.%) was crushed and ground to obtain coal gangue powder with an average particle size of 200 mesh.

[0056] (2) After mixing the coal gangue powder and slag-forming agent in a mass ratio of coal gangue:CaO:MgO = 1:0.25:0.25, the mixture is sintered at 1150℃ for 2 hours to obtain the mixed sintered material.

[0057] (3) The silicon waste from diamond cutting was dried at 100°C for 20 hours under a vacuum of 30Pa to remove moisture and obtain dried silicon waste from diamond wire cutting.

[0058] (4) The dried diamond wire-cut silicon waste and the mixed sintering material are mixed in a mass ratio of 3:1. The mixture is then placed in an induction melting furnace and heated to 1650°C. The mixture is then reduced and melted 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, titanium-containing Si-Fe alloy and reduction residue are obtained after slag-gold separation. The reduction residue can be returned to step (1) for recycling as a slag-forming agent.

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

[0061] Example 4:

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

[0063] (1) The coal gangue (Fe2O3 content is 10.4wt.% and TiO2 content is 2.2wt.%) was crushed and ground to obtain coal gangue powder with an average particle size of 300 mesh.

[0064] (2) After mixing the coal gangue powder and slag-forming agent in a mass ratio of coal gangue:Al2O3:MgO=1:0.1:0.25, the mixture is sintered at 1200℃ for 2 hours to obtain the mixed sintered material.

[0065] (3) The silicon waste from diamond cutting was dried at 110°C for 18 hours under a vacuum of 20Pa to remove moisture and obtain dried silicon waste from diamond wire cutting.

[0066] (4) The dried diamond wire-cut silicon waste and the mixed sintering material are mixed in a mass ratio of 3:1. The mixture is then placed in an induction melting furnace and heated to 1600℃. The mixture is then reduced and melted 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, titanium-containing Si-Fe alloy and reduction residue are obtained after slag-gold separation. The reduction residue can be returned to step (1) for recycling as a slag-forming agent.

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

[0069] In summary, this invention effectively utilizes coal gangue and diamond cutting silicon waste through mixed smelting. The coal gangue removes oxygen impurities from the diamond cutting silicon waste, yielding elemental silicon. Simultaneously, the elemental silicon reduces iron and titanium oxides in the coal gangue, extracting iron and titanium, which then enter the alloy to prepare a high-purity titanium-containing Si-Fe alloy. This effectively achieves the synergistic recycling of two types of solid waste, realizing the goal of preparing high-value-added products from 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 and are not intended 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 to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method of producing a titanium-containing Si-Fe alloy from recycled coal gangue and diamond-cut silicon waste, characterized by: The method comprises the following steps: (1) crushing and grinding coal gangue to obtain coal gangue powder material; (2) mixing the coal gangue powder material obtained in step (1) and a slagging agent uniformly and then sintering to obtain a mixed sintering material; (3) vacuum drying diamond cutting silicon waste to obtain dried diamond cutting silicon waste; (4) mixing the mixed sintering material obtained in step (2) and the dried diamond cutting silicon waste obtained in step (3) uniformly according to a proportion, and then heating under an inert atmosphere to reduce smelting to obtain a titanium-containing Si-Fe alloy melt and a smelting slag; (5) after the titanium-containing Si-Fe alloy melt and the smelting slag obtained in step (4) are cooled to room temperature, a titanium-containing Si-Fe alloy and a reduction residue are obtained after slag-gold separation.

2. The method of claim 1, wherein: In step (2), the slagging 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 of claim 1, wherein: In step (2), the sintering temperature of the mixture of the coal gangue powder material and the slagging agent is 1050 to 1250°C, and the sintering time is 1.5 to 3 hours.

4. The method of claim 1, wherein: In step (3), the vacuum degree is 10 to 50 Pa, the drying temperature is 80 to 120°C, and the drying time is 15 to 24 hours.

5. The method of claim 1, wherein: In step (4), the mass ratio of the mixed sintering material and the diamond cutting silicon waste is mixed sintering material:diamond cutting silicon waste = 4:1 to 2:

1.

6. The method of claim 1 or 5, wherein: In step (4), the reduction smelting temperature is 1550 to 1750°C, and the reduction smelting time is 40 to 240 minutes.

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

Images