A method for synergistic enrichment of rare metals in rare metal waste using silicon and a low-frequency electric arc furnace

Abstract

This invention belongs to the technical field of secondary resource recycling and reuse of rare and precious metals, rare and dispersed metals, and rare earth metals, and relates to a method for co-enriching rare and precious metals in waste materials using silicon and a low-frequency electric arc furnace. The method utilizes a low-frequency electric arc furnace as the smelting equipment. The waste material containing rare and precious metals to be treated and a slag-forming agent are mixed in a certain proportion, formed into pellets, dried, and then added to the low-frequency electric arc furnace for melting to obtain pre-melted slag. Industrial silicon or waste silicon materials are crushed, pelletized, dried, and then added to the low-frequency electric arc furnace for high-temperature melting and collection to improve the reaction efficiency between materials. After a period of reaction, silicon slag is separated to obtain molten silicon and smelting slag. After removing the smelting slag, pre-melted slag is added for continued melting and heat preservation. After multiple melting and enrichment processes, molten silicon enriched with rare and precious metals is obtained. The molten silicon is poured out and cooled to obtain silicon ingots enriched with rare and precious metals. The silicon ingots are crushed, ground, and the rare and precious metals are separated and purified. The silicon material can be reused as a silicon source or used as a raw material for producing solar-grade silicon. The present invention has a simple process and low energy consumption cost, which is conducive to industrial application.

Description

Technical Field

[0001] This invention belongs to the technical field of secondary resource recycling and reuse of rare metals such as rare precious metals, rare dispersed metals, and rare earth metals, and relates to a method for the synergistic recovery and enrichment of rare metals in waste materials using silicon and a low-frequency electric arc furnace. Background Technology

[0002] The three rare metals mainly refer to rare earth metals (scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium), rare precious metals (gold, silver, zirconium, niobium, platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, platinum)), and rare dispersed metals (gallium, germanium, selenium, indium, tellurium, rhenium, thallium, rubidium, hafnium, scandium, vanadium), etc.

[0003] Solid waste resources containing rare metals mainly include deactivated automotive exhaust catalysts, deactivated chemical industry catalysts, anode mud, rare earth waste from neodymium iron boron magnets, electronic product recycling waste, aerospace recycling waste, and other slag containing rare metals.

[0004] Currently, the main processes for recovering rare metals from solid waste containing rare metals are hydrometallurgy and pyrometallurgy. Hydrometallurgical recovery, with its advantages of low cost, simple equipment, and easy operation, is more suitable for small-scale production. However, its drawbacks, such as generating large amounts of difficult-to-treat waste liquid and long processing cycles, make it unsuitable for processing large quantities of rare metal-containing solid waste. Pyrometallurgical recovery, with its advantages of high recovery rate, large single-processing capacity, and short processing time, has become the mainstream recovery method and is currently a research hotspot. The main factors restricting the development of pyrometallurgical recovery are energy consumption and cost control. Currently, domestic and international intellectual property rights related to pyrometallurgical capture and recovery of rare metals mainly focus on iron, copper, and matte capture and recovery methods, which have a high degree of maturity in the industrial field.

[0005] CN 107400784 A discloses a method for recovering platinum group metals from spent catalysts using an iron trapping agent. The method includes the following steps: mixing iron oxide with spent catalyst, reducing agent, and slagging agent in a certain proportion to obtain a mixture; placing the mixture in a melting furnace at 1200–1300℃ for melting; after complete reaction, allowing it to stand to allow the alloy melt to fully trap the platinum group metals and sink to the bottom; and performing slag-metal separation to obtain a multi-metallic alloy phase rich in platinum group metals and smelting slag. This method has advantages such as high recovery rate and fast melting speed, but it has high energy consumption, high equipment consumables, and high maintenance costs. CN 113737013 A discloses a method for recovering platinum group metals (PGMs) from spent catalysts using copper and antimony as a scavenging agent. The method includes the following steps: preparing a PGM scavenging agent by mixing copper and antimony in a specific ratio; mixing spent catalyst, slag-forming flux, scavenging agent, and reducing agent in a predetermined ratio to obtain a mixture; smelting the mixture at 1000–1200°C; after the reaction, slag floats on the surface of the alloy phase; separating the slag phase from the alloy phase yields a copper-antimony alloy phase containing PGMs; recovering the obtained copper-antimony alloy phase containing PGMs, and subjecting it to acid hydrolysis, separation, and purification treatment to obtain the PGMs. This method features a low smelting temperature and allows for the repeated recycling of the copper-antimony alloy. CN 112981101 A discloses a clean and efficient method for capturing and enriching platinum group metals in catalysts. This method includes the following steps: reducing and smelting silicon waste, spent catalyst containing rare and precious metals, slagging agent, and additives together; after smelting, separating the slag and metal to obtain a silicon-based alloy containing rare and precious metals and waste residue; grinding the obtained silicon-based alloy, washing with aqua regia, and filtering to obtain silicon powder and a leachate containing rare and precious metals; washing the obtained silicon powder with a fluorinated acid solution and filtering to obtain high-purity silicon and a filtrate containing precious metals. However, this method is currently only at the laboratory stage and has not yet been promoted to industrial applications.

[0006] Regardless of whether it's the iron trapping method, copper trapping method, or nickel matte trapping method, the primary focus is on recovering platinum group metals (platinum, palladium, rhodium), while rare earth metals (cerium, lanthanum, praseodymium, etc.) and rare metals (zirconium, niobium, etc.) cannot be recovered. Due to its excellent properties, silicon can act as both a reducing agent and a trapping agent during the smelting process to enrich the rare metals. The trapped rare metals are then concentrated at the silicon grain boundaries.

[0007] Therefore, it is evident that providing a low-frequency electric arc furnace as a smelting device for smelting, enriching, and recovering rare metals from waste containing rare metals, and promoting its application in practical industrialization, overcoming the difficulty of melting waste silicon, controlling slag system design, adjusting density and viscosity to ensure complete separation of silicon slag after smelting, achieving simultaneous recovery of multiple rare metals, simplifying the production process, reducing production costs, reducing energy consumption, and improving production efficiency, has become an urgent problem that technical personnel in this field need to solve. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a method for the synergistic recovery and enrichment of rare metals from rare metal waste using silicon and a low-frequency electric arc furnace. This method overcomes the difficulties in recovering rare metal waste and treating waste silicon by controlling the slag system design and adjusting density and viscosity to ensure complete separation of silicon and slag after smelting. This achieves simultaneous recovery of multiple rare metals, simplifies the production process, reduces production costs, decreases energy consumption, and improves production efficiency. The present invention is achieved through the following technical solutions.

[0009] A method for synergistically recovering and enriching rare metals from rare metal waste using silicon and a low-frequency electric arc furnace, characterized by comprising the following steps:

[0010] Step (1): The recycled waste containing rare metals is crushed, graded, dried and mixed with slagging agent to form pellets and then dried; the recycled silicon waste is used as a silicon source, and is physically crushed, graded and then pelletized and dried for later use.

[0011] Step (2): Place the pellets containing three rare metals obtained in step (1) into a low-frequency electric arc furnace for a period of time to pre-melt them and obtain a pre-melted slag pool.

[0012] Step (3): The silicon material blocks obtained in step (1) are added to the pre-melted slag pool obtained in step (2) in a certain proportion for high-temperature smelting to improve the reaction efficiency between materials in the low-frequency electric arc furnace. After a period of smelting and recovery, molten silicon and molten slag are obtained. Then, silicon slag separation and remelting are carried out. The silicon slag separation and remelting process route is mainly divided into the following two types:

[0013] Route 1: For the high-density slag agent obtained in step (1), after melting, the molten silicon floats on top of the slag and is discharged first as new silicon material for later use. The slag is then discharged and solidified to form glass slag for further processing. Steps (2) and (3) are repeated, and the new silicon material obtained is added to the low-frequency electric arc furnace as a silicon source for melting until the silicon capacity limit is reached.

[0014] Route 2: For the low-density slag agent obtained in step (1), after smelting, the slag floats on the silicon melt. After removing the slag, the molten silicon is retained in the electric arc furnace. The slag agglomerate obtained in step (1) is added according to the ratio and smelted in the low-frequency electric arc furnace until the silicon capacity limit is reached.

[0015] Step (4): After crushing and grinding the silicon ingot obtained in step (3), wet separation and purification are carried out to obtain rare metal enrichment and pure silicon material. The rare metal enrichment can be further leached and purified, and the pure silicon material can be reused as a silicon source or used as a raw material for producing solar-grade silicon.

[0016] The rare metal waste used as raw material in step (1) includes one or more of the following: rare earth metal waste, rare metal waste, and rare dispersed metal waste.

[0017] The rare metal-containing waste recovered in step (1) includes scrapped automobile exhaust three-way catalysts, depleted petrochemical catalysts, industrial catalysts containing rare and precious metals, anode mud, electronic product recycling waste, aerospace recycling waste, and other slag containing rare metals.

[0018] In step (1), due to the different compositions of the three rare metal wastes, two types of slag system designs are required in the slag system design: high-density slag system with a density higher than 2.5 g / cm³. 3 Melting point below 1400℃; low-density slag system, density below 2.0 g / cm³ 3 Slag-forming agents include one or more of the following: Al2O3, SiO2, CaO, MgO, CaF2, NaF, BaO, FeO, BaF2, MnO, and CaCl2. The amount added depends on the specific requirements for slag formation.

[0019] In step (1), the waste material is crushed, graded, dried, and mixed with a slag-forming agent to form pellets, which are then dried to a size of 5-10 cm and a moisture content of less than 5%.

[0020] The silicon waste recovered in step (1) includes industrial silicon tailings, solar-grade polycrystalline silicon waste, battery diffusion wafer cutting waste, diamond wire silicon wafer cutting waste, and other silicon waste.

[0021] In step (1), the recycled silicon waste is used as a silicon source. After physical crushing and grading, it is formed into pellets and dried, with a size of 5-10 cm and a moisture content of less than 5%.

[0022] The pre-melting temperature in step (2) is 1573K to 1673K; the equipment is a low-frequency electric arc furnace with a working frequency of 1 to 45Hz; the cooling method is air cooling with a cooling rate of 0.1 to 25K.

[0023] The smelting process described in step (3) involves adding silicon pellets in small quantities to pre-melted slag for smelting and enrichment. The mass ratio between silicon pellets and slag is 0.1:1 to 2:1. The smelting temperature range is 1723K to 1973K. The holding time is not less than 1 hour. The cooling method is air cooling, and the cooling rate is 0.1 to 15℃.

[0024] In step (4), the method for separating and purifying the three rare metals is wet leaching. The leaching agent is a mixture of one or more of hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid in any proportion. The acid concentration is 0.1 to 100 wt.%, the mass ratio of silicon to acid is 1:0.1 to 1:1200, the pickling temperature is 15 to 100°C, and the pickling time is 0.5 to 24 h.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) This invention can not only recover the rare metals in the failed automotive catalyst, but also recover and process the failed petrochemical catalyst, industrial catalyst containing rare and precious metals, anode mud, rare earth waste from neodymium iron boron magnets, waste from electronic product recycling, waste from aerospace recycling, and other slag containing rare metals. It overcomes the difficulties in recovering rare metal waste and treating waste silicon, and controls the slag system design, adjusting density, viscosity, etc. to ensure complete separation of silicon slag after smelting.

[0027] (2) This invention enables the recovery of multiple rare metal elements, realizes continuous production of rare metal pyrometallurgical recovery of rare metals in waste containing rare metals, simplifies the production process, reduces production costs, and improves production efficiency.

[0028] (2) The present invention uses a low-frequency electric arc furnace as the smelting equipment. The working frequency is low, the electric arc is stable and concentrated, the smelting pool is well stirred, and the reaction in the furnace is good. This can greatly improve the efficiency of the rare metals recovery reaction and reduce energy consumption. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] Example 1

[0032] like Figure 1 As shown, a method for the synergistic recovery and enrichment of rare metals from rare metal waste using silicon and a low-frequency electric arc furnace includes the following process steps:

[0033] Step 1: The depleted automotive three-way catalytic converter (cordierite support, with SiO2 content of 47.02wt%, Al2O3 content of 37.94wt%, MgO content of 9.20wt%, CeO2 content of 1.12wt%, ZrO2 content of 1.01wt%, Pt content of 974ppmw, and Rh content of 208ppmw), and slagging agent (SiO2 / Al2O3 mass ratio of 3:2, with MgO accounting for 10% of the total mass of the slag system, and the total mass of the slagging agent accounting for 70% of the mass of the depleted automotive catalyst) are crushed, graded, and agglomerated to a size of 8cm. They are then dried at 373K for 12 hours, with a moisture content not exceeding 5%. The density of this high-density slag system is 2.607g / cm³. 3 .

[0034] Step 2: Use silicon ingot cutting waste (Si content is 70.47wt%) as silicon source, crush, grade and form into 8cm agglomerates, and dry at 373K for 12 hours.

[0035] Step 3: Place the high-density slag pellets in a low-frequency electric arc furnace for pre-melting. The low-frequency electric arc furnace operates at a frequency of 25 Hz, the pre-melting temperature is 1673 K, the melting time is 1 hour, and the cooling method is air cooling. Finally, the pellets are placed in a pre-melted slag pool.

[0036] Step 4: Add the silicon agglomerate obtained in Step 2 into an electric arc furnace for melting at a silicon-to-slag ratio of 0.5:1. The melting temperature is 1723K, and the melting time is 5 hours. After melting and collection, the silicon floats on the slag. The molten silicon is discharged from the top in a molten state and is reserved as new silicon material for further melting and collection. The slag is then discharged and solidified to form glass slag.

[0037] Step 5: After removing the slag, add the same mass of the mixture from Step 1 back into the low-frequency electric arc furnace. Repeat steps 3 and 4. After five melting cycles, the three rare metals reach their capacity limit in the silicon melt. After cooling, the silicon melt yields a rare metal enrichment. The direct recovery rates of the three rare metal elements are Pt 97.23%, Pd 96.36%, Rh 95.89%, Zr 86.39%, and Ce 93.35%.

[0038] Step 6: The enriched rare metal silicon ingots obtained in Step 5 are crushed, classified, and ground to less than 100 micrometers. They are then acid-washed with aqua regia (HCl (analytical grade) and HNO (analytical grade) in a volume ratio of 3:1, with a solid-liquid ratio of 1:8 g / ml, an acid-washing temperature of 353K, and an acid-washing time of 3h. After filtration, silicon powder and a leachate containing rare metal elements are obtained.

[0039] Example 2

[0040] like Figure 1 As shown, a method for the synergistic recovery and enrichment of rare metals from rare metal waste using silicon and a low-frequency electric arc furnace includes the following process steps:

[0041] Step 1: The depleted automotive three-way catalytic converter (cordierite support, with SiO2 content of 32.25wt%, Al2O3 content of 21.36wt%, MgO content of 13.12wt%, CeO2 content of 2.65wt%, ZrO2 content of 1.38wt%, Pt content of 1352ppmw, and Rh content of 532ppmw), and slagging agent (SiO2 / Al2O3 mass ratio of 4:1, with MgO, NaF, and CaCl2 added at 6%, 5%, and 7% of the total mass of the slag system respectively, and the total mass of the slagging agent accounting for 60% of the mass of the depleted automotive catalyst) are crushed, graded, and agglomerated to a size of 5cm. The agglomerated slag is then dried at 373K for 24 hours, resulting in a density of 1.978g / cm³. 3 .

[0042] Step 2: Use the waste material from cutting the battery diffusion sheet (Si content is 86.21wt%) as a silicon source, crush and grade it into 5cm pellets, and dry it at 373K for 24 hours.

[0043] Step 3: Place the light slag pellets in a low-frequency electric arc furnace for pre-melting. The low-frequency electric arc furnace operates at a frequency of 10 Hz, the pre-melting temperature is 1673 K, the melting time is 0.5 h, and the cooling method is air cooling, finally obtaining a pre-melted slag pool.

[0044] Step 4: Add the silicon agglomerate obtained in Step 2 into an electric arc furnace for melting at a silicon-to-slag ratio of 0.8:1. The melting temperature is 1723K, and the melting time is 3 hours. After melting and collection, the slag floats on the surface of the molten silicon and is discharged from the top while still in a molten state.

[0045] Step 5: After removing the slag, add the mixed slag agent obtained in Step 1 back into the low-frequency electric arc furnace, and continue to repeat Steps 3 and 4. After 6 smeltings, the three rare metals reach the containment limit in the silicon melt. After cooling, the silicon melt yields a rare metal enrichment. The direct recovery rates of the three rare metal elements are Pt 93.23%, Pd 95.72%, Rh 93.51%, Zr 91.69%, and Ce 94.35%.

[0046] Step 6: The enriched rare metal silicon ingots obtained in Step 5 are crushed, classified, and ground to less than 75 micrometers. They are then acid-washed with aqua regia (HCl (analytical grade) and HNO (analytical grade) in a volume ratio of 3:1, with a solid-liquid ratio of 1:10 g / ml, an acid-washing temperature of 353K, and an acid-washing time of 4 hours. After filtration, silicon powder and a leachate containing rare metal elements are obtained.

[0047] Example 3

[0048] like Figure 1 As shown, a method for the synergistic recovery and enrichment of rare metals from rare metal waste using silicon and a low-frequency electric arc furnace includes the following process steps:

[0049] Step 1: Crush and classify the anode mud (containing 1.12 wt% Au, 7.21 wt% Ag, and 22.32 wt% Cu) and mix it with a sodium-silicon-based lightweight slagging agent (melting density 2.06 L / cm³). 3 The pellets are 5cm in size and dried at 373K for 24 hours with a moisture content of no more than 10%. They are then placed in a low-frequency electric arc furnace for pre-melting. The low-frequency electric arc furnace operates at a frequency of 25Hz, the pre-melting temperature is 1673K, the melting time is 0.5h, and the cooling method is air cooling. Finally, a pre-melted slag pool is obtained.

[0050] Step 2: Use silicon ingot cutting waste (Si content is 76.52wt%) as silicon source, crush, grade and form into 5cm agglomerates, and dry at 373K for 24 hours.

[0051] Step 3: Continuously add the blocky silicon material obtained in Step 2 into the pre-melted slag pool obtained in Step 1 at a silicon-slag mass ratio of 1:2. The melting temperature is 2023K, and the melting time is 3 hours. After melting and collection, the slag floats on top of the molten silicon and is discharged from the top while still molten.

[0052] Step 4: After removing the slag, add the mixed slag agent obtained in Step 1 back into the low-frequency electric arc furnace, and continue to repeat Step 2. After three smelting processes, the three rare metals reach their capacity limit in the silicon melt. After cooling, the silicon melt yields a rare metal enrichment. The direct recovery rates of the three rare metal elements are Au 99.39%, Ag 95.39%, Pt 83.26%, and Ce 86.33%, respectively.

[0053] Step 5: The enriched rare metal silicon ingots obtained in Step 5 are crushed, classified, and ground to less than 75 micrometers. They are then acid-washed with aqua regia (HCl (analytical grade) and HNO3 (analytical grade) in a volume ratio of 3:1, with a solid-liquid ratio of 1:10 g / ml, an acid-washing temperature of 353K, and an acid-washing time of 4 hours. After filtration, silicon powder and a leachate containing rare metal elements are obtained.

[0054] Example 4

[0055] like Figure 1 As shown, a method for the synergistic recovery and enrichment of rare metals from rare metal waste using silicon and a low-frequency electric arc furnace includes the following process steps:

[0056] Step 1: The depleted petrochemical catalyst (containing 2500 g / t of platinum, rhodium, and palladium) is crushed and classified, and then mixed with an aluminum-silicon based high-density alkaline slag agent (melting density 3.254 g / cm³). 3The material is shaped into 10cm pellets, dried at 373K for 12 hours with a moisture content of no more than 5%, and then pre-melted in a low-frequency electric arc furnace with a working frequency of 25Hz, a pre-melting temperature of 1673K, a melting time of 1 hour, and air cooling. The final product is a pre-melted slag pool.

[0057] Step 2: Use silicon ingot cutting waste (Si content is 76.52wt%) as silicon source, crush, grade and form into 5cm agglomerates, and dry at 373K for 24 hours.

[0058] Step 3: Continuously add the silicon material obtained in Step 2 into the pre-melted slag pool obtained in Step 1 at a silicon-to-slag mass ratio of 1:3. The melting temperature is 1923K, and the melting time is 3 hours. After melting and collection, the molten silicon floats on the slag. The molten silicon is discharged from the top in a molten state and reused as new silicon material. The slag is discharged and cooled to a glassy state.

[0059] Step 4: After removing the slag, add the mixed slag agent obtained in Step 1 and the silicon material obtained in Step 2 to the low-frequency electric arc furnace at a silicon-to-slag ratio of 1:3. Continue to repeat Step 3. After four smelting cycles, the three rare metals reach their capacity limit in the silicon melt. After cooling, the silicon melt yields a rare metal enrichment. The direct recovery rates of the three rare metal elements are Pt 96.73%, Pd 93.62%, and Rh 97.58%.

[0060] Step 5: The enriched rare metal silicon ingots obtained in Step 5 are crushed, classified, and ground to a size of less than 100 micrometers. First, a mixed acid solution of hydrochloric acid, sulfuric acid, and hydrofluoric acid with a volume ratio of 3:1:1 (the concentrations of hydrochloric acid, sulfuric acid, and hydrofluoric acid were all 20 mol / L before mixing) is used as the leaching solution. The liquid-to-solid ratio is 2:1 mL / g, the leaching temperature is 373 K, and the leaching time is 24 h. Then, aqua regia (HCl (analytical grade) and HNO3 (analytical grade) with a volume ratio of 3:1 is used for acid washing. The solid-to-liquid ratio is 1:10 g / ml, the acid washing temperature is 353 K, and the acid washing time is 4 h. After filtration, silicon powder and a leaching solution containing rare metal elements are obtained.

[0061] Example 5

[0062] like Figure 1 As shown, a method for the synergistic recovery and enrichment of rare metals in rare metal waste by silicon and low-frequency electric arc furnace is described. In the preparation method, except that the slag agent mentioned in step (3) is replaced with a light calcium-aluminum slag system (equal mass mixture of Al2O3 and CaF2, MgO, NaF and CaO accounting for 5%, 10% and 15% of the total mass of the slag system, respectively, and the total mass of the slag agent accounting for 40% of the total mass of the recovered waste), the other conditions are the same as in Example 2, so they will not be described in detail here.

[0063] Example 6

[0064] like Figure 1 As shown, a method for synergistic recovery and enrichment of rare metals in rare metal waste by silicon and low-frequency electric arc furnace is described. In the preparation method, except that the rare metal waste in step (1) is replaced with neodymium iron boron magnet rare earth waste (neodymium 19.50%, praseodymium 4.86%, dysprosium 2.36%), the other conditions are the same as in Example 1, so they will not be repeated here.

[0065] Example 7

[0066] like Figure 1 As shown, a method for the synergistic recovery and enrichment of rare metals in rare metal waste by silicon and low-frequency electric arc furnace is described. In the preparation method, except that the rare metal waste in step (1) is replaced with recycled electronic circuit boards (silver and platinum content is 1500g / t), the other conditions are the same as in Example 1, so they will not be described in detail here.

[0067] The objectives, technical solutions, and beneficial effects of the present invention have been further described in detail above with reference to the accompanying drawings. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the synergic enrichment of the tri-rare metals in tri-rare metal waste material with a silicon and a low frequency electric arc furnace, characterized by, The method comprises the following steps: (1) crushing, grading and drying the waste containing three rare metals, mixing the waste with slagging agent to make pellets, and drying the pellets to obtain pellets containing three rare metals, wherein the slagging agent comprises high-density slagging agent or low-density slagging agent, the high-density slagging agent has a density higher than 2.5 g / cm3 and a melting point lower than 1400 ℃, and the low-density slagging agent has a density lower than 2.0 g / cm3; the waste containing three rare metals is recovered as a silicon source, and is crushed, graded, and dried to obtain silicon pellets; (2) putting the pellets containing three rare metals obtained in step (1) into a low-frequency electric arc furnace to pre-melt for a period of time to obtain a pre-melted slag pool; (3) adding the silicon blocks obtained in step (1) into the pre-melted slag pool obtained in step (2) according to a certain ratio to perform high-temperature smelting, so as to improve the reaction efficiency between materials in the low-frequency electric arc furnace, and after a period of smelting and recovery, molten silicon and molten slag are obtained, the molten silicon is cooled to form a silicon ingot, and then silicon slag separation and remelting are performed, wherein the silicon slag separation and remelting process route mainly comprises the following two routes: Route 1: for the high-density slagging agent obtained in step (1), the molten silicon is floated on the upper part of the molten slag after smelting, and is discharged first as new silicon material for standby, the molten slag is then discharged, and is condensed to form glass slag for next step; steps (2) and (3) are continuously repeated, the new silicon material obtained is added into the low-frequency electric arc furnace as a silicon source for smelting until the silicon containing limit is reached; Route 2: for the low-density slagging agent obtained in step (1), the molten slag is floated on the molten silicon after smelting, the molten silicon is reserved in the electric arc furnace after slagging, and the slag pellets obtained in step (1) are added into the low-frequency electric arc furnace according to a certain ratio for smelting until the silicon containing limit is reached; (4) crushing and grinding the silicon ingot obtained in step (3) to perform wet separation and purification, to obtain three rare metal concentrates and pure silicon material, the three rare metal concentrates are further leached, purified and separated, and the pure silicon material is repeatedly used as a silicon source or is used as a raw material for producing solar-grade silicon.

2. A process for the co-enrichment of the tri-rare metals in tri-rare metal waste material by silicon in a low frequency electric arc furnace as claimed in claim 1, characterized in that, The waste containing three rare metals recovered in step (1) comprises scrap automobile exhaust three-way catalyst, failed petroleum chemical catalyst, industrial catalyst containing rare and precious metals, anode slime, electronic product recovery waste, aerospace recovery waste and other slag containing three rare metals.

3. A process for the co-enrichment of the tri-rare metals in tri-rare metal waste material by silicon in a low frequency electric arc furnace as claimed in claim 1, characterized in that, The waste containing three rare metals used as a raw material in step (1) comprises one or more of waste containing rare earth metals, waste containing rare metals and waste containing rare and dispersed metals.

4. A process for the co-enrichment of the tri-rare metals in tri-rare metal waste material by silicon in a low frequency electric arc furnace as claimed in claim 1, characterized in that, Two types of slag system design are required in step (1): high-density slag system with density higher than 2.5 g / cm 3 and melting point lower than 1400℃; low-density slag system with density lower than 2.0 g / cm 3 ; the slag forming agent includes one or more than two of Al2O3, SiO2, CaO, MgO, CaF2, NaF, BaO, FeO, BaF2, MnO, CaCl2, and the addition amount is determined according to the specific requirements of slag forming.

5. A process for the co-enrichment of the tri-rare metals in tri-rare metal waste material by silicon in a low frequency electric arc furnace as claimed in claim 1, characterized in that, The waste in step (1) is crushed, graded and dried, and is mixed with slagging agent to make pellets, and the pellets are dried, the size of the pellets is 5-10 cm, and the water content of the pellets is lower than 5%.

6. A process for the co-enrichment of the tri-rare metals in tri-rare metal waste material by silicon in a low frequency electric arc furnace as claimed in claim 1, characterized in that, The silicon material in step (1) comprises industrial silicon tailings, solar-grade polysilicon waste, battery diffusion sheet cutting waste and diamond wire silicon wafer cutting waste.

7. A process for the co-enrichment of the tri-rare metals in tri-rare metal waste material by silicon in a low frequency electric arc furnace as claimed in claim 1, characterized in that, The silicon material in step (1) is crushed, graded and dried to make pellets, the size of the pellets is 5-10 cm, and the water content of the pellets is lower than 5%.

8. A process for the co-enrichment of the tri-rare metals in tri-rare metal waste material by silicon in a low frequency electric arc furnace as claimed in claim 1, characterized in that, The pre-melting temperature in step (2) is 1573 K-1673 K; the equipment is a low-frequency electric arc furnace, the working frequency of the equipment is 1-45 Hz; and the cooling method is air cooling, and the cooling rate is 0.1-15 ℃.

9. A process for the co-enrichment of the tri-rare metals in tri-rare metal waste material by silicon in a low frequency electric arc furnace as claimed in claim 1, characterized in that, The smelting in step (3) is smelting enrichment by putting the silicon material pellets into the pre-melted slag for a small number of times, the mass ratio between the silicon slag is 0.1:1~2:1, the smelting temperature range is 1723K~1973K, the holding time is not less than 1h, the cooling mode is air cooling, and the cooling rate is 0.1~15℃.

10. A process for the co-enrichment of the tri-rare metals in tri-rare metal waste material by silicon in a low frequency electric arc furnace as claimed in claim 1, characterized in that, The means for separating and purifying the three rare metals in step (4) is wet leaching, the leaching agent is a mixture containing one or more of hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid in any proportion, the acid concentration is 0.1~100wt.%, the mass ratio of silicon to acid is 1:0.1~1:1200, the acid pickling temperature is 15~100℃, and the acid pickling time is 0.5~24h.

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