CN116239122B

CN116239122B - A method for preparing high-purity silicon by cutting crystalline silicon waste from solar cells

Info

Publication number: CN116239122B
Application number: CN202310040900.8A
Authority: CN
Inventors: 魏创林; 魏伟; 王凯; 魏佳新; 魏波; 李健仁; 赵红波; 乔泓博; 寇娟; 陆江婷; 岳进
Original assignee: Shizuishan Baoma Xingqing Special Alloy Co ltd
Current assignee: Shizuishan Baoma Xingqing Special Alloy Co ltd
Priority date: 2023-01-12
Filing date: 2023-01-12
Publication date: 2025-02-07
Anticipated expiration: 2043-01-12
Also published as: CN116239122A

Abstract

The present invention provides a method for preparing high-purity silicon by cutting crystalline silicon waste from solar cells, adding silicon mud to a submerged arc furnace to prepare molten silicon, and performing component detection on the molten silicon; then by means of powder spraying, a fly ash slag-making agent with fly ash as a carrier is introduced into the submerged arc furnace, and an inert gas is continuously introduced into the submerged arc furnace, and the high-temperature molten silicon in the submerged arc furnace is subcontracted to a refining furnace, and the temperature in the refining furnace is maintained at 1800°C to 2200°C, and the molten silicon is subjected to component detection; then by means of powder spraying, fly ash-iron removal agent sintered body particles with fly ash as a carrier are introduced into the refining furnace, and an inert gas is introduced into the refining furnace. The present application makes full use of the porous form of the fly ash structure, and the oxides formed by metal impurities are adsorbed and adhered and aggregated together, thereby improving the slag removal efficiency, and by means of two impurity removal methods, the impurity content in the molten silicon is significantly reduced.

Description

Method for preparing high-purity silicon by cutting crystalline silicon waste by using solar cell

Technical Field

The invention belongs to the technical field of high-purity industrial silicon preparation, relates to a method for preparing high-purity industrial silicon by utilizing cut silicon waste, and in particular relates to a method for preparing high-purity silicon by utilizing solar cell cut crystalline silicon waste.

Background

The industrial silicon is also called metallic silicon or crystalline silicon, the traditional preparation method is a product which is formed by smelting silica and a carbonaceous reducing agent in an ore smelting furnace through high-temperature reaction, the content of the main component silicon element is about 98 percent, and the rest impurities are iron, aluminum, calcium and the like. The properties are similar to germanium, lead and tin, and can be used for semiconductors and the like.

According to the requirements of specific applications on microelements, silicon for chemical use and silicon for metallurgy use are also classified. Industrial silicon is classified into 8 brands according to the national standard (GBT 2881-2014), the brands are expressed in a mode of combining silicon element symbols with 4 digits, and the metalloid silicon can be classified into 5530#, 5210#, 4410#, 4210#, 4110#, 3303#, 2202#, 1101#, and the like. Among them, si4210 is required to be the largest, and Si5530 is widely used. In particular, the purity requirement of Si 5520-Si 1101 on silicon is not less than 99.20 to not less than 99.79 percent, and the traditional smelting method has very high power consumption and great smelting difficulty.

In the preparation of crystalline silicon solar cell materials from silicon feedstock, it is necessary to cut a silicon ingot into silicon slices. In the cutting process, nearly half of silicon enters the cutting liquid in the form of superfine powder to form a large amount of cutting waste, so that silicon resource waste and environmental pollution are caused. When the diamond cuts a silicon rod or a silicon ingot, in order to ensure the machining precision and improve the surface quality of a silicon wafer, auxiliary cutting liquid is needed to lubricate and rinse a cutting surface to form silicon mud. The silicon mud comprises silicon powder generated by diamond in the process of cutting a silicon rod or a silicon ingot, diamond wire abrasion and falling matters in the diamond cutting process containing metal impurities, flocculating agent and cooling liquid in the cutting process, wherein the average size of the silicon powder is 1-5 mu m, and the cutting waste silicon mud consists of about 90% of silicon powder and a small amount of Fe, al and Ca as well as impurities such as water, diethylene glycol or ethylene glycol or polyethylene glycol.

Because the silicon powder in the silicon mud is smaller in size and contains moisture and non-silicon impurities, the recycling difficulty is high. The silicon sludge is generally used as a refractory material through drying and dehydration or is used as a raw material for iron and steel smelting after simple sintering, so that a large amount of silicon sludge cannot be effectively recycled and applied to polysilicon processing. Because the silicon mud is low in cost and cannot be effectively and repeatedly used for processing the silicon wafer, the production cost of the polysilicon is limited, and the energy waste is caused.

Chinese patent document CN115504476A discloses a method for producing high-purity silicon by utilizing recycled silicon mud, which comprises the steps of adding prepared mixed solution into the silicon mud, filtering after stirring reaction to obtain a mixture A, adding the mixture A into hydrofluoric acid solution for pickling, cleaning and drying by using high-purity water after pickling to obtain silicon powder, adding the silicon powder into an electron beam vacuum furnace for smelting and purifying to obtain silicon ingots, sawing the surfaces of the silicon ingots, and sawing the surfaces of the silicon ingots to obtain the high-purity silicon ingots. Through detection, the purity of the high-purity silicon ingot can reach 99.9999%, reach an electronic grade, and far exceed the purity of the silicon ingot obtained by smelting and recycling silicon mud through an intermediate frequency induction furnace, an electric arc furnace or a resistance furnace and the like in the prior art. Although the purity of the high-purity silicon obtained by the method reaches an electron level, the method uses an electron beam vacuum furnace for smelting and purifying, has high requirements on equipment and high energy consumption.

Chinese patent CN 111498852A discloses a device for producing high purity industrial silicon and a preparation method thereof, the device adopts a common slag former to remove impurities, the content of the slag former is about 50% of the total mass of the silicon solution, and the consumption of the slag former is relatively large. Further, the content of the raw silicon solution in the patent document is not clear, and therefore, the purity of the high purity silicon described in the patent document cannot be accurately evaluated for the technical effect of the method.

Chinese patent document CN114890428A discloses a ternary slag former for external refining of industrial silicon and a method for removing impurities, wherein the ternary slag former is SiO2-Al ₂O₃ -ZnO, and the melting point is 1305-1500 ℃. According to the impurity removal method, compressed gas is introduced into a ladle, a ternary slag former is added into an industrial silicon melt for reaction for 30-60 min, and a compound formed by the reaction of impurities in the silicon solution and the ternary slag former volatilizes and overflows the industrial silicon melt, but the patent states that impurity iron in the industrial silicon can react with free zinc in the slag former, but ZnO in the slag former cannot be reduced to Zn under the condition of no reducing agent according to the common knowledge in the field, even if the ternary slag former contains free zinc, because the boiling point of the zinc is 907 ℃ and the melting point of the Fe is up to 1500 ℃, the reaction of the impurity iron described in the patent with the free zinc in the slag former cannot occur.

In summary, the main technical difficulty of preparing the high-purity industrial silicon with the purity of more than 99% from the crystalline silicon cutting waste is to reduce the content of impurities such as Fe, al, ca and the like in the silicon mud. The problems of the method for preparing high-purity silicon by cutting crystalline silicon waste by using a solar cell in the prior art include ① smelting and purifying in an electron beam vacuum furnace to obtain a silicon ingot, which is equivalent to the method for preparing electronic grade high-purity silicon by using a normal method, the energy consumption is high, ② uses a common slag former to remove impurities in silicon mud, but the slag former consumes more. ③ Composite slag forming agent is adopted, but the slag forming efficiency is improved. ④ The removal of iron impurities from the silicon solution by the slag former is relatively difficult.

Disclosure of Invention

In order to solve the technical problems in the prior art, the application provides a method for preparing high-purity silicon by utilizing solar cell cut crystalline silicon waste, which adopts a smelting method to prepare high-purity industrial silicon, the application firstly uses an ore smelting furnace to smelt in the smelting process, and after impurities are removed, transferring the molten liquid into a refining furnace for secondary refining and removing impurity elements, converting a small amount of electric energy into heat energy through the refining furnace, keeping the temperature, adopting chemical and physical purification measures, finally accurately producing high-purity industrial silicon with required indexes, and achieving the effects of energy conservation, consumption reduction and comprehensive utilization of resources.

The application relates to a method for preparing high-purity silicon by utilizing solar cell cut crystalline silicon waste, which comprises the following steps:

A method for preparing high-purity silicon by utilizing solar cell cut crystalline silicon waste material is used for preparing high-purity silicon with silicon content more than or equal to 99 percent, and comprises the following steps:

s1, placing silicon mud in an ore-smelting furnace to prepare silicon melt, keeping the temperature of the silicon melt at not lower than 1800 ℃, fully melting the silicon mud into the silicon melt, and detecting the components of the silicon melt;

s2, introducing a fly ash slagging agent taking fly ash as a carrier into the submerged arc furnace in a powder spraying mode, continuously introducing inert gas into the submerged arc furnace, and fully smelting, wherein the fly ash slagging agent is fly ash-slagging agent sintered body particles, the mass ratio of the fly ash to the slagging agent in the fly ash-slagging agent sintered body particles is 30-35:65-70, and the total mass of the introduced fly ash-slagging agent sintered body particles is 10-15% of the total mass of the silicon melt.

S3, slowly flowing high-temperature silicon melt in the submerged arc furnace into the refining furnace, keeping the temperature in the refining furnace at 1800-2200 ℃, and detecting the components of the silicon melt;

S4, introducing fly ash-iron remover sintered body particles taking fly ash as a carrier into a refining furnace in a powder spraying mode, introducing inert gas into the refining furnace, and fully smelting, wherein the mass ratio of the fly ash to the iron remover in the fly ash-iron remover sintered body particles is 45-55:45-55, and the total mass of the introduced fly ash-iron remover sintered body particles is 5-10% of the total mass of the silicon melt.

S5, taking the silicon melt in the refining furnace for component detection, and discharging the prepared high-purity silicon after the predetermined components are reached.

In the application, in the step S1, in the process of heating the silicon sludge in the submerged arc furnace to form the melt, water, diethylene glycol or flocculating agent such as ethylene glycol or polyethylene glycol and the like mixed in the silicon sludge can be gradually volatilized and removed, and impurities in the cooling liquid are gradually removed. In the process of silicon melting, fe, al, ca and other impurities mixed in the silicon mud are uniformly dissolved in the silicon melt, so that the Fe, al, ca and other impurities can react with the slag former to form oxides.

Maintaining the temperature of the silicon melt at not lower than 1800 ℃ and preserving heat for more than 30 minutes, after the silicon mud is fully melted into the melt, and dispersing impurities in the silicon mud into the silicon melt, adding a slag former taking fly ash as a carrier into the silicon melt in a powder spraying mode through a step S2, and continuously introducing inert gas into the silicon melt to prevent oxygen from entering the silicon melt to generate silicon oxide. Under the action of slag former, al, ca and other main impurities in the molten silicon form low-density oxide, which floats to the surface of the molten silicon.

After the main impurities such as Al, ca and the like in the silicon melt are removed in the step S2, the main impurities in the silicon melt are Fe. However, fe and Fe oxides are difficult to remove by conventional slag formers. For this purpose, the silicon melt from which the main impurities such as Al and Ca have been removed is transferred to a refining furnace by step S3, and the temperature in the refining furnace is maintained at a temperature higher than 1800 ℃ and lower than 2200 ℃.

After the silicon melt is stood, spraying fly ash-iron removing agent sinter into the silicon melt in a powder spraying mode,

The iron removing agent comprises 30-40 wt% of CaF ₂,30～40wt％AlSn,20～30wt％Na₂SiF₆.

Iron removing agent and iron in the sinter are utilized to generate iron-containing intermetallic compounds at high temperature, the iron-containing intermetallic compounds are gathered on the fly ash melt, and substances such as Al, ca and the like remained in the silicon melt are focused together under the action of the fly ash and float on the upper layer of the silicon melt.

The method can remove impurities in the silicon melt, and can obtain high-purity industrial silicon with purity higher than 99%.

In order to improve the slag forming efficiency, the particle size of the fly ash-slag former sintered body in the step S2 is 60-20 meshes.

In order to improve the production efficiency of the iron-aluminum alloy, the particle size of the fly ash-iron remover sintered body in the step S3 is 30-10 meshes.

The preparation method of the step S2 fly ash-slag former sintered body particles comprises the steps of mixing 30-35 parts of fly ash and 65-70 parts of slag former together, adding water accounting for 20% -25% of the total mass of the fly ash and the slag former, fully mixing the fly ash and a binder accounting for 5% -15% of the total mass of the slag former, granulating on a granulator, carrying out heat preservation sintering at a high temperature of 1100-1200 ℃, crushing and screening particles with 60-20 meshes after natural cooling, and taking the binder as water glass.

The main components of the fly ash are about 90% of the total amount of SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂, caO and the like, the components are the same as the slag former, the porosity is generally 60% -75%, the fly ash has a porous structure, the specific surface area is generally 2500-5000 m ²/g, the fly ash has stronger adsorption capacity, meanwhile, the fly ash consists of a plurality of particles with different structures and forms, the particle size of single fly ash particles is about 25-300 mu m, the tap density of the fly ash is 2-3 g/cm ³, the stacking density is 0.6-1.2 g/cm ³, the fly ash and the slag former are sintered into a sintered body slag former, after the silicon melt is added, the impurities in the silicon melt can be accelerated to be adsorbed around the sintered body in the early stage, the impurities can be oxidized into oxides by the slag former along with the progress of the reaction, the formed novel oxides are adhered around the slag former and float above the silicon melt together, and the impurities are removed. The application fully utilizes the porous form of the fly ash structure, and the formed oxides are gathered together by utilizing the adhesiveness of the oxides at high temperature after being adsorbed, thereby improving the deslagging efficiency.

Further, the preparation method of the sintered body particles of the fly ash-iron removing agent in the step S4 comprises the steps of mixing 45-55 parts of fly ash and 45-55 parts of iron removing agent together, adding water accounting for 20% -25% of the total mass of the fly ash and the iron removing agent, fully mixing the fly ash and the binder accounting for 5% -15% of the total mass of the iron removing agent, pelletizing on a pelletizer, carrying out heat preservation and sintering at a high temperature of 1100-1200 ℃, naturally cooling, crushing and screening particles with 30-10 meshes, wherein the iron removing agent is CaF ₂,30～40％AlSn,20～30％Na₂SiF₆ with a mass fraction of 30-40%, and the binder is water glass.

Impurities in the silicon melt can be further removed through the fly ash-iron removing agent sintered body particles, an iron-zinc alloy melt is formed, the iron-zinc alloy melt is adhered to the fly ash melt, finally floats on the upper layer of the silicon melt, and Fe impurities are removed.

Further, the slag former is a composition formed by any one of SiO ₂、Al₂O₃、CaCl、CaCO₃ and CaO or a plurality of combinations thereof.

Further, the powder spraying flow of the powder spraying pipe is 10 kg/min-30 kg/min, and the powder spraying method is that powder is sprayed at intervals, such as at least once every 10 minutes.

The inert gas is sprayed with powder, and the spraying pressure is 1 mpa-5 mpa.

Further, the inert gas and the spray pipe used in the powder spraying process comprise a powder spraying pipe, and the inert gas pipe surrounds the inert gas arranged outside the powder spraying pipe. The powder spraying mode of the inert gas and the powder is a concentric circle powder spraying mode, the center of the concentric circle is a mixture of the inert gas and the cover, and the outer circle of the concentric circle is the inert gas.

Further, when the component detection in the step S5 does not reach the preset component, a fly ash slagging agent taking fly ash as a carrier is introduced into the refining furnace in a powder spraying mode, meanwhile, inert gas is continuously introduced into the submerged arc furnace and fully smelted, the fly ash slagging agent is fly ash-slagging agent sintered body particles, and/or the fly ash-iron removing agent sintered body particles taking the fly ash as the carrier are introduced into the refining furnace in a powder spraying mode, and meanwhile, the inert gas is introduced into the refining furnace.

According to the application, a powder spraying mode is adopted, the deslagging agent is introduced into the silicon melt, powder in the introduced silicon melt is rapidly dispersed, the deslagging agent and impurities in the silicon melt can be mixed, in the mixing process, siO ₂、Al₂O₃ in the deslagging agent can react with Al, ca and the like in the impurities, so that metal impurities such as Al, ca and the like in the silicon melt generate oxide objects such as Al ₂O₃, caO and the like, and the oxide objects are concentrated together to finally form a slag layer to float on the surface.

By using the powder spraying mode of concentric circles, the center of the concentric circles is a mixture of inert gas and a cover, and the outer circle of the concentric circles is inert gas, so that excessive oxygen is prevented from being introduced in the powder spraying process, silicon oxide is subjected to inert gas through the outer circle, on one hand, impurities such as Al, mg or Ca can be removed by vacuum directional solidification, and on the other hand, a powder spraying pipeline can be prevented from being blocked.

The total mass fraction of SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂ and CaO in the fly ash is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the bulk density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm, and the fly ash is high-calcium fly ash.

Further, the fly ash is high-calcium fly ash.

The application has the beneficial effects that:

1. The main component of the fly ash is characterized in that Al ₂O₃、SiO₂, caO and the like account for about 90% of the total amount, the composition is the same as that of a slag former, the porosity is generally 60% -75%, the fly ash has a porous structure, the specific surface area is generally 2500-5000 m ²/g, the fly ash has stronger adsorption capacity, meanwhile, the fly ash consists of a plurality of particles with different structures and forms, the particle size of single fly ash particles is about 25-300 mu m, the tap density of the fly ash is 2-3 g/cm ³, the stacking density is 0.6-1.2 g/cm ³, the fly ash and the slag former are sintered into a sintered body slag former, after the silicon melt is added, the impurities in the silicon melt can be accelerated to be adsorbed around the sintered body in the early stage, the impurities can be oxidized into oxides by the slag former along with the reaction of temperature, the formed oxides are adhered around the slag body, the slag body is gathered together and float above the silicon melt, and the impurities are removed. The application fully utilizes the porous form of the fly ash structure, and the formed oxides are adhered and gathered together, thereby improving the deslagging efficiency.

2. According to the method, impurities in the silicon melt are removed twice, the temperature of the silicon melt is kept to be not lower than 1800 ℃, the temperature is kept for more than 30 minutes, after the silicon mud is fully melted into the melt, and the impurities in the silicon mud are dispersed in the silicon melt, a slag former taking fly ash as a carrier is added into the silicon melt in a powder spraying mode through a step S2, and meanwhile, inert gas is continuously introduced into the silicon melt to prevent oxygen from entering the silicon melt, so that silicon oxide is generated. Under the action of slag former, al, ca and other main impurities in the molten silicon form low-density oxide, which floats to the surface of the molten silicon. After the main impurities such as Al, ca and the like in the silicon melt are removed in the step S2, the main impurities in the silicon melt are Fe. However, it is difficult to oxidize Fe by conventional slag formers. For this purpose, in step S3, the silicon melt from which the main impurities such as Al and Ca have been removed is slowly flowed into the refining furnace, and the temperature in the refining furnace is maintained at a temperature higher than 1800 ℃ and lower than 2200 ℃. After the silicon melt is kept stand, a fly ash-iron removing agent sinter is sprayed into the silicon melt in a powder spraying mode, iron-containing intermetallic compounds are generated by utilizing the iron removing agent and iron in the sinter at high temperature and are gathered on the fly ash melt, and substances such as Al, ca and the like remained in the silicon melt are focused together under the action of the fly ash and float on the upper layer of the silicon melt. The method can remove impurities in the silicon melt, and can obtain high-purity industrial silicon with purity higher than 99%.

3. According to the application, a powder spraying mode is adopted, the deslagging agent is introduced into the silicon melt, powder in the introduced silicon melt is rapidly dispersed, the deslagging agent and impurities in the silicon melt can be mixed, in the mixing process, siO ₂、Al₂O₃ in the deslagging agent can react with Al, ca and the like in the impurities, so that metal impurities such as Al, ca and the like in the silicon melt generate oxide objects such as Al ₂O₃, caO and the like, and the oxide objects are concentrated together to finally form a slag layer to float on the surface. By using the powder spraying mode of concentric circles, the center of the concentric circles is a mixture of inert gas and a cover, the outer circle of the concentric circles is inert gas, so that excessive oxygen is prevented from being introduced in the powder spraying process, silicon is oxidized, and impurities such as Al, mg or Ca can be removed through vacuum directional solidification through the inert gas of the outer circle, and the silicon solution can be prevented from blocking a powder spraying pipeline.

Drawings

FIG. 1 is a schematic view of a powder spraying pipe according to the present application;

in the figure, a powder spraying pipeline 1, a powder spraying pipeline 2 and an inert gas pipeline, wherein an arrow in the figure indicates the powder spraying direction or the inert gas direction.

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

Example 1

A method for preparing high-purity silicon by utilizing solar cell cut crystalline silicon waste material is used for preparing industrial silicon with purity higher than 99 percent, and comprises the following steps:

S1, adding 600kg of spherical silicon mud into an ore heating furnace to prepare silicon melt, heating, controlling the temperature of molten silicon to 1800 ℃, preserving heat for 30min, and detecting the components of the silicon melt to obtain silicon melt, wherein the silicon melt comprises silicon 88.26%, al 0.17%, ca 0.23%, ba 0.12%, fe 0.85% and B0.08%.

S2, 72kg of coal ash-slag former sintered body particles taking coal ash as a carrier are introduced into the submerged arc furnace in a powder spraying mode of 10kg/min for 1min each time and 10min each time, wherein the particle size is 60-20 meshes, argon is continuously introduced into the submerged arc furnace at the flow rate of 6-7L/min, the coal ash slag former is coal ash-slag former sintered body particles, the mass ratio of the coal ash to the slag former is 30:70, the mass fraction of the slag former is 30% SiO ₂、30％Al₂O₃,20％BaO,20％CaCO₃, the coal ash is SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂, the total mass fraction of CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the bulk density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm coal ash, the total mass of the introduced coal ash-slag former sintered body particles is 12% of the total mass of the silicon melt, and after the powder spraying is completed, the silicon melt is fully carried out in the submerged arc furnace for 1 hour. As shown in fig. 1, the powder spraying mode of the inert gas and the powder spraying particles in the step is a concentric circle powder spraying mode, the spray pipe used in the inert gas and the powder spraying process comprises a powder spraying pipeline 1, an inert gas pipeline 2 surrounding the inert gas arranged outside the powder spraying pipeline 1, the center of the concentric circle is a mixture of the inert gas and the powder spraying particles, and the outer circle of the concentric circle is the inert gas.

S3, after the slag floating in the step S2 is removed, 520kg of high-temperature silicon melt with the temperature not lower than 1800 ℃ is slowly flowed into a refining furnace, the temperature in the refining furnace is kept at 1800-2200 ℃, and after standing for 30min, the silicon melt is subjected to component detection, and Si 98.52%, fe 0.63%, al 0.06%, ca 0.03%, ba <0.01% and B <0.01% are detected.

S4, in a powder spraying mode that the flow is 10kg/min, powder spraying is carried out for 1min each time, powder spraying is carried out for 10min each time, 30kg of fly ash is taken as a carrier, the particle size is 30-10 meshes, meanwhile, argon is continuously introduced into the refining furnace at the flow rate of 6-7L/min, the mass ratio of the fly ash to the iron remover in the fly ash-iron remover is 45:55, the total mass fraction of the fly ash is SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂, the total mass fraction of CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the stacking density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm of fly ash, the total mass of the introduced fly ash-iron remover sintered body particles is 5% of the total mass of the silicon melt, and after powder spraying is finished, the silicon melt is fully slagging in a submerged arc furnace for 0.5 hours. As shown in FIG. 1, the powder spraying mode of the inert gas and the powder spraying particles in the step is a concentric circle powder spraying mode, the center of the concentric circle is a mixture of the inert gas and the powder spraying particles, and the outer circle of the concentric circle is the inert gas.

S5, taking silicon melt in the refining furnace for component detection, and obtaining Si 99.37%, fe <0.01%, al <0.01%, ca <0.01%, ba <0.01%, B <0.01% in the silicon melt, and obtaining 513kg of high-purity industrial silicon with purity higher than 99%.

Example 2

S1, adding 600kg of spherical silicon mud into an ore heating furnace to prepare silicon melt, heating, controlling the temperature of molten silicon to 1800 ℃, preserving heat for 30min, and detecting the components of the silicon melt to obtain silicon melt, wherein the silicon melt contains 85.36%, 0.23% of Al, 0.86% of Ca, 0.12% of Ba, 0.37% of Fe and 0.03% of B.

S2, 90kg of coal ash-slag former sintered body particles taking coal ash as a carrier are introduced into the submerged arc furnace in a powder spraying mode of spraying powder for 1min each time at intervals of 20min, wherein the particle size is 60-20 meshes, argon is continuously introduced into the submerged arc furnace at the flow rate of 6-7L/min, the coal ash slag former is coal ash-slag former sintered body particles, the mass ratio of the coal ash to the slag former is 35:65, the mass fraction of the slag former is 60% SiO ₂、20％Al₂O₃,20％CaCl₂, the coal ash is SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂, the total mass fraction of CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the bulk density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm coal ash, the total mass of the introduced coal ash-slag former sintered body particles is 15% of the total mass of the silicon melt, and after the powder spraying is completed, the silicon melt is fully slagging in the submerged arc furnace for 1.5 hours. As shown in FIG. 1, the powder spraying mode of the inert gas and the powder spraying particles in the step is a concentric circle powder spraying mode, the center of the concentric circle is a mixture of the inert gas and the powder spraying particles, and the outer circle of the concentric circle is the inert gas.

S3, after the slag floating in the step S2 is removed, 510kg of high-temperature silicon melt with the temperature not lower than 1800 ℃ is slowly flowed into a refining furnace, the temperature in the refining furnace is kept at 1800-2200 ℃, and after standing for 30min, the silicon melt is subjected to component detection, and 98.23% of Si, 0.34% of Fe, 0.06% of Al and 0.03% of Ca are detected.

S4, 60kg of fly ash serving as a carrier is introduced into a refining furnace in a powder spraying mode of spraying powder for 30S each time at intervals of 10min, wherein the particle size of the particles is 30-10 meshes, argon is continuously introduced into the refining furnace at the flow rate of 6-7L/min, the mass ratio of the fly ash to the iron remover in the fly ash-iron remover sintered particles is 55:45, the total mass fraction of SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂ and CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the stacking density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm, the fly ash is high-calcium fly ash, the total mass of the introduced fly ash-iron remover sintered particles is 5% of the total mass of the silicon melt, and after powder spraying is completed, the silicon melt is fully slagging in a submerged arc furnace for 1 hour. As shown in FIG. 1, the powder spraying mode of the inert gas and the powder spraying particles in the step is a concentric circle powder spraying mode, the center of the concentric circle is a mixture of the inert gas and the powder spraying particles, and the outer circle of the concentric circle is the inert gas.

S5, taking silicon melt in the refining furnace for component detection, and obtaining Si 99.56%, fe <0.01%, al <0.01%, ca <0.01%, ba <0.01%, B <0.01% in the silicon melt, and obtaining 473kg of high-purity industrial silicon with purity higher than 99%.

Example 3

s1, adding 600kg of spherical silicon mud into an ore heating furnace to prepare silicon melt, heating, controlling the temperature of molten silicon to 1800 ℃, preserving heat for 30min, and detecting the components of the silicon melt to obtain silicon melt, wherein silicon 88.37%, al 0.46%, ca 0.35% and Ba 0.12% Fe 0.42%.

S2, 60kg of coal ash-slag former sintered body particles taking coal ash as a carrier are introduced into the submerged arc furnace in a powder spraying mode of spraying powder for 0.5min each time and spraying powder for 5min each time, wherein the particle size is 60-20 meshes, meanwhile, argon is continuously introduced into the submerged arc furnace at the flow rate of 6-7L/min, the coal ash slag former is coal ash-slag former sintered body particles, the mass ratio of the coal ash to the slag former is 35:65, the mass fraction of the slag former is 60% SiO ₂、40％Al₂O₃, the coal ash is SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂, the total mass fraction of CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the bulk density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm of coal ash, the total mass of the introduced coal ash-slag former sintered body particles is 10% of the total mass of the silicon melt, and after the powder spraying is completed, the silicon melt is fully slagging in the submerged arc furnace for 1.5 hours. As shown in FIG. 1, the powder spraying mode of the inert gas and the powder spraying particles in the step is a concentric circle powder spraying mode, the center of the concentric circle is a mixture of the inert gas and the powder spraying particles, and the outer circle of the concentric circle is the inert gas.

S3, after the slag floating in the step S2 is removed, 530kg of high-temperature silicon melt with the temperature not lower than 1800 ℃ is slowly flowed into a refining furnace, the temperature in the refining furnace is kept at 1800-2200 ℃, and after standing for 30min, the silicon melt is subjected to component detection, and Si 97.36%, fe 0.42%, al 0.09% and Ca 0.01% are detected.

S4, 60kg of fly ash serving as a carrier is introduced into a refining furnace in a powder spraying mode of spraying powder for 0.5min each time and spraying powder for 10min each time, wherein the particle size is 30-10 meshes, argon is continuously introduced into the refining furnace at the flow rate of 6-7L/min, the mass ratio of the fly ash to the iron remover in the fly ash-iron remover sintered body particles is 50:50, the total mass fraction of the fly ash is SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂, the total mass fraction of CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the stacking density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm of fly ash, the fly ash is high-calcium fly ash, the total mass of the introduced fly ash-iron remover sintered body particles is 10% of the total mass of the silicon melt, and after the powder spraying is completed, the silicon melt is fully slagging in a submerged arc furnace for 1 hour. As shown in FIG. 1, the powder spraying mode of the inert gas and the powder spraying particles in the step is a concentric circle powder spraying mode, the center of the concentric circle is a mixture of the inert gas and the powder spraying particles, and the outer circle of the concentric circle is the inert gas.

S5, taking silicon melt in the refining furnace for component detection, and obtaining Si 99.52%, fe <0.01%, al <0.01%, ca <0.01%, ba <0.01%, B <0.01% in the silicon melt, and discharging the silicon melt after detection qualification, thereby obtaining 464kg of high-purity industrial silicon with the purity higher than 99%.

Example 4

S1, adding 600kg of spherical silicon mud into an ore heating furnace to prepare silicon melt, heating, controlling the temperature of molten silicon to 1800 ℃, preserving heat for 30min, detecting the components of the silicon melt to obtain 87.15 percent of silicon, 0.53 percent of Al, 0.43 percent of Ca and 0.18 percent of Fe in the silicon melt,

S2, 72kg of coal ash-slag former sintered body particles taking coal ash as a carrier are introduced into the submerged arc furnace in a powder spraying mode of spraying powder for 1min each time at intervals of 10min, wherein the particle size is 60-20 meshes, argon is continuously introduced into the submerged arc furnace at the flow rate of 6-7L/min, the coal ash slag former is coal ash-slag former sintered body particles, the mass ratio of the coal ash to the slag former is 30:70, the mass fraction of the slag former is 40% SiO ₂、50％Al₂O₃,10％CaCl₂, the coal ash is SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂, the total mass fraction of CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the bulk density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm coal ash, the total mass of the introduced coal ash-slag former sintered body particles is 12% of the total mass of the silicon melt, and after the powder spraying is completed, the silicon melt is fully slagging in the submerged arc furnace for 1 hour. As shown in FIG. 1, the powder spraying mode of the inert gas and the powder spraying particles in the step is a concentric circle powder spraying mode, the center of the concentric circle is a mixture of the inert gas and the powder spraying particles, and the outer circle of the concentric circle is the inert gas.

S3, after the slag floating in the step S2 is removed, 520kg of high-temperature silicon melt with the temperature not lower than 1800 ℃ is slowly flowed into a refining furnace, the temperature in the refining furnace is kept at 1800-2200 ℃, and after standing for 30min, the silicon melt is subjected to component detection, and Si 98.36%, fe 0.31%, al <0.01% and Ca <0.01% are detected.

S4, 42kg of fly ash serving as a carrier is introduced into a refining furnace in a powder spraying mode of spraying powder for 1min each time at intervals of 10min, wherein the particle size of the particles is 30-10 meshes, argon is continuously introduced into the refining furnace at the flow rate of 6-7L/min, the mass ratio of the fly ash to the iron remover in the fly ash-iron remover sintered particles is 45:55, the total mass fraction of SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂ and CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the stacking density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm, the fly ash is high-calcium fly ash, the total mass of the introduced fly ash-iron remover sintered particles is 5% of the total mass of the silicon melt, and after powder spraying is completed, the silicon melt is fully slagging in a submerged arc furnace for 0.5 hours. As shown in FIG. 1, the powder spraying mode of the inert gas and the powder spraying particles in the step is a concentric circle powder spraying mode, the center of the concentric circle is a mixture of the inert gas and the powder spraying particles, and the outer circle of the concentric circle is the inert gas.

S5, taking silicon melt in the refining furnace for component detection, and obtaining Si 99.64%, fe <0.01%, al <0.01%, ca <0.01%, ba <0.01%, B <0.01% in the silicon melt, and obtaining 483kg of high-purity industrial silicon with purity higher than 99%.

Example 5

S1, adding 600kg of spherical silicon mud into an ore heating furnace to prepare silicon melt, heating, controlling the temperature of molten silicon to 1800 ℃, preserving heat for 30min, and detecting the components of the silicon melt to obtain silicon melt, wherein silicon 83.26%, al 0.84%, ca 0.15% and Ba 0.12% Fe 0.05%.

S2, 72kg of coal ash-slag former sintered body particles taking coal ash as a carrier are introduced into the submerged arc furnace in a powder spraying mode of 10kg/min for 1min each time and 20min each time, wherein the particle size is 60-20 meshes, argon is continuously introduced into the submerged arc furnace at the flow rate of 6-7L/min, the coal ash slag former is coal ash-slag former sintered body particles, the mass ratio of the coal ash to the slag former is 35:65, the mass fraction of the slag former is 20% SiO ₂、50％Al₂O₃,30％CaCO₃, the coal ash is SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂, the total mass fraction of CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the bulk density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm coal ash, the total mass of the introduced coal ash-slag former sintered body particles is 12% of the total mass of the silicon melt, and after the powder spraying is completed, the silicon melt is fully carried out in the submerged arc furnace for 2 hours. As shown in FIG. 1, the powder spraying mode of the inert gas and the powder spraying particles in the step is a concentric circle powder spraying mode, the center of the concentric circle is a mixture of the inert gas and the powder spraying particles, and the outer circle of the concentric circle is the inert gas.

S3, after the slag floating in the step S2 is removed, 522kg of high-temperature silicon melt with the temperature not lower than 1800 ℃ is slowly flowed into a refining furnace, the temperature in the refining furnace is kept at 1800-2200 ℃, and after standing for 30min, the silicon melt is subjected to component detection, and Si 97.94%, fe 0.01%, al <0.09% and Ca <0.02%.

S4, 42kg of fly ash serving as a carrier and fly ash-iron remover sintered body particles are introduced into a refining furnace in a powder spraying mode of spraying powder for 1min each time at intervals of 20min, wherein the particle size of the particles is 30-10 meshes, argon is continuously introduced into the refining furnace at the flow rate of 6-7L/min, the mass ratio of the fly ash to the iron remover in the fly ash-iron remover sintered body particles is 55:45, the total mass fraction of SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂ and CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the stacking density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm, the fly ash is high-calcium fly ash, and after powder spraying is finished, the silicon melt is fully slagging in a submerged arc furnace for 1 hour. As shown in FIG. 1, the powder spraying mode of the inert gas and the powder spraying particles in the step is a concentric circle powder spraying mode, the center of the concentric circle is a mixture of the inert gas and the powder spraying particles, and the outer circle of the concentric circle is the inert gas.

S5, taking silicon melt in the refining furnace for component detection, and obtaining Si 99.46%, fe <0.01%, al <0.01%, ca <0.01%, ba <0.01%, B <0.01% in the silicon melt, and discharging after detection qualification, thereby obtaining 480kg of high-purity industrial silicon with purity higher than 99%.

In the above embodiments 1-5, the preparation method of the sintered body particles of the fly ash-slag former in the step S2 comprises mixing 30-35 parts of fly ash and 65-70 parts of slag former together, adding water accounting for 20% -25% of the total mass of the fly ash and slag former, fully mixing the fly ash and binder accounting for 5% -15% of the total mass of the slag former, pelletizing on a pelletizer, performing heat preservation sintering at a high temperature of 1100-1200 ℃, crushing and sieving to obtain particles of 60-20 meshes after natural cooling, wherein the binder is water glass.

The preparation method of the fly ash-iron removing agent sintered body particles in the step S4 comprises the steps of mixing 45-55 parts of fly ash and 45-55 parts of iron removing agent together, adding water accounting for 20% -25% of the total mass of the fly ash and the iron removing agent, fully mixing the fly ash and a binder accounting for 5% -15% of the total mass of the iron removing agent, performing heat preservation sintering at a high temperature of 1100-1200 ℃ after pelletizing on a pelletizer, crushing and screening particles of 30-10 meshes after natural cooling, wherein the iron removing agent is CaF ₂,30～40％AlSn,20～30％Na₂SiF₆ accounting for 30-40% of the mass fraction, and the binder is water glass.

The preparation method of the fly ash-slag former sintered body particles in the embodiment 1 comprises the steps of mixing 30 parts of fly ash and 70 parts of slag former together, adding water accounting for 25% of the total mass of the fly ash and the slag former, fully mixing the fly ash and water glass accounting for 10% of the total mass of the slag former, pelletizing on a pelletizer, preserving heat for 30min at a high temperature of 1100-1200 ℃, sintering, naturally cooling, crushing and screening to obtain particles with 60-20 meshes, wherein the slag former comprises 30 parts of SiO ₂, 30 parts of Al ₂O₃, 20 parts of BaO and 20 parts of CaCO ₃.

The preparation method of the fly ash-iron removing agent sintered body particles comprises the steps of mixing 45 parts of fly ash and 55 parts of iron removing agent together, adding water accounting for 25% of the total mass of the fly ash and the iron removing agent, fully mixing the fly ash and water glass accounting for 10% of the total mass of the iron removing agent, performing pelleting on the mixture on a pelleting machine, performing heat preservation for 30min at a high temperature of 1100-1200 ℃, performing natural cooling, crushing and screening to obtain particles with 30-10 meshes, wherein the iron removing agent is CaF ₂,30％AlSn,30％Na₂SiF₆ with a mass fraction of 40%.

The preparation method of the fly ash-slag former sintered body particles in the embodiment 2 comprises the steps of mixing 35 parts of fly ash and 65 parts of slag former together, adding water accounting for 20% of the total mass of the fly ash and the slag former, fully mixing the fly ash and water glass accounting for 15% of the total mass of the slag former, granulating on a granulator, preserving heat for 45min at a high temperature of 1100-1200 ℃ for sintering, crushing and screening particles of 60-20 meshes after natural cooling, wherein the slag former comprises 60 parts of SiO2, 20 parts of Al ₂O₃ and 20 parts of CaCl ₂.

The preparation method of the fly ash-iron removing agent sintered body particles in the embodiment 2 comprises the steps of mixing 55 parts of fly ash and 45 parts of iron removing agent together, adding water accounting for 25% of the total mass of the fly ash and the iron removing agent, fully mixing the fly ash and water glass accounting for 10% of the total mass of the iron removing agent, granulating on a granulator, preserving heat for 45min at the high temperature of 1100-1200 ℃ for sintering, crushing and screening particles with 30-10 meshes after natural cooling, and taking 30% CaF ₂,40％AlSn,30％Na₂SiF₆ as the iron removing agent by mass fraction.

The preparation method of the fly ash-slag former sintered body particles in the embodiment 3 comprises the steps of mixing 35 parts of fly ash and 65 parts of slag former together, adding water accounting for 25% of the total mass of the fly ash and the slag former, fully mixing the fly ash and water glass accounting for 5% of the total mass of the slag former, granulating on a granulator, preserving heat for 30min at a high temperature of 1100-1200 ℃ for sintering, crushing and screening particles with 60-20 meshes after natural cooling, and obtaining 60 parts of SiO ₂ and 40 parts of Al ₂O₃ as slag former components.

The preparation method of the fly ash-iron removing agent sintered body particles in the embodiment 3 comprises the steps of mixing 50 parts of fly ash and 50 parts of iron removing agent together, adding water accounting for 25% of the total mass of the fly ash and the iron removing agent, fully mixing the fly ash and water glass accounting for 5% of the total mass of the iron removing agent, granulating on a granulator, preserving heat for 30min at the high temperature of 1100-1200 ℃ for sintering, crushing and screening particles with 30-10 meshes after natural cooling, and taking the iron removing agent which is CaF ₂,40％AlSn,20％Na₂SiF₆ with the mass fraction of 40%.

The preparation method of the fly ash-slag former sintered body particles in the embodiment 4 comprises the steps of mixing 30 parts of fly ash and 70 parts of slag former together, adding water accounting for 25% of the total mass of the fly ash and the slag former, fully mixing the fly ash and water glass accounting for 15% of the total mass of the slag former, granulating on a granulator, preserving heat for 30min at a high temperature of 1100-1200 ℃ for sintering, crushing and screening particles with 60-20 meshes after natural cooling, wherein the slag former comprises 40 parts of SiO ₂, 50 parts of Al ₂O₃ and 10 parts of CaCl ₂.

The preparation method of the fly ash-iron removing agent sintered body particles in the embodiment 4 comprises the steps of mixing 45 parts of fly ash and 55 parts of iron removing agent together, adding water accounting for 25% of the total mass of the fly ash and the iron removing agent, fully mixing the fly ash and water glass accounting for 15% of the total mass of the iron removing agent, granulating on a granulator, preserving heat for 35min at a high temperature of 1100-1200 ℃, sintering, naturally cooling, crushing and screening particles with 30-10 meshes, and taking the iron removing agent which is CaF ₂,40％AlSn,20％Na₂SiF₆ with a mass fraction of 40%.

The preparation method of the fly ash-slag former sintered body particles in the embodiment 5 comprises the steps of mixing 35 parts of fly ash and 65 parts of slag former together, adding water accounting for 25% of the total mass of the fly ash and the slag former, fully mixing the fly ash and water glass accounting for 15% of the total mass of the slag former, pelletizing on a pelletizer, preserving heat for 35min at a high temperature of 1100-1200 ℃, sintering, naturally cooling, crushing and screening particles with 60-20 meshes, wherein the slag former comprises 20 parts of SiO ₂, 50 parts of Al ₂O₃ and 30 parts of CaCO ₃.

The preparation method of the fly ash-iron removing agent sintered body particles in the embodiment 5 comprises the steps of mixing 55 parts of fly ash and 45 parts of iron removing agent together, adding water accounting for 25% of the total mass of the fly ash and the iron removing agent, fully mixing the fly ash and water glass accounting for 15% of the total mass of the iron removing agent, granulating on a granulator, preserving heat for 35min at a high temperature of 1100-1200 ℃, sintering, naturally cooling, crushing and screening particles with 30-10 meshes, wherein the iron removing agent comprises 35 parts of CaF ₂, 35 parts of AlSn and 30 parts of Na ₂SiF₆ by mass.

Comparative example 1

The comparative example differs from example 1 in that a one-step process was used to prepare high purity industrial silicon, as follows

S1, adding 600kg of silicon mud into an ore smelting furnace to prepare silicon melt, heating, controlling the temperature of molten silicon to 1800 ℃, preserving heat for 30min, and detecting the components of the silicon melt to obtain silicon melt, wherein the silicon melt contains 88.26%, 0.17% of Al, 0.23% of Ca, 0.12% of Ba, 0.85% of Fe and 0.08% of B.

S2, introducing 72kg of coal ash-slag former sintered body particles taking coal ash as a carrier into a submerged arc furnace in a powder spraying mode, wherein the particle size is 60-20 meshes, introducing 30kg of coal ash-iron remover sintered body particles taking coal ash as a carrier, wherein the particle size is 30-10 meshes, continuously introducing argon into the submerged arc furnace at a flow rate of 6-7L/min, wherein the coal ash slag former is coal ash-slag former sintered body particles, the mass ratio of the coal ash to the slag former is 30:70, the mass ratio of the slag former is 30% SiO ₂、25％Al₂O₃,20％BaO,25％CaCO₃, the mass ratio of the coal ash to the iron remover in the coal ash-iron remover sintered body particles is 45:55, the coal ash is SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂, the total mass ratio of CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the bulk density is less than or equal to 1.2g/cm ³, the stability is less than or the silicon melt is fully slagging coal ash in the submerged arc furnace for 1 hour.

S3, taking silicon melt in the refining furnace for component detection, and measuring 98.68% of Si, 0.41% of Fe, 0.01% of Al, 0.01% of Ca, 0.01% of Ba and 0.01% of B in the silicon melt to obtain 452kg of high-purity industrial silicon with the purity of 98.68.

Comparative example 2

This comparative example is different from example 1 in that the powder spraying is performed using a common nozzle, and the inert gas pipe and the powder spraying pipe are separated.

After the completion of refining, 97.35% of Si, 0.03% of Fe, 0.01% of Al and 0.01% of Ca were measured in the silicon melt.

Comparative example 3

The difference between this comparative example and example 1 is that the slag former used was free of fly ash carrier.

S2, introducing 72kg of slag forming agent into the submerged arc furnace in a powder spraying mode of 10kg/min of flow, 1min of powder spraying each time and 10min of powder spraying at intervals, wherein the grain size of the slag forming agent is 60-20 meshes, simultaneously continuously introducing argon into the submerged arc furnace at the flow of 6-7L/min, the mass fraction of the slag forming agent is 30% SiO ₂、30％Al₂O₃,20％BaO,20％CaCO₃, and fully slagging the silicon melt in the submerged arc furnace for 1 hour after the powder spraying is completed. As shown in FIG. 1, the powder spraying mode of the inert gas and the powder spraying particles in the step is a concentric circle powder spraying mode, the center of the concentric circle is a mixture of the inert gas and the powder spraying particles, and the outer circle of the concentric circle is the inert gas.

S4, introducing 30kg of iron remover particles into the refining furnace in a powder spraying mode of 10kg/min of flow, 1min of powder spraying each time and 10min of powder spraying at intervals, continuously introducing argon into the refining furnace at a flow of 6L-7L/min, and fully slagging the silicon melt in the submerged arc furnace for 0.5 hour after the powder spraying is completed. As shown in FIG. 1, the powder spraying mode of the inert gas and the powder spraying particles in the step is a concentric circle powder spraying mode, the center of the concentric circle is a mixture of the inert gas and the powder spraying particles, and the outer circle of the concentric circle is the inert gas.

S5, taking silicon melt in the refining furnace for component detection, and obtaining Si 99.35%, fe <0.01%, al <0.01%, ca <0.01%, ba <0.01%, B <0.01% in the silicon melt, and taking out the silicon melt after qualified detection to obtain 430kg of high-purity industrial silicon with purity higher than 99%.

Comparative example 4

This comparative example differs from example 1 in that no iron removal agent was used for the slag former.

Comparative example 5

This comparative example differs from example 1 in that the method of adding the slag former is a conventional direct pouring addition method.

S2, introducing 72kg of coal ash-slag former sintered body particles taking coal ash as a carrier into a submerged arc furnace, wherein the particle size is 60-20 meshes, simultaneously introducing argon into the submerged arc furnace continuously at the flow rate of 6-7L/min, the coal ash slag former is coal ash-slag former sintered body particles, the mass ratio of the coal ash to the slag former is 30:70, the mass fraction of the slag former is 30% SiO ₂、30％Al₂O₃,20％BaO,20％CaCO₃, the total mass fraction of the coal ash is SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂, the total mass fraction of CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the bulk density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm coal ash, the total mass of the introduced coal ash-slag former sintered body particles is 12% of the total mass of silicon melt, and the silicon melt is fully slag-formed in the submerged arc furnace for 1 hour.

S3, after the slag floating in the step S2 is removed, 510kg of high-temperature silicon melt with the temperature not lower than 1800 ℃ is slowly flowed into a refining furnace, the temperature in the refining furnace is kept at 1800-2200 ℃, and after standing for 30min, the silicon melt is subjected to component detection, and 96.42% of Si, 0.71% of Fe, 0.08% of Al, 0.03% of Ca, 0.01% of Ba and 0.01% of B are detected.

S4, introducing 30kg of fly ash-iron removing agent sintered body particles taking fly ash as a carrier into a refining furnace, wherein the particle size is 30-10 meshes, simultaneously continuously introducing argon into the refining furnace at a flow rate of 6-7L/min, wherein in the fly ash-iron removing agent sintered body particles, the mass ratio of the fly ash to the iron removing agent is 45:55, the total mass fraction of the fly ash is SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂, the total mass fraction of CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the bulk density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm of the fly ash, the total mass of the introduced fly ash-iron removing agent sintered body particles is 5% of the total mass of the silicon melt, and the silicon melt is fully slagging in an submerged arc furnace for 0.5 hours.

S5, taking silicon melt in the refining furnace for component detection, and obtaining 99.02% of Si, 0.02% of Fe, 0.03% of Al and 0.01% of Ca in the silicon melt, and discharging the silicon melt from the furnace after detection qualification, thereby obtaining 492kg of high-purity industrial silicon with purity higher than 99%.

Comparative example 6

This comparative example differs from example 1 in that the fly ash ratio is too high,

S1, adding 600kg of silicon mud into an ore smelting furnace to prepare silicon melt, heating, controlling the temperature of molten silicon to 1800 ℃, preserving heat for 30min, and detecting the components of the silicon melt to obtain silicon melt, wherein the silicon melt contains silicon 88.26%, al 0.17%, ca 0.15%, ba 0.12%, fe 0.85% and B0.08%.

S2, introducing 72kg of coal ash-slag former sintered body particles taking coal ash as a carrier into a submerged arc furnace in a powder spraying mode, wherein the particle size is 60-20 meshes, simultaneously introducing argon into the submerged arc furnace continuously at a flow rate of 6-7L/min, wherein the coal ash slag former is coal ash-slag former sintered body particles, the mass ratio of the coal ash to the slag former is 50:50, the mass fraction of the slag former is 30% SiO ₂、250％Al₂O₃,20％BaO,25％CaCO₃, the total mass fraction of the coal ash is SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂, the total mass fraction of the CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the stacking density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm coal ash, and the total mass of the introduced coal ash-slag former sintered body particles is 12% of the total mass of the silicon melt, and the silicon melt is fully slag-formed in the submerged arc furnace for 1 hour.

S3, removing slag floating in the step S2, slowly flowing 513kg of high-temperature silicon melt with the temperature not lower than 1800 ℃ into a refining furnace, keeping the temperature in the refining furnace at 1800-2200 ℃, and standing for 30min, and detecting components of the silicon melt, wherein Si 93.59%, fe 0.71%, al 0.08%, ca 0.03%, ba <0.01% and B <0.01%.

S4, through a powder spraying mode, 30kg of coal ash-iron removing agent sintered body particles taking coal ash as a carrier are introduced into a refining furnace, the particle size is 30-10 meshes, meanwhile, argon is continuously introduced into the refining furnace at the flow rate of 6-7L/min, the mass ratio of the coal ash to the iron removing agent in the coal ash-iron removing agent sintered body particles is 60:40, the coal ash is SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂, the total mass fraction of CaO is more than or equal to 80%, the density is less than or equal to 2.5g/cm ³, the stability is less than or equal to 5mm, and the silicon melt is fully slagging for 0.5 hours in an ore heating furnace.

S5, taking silicon melt in the refining furnace for component detection, and measuring 95.13% of Si, 0.51% of Fe, 0.05% of Al and 0.06% of Ca in the silicon melt to obtain 502kg of high-purity industrial silicon with the purity of 95.13%.

Comparative example 7

This comparative example differs from example 1 in that the fly ash ratio was too low

S2, 72kg of coal ash-slag former sintered body particles taking coal ash as a carrier are introduced into the submerged arc furnace in a powder spraying mode of 10kg/min for 1min each time and 10min each time, wherein the particle size is 60-20 meshes, argon is continuously introduced into the submerged arc furnace at the flow rate of 6-7L/min, the coal ash slag former is coal ash-slag former sintered body particles, the mass ratio of the coal ash to the slag former is 30:70, the mass fraction of the slag former is 30% SiO ₂、30％Al₂O₃,20％BaO,20％CaCO₃, the coal ash is SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂, the total mass fraction of CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the bulk density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm coal ash, the total mass of the introduced coal ash-slag former sintered body particles is 12% of the total mass of silicon melt, and after the powder spraying is completed, the silicon melt is fully slagging for 1 hour in the submerged arc furnace. As shown in FIG. 1, the powder spraying mode of the inert gas and the powder spraying particles in the step is a concentric circle powder spraying mode, the center of the concentric circle is a mixture of the inert gas and the powder spraying particles, and the outer circle of the concentric circle is the inert gas.

S3, after the slag floating in the step S2 is removed, 518kg of high-temperature silicon melt with the temperature not lower than 1800 ℃ is slowly flowed into a refining furnace, the temperature in the refining furnace is kept at 1800-2200 ℃, and after standing for 30min, the silicon melt is subjected to component detection, and Si 96.47%, fe 0.69%, al 0.11%, ca 0.04%, ba <0.01% and B <0.01% are detected.

S4, 30kg of fly ash-iron removing agent sintered body particles taking fly ash as a carrier are introduced into a refining furnace in a powder spraying mode of spraying powder for 1min each time at intervals of 10min, the particle size of the particles is 30-10 meshes, argon is continuously introduced into the refining furnace at the flow rate of 6-7L/min, the mass ratio of the fly ash to the iron removing agent in the fly ash-iron removing agent sintered body particles is 45:55, the total mass fraction of the fly ash is SiO ₂、Al₂O₃、FeO、Fe₂O₃、TiO₂, the CaO is more than or equal to 90%, the tap density is less than or equal to 3g/cm ³, the stacking density is less than or equal to 1.2g/cm ³, the stability is less than or equal to 5mm, the total mass of the introduced fly ash-iron removing agent sintered body particles is 5% of the total mass of silicon melt, and after powder spraying is completed, the silicon melt is fully slagging in a submerged arc furnace for 0.5 hours. As shown in FIG. 1, the powder spraying mode of the inert gas and the powder spraying particles in the step is a concentric circle powder spraying mode, the center of the concentric circle is a mixture of the inert gas and the powder spraying particles, and the outer circle of the concentric circle is the inert gas.

S5, taking silicon melt in the refining furnace for component detection, and measuring 98.34% of Si, 0.04% of Fe, 0.03% of Al and 0.01% of Ca in the silicon melt to obtain 511kg of high-purity industrial silicon with the purity of 98.34%.

Comparative example 8

This comparative example differs from example 1 in that the particle size is too high

S3, after the slag floating in the step S2 is removed, 544kg of high-temperature silicon melt with the temperature not lower than 1800 ℃ is slowly flowed into a refining furnace, the temperature in the refining furnace is kept at 1800-2200 ℃, and after standing for 30min, the silicon melt is subjected to component detection, and 96.43% of Si, 0.62% of Fe, 0.07% of Al, 0.04% of Ca, 0.01% of Ba and 0.01% of B are detected.

S5, taking silicon melt in the refining furnace for component detection, and obtaining 518kg of high-purity industrial silicon with the purity of 98.27% from 98.27% of Si, 0.02% of Fe, 0.020.01% of Al and 0.01% of Ca in the silicon melt.

Comparative example 9

The comparative example differs from the example in that the particle size is too small

S3, after slag floating in the step S2 is removed, 542kg of high-temperature silicon melt with the temperature not lower than 1800 ℃ is slowly flowed into a refining furnace, the temperature in the refining furnace is kept at 1800-2200 ℃, after standing for 30min, the silicon melt is subjected to component detection, and Si 97.86%, fe 0.58%, al 0.06%, ca 0.06%, ba <0.01% and B <0.01% are detected.

S5, taking silicon melt in the refining furnace for component detection, and obtaining the silicon melt with 98.93% of Si, 0.02% of Fe, 0.02% of Al and 0.01% of Ca, thereby obtaining 519kg of high-purity industrial silicon with 98.9% of purity.

Comparative example 10

The comparative example differs from example 1 in that the fly ash used was low calcium fly ash.

The silicon solution obtained in the step S2 contains 98.42% of Si, 0.63% of Fe, 0.07% of Al and 0.05% of Ca;

The silicon solution obtained in the step S4 contains 99.32% of Si, 0.01% of Fe, 0.01% of Al and 0.01% of Ca, and 510kg of high-purity industrial silicon with the purity of 99.32% is obtained.

Table 1 shows the industrial silicon composition obtained in each of the examples and comparative examples.

Table 1 table of industrial silicon composition obtained in each example

By comparing example 1 with comparative example 1, the method of removing silicon melt in the submerged arc furnace and the refining furnace of example 1, respectively, can significantly improve the purity of silicon melt. In the embodiment 1 of the application, most of Al, ca, B and other impurities are removed in an ore smelting furnace, and Fe and a small amount of Al, ca and the like impurities are further removed in a refining furnace, so that the purity of the silicon solution obtained in the embodiment 1 is higher.

By comparing the embodiment 1 with the comparison 2, the powder spraying pipe and the inert gas spraying pipe adopted in the embodiment 1 are arranged in a concentric-circle powder spraying mode, the center of the concentric circle is a mixture of inert gas and powder spraying particles, the outer circle of the concentric circle is inert gas, so that excessive oxygen is prevented from being introduced in the powder spraying process, silicon is oxidized, impurities such as Al, mg or Ca can be removed through vacuum directional solidification through the inert gas of the outer circle, and the silicon solution and a high-temperature melted slag former can be prevented from blocking the powder spraying pipe. In contrast, in comparative example 2, the common nozzle is used for powder spraying, the inert gas pipeline is separated from the powder spraying pipeline, and the nozzle is blocked in the powder spraying process, so that the actual powder spraying amount is reduced in a specific time, and the deslagging effect and the yield are affected.

By comparing the embodiment 1 with the comparative example 3, the embodiment 1 adopts the sintered body particles of the deslagging agent taking the fly ash as the carrier to deslagging, fully utilizes the porous form of the fly ash structure, and adheres and gathers the formed oxides together at high temperature after the adsorption, thereby improving deslagging efficiency. The deslagging agent in the comparative example 3 does not adopt fly ash, so that more deslagging agent is needed, and impurities in the silicon melt and slag cannot be quickly focused together after forming slag because the deslagging agent is a powder device, so that the deslagging efficiency is low on one hand, the slag layer is thicker on the other hand, more silicon is attached to the slag layer, and the yield of high-purity silicon is reduced.

By comparing example 1 with comparative example 4, example 1 added iron-removing agent particles using fly ash as carrier, iron-containing intermetallic compound was produced by using iron-removing agent and iron in sinter at high temperature and accumulated on fly ash melt, and the remaining substances such as Al, ca and the like in silicon melt were also focused together under the action of fly ash and floated on the upper layer of silicon melt. The method can remove impurities in the silicon melt, and can obtain high-purity industrial silicon with purity higher than 99%.

By comparing the example 1 with the comparative example 5, the example 1 adopts the powder spraying mode to add the powder coal ash-slag former sintered body particles into the silicon melt, and the powder spraying mode can efficiently disperse the powder coal ash-slag former sintered body particles into the silicon melt, thereby realizing the rapid slag removal of the silicon melt in each part of the furnace and improving the slag forming efficiency of impurities in the silicon melt. In contrast, in comparative example 5, the slag former is added into the silicon melt by a conventional direct pouring method, which results in uneven distribution of the slag former in the silicon melt, poor consistency of the product, and low impurity removal efficiency.

By comparing example 1 with comparative example 6, in the fly ash-slag former sintered body particles, the ratio of the fly ash is too high, resulting in a relatively low ratio of the effective components of the slag former, which is disadvantageous for removing impurities in the silicon melt.

By comparing example 1 with comparative example 7, in comparative example 7, the ratio of the fly ash-slag former sintered body particles to the fly ash is too low, so that impurities and slag formed by the impurities and the slag former cannot be gathered together efficiently, the slag forming efficiency is low, and the purity of the obtained silicon melt cannot meet the requirement under the same conditions.

By comparing example 1 with comparative example 8, the comparative example 8 has too high particle size, which results in great difficulty in powder spraying, and insufficient power of the powder spraying particles in the silicon melt, which results in lower dispersion efficiency of the powder spraying particles in the silicon melt.

By comparing example 1 with comparative example 9, the comparative example 9 has too small particle size, which results in too small volume of slag, which is unfavorable for focusing slag, and reduces the efficiency of removing impurities.

By comparing example 1 with comparative example 10, comparative example 10 uses low-calcium fly ash, which has relatively low CaO content and relatively low slag removal efficiency with respect to high-calcium fly ash.

It should be noted that the above-mentioned embodiments are merely for illustrating the technical solution of the present invention, and not for limiting the same, and although the present invention has been described in detail with reference to the above-mentioned embodiments, it should be understood by those skilled in the art that the technical solution described in the above-mentioned embodiments may be modified or some or all of the technical features may be equivalently replaced, and these modifications or substitutions do not deviate from the essence of the corresponding technical solution from the scope of the technical solution of the embodiment of the present invention.

Claims

1. A method for preparing high-purity silicon by cutting crystalline silicon waste from solar cells, for preparing high-purity silicon with a silicon content of ≥99%, characterized in that the steps are as follows:

S1, adding silicon mud into a submerged arc furnace to prepare silicon melt, maintaining the temperature of the silicon melt not less than 1800° C., and performing component detection on the silicon melt after the silicon mud is fully melted into the silicon melt;

S2, by means of powder spraying, a fly ash slag-forming agent with fly ash as a carrier is introduced into the submerged arc furnace, and an inert gas is continuously introduced into the submerged arc furnace, and the fly ash slag-forming agent is a fly ash-slag-forming agent sintered body particle, and the mass ratio of fly ash to slag-forming agent in the fly ash-slag-forming agent sintered body particle is 30-35:65-70, and the total mass of the introduced fly ash-slag-forming agent sintered body particle is 10%-15% of the total mass of the silicon melt; the powder The preparation method of fly ash-slag-forming agent sintered body particles is as follows: 30-35 parts of fly ash and 65-70 parts of slag-forming agent are mixed together, and 20%-25% of water by weight of the total weight of the fly ash and the slag-forming agent and 5%-15% of a binder by weight of the total weight of the fly ash and the slag-forming agent are added, after fully mixing, pelletizing on a pelletizing machine, sintering at a high temperature of 1100° C. to 1200° C., crushing and screening to obtain 60-mesh to 20-mesh particles after natural cooling; the slag-forming agent is any one of SiO ₂ , Al ₂ O ₃ , CaCO ₃ , CaO or a combination thereof;

S3, transferring the high-temperature silicon melt in the ore-fired furnace to the refining furnace, maintaining the temperature in the refining furnace at 1800°C to 2200°C, and performing component detection on the silicon melt;

S4, by means of powder spraying, fly ash-ironing agent sintered body particles with fly ash as carrier are introduced into a refining furnace, and at the same time, inert gas is introduced into the refining furnace, and the fly ash-ironing agent sintered body particles are fully smelted, wherein the mass ratio of fly ash to iron removing agent in the fly ash-ironing agent sintered body particles is 45-55:45-55; the total mass of the fly ash-ironing agent sintered body particles introduced is 5%-10% of the total mass of silicon melt; the preparation method of the fly ash-ironing agent sintered body particles The method comprises the following steps: 45-55 parts of fly ash and 45-55 parts of an iron remover are mixed together, and water accounting for 20%-25% of the total weight of the fly ash and the iron remover, and a binder accounting for 5%-15% of the total weight of the fly ash and the iron remover are added, and the mixture is fully mixed and pelletized on a pelletizer, and then the mixture is heat-insulated and sintered at a high temperature of 1100° C. to 1200° C., and then naturally cooled and crushed to obtain particles of 30 meshes to 10 meshes; the iron remover comprises 30-40wt% CaF ₂ , 30-40wt% AlSn, and 20-30wt% Na ₂ SiF ₆ ;

S5, taking the silicon melt in the refining furnace for component detection, and when the silicon content is ≥99%, the prepared high-purity silicon is taken out of the furnace;

The total mass fraction of SiO ₂ , Al ₂ O ₃ , FeO, Fe ₂ O ₃ , TiO ₂ and CaO in the fly ash is ≥90%, the tap density is ≤3g/cm ³ , the bulk density is ≤1.2g/cm ³ , and the stability is ≤5mm;

The spray pipe used in the inert gas and powder spraying process comprises a powder spraying pipeline (1) and an inert gas pipeline (2) arranged outside the powder spraying pipeline (1) and used for introducing the inert gas.

2. The method for preparing high-purity silicon by cutting crystalline silicon waste from solar cells as claimed in claim 1, characterized in that the particle size of the fly ash-slag-forming agent sintered body particles in step S2 is 60 mesh to 20 mesh.

3. The method for preparing high-purity silicon by cutting crystalline silicon waste from solar cells as claimed in claim 1, characterized in that the particle size of the fly ash-iron remover sintered body particles in step S3 is 30 mesh to 10 mesh.

4. The method for preparing high-purity silicon by cutting crystalline silicon waste from solar cells as claimed in claim 1, characterized in that the powder spraying flow rate is 10kg/min~30kg/min, and the powder spraying method is intermittent powder spraying.

5. The method for preparing high-purity silicon by cutting crystalline silicon waste from solar cells as claimed in claim 1, characterized in that the fly ash is high-calcium fly ash.