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

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

Technical Field

[0001] The invention belongs to the technical field of high-purity industrial silicon preparation, and relates to a method for preparing high-purity industrial silicon by cutting silicon waste, and specifically to a method for preparing high-purity silicon by cutting crystalline silicon waste from solar cells. Background Art

[0002] Industrial silicon is also known as metallic silicon or crystalline silicon. The traditional preparation method is to smelt silica and carbonaceous reducing agent in a submerged arc furnace through high-temperature reaction. The main component silicon element content is about 98%, and the remaining impurities are iron, aluminum, calcium, etc. Its properties are similar to those of germanium, lead, and tin, and it can be used in semiconductors, etc.

[0003] According to the requirements of trace elements for specific uses, it is also divided into chemical silicon and metallurgical silicon. Industrial silicon is divided into 8 grades according to the national standard (GBT2881-2014). The grades are expressed in the form of a combination of the silicon element symbol and a 4-digit number. Quasi-metallic silicon can be divided into different grades such as 5530#, 5210#, 4410#, 4210#, 4110#, 3303#, 2202#, and 1101#. Among them, Si4210 has the largest demand, and Si5530 is more widely used. In particular, Si5520~Si1101 requires a silicon purity of not less than 99.20 to not less than 99.79%. The traditional smelting method consumes very high power and is difficult to smelt.

[0004] In the process of using silicon raw materials to prepare crystalline silicon solar cell materials, the silicon ingot needs to be cut into silicon slices. During the cutting process, nearly half of the silicon will enter the cutting fluid in the form of ultrafine powder to form a large amount of cutting waste, resulting in a waste of silicon resources and environmental pollution. When diamonds are cutting silicon rods or silicon ingots, in order to ensure processing accuracy and improve the surface quality of silicon wafers, auxiliary cutting fluid is required to lubricate and flush the cutting surface to form silicon mud. The silicon mud includes silicon powder generated by diamonds in the process of cutting silicon rods or silicon ingots, diamond wire wear and tear containing metal impurities during diamond cutting, flocculants and coolants during the cutting process. The average size of silicon powder is 1-5μm. The cutting waste silicon mud is composed of about 90% silicon powder and a small amount of Fe, Al, Ca, and impurities such as water, diethylene glycol or ethylene glycol or polyethylene glycol.

[0005] Since the silicon powder in "silicon mud" is small in size and contains moisture and non-silicon impurities, it is difficult to recycle and reuse. It is usually used as a refractory material by drying and dehydration, or used as a raw material for steel smelting after simple sintering, resulting in a large amount of silicon mud that cannot be effectively recycled and applied to polysilicon processing. Since silicon mud is cheap and cannot be effectively reused in silicon wafer processing, it limits the production cost of polysilicon and causes energy waste.

[0006] Chinese patent document CN115504476A discloses a method for producing high-purity silicon using recycled silicon mud. The method includes adding a prepared mixed solution to the silicon mud, stirring the reaction and filtering to obtain a mixture A; adding the mixture A to a hydrofluoric acid solution for pickling, washing and drying with high-purity water after pickling to obtain silicon powder; adding the silicon powder to an electron beam vacuum furnace for smelting and purification to obtain a silicon ingot; sawing the surface of the silicon ingot, and removing the surface of the silicon ingot to obtain a high-purity silicon ingot. According to testing, the purity of the high-purity silicon ingot can reach 99.9999%, reaching the electronic grade, which far exceeds the purity of the silicon ingot obtained by melting and recovering silicon mud in the prior art through medium-frequency induction furnaces, arc furnaces or resistance furnaces. Although the purity of the high-purity silicon obtained by this method reaches the electronic grade, this method uses smelting and purification in an electron beam vacuum furnace, which has high requirements for equipment and high energy consumption.

[0007] Chinese patent CN 111498852 A discloses a device for producing high-purity industrial silicon and a preparation method thereof. The patent adopts a common slag-making agent to remove impurities. The content of the slag-making agent is about 50% of the total mass of the silicon solution, and the consumption of the slag-making agent is relatively large. In addition, the composition of the original silicon solution in the patent document is not clear. Therefore, the purity of the high-purity silicon recorded in the patent document cannot accurately evaluate the technical effect of the method.

[0008] Chinese patent document CN114890428A discloses a ternary slag-forming agent and its impurity removal method for industrial silicon refining outside the furnace. The ternary slag-forming agent of the patent is SiO2-Al 2 O 3 -ZnO, whose melting point is 1305℃~1500℃. The impurity removal method is to pass compressed gas into the ladle, add the ternary slag-forming agent to the industrial silicon melt for reaction for 30~60min, and the impurities in the silicon solution react with the ternary slag-forming agent to form compounds that volatilize and overflow the industrial silicon melt. However, the patent records that the impurity iron in the industrial silicon can react with the free zinc in the slag-forming agent. However, according to the common sense in the field, the ZnO in the slag-forming agent cannot be reduced to Zn in the absence of a reducing agent. Even if the ternary slag-forming agent contains free zinc, since the boiling point of zinc is 907℃ and the melting point of Fe is as high as 1500℃, the reaction of the impurity iron recorded in the patent with the free zinc in the slag-forming agent cannot occur.

[0009] In summary, the main technical difficulty in preparing crystalline silicon cutting waste into high-purity industrial silicon with a purity of more than 99% lies in reducing the content of impurities such as Fe, Al, and Ca in silicon mud. The existing technology uses the method of using solar cell cutting crystalline silicon waste to prepare high-purity silicon. The problems include: ① using electron beam vacuum furnace for smelting and purification to obtain silicon ingots, which is equivalent to the normal method of preparing electronic grade high-purity silicon, and the energy consumption is high; ② using ordinary slag-making agents to remove impurities in silicon mud, but the consumption of slag-making agents is large. ③ Using composite slag-making agents, but the slag-making efficiency is low. ④ It is relatively difficult to remove iron impurities in silicon solution through slag-making agents. Summary of the invention

[0010] In order to solve the technical problems existing in the prior art, the present application provides a method for preparing high-purity silicon by using crystalline silicon waste cut from solar cells, and adopts a smelting method to prepare high-purity industrial silicon. In the smelting process, the present application first uses a mineral arc furnace for smelting. After removing impurities, the molten liquid is transferred to a refining furnace for secondary refining and removal of impurity elements. A small amount of electric energy in the refining furnace is converted into heat energy to maintain a constant temperature, and chemical and physical purification measures are taken to finally accurately produce high-purity industrial silicon with the required indicators, and achieve the effects of energy saving and consumption reduction, and comprehensive resource utilization.

[0011] The present invention discloses a method for preparing high-purity silicon by cutting crystalline silicon waste from solar cells as follows:

[0012] A method for preparing high-purity silicon by using crystalline silicon waste cut from solar cells, which is used to prepare high-purity silicon with a silicon content of ≥99%, and the steps are as follows:

[0013] S1, placing silicon mud in a submerged arc furnace to prepare silicon melt, maintaining the temperature of the silicon melt at not less than 1800° C., and performing component detection on the silicon melt after the silicon mud is fully melted into the silicon melt;

[0014] S2, introducing a fly ash slag-forming agent with fly ash as a carrier into the submerged arc furnace by means of powder spraying, and continuously introducing an inert gas into the submerged arc furnace at the same time, and fully smelting the fly ash slag-forming agent, wherein the fly ash slag-forming agent is fly ash-slag-forming agent sintered body particles, and the mass ratio of fly ash to slag-forming agent in the fly ash-slag-forming agent sintered body particles is 30-35:65-70, and the total mass of the introduced fly ash-slag-forming agent sintered body particles is 10%-15% of the total mass of the silicon melt.

[0015] S3, slowly flowing the high-temperature silicon melt in the ore-fired furnace into the refining furnace, maintaining the temperature in the refining furnace at 1800° C. to 2200° C., and performing component detection on the silicon melt;

[0016] S4, fly ash-ironing agent sintered body particles with fly ash as carrier are introduced into the refining furnace by powder spraying, and at the same time, inert gas is introduced into the refining furnace and fully smelted, the mass ratio of fly ash to iron remover 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% to 10% of the total mass of the silicon melt.

[0017] S5, taking the silicon melt in the refining furnace for component detection, and taking the prepared high-purity silicon out of the furnace after reaching a predetermined composition.

[0018] In the present application, in step S1, the process of heating silicon mud in a submerged arc furnace to form a melt can gradually volatilize and remove water, flocculants such as diethylene glycol or ethylene glycol or polyethylene glycol, and coolant impurities mixed in the silicon mud. In the process of silicon melting, impurities such as Fe, Al, and Ca mixed in the silicon mud are uniformly dissolved in the silicon melt, which facilitates the reaction of impurities such as Fe, Al, and Ca with slag-forming agents to form oxides.

[0019] The temperature of the silicon melt is maintained at not less than 1800°C and kept warm for more than 30 minutes, so that the silicon mud is fully melted into the melt and the impurities in the silicon mud are dispersed in the silicon melt. Then, through step S2, a slag-forming agent with fly ash as a carrier is added to the silicon melt by means of powder spraying, and an inert gas is continuously introduced into the silicon melt to prevent oxygen from entering the silicon melt and generating silicon oxides. Under the action of the slag-forming agent, the main impurities such as Al and Ca in the silicon melt form low-density oxides and float to the surface of the silicon melt.

[0020] After the main impurities such as Al and Ca in the silicon melt are removed in step S2, the main impurity in the silicon melt is Fe. However, it is difficult to remove Fe and Fe oxides by conventional slag-making agents. Therefore, in step S3, the silicon melt after the main impurities such as Al and Ca are removed is transferred to the refining furnace, and the temperature in the refining furnace is kept higher than 1800°C and lower than 2200°C.

[0021] After the silicon melt is left to stand, fly ash-iron remover sinter is sprayed into the silicon melt by means of powder spraying.

[0022] The composition of the iron remover is 30-40wt% CaF 2 , 30~40wt%AlSn, 20~30wt%Na 2 SiF 6 .

[0023] The iron remover in the sintered material reacts with iron at high temperature to generate iron-containing metal compounds, which are gathered on the fly ash melt. The remaining Al, Ca and other substances in the silicon melt are also focused together under the action of the fly ash and float on the upper layer of the silicon melt.

[0024] The present invention can remove impurities in silicon melt and obtain high-purity industrial silicon with a purity higher than 99%.

[0025] In order to improve the slag-making efficiency, the particle size of the fly ash-slag-making agent sintered body in step S2 is 60 mesh to 20 mesh.

[0026] In order to improve the efficiency of forming the iron-aluminum alloy, the particle size of the fly ash-iron remover sintered body in step S3 is 30 mesh to 10 mesh.

[0027] The preparation method of the fly ash-slag-forming agent sintered body particles in step S2 is: 30-35 parts of fly ash and 65-70 parts of slag-forming agent are mixed together and 20%-25% of water which accounts for the total mass of the fly ash and the slag-forming agent is added, and 5%-15% of a binder which accounts for the total mass of the fly ash and the slag-forming agent is fully mixed, and after being pelletized on a pelletizing machine, the mixture is heat-insulated and sintered at a high temperature of 1100°C to 1200°C, and after natural cooling, the particles are crushed and sieved to obtain particles of 60 mesh to 20 mesh, and the binder is water glass.

[0028] The main component of fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , CaO, etc. account for about 90% of the total amount. Its composition is the same as that of the slag-making agent, and its porosity is generally 60% to 75%. Fly ash has a porous structure and its specific surface area is generally 2500 to 5000m 2 / g, has strong adsorption capacity, and fly ash is composed of many particles with different structures and forms. The particle size of a single fly ash particle is about 25-300μm, and the tap density of fly ash is 2-3g / cm 3 , bulk density is 0.6~1.2g / cm 3 This application makes full use of the above characteristics of fly ash, sintering fly ash and slag-forming agent into a sintered body slag-forming agent. After adding silicon melt, the impurities in the silicon melt can be adsorbed around the sintered body at the early stage. As the reaction proceeds, the impurities can be oxidized into oxides by the slag-forming agent, and the new oxides formed are adhered around the slag-forming body, gathered together and floated above the silicon melt, thereby completing the removal of impurities. This application makes full use of the porous structure of fly ash, adsorbs the formed oxides, and gathers them together by using the adhesion of the oxides at high temperature, thereby improving the slag removal efficiency.

[0029] Further, the preparation method of the fly ash-ironing agent sintered body particles in step S4 is as follows: 45-55 parts of fly ash and 45-55 parts of ironing agent are mixed together and 20%-25% of the total mass of the fly ash and ironing agent is added. After the fly ash and 5%-15% of the total mass of the binder are fully mixed, the fly ash and ironing agent are pelletized on a pelletizer, and then the pellets are sintered at a high temperature of 1100°C to 1200°C. After natural cooling, the pellets are crushed and sieved to obtain 30-10 mesh particles. The ironing agent is 30-40% CaF 2 , 30~40%AlSn, 20~30%Na 2 SiF 6 , the binder is water glass.

[0030] Impurities in the silicon melt can be further removed through the fly ash-ironing agent sintered particles, and an iron-zinc alloy melt is formed, which adheres to the fly ash melt and finally floats on the upper layer of the silicon melt, completing the removal of Fe impurities.

[0031] Furthermore, the slag-forming agent is SiO 2 、Al 2 O 3 , CaCl, CaCO 3 , CaO or a combination of any one of them.

[0032] Furthermore, the powder spraying flow rate of the powder spraying pipe is 10kg / min to 30kg / min, and the powder spraying method is interval powder spraying, such as powder spraying at least once every 10 minutes.

[0033] The inert gas powder spraying has a powder spraying pressure of 1Mpa to 5Mpa.

[0034] Furthermore, the spray pipe used in the inert gas and powder spraying process includes a powder spraying pipeline and an inert gas pipeline surrounding the inert gas arranged outside the powder spraying pipeline. The powder spraying method of the inert gas and the powder is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the outer surface, and the outer circle of the concentric circle is the inert gas.

[0035] Furthermore, when the component detection in step S5 does not reach the predetermined component, a fly ash slag-forming agent with fly ash as a carrier is introduced into the refining furnace by means of powder spraying, and an inert gas is continuously introduced into the electric arc furnace and fully smelted. The fly ash slag-forming agent is fly ash-slag-forming agent sintered particles, and / or fly ash-deironing agent sintered particles with fly ash as a carrier are introduced into the refining furnace by means of powder spraying, and an inert gas is continuously introduced into the refining furnace.

[0036] The present invention adopts a powder spraying method to introduce the slag remover into the silicon melt. The powder introduced into the silicon melt quickly disperses, so that the slag remover can be mixed with the impurities in the silicon melt. During the mixing process, SiO 2 、Al 2 O 3 It can react with Al, Ca and other impurities in the silicon melt to generate Al 2 O 3 , CaO and other oxide bodies, and concentrate together to eventually form a slag layer floating on the surface.

[0037] The powder spraying method of concentric circles is used, with the center of the concentric circles being a mixture of inert gas and the outer circle being an inert gas. This can prevent the introduction of too much oxygen during the powder spraying process and pass the inert gas in the outer circle. On the one hand, vacuum directional solidification can be achieved to remove impurities such as Al, Mg or Ca, and on the other hand, it can prevent the powder spraying pipeline from being blocked.

[0038] The SiO in fly ash 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤5mm, and the fly ash is high calcium fly ash.

[0039] Furthermore, the fly ash is high-calcium fly ash.

[0040] The beneficial effects of this application are:

[0041] 1. The main component of fly ash is Al 2 O 3 、SiO 2 , CaO, etc. account for about 90% of the total amount. Its composition is the same as that of the slag-making agent, and its porosity is generally 60% to 75%. Fly ash has a porous structure and its specific surface area is generally 2500 to 5000m 2 / g, has strong adsorption capacity, and fly ash is composed of many particles with different structures and forms. The particle size of a single fly ash particle is about 25-300μm, and the tap density of fly ash is 2-3g / cm 3 , bulk density is 0.6~1.2g / cm 3The present application makes full use of the above-mentioned characteristics of fly ash, and sintering the fly ash and slag-forming agent into a sintered body slag-forming agent. After adding the silicon melt, the impurities in the silicon melt can be adsorbed around the sintered body at the early stage. As the temperature reaction proceeds, the impurities can be oxidized into oxides by the slag-forming agent, and the formed oxides are adhered around the slag-forming body. The slag-forming body gathers together and floats above the silicon melt, thereby completing the removal of impurities. The present application makes full use of the porous structure of fly ash, gathers the formed oxides together by adhesion, and improves the slag removal efficiency.

[0042] 2. This application removes impurities from the silicon melt twice, keeps the temperature of the silicon melt not less than 1800°C, and keeps it warm for more than 30 minutes, so that the silicon mud is fully melted into the melt, and the impurities in the silicon mud are dispersed in the silicon melt, and then, through step S2, a slag-making agent with fly ash as a carrier is added to the silicon melt by means of powder spraying, and an inert gas is continuously introduced into the silicon melt to prevent oxygen from entering the silicon melt and generating silicon oxide. Under the action of the slag-making agent, the main impurities such as Al and Ca in the silicon melt form low-density oxides and float to the surface of the silicon melt. After removing the main impurities such as Al and Ca in the silicon melt through step S2, the main impurity in the silicon melt is Fe. However, it is difficult to oxidize Fe through conventional slag-making agents. To this end, through step S3, the silicon melt after removing the main impurities such as Al and Ca is slowly flowed into the refining furnace, and the temperature in the refining furnace is kept higher than 1800°C and lower than 2200°C. After the silicon melt is left to stand, fly ash-ironing agent sinter is sprayed into the silicon melt by means of powder spraying, and the ironing agent in the sinter reacts with iron at high temperature to generate iron-containing metal compounds, which are gathered on the fly ash melt, and the remaining Al, Ca and other substances in the silicon melt are also focused together under the action of the fly ash and float on the upper layer of the silicon melt. The present application can remove impurities in the silicon melt and obtain high-purity industrial silicon with a purity higher than 99%.

[0043] 3. The present application adopts a powder spraying method to introduce the slag remover into the silicon melt. The powder introduced into the silicon melt quickly disperses, so that the slag remover can be mixed with the impurities in the silicon melt. During the mixing process, SiO 2 、Al 2 O 3 It can react with Al, Ca and other impurities in the silicon melt to generate Al 2 O 3, CaO and other oxide bodies, and finally form a slag layer floating on the surface. The concentric circle powder spraying method is used, the center of the concentric circle is a mixture of inert gas and cover, and the outer circle of the concentric circle is inert gas, which can prevent the introduction of too much oxygen during the powder spraying process to oxidize silicon. Through the outer circle inert gas, on the one hand, vacuum directional solidification can be achieved to remove impurities such as Al, Mg or Ca, and on the other hand, it can prevent the silicon solution from clogging the powder spraying pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic diagram of the powder spraying tube structure for this application;

[0045] In the figure, 1 is a powder spraying pipeline, 2 is an inert gas pipeline, and the arrows in the figure indicate the powder spraying direction or the inert gas direction. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0047] Example 1

[0048] A method for preparing high-purity silicon by using crystalline silicon waste cut from solar cells, which is used to prepare industrial silicon with a purity higher than 99%, comprises the following steps:

[0049] S1, adding 600kg of spherical silicon mud into a mineral arc furnace to prepare silicon melt, heating, and controlling the temperature of the silicon melt to reach 1800°C, and keeping it warm for 30 minutes, and detecting the composition of the silicon melt to obtain 88.26% silicon, 0.17% Al, 0.23% Ca, 0.12% Ba, 0.85% Fe, and 0.08% B.

[0050] S2, by a powder spraying method with a flow rate of 10kg / min, each powder spraying lasts for 1min, and the powder spraying interval is 10min, 72kg of fly ash-slag-forming agent sintered body particles with fly ash as a carrier are introduced into the submerged arc furnace, the particle size of the particles is 60 mesh to 20 mesh, and argon gas is continuously introduced into the submerged arc furnace at a flow rate of 6L to 7L / min, the fly ash slag-forming agent is fly ash-slag-forming agent sintered body particles, the mass ratio of the fly ash to the slag-forming agent is 30:70, and the mass fraction of the slag-forming agent is 30% SiO 2 、30%Al 2 O 3 , 20%BaO, 20%CaCO 3 , the fly ash is SiO 2、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the fly ash is high calcium fly ash, the total mass of the fly ash-slag-making agent sintered body particles introduced is 12% of the total mass of the silicon melt, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore-fired furnace for 1 hour. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method. The inert gas and the spray pipe used in the powder spraying process include a powder spraying pipeline 1, an inert gas pipeline 2 surrounding the inert gas arranged on the outside of the powder spraying pipeline 1, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0051] S3, after removing the floating slag in step S2, 520 kg of high-temperature silicon melt with a temperature not lower than 1800°C is slowly flowed into the refining furnace, and the temperature in the refining furnace is maintained at 1800°C ~ 2200°C. After standing for 30 minutes, the silicon melt is subjected to component detection, and the measured content is Si 98.52%, Fe 0.63%, Al 0.06%, Ca 0.03%, Ba<0.01%, and B<0.01%.

[0052] S4 adopts a powder spraying method with a flow rate of 10kg / min, each powder spraying lasts for 1min, and the powder spraying interval is 10min. 30kg of fly ash-removing agent sintered body particles with fly ash as carrier are introduced into the refining furnace. The particle size of the particles is 30 mesh to 10 mesh. At the same time, argon gas is continuously introduced into the refining furnace at a flow rate of 6L to 7L / min. In the fly ash-removing agent sintered body particles, the mass ratio of fly ash to iron remover is 45:55. The fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the fly ash is high calcium fly ash, the total mass of the fly ash-ironing agent sintered body particles introduced is 5% of the total mass of the silicon melt, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore furnace for 0.5 hours. Figure 1The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0053] S5, take the silicon melt in the refining furnace for component detection, and measure the silicon melt, Si 99.37%, Fe<0.01%, Al<0.01%, Ca<0.01%, Ba<0.01%, B<0.01%, and the silicon melt passes the test and is discharged from the furnace, obtaining 513kg of high-purity industrial silicon with a purity higher than 99%.

[0054] Example 2

[0055] A method for preparing high-purity silicon by using crystalline silicon waste cut from solar cells, which is used to prepare industrial silicon with a purity higher than 99%, comprises the following steps:

[0056] S1, adding 600kg of spherical silicon mud into a mineral arc furnace to prepare silicon melt, heating, and controlling the temperature of the silicon melt to reach 1800°C, and keeping it warm for 30 minutes, and detecting the composition of the silicon melt to obtain 85.36% silicon, 0.23% Al, 0.86% Ca, 0.12% Ba, 0.37% Fe, and 0.03% B.

[0057] S2, by a powder spraying method with a flow rate of 20kg / min, each powder spraying lasts for 1min, and the powder spraying interval is 20min, 90kg of fly ash-slag-forming agent sintered body particles with fly ash as a carrier are introduced into the submerged arc furnace, the particle size of the particles is 60 mesh to 20 mesh, and argon gas is continuously introduced into the submerged arc furnace at a flow rate of 6L to 7L / min, the fly ash slag-forming agent is fly ash-slag-forming agent sintered body particles, the mass ratio of the fly ash to the slag-forming agent is 35:65, and the mass fraction of the slag-forming agent is 60% SiO 2 、20%Al 2 O 3 , 20% CaCl 2 , the fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the fly ash is high calcium fly ash, the total mass of the fly ash-slag-forming agent sintered body particles introduced is 15% of the total mass of the silicon melt, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore-fired furnace for 1.5 hours. Figure 1The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0058] S3, after removing the floating slag in step S2, 510 kg of high-temperature silicon melt with a temperature not lower than 1800° C. is slowly flowed into the refining furnace, and the temperature in the refining furnace is maintained at 1800° C. to 2200° C. After standing for 30 minutes, the silicon melt is subjected to a composition test, and the measured Si content is 98.23%, Fe 0.34%, Al 0.06%, and Ca 0.03%.

[0059] S4 adopts a powder spraying method with a flow rate of 30kg / min, each powder spraying is 30s, and the interval of powder spraying is 10min. 60kg of fly ash-removing agent sintered body particles with fly ash as carrier are introduced into the refining furnace. The particle size of the particles is 30 mesh to 10 mesh. At the same time, argon gas is continuously introduced into the refining furnace at a flow rate of 6L to 7L / min. In the fly ash-removing agent sintered body particles, the mass ratio of fly ash to iron remover is 55:45. The fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the fly ash is high calcium fly ash, the total mass of the fly ash-ironing agent sintered body particles introduced is 5% of the total mass of the silicon melt, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore-fired furnace for 1 hour. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0060] S5, take the silicon melt in the refining furnace for component detection, and measure the silicon melt, Si 99.56%, Fe<0.01%, Al<0.01%, Ca<0.01%, Ba<0.01%, B<0.01%, and the silicon melt passes the test and is discharged from the furnace, obtaining 473kg of high-purity industrial silicon with a purity higher than 99%.

[0061] Example 3

[0062] A method for preparing high-purity silicon by using crystalline silicon waste cut from solar cells, which is used to prepare industrial silicon with a purity higher than 99%, comprises the following steps:

[0063] S1, adding 600kg of spherical silicon mud into a mineral arc furnace to prepare silicon melt, heating, and controlling the temperature of the silicon melt to reach 1800°C, and keeping it warm for 30 minutes, and detecting the composition of the silicon melt to obtain 88.37% silicon, 0.46% Al, 0.35% Ca, 0.12% Ba and 0.42% Fe.

[0064] S2, by a powder spraying method with a flow rate of 30kg / min, each powder spraying lasts 0.5min, and the powder spraying interval is 5min, 60kg of fly ash-slag-forming agent sintered body particles with fly ash as a carrier are introduced into the submerged arc furnace, the particle size of the particles is 60 mesh to 20 mesh, and argon gas is continuously introduced into the submerged arc furnace at a flow rate of 6L to 7L / min, the fly ash slag-forming agent is fly ash-slag-forming agent sintered body particles, the mass ratio of the fly ash to the slag-forming agent is 35:65, and the mass fraction of the slag-forming agent is 60% SiO 2 、40%Al 2 O 3 , the fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the fly ash is high calcium fly ash, the total mass of the fly ash-slag-forming agent sintered body particles introduced is 10% of the total mass of the silicon melt, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore-fired furnace for 1.5 hours. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0065] S3, after removing the floating slag in step S2, 530 kg of high-temperature silicon melt with a temperature not lower than 1800° C. is slowly flowed into the refining furnace, and the temperature in the refining furnace is maintained at 1800° C. to 2200° C. After standing for 30 minutes, the silicon melt is subjected to a composition test, and the measured contents are Si 97.36%, Fe 0.42%, Al 0.09%, and Ca 0.01%.

[0066] S4 adopts a powder spraying method with a flow rate of 30kg / min, each powder spraying lasts for 0.5min, and the powder spraying interval is 10min. 60kg of fly ash-removing agent sintered body particles with fly ash as carrier are introduced into the refining furnace. The particle size of the particles is 30 mesh to 10 mesh. At the same time, argon gas is continuously introduced into the refining furnace at a flow rate of 6L to 7L / min. In the fly ash-removing agent sintered body particles, the mass ratio of fly ash to iron remover is 50:50. The fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the fly ash is high calcium fly ash, the total mass of the fly ash-ironing agent sintered body particles introduced is 10% of the total mass of the silicon melt, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore-fired furnace for 1 hour. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0067] S5, take the silicon melt in the refining furnace for component detection, and measure the silicon melt, Si 99.52%, Fe<0.01%, Al<0.01%, Ca<0.01%, Ba<0.01%, B<0.01%, and the silicon melt passes the test and is discharged from the furnace, obtaining 464kg of high-purity industrial silicon with a purity higher than 99%.

[0068] Example 4

[0069] A method for preparing high-purity silicon by using crystalline silicon waste cut from solar cells, which is used to prepare industrial silicon with a purity higher than 99%, comprises the following steps:

[0070] S1, add 600kg of spherical silicon mud into a mineral arc furnace to prepare silicon melt, heat, and control the temperature of the silicon melt to reach 1800℃, and keep it warm for 30 minutes. The composition of the silicon melt is detected to obtain 87.15% silicon, 0.53% Al, 0.43% Ca, 0.18% Fe,

[0071] S2, by a powder spraying method with a flow rate of 20kg / min, each powder spraying lasts for 1min, and the powder spraying interval is 10min, 72kg of fly ash-slag-forming agent sintered body particles with fly ash as a carrier are introduced into the submerged arc furnace, the particle size of the particles is 60 mesh to 20 mesh, and argon gas is continuously introduced into the submerged arc furnace at a flow rate of 6L to 7L / min, the fly ash slag-forming agent is fly ash-slag-forming agent sintered body particles, the mass ratio of the fly ash to the slag-forming agent is 30:70, and the mass fraction of the slag-forming agent is 40% SiO 2 、50%Al 2 O 3 , 10% CaCl 2 , the fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the fly ash is high calcium fly ash, the total mass of the fly ash-slag-making agent sintered body particles introduced is 12% of the total mass of the silicon melt, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore-fired furnace for 1 hour. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0072] S3, after removing the floating slag in step S2, 520 kg of high-temperature silicon melt with a temperature not lower than 1800°C is slowly flowed into the refining furnace, and the temperature in the refining furnace is maintained at 1800°C ~ 2200°C. After standing for 30 minutes, the silicon melt is subjected to component detection, and the measured Si content is 98.36%, Fe 0.31%, Al<0.01%, and Ca<0.01%.

[0073] S4 adopts a powder spraying method with a flow rate of 10kg / min, each powder spraying lasts for 1min, and the powder spraying interval is 10min. 42kg of fly ash-removing agent sintered body particles with fly ash as carrier are introduced into the refining furnace. The particle size of the particles is 30 mesh to 10 mesh. At the same time, argon gas is continuously introduced into the refining furnace at a flow rate of 6L to 7L / min. In the fly ash-removing agent sintered body particles, the mass ratio of fly ash to iron remover is 45:55. The fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2, the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the fly ash is high calcium fly ash, the total mass of the fly ash-ironing agent sintered body particles introduced is 5% of the total mass of the silicon melt, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore furnace for 0.5 hours. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0074] S5, taking the silicon melt in the refining furnace for component detection, and measuring the Si content of the silicon melt is 99.64%, Fe<0.01%, Al<0.01%, Ca<0.01%, Ba<0.01%, B<0.01%. The silicon melt passes the test and is discharged from the furnace, obtaining 483kg of high-purity industrial silicon with a purity higher than 99%.

[0075] Example 5

[0076] A method for preparing high-purity silicon by using crystalline silicon waste cut from solar cells, which is used to prepare industrial silicon with a purity higher than 99%, comprises the following steps:

[0077] S1, adding 600kg of spherical silicon mud into a mineral arc furnace to prepare silicon melt, heating, and controlling the temperature of the silicon melt to reach 1800°C, and keeping it warm for 30 minutes, and detecting the composition of the silicon melt to obtain 83.26% silicon, 0.84% ​​Al, 0.15% Ca, 0.12% Ba and 0.05% Fe.

[0078] S2, by a powder spraying method with a flow rate of 10kg / min, each powder spraying lasts for 1min, and the powder spraying interval is 20min, 72kg of fly ash-slag-forming agent sintered body particles with fly ash as a carrier are introduced into the submerged arc furnace, the particle size of the particles is 60 mesh to 20 mesh, and argon gas is continuously introduced into the submerged arc furnace at a flow rate of 6L to 7L / min, the fly ash slag-forming agent is fly ash-slag-forming agent sintered body particles, the mass ratio of the fly ash to the slag-forming agent is 35:65, and the mass fraction of the slag-forming agent is 20% SiO 2 、50%Al 2 O 3 , 30% CaCO 3 , the fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2, the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the fly ash is high calcium fly ash, the total mass of the fly ash-slag-making agent sintered body particles introduced is 12% of the total mass of the silicon melt, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore furnace for 2 hours. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0079] S3, after removing the floating slag in step S2, 522 kg of high-temperature silicon melt with a temperature not lower than 1800°C is slowly flowed into the refining furnace, and the temperature in the refining furnace is maintained at 1800°C ~ 2200°C. After standing for 30 minutes, the silicon melt is subjected to component detection, and it is measured that Si is 97.94%, Fe is 0.01%, Al is less than 0.09%, and Ca is less than 0.02%.

[0080] S4 adopts a powder spraying method with a flow rate of 10kg / min, each powder spraying lasts for 1min, and the powder spraying interval is 20min. 42kg of fly ash-removing agent sintered body particles with fly ash as carrier are introduced into the refining furnace. The particle size of the particles is 30 mesh to 10 mesh. At the same time, argon gas is continuously introduced into the refining furnace at a flow rate of 6L to 7L / min. In the fly ash-removing agent sintered body particles, the mass ratio of fly ash to iron remover is 55:45. The fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the fly ash is high calcium fly ash, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore-fired furnace for 1 hour. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0081] S5, take the silicon melt in the refining furnace for component detection, and measure the silicon melt, Si 99.46%, Fe<0.01%, Al<0.01%, Ca<0.01%, Ba<0.01%, B<0.01%, and the silicon melt passes the test and is taken out of the furnace, obtaining 480kg of high-purity industrial silicon with a purity higher than 99%.

[0082] In the above-mentioned Examples 1 to 5, the preparation method of the fly ash-slag-forming agent sintered body particles in step S2 is: 30 to 35 parts of fly ash and 65 to 70 parts of slag-forming agent are mixed together and 20% to 25% of water which accounts for the total mass of the fly ash and the slag-forming agent is added, and 5% to 15% of a binder which accounts for the total mass of the fly ash and the slag-forming agent is fully mixed, and after being pelletized on a pelletizing machine, the mixture is heat-insulated and sintered at a high temperature of 1100°C to 1200°C, and after natural cooling, the particles are crushed and sieved to obtain particles of 60 mesh to 20 mesh, and the binder is water glass.

[0083] The preparation method of the fly ash-ironing agent sintered body particles in step S4 is as follows: 45-55 parts of fly ash and 45-55 parts of ironing agent are mixed together and 20%-25% of the total mass of the fly ash and ironing agent is added. After the fly ash and 5%-15% of the total mass of the binder are fully mixed, the fly ash and ironing agent are pelletized on a pelletizer, and then the pellets are kept warm and sintered at a high temperature of 1100° C. to 1200° C., and then the pellets are crushed and sieved to obtain 30-10 mesh particles after natural cooling. The ironing agent is 30-40% CaF 2 , 30~40%AlSn, 20~30%Na 2 SiF 6 , the binder is water glass.

[0084] The preparation method of the fly ash-slag-forming agent sintered body particles of Example 1 is as follows: 30 parts of fly ash and 70 parts of slag-forming agent are mixed together, and 25% of the total mass of the fly ash and the slag-forming agent is added. After the fly ash and the slag-forming agent are fully mixed, the fly ash and the slag-forming agent are pelletized on a pelletizer, and then the pellets are kept at a high temperature of 1100° C. to 1200° C. for 30 minutes, and the pellets are crushed and sieved to obtain 60-mesh to 20-mesh particles after natural cooling. The slag-forming agent component is 30 parts of SiO 2 、30 parts Al 2 O 3 , 20 parts BaO, 20 parts CaCO 3 .

[0085] The preparation method of the fly ash-ironing agent sintered body particles of Example 1 is as follows: 45 parts of fly ash and 55 parts of ironing agent are mixed together, and water accounting for 25% of the total mass of the fly ash and ironing agent is added, and water glass accounting for 10% of the total mass of the fly ash and ironing agent is fully mixed, and then pelletized on a pelletizer, and then sintered at a high temperature of 1100°C to 1200°C for 30 minutes, and then naturally cooled and crushed to obtain particles of 30 mesh to 10 mesh. The ironing agent is 40% by mass of CaF 2 , 30% AlSn, 30% Na 2 SiF 6 .

[0086] The preparation method of fly ash-slag-forming agent sintered body particles in Example 2 is as follows: 35 parts of fly ash and 65 parts of slag-forming agent are mixed together and 20% of the total mass of the fly ash and the slag-forming agent is added. After the fly ash and the slag-forming agent are fully mixed, the fly ash and the slag-forming agent are pelletized on a pelletizer, and then the pellets are sintered at a high temperature of 1100°C to 1200°C for 45 minutes. After natural cooling, the pellets are crushed and sieved to obtain particles of 60 mesh to 20 mesh. The slag-forming agent components are 60 parts of SiO2, 20 parts of Al 2 O 3 , 20 parts CaCl 2 .

[0087] The preparation method of the fly ash-ironing agent sintered body particles described in Example 2 is as follows: 55 parts of fly ash and 45 parts of ironing agent are mixed together, and water accounting for 25% of the total mass of the fly ash and ironing agent is added, and water glass accounting for 10% of the total mass of the fly ash and ironing agent is fully mixed, and then pelletized on a pelletizer, and then sintered at a high temperature of 1100°C to 1200°C for 45 minutes, and then naturally cooled and crushed to obtain particles of 30 mesh to 10 mesh. The ironing agent is 30% by mass of CaF 2 , 40% AlSn, 30% Na 2 SiF 6 .

[0088] The preparation method of fly ash-slag-forming agent sintered body particles in Example 3 is as follows: 35 parts of fly ash and 65 parts of slag-forming agent are mixed together, and 25% of the total weight of the fly ash and the slag-forming agent is added. After the fly ash and the slag-forming agent are fully mixed, the fly ash and the slag-forming agent are pelletized on a pelletizer, and then the pellets are sintered at a high temperature of 1100°C to 1200°C for 30 minutes. After natural cooling, the pellets are crushed and sieved to obtain particles of 60 mesh to 20 mesh. The slag-forming agent component is 60 parts of SiO 2 、40 parts Al 2 O 3 .

[0089] The preparation method of the fly ash-ironing agent sintered body particles described in Example 3 is as follows: 50 parts of fly ash and 50 parts of ironing agent are mixed together and 25% of the total mass of the fly ash and ironing agent is added. After the fly ash and ironing agent are fully mixed and pelletized on a pelletizer, the mixture is kept warm for 30 minutes at a high temperature of 1100°C to 1200°C, and then naturally cooled and crushed to obtain particles of 30 mesh to 10 mesh. The ironing agent is 40% by mass of CaF 2 , 40% AlSn, 20% Na 2 SiF 6 .

[0090] The preparation method of fly ash-slag-forming agent sintered body particles in Example 4 is as follows: 30 parts of fly ash and 70 parts of slag-forming agent are mixed together, and 25% of the total weight of the fly ash and the slag-forming agent is added. After the fly ash and the slag-forming agent are fully mixed, the fly ash and the slag-forming agent are pelletized on a pelletizer, and then the pellets are sintered at a high temperature of 1100° C. to 1200° C. for 30 minutes. After natural cooling, the pellets are crushed and sieved to obtain 60-mesh to 20-mesh particles. The slag-forming agent component is 40 parts of SiO 2 , 50 parts Al 2 O 3 , 10 parts CaCl 2 .

[0091] The preparation method of the fly ash-ironing agent sintered body particles described in Example 4 is as follows: 45 parts of fly ash and 55 parts of ironing agent are mixed together, and water accounting for 25% of the total mass of the fly ash and ironing agent is added, and water glass accounting for 15% of the total mass of the fly ash and ironing agent is fully mixed, and then pelletized on a pelletizer, and then sintered at a high temperature of 1100°C to 1200°C for 35 minutes, and then naturally cooled and crushed to obtain particles of 30 mesh to 10 mesh. The ironing agent is 40% by mass of CaF 2 , 40% AlSn, 20% Na 2 SiF 6 .

[0092] The preparation method of fly ash-slag-forming agent sintered body particles in Example 5 is as follows: 35 parts of fly ash and 65 parts of slag-forming agent are mixed together, and water accounting for 25% of the total mass of the fly ash and the slag-forming agent is added, and the fly ash and the slag-forming agent are fully mixed, and then pelletized on a pelletizer, and then sintered at a high temperature of 1100°C to 1200°C for 35 minutes, and then crushed and sieved to obtain particles of 60 mesh to 20 mesh after natural cooling. The slag-forming agent component is 20 parts of SiO 2 , 50 parts Al 2 O 3 , 30 parts CaCO 3 .

[0093] The preparation method of the fly ash-ironing agent sintered body particles described in Example 5 is as follows: 55 parts of fly ash and 45 parts of ironing agent are mixed together, and water accounting for 25% of the total mass of the fly ash and ironing agent is added, and water glass accounting for 15% of the total mass of the fly ash and ironing agent is fully mixed, and then pelletized on a pelletizer, and then sintered at a high temperature of 1100°C to 1200°C for 35 minutes, and then naturally cooled and crushed to obtain particles of 30 mesh to 10 mesh. The ironing agent is 35 parts by mass of CaF 2 , 35 parts AlSn, 30 parts Na 2 SiF 6 .

[0094] Comparative Example 1

[0095] The difference between this comparative example and Example 1 is that a one-step method is used to prepare high-purity industrial silicon, as follows:

[0096] A method for preparing high-purity silicon by using crystalline silicon waste cut from solar cells, which is used to prepare industrial silicon with a purity higher than 99%, comprises the following steps:

[0097] S1, adding 600kg silicon mud into a mineral arc furnace to prepare silicon melt, heating, and controlling the temperature of the silicon melt to reach 1800°C, and keeping it warm for 30 minutes, and detecting the composition of the silicon melt to obtain 88.26% silicon, 0.17% Al, 0.23% Ca, 0.12% Ba, 0.85% Fe, and 0.08% B.

[0098] S2, by means of powder spraying, 72 kg of fly ash-slag-forming agent sintered body particles with fly ash as carrier are introduced into the submerged arc furnace, the particle size of the particles is 60 mesh to 20 mesh, 30 kg of fly ash-removal agent sintered body particles with fly ash as carrier are introduced, the particle size of the particles is 30 mesh to 10 mesh, and argon gas is continuously introduced into the submerged arc furnace at a flow rate of 6L to 7L / min. The fly ash slag-forming agent is fly ash-slag-forming agent sintered body particles, the mass ratio of the fly ash to the slag-forming agent is 30:70, and the mass fraction of the slag-forming agent is 30% SiO 2 、25%Al 2 O 3 , 20%BaO, 25%CaCO 3 In the fly ash-ironing agent sintered body particles, the mass ratio of fly ash to iron removing agent is 45:55, and the fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , fly ash with stability ≤5mm, and molten silicon are fully slag-formed in a submerged arc furnace for 1 hour.

[0099] S3, taking the silicon melt in the refining furnace for component detection, it is measured that in the silicon melt, Si is 98.68%, Fe is 0.41%, Al is 0.01%, Ca is less than 0.01%, Ba is less than 0.01%, and B is less than 0.01%, and 452kg of high-purity industrial silicon with a purity of 98.68% is obtained.

[0100] Comparative Example 2

[0101] The difference between this comparative example and Example 1 is that a common spray pipe is used for powder spraying, and the inert gas pipeline and the powder spraying pipeline are separated.

[0102] After refining, the silicon melt was measured to contain 97.35% Si, 0.03% Fe, 0.01% Al and 0.01% Ca.

[0103] Comparative Example 3

[0104] The difference between this comparative example and implementation 1 is that the slag-making agent used does not have a fly ash carrier.

[0105] A method for preparing high-purity silicon by using crystalline silicon waste cut from solar cells, which is used to prepare industrial silicon with a purity higher than 99%, comprises the following steps:

[0106] S1, adding 600kg silicon mud into a mineral arc furnace to prepare silicon melt, heating, and controlling the temperature of the silicon melt to reach 1800°C, and keeping it warm for 30 minutes, and detecting the composition of the silicon melt to obtain 88.26% silicon, 0.17% Al, 0.23% Ca, 0.12% Ba, 0.85% Fe, and 0.08% B.

[0107] S2, by a powder spraying method with a flow rate of 10kg / min, each powder spraying lasts for 1min, and the powder spraying interval is 10min, 72kg of slag-forming agent is introduced into the submerged arc furnace, and the particle size of the slag-forming agent is 60 mesh to 20 mesh. At the same time, argon gas is continuously introduced into the submerged arc furnace at a flow rate of 6L to 7L / min, and the mass fraction of the slag-forming agent is 30% SiO 2 、30%Al 2 O 3 , 20%BaO, 20%CaCO 3 After the powder spraying is completed, the silicon melt is fully slag-formed in the submerged arc furnace for 1 hour. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0108] S3, after removing the floating slag in step S2, 520 kg of high-temperature silicon melt with a temperature not lower than 1800°C is slowly flowed into the refining furnace, and the temperature in the refining furnace is maintained at 1800°C ~ 2200°C. After standing for 30 minutes, the silicon melt is subjected to component detection, and the measured content is Si 98.52%, Fe 0.63%, Al 0.06%, Ca 0.03%, Ba<0.01%, and B<0.01%.

[0109] S4, by the powder spraying method of flow rate of 10kg / min, each powder spraying for 1min, and powder spraying once every 10min, 30kg of iron removal agent particles with a particle size of 30 mesh to 10 mesh are introduced into the refining furnace, and argon gas is continuously introduced into the refining furnace at a flow rate of 6L to 7L / min. After the powder spraying is completed, the silicon melt is fully slag-formed in the ore-fired furnace for 0.5 hour. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0110] S5, take the silicon melt in the refining furnace for component detection, and measure the silicon melt, Si 99.35%, Fe<0.01%, Al<0.01%, Ca<0.01%, Ba<0.01%, B<0.01%, and the silicon melt passes the test and is taken out of the furnace, obtaining 430kg of high-purity industrial silicon with a purity higher than 99%.

[0111] Comparative Example 4

[0112] The difference between this comparative example and Example 1 is that no iron removal agent is used as the slag-making agent.

[0113] A method for preparing high-purity silicon by using crystalline silicon waste cut from solar cells, which is used to prepare industrial silicon with a purity higher than 99%, comprises the following steps:

[0114] S1, adding 600kg silicon mud into a mineral arc furnace to prepare silicon melt, heating, and controlling the temperature of the silicon melt to reach 1800°C, and keeping it warm for 30 minutes, and detecting the composition of the silicon melt to obtain 88.26% silicon, 0.17% Al, 0.23% Ca, 0.12% Ba, 0.85% Fe, and 0.08% B.

[0115] S2, by a powder spraying method with a flow rate of 10kg / min, each powder spraying lasts for 1min, and the powder spraying interval is 10min, 72kg of slag-forming agent is introduced into the submerged arc furnace, and the particle size of the slag-forming agent is 60 mesh to 20 mesh. At the same time, argon gas is continuously introduced into the submerged arc furnace at a flow rate of 6L to 7L / min, and the mass fraction of the slag-forming agent is 30% SiO 2 、30%Al 2 O 3 , 20%BaO, 20%CaCO 3 After the powder spraying is completed, the silicon melt is fully slag-formed in the submerged arc furnace for 1 hour. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0116] S3, after removing the floating slag in step S2, 520 kg of high-temperature silicon melt with a temperature not lower than 1800°C is slowly flowed into the refining furnace, and the temperature in the refining furnace is maintained at 1800°C ~ 2200°C. After standing for 30 minutes, the silicon melt is subjected to component detection, and the measured content is Si 98.52%, Fe 0.63%, Al 0.06%, Ca 0.03%, Ba<0.01%, and B<0.01%.

[0117] Comparative Example 5

[0118] The difference between this comparative example and Example 1 is that the method of adding the slag-forming agent is a conventional direct pouring method.

[0119] S1, adding 600kg of spherical silicon mud into a mineral arc furnace to prepare silicon melt, heating, and controlling the temperature of the silicon melt to reach 1800°C, and keeping it warm for 30 minutes, and detecting the composition of the silicon melt to obtain 88.26% silicon, 0.17% Al, 0.23% Ca, 0.12% Ba, 0.85% Fe, and 0.08% B.

[0120] S2, 72 kg of fly ash-slag-forming agent sintered body particles with fly ash as carrier are introduced into the submerged arc furnace, the particle size of the particles is 60 mesh to 20 mesh, and argon gas is continuously introduced into the submerged arc furnace at a flow rate of 6 L to 7 L / min. The fly ash slag-forming agent is fly ash-slag-forming agent sintered body particles, the mass ratio of the fly ash to the slag-forming agent is 30:70, and the mass fraction of the slag-forming agent is 30% SiO 2 、30%Al 2 O 3 , 20%BaO, 20%CaCO 3 , the fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , the stability of the fly ash is ≤5mm, the total mass of the fly ash-slag-forming agent sintered body particles introduced is 12% of the total mass of the silicon melt, and the silicon melt is fully slag-formed in the electric arc furnace for 1 hour.

[0121] S3, after removing the floating slag in step S2, 510 kg of high-temperature molten silicon with a temperature not lower than 1800°C is slowly flowed into the refining furnace, and the temperature in the refining furnace is maintained at 1800°C ~ 2200°C. After standing for 30 minutes, the composition of the molten silicon is detected, and it is measured that Si is 96.42%, Fe is 0.71%, Al is 0.08%, Ca is 0.03%, Ba is less than 0.01%, and B is less than 0.01%.

[0122] S4: 30 kg of fly ash-ironing agent sintered particles with fly ash as carrier are introduced into the refining furnace, and the particle size of the particles is 30 mesh to 10 mesh. At the same time, argon is continuously introduced into the refining furnace at a flow rate of 6 L to 7 L / min. In the fly ash-ironing agent sintered particles, the mass ratio of fly ash to iron removing agent is 45:55. The fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , the stability of the fly ash is ≤5mm, the total mass of the fly ash-ironing agent sintered body particles introduced is 5% of the total mass of the silicon melt, and the silicon melt is fully slag-formed in the ore-fired furnace for 0.5 hours.

[0123] S5, taking the silicon melt in the refining furnace for component detection, it is measured that the silicon melt contains 99.02% Si, 0.02% Fe, 0.03% Al, and 0.01% Ca. The silicon melt passes the test and is discharged from the furnace, obtaining 492kg of high-purity industrial silicon with a purity higher than 99%.

[0124] Comparative Example 6

[0125] The difference between this comparative example and Example 1 is that the proportion of fly ash is too high.

[0126] A method for preparing high-purity silicon by using crystalline silicon waste cut from solar cells, which is used to prepare industrial silicon with a purity higher than 99%, comprises the following steps:

[0127] S1, adding 600kg silicon mud into a mineral arc furnace to prepare silicon melt, heating, and controlling the temperature of the silicon melt to reach 1800°C, and keeping it warm for 30 minutes, and detecting the composition of the silicon melt to obtain 88.26% silicon, 0.17% Al, 0.15% Ca, 0.12% Ba, 0.85% Fe, and 0.08% B.

[0128] S2, by means of powder spraying, 72 kg of fly ash-slag-forming agent sintered body particles with fly ash as carrier are introduced into the submerged arc furnace, the particle size of the particles is 60 mesh to 20 mesh, and argon gas is continuously introduced into the submerged arc furnace at a flow rate of 6L to 7L / min, the fly ash slag-forming agent is fly ash-slag-forming agent sintered body particles, the mass ratio of the fly ash to the slag-forming agent is 50:50, and the mass fraction of the slag-forming agent is 30% SiO 2 、250%Al 2 O 3 , 20%BaO, 25%CaCO 3 , the fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , the stability of the fly ash is ≤5mm, the total mass of the fly ash-slag-forming agent sintered body particles introduced is 12% of the total mass of the silicon melt, and the silicon melt is fully slag-formed in the electric arc furnace for 1 hour.

[0129] S3, remove the floating slag in step S2, slowly flow 513kg of high-temperature silicon melt with a temperature not lower than 1800°C into the refining furnace, maintain the temperature in the refining furnace at 1800°C ~ 2200°C, and after standing for 30 minutes, perform component detection on the silicon melt, and it is measured that Si is 93.59%, Fe is 0.71%, Al is 0.08%, Ca is 0.03%, Ba is less than 0.01%, and B is less than 0.01%.

[0130] S4: 30 kg of fly ash-ironing agent sintered particles with fly ash as carrier are introduced into the refining furnace by powder spraying, and the particle size is 30 mesh to 10 mesh. At the same time, argon is continuously introduced into the refining furnace at a flow rate of 6L to 7L / min. In the fly ash-ironing agent sintered particles, the mass ratio of fly ash to iron removing agent is 60:40. The fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 、CaO total mass fraction ≥ 80%, density ≤ 2.5g / cm 3 , fly ash with stability ≤5mm, and molten silicon are fully slag-formed in a submerged arc furnace for 0.5 hour.

[0131] S5, taking the silicon melt in the refining furnace for component detection, and measuring the silicon melt, Si 95.13%, Fe 0.51%, Al 0.05%, Ca 0.06%, to obtain 502kg of high-purity industrial silicon with a purity of 95.13%.

[0132] Comparative Example 7

[0133] The difference between this comparative example and Example 1 is that the proportion of fly ash is too low

[0134] A method for preparing high-purity silicon by using crystalline silicon waste cut from solar cells, which is used to prepare industrial silicon with a purity higher than 99%, comprises the following steps:

[0135] S1, adding 600kg of spherical silicon mud into a mineral arc furnace to prepare silicon melt, heating, and controlling the temperature of the silicon melt to reach 1800°C, and keeping it warm for 30 minutes, and detecting the composition of the silicon melt to obtain 88.26% silicon, 0.17% Al, 0.23% Ca, 0.12% Ba, 0.85% Fe, and 0.08% B.

[0136] S2, by a powder spraying method with a flow rate of 10kg / min, each powder spraying lasts for 1min, and the powder spraying interval is 10min, 72kg of fly ash-slag-forming agent sintered body particles with fly ash as a carrier are introduced into the submerged arc furnace, the particle size of the particles is 60 mesh to 20 mesh, and argon gas is continuously introduced into the submerged arc furnace at a flow rate of 6L to 7L / min, the fly ash slag-forming agent is fly ash-slag-forming agent sintered body particles, the mass ratio of the fly ash to the slag-forming agent is 30:70, and the mass fraction of the slag-forming agent is 30% SiO 2 、30%Al 2 O 3 , 20%BaO, 20%CaCO 3 , the fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the total mass of the fly ash-slag-forming agent sintered body particles introduced is 12% of the total mass of the silicon melt, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore-fired furnace for 1 hour. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0137] S3, after removing the floating slag in step S2, 518 kg of high-temperature molten silicon with a temperature not lower than 1800°C is slowly flowed into the refining furnace, and the temperature in the refining furnace is maintained at 1800°C ~ 2200°C. After standing for 30 minutes, the composition of the molten silicon is detected, and it is measured that Si is 96.47%, Fe is 0.69%, Al is 0.11%, Ca is 0.04%, Ba is less than 0.01%, and B is less than 0.01%.

[0138] S4 adopts a powder spraying method with a flow rate of 10kg / min, each powder spraying lasts for 1min, and the powder spraying interval is 10min. 30kg of fly ash-removing agent sintered body particles with fly ash as carrier are introduced into the refining furnace. The particle size of the particles is 30 mesh to 10 mesh. At the same time, argon gas is continuously introduced into the refining furnace at a flow rate of 6L to 7L / min. In the fly ash-removing agent sintered body particles, the mass ratio of fly ash to iron remover is 45:55. The fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the total mass of the fly ash-ironing agent sintered body particles introduced is 5% of the total mass of the silicon melt, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore-fired furnace for 0.5 hours. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0139] S5, taking the silicon melt in the refining furnace for component detection, and measuring the silicon melt, Si 98.34%, Fe 0.04%, Al 0.03%, Ca 0.01%, to obtain 511kg of high-purity industrial silicon with a purity of 98.34%.

[0140] Comparative Example 8

[0141] The difference between this comparative example and Example 1 is that the particle size is too high

[0142] A method for preparing high-purity silicon by using crystalline silicon waste cut from solar cells, which is used to prepare industrial silicon with a purity higher than 99%, comprises the following steps:

[0143] S1, adding 600kg of spherical silicon mud into a mineral arc furnace to prepare silicon melt, heating, and controlling the temperature of the silicon melt to reach 1800°C, and keeping it warm for 30 minutes, and detecting the composition of the silicon melt to obtain 88.26% silicon, 0.17% Al, 0.23% Ca, 0.12% Ba, 0.85% Fe, and 0.08% B.

[0144] S2, by a powder spraying method with a flow rate of 10kg / min, each powder spraying lasts for 1min, and the powder spraying interval is 10min, 72kg of fly ash-slag-forming agent sintered body particles with fly ash as a carrier are introduced into the submerged arc furnace, the particle size of the particles is 60 mesh to 20 mesh, and argon gas is continuously introduced into the submerged arc furnace at a flow rate of 6L to 7L / min, the fly ash slag-forming agent is fly ash-slag-forming agent sintered body particles, the mass ratio of the fly ash to the slag-forming agent is 30:70, and the mass fraction of the slag-forming agent is 30% SiO 2 、30%Al 2 O 3 , 20%BaO, 20%CaCO 3 , the fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the total mass of the fly ash-slag-forming agent sintered body particles introduced is 12% of the total mass of the silicon melt, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore-fired furnace for 1 hour. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0145] S3, after removing the floating slag in step S2, 544 kg of high-temperature silicon melt with a temperature not lower than 1800°C is slowly flowed into the refining furnace, and the temperature in the refining furnace is maintained at 1800°C ~ 2200°C. After standing for 30 minutes, the silicon melt is subjected to component detection, and it is measured that Si is 96.43%, Fe is 0.62%, Al is 0.07%, Ca is 0.04%, Ba is less than 0.01%, and B is less than 0.01%.

[0146] S4 adopts a powder spraying method with a flow rate of 10kg / min, each powder spraying lasts for 1min, and the powder spraying interval is 10min. 30kg of fly ash-removing agent sintered body particles with fly ash as carrier are introduced into the refining furnace. The particle size of the particles is 30 mesh to 10 mesh. At the same time, argon gas is continuously introduced into the refining furnace at a flow rate of 6L to 7L / min. In the fly ash-removing agent sintered body particles, the mass ratio of fly ash to iron remover is 45:55. The fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the total mass of the fly ash-ironing agent sintered body particles introduced is 5% of the total mass of the silicon melt, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore-fired furnace for 0.5 hours. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0147] S5, taking the silicon melt in the refining furnace for component detection, and measuring the silicon melt, Si 98.27%, Fe 0.02%, Al 0.020.01%, Ca < 0.01%, and obtaining 518 kg of high-purity industrial silicon with a purity of 98.27%.

[0148] Comparative Example 9

[0149] The difference between this comparative example and the embodiment is that the particle size is too small

[0150] A method for preparing high-purity silicon by using crystalline silicon waste cut from solar cells, which is used to prepare industrial silicon with a purity higher than 99%, comprises the following steps:

[0151] S1, adding 600kg of spherical silicon mud into a mineral arc furnace to prepare silicon melt, heating, and controlling the temperature of the silicon melt to reach 1800°C, and keeping it warm for 30 minutes, and detecting the composition of the silicon melt to obtain 88.26% silicon, 0.17% Al, 0.23% Ca, 0.12% Ba, 0.85% Fe, and 0.08% B.

[0152] S2, by a powder spraying method with a flow rate of 10kg / min, each powder spraying lasts for 1min, and the powder spraying interval is 10min, 72kg of fly ash-slag-forming agent sintered body particles with fly ash as a carrier are introduced into the submerged arc furnace, the particle size of the particles is 60 mesh to 20 mesh, and argon gas is continuously introduced into the submerged arc furnace at a flow rate of 6L to 7L / min, the fly ash slag-forming agent is fly ash-slag-forming agent sintered body particles, the mass ratio of the fly ash to the slag-forming agent is 30:70, and the mass fraction of the slag-forming agent is 30% SiO 2 、30%Al 2 O 3 , 20%BaO, 20%CaCO 3 , the fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO 2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the total mass of the fly ash-slag-forming agent sintered body particles introduced is 12% of the total mass of the silicon melt, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore-fired furnace for 1 hour. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0153] S3, after removing the floating slag in step S2, 542 kg of high-temperature silicon melt with a temperature not lower than 1800°C is slowly flowed into the refining furnace, and the temperature in the refining furnace is maintained at 1800°C ~ 2200°C. After standing for 30 minutes, the silicon melt is subjected to component detection, and it is measured that Si is 97.86%, Fe is 0.58%, Al is 0.06%, Ca is 0.06%, Ba is less than 0.01%, and B is less than 0.01%.

[0154] S4 adopts a powder spraying method with a flow rate of 10kg / min, each powder spraying lasts for 1min, and the powder spraying interval is 10min. 30kg of fly ash-removing agent sintered body particles with fly ash as carrier are introduced into the refining furnace. The particle size of the particles is 30 mesh to 10 mesh. At the same time, argon gas is continuously introduced into the refining furnace at a flow rate of 6L to 7L / min. In the fly ash-removing agent sintered body particles, the mass ratio of fly ash to iron remover is 45:55. The fly ash is SiO 2 、Al 2 O 3 ,FeO,Fe 2 O 3 、TiO2 , the total mass fraction of CaO is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤ 5mm fly ash, the total mass of the fly ash-ironing agent sintered body particles introduced is 5% of the total mass of the silicon melt, after the powder spraying is completed, the silicon melt is fully slag-formed in the ore-fired furnace for 0.5 hours. Figure 1 The powder spraying method of the inert gas and the powder particles described in this step is a concentric circle powder spraying method, the center of the concentric circle is a mixture of the inert gas and the powder particles, and the outer circle of the concentric circle is the inert gas.

[0155] S5, taking the silicon melt in the refining furnace for component detection, and measuring the silicon melt, Si 98.93%, Fe 0.02%, Al 0.02%, Ca < 0.01%, and obtaining 519kg of high-purity industrial silicon with a purity of 98.9%.

[0156] Comparative Example 10

[0157] The difference between this comparative example and Example 1 is that the fly ash used is low-calcium fly ash.

[0158] The composition of the silicon solution obtained in step S2 is Si 98.42%, Fe 0.63%, Al 0.07%, and Ca 0.05%;

[0159] The composition of the silicon solution obtained in step S4 is Si 99.32%, Fe<0.01%, Al<0.01%, Ca<0.01%, and 510 kg of high-purity industrial silicon with a purity of 99.32% is obtained.

[0160] Table 1 is a table of industrial silicon compositions obtained in various embodiments and comparative examples.

[0161] Table 1 Composition of industrial silicon obtained in each embodiment

[0162]

[0163]

[0164] By comparing Example 1 with Comparative Example 1, the method of removing molten silicon in an ore-fired furnace and a refining furnace respectively in Example 1 can significantly improve the purity of molten silicon. In Example 1 of the present application, most of the impurities such as Al, Ca, and B are first removed in an ore-fired furnace, and the impurities Fe and a small amount of Al, Ca, etc. are further removed in a refining furnace. Obviously, the silicon solution obtained in Example 1 has a higher purity.

[0165] By comparing Example 1 with Comparative Example 2, the powder spraying pipe and the inert gas spraying pipe used in Example 1 are arranged in a concentric powder spraying mode, the center of the concentric circle is a mixture of inert gas and powder spraying particles, and the outer circle of the concentric circle is inert gas, which can prevent the introduction of too much oxygen during the powder spraying process to oxidize silicon. Through the outer circle inert gas, on the one hand, vacuum directional solidification can be achieved to remove impurities such as Al, Mg or Ca, and on the other hand, silicon solution and high-temperature molten slag-forming agent can be prevented from clogging the powder spraying pipe. Comparative Example 2 uses an ordinary spraying pipe for powder spraying, and the inert gas pipeline and the powder spraying pipeline are separated. During the powder spraying process, the pipe mouth will be blocked, resulting in a decrease in the actual powder spraying amount within a specific time, affecting the slag removal effect and output.

[0166] By comparing Example 1 with Comparative Example 3, Example 1 uses fly ash as a carrier of slag remover sintered body particles for slag removal, making full use of the porous structure of fly ash to adsorb the formed oxides and aggregate them together under high temperature, thereby improving the slag removal efficiency. However, the slag remover of Comparative Example 3 does not use fly ash, resulting in the need to consume more slag remover, and because the slag remover is a powder device, impurities in the silicon melt and the slag formed cannot be quickly focused together, on the one hand, the slag removal efficiency is low, and on the other hand, the slag layer is thick, and more silicon is attached to the slag layer, reducing the yield of high-purity silicon.

[0167] By comparing Example 1 with Comparative Example 4, Example 1 adds iron remover particles with fly ash as a carrier, and uses the iron remover in the sinter to generate iron-containing metal compounds with iron at high temperature, and gathers on the fly ash melt, and the remaining Al, Ca and other substances in the silicon melt are also focused together under the action of the fly ash and float on the upper layer of the silicon melt. The present application can remove impurities in the silicon melt and obtain high-purity industrial silicon with a purity higher than 99%.

[0168] By comparing Example 1 with Comparative Example 5, Example 1 uses a powder spraying method to add fly ash-slag-forming agent sintered body particles to the silicon melt. By using the powder spraying method, the fly ash-slag-forming agent sintered body particles can be efficiently dispersed into the silicon melt, and the silicon melt in various parts of the furnace can be quickly deslaged, thereby improving the slag-making efficiency of impurities in the silicon melt. Comparative Example 5 uses a conventional direct pouring method to add a slag-forming agent to the silicon melt, resulting in uneven distribution of the slag-forming agent in the silicon melt, resulting in poor product consistency and low impurity removal efficiency.

[0169] By comparing Example 1 with Comparative Example 6, in Comparative Example 6, the fly ash accounts for too high a proportion in the fly ash-slag-forming agent sintered body particles, resulting in a relatively low proportion of effective ingredients of the slag-forming agent, which is not conducive to removing impurities in the silicon melt.

[0170] By comparing Example 1 with Comparative Example 7, in Comparative Example 7, the proportion of fly ash-slag-forming agent sintered body particles and fly ash is too low, resulting in impurities and slag formed by impurities and slag-forming agent cannot be efficiently aggregated together. Under the same conditions, the slag-forming efficiency is low, and the purity of the obtained silicon melt does not meet the requirements.

[0171] By comparing Example 1 with Comparative Example 8, the particle size of Comparative Example 8 is too high, which makes powder spraying difficult and the powder spraying particles have insufficient power in the silicon melt, resulting in low dispersion efficiency of the powder spraying particles in the silicon melt.

[0172] By comparing Example 1 with Comparative Example 9, the particle size of Comparative Example 9 is too small. The too small particle size leads to too small a slag volume, which is not conducive to focusing of the slag and reduces the efficiency of removing impurities.

[0173] By comparing Example 1 with Comparative Example 10, Comparative Example 10 uses low-calcium fly ash, which has a relatively low CaO content and a relatively low slag removal efficiency compared to high-calcium fly ash.

[0174] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing high-purity silicon using crystalline silicon waste cut from solar cells, for preparing high-purity silicon with a silicon content of ≥99%, characterized in that: Here are the steps: 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 at the same time, an inert gas is continuously introduced into the submerged arc furnace, and the fly ash slag-forming agent is fly ash-slag-forming agent sintered body particles, and the mass ratio of fly ash to slag-forming agent in the fly ash-slag-forming agent sintered body particles is 30-35:65-70, and the total mass of the introduced fly ash-slag-forming agent sintered body particles is 10%-15% of the total mass of the silicon melt; the preparation method of the fly ash-slag-forming agent sintered body particles is: 30-35 parts of fly ash and 65-70 parts of slag-forming agent are mixed together, and water accounting for 20%-25% of the total weight of the fly ash and the slag-forming agent, and a binder accounting for 5%-15% of the total weight of the fly ash and the slag-forming agent are added, and after being fully mixed, pelletized on a pelletizing machine, heat-insulated and sintered at a high temperature of 1100° C. to 1200° C., and crushed and sieved to obtain particles of 60 mesh to 20 mesh after natural cooling; the slag-forming agent is a composition formed by any one of SiO2, Al2O3, CaCO3, and CaO or a combination of multiple 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 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 the silicon melt; the preparation method of the fly ash-ironing agent sintered body particles is: 45-55 parts of fly ash, 45 ~55 parts of iron remover are mixed together and 20%~25% of water in total weight of the fly ash and the iron remover, 5%~15% of binder in total weight of the fly ash and the iron remover are added, after being fully mixed, and pelletized on a pelletizer, sintered at a high temperature of 1100°C~1200°C, and crushed and sieved to obtain 30-mesh~10-mesh particles after natural cooling; the composition of the iron remover is 30~40wt%CaF2, 30~40wt%AlSn, and 20~30wt%Na2SiF6; 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 SiO2, Al2O3, FeO, Fe2O3, TiO2 and CaO in the fly ash is ≥90%, and the tap density is ≤3g / cm 3 , bulk density ≤1.2g / cm 3 , stability ≤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 according to claim 1, characterized in that: The particle size of the fly ash-slag-forming agent sintered body 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 according to claim 1, characterized in that: The particle size of the fly ash-iron remover sintered body 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 according to claim 1, characterized in that: The powder spraying flow rate is 10kg / min to 30kg / min, and the powder spraying method is interval powder spraying.

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

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