CN112723358B - Method for reducing iron and removing phosphorus of industrial silicon - Google Patents
Method for reducing iron and removing phosphorus of industrial silicon Download PDFInfo
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Abstract
The invention relates to a method for reducing iron and removing phosphorus in industrial silicon, belonging to the technical field of metallurgical industry. The method comprises the steps of finely grinding industrial silicon to obtain industrial silicon powder, placing the industrial silicon powder in an acid solution, stirring for reaction to remove iron, cleaning and drying to obtain low-iron industrial silicon powder, placing the low-iron industrial silicon powder in a vacuum induction furnace with a plasma torch, carrying out induction heating on the industrial silicon powder to a molten state under a vacuum condition to obtain molten silicon, guiding plasma jet induced by electric arc to the surface of the molten silicon for chemical smelting, stirring the molten silicon by the plasma jet to generate a high-temperature point, volatilizing phosphorus from the molten silicon to obtain low-phosphorus molten silicon, cooling the low-phosphorus molten silicon to room temperature along with the furnace to obtain a silicon ingot, and removing scum on the surface of the silicon ingot to obtain the low-phosphorus industrial silicon. The method has the advantages of simple process and equipment, convenient operation, high universality to raw materials and good phosphorus removal effect.
Description
Technical Field
The invention relates to a method for reducing iron and removing phosphorus in industrial silicon, belonging to the technical field of metallurgical industry.
Background
The current global energy industry development trend is typically towards energy transformation, and new energy and renewable energy are increasingly in proportion, wherein solar energy is favored by people due to the universality, richness, safety and cleanness, and becomes the renewable energy with the most development potential.
Due to the difference between the technical means and the production cost, the crystalline silicon solar cell always occupies the mainstream position in the photovoltaic market due to the advantages of low cost and high conversion efficiency, and the crystalline silicon solar cell occupies about 90% of the market share of the global photovoltaic industry at present and is the most competitive product of the solar cell.
Crystalline silicon is a basic material for the fabrication of crystalline silicon solar cells. The too high content of phosphorus in the crystalline silicon can lead to the compound cavity of the phosphorus in the crystalline silicon to become the compound center of the photon-generated minority carrier, induce the generation of crystal defects, reduce the minority carrier lifetime and influence the photoelectric conversion efficiency. At present, the method of high vacuum distillation and slagging refining is mainly adopted to remove phosphorus in industrial silicon.
In the prior art, the method for removing the impurity phosphorus in silicon comprises the steps of introducing inert gas into a vacuum induction furnace at 1450-1600 ℃, using a calcium-containing alloy or a calcium compound with strong reducibility as a dephosphorizing agent, using a calcium halide as a fluxing agent, carrying out dephosphorization reaction in a silicon melting state, and removing other impurities by acid washing. The method needs to be carried out in an argon environment, and the phosphorus removal effect needs to be improved. The method for removing boron and phosphorus impurities in industrial silicon by adopting rare earth oxide introduces the rare earth oxide into the slag former, wherein the specific component is R X O Y (Y 2 O 3 、La 2 O 3 、CeO 2 、Sm 2 O 3 )-SiO 2 -BaO-CaF 2 And carrying out slagging for 40min under vacuum by medium frequency induction, wherein the weight ratio of slag to silicon is 1:1, and the P content is reduced from 15ppmw to 1.5 ppmw. The method adopts rare earth oxide as a slagging agent, has high cost and is not beneficial to large-scale production. The method for removing boron and phosphorus by slagging refining selects iron oxide and SiO as slagging agents 2 MnO and CaF 2 (ii) a The iron oxide is Fe 2 O 3 、FeO、Fe 3 O 4 One of (1); the mass ratio of the slagging constituent to the industrial silicon is (20-26) to (5-9). Heating to 1550- 2 And O, repeating slagging for 8-15 times, and reducing the content of phosphorus to a lower level. The method has long process flow and high energy consumption, and is not beneficial to industrial application.
Disclosure of Invention
The invention provides a method for removing iron and phosphorus from industrial silicon, which aims at the problem of removing phosphorus from industrial silicon in the prior art.
A method for reducing iron and removing phosphorus in industrial silicon comprises the following specific steps:
(1) finely grinding industrial silicon to obtain industrial silicon powder;
(2) putting the industrial silicon powder obtained in the step (1) into an acid solution, stirring for reaction, removing iron, cleaning and drying to obtain low-iron industrial silicon powder;
(3) placing the low-iron industrial silicon powder obtained in the step (2) into a vacuum induction furnace provided with a plasma torch, and carrying out induction heating on the industrial silicon powder to a molten state under a vacuum condition to obtain molten silicon;
(4) guiding the plasma jet induced by the electric arc to the surface of the molten silicon in the step (3) for chemical smelting, stirring the molten silicon by the plasma jet to generate a high temperature point, and volatilizing phosphorus to escape from the molten silicon to obtain low-phosphorus molten silicon;
(5) and (4) cooling the low-phosphorus molten silicon to room temperature along with the furnace to obtain a silicon ingot, and removing scum on the surface of the silicon ingot to obtain the low-phosphorus industrial silicon.
The particle size of the industrial silicon powder in the step (1) is not more than 1000 μm; the specific particle size is 250-1000 μm, 150-250 μm, 106-150 μm, 75-106 μm or less than 75 μm;
preferably, the particle size of the industrial silicon powder is 75-106 μm.
The acid solution in the step (2) is HNO 3 HCl, aqua regia, HNO 3 -HF mixed acid or HCl-HF mixed acid.
Further, the HNO 3 The concentration is 2-6mol/L, the HCl concentration is 2-6mol/L, HNO 3 HNO in HF mixed acid 3 The concentration is 1-5mol/L, HF and 1-5mol/L, and the concentration of HCl in the HCl-HF mixed acid is 1-5mol/L, HF and 1-5 mol/L;
preferably, the HNO 3 Concentration of 4mol/L, HCl concentration of 4mol/L, HNO 3 HNO in HF mixed acid 3 The concentration is 4mol/L, HF and 1mol/L, and the concentration of HCl in the HCl-HF mixed acid is 4mol/L, HF and 1 mol/L;
the reaction temperature in the step (2) is 35-75 ℃, the reaction time is 2-8h, and the liquid-solid ratio mL of the acid solution to the industrial silicon powder is 2-6: 1;
the power of the plasma generator is 13-16kW, and the chemical smelting time of the arc-induced plasma jet is 5-
20min, plasma gas is 20-60mm away from the molten silicon liquid surface, and gas flow rate is 4.0-7.0m 3 /h；
The plasma gas in the step (4) is Ar or Ar-O 2 Mixed gases or Ar-H 2 Mixing gas;
further, said Ar-O 2 The volume fraction of Ar in the mixed gas is 95 percent, and Ar-H 2 The volume fraction of Ar in the mixed gas is 70% or 95%;
the beneficial effects of the invention are:
(1) the method adopts the acid solution to remove the iron in the industrial silicon, thereby eliminating the inhibition of impurity iron on phosphorus in the phosphorus removal process and achieving the purpose of improving the impurity phosphorus removal efficiency;
(2) the invention adopts a wet leaching method to reduce or remove the iron content in the industrial silicon as far as possible, and then adopts a thermal plasma arc melting method to achieve the purpose of deeply removing impurity phosphorus under the condition that the iron content in the industrial silicon is as low as possible; compared with the method of directly implementing thermal plasma arc melting without adopting the step of acid leaching and iron removal, the removal efficiency of impurity phosphorus in the industrial silicon is obviously improved after the iron is reduced by acid leaching;
(3) The method has the advantages of simple process and equipment, convenient operation, high universality of raw materials and good phosphorus removal effect.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but the scope of the present invention is not limited to the description.
Comparative example: finely grinding industrial silicon with Fe and P contents of 4749ppmw and 64ppmw respectively to obtain industrial silicon powder with the particle size of 75-106 microns, placing 100g of industrial silicon powder into a high-purity graphite crucible in a vacuum induction furnace with a plasma torch, and carrying out induction heating to a molten state under a vacuum condition to obtain molten silicon; directing a plasma jet produced by a 15kW arc plasma torch to the surface of the molten silicon for 15min, the plasma gas being Ar-H 2 Mixed gas, Ar-H 2 The volume fraction of Ar in the mixed gas is 70 percent, and the flow rate of the plasma gas is 5.0m 3 H, placing the plasma torch 50mm above the molten silicon, and waiting for the furnace temperature to dropWhen the temperature is as low as room temperature, the graphite crucible is taken out, a sample is cut and sampled by a wire cutting machine, and the sample sending detection result shows that the content of the impurity P is 40ppmw, and the removal rate is 37.50%.
Example 1: a method for reducing iron and removing phosphorus in industrial silicon comprises the following specific steps:
(1) finely grinding industrial silicon with Fe and P contents of 4749ppmw and 64ppmw respectively to obtain industrial silicon powder; wherein the particle size of the industrial silicon powder is 75-106 μm;
(2) Putting 100g of industrial silicon powder obtained in the step (1) into 4mol/LHNO 3 In the solution, stirring and reacting at the temperature of 35 ℃ for 0.5h to remove iron, cleaning and drying to obtain low-iron industrial silicon powder, wherein the content of impurity Fe in the low-iron industrial silicon powder is reduced to 2655 ppmw; wherein HNO 3 The liquid-solid ratio mL/g of the solution to the industrial silicon powder is 2: 1;
(3) placing the low-iron industrial silicon powder obtained in the step (2) into a vacuum induction furnace provided with a plasma torch, and carrying out induction heating on the industrial silicon powder to a molten state under a vacuum condition to obtain molten silicon;
(4) guiding plasma jet flow generated by a 13kW arc plasma torch to the surface of the molten silicon in the step (3) for chemical smelting for 5min, injecting plasma gas with 100% Ar of components, wherein the flow rate of the plasma gas is 4.0m 3 The plasma torch is placed 20mm above the molten silicon, the plasma jet flow stirs the molten silicon to generate a high temperature point, and phosphorus volatilizes and escapes from the molten silicon to obtain low-phosphorus molten silicon;
(5) cooling the low-phosphorus molten silicon to room temperature along with the furnace to obtain a silicon ingot, and removing scum on the surface of the silicon ingot to obtain low-phosphorus industrial silicon; the sample sending detection result shows that the content of the impurity P is 31ppmw, and the removal rate is 51.56%.
Example 2: a method for reducing iron and removing phosphorus in industrial silicon comprises the following specific steps:
(1) finely grinding industrial silicon with Fe and P contents of 4749ppmw and 64ppmw respectively to obtain industrial silicon powder; wherein the particle size of the industrial silicon powder is 250-1000 μm;
(2) Putting 100g of the industrial silicon powder obtained in the step (1) into a 4mol/LHCl solution, stirring and reacting at the temperature of 45 ℃ to remove iron for 2h, cleaning and drying to obtain low-iron industrial silicon powder, wherein the content of Fe impurity in the low-iron industrial silicon powder is reduced to 2034 ppmw; wherein the liquid-solid ratio mL/g of the HCl solution to the industrial silicon powder is 3: 1;
(3) placing the low-iron industrial silicon powder obtained in the step (2) into a vacuum induction furnace provided with a plasma torch, and carrying out induction heating on the industrial silicon powder to a molten state under a vacuum condition to obtain molten silicon;
(4) guiding plasma jet generated by a 14kW arc plasma torch to the surface of the molten silicon in the step (3) for chemical smelting for 10min, wherein the injection component is 95% Ar + 5% O 2 (volume fraction) of plasma gas having a flow rate of 6.0m 3 The plasma torch is placed 30mm above the molten silicon, the plasma jet flow stirs the molten silicon to generate a high temperature point, and phosphorus volatilizes and escapes from the molten silicon to obtain low-phosphorus molten silicon;
(5) cooling the low-phosphorus molten silicon to room temperature along with the furnace to obtain a silicon ingot, and removing scum on the surface of the silicon ingot to obtain low-phosphorus industrial silicon; the sample sending detection result shows that the content of the impurity P is 22ppmw, and the removal rate is 65.63%.
Example 3: a method for reducing iron and removing phosphorus in industrial silicon comprises the following specific steps:
(1) Finely grinding industrial silicon with Fe and P contents of 4749ppmw and 64ppmw respectively to obtain industrial silicon powder; wherein the particle size of the industrial silicon powder is 75-106 μm;
(2) putting 100g of the industrial silicon powder obtained in the step (1) into a mixed acid solution of 4mol/LHCl +1mol/LHF, stirring and reacting at 65 ℃ to remove iron for 6 hours, cleaning and drying to obtain low-iron industrial silicon powder, wherein the content of impurity Fe in the low-iron industrial silicon powder is reduced to 343 ppmw; wherein the liquid-solid ratio mL/g of the mixed acid solution to the industrial silicon powder is 4: 1;
(3) placing the low-iron industrial silicon powder obtained in the step (2) into a vacuum induction furnace provided with a plasma torch, and carrying out induction heating on the industrial silicon powder to a molten state under a vacuum condition to obtain molten silicon;
(4) guiding plasma jet generated by a 15kW arc plasma torch to the surface of the molten silicon in the step (3) for chemical smelting for 15min, wherein the injection component is 70% Ar + 30% H 2 (volume fraction) of plasma gas having a flow rate of 5.0m 3 H, the plasma torch is placed 50mm above the molten silicon and the plasma jet agitates the molten silicon to create a high temperature spot for the phosphorusVolatilizing the silicon melt to escape from the silicon melt to obtain low-phosphorus molten silicon;
(5) cooling the low-phosphorus molten silicon to room temperature along with the furnace to obtain a silicon ingot, and removing scum on the surface of the silicon ingot to obtain low-phosphorus industrial silicon; the sample sending detection result shows that the content of the impurity P is 7ppmw, and the removal rate is 89.06%.
Example 4: a method for reducing iron and removing phosphorus in industrial silicon comprises the following specific steps:
(1) finely grinding industrial silicon with Fe and P contents of 4749ppmw and 64ppmw respectively to obtain industrial silicon powder; wherein the particle size of the industrial silicon powder is 106-150 mu m;
(2) putting 100g of industrial silicon powder obtained in the step (1) into aqua regia, stirring and reacting at 55 ℃ for 4 hours to remove iron, cleaning and drying to obtain low-iron industrial silicon powder, wherein the content of impurity Fe in the low-iron industrial silicon powder is reduced to 1519 ppmw; wherein the liquid-solid ratio mL/g of the aqua regia solution to the industrial silicon powder is 5: 1;
(3) placing the low-iron industrial silicon powder obtained in the step (2) into a vacuum induction furnace provided with a plasma torch, and carrying out induction heating on the industrial silicon powder to a molten state under a vacuum condition to obtain molten silicon;
(4) guiding plasma jet generated by a 16kW arc plasma torch to the surface of the molten silicon in the step (3) for chemical smelting for 20min, wherein the injection component is 95% Ar + 5% H 2 (volume fraction) of plasma gas having a flow rate of 7.0m 3 The plasma torch is placed 40mm above the molten silicon, the plasma jet flow stirs the molten silicon to generate a high temperature point, and phosphorus volatilizes and escapes from the molten silicon to obtain low-phosphorus molten silicon;
(5) cooling the low-phosphorus molten silicon to room temperature along with the furnace to obtain a silicon ingot, and removing scum on the surface of the silicon ingot to obtain low-phosphorus industrial silicon; the sample sending detection result shows that the content of the impurity P is 18ppmw, and the removal rate is 71.88%.
Example 5: a method for reducing iron and removing phosphorus in industrial silicon comprises the following specific steps:
(1) finely grinding industrial silicon with Fe and P contents of 4749ppmw and 64ppmw respectively to obtain industrial silicon powder; wherein the particle size of the industrial silicon powder is not more than 75 μm;
(2) putting 100g of industrial silicon powder obtained in the step (1) into 4mol/LHNO 3 +1mol/LHF mixtureIn the synthetic acid, stirring and reacting at the temperature of 75 ℃ for 8 hours to remove iron, cleaning and drying to obtain low-iron industrial silicon powder, wherein the content of impurity Fe in the low-iron industrial silicon powder is reduced to 949 ppmw; wherein the liquid-solid ratio mL/g of the mixed acid to the industrial silicon powder is 6: 1;
(3) placing the low-iron industrial silicon powder obtained in the step (2) into a vacuum induction furnace provided with a plasma torch, and carrying out induction heating on the industrial silicon powder to a molten state under a vacuum condition to obtain molten silicon;
(4) guiding plasma jet generated by a 15kW arc plasma torch to the surface of the molten silicon in the step (3) for chemical smelting for 15min, wherein the injection component is 95% Ar + 5% H 2 (volume fraction) of plasma gas having a flow rate of 5.0m 3 The plasma torch is placed 60mm above the molten silicon, the plasma jet flow stirs the molten silicon to generate a high temperature point, and phosphorus volatilizes and escapes from the molten silicon to obtain low-phosphorus molten silicon;
(5) cooling the low-phosphorus molten silicon to room temperature along with the furnace to obtain a silicon ingot, and removing scum on the surface of the silicon ingot to obtain low-phosphorus industrial silicon; the sample sending detection result shows that the content of the impurity P is 14ppmw, and the removal rate is 78.13%.
While the present invention has been described in detail with reference to the specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention.
Claims (6)
1. A method for reducing iron and removing phosphorus of industrial silicon is characterized by comprising the following specific steps:
(1) finely grinding industrial silicon to obtain industrial silicon powder;
(2) putting the industrial silicon powder obtained in the step (1) into an acid solution, stirring for reaction, removing iron, cleaning and drying to obtain low-iron industrial silicon powder; wherein the acid solution is HNO 3 HCl, aqua regia, HNO 3 -HF mixed acid or HCl-HF mixed acid;
(3) placing the low-iron industrial silicon powder obtained in the step (2) into a vacuum induction furnace provided with a plasma torch, and carrying out induction heating on the industrial silicon powder to a molten state under a vacuum condition to obtain molten silicon;
(4) guiding the plasma jet induced by the electric arc to the surface of the molten silicon in the step (3) for chemical smelting, stirring the molten silicon by the plasma jet to generate a high temperature point, and volatilizing phosphorus to escape from the molten silicon to obtain low-phosphorus molten silicon; wherein the plasma gas is Ar or Ar-O 2 Mixed gas or Ar-H 2 Mixing gas; Ar-O 2 The volume fraction of Ar in the mixed gas is 95 percent, and Ar-H 2 The volume fraction of Ar in the mixed gas is 70% or 95%;
(5) and (4) cooling the low-phosphorus molten silicon to room temperature along with the furnace to obtain a silicon ingot, and removing scum on the surface of the silicon ingot to obtain the low-phosphorus industrial silicon.
2. The method for reducing iron and removing phosphorus in industrial silicon according to claim 1, wherein: the particle size of the industrial silicon powder in the step (1) is not more than 1000 μm.
3. The method for reducing iron and removing phosphorus in industrial silicon according to claim 2, characterized in that: the particle size of the industrial silicon powder is 250-1000 μm, 150-250 μm, 106-150 μm, 75-106 μm or less than 75 μm.
4. The method for reducing iron and removing phosphorus in industrial silicon according to claim 1, wherein: HNO 3 The concentration is 2-6 mol/L, the HCl concentration is 2-6 mol/L, HNO 3 HNO in HF mixed acid 3 The concentration is 1-5 mol/L, HF and 1-5 mol/L, and the concentration of HCl in the HCl-HF mixed acid is 1-5 mol/L, HF and 1-5 mol/L.
5. The method for reducing iron and removing phosphorus in industrial silicon according to claim 1, wherein: the reaction temperature of the step (2) is 35-75 ℃, and the reaction time is 2-8 h; the liquid-solid ratio mL/g of the acid solution to the industrial silicon powder is 2-6: 1.
6. The method for reducing iron and removing phosphorus in industrial silicon according to claim 1, wherein: the power of the plasma generator is 13-16kW, the chemical smelting time of the arc-induced plasma jet is 5-20min, the distance between plasma gas and the molten silicon liquid surface is 20-60 mm, and the gas flow rate is 4.0-7.0m 3 /h。
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| CA1147698A (en) * | 1980-10-15 | 1983-06-07 | Maher I. Boulos | Purification of metallurgical grade silicon |
| JP3138003B2 (en) * | 1991-05-10 | 2001-02-26 | 川崎製鉄株式会社 | Method and apparatus for purifying silicon |
| CN100372762C (en) * | 2006-01-25 | 2008-03-05 | 昆明理工大学 | Method for preparing solar grade polysilicon |
| CN101007633A (en) * | 2006-12-15 | 2007-08-01 | 佟新廷 | Silicon preparation method of PV industry |
| CN101239723A (en) * | 2007-02-07 | 2008-08-13 | 北京明远通科技有限公司 | Plasma producing method and device for polycrystalline silicon |
| KR101178590B1 (en) * | 2009-06-10 | 2012-08-30 | 한국세라믹기술원 | Manufacturing Method For Silicon Ingot |
| CN102040221A (en) * | 2009-10-13 | 2011-05-04 | 上海太阳能科技有限公司 | Method for purifying metal silicon |
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| 真空感应熔炼和定向凝固提纯冶金级硅研究;冀明;《中国优秀博硕士学位论文全文数据库（信息科技辑）》;20110915(第9期);全文 * |
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