CN102139878B - Method for removing boron impurity from industrial silicon by using titanium-containing compound - Google Patents
Method for removing boron impurity from industrial silicon by using titanium-containing compound Download PDFInfo
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- CN102139878B CN102139878B CN 201110040914 CN201110040914A CN102139878B CN 102139878 B CN102139878 B CN 102139878B CN 201110040914 CN201110040914 CN 201110040914 CN 201110040914 A CN201110040914 A CN 201110040914A CN 102139878 B CN102139878 B CN 102139878B
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- containing compound
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Abstract
The invention provides a method for removing a boron impurity from industrial silicon by using a titanium-containing compound and belongs to the field of metallurgy. The method comprises the following steps of: mixing the industrial silicon and a slag forming constituent, adding the mixture into a graphite crucible and pre-heating the graphite crucible in a smelting furnace to the temperature of between 1,400 and 1,600 DEG C; vacuumizing the smelting furnace with a mechanical pump and a Roots pump in turn, heating the smelting furnace to the temperature of between 1,500 and 1,700 DEG C and controlling the frequency of a medium frequency power supply to between 80 and 120kW; and introducing gas into the smelting furnace, stirring, forming slag, pouring silicon liquid into a die after the slag is fully formed, and cutting impurities from the solidified silicon material to obtain the silicon material from which boron is removed. The slag forming constituent used in the method has a good effect; the distribution ratio can be over 5; and compared with the distribution ratio of a pure Ca slag forming constituent, the distribution ratio of the slag forming constituent is obviously improved. The content of the boron in the industrial silicon is obviously reduced. The method has a wide application prospect.
Description
Technical field
The present invention relates to the boron removal method of industrial silicon, be specifically related to a kind of method that adopts titanium-containing compound to remove boron from industrial silicon impurity.
Background technology
Sun power has advantages of that cleaning, reserves enrich.The annual sun power that receives is equivalent to solid, gas, liquid fuel approximately 3.5 ten thousand times of annual burning on the present earth on the earth, and how effectively utilizing sun power is scientific research hot issue for a long time.Wherein, utilizing the photovoltaic effect, is the solar battery technology of electric energy with light energy conversion, is to solve day by day one of the effective way of the energy problem of crisis of the earth.
Solar-grade polysilicon is the raw material of producing solar-energy photo-voltaic cell, and its production cost is the important factor of restriction photovoltaic industry always.At present, the main using modified Siemens Method of European and American countries is produced solar-grade polysilicon, yet this process energy consumption is large, and cost is high, and a large amount of liquid chlorine, hydrogen that use exist huge safety and environment hidden danger in process of production.Under the dual-pressure of cost and environmental protection, metallurgy method is produced solar-grade polysilicon technique and is arisen at the historic moment.Its technical process mainly comprises: the operations such as hydrometallurgy, air blowing, slag making, vacuum melting, directional freeze, be intended to by a series of concerned process steps, set out take the industrial silicon of purity as 99% as raw material, by removing impurity element in the silicon, obtain the solar-grade polysilicon (SoG-Si) of purity more than 5N, and for the manufacture of solar cell.
Boron, phosphorus are the important doped elements in the solar-energy photo-voltaic cell, and its content has great effect to the battery efficiency of solar cell.In order to reach electricity conversion at the solar cell more than 10%, in the world the boron content concn there is the requirement that is lower than 0.5ppmw, phosphorus content is required to be lower than 1ppmw.
Suzuki and the Sano (1 of Japan, Suzuki, Sano.Thermodynamics for removal of boron frommetallurgical silicon by flux treatment of molten silicon[C] .The 10th European Photovoltaic SolarEnergy Conference In Lisbon, 1991, Portugal 8-12), the Viana Teixeira of Tokyo Univ Japan and Kazuki Morita (2, Leandro Augusto Viana Teixeira and Kazuki Morital, Removal of Boron from Molten SiliconUsing CaO-SiO
2Based Slags, ISIJ International, 2009,49 (6): 783-787), the people such as the Wang Xinguo of Shanghai University (3, Wang Xinguo, Ding Weizhong, Tang Kai, Deng. the thermodynamic study of silicon alloy oxidation refining process [J]. the China YouSe Acta Metallurgica Sinica, 2001,11 (3): 503-509), the people such as C.Alemany (4 of France, DELANNOYY, ALEMANY C, LI K I, etal.Plasma-refining process to provide solar-grade silicon[J] .Solar Energy Materials and SolarCells, 2002,72 (1-4): 69-75) all removing phosphorus, certain work has been carried out in the element aspects such as boron, and makes some progress.
Aspect the removal phosphoric, Xiamen University's metallurgical laboratory has carried out large quantity research and experiment, and verified at 1600 ℃, electromagnetic induction melting 1h under 0.012～0.035Pa, can with the phosphorus impurities in the silicon from 15ppmw be reduced to 0.08ppmw (5, Zheng Songsheng, Luo Xuetao etc., the progress of polysilicon metallurgy method dephosphorization, material Leader [J], 2009,23 (10), 11-14).
For the boron impurity of removing in the industrial silicon, applying in a large number the method that metallurgy method prepares in the solar-grade polysilicon technique at present is slag refining.By adding slag former, in solution, form the slag phase.By Theoretical Calculation and experimental verification, the segregation coefficient of the oxide compound of boron in slag phase and silicon is far smaller than the segregation coefficient of boron in silicon, and Xiamen University's metallurgical laboratory adopts CaO-SiO
2-CaF
2The pilot plant test of-BaO slag making system shows, slag silicon than 1650～1750 ℃ of lower successes in 2: 1～2: 1, temperature with boron content to 0.15～0.7ppmw (6, Cai Jing, Luo Xuetao etc., high-purity metalluragical silicon is except the progress of boron, material Leader [J], 2009,23 (12): 81-84).
Summary of the invention
The object of the present invention is to provide a kind of method that adopts titanium-containing compound to remove boron from industrial silicon impurity.
Described a kind of method that adopts titanium-containing compound to remove boron from industrial silicon impurity may further comprise the steps:
1) with industrial silicon and slag former in mass ratio 1: mix (1～15), and its compressing tablet is got sheet material;
2) sheet material is put into plumbago crucible, place smelting furnace to be preheated to 1400～1600 ℃;
3) with mechanical pump, lobe pump smelting furnace is evacuated to below the 10Pa successively, passes into again argon gas to 9000～11000Pa;
4) start intermediate frequency power supply sheet material is heated to 1500～1700 ℃, control intermediate frequency power supply power is 80～120kW;
5) carry out aeration-agitation and slag making in the silicon liquid after venting pin being inserted sheet material and melting, the condition of ventilation is: Ventilation Rate 1.5～3L/min, aeration time 10～300min;
6) with step 5) silicon liquid after the slag making pours in the mould, and the silicon material furnace cooling after solidifying takes out the silicon material after the cooling, laterally excise the more part of silicon material top 10% foreign matter content, namely gets except the silicon material behind the boron, measures wherein boron impurity content.
In step 1) in, described slag former can be TiO
2-CaF
2-SiO
2Slag former etc., described TiO
2-CaF
2-SiO
2The composition of slag former can be by mass percentage: TiO
2Be 17%～38%, preferred 21%～35%, be preferably 21%～26%; CaF
2Be 15%～30%, preferred 15%～25%, be preferably 16%～23%; Remaining is SiO
2The mass ratio of described industrial silicon and slag former preferred 1: (1～10) is preferably 1: (1～5).
In step 4) in, described intermediate frequency power supply power is preferably 85～115kW, is preferably 90～100kW.
In step 5) in, the condition optimization of described ventilation is: Ventilation Rate 2～2.5L/min, aeration time 30～100min; Described venting pin preferably stretches in the silicon liquid with 45 ° of inclination angles; The time of described slag making can be 10～80min.
Slag former among the present invention selects titanium dioxide and Fluorspar Powder as raw material, greatly reduces the cost of slag former, and simultaneously its slag making is respond well, and partition ratio can reach more than 5, and contrasting simple Ca is that slag former is significantly increased.Icp analysis is the result show, boron content is reduced to below the 0.5ppmw from 50 original～100ppmw, reached the requirement of producing solar cell.Such slag former is with low cost, stable chemical nature, environmentally safe, can be applied to large-scale industrialization and produce solar-grade polysilicon (SoG-Si).The present invention proposes the slagging process that adds titanium dioxide, Fluorspar Powder in the industrial silicon, the technique of removing boron from industrial silicon impurity has been carried out theory and experimental verification.Through great many of experiments, the optimum value of checking key variables has finally been determined the setting range of the key parameters such as slag silicon ratio, monitor system, temperature of reaction, reaction times, draft speed, time of this technique.Significantly reduced boron from industrial silicon content, had broad application prospects.
Embodiment
The present invention can make slag former as raw material with titanium dioxide, Fluorspar Powder, silicon-dioxide, and its effective constituent is TiO
2, CaF
2, SiO
2Gibbs free energy change scale by the calculational chemistry reaction is bright, and in slagging process, the boron in the Pure Silicon Metal can be by TiO
2And SiO
2Oxidation, boron oxide is at TiO
2-CaF
2-SiO
2Solid solubility is higher in the slag system, thereby the trend that enters slag system by diffusion is arranged; Simultaneously, learn that by Phase Diagram Analysis at high temperature easy and boron reaction of Ti generates TiB
2Deng compound.In view of above two kinds of reaction mechanisms, by compressing tablet in technological process process, improve temperature, the mode such as blow in the solution accelerates speed of reaction to be able to apply to the efficient of suitability for industrialized production, finishes the target of removing boron impurity from industrial silicon.
Embodiment 1
1) getting titanium dioxide, Fluorspar Powder, silicon-dioxide is that raw material is by TiO
2(20%wt)-CaF
2(15%wt)-SiO
2Ratio (65%wt) altogether 10kg is fully mixed, and makes slag former.
2) more above-mentioned slag former is fully mixed with the 150kg industrial silicon, then compressing tablet is processed.With tabletting machine 10 * 10
6The 50s that pressurizes under the Pa, making diameter is 80mm, and thickness is the cylindrical sheet of 30mm, and every tablet quality is 300g.
3) material behind the compressing tablet is carried out thermal pretreatment, preheating temperature is controlled at 1400 ℃, then successively with vacuum pump, lobe pump stove is vacuumized.
4) be evacuated to pressure and be lower than 10Pa after, in stove, pass into argon gas with venting pin, air blowing speed is 1.5L/min, gassing time is 10min, the firm power of control heating in medium frequency is 80kW in the reaction process, the control slag making time is 10min.
Sample is carried out icp analysis, record that boron content is 0.52ppmw in the sample.
Embodiment 2
Technological process is with embodiment 1, and slag former is according to TiO
2(25%wt)-CaF
2(15%wt)-SiO
2(60%wt), it is 1450 ℃ that preparation 30kg changes preheating temperature, and changing air blowing speed is 2L/min, gassing time is 20min, control heating in medium frequency firm power is 90kW in the reaction process, and sample is carried out icp analysis, records that boron content is 0.44ppmw in the sample.
Embodiment 3
Technological process is with embodiment 1, and slag former is according to TiO
2(25%wt)-CaF
2(20%wt)-SiO
2(55%wt) preparation 50kg, changing preheating temperature is 1500 ℃, changing the slag making time is 20min, and sample is carried out icp analysis, records that boron content is 0.41ppmw in the sample.
Embodiment 4
Technological process is with embodiment 1, and slag former is according to TiO
2(25%wt)-CaF
2(20%wt)-SiO
2(55%wt) preparation 100kg, changing air blowing speed is 2.5L/min, and gassing time is 30min, and control heating in medium frequency firm power is 100kW in the reaction process, and changing the slag making time is 40min, and sample is carried out icp analysis, recording boron content is 0.36ppmw.
Embodiment 5
Technological process is with embodiment 1, and slag former is according to TiO
2(30%wt)-CaF
2(20%wt)-SiO
2(50%wt) preparation 150kg, changing preheating temperature is 1450 ℃, and control heating in medium frequency power is 110kW in the reaction process, and changing the slag making time is 50min, and sample is carried out icp analysis, and recording boron content is 0.37ppmw.
Embodiment 6
Technological process is with embodiment 1, and slag former is according to TiO
2(35%wt)-CaF
2(20%wt)-SiO
2(45%wt) preparation 150kg, changing air blowing speed is 2.5L/min, and gassing time is 50min, and changing the slag making time is 60min, and sample is carried out icp analysis, and recording boron content is 0.35ppmw.
Embodiment 7
Technological process is with embodiment 1, and control heating in medium frequency power is 100kW in the reaction process, and changing air blowing speed is 3L/min, and gassing time is 100min, and changing the slag making time is 80min, and sample is carried out icp analysis, and recording boron content is 0.39ppmw.
Claims (6)
1. method that adopts titanium-containing compound to remove boron from industrial silicon impurity is characterized in that may further comprise the steps:
1) industrial silicon is mixed with slag former 1: 1 in mass ratio～5, and its compressing tablet is got sheet material; Described slag former is TiO
2-CaF
2-SiO
2Slag former, its composition is by mass percentage: TiO
2Be 21%～35%, CaF
2Be 15%～25%, remaining is SiO
2
2) sheet material is put into plumbago crucible, place smelting furnace to be preheated to 1400～1600 ℃;
3) with mechanical pump, lobe pump smelting furnace is evacuated to below the 10Pa successively, passes into again argon gas to 10000～11000Pa;
4) start intermediate frequency power supply sheet material is heated to 1500～1700 ℃, control intermediate frequency power supply power is 80～120kW;
5) carry out aeration-agitation and slag making in the silicon liquid after venting pin being inserted sheet material and melting, the condition of ventilation is: Ventilation Rate 1.5～3L/min, aeration time 10～300min;
6) the silicon liquid after the step 5) slag making is fully poured in the mould, the silicon material furnace cooling after solidifying takes out the silicon material after the cooling, laterally excise the more part of silicon material top 10% foreign matter content, namely gets except the silicon material behind the boron.
2. a kind of method that adopts titanium-containing compound to remove boron from industrial silicon impurity as claimed in claim 1 is characterized in that in step 1) described TiO
2-CaF
2-SiO
2The composition of slag former is by mass percentage: TiO
2Be 21%～26%; CaF
2Be 16%～23%; Remaining is SiO
2
3. a kind of method that adopts titanium-containing compound to remove boron from industrial silicon impurity as claimed in claim 1 is characterized in that in step 4), and described intermediate frequency power supply power is 85～115kW.
4. a kind of method that adopts titanium-containing compound to remove boron from industrial silicon impurity as claimed in claim 3 is characterized in that described power is 90～100kW.
5. a kind of method that adopts titanium-containing compound to remove boron from industrial silicon impurity as claimed in claim 1 is characterized in that in step 5), and the condition of described ventilation is: Ventilation Rate 2～2.5L/min, aeration time 30～100min.
6. a kind of method that adopts titanium-containing compound to remove boron from industrial silicon impurity as claimed in claim 1 is characterized in that in the time of slag making described in the step 5) be 10～80min.
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| CN 201110040914 CN102139878B (en) | 2011-02-18 | 2011-02-18 | Method for removing boron impurity from industrial silicon by using titanium-containing compound |
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| CN 201110040914 CN102139878B (en) | 2011-02-18 | 2011-02-18 | Method for removing boron impurity from industrial silicon by using titanium-containing compound |
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| CN102139878B true CN102139878B (en) | 2013-02-06 |
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| CN103072994B (en) * | 2013-02-04 | 2014-04-23 | 福建兴朝阳硅材料股份有限公司 | Electrophoretic assistant slag forming and boron removing method |
| CN103754882B (en) * | 2013-12-27 | 2015-07-08 | 福建兴朝阳硅材料股份有限公司 | Purifying method of slag-making agent with boron removal |
| CN105063749B (en) * | 2015-06-08 | 2017-07-18 | 朱超 | A kind of method for preparing high-purity polycrystalline silicon |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1188035A (en) * | 1997-01-15 | 1998-07-22 | 珠海市万达焊条有限公司 | Low hydrogen type downward continuous welding rod |
| CN101844768A (en) * | 2010-05-20 | 2010-09-29 | 厦门大学 | Method for removing phosphorus and boron from metallurgical-grade silicon |
| CN101870472A (en) * | 2010-02-09 | 2010-10-27 | 厦门大学 | Method for removing impurities of boron and phosphorus in industrial silicon by adopting rare-earth oxide |
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2011
- 2011-02-18 CN CN 201110040914 patent/CN102139878B/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1188035A (en) * | 1997-01-15 | 1998-07-22 | 珠海市万达焊条有限公司 | Low hydrogen type downward continuous welding rod |
| CN101870472A (en) * | 2010-02-09 | 2010-10-27 | 厦门大学 | Method for removing impurities of boron and phosphorus in industrial silicon by adopting rare-earth oxide |
| CN101844768A (en) * | 2010-05-20 | 2010-09-29 | 厦门大学 | Method for removing phosphorus and boron from metallurgical-grade silicon |
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