CN103420378A - Slag former for smelting polycrystalline silicon medium and use method of slag former - Google Patents

Slag former for smelting polycrystalline silicon medium and use method of slag former Download PDF

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CN103420378A
CN103420378A CN2013103379301A CN201310337930A CN103420378A CN 103420378 A CN103420378 A CN 103420378A CN 2013103379301 A CN2013103379301 A CN 2013103379301A CN 201310337930 A CN201310337930 A CN 201310337930A CN 103420378 A CN103420378 A CN 103420378A
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slag former
silicon
slag
medium
silicon liquid
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CN103420378B (en
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谭毅
李佳艳
张磊
李亚琼
王登科
姜大川
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Dalian University of Technology
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Dalian University of Technology
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Abstract

The invention discloses a slag former for smelting a polycrystalline silicon medium and a use method of the slag former. The slag former is formed by mixing the following raw materials by weight: 30%-60% of Na2SiO3, 20%-50% of SiO2, 1%-15% of TiO2 and 1%-5% of Al2O3. The slag former is added in a process of smelting and purifying the polycrystalline silicon medium, so that the partition coefficient LB value of boron in the slag former and a silicon solution is effectively increased by 1-2 from 2-4, the boron removal effect is improved, and the boron content of a silicon material is reduced to be less than 0.20 ppmw.

Description

Slag former and using method thereof for a kind of polycrystalline silicon medium melting
Technical field
The invention belongs to polycrystalline silicon medium melting field, be specifically related to slag former and using method thereof for a kind of polycrystalline silicon medium melting.
Background technology
World today's energy dilemma and environmental pollution pressure are also deposited, and people are badly in need of cleaning, safety, continuable new forms of energy.Sun power, as meeting the energy required like this, always is the target that people pursue.People are the utilizations of its heat effect to the use of sun power the earliest, but are difficult to meet fully the needs of modern society.Until the discovery of photoresistance, the manufacture of solar cell, people find sun power new utilize mode.Silicon is as the desirable feedstock of solar cell, impurity wherein mainly contains metallic impurity and the nonmetallic impuritys such as B, P such as Fe, Al, Ca, and these impurity elements can reduce the Compound Degree of silicon crystal grain interface photo-generated carrier, and the Compound Degree of photo-generated carrier has determined the photoelectric transformation efficiency of solar cell, so effectively remove these impurity, in the application facet of solar cell, vital effect is arranged.
The development of photovoltaic industry depends on the purification to the silicon raw material, in the process of polycrystalline silicon purifying, comprises that medium melting, directional freeze, electron beam purify and casting ingot process.Metallurgy method has development potentiality because possessing simple, the lower-cost advantage of technique.In all multi-methods, with slag practice, require equipment the simplest, the easiest industrialization promotion.Thereby researching value and the application prospect of the tool reality of medium melting.
Partition ratio has reflected transfer ability and the separation efficiency of solute in two-phase.The ratio of the massfraction of boron in the slag agent and massfraction in silicon liquid, the boron partition ratio, is used L BMean.After the de-boron of its explanation slag agent, the allocation proportion that boron reaches between slag agent and silicon liquid.At present, have the actual allocated coefficient L of slag system both at home and abroad now BLower, numerical value 2-4, thus mean that it is not very desirable removing effect of boron.
Summary of the invention
The purpose of this invention is to provide slag former and using method thereof for a kind of polycrystalline silicon medium melting, can effectively improve boron partition ratio L B, improve except effect of boron.
Technical scheme of the present invention is as follows:
A kind of slag former, by weight percentage, mixed by following raw material: Na 2SiO 330%～60%, SiO 220%～50%, TiO 21%～15% and Al 2O 31%～5%.
Described slag former, take each raw material by proportioning raw materials and mix and can make.
The present invention also provides the using method of a kind of slag former in the polycrystalline silicon medium melting, and the method comprises slag former is joined to the step of carrying out the medium melting in silicon liquid, and described slag former is slag former provided by the present invention.
In above-mentioned using method, the mass ratio of described slag former and silicon liquid is preferably 0.3～1.2:1.
The using method of a kind of slag former of the present invention in the polycrystalline silicon medium melting, optimal technical scheme comprises the steps:
(1) the silicon material is joined in smelting pot, adopt medium-frequency induction furnace to be heated to the silicon material and all be fused into silicon liquid;
(2) slag former is joined in mixer and mixes according to the raw material composition;
(3) slag former mixed joins in the silicon liquid of step (1), is heated to slag former and all melts, and carries out the medium melting;
(4) after the medium melting finishes, the slag that floats over bath surface is all poured out;
(5) repeating step (3)～(4) is 2～4 times, and the silicon liquid obtained pours into cooled and solidified in mould.
In the technical scheme of above-mentioned using method:
Preferably adopt following scheme in described step (1): the silicon material is added in plumbago crucible, adopt medium-frequency induction furnace hoisting power to 50～250kW, through 30～80min, make the silicon material all be fused into silicon liquid.
In described step (2), mixing time is preferably 5～20min.
In described step (3), the mass ratio of slag former and silicon liquid is preferably 0.3～1.2:1.
In described step (3) can by the slag former after mixing is disposable add after, keep induction furnace power 30～150kW heat temperature raising, after melt upper surface temperature reaches 1650～1750 ℃, be incubated 20～60min and carry out the medium melting; Also the slag former after mixing can be divided into to 4～10 parts, interval 10～20min adds successively, keep induction furnace power 50～200kW, after adding fully, keep induction furnace power 30～150kW heat temperature raising, after melt upper surface temperature reaches 1650～1750 ℃, be incubated 20～60min and carry out the medium melting.
Preferably adopt following scheme in described step (4): after the medium melting finishes, control 1500 ± 20 ℃ of slags that will float over bath surface of temperature and all pour out.
In described step (5), after the liquid cooling of gained silicon is but solidified, through ICP-MS, measure its boron content, adopt the silicon material of Methods For Purification of the present invention, its boron content is below 0.20ppmw.
Beneficial effect of the present invention: TiO in (1) slag former 2And Al 2O 3Add, can be by boron the partition ratio L in slag agent and silicon liquid BNumerical value has effectively improved 1～2 from 2～4, improves except effect of boron; (2) in polycrystalline silicon medium melting purification process, gradation adds slag former, effectively improves the utilization ratio of slag former more than 35%.(3) adopt slag former of the present invention and using method purified silicon material, the boron content of silicon material can be reduced to below 0.20ppmw.
Embodiment
Following non-limiting example can make those of ordinary skill in the art more fully understand the present invention, but does not limit the present invention in any way.
Embodiment 1
A kind of slag former, by weight percentage, mixed by following raw material: Na 2SiO 360%, SiO 220%, TiO 215% and Al 2O 35%.
Described slag former can be used when the medium smelting polycrystalline silicon purifying, described slag former add the partition ratio L in slag agent and silicon liquid by boron BNumerical value effectively brings up to 3.8, improves except effect of boron, and concrete using method comprises the steps:
(1) 100kg silicon material is joined in plumbago crucible, adopt the medium-frequency induction furnace hoisting power to 150W, through 60min, make the silicon material all be fused into silicon liquid;
(2) slag former is joined in mixer and mixes according to the raw material composition, mixing time 10min;
(3) slag former after getting 50kg and mixing, in the disposable silicon liquid that joins step (1), keep induction furnace power 100kW heat temperature raising, and after melt upper surface temperature reaches 1650 ℃, insulation 35min carries out the medium melting;
(4), after the medium melting finishes, control 1500 ± 20 ℃ of slags that will float over bath surface of temperature and all pour out;
(5) repeating step (3)～(4) is 2 times, and the silicon liquid obtained pours into cooled and solidified in mould, obtains the polysilicon 78kg of refining, through ICP-MS, polysilicon is carried out to 3～5 measurements and averages, and wherein boron (B) content is 0.12ppmw.
Embodiment 2
A kind of slag former, by weight percentage, mixed by following raw material: Na 2SiO 360%, SiO 220%, TiO 215% and Al 2O 35%.
Described slag former can be used when the medium smelting polycrystalline silicon purifying, described slag former add the partition ratio L in slag agent and silicon liquid by boron BNumerical value effectively brings up to 4.3, improves except effect of boron, and concrete using method comprises the steps:
(1) 100kg silicon material is joined in plumbago crucible, adopt the medium-frequency induction furnace hoisting power to 150W, through 60min, make the silicon material all be fused into silicon liquid;
(2) slag former is joined in mixer and mixes according to the raw material composition, mixing time 10min;
(3) slag former after getting 30kg and mixing, be divided into 3 parts, and interval 10min joins in the silicon liquid of step (1) successively, keeps induction furnace power 100kW heat temperature raising, and after melt upper surface temperature reaches 1650 ℃, insulation 35min carries out the medium melting;
(4), after the medium melting finishes, control 1500 ± 20 ℃ of slags that will float over bath surface of temperature and all pour out;
(5) repeating step (3)～(4) is 2 times, and the silicon liquid obtained pours into cooled and solidified in mould, obtains the polysilicon 78kg of refining, through ICP-MS, polysilicon is carried out to 3～5 measurements and averages, and wherein boron (B) content is 0.1ppmw.
Embodiment 3
A kind of slag former, by weight percentage, mixed by following raw material: Na 2SiO 330%, SiO 250%, TiO 215% and Al 2O 35%.
Described slag former can be used when the medium smelting polycrystalline silicon purifying, described slag former add the partition ratio L in slag agent and silicon liquid by boron BNumerical value effectively brings up to 4.7, improves except effect of boron, and concrete using method comprises the steps:
(1) 100kg silicon material is joined in plumbago crucible, adopt the medium-frequency induction furnace hoisting power to 100kW, through 80min, make the silicon material all be fused into silicon liquid;
(2) slag former is joined in mixer and mixes according to the raw material composition, mixing time 15min;
(3) slag former after getting 100kg and mixing, be divided into 10 parts, and interval 15min joins in the silicon liquid of step (1) successively, keep induction furnace power 50kW, after adding fully, keep induction furnace power 50kW, after melt upper surface temperature reaches 1700 ℃, insulation 60min carries out the medium melting;
(4), after the medium melting finishes, control 1500 ± 20 ℃ of slags that will float over bath surface of temperature and all pour out;
(5) repeating step (3)～(4) is 3 times, and silicon liquid pours into cooled and solidified in mould, obtains the polysilicon 82kg of refining, through ICP-MS, polysilicon is carried out to 3～5 measurements and averages, and wherein boron (B) content is 0.15ppmw.
Embodiment 4
A kind of slag former, by weight percentage, mixed by following raw material: Na 2SiO 350%, SiO 245%, TiO 21% and Al 2O 34%.
Described slag former can be used when the medium smelting polycrystalline silicon purifying, described slag former add the partition ratio L in slag agent and silicon liquid by boron BNumerical value effectively brings up to 4.5, improves except effect of boron, and concrete using method comprises the steps:
(1) 100kg silicon material is joined in plumbago crucible, adopt the medium-frequency induction furnace hoisting power to 200kW, through 40min, make the silicon material all be fused into silicon liquid;
(2) slag former is joined in mixer and mixes according to the raw material composition, mixing time 20min;
(3) slag former after getting 30kg and mixing, be divided into 6 parts, and interval 10min adds successively, keeps induction furnace power 200kW, after adding fully, keeps induction furnace power 150kW, and after melt upper surface temperature reaches 1750 ℃, insulation 20min carries out the medium melting;
(4), after the medium melting finishes, control 1500 ± 20 ℃ of slags that will float over bath surface of temperature and all pour out;
(5) repeating step (3)～(4) is 4 times, and silicon liquid pours into cooled and solidified in mould, obtains the polysilicon 80kg of refining, through ICP-MS, polysilicon is carried out to 3～5 measurements and averages, and wherein boron (B) content is 0.19ppmw.
Embodiment 5
A kind of slag former, by weight percentage, mixed by following raw material: Na 2SiO 340%, SiO 248%, TiO 210% and Al 2O 32%.
Described slag former can be used when the medium smelting polycrystalline silicon purifying, described slag former add the partition ratio L in slag agent and silicon liquid by boron BNumerical value effectively brings up to 5.3, improves except effect of boron, and concrete using method comprises the steps:
(1) 100kg silicon material is joined in plumbago crucible, adopt the medium-frequency induction furnace hoisting power to 250kW, through 30min, make the silicon material all be fused into silicon liquid;
(2) slag former is joined in mixer and mixes according to the raw material composition, mixing time 10min;
(3) slag former after getting 70kg and mixing, be divided into 7 parts, and interval 15min adds successively, keeps induction furnace power 250kW, after adding fully, keeps induction furnace power 100kW, and after melt upper surface temperature reaches 1700 ℃, insulation 30min carries out the medium melting;
(4), after the medium melting finishes, control 1500 ± 20 ℃ of slags that will float over bath surface of temperature and all pour out;
(5) repeating step (3)～(4) is 2 times, and silicon liquid pours into cooled and solidified in mould, obtains the polysilicon 86kg of refining, through ICP-MS, polysilicon is carried out to 3～5 measurements and averages, and wherein boron (B) content is 0.18ppmw.

Claims (10)

1. a slag former, is characterized in that, by weight percentage, by following raw material, mixed: Na 2SiO 330%～60%, SiO 220%～50%, TiO 21%～15% and Al 2O 31%～5%.
2. the using method of a slag former in the polycrystalline silicon medium melting, the method comprises slag former is joined to the step of carrying out the medium melting in silicon liquid, it is characterized in that, described slag former is slag former claimed in claim 1.
3. using method according to claim 2, described method comprises the steps:
(1) the silicon material is joined in smelting pot, adopt medium-frequency induction furnace to be heated to the silicon material and all be fused into silicon liquid;
(2) slag former is joined in mixer and mixes according to the raw material composition;
(3) slag former mixed joins in the silicon liquid of step (1), is heated to slag former and all melts, and carries out the medium melting;
(4) after the medium melting finishes, the slag that floats over bath surface is all poured out;
(5) repeating step (3)～(4) is 2～4 times, and the silicon liquid obtained pours into cooled and solidified in mould.
4. using method according to claim 3, is characterized in that, described step joins the silicon material in smelting pot in (1), adopts medium-frequency induction furnace hoisting power to 50～250kW, through 30～80min, makes the silicon material all be fused into silicon liquid.
5. using method according to claim 3, is characterized in that, in described step (2), mixing time is 5～20min.
6. using method according to claim 3, is characterized in that, in described step (3), the mass ratio of slag former and silicon liquid is 0.3～1.2:1.
7. using method according to claim 3, it is characterized in that, in described step (3) by the slag former after mixing is disposable join silicon liquid after, keep induction furnace power 30～150kW heat temperature raising, after melt upper surface temperature reaches 1650～1750 ℃, be incubated 20～60min and carry out the medium melting.
8. using method according to claim 3, it is characterized in that, in described step (3), the slag former after mixing is divided into to 4～10 parts, interval 10～20min joins in silicon liquid successively, keep induction furnace power 50～200kW, after adding fully, keep induction furnace power 30～150kW heat temperature raising, after melt upper surface temperature reaches 1650～1750 ℃, be incubated 20～60min and carry out the medium melting.
9. using method according to claim 3, is characterized in that, after described step (4) medium melting finishes, controls 1500 ± 20 ℃ of temperature, and the slag that floats over bath surface is all poured out.
10. using method according to claim 3, is characterized in that, described in step (1), smelting pot is plumbago crucible.
CN201310337930.1A 2013-08-05 2013-08-05 Slag former for smelting polycrystalline silicon medium and use method of slag former Expired - Fee Related CN103420378B (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4124410A (en) * 1977-11-21 1978-11-07 Union Carbide Corporation Silicon solar cells with low-cost substrates
CN101955186A (en) * 2010-09-19 2011-01-26 江西盛丰新能源科技有限公司 Method for preparing polycrystalline silicon by physically removing boron
CN102259865A (en) * 2011-06-01 2011-11-30 宁夏银星多晶硅有限责任公司 Slag washing process for removing boron from metallurgical polycrystalline silicon
CN103072994A (en) * 2013-02-04 2013-05-01 福建兴朝阳硅材料股份有限公司 Electrophoretic assistant slag forming and boron removing method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4124410A (en) * 1977-11-21 1978-11-07 Union Carbide Corporation Silicon solar cells with low-cost substrates
CN101955186A (en) * 2010-09-19 2011-01-26 江西盛丰新能源科技有限公司 Method for preparing polycrystalline silicon by physically removing boron
CN102259865A (en) * 2011-06-01 2011-11-30 宁夏银星多晶硅有限责任公司 Slag washing process for removing boron from metallurgical polycrystalline silicon
CN103072994A (en) * 2013-02-04 2013-05-01 福建兴朝阳硅材料股份有限公司 Electrophoretic assistant slag forming and boron removing method

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