CN102951645A - Method for removing boron and phosphorus impurity in industrial silicon by slagging refining - Google Patents

Abstract

The invention discloses a method for removing the boron and phosphorus impurity in industrial silicon by slagging refining, and relates to the industrial silicon impurity removal technology. The method comprises the following steps of: 1) coating a compact SiC coating as an inner layer on the surface of a graphite crucible, and coating a Y2O3 coating on the SiC coating as an outer layer; 2) after slagging constituent is mixed, putting into a pre-processed graphite crucible; 3) opening a medium-frequency induction furnace for heating until slag charges are molten; 4) after the slag charges are molten, adding the industrial silicon into the molten slag charges, carrying out slagging refining, and reacting if power is lowered after the slag charges and silicon materials are totally molten; 5) inserting a venting pin into the molten liquid, and introducing Ar+H2O into the system to guarantee that the silicon and the slags are contacted; 6) pulling out the venting pin, and pouring the upper layer of silicon liquid of the molten liquid into a standing graphite module for cooling; 7) continuously adding silicon materials, and repeating steps 4) to 6); and 8) cutting impurity enrichment parts on the tail part and the head part of refined polysilicon, and measuring the content of residual parts of boron and phosphorus by ICP-MS (inductively coupled plasma-mass spectrum). The method has the advantages of simple technology and high industrial feasibility.

Description

A kind of slag refining is removed the method for boron from industrial silicon phosphorus impurities

Technical field

The present invention relates to the impurity removal process of industrial silicon, especially relate to the method that a kind of slag refining is removed the boron from industrial silicon phosphorus impurities.

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 always is the target that people pursue as satisfying the energy that requires like this.People are the utilizations of its heat effect to the use of sun power the earliest, but are difficult to satisfy fully the needs of modern society.Until the discovery of photoresistance, the manufacturing 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, A1, Ca, and these impurity elements can reduce the at the interface Compound Degree of photo-generated carrier of silicon crystal grain, and the Compound Degree of photo-generated carrier has determined the photoelectric transformation efficiency of solar cell, in the application facet of solar cell vital effect is arranged so effectively remove these impurity.

Although the polysilicon purity of improvement siemens method preparation is very high, is difficult to the demand that satisfied in recent years photovoltaic industry develops rapidly.1996 under the support of Japanese new forms of energy and industrial technology development organizations, Kawasaki, Japan Inland Steel processed (Kawasaki steel) has developed the method for utilizing metallurgical technology to produce solar-grade polysilicon, this method is significantly improved than Siemens Method at cost and pollution, its main flow process is: selecting general industry silicon is raw material, utilize the boron impurity in the plasma melting removal silicon, the horizontal zone melting directional freeze forms silicon ingot, after removing the end to end part and outer matrix section that metallic impurity are assembled in the silicon ingot, carry out coarse reduction and cleaning; The recycling electron beam melting is removed phosphorus and carbon impurity, carries out horizontal zone melting second time directional freeze and becomes silicon ingot, removes afterwards metallic impurity are assembled in the zone melting and refining silicon ingot second time end to end part and outer matrix section, directly generates solar-grade polysilicon.Alemany etc. (Alemany C, Trassy C, Pateyron B, et al.Refiing of metallurgical grade silicon byinductive plasma[J] .Solar Energy Materials﹠amp; Solar Cells, 2002,72:41-48) utilize electromagnetic induction H ₂-O ₂Cement Composite Treated by Plasma silicon liquid finds that B content has obvious reduction, and refining effect is obvious, by interpretation and theoretical thermodynamics calculating are found that B mainly removes with the form volatilization of BOH.The plasma body that Japanese Patent No.4-228414 adopts argon gas that mixed gas contains hydrogen and water vapour to form together with SiO 2 powder, the surface of irradiation molten silicon promotes the oxidation removal of boron.The Marvin's meeting (Wu Jijun, Ma Wenhui, Wei Kuixian, et al.Removing boron from metallurgical gradesilicon by vacuum oxidation refining[C] .Proceedings of the 8 ^ThVacuum Metallurgy and SurfaceEngineering Conference.Shengyang, 2007:51) etc. the people adopt Ar-O ₂Plasma body, behind the refining 10min, the B content in the silicon drops to 2ppmw by 40ppmw in 2286～2320K scope.Above technique has all adopted plasma body, and its equipment requirements is high, and melting region is narrow, is blown into the oxidizing gas utilization ratio low, and energy consumption is high during suitability for industrialized production, and current consumption is large, and the treatment time is long, and production cost is high.

C.P.Khattak (Chandra P Khattak, David B Joyce, Frederick Schmid.A simple process toremove boron from metallurgical grade silicon[J] .Solar Energy Mater Solar Cel1s, 2002,74:77) in its paper, point out in silicon liquid, to pass into and contain O, H, the reactant gases of Cl and B reaction generate volatile gases, by carrier gas or the mode that vacuumizes it is discharged from system again, wherein, carrier gas can be selected neutral gas, such as Ar, can play simultaneously promotion silicon liquid and stir, the effect of accelerated reaction.Kondo Jiro etc. (Kondo Jiro, Okazawa Kensuke.Method for removingboron from silicon:US, 20070180949[P] .2007-09-08) have then studied from silicon liquid bottom and have been blown into by Ar, H ₂, H ₂O and O ₂Deng the method for the reactant gases oxidation that forms except B.

In the development of metallurgy method technique subsequently, it is found that and utilize slag practice can remove preferably boron and phosphorus matter in the silicon.US Patent No. 5788945 discloses a method of utilizing the continuous slag making of 60%CaO-40%SiO2 slag former, B content in the raw silicon can be down to 1ppmw from 40ppmw, wherein the slag processing is convection current in a container by slag and silicon, or by two or two convection current that realize slag and molten silicon with upper container.It is SiO that US Patent No. 2008/0241045A1 adopts slag former ₂-Na ₂CO ₃, adopt the mode of slag former recycle under 1600 ℃, B in the silicon is reduced to 0.16ppmw,

According to Tanahashi (Tanahashi, et al.Distribution behavior of boron between SiO2-saturatedNaO _0.5-CaO-SiO ₂Flux-molten silicon[J] .J.Mining Mater, 2002, calculating 118:497) etc. is with Na ₂O-CaO-SiO ₂Be the reaction slag system, the partition ratio of B in slag system can reach 3.5, considers simultaneously in the high alkalinity slag to pass into H ₂O can effectively increase the OH in the melt ^-With free oxygen concentration, for forming the BOH volatilization and forming B ₂O ₃Enter slag more favorably condition is provided mutually.The Viana Teixeira of Tokyo Univ Japan and Kazuki Morita (Leandro AugustoViana Teixeira and Kazuki Morital, Removal of Boron from Molten Silicon Using CaO-SiO ₂BasedSlags, ISIJIntemational, Vol.49 (2009), No.6, pp.783-787) obtained Different Ca F ₂The CaO-SiO of content ₂-CaF ₂The partition ratio of system and the activity quotient of boron oxide are also found Na simultaneously ₂The partition ratio that adds affiliation increase system of O.

Chinese patent CN02135841.9 (a kind of high-purity silicon for solar energy cell and production method thereof) discloses and has a kind ofly added lime in melt, ferric oxide, and the slagging process of fluorite has obtained the high-purity silicon of used for solar batteries.The patent 201010109835.2(Luo Xue of Xiamen University great waves, Gong Weiyang etc., a kind of method that adopts rare earth oxide to remove the boron from industrial silicon phosphorus impurities) in the slag former composition, introduced rare earth oxide, concrete composition is R _XO _Y(Y ₂O ₃, La ₂O ₃, CeO ₂, Sm ₂O ₃)-SiO ₂-BaO-CaF ₂With Medium frequency induction slag making 40min under vacuum, slag silicon weight ratio is 1:1, the B content in the polysilicon can be reduced to 0.15ppmw from 8ppmw, and P content is reduced to 1.5ppmw from 15ppmw.

From the development of following metallurgy method, slag practice is the main method of removing B element in the silicon, and the emphasis of research all is how to improve on the slag gold partition ratio of B now.Selection people for slag former have carried out a lot of trials, and common slag system has CaO-SiO ₂, Na ₂O-SiO ₂, CaO-SiO ₂-CaF ₂, CaO-MgO-SiO ₂, CaO-BaO-SiO ₂Deng, these slag systems are having certain effect aspect the removal of B, but there are some inevitable problems in the people aspect industrial production: at first, the removal effect of B is the difficult requirement that reaches solar-grade polysilicon still.Secondly, help the consumption of slag agent relatively too high in the slagging process, limited scale operation, also can produce certain pollution to silicon.And when using CaO slag making system, the content of phosphorus generally higher (at least several ppm, at most tens of ppm) in the slag former often more or less makes phosphorus impurities increase after the refining, increases the difficulty of subsequent process or increases the cost that removal of impurities is purified.

Summary of the invention

The object of the present invention is to provide a kind of slag refining to remove the method for boron from industrial silicon phosphorus impurities.

The present invention includes following steps:

1) the SiC coating that is coated with the last layer densification on the plumbago crucible surface then applies Y in the SiC coating as internal layer ₂O ₃Coating is as skin;

2) with after the various slag formers mixing, put into pretreated plumbago crucible, described various slag formers are ferric oxide, SiO ₂, MnO and CaF ₂Described ferric oxide is Fe ₂O ₃, FeO, Fe ₃O ₄In a kind of;

3) open medium-frequency induction furnace heating, melt to slag charge;

4) slag charge melts in the slag charge of backward fusing and adds industrial silicon, carries out slag refining, after slag charge and silicon material melt fully, reduces the power afterreaction;

5) in liquation, insert venting pin, pass into Ar+H to system ₂O guarantees that the silicon phase contacts with slag;

6) pull away venting pin, liquation upper strata silicon liquid is poured in the graphite jig that leaves standstill, cooling;

7) continue to add silicon material, repeating step 4)～6);

8) refining is crossed polysilicon and excise end to end impurity enriched part, measure remainder boron phosphorus content by ICP-MS again.

In step 1), the thickness of described internal layer can be 1～3mm, and described outer field thickness can be 1～2mm.

In step 2) in, described ferric oxide, SiO ₂, MnO and CaF ₂Mass percent can be: ferric oxide is that 10%～60%, MnO is 5%～35%, CaF ₂Be 10%～30%, surplus is SiO ₂Described ferric oxide, SiO ₂, MnO and CaF ₂Mass percent be preferably: ferric oxide is that 10%～50%, MnO is 5%～30%, CaF ₂Be 10%～25%, surplus is SiO ₂Described ferric oxide, SiO ₂, MnO and CaF ₂Mass percent be preferably: ferric oxide is that 10%～40%, MnO is 15%～25%, CaF ₂Be 10%～20%, surplus is SiO ₂

In step 3), the condition of described heating can be in 1～2h power is added to 120～150kW, and final holding power 120～150kW melts to slag charge.

In step 4), the add-on of described industrial silicon can be in mass ratio: slag former: industrial silicon=(20～26): (5～9), describedly fall lower powered condition and can be in 10～30min and to reduce power to 90～120kW, the temperature of described reaction can be 1550～1850 ℃.

In step 5), described venting pin can be 10～20mm apart from the distance of crucible bottom, described Ar+H ₂Among the O, Ar is 60%～90%, H by mass percentage ₂O is 40%～10%; The described Ar+H that passes into ₂The speed of O can be 0.5～3L/min, the described Ar+H that passes into ₂The speed of O is preferably 1～2L/min.

In step 6), described graphite jig can adopt cylindrical graphite jig, and the inside radius of described cylindrical graphite jig can be 15～25cm, and external diameter can be 16～26cm, and height can be 40～50cm; The speed of described cooling can be 100～400 ℃/min, and the speed of cooling is preferably 200～300 ℃/min.

In step 7), described repeating step 4)～6 number of times) can be and is cycled to repeat 5～20 times, is preferably 8～15 times.

In step 8), described excision ratio end to end can be 5%～10%.

The present invention is based on the smelting iron and steel principle, iron oxide based slag system has good effect to dephosphorization, MnO and CaF ₂Can effectively increase melt activity, selective oxidation iron (Fe of the present invention ₂O ₃, FeO ₂, FeO ₃)-SiO ₂-MnO-CaF ₂As slag former.According to thermodynamic principles, Fe ₂O ₃-SiO ₂-MnO-CaF ₂Reaction equation with B, P in slagging process is as follows:

$B\left(l\right)+\frac{3}{4}{\mathrm{SiO}}_2\left(l\right)={\mathrm{BO}}_{1.5}\left(l\right)+\frac{3}{4}\mathrm{Si}\left(l\right)$

Fe ₂O ₃+1.2P＝1.2PO _2.5+2Fe

Usually represent deimpurity ability with partition ratio.

The partition ratio of B is expressed as

Wherein, (mass%B) the B content of expression slag in mutually, [mass%B] expression silicon B content in mutually.The B oxidation products BO that generates as can be known according to phasor _1.5Thereby easily be combined with MnO and improved ferric oxide (Fe ₂O ₃, FeO ₂, FeO ₃Deng)-SiO ₂-MnO-CaF ₂Slag system is to the B oxygenizement, and then improved the B partition ratio.

The partition ratio of P is expressed as

Wherein, (mass%P) the P content of expression slag in mutually, [mass%P] expression silicon P content in mutually.Not only ferric oxide can improve the partition ratio of P and CaF to the oxidation of P in this slag system ₂Also can play dephosphorizing and can generate Ca with the oxide compound reaction of phosphorus ₅(PO ₄) ₃Thereby, better improved the removal effect of phosphorus.

But this slag system is in slagging process, along with the increase of iron oxide content, L _pAlso can and then rise, but along with the decline of P content in the silicon, the amount of the ferric oxide of increase can't be all and P reaction, L _pDescend.The increase of simultaneous oxidation iron also can be to SiO ₂Activity exert an influence, thereby reduce the clearance of B.Along with SiO ₂The increase of content, the system oxygen partial pressure increases, L _BRise gradually, but excessive oxygen partial pressure makes again L _BDescend.Therefore, for ferric oxide-SiO ₂-MnO-CaF ₂The slag making system is determined suitable ferric oxide/SiO ₂/ MnO/CaF ₂Most important for the dust removal rate that improves whole system.

Main purpose of the present invention provides the processing method that boron and phosphorus matter in the polysilicon is removed in a kind of slag making.The concrete technology flow process is to prepare by a certain percentage slag charge first, has put it into SiC, Y ₂O ₃In the plumbago crucible of coating, Frequency Induction Heating adds the industrial silicon material to fusing, and then aeration-agitation after the fusing of silicon material is poured upper strata silicon liquid into graphite and accepted crucible and cool off fast.The general percentage range of each composition in the slag system that the present invention is given, OK range, design parameter scope in optimized scope and the technique, and the technological process cost is low, easy to operate, energy consumption is little, is suitable for suitability for industrialized production.

Advantage of the present invention is to utilize SiO ₂, in the time of the golden partition ratio of the raising B slag that the slag system ingredients such as MnO can be larger, utilize ferric oxide in the slag system, CaF ₂Better improved the removal effect of P with the interaction of phosphorus, wherein the boron clearance reaches more than 95%, tp removal rate is up to more than 90%, solved the present Ca B such as slag system such as grade of system partition ratio generally lower, and the problems such as the P removal effect is not good only need be carried out directional freeze one procedure after slag making is finished again, just industrial silicon can be purified to solar-grade polysilicon, simple for process, the industrialization feasibility is high.

Embodiment

Embodiment 1

1. the SiC coating that is coated with the last layer densification on the plumbago crucible surface is about 1.5mm as internal layer thickness, then applies Y in the SiC coating ₂O ₃Coating is about 1mm as outer layer thickness, to increase plumbago crucible work-ing life.

2. weighing Fe ₂O ₃(10%wt)-SiO ₂(60%wt)-MnO (20%wt)-CaF ₂(10%wt) slag former is total to 130kg, puts into the graphite of coating.Close bell, open intermediate frequency, the 1h internal power rises to 120kW, keeps power 120kW that slag charge is melted fully.

3. after the slag charge fusing, add 25kg industrial silicon (B content is 8.6ppmw, and P content is 15ppmw).After slag charge and silicon material melt fully, reduce power in the 25min to 90kW, recording this moment temperature of reaction by infrared thermometer is 1550 ℃.

4. pass into mixed gas Ar+H to system ₂O, venting pin are apart from crucible bottom 10mm, and wherein the volume fraction of Ar is 60%, H ₂The volume fraction of O is 40%.Ventilation Rate 2L/min fully stirs liquation.

5.30min after, pull away venting pin, stop ventilation, liquation upper strata silicon liquid is poured into the graphite that leaves standstill accept in the mould, cool off, the outside radius of the cylindrical graphite jig that this experiment is adopted is 17cm, inside radius is 15cm, and height is 40cm, and the control rate of cooling is at 200 ℃/min.

6. continue in plumbago crucible, to add industrial silicon 25kg, so repeat slag making 8 times.

7. obtain altogether refining polysilicon 170kg, through ICP-MS the gained polysilicon is taken multiple measurements and average, wherein average B content is 0.1ppmw, and mean P content is 0.5ppmw.

Embodiment 2

Technological process is with embodiment 1.Plumbago crucible SiC undercoat thickness is 3mm, Y ₂O ₃External coating (EC) thickness is 1.5mm, wherein adds slag former FeO (10%wt)-SiO ₂(60%wt)-MnO (15%wt)-CaF ₂(15%wt) be total to 100kg.Open intermediate frequency, in the 1.5h power is risen to 150kW, keep power 150kW that slag charge is melted fully.Then add the 45kg industrial silicon.In the 15min power is reduced to 120kW after the fusing fully, this moment, temperature of reaction was 1650 ℃.Pass into 90%Ar+10%H ₂O stirs liquation, and venting pin is about 12mm apart from the distance of crucible bottom, Ventilation Rate 1L/min.After slag making continued 15min, pouring upper strata silicon liquid into outside radius was 22cm, and inside radius is 20cm, and high accepting for the graphite of 50cm cooled off in the mould, and rate of cooling is controlled at 200 ℃/min.Again add the 45kg industrial silicon, altogether add 15 times.Obtain altogether refining polysilicon 573kg.Recording average B content through ICP-MS is 0.25ppmw, and mean P content is 1.5ppmw.

Embodiment 3

Technological process is with embodiment 1.Plumbago crucible SiC undercoat thickness is 1mm, Y ₂O ₃External coating (EC) thickness is that 2mm adds slag former Fe ₃O ₄(15%wt)-SiO ₂(60%wt)-MnO (10%wt)-CaF ₂(15%wt) be total to 100kg.Open intermediate frequency, in the 1.2h power is risen to 130kW, keep power 130kW that slag charge is melted fully.Then add the 35kg industrial silicon.In the 15min power is reduced to 110kW after the fusing fully, this moment, temperature of reaction was 1750 ℃.Venting pin is 14mm apart from the distance of crucible bottom, Ventilation Rate 1.5L/min.After slag making continued 20min, pouring upper strata silicon liquid into outside radius was 20cm, and inside radius is 18cm, and high accepting for the graphite of 45cm cooled off in the mould, and rate of cooling is controlled at 300 ℃/min.Again add the 35kg industrial silicon, altogether add 10 times.Obtain altogether refining polysilicon 212kg.Recording average B content through ICP-MS is 0.12ppmw, and mean P content is 0.7ppmw.

Embodiment 4

Technological process is with embodiment 1.Plumbago crucible SiC undercoat thickness is 3mm, Y ₂O ₃External coating (EC) thickness is that 1mm adds slag former Fe ₂O ₃(20%wt)-SiO ₂(60%wt)-MnO (10%wt)-CaF ₂(10%wt) be total to 130kg.Open intermediate frequency, in the 2h power is risen to 150kW, keep power 150kW that slag charge is melted fully.Then add the 45kg industrial silicon.In the 20min power is reduced to 120kW after the fusing fully, this moment, temperature of reaction was 1850 ℃.Venting pin is 17mm apart from the distance of crucible bottom, passes into 80%Ar+20%H ₂O stirs liquation, Ventilation Rate 1L/min.After slag making continued 20min, pouring upper strata silicon liquid into outside radius was 20cm, and inside radius is 18cm, and high accepting for the graphite of 45cm cooled off in the mould, and rate of cooling is controlled at 300 ℃/min.Again add the 45kg industrial silicon, altogether add 9 times.Obtain altogether refining polysilicon 345kg.Recording average B content through ICP-MS is 0.15ppmw, and mean P content is 0.8ppmw.

Embodiment 5

Technological process is with embodiment 1.Plumbago crucible SiC undercoat thickness is 2mm, Y ₂O ₃External coating (EC) thickness is that 2mm adds slag former Fe ₃O ₄(10%wt)-SiO ₂(50%wt)-MnO (20%wt)-CaF ₂(20%wt) be total to 120kg.Open intermediate frequency, in the 1.5h power is risen to 150kW, keep power 150kW that slag charge is melted fully.Then add the 45kg industrial silicon.In the 15min power is reduced to 120kW after the fusing fully, this moment, temperature of reaction was 1850 ℃.Venting pin is that 15mm passes into 60%Ar+40%H apart from the distance of crucible bottom ₂O stirs liquation, Ventilation Rate 2L/min.After slag making continued 30min, pouring upper strata silicon liquid into outside radius was 20cm, and inside radius is 18cm, and high accepting for the graphite of 45cm cooled off in the mould, and rate of cooling is controlled at 200 ℃/min.Again add the 30kg industrial silicon, altogether add 10 times.Obtain altogether refining polysilicon 255kg.Recording average B content through ICP-MS is 0.12ppmw, and mean P content is 0.8ppmw.

Embodiment 6

Technological process is with embodiment 1.Plumbago crucible SiC undercoat thickness is 2.5mm, Y ₂O ₃External coating (EC) thickness is that 1mm adds slag former FeO (10%wt)-SiO ₂(50%wt)-MnO (20%wt)-CaF ₂(20%wt) be total to 110kg.Open intermediate frequency, in the 2h power is risen to 150kW, keep power 150kW that slag charge is melted fully.Then add the 45kg industrial silicon.In the 20min power is reduced to 110kW after the fusing fully, this moment, temperature of reaction was 1750 ℃.Venting pin is that 19mm passes into 70%Ar+30%H apart from the distance of crucible bottom ₂O stirs liquation, Ventilation Rate 2L/min.After slag making continued 20min, pouring upper strata silicon liquid into outside radius was 20cm, and inside radius is 18cm, and high accepting for the graphite of 45cm cooled off in the mould, and rate of cooling is controlled at 300 ℃/min.Again add the 35kg industrial silicon, altogether add 12 times.Obtain altogether refining polysilicon 357kg.Recording average B content through ICP-MS is 0.2ppmw, and mean P content is 1.2ppmw.

Embodiment 7

Technological process is with embodiment 1.Plumbago crucible SiC undercoat thickness is 2mm, Y ₂O ₃External coating (EC) thickness is that 1.5mm adds slag former Fe ₂O ₃(20%wt)-SiO ₂(40%wt)-MnO (15%wt)-CaF ₂(15%wt) be total to 130kg.In the 2h power is risen to 150kW, keep power 150kW that slag charge is melted fully.Then add the 45kg industrial silicon.In the 20min power is reduced to 110kW after the fusing fully, this moment, temperature of reaction was 1750 ℃.Venting pin is that 20mm passes into 90%Ar+10%H apart from the distance of crucible bottom ₂O stirs liquation, Ventilation Rate 2L/min.After slag making continued 15min, pouring upper strata silicon liquid into outside radius was 20cm, and inside radius is 18cm, and high accepting for the graphite of 45cm cooled off in the mould, and rate of cooling is controlled at 200 ℃/min.Again add the 30kg industrial silicon, altogether add 15 times.Obtain altogether refining polysilicon 383kg.Recording average B content through ICP-MS is 0.18ppmw, and mean P content is 1ppmw.

Claims (10)

1. a slag refining is removed the method for boron from industrial silicon phosphorus impurities, it is characterized in that may further comprise the steps:

1) the SiC coating that is coated with the last layer densification on the plumbago crucible surface then applies Y in the SiC coating as internal layer ₂O ₃Coating is as skin;

2) with after the various slag formers mixing, put into pretreated plumbago crucible, described various slag formers are ferric oxide, SiO ₂, MnO and CaF ₂Described ferric oxide is Fe ₂O ₃, FeO, Fe ₃O ₄In a kind of;

3) open medium-frequency induction furnace heating, melt to slag charge;

4) slag charge melts in the slag charge of backward fusing and adds industrial silicon, carries out slag refining, after slag charge and silicon material melt fully, reduces the power afterreaction;

5) in liquation, insert venting pin, pass into Ar+H to system ₂O guarantees that the silicon phase contacts with slag;

6) pull away venting pin, liquation upper strata silicon liquid is poured in the graphite jig that leaves standstill, cooling;

7) continue to add silicon material, repeating step 4)～6);

8) refining is crossed polysilicon and excise end to end impurity enriched part, measure remainder boron phosphorus content by ICP-MS again.

2. a kind of slag refining as claimed in claim 1 is removed the method for boron from industrial silicon phosphorus impurities, it is characterized in that in step 1), and the thickness of described internal layer is 1～3mm, and described outer field thickness is 1～2mm.

3. a kind of slag refining as claimed in claim 1 is removed the method for boron from industrial silicon phosphorus impurities, it is characterized in that in step 2) in, described ferric oxide, SiO ₂, MnO and CaF ₂Mass percent be: ferric oxide is that 10%～60%, MnO is 5%～35%, CaF ₂Be 10%～30%, surplus is SiO ₂Described ferric oxide, SiO ₂, MnO and CaF ₂Mass percent be preferably: ferric oxide is that 10%～50%, MnO is 5%～30%, CaF ₂Be 10%～25%, surplus is SiO ₂Described ferric oxide, SiO ₂, MnO and CaF ₂Mass percent be preferably: ferric oxide is that 10%～40%, MnO is 15%～25%, CaF ₂Be 10%～20%, surplus is SiO ₂

4. a kind of slag refining as claimed in claim 1 is removed the method for boron from industrial silicon phosphorus impurities, it is characterized in that in step 3), the condition of described heating is for adding to power 120～150kW in 1～2h, final holding power 120～150kW melts to slag charge.

5. a kind of slag refining as claimed in claim 1 is removed the method for boron from industrial silicon phosphorus impurities, it is characterized in that in step 4), and the add-on of described industrial silicon is in mass ratio: slag former: industrial silicon=(20～26): (5～9).

6. a kind of slag refining as claimed in claim 1 is removed the method for boron from industrial silicon phosphorus impurities, it is characterized in that in step 4), describedly fall lower powered condition for reduce power to 90～120kW in 10～30min, the temperature of described reaction is 1550～1850 ℃.

7. a kind of slag refining as claimed in claim 1 is removed the method for boron from industrial silicon phosphorus impurities, it is characterized in that in step 5), and described venting pin is 10～20mm apart from the distance of crucible bottom, described Ar+H ₂Among the O, Ar is 60%～90%, H by mass percentage ₂O is 40%～10%; The described Ar+H that passes into ₂The speed of O can be 0.5～3L/min, the described Ar+H that passes into ₂The speed of O is preferably 1～2L/min.

8. a kind of slag refining as claimed in claim 1 is removed the method for boron from industrial silicon phosphorus impurities, it is characterized in that in step 6), described graphite jig adopts cylindrical graphite jig, and the inside radius of described cylindrical graphite jig is 15～25cm, external diameter is 16～26cm, and height is 40～50cm; The speed of described cooling can be 100～400 ℃/min, and the speed of cooling is preferably 200～300 ℃/min.

9. a kind of slag refining as claimed in claim 1 is removed the method for boron from industrial silicon phosphorus impurities, it is characterized in that in step 7) described repeating step 4)～6) number of times can be and be cycled to repeat 5～20 times, be preferably 8～15 times.

10. a kind of slag refining as claimed in claim 1 is removed the method for boron from industrial silicon phosphorus impurities, it is characterized in that in step 8), and described excision ratio end to end is 5%～10%.