CN102101671B - Method for removing boron and phosphorus impurities from industrial silicon by using magnesium-containing compound - Google Patents
Method for removing boron and phosphorus impurities from industrial silicon by using magnesium-containing compound Download PDFInfo
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- CN102101671B CN102101671B CN2011100009943A CN201110000994A CN102101671B CN 102101671 B CN102101671 B CN 102101671B CN 2011100009943 A CN2011100009943 A CN 2011100009943A CN 201110000994 A CN201110000994 A CN 201110000994A CN 102101671 B CN102101671 B CN 102101671B
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Abstract
The invention discloses a method for removing boron and phosphorus impurities from industrial silicon by using a magnesium-containing compound, and relates to the industrial silicon, which make boron (B) and phosphorus (P) in a silicon material form oxides to enter a slag phase so as to fulfill the aim of purification by melting a slag forming agent and the silicon material through a medium frequency induction furnace. In the method, the maximum-efficiency ingredient proportion for boron removal by oxidation is achieved, and proper ranges for process parameters such as a slag-silicon ratio, medium frequency smelting power, a reaction temperature, reaction time, stirring speed and the like during industrial production are simultaneously given, so that a solar-grade polycrystalline silicon production process which is low in cost and can be subjected to industrial mass production is formed. The method has the advantages of frequent utilization of a slag agent, continuity of production and the like and is easy to operate. By the method, the B content in the industrial silicon can be reduced from 8ppmw to 0.1 to 0.5ppmw, and the P content can be reduced from 15ppmw to 1 to 3ppmw.
Description
Technical field
The present invention relates to a kind of industrial silicon, especially relate to a kind of method that adopts magnesium-containing compound to remove boron and phosphorus matter in the industrial silicon.
Background technology
Exhausted and the lasting soaring situation of oil price in the face of our times property traditional energy, sun power has received the great attention of countries in the world as reproducible clear energy sources.And after getting into 21 century, the average growth rate per annum of global photovoltaic module estimates that especially up to more than 30% global solar photovoltaic installed capacity at end of this year cumulative amount will be increased to more than the 18000MW, and this will certainly bring the high speed development to solar cell industry.But the silicon materials selling at exorbitant prices also becomes one of important factor that hinders the photovoltaic industry development, and under the condition that does not influence efficient, the cost that reduces silicon materials is the key that reduces the silicon solar cell cost.Therefore; In order to satisfy photovoltaic industry for the raw-material heavy demand of polysilicon; Break away from the solar level silicon materials simultaneously to the depending on of electronic-grade silicon material, each big polysilicon manufacturer of the world and research unit actively launch the Study on Process of low cost prodn solar-grade polysilicon.Wherein, metallurgy method prepare solar energy level silicon simple owing to its technical process, pollute less and do not have sub product to receive much concern in the process.
Impurity in the silicon refers to metallic impurity such as nonmetallic impurity such as B, P, As, C and Fe, Ti, Al, Mo, and the main source of these impurity is the remnants after the metalluragical silicon impurities in raw materials is purified.All the time, P type silicon accounts for the dominant position of photovoltaic industry.Boron is the doping agent of P type silicon, and the auger recombination of material increases sharply (auger recombination rate and impurity concentration square be directly proportional), carrier mobility reduces but the boron of too high amount can make.Can cause minority diffusion length to descend like this, battery efficiency reduces.In addition, the metastable state defective (BO of boron and oxygen formation
n) be the major cause that sorrow subtracts after the silion cell illumination.
At present, slag practice is one of effective ways of removing boron and phosphorus matter.The Suzuki and the Sano (Suzuki of Japan; Sano.Thermodynamics for removal of boron from metallurgical silicon by flux treatmentof molten silicon [C] .The 10th European Photovoltaic Solar Energy Conference In Lisbon; Portugal8-12Apr.1991) be that slag has carried out comparatively systematic research to Ca; It is through mixing melting reaction 2h with the silicon of 10g and the slag of 10g heterogeneity and different ratios, and the data declaration of acquisition is with CaO-BaO-SiO
2Can obtain maximum slag gold partition ratio about 2 as slag system.Simultaneously, research shows that slag gold partition ratio to a certain degree then begins to descend but be increased to along with the increase of the basicity of slag also can increase to some extent.The Wang Xinguo of Shanghai University, the big medium people (Wang Xinguo of fourth; Ding Weizhong, Tang Kai etc. the thermodynamic study of silicon alloy oxidation refining process [J]. China YouSe Acta Metallurgica Sinica, 2001; 11 (3): 503-509) analyzed under 1550 ℃ of temperature condition; The slag of Pure Silicon Metal impurity element in oxidation refining process gold equilibrium composition has provided the balance isopleth of aluminium and calcium, and is that oxygenant is tested the dealuminzation and the decalcification of metalluragical silicon with the soda lime glass.The result shows that the impurity aluminum calcium clearance in the metalluragical silicon reaches as high as 93.1% and 96.4%, and the content of aluminium and calcium is minimum reduces to 0.07% and 0.025%, has reached good refining effect.
Suzuki (Suzuki K; Kumagai T; Sano N.Removal of boron from metallurgical-grade silicon byapplying the plasma treatment [J] .ISIJ Int, 1992,32 (5): 630) point out; When temperature surpasses 2027 ℃, the oxidized formation BO of B meeting, B
2O, B
2O
3Deng gas, wherein the vapour pressure with BO is the highest, is respectively B
2O, B
2O
3493 times and 1321 times of vapour pressure, thus B under the oxidisability plasma ambient through forming the purpose that gaseous state BO can reach removal.People such as C.Alemany (the Delannoy Y of France; Alemany C, Li K I, et al.Plasma-refining process to providesolar-grade silicon [J] .Solar Energy Materials and Solar Cells; 2002; 72 (1-4): 69-75) utilize the ionic fluid metallurgical grade silicon of purifying, they feed H utilizing ionic fluid and ruhmkorff coil to keep silicon under the fused state
2And O
2Reactant gases carries out refining purifies, and result of study shows that B volatilizees with forms such as BOH, BO, BH; Wherein the volatilization of BOH is topmost; The concentration of B is reduced to 2ppmw by 15ppmw, and C and O generate CO and be discharged from, and therefore utilizes the plasma oxidation refining can well remove C and B element in the silicon.Through test, the silicon ingot after the purification is processed solar cell, and its transformation efficiency is 12.7%.
It is the slag former of main body with sulfide that the applicant discloses a kind of in Chinese patent 201010177791.7, and staple is RS-SiO
2-BaO-CaF
2(wherein RS is sulfide FeS commonly used, CuS, ZnS) adopts this novel slag former that industrial silicon is carried out melting, can the B content in the polysilicon be reduced to 0.35～0.60ppmw from 10ppmw, and P content is reduced to 1～2.5ppmw from 25ppmw.
Summary of the invention
The object of the present invention is to provide a kind of method that adopts magnesium-containing compound to remove boron and phosphorus matter in the industrial silicon.
The present invention includes following steps:
1) slag charge is mixed with the silicon material, get slag charge and silicon material compound, the mass ratio of slag charge and silicon material is 1: (0.5～10);
In step 1), the mass ratio of said slag charge and silicon material can be 1: (1～5).
2) slag charge and silicon material compound are pressed into bulk;
In step 2) in, can slag charge and silicon material compound be put into tabletting machine and be pressed into bulk, the pressure of tabletting machine is 4 * 10
6～15 * 10
6Pa is preferably 10 * 10
6～15 * 10
6Pa; The time of briquetting can be 10～90s, is preferably 30～60s.
3) will be pressed into blocky slag charge and silicon material compound is put into plumbago crucible, open mechanical pump, the intravital vacuum of stove will be evacuated to below the 300Pa;
4) open the medium-frequency induction furnace heating, rubescent to plumbago crucible, closed vacuum valve cuts out mechanical pump, feeds Ar gas to stove, makes the vacuum tightness of system reach a standard atmospheric pressure;
In step 4), the power of said medium-frequency induction furnace heating can be 20～40kW.
5) continue to feed Ar gas, the power of adjustment medium-frequency induction furnace heating makes slag charge and the fusing of silicon material compound;
In step 5), the speed of said lasting feeding Ar gas can be 0.5～3L/min, is preferably 1.5～3L/min; The power of said adjustment medium-frequency induction furnace heating can be 120～150kW.
6) treat that slag charge and silicon material compound melt fully after, venting pin is slowly inserted silicon liquid, the beginning aeration-agitation;
In step 6), said beginning aeration-agitation can be controlled at 5～55mm with the degree of depth that venting pin gets into silicon liquid, preferably is controlled at 20～40mm.
7) through adjustment intermediate frequency power, make maintain at 1600～1900 ℃, liquation generation layering, the slag liquid precipitate below, and silicon liquid is on the upper strata;
In step 7), said intermediate frequency power can be 100～130kW.
8) after slag making finishes, venting pin is lifted away from plumbago crucible, closes upset cast behind the breather valve, with the upper strata silicon liquid in the plumbago crucible all pour into be incubated 3～5h in the graphite jig after, powered-down, furnace cooling takes out the silicon material, surveys boron and the content of phosphorus in the silicon material;
In step 8), saidly close upset cast behind the breather valve, can intermediate frequency power be controlled at 110～140kW, upset cast again behind 5～10min; The temperature of said insulation can be 1400～1600 ℃, is preferably 1440～1540 ℃; The boron in the said survey silicon material and the content of phosphorus can be through the boron in plasma inductance coupling mass spectrograph (ICP-MS) the survey silicon material and the content of phosphorus.
9) secondary charging adds industrial silicon, repeats above-mentioned steps 5)～step 8), continue slag making, under the normal circumstances, reusable 3～6 times of slag charge.
The present invention is according to thermodynamic argument, MgO at high temperature can with SiO
2Form MgO
2SiO
2And MgOSiO
2These two kinds of intermediate compounds are because B and the oxidized product B O of P
1.5And P
2O
5Solid solubility in these two kinds of compounds is higher, this means MgO-SiO
2-BaO-CaF
2This slag system has very strong oxygenizement and effective sorption to B, P, to B, P removal effect highly significant in the silicon.
At slag former MgR-SiO
2-BaO-CaF
2In the system, the weight percent general range of MgR is 10%～70%, and suitable scope is 10%～50%, and optimized scope is 10%～30%; SiO
2General range is 20%～90%, and suitable scope is 20%～80%, and optimized scope is 40%～80%; The BaO general range is 5%～40%, and suitable scope is 5%～20%, and optimized scope is 5%～10%; CaF
2General range is 5%～30%, and suitable scope is 5%～20%, and optimized scope is 10%～20%.
Compare with the method for boron and phosphorus matter in the existing removal industrial silicon, the present invention has following outstanding advantage:
1) adopts MgR (MgO, Mg (OH)
2, MgCl
2)-SiO
2-BaO-CaF
2The slag making system is carried out the application that P removes B that removes of industrial silicon, has obtained good result, and the boron clearance reaches more than 95%, and tp removal rate is up to more than 80%, and instead Ca is that slag former becomes new and effective slag former.Can the B content in the industrial silicon be reduced to 0.1～0.5ppmw from 8ppmw, P content is reduced to 2～4ppmw from 15ppmw.
2) slag charge is reusable, has reduced material cost and time cost.
3) the impurity element Mg that introduces, Ca etc. can remove through a directional freeze.
4) chemical property of slag former is stable, and is pollution-free.
5) be used for removing the slag former of industrial silicon boron and phosphorus matter, through introducing activeconstituents MgR (MgO, Mg (OH)
2, MgCl
2), improve SiO
2Oxidation efficiency, can reduce boron phosphorus content in the silicon greatly, and finally obtain solar-grade polysilicon through refining.
Embodiment
Embodiment 1
1) accurate weighing MgO (30%wt)-SiO
2(40%wt)-BaO (10%wt)-CaF
2(20%wt) slag former 50kg altogether, with silica flour (B content is 8ppmw, and P content is 15ppmw) the 50kg thorough mixing of purity 3N, with powder 10 * 10
6Pa lower sheeting 60s processes cylindric block, puts into plumbago crucible.
2) start mechanical pump and vacuumize, open Frequency Induction Heating when vacuum during less than 300Pa, holding power 20kW is rubescent to plumbago crucible.
3) feed Ar gas through the graphite venting pin to system, the system vacuum tightness of making reaches a standard atmospheric pressure, adjusts power afterwards and makes the compound fusing to 150kW.Whole slagging process continues to feed Ar gas, and Ventilation Rate is 3L/min.
4) treat that silicon material and slag charge melt fully after, venting pin is slowly inserted silicon liquid, the beginning aeration-agitation.It is 40mm that venting pin gets into the silicon liquid degree of depth.
5) adjustment intermediate frequency power is controlled at 130kW, makes in the slagging process maintain at 1900 ℃.
6) behind the 2h, venting pin is extracted from liquation, improved intermediate frequency power to 140kW.Behind the 10min, the silicon liquid in the plumbago crucible poured into be incubated 5h in the mould, 1540 ℃ of holding temperatures.
7) add the silica flour of 50Kg again in the plumbago crucible, repeat above step 3-step 6 totally 3 times.
8) recording 3 average B content in the silicon appearance through plasma inductance coupling mass spectrograph (ICP-MS) is 0.1ppmw, and mean P content is 1ppmw.
Embodiment 2
Technological process is with embodiment 1.Slag former MgO (20%wt)-SiO
2(60%wt)-BaO (10%wt)-CaF
2(10%wt) slag former is total to 50kg, silicon material 100kg.Powder is 15 * 10
6Pa lower sheeting 30s; Power is controlled at 120kW in the slagging process, makes maintain at 1800 ℃; It is 20mm that venting pin gets into the silicon liquid degree of depth, and Ventilation Rate is 1.5L/min; Behind the slag making 2h, improve power to 130kW, insulation 3h is left standstill in the cast back under 1440 ℃; Repeat slag making 6 times; The average B content that records in the silicon appearance through plasma inductance coupling mass spectrograph (ICP-MS) is 0.2ppmw, and mean P content is 1.5ppmw.
Embodiment 3
Technological process is with embodiment 1.Slag former MgO (10%wt)-SiO
2(80%wt)-BaO (5%wt)-CaF
2(5%wt) slag former is total to 20kg, silicon material 100kg.Powder is 12 * 10
6Pa lower sheeting 40s; Power is controlled at 100kW in the slagging process, makes maintain at 1600 ℃; It is 30mm that venting pin gets into the silicon liquid degree of depth, and Ventilation Rate is 2L/min; Behind the slag making 0.5h, improve power to 110kW, insulation 3h is left standstill in the cast back under 1500 ℃; Repeat slag making 5 times; The average B content that records in the silicon appearance through plasma inductance coupling mass spectrograph (ICP-MS) is 0.5ppmw, and mean P content is 3ppmw.
Embodiment 4
Technological process is with embodiment 1.Slag former Mg (OH)
2(20%wt)-SiO
2(50%wt)-BaO (10%wt)-CaF
2(20%wt) slag former is total to 30kg, silicon material 120kg.Powder is 10 * 10
6Pa lower sheeting 60s; Power is controlled at 130kW in the slagging process, makes maintain at 1900 ℃; It is 30mm that venting pin gets into the silicon liquid degree of depth, and Ventilation Rate is 3L/min; Behind the slag making 1.5h, improve power to 140kW, insulation 5h is left standstill in the cast back under 1540 ℃; Repeat slag making 3 times, the average B content that records in the silicon appearance through plasma inductance coupling mass spectrograph (ICP-MS) is 0.45ppmw, and mean P content is 2.5ppmw.
Embodiment 5
Technological process is with embodiment 1.Slag former (MgOH)
2(30%wt)-SiO
2(60%wt)-BaO (5%wt)-CaF
2(5%wt) slag former is total to 40kg, silicon material 120kg.Powder is 14 * 10
6Pa lower sheeting 60s; Power is controlled at 110kW in the slagging process, makes maintain at 1700 ℃; It is 30mm that venting pin gets into the silicon liquid degree of depth, and Ventilation Rate is 2L/min; Behind the slag making 1h, improve power to 120kW, insulation 4h is left standstill in the cast back under 1440 ℃; Repeat slag making 4 times, the average B content that records in the silicon appearance through plasma inductance coupling mass spectrograph (ICP-MS) is 0.35ppmw, and mean P content is 3ppmw.
Embodiment 6
Technological process is with embodiment 1.Slag former MgCl
2(30%wt)-SiO
2(60%wt)-BaO (5%wt)-CaF
2(5%wt) slag former is total to 50kg, silicon material 100kg.Powder is 10 * 10
6Pa lower sheeting 30s; Power is controlled at 100kW in the slagging process, makes maintain at 1600 ℃; It is 30mm that venting pin gets into the silicon liquid degree of depth, and Ventilation Rate is 0.5L/min; Behind the slag making 0.5h, improve power to 110kW, insulation 4h is left standstill in the cast back under 1480 ℃; Repeat slag making 6 times, the average B content that records in the silicon appearance through plasma inductance coupling mass spectrograph (ICP-MS) is 0.25ppmw, and mean P content is 2ppmw.
Claims (13)
1. method that adopts magnesium-containing compound to remove boron and phosphorus matter in the industrial silicon is characterized in that may further comprise the steps:
1) slag charge is mixed with the silicon material, get slag charge and silicon material compound, the mass ratio of slag charge and silicon material is 1: 1～5;
2) slag charge and silicon material compound are pressed into bulk;
3) will be pressed into blocky slag charge and silicon material compound is put into plumbago crucible, open mechanical pump, the intravital vacuum of stove will be evacuated to below the 300Pa;
4) open the medium-frequency induction furnace heating, rubescent to plumbago crucible, closed vacuum valve cuts out mechanical pump, feeds Ar gas to stove, makes the vacuum tightness of system reach a standard atmospheric pressure;
5) continue to feed Ar gas, the power of adjustment medium-frequency induction furnace heating makes slag charge and the fusing of silicon material compound;
6) treat that slag charge and silicon material compound melt fully after, venting pin is inserted silicon liquid, the beginning aeration-agitation;
7) through adjustment intermediate frequency power, make maintain at 1600～1900 ℃, liquation generation layering, the slag liquid precipitate below, and silicon liquid is on the upper strata;
8) after slag making finishes, venting pin is lifted away from plumbago crucible, closes upset cast behind the breather valve, with the upper strata silicon liquid in the plumbago crucible all pour into be incubated 3～5h in the graphite jig after, powered-down, furnace cooling takes out the silicon material, surveys boron and the content of phosphorus in the silicon material;
9) secondary charging adds industrial silicon, repeats above-mentioned steps 5)～step 8), continue slag making.
2. a kind of method that adopts magnesium-containing compound to remove boron and phosphorus matter in the industrial silicon as claimed in claim 1 is characterized in that in step 2) in, slag charge and silicon material compound to be put into tabletting machine be pressed into bulk, the pressure of tabletting machine is 4 * 10
6～15 * 10
6Pa, the time of briquetting is 10～90s.
3. a kind of method that adopts magnesium-containing compound to remove boron and phosphorus matter in the industrial silicon as claimed in claim 2, the pressure that it is characterized in that said tabletting machine is 10 * 10
6～15 * 10
6Pa, the time of briquetting is 30～60s.
4. a kind of method that adopts magnesium-containing compound to remove boron and phosphorus matter in the industrial silicon as claimed in claim 1 is characterized in that in step 4) the power of said medium-frequency induction furnace heating is 20～40kW.
5. a kind of method that adopts magnesium-containing compound to remove boron and phosphorus matter in the industrial silicon as claimed in claim 1 is characterized in that in step 5), and the speed of said lasting feeding Ar gas is 0.5～3L/min.
6. a kind of method that adopts magnesium-containing compound to remove boron and phosphorus matter in the industrial silicon as claimed in claim 5 is characterized in that the speed of said lasting feeding Ar gas is 1.5～3L/min.
7. a kind of method that adopts magnesium-containing compound to remove boron and phosphorus matter in the industrial silicon as claimed in claim 1 is characterized in that in step 5) the power of said adjustment medium-frequency induction furnace heating is 120～150kW.
8. a kind of method that adopts magnesium-containing compound to remove boron and phosphorus matter in the industrial silicon as claimed in claim 1 is characterized in that in step 6), and said beginning aeration-agitation is that the degree of depth that venting pin gets into silicon liquid is controlled at 5～55mm.
9. a kind of method that adopts magnesium-containing compound to remove boron and phosphorus matter in the industrial silicon as claimed in claim 8 is characterized in that said beginning aeration-agitation, is the degree of depth that venting pin gets into silicon liquid is controlled at 20～40mm.
10. a kind of method that adopts magnesium-containing compound to remove boron and phosphorus matter in the industrial silicon as claimed in claim 1 is characterized in that in step 7) said intermediate frequency power is 100～130kW.
11. a kind of method that adopts magnesium-containing compound to remove boron and phosphorus matter in the industrial silicon as claimed in claim 1; It is characterized in that in step 8); Saidly closing upset cast behind the breather valve, is that intermediate frequency power is controlled at 110～140kW, upset cast again behind 5～10min.
12. a kind of method that adopts magnesium-containing compound to remove boron and phosphorus matter in the industrial silicon as claimed in claim 1 is characterized in that in step 8) the temperature of said insulation is 1400～1600 ℃.
13. a kind of method that adopts magnesium-containing compound to remove boron and phosphorus matter in the industrial silicon as claimed in claim 12, the temperature that it is characterized in that said insulation is 1440～1540 ℃.
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| CN102515168A (en) * | 2011-12-12 | 2012-06-27 | 昆明理工大学 | Method for removing boron impurity in industrial silicon |
| CN103570023B (en) * | 2012-07-23 | 2017-02-08 | 东莞东阳光科研发有限公司 | Slag-making and boron-removing method for industrial silicon |
| CN102923707A (en) * | 2012-11-09 | 2013-02-13 | 朱兴发 | Fusion vacuum processing furnace and productive technology used for producing of 6N grade solar-grade polycrystalline silicon |
| CN105063749B (en) * | 2015-06-08 | 2017-07-18 | 朱超 | A kind of method for preparing high-purity polycrystalline silicon |
| CN109354025B (en) * | 2018-11-19 | 2020-08-18 | 成都斯力康科技股份有限公司 | Composite slagging agent for impurity removal and purification of industrial silicon |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1628076A (en) * | 2002-02-04 | 2005-06-15 | 夏普株式会社 | Silicon purifying method, slag for purifying silicon, and purified silicon |
| 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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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1628076A (en) * | 2002-02-04 | 2005-06-15 | 夏普株式会社 | Silicon purifying method, slag for purifying silicon, and purified silicon |
| 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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