CN101724900B - Device and method for purifying polycrystalline silicon - Google Patents
Device and method for purifying polycrystalline silicon Download PDFInfo
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- CN101724900B CN101724900B CN2009101128961A CN200910112896A CN101724900B CN 101724900 B CN101724900 B CN 101724900B CN 2009101128961 A CN2009101128961 A CN 2009101128961A CN 200910112896 A CN200910112896 A CN 200910112896A CN 101724900 B CN101724900 B CN 101724900B
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Abstract
The invention provides a device and a method for purifying polycrystalline silicon, relates to the polycrystalline silicon, and provides the device and the method for purifying the polycrystalline silicon with lower cost and higher efficiency. The device is provided with a primary smelt crucible, a secondary smelt crucible, a dreg holding crucible after primary slagging and a secondary insulating ladle. The method comprises the following steps: uniformly mixing silicon and dreg and putting the mixture in the primary smelt crucible, putting the dreg in the secondary smelt crucible for heating until the dreg is melted; preheating a stirring rod after materials in the primary smelt crucible are melted; lifting the stirring rod after reaction, and adding BaCO3 into the mixture; turning the primary smelt crucible rightwards for casting after demixing, stopping casting after most silicon solution flows into the secondary smelt crucible and dreg solution starts to flows into the secondary smelt crucible, turning the primary smelt crucible rightwards for casting, and pouring the dreg solution in the secondary smelt crucible into the dreg holding crucible after primary slagging for solidifying; preheating the stirring rod, lifting the stirring rod after the reaction, adding BaCO3 into the secondary smelt crucible, turning the secondary smelt crucible rightwards for casting after demixing, and pouring all melt into the insulating ladle for standing, demixing and solidifying; and grinding and acid pickling silicon after the silicon is taken out, and directionally solidifying the silicon.
Description
Technical field
The present invention relates to a kind of polysilicon, especially relate to a kind of polysilicon purifying plant and method of purification.
Background technology
In recent years, oil price rise steadily and traditional energy is on the rise to the environmental pollution problem and becomes two hang-ups that various countries' sustained economic development faces.Advantages such as sun power is extensive with its distribution, cleanliness without any pollution become an important channel that solves energy dilemma and environmental degradation.At present, the solar cell industry transition material overwhelming majority adopts crystalline silicon material (polysilicon), and its raw material sources mainly are to obtain with chemical process, promptly improve Siemens Method, silane thermal decomposition process and fluidized bed process.These methods are not only invested greatly, energy consumption is high, the cycle is long, and a general production line of producing 1000 tons of polysilicons per year needs more than 1,000,000,000 Renminbi.If handle the recycle of bad by-product silicon tetrachloride, will cause severe contamination to environment.Cost with the polysilicon of chemical method preparation reaches 30～45 dollars/kilogram, and is too expensive for the scale operation of photovoltaic industry.So researching and developing the production technology of the solar-grade polysilicon of a kind of low cost and environmental protection is very important.Physical metallurgy method purifying polycrystalline silicon then provides possibility for this development trend.
The purity requirement that must satisfy about solar-grade polysilicon; Can be for the impurity level that industry is admitted at present: P be below 0.5ppmw; B is below 0.3ppmw; Metallic impurity total contents such as Al, Fe, Ca are less than 0.1ppmw, and it is the P type that while solar cell industry generally also requires the conductive wafer type, is more than the 0.5 Ω cm than resistance.
The technology that physical metallurgy method purifying polycrystalline silicon relates generally to has pickling, air blowing slag making refining, vacuum induction melting, directional freeze, electron beam and beam-plasma melting etc.
The vacuum induction melting removal of impurities mainly is to utilize some impurity element such as P in the silicon, and Al, saturated vapor pressures such as Ca under certain high vacuum, get in the gas phase impurity volatilization much larger than silicon, can obtain good impurity-eliminating effect.People (Noriyoshi Yuge, Kazuhiro Hanazawa, Kohji Nishikawa and Hisaei Terashima such as Noriyoshi Yuge; Removal ofphosphorus; Aluminum and calcium by evaporation in molten silicon [J] .Nippon KinzokuGakkaishi; Journal of the Japan Institute of Metals, 1997,61 (10): result of study 1086) shows; At temperature 1915K, vacuum tightness 8.0 * 10
-3～3.6 * 10
-2Content with phosphorus under the condition of Pa is reduced to below the 0.1ppmw.But in suitability for industrialized production, the experiment condition that obtain the high temperature high vacuum has very high requirement to Equipment Design and manufacturing, and separate unit is long working cycle, is difficult for accomplishing scale production.
Plasma technology is that the high temperature that utilizes plasma gun to produce makes B and H
2O or H
2Generate volatile gases and B is removed Deng the gas reaction of weak oxide property, can B content be reduced to quite low level (being lower than 0.1ppmw), also quite obvious to the removal of C and O simultaneously, like U.S. Pat 5972107; But because the action of plasma scope is little, current consumption is big, handles the time that several kilograms of polysilicons just need h more than.Suitability for industrialized production equipment is complicated and wayward, yields poorly, and cost is high.
Pickling is also referred to as hydrometallurgy, and mainly the metallic impurity reaction through acid (hydrochloric acid, nitric acid and hydrofluoric acid etc.) and silicon powder surface makes it to get into the purpose that reaches removal in the liquid.Acid cleaning process generally can make the purity of industrial silicon reach 4N (simply with Fe, Al, the content summation of Ca is represented).Marvin's can wait (YU Zhan-liang, MA Wen-hui; Removal of iron andaluminum impurities from metallurgical grade-silicon with hydrometallurgical route; Trans.Nonferrous Met.Soc.China; 17 (2007) s1030-s1033) acid cleaning process is carried out comparatively deep exploration, on kind, concentration, consumption, temperature, reaction times and the acid cleaning process of acid, all done certain research.
The ultimate principle of directional solidification technique purifying solar energy level silicon is to utilize the effect of segregation of impurity element in solid phase and liquid phase to reach the purpose of purification, obtains the columanar structure along direction of growth proper alignment through the unidirectional heat current control simultaneously.The directional solidification growth method of polycrystalline silicon used for solar battery ingot commonly used mainly contains teeming practice, Bridgman method, heat-exchanging method (HEM) and electromagnetic casting method (EMC) at present.The technology that mostly adopts heat-exchanging method to combine in the middle of the actual production with Bridgman method.It is emphasized that in the design of directional solidification furnace and must only keep longitudinal temperature gradient, prevent horizontal hot-fluid, the growth velocity of its directional freeze can be brought up to 1.5～2.0cm/h from 0.5cm/h, and grain-size can reach the millimeter level.
Air blowing slag making refining mainly be utilize the thermodynamic stability of the oxide compound of some impurity in slag higher and make impurity more be enriched in slag mutually in, separate removing impurity then through the slag gold.For B impurity, because of its segregation coefficient (0.8) in silicon approaches 1, can't remove, and its boiling point also is difficult to remove under high vacuum up to 2550 ℃ through directional freeze.But the oxide compound of B is easier to get into SiO
2Alkalescence melt in the slag, therefore utilizing slag making to remove B is a kind of effective way.A lot of trials have been carried out in selection for slag former, 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, mostly around the slag gold partition ratio ratio that improves B.Suzuki and Sano (Suzuki, the Sano of Japan; Thermodynamics for removal of boron from metallurgical silicon by flux treatment of moltensilicon; The 10th European Photovoltaic Solar Energy Conference In Lisbon; Portugal 8-12Apr.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, research simultaneously shows that slag gold partition ratio along with the increase of the basicity of slag also can increase to some extent, to a certain degree then begins to descend but be increased to.Lower partition ratio has determined then to need higher slag-metal rate if obtain lower B content; Suppose that the B partition ratio is 2; As to be that 10ppmw reduces to below the 1ppmw from B content with silicon; Then slag silicon partition ratio need be 3: 1, and not only cost is high and once treatable silicon is also comparatively limited for the so big quantity of slag.Na is that the density that the density of slag is generally less than silicon liquid becomes scum silica frost, and the processing of can skimming is handled and reduced use the quantity of slag thereby can add slag in batches, but owing to the slag silicon partition ratio of B is low than Ca, Na
2O at high temperature resolves into simple substance Na and volatile easily, and therefore range of application is little in industry.For P impurity, there are some researches show, in the fused metalluragical silicon, mix a certain amount of Ca, and then the grinding pickling, the content of impurity P drops to less than 5ppmw with 5 times amount.Reason possibly be because P is dissolved in (J.M.Juneja, T.K.Mukherjee in the Calucium Silicate powder; Astudy of the purification of metallurgical grade silicon, Hydrometallurgy, 1986,16:69.).Tomohito Shimpo (Tomohito Shimpo, Takeshi Yoshikawa, the and Kazuki morita of Japan; Thermodynamicstudy of the effect of calcium on removal of phosphorus from silicon by acid leaching treatment; Metallurgical And Materials Transactions B; Volume 35B; April 2004 277-284) comparatively careful Theoretical Calculation and experimental study have been done in the pickling dephosphorization, it points out that when in silicon melt, adding mass ratio be that Ca clearance of P after pickling of 5.17% reaches as high as 80.4%.
Summary of the invention
The object of the present invention is to provide the polysilicon purifying plant that a kind of cost is lower, efficient is higher.
Another object of the present invention is to provide a kind of simple for process, easy to operate, can serialization production, be suitable for the method for purification of the polysilicon of industrialization.
Polysilicon purifying plant according to the invention is provided with to be contained slag crucible, secondary slag making smelting pot and secondary insulation after a slag making smelting pot, the slag making and two-mans ladle; Slag making smelting pot and secondary slag making smelting pot heat through the Medium frequency induction coil; The Medium frequency induction coil is realized two-way upset by the air-operated bi-directional valve gate control; Silicon liquid and a slag of question response are housed in slag making smelting pot, the silicon liquid and the secondary slag of question response is housed in the secondary slag making smelting pot.Slag making smelting pot and secondary slag making smelting pot top are equipped with liftable rotation stirring rod; Being used to quicken slag liquid and silicon liquid fully contacts and reacts; Treat solidified slag liquid after containing a slag making in the Sheng slag crucible after the slag making, treat to treat solidified slag liquid after coagulated silicon liquid and the secondary slag making after the slag making of Sheng secondary in insulation is two-mand ladle.
Said insulation is two-mand ladle to be taken to build by refractory brick and is formed internal spray Si
3N
4Layer.
The method of purification of polysilicon according to the invention may further comprise the steps:
1) with silicon and CaO (40%-60%wt)-SiO
2(30%-50%wt)-CaF
2(5%-20%wt) the slag mixing is put into the slag making smelting pot one time, with CaO (40%-60%wt)-SiO
2(30%-50%wt)-CaF
2(5%-20%wt) slag is put into graphite secondary slag making smelting pot, starts the medium-frequency induction furnace heating, and when temperature rose to 600 ℃, the silicon autonomous induction was given birth to heat, and when temperature reaches 1415 ℃, silicon begins fusing, and temperature continues to rise to slag and begins to melt;
2) treat that the material in the slag making smelting pot melts fully after, the liftable rotation stirring rod that places slag making smelting pot top is reduced to bath surface carries out preheating;
3) treat the preheating fully of liftable rotation stirring rod after, liftable is rotated stirring rod reduces to slag making smelting pot bottom one time, stir, in whipping process, keep melt temperature at 1600～1850 ℃, churning time is 20～120min;
4) question response fully after, liftable is rotated stirring rod rises, add BaCO to melt
3, make melt form the layering of tangible slag silicon with the density that increases slag, the upper strata is a silicon liquid, lower floor is the slag phase;
5) treat abundant layering after; With slag making smelting pot turnover casting to the right; Treat most silicon flows go into secondary slag making smelting pot after beginning have the slag flow to go into, stop the casting; With slag making smelting pot turnover casting left, contain rapid solidification in the slag crucible after pouring the remainder in the secondary slag making smelting pot (slag liquid) into a slag making;
6) will place the liftable rotation stirring rod of secondary slag making smelting pot top to reduce to silicon liquid liquid level and carry out preheating;
7) wait to place the liftable rotation stirring rod preheating fully of secondary slag making smelting pot top after; The liftable rotation stirring rod that places secondary slag making smelting pot top is reduced to crucible bottom; Stir; In whipping process, keep melt temperature at 1600～1850 ℃, churning time is 20～120min;
8) question response fully after, liftable is rotated stirring rod rises, add BaCO to melt
3, make melt form the layering of tangible slag silicon with the density that increases slag, the upper strata is a silicon liquid, lower floor is the slag phase;
9) treat abundant layering after, with secondary slag making smelting pot turnover casting to the right, with the melt in the secondary slag making smelting pot all pour into insulation two-man ladle in standing demix solidify;
10) silicon during insulation is two-mand ladle carries out the crushing and grinding pickling after taking out, and carries out directional freeze at last, polysilicon product.
In step 1), said silicon and CaO (40%-60%wt)-SiO
2(30%-50%wt)-CaF
2(5%-20%wt) slag is preferably 1 by mass ratio: (0.25～4); The power of said medium-frequency induction furnace is preferably 70～200kW, and the temperature that said slag begins to melt is generally about 1530 ℃.
In step 3), the rotating speed that said rotation is stirred can be 120～1200rpm, and preferably rotating speed is 400～600rpm, and the said melt temperature of in whipping process, keeping is preferably 1650～1750 ℃, and churning time is preferably 30～60min.
In step 4), said BaCO
3Add-on be preferably by mass percentage slag total mass 5%～20%.
In step 7), the rotating speed that said rotation is stirred can be 120～1200rpm, and preferably rotating speed is 400～600rpm; The said melt temperature of keeping is preferably 1650～1750 ℃, and said churning time is preferably 30～60min.
In step 8), said BaCO
3Add-on be preferably by mass percentage slag total mass 5%～20%.
The present invention has adopted converter air blowing slag making technology; Make the complete layering of slag silicon through adding the Ba based compound with the density that increases slag; In converter through two-way casting so that slag silicon well separates, avoided after secondary slag making stove is introduced a slag making, containing the slag of P, B and reduce except that P and remove the B effect.The minimum 0.35ppmw that reduces to of B in the present invention, clearance reaches 96.4%, and P is minimum can be to 0.8ppmw, and clearance reaches 94.6%; The present invention is simple to operate, and is lower to the requirement of equipment, less with the quantity of slag; With low cost and dust removal rate is high, but the reaction serialization carry out, be fit to commercial scale prodn.
The present invention utilizes the slag making purifying method to remove crucial detrimental impurity in the silicon, its objective is with the industrial silicon to be raw material, removes wherein P, B and most of metallic impurity through the slag making refining.The HIGH-PURITY SILICON that the present invention obtains is again through follow-up pickling and directional solidification processes, and industrial silicon is purified to solar-grade polysilicon the most at last.
The selected slag former of the present invention system is: CaO-BaO-SiO
2-CaF
2On slagging process,, reduced the remelting operation of silicon, saved energy consumption greatly through adopting converter slag-making; Through adopting two-way casting to realize that slag silicon separates; In the consumption that reduces slag, can obtain well to remove P and remove the B effect, and can realize serialization production, for low-cost solar silicon metallurgy purification provides direction.
Description of drawings
Fig. 1 is that the structure of the polysilicon purifying plant of the embodiment of the invention is formed synoptic diagram.
Embodiment
For the present invention is described, adopting purity is that about 99.5% industrial silicon is a raw material, and wherein P content is about 15ppmw, and B content is about 10ppmw, and Fe content is 2000ppmw, and Al content is 1000ppmw, and Ca content is 500ppmw.
The selected slag former of the present invention system is: CaO-BaO-SiO
2-CaF
2,, pass through SiO earlier in conjunction with phasor and thermodynamic argument
2With the B oxidation, the basicity through CaO adjusting slag system makes being present in the slag system that the oxide compound of B can be more stable on thermodynamics then, utilizes CaF simultaneously
2The viscosity that reduces slag to be to increase flowability and to reduce the fusing point of slag, utilizes density that BaO increases slag to realize good slag silicon layering.The main slag that this slag system forms is CaSiO mutually
3, through slag making, have quite a few P can be dissolved into slag mutually in, separate through slag gold and to remove, some P is combined into Ca with the Ca that incorporates in the silicon in addition
3P
2And stay in the silicon, remove through the crushing and grinding pickling.
Referring to Fig. 1; Polysilicon purifying plant embodiment according to the invention is provided with and contains slag crucible 1, secondary slag making smelting pot 7 and secondary insulation after slag making smelting pot 3, the slag making and two-man ladle 10; Slag making smelting pot 3 and secondary slag making smelting pot 7 heat through Medium frequency induction coil 6; Medium frequency induction coil 6 is realized two-way upset by the air-operated bi-directional valve gate control; Silicon liquid 4 and a slag 5 of question response are housed in slag making smelting pot 3, the silicon liquid 8 and secondary slag 9 of question response is housed in the secondary slag making smelting pot 7.One time slag making smelting pot 3 is equipped with liftable rotation stirring rod 13 with secondary slag making smelting pot 7 tops; Being used to quicken slag liquid and silicon liquid fully contacts and reacts; Contain after the slag making and treat solidified slag liquid 2 after containing a slag making in the slag crucible 1, insulation is two-mand ladle to contain in 10 and is treated after the secondary slag making to treat solidified slag liquid 12 after coagulated silicon liquid 11 and the secondary slag making.
Said insulation is two-mand ladle and 10 is taken to build by refractory brick and form internal spray Si
3N
4Layer.
Below provide and adopt polysilicon purifying plant shown in Figure 1 to carry out the concrete grammar that polysilicon is purified.
1) with silicon and CaO (40%-60%wt)-SiO
2(30%-50%wt)-CaF
2(5%-20%wt) the slag mixing is put into slag making smelting pot 3 one time, with CaO (40%-60%wt)-SiO
2(30%-50%wt)-CaF
2(5%-20%wt) slag is put into graphite secondary slag making smelting pot 7, starts the medium-frequency induction furnace heating, when temperature rises to 600 ℃; Plumbago crucible begins induction heating, and the material in the crucible is carried out preheating, because the resistivity of silicon sharply descends; Electroconductibility strengthens, and the silicon autonomous induction is given birth to heat, when temperature reaches 1415 ℃; Silicon begins fusing, and temperature continues to rise to slag and begins to melt; Said silicon and CaO (40%-60%wt)-SiO
2(30%-50%wt)-CaF
2(5%-20%wt) slag is preferably 1 by mass ratio: (0.25～4); The power of said medium-frequency induction furnace is preferably 70～200kW, and the temperature that said slag begins to melt is generally about 1530 ℃.
2) after treating that the material in the slag making smelting pot 3 melts fully, the liftable rotation stirring rod 13 that places slag making smelting pot 3 tops reduced to apart from bath surface 1cm place carry out preheating;
3) treat 13 preheatings fully of liftable rotation stirring rod after; Liftable is rotated the position that stirring rod 13 is reduced to slag making smelting pot 3 bottom 2cm of distance; Begin rotation and stir, in whipping process, keep melt temperature at 1600～1850 ℃, churning time is 20～120min; The rotating speed that said rotation is stirred can be 120～1200rpm, and preferably rotating speed is 400～600rpm, and the said melt temperature of in whipping process, keeping is preferably 1650～1750 ℃, and churning time is preferably 30～60min.
4) question response fully after, liftable is rotated stirring rod 13 rises, add BaCO to melt
3, make melt form the layering of tangible slag silicon with the density that increases slag, the upper strata is a silicon liquid, lower floor is the slag phase; Said BaCO
3Add-on be preferably by mass percentage slag total mass 5%～20%.
5) treat abundant layering after; Start operated pneumatic valve with slag making smelting pot 3 turnover casting to the right; Treat most silicon flows go into secondary slag making smelting pot 7 after beginning have the slag flow to go into, stop the casting; And start operated pneumatic valve turnover casting left, contain rapid solidification in the slag crucible 1 after pouring the remainders (slag liquid) in the secondary slag making smelting pot 7 into a slag making;
6) will place the liftable rotation stirring rod 14 of secondary slag making smelting pot 7 tops to reduce to and carry out preheating apart from silicon liquid 1cm place;
7) wait to place liftable rotation stirring rod 14 preheatings fully of secondary slag making smelting pot 7 tops after; The liftable rotation stirring rod 14 that places secondary slag making smelting pot 7 tops is reduced to the position apart from crucible bottom 2cm; Beginning rotation stirs; In whipping process, keep melt temperature at 1600～1850 ℃, churning time is 20～120min; The rotating speed that said rotation is stirred can be 120～1200rpm, and preferably rotating speed is 400～600rpm; The said melt temperature of keeping is preferably 1650～1750 ℃, and said churning time is preferably 30～60min.
8) question response fully after, stirring rod is risen, continuing slowly to add total amount to melt is the BaCO of the quantity of slag 5% to 20%
3Density to increase slag makes melt form the layering of tangible slag silicon, and the upper strata is a silicon liquid, and lower floor is a slag liquid.
9) treat abundant layering after, start operated pneumatic valve with crucible 7 turnover casting to the right, all pour the melt in the crucible into insulation and two-man ladle that standing demix solidifies in 10.
10) silicon in will two-maing ladle carries out the crushing and grinding pickling after taking out, and carries out directional freeze at last.
Below provide specific embodiment.
Embodiment 1
With the silicon (piece material) of 150kg and CaO (53%wt)-SiO of 150kg
2(40%wt)-CaF
2(7%wt) slag (slag silicon ratio is 1: 1) mixing is put into slag making smelting pot 3 one time, with CaO (53%wt)-SiO of 150kg
2(40%wt)-CaF
2(7%wt) slag is put into secondary slag making smelting pot 7; Start heating in medium frequency, power is controlled at 70KW-200KW, treats after silicon and slag melt fully stirring rod to be reduced to the top preheating of silicon liquid; Fully after the preheating stirring rod is inserted 2cm place at the bottom of the crucible; Rotating speed with 400rpm stirs, and temperature of reaction is controlled at about 1700 ℃, and the reaction times is 1h.After the slag making fully the graphite stirring rod is lifted away from silicon liquid, in melt, slowly add the BaCO of 20kg continuously
3After treating the obvious layering of slag silicon; Start the slow uphill casting of air-operated bi-directional valve door to the right; Treat that most silicon flows go into secondary slag making smelting pot 7 and after beginning have the slag flow to go into, stop casting, and start operated pneumatic valve turnover casting left, contain rapid solidification in the slag crucible 1 after pouring the remainder in the crucible into a slag making.With after the graphite stirring rod preheating that places secondary slag making smelting pot 7 tops fully stirring rod being inserted 2cm place at the bottom of the crucible, stir with the rotating speed of 400rpm, temperature of reaction is controlled at about 1700 ℃, and the reaction times is 1h.After the slag making fully the graphite stirring rod is lifted away from silicon liquid, in melt, slowly add the BaCO of 20kg continuously
3, treat the obvious layering of slag silicon after, turnover casting to the right.Melt solidifies behind the standing demix in insulation is two-mand ladle gradually.After cooling silicon is carried out the crushing and grinding pickling, in heat-exchanging furnace, carry out directional freeze then.Detected by the sampling of 30% length place, lower end after taking out silicon ingot, P content is 1ppmw, and B content is 0.5ppmw, and the purity of polysilicon is 99.99974%.
Technological process is with embodiment 1.The silicon material is 200kg, and slag is 100kg, and slag silicon ratio is 1: 2, and the composition of slag is with embodiment 1.The stirring rod rotating speed is 600rpm, and temperature of reaction is controlled at about 1700 ℃, and the reaction times is 30min.BaCO
3Add-on is 20Kg, and sampling at last detects, and P content is 2ppmw, and B content is 0.8ppmw, and the purity of polysilicon is 99.9996%.
Embodiment 3
Technological process is with embodiment 1.The silicon material is 200Kg, and slag is 100kg, and slag silicon ratio is 1: 2, and the composition of slag is CaO (40%wt)-SiO
2(40%wt)-CaF
2(20%wt), the stirring rod rotating speed is 600rpm, and temperature of reaction is controlled at about 1700 ℃, and the reaction times is 30min.BaCO
3Add-on is 20kg, and sampling at last detects, and P content is 3ppmw, and B content is 1.2ppmw, and the purity of polysilicon is 99.9994%.
Embodiment 4
Technological process is with embodiment 1.The silicon material is 200Kg, and slag is 100Kg, and slag silicon ratio is 1: 2, and the composition of slag is CaO (40%wt)-SiO
2(40%wt)-CaF
2(20%wt), the stirring rod rotating speed is 400rpm, and temperature of reaction is controlled at about 1750 ℃, and the reaction times is 60min.BaCO
3Add-on is 10kg, and sampling at last detects, and P content is 2.7ppmw, and B content is 1.1ppmw, and the purity of polysilicon is 99.9995%
For advantage of the present invention is described, below provide Comparative Examples.
Comparative Examples 1
With the silicon (piece material) of 150kg and CaO (53%wt)-SiO of 150kg
2(40%wt)-CaF
2(7%wt) slag (slag silicon ratio is 1: 1) mixing is put into slag making smelting pot 3 one time, with CaO (53%wt)-SiO of 150Kg
2(40%wt)-CaF
2(7%wt) slag is put into secondary slag making smelting pot 7; Start heating in medium frequency, power is controlled at 70～200kW, treats after silicon and slag melt fully stirring rod to be reduced to the top preheating of silicon liquid; Fully after the preheating stirring rod is inserted 2cm place at the bottom of the crucible; Rotating speed with 400rpm stirs, and temperature of reaction is controlled at about 1700 ℃, and the reaction times is 1h.After the slag making fully the graphite stirring rod is lifted away from silicon liquid, turnover casting to the right.
With after the graphite stirring rod preheating that places secondary slag making smelting pot 7 tops fully stirring rod being inserted 2cm place at the bottom of the crucible, stir with the rotating speed of 400rpm, temperature of reaction is controlled at about 1700 ℃, and the reaction times is 1h.After the slag making fully the graphite stirring rod is lifted away from silicon liquid turnover casting to the right.Melt solidifies behind the standing demix in insulation is two-mand ladle gradually.After cooling silicon is carried out the crushing and grinding pickling, in heat-exchanging furnace, carry out directional freeze then.Detected by the sampling of 30% length place, lower end after taking out silicon ingot, P content is 3ppmw, and B content is 1.5ppmw, and the purity of polysilicon is 99.9994%.
Comparative Examples 2
Technological process is with embodiment 1.Do not add BaCO
3, slag silicon separation case is relatively poor in the converter process, and sampling at last detects, and P content is 1.7ppmw, and B content is 0.74ppmw, the purity of polysilicon is 99.99966%
Through the simultaneous test explanation of embodiment 1 with Comparative Examples 1 and 2, the present invention adopts and adds BaCO
3The density that increases slag is so that the remarkable layering of slag silicon and take two-way casting to separate the removal effect that can significantly improve impurity P, B to realize good slag silicon.
Claims (11)
1. polysilicon purifying plant; It is characterized in that being provided with and contain slag crucible, secondary slag making smelting pot and secondary insulation after a slag making smelting pot, the slag making and two-man ladle; Slag making smelting pot and secondary slag making smelting pot heat through the Medium frequency induction coil; The Medium frequency induction coil is realized two-way upset by the air-operated bi-directional valve gate control, and silicon liquid and slag of question response is housed in slag making smelting pot, and the silicon liquid and the secondary slag of question response is housed in the secondary slag making smelting pot; Slag making smelting pot and secondary slag making smelting pot top are equipped with liftable rotation stirring rod; Be used to quicken slag liquid and silicon liquid and fully contact and react, contain after the slag making and treat solidified slag liquid after containing a slag making in the slag crucible, treat to treat solidified slag liquid after coagulated silicon liquid and the secondary slag making after containing the secondary slag making in insulation is two-mand ladle.
2. a kind of polysilicon purifying plant as claimed in claim 1 is characterized in that said insulation two-mans ladle to be taken to build by refractory brick to form internal spray Si
3N
4Layer.
3. the method for purification of polysilicon is characterized in that adopting a kind of according to claim 1 polysilicon purifying plant, and said method of purification may further comprise the steps:
1) with silicon and CaO (40%-60%wt)-SiO
2(30%-50%wt)-CaF
2(5%-20%wt) the slag mixing is put into the slag making smelting pot one time, with CaO (40%-60%wt)-SiO
2(30%-50%wt)-CaF
2(5%-20%wt) slag is put into graphite secondary slag making smelting pot, starts the medium-frequency induction furnace heating, and when temperature rose to 600 ℃, the silicon autonomous induction was given birth to heat, and when temperature reaches 1415 ℃, silicon begins fusing, and temperature continues to rise to slag and begins to melt;
2) treat that the material in the slag making smelting pot melts fully after, the liftable rotation stirring rod that places slag making smelting pot top is reduced to bath surface carries out preheating;
3) treat the preheating fully of liftable rotation stirring rod after, liftable is rotated stirring rod reduces to slag making smelting pot bottom one time, stir, in whipping process, keep melt temperature at 1600～1850 ℃, churning time is 20～120min;
4) question response fully after, liftable is rotated stirring rod rises, add BaCO to melt
3, melt forms the layering of slag silicon, and the upper strata is a silicon liquid, and lower floor is the slag phase;
5) treat abundant layering after; With slag making smelting pot turnover casting to the right; Treat that most silicon flows go into secondary slag making smelting pot and after beginning have the slag flow to go into, stop casting, contain rapid solidification in the slag crucible after pouring the slag liquid in slag making smelting pot into a slag making;
6) will place the liftable rotation stirring rod of secondary slag making smelting pot top to reduce to silicon liquid liquid level and carry out preheating;
7) wait to place the liftable rotation stirring rod preheating fully of secondary slag making smelting pot top after; The liftable rotation stirring rod that places secondary slag making smelting pot top is reduced to crucible bottom; Stir; In whipping process, keep melt temperature at 1600～1850 ℃, churning time is 20～120min;
8) question response fully after, liftable is rotated stirring rod rises, add BaCO to melt
3, melt forms the layering of tangible slag silicon, and the upper strata is a silicon liquid, and lower floor is the slag phase;
9) treat abundant layering after, with secondary slag making smelting pot turnover casting to the right, with the melt in the secondary slag making smelting pot all pour into insulation two-man ladle in standing demix solidify;
10) silicon during insulation is two-mand ladle carries out the crushing and grinding pickling after taking out, and carries out directional freeze at last, polysilicon product.
4. the method for purification of polysilicon as claimed in claim 3 is characterized in that in step 1), said silicon and CaO (40%-60%wt)-SiO
2(30%-50%wt)-CaF
2(5%-20%wt) slag is 1: 0.25～4 by mass ratio.
5. the method for purification of polysilicon as claimed in claim 3 is characterized in that in step 1), and the power of said medium-frequency induction furnace is 70～200kW, and the temperature that said slag begins to melt is 1530 ℃.
6. the method for purification of polysilicon as claimed in claim 3 is characterized in that in step 3), and the rotating speed of said stirring is 120～1200rpm; The said melt temperature of in whipping process, keeping is 1650～1750 ℃, and churning time is 30～60min.
7. the method for purification of polysilicon as claimed in claim 3 is characterized in that in step 4), said BaCO
3Add-on be by mass percentage slag total mass 5%～20%.
8. the method for purification of polysilicon as claimed in claim 3 is characterized in that in step 7), and the rotating speed of said stirring is 120～1200rpm; The said melt temperature of keeping is 1650～1750 ℃, and said churning time is 30～60min.
9. the method for purification of polysilicon as claimed in claim 6, the rotating speed that it is characterized in that said stirring is 400～600rpm.
10. the method for purification of polysilicon as claimed in claim 8, the rotating speed that it is characterized in that said stirring is 400～600rpm.
11. the method for purification of polysilicon as claimed in claim 3 is characterized in that in step 8), said BaCO
3Add-on be by mass percentage slag total mass 5%～20%.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101920960B (en) * | 2010-06-29 | 2012-07-25 | 华南师范大学 | Method for preparing solar grade polysilicon by metallurgy method and polysilicon prepared thereby |
| CN102153088B (en) * | 2011-02-18 | 2012-08-15 | 厦门大学 | Method for carrying out slagging, pickling and boron removal on metal silicon |
| CN102139880B (en) * | 2011-05-16 | 2013-07-31 | 青岛隆盛晶硅科技有限公司 | Method for removing impurity boron in polycrystalline silicon by electron beam slagging smelting |
| CN103011170A (en) * | 2012-12-31 | 2013-04-03 | 大连理工大学 | Method for purifying polysilicon through silicon alloy slagging |
| CN103072998B (en) * | 2013-02-04 | 2014-05-07 | 福建兴朝阳硅材料股份有限公司 | Method for preparing low-phosphorus-boron polycrystalline silicon through two-man ladle refining |
| CN103172381B (en) * | 2013-04-08 | 2014-03-26 | 无锡中彩科技有限公司 | Preparation method and applications of cold-wall fluidized bed |
| CN103523784B (en) * | 2013-10-12 | 2015-02-04 | 云南永昌硅业股份有限公司 | Ladle baking method in silicon smelting process |
| CN103553050B (en) * | 2013-10-25 | 2016-03-02 | 青岛隆盛晶硅科技有限公司 | Polysilicon serialization medium melting method |
| CN105063749B (en) * | 2015-06-08 | 2017-07-18 | 朱超 | A kind of method for preparing high-purity polycrystalline silicon |
| CN107099841B (en) * | 2017-04-24 | 2019-02-26 | 武汉理工大学 | A kind of method that short route, high efficiency and inexpensive purification prepare polycrystalline silicon used for solar battery |
| CN112624122B (en) * | 2021-01-12 | 2022-06-14 | 昆明理工大学 | Method and device for preparing 6N polycrystalline silicon by refining industrial silicon through vacuum microwave |
| CN114572988A (en) * | 2022-03-14 | 2022-06-03 | 城固县鑫弘矿业有限责任公司 | External refining and purifying method for industrial silicon |
| CN117387378B (en) * | 2023-12-12 | 2024-04-16 | 陕西煜成和汇金属材料有限公司 | Slag skimming device of electron beam melting furnace |
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| CN101255598A (en) * | 2007-12-17 | 2008-09-03 | 史珺 | Method for preparing solar energy grade polycrystalline silicon |
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