CN102807220A - Silicon purification method - Google Patents
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- CN102807220A CN102807220A CN2011101440397A CN201110144039A CN102807220A CN 102807220 A CN102807220 A CN 102807220A CN 2011101440397 A CN2011101440397 A CN 2011101440397A CN 201110144039 A CN201110144039 A CN 201110144039A CN 102807220 A CN102807220 A CN 102807220A
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Abstract
The present invention provides a silicon purification method. The method comprises: mixing a raw material silicon and a co-melted metal, and carrying out heating melting to obtain a mixed liquid; introducing slagging gas to the mixed liquid, and adding a slagging agent to the mixed liquid to carry out gas blowing slagging refining; and then carrying out crushing and acid washing, wherein the co-melted metal comprises one or a plurality of materials selected from aluminum, zinc or titanium. By adopting the method of the present invention to purify industrial silicon, boron impurity content in the resulting polycrystalline silicon is low, a solar energy level requirement is met, and the method has a characteristic of simple process, and is easy to industrially perform.
Description
Technical field
The present invention relates to a kind of method of purification of silicon, especially a kind of method of purification of industrial silicon.
Background technology
In recent years, oil price rise steadily and traditional energy environmental pollution problem serious day by day, this has become 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, and energy consumption is high, the cycle is long, and the production line of producing 1000 tons of polysilicons a general year needs more than 1,000,000,000 Renminbi.If handle badly, the recycle of by-product silicon tetrachloride will cause severe contamination to environment.Cost with the polysilicon of chemical method preparation reaches 30-45 dollar/kilogram, costliness too 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.The physical metallurgy 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: phosphorus be below 0.5ppm; Boron is below 0.3ppm; Metals content impurities such as iron, calcium, aluminium are less than 0.1ppm, 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.
At present, the technology that relates generally to of physical metallurgy method purifying polycrystalline silicon has pickling, slag making refining, vacuum induction melting, directional freeze, electron beam and plasma melting etc.
The vacuum induction melting removal of impurities mainly is to utilize saturated vapor pressures such as some impurity element such as P in the silicon, Al, Ca much larger than silicon, under certain high vacuum, the impurity volatilization is got in the gas phase, can obtain good impurity-eliminating effect.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 B and H when utilizing the high temperature that plasma gun produces
2O or H
2Thereby Deng gas reaction generation volatile gases B is removed, can B content be reduced to quite low level (being lower than 0.1ppm), must remove also quite obvious to C and O simultaneously.But because the action of plasma scope is little, power consumption is big, and handling several kilograms of polysilicons just needs more than one hour time.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 and silicon face makes it to get into the purpose that reaches removal in the liquid.But this method is not obvious to the removal effect of boron impurities.
The ultimate principle of directional solidification technique purifying solar energy level polysilicon 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.
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 boron impurity, because of its segregation coefficient (being 0.8) in silicon is bordering on 1, can't remove through directional freeze, and its boiling point height to 2550 ℃, under high vacuum, also be difficult to remove.But the oxide compound of boron is easier to get in the basic slag of silicon-dioxide, is beneficial to removing of boron.
But existing air blowing slagging boron removal effect is unsatisfactory, and the content of boron impurities is still higher.
Summary of the invention
For overcome in the prior art industrial silicon purified after, boron impurities content is problem of higher still, the invention discloses a kind of method of purification of silicon, the polysilicon boron impurities content that obtains after through this method industrial silicon being purified is low, reaches the solar level requirement.
The method of purification of silicon disclosed by the invention comprises raw silicon and melts metal mixed and heating and melting altogether, obtains mixed solution; In mixed solution, feed slag making gas then and add slag former, the slag making refining of blowing; Pulverize again and pickling; The said metal that melts altogether is selected from aluminium, zinc or the titanium one or more.
Among the present invention, through at first raw silicon being melted the common fusion of metal (for example aluminium) together, and then through the air blowing slag practice; And combination pickling; Can go out boron impurities in the raw silicon to a great extent, improve the purity of silicon greatly, meet the requirement of solar-grade polysilicon.The contriver finds; Form alloy system (for example Si-Al alloy system) after raw silicon melted the common fusion of metal (for example aluminium) together, and the impurity B in the raw silicon can melt together metal (for example aluminium) form more stable, after boron impurities melts metal (for example aluminium) contact together; Can form stable intermediate compound (the for example intermediate compound of Al-B); Thereby boron is brought in the slag charge, and along with the removal of slag charge, the boron impurities in the raw silicon is gone out immediately; And residue in intermediate compound dissolved the removing in follow-up acid cleaning process in the mixed solution, thereby greatly reduce the content of the boron impurities in the silicon.
And above-mentioned method of purification is simple for process, is convenient to industry and goes up extensive enforcement.
Embodiment
Clearer for technical problem, technical scheme and beneficial effect that the present invention is solved, below in conjunction with embodiment, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explanation the present invention, and be not used in qualification the present invention.
The method of purification of silicon disclosed by the invention comprises raw silicon and melts metal mixed and heating and melting altogether, obtains mixed solution; In mixed solution, feed slag making gas then and add slag former, the slag making refining of blowing; Pulverize again and pickling; The said metal that melts altogether is selected from aluminium, zinc or the titanium one or more.
The raw silicon that adopts in the above-mentioned method of purification is the industrial silicon that is used to prepare solar-grade polysilicon well known in the art, like purity greater than 98.0% raw silicon.Above-mentioned raw materials silicon can be commercially available.The present invention can be that silica flour also can be a silico briquette for the not restriction of shape of raw silicon.
According to the present invention, the metal that melts altogether that adopts in the above-mentioned method of purification is preferably aluminium, and wherein, aluminium is aluminium of the prior art, is preferably rafifinal, and its purity is greater than 99.0%.Further optimize silicon purification system, avoid introducing other impurity.
Among the present invention; With raw silicon with when melting metal mixed altogether, the two content can change in a big way, under the preferable case; Said weight ratio of melting metal and raw silicon altogether is 0.05-5: 1, and the weight ratio of more preferably melting metal and raw silicon altogether is 0.125-0.3: 1.
Can carry out heating and melting with a certain amount of raw silicon with after melting metal mixed altogether.Above-mentioned heating and melting can carry out in the equipment that this area is used always, for example can adopt induction furnace to heat.Under the preferable case, elder generation is with raw silicon and melt the induction furnace that metal places plumbago crucible altogether, is to heat under the 60-80KW at induction furnace power, obtains the fused mixed solution.As long as the not special restriction of above-mentioned heat temperature raising process is can be with raw silicon and melt metal melting altogether.
Obtain the slag making refining of to blow after the mixed solution.
According to the present invention, the slag making gas that feeds during the air blowing slag making contains water vapour at least, contains carrier gas simultaneously; Said carrier gas is selected from a kind of in the gas mixture of gas mixture, rare gas element and oxygen of air, nitrogen, rare gas element, nitrogen and oxygen.Wherein, the vector gas effect in the slag making gas of the present invention is: the dilution water steam can increase the flow of mixed gas.
Under the preferable case, said carrier gas is an air, is benchmark with the TV of said air and water vapour, and the volume of said air accounts for 80-99.9%, and the volume of said water vapour accounts for 0.1-20%.Similarly, said carrier gas can also be the gas mixture of nitrogen and oxygen or the gas mixture of rare gas element and oxygen, and wherein, nitrogen or rare gas element account for the 60-98% of slag making volume of gas, and oxygen accounts for 5-30%, and water vapour accounts for 1-35%.Further be preferably, nitrogen or rare gas element account for the 70-85% of slag making volume of gas, and oxygen accounts for 15-23%, and water vapour accounts for 15-30%.
When carrier gas was above-mentioned all gases, oxygen wherein (or airborne oxygen) and water changed into the oxide compound of boron and the oxyhydroxide of boron (BOH) with boron
nWherein, the oxyhydroxide of boron is gaseous state, can overflow with air, reaches the purpose of removal of impurities.In addition; When containing oxygen in the carrier gas, can the part in the mixed solution be melted metal (for example aluminium) oxidation altogether, when silicon melts metal (for example aluminium) formation alloy (for example Si-Al alloy) together simultaneously; Melt metal (for example aluminium) altogether and can form more stable intermediate compound (for example Al-B) with boron; Can combine with slag former and will melt the oxide compound (for example aluminum oxide) that metal (for example aluminium) oxidation obtains altogether, thereby boron impurities is brought in the slag charge, through follow-up separation; Can effectively boron impurities be gone out, thereby further reduce the content of boron impurities.
Above-mentioned rare gas element is well known in the art, is 0 family's gas, argon gas more preferably among the present invention.
Under the preferable case, the present invention adopts the porous swivel nozzle in silicon liquid, to feed mixed gas.
Before feeding slag making gas, preferably the porous swivel nozzle is carried out preheating on the mixed solution surface, be preferably in 4-6min warm up time.Then that preheating is good porous swivel nozzle is inserted in the mixed solution, and preferred porous swivel nozzle is inserted into the place apart from container bottom 15-25mm.
After the ventilation beginning, the rotating speed of porous swivel nozzle is preferably 200-500rad/min.
The flow that feeds mixed gas is preferably 300-500l/h, more preferably 350-450l/h.
In fusion process, continue to feed slag making gas, the aeration time of slag making gas is preferably 50-80min, more preferably 60-70min.
When feeding gas, in mixed solution, add slag former.
According to the present invention, above-mentioned slag former can adopt the slag former of various systems of the prior art, for example CaO-SiO
2, Na
2O-SiO
2, CaO-SiO
2-CaF
2, CaO-MgO-SiO
2, CaO-BaO-SiO
2Deng.
Among the present invention, said slag former is preferably Na
2O-SiO
2-CaF
2System, that is, said slag former contains Na
2O, SiO
2And CaF
2Concrete, in the said slag former, Na
2The content of O is 10-65wt%, SiO
2Content be 15-85wt%, CaF
2Content be 1-50wt%; Na more preferably
2The content of O is 15-55wt%, SiO
2Content be 25-65wt%, CaF
2Content be 3-20wt%.
Among the present invention, when adopting the slag former of above-mentioned system, the oxygen G&W in the slag making gas that in mixed solution, feeds changes into the oxide compound of boron and the oxyhydroxide of boron (BOH) with boron
nAfter, the oxide compound of the boron of formation can highly stable being present in the above-mentioned slag former system.As previously mentioned, the oxyhydroxide of boron overflows with the form of gas; And melting altogether after metal (for example aluminium) oxidation forms oxide compound in the mixed solution can better be compatible with slag charge, thereby can the more effective boron impurities of removing.
In addition, CaF
2Thereby the viscosity that can reduce slag charge increases the flowability of slag and CaF
2Can reduce the fusing point of slag; The main slag that this slag charge forms is Na mutually
2SiO
3, through slag making, have quite a few foreign matter of phosphor (P) can incorporate slag mutually in, thereby reach the effect of removing boron impurities and phosphorus simultaneously.
According to the present invention, the addition of said slag former can change in a big way, and under the preferable case, the weight ratio of said slag former and raw silicon is 0.1-10: 1, and 0.5-3 more preferably: 1.
Under the preferable case,, reduce the content of impurity, in said air blowing slag making refining process, can the slag charge that produce be removed, promptly in the air blowing slag making, slag charge is removed in order further to improve the separate impurities degree.Above-mentioned method of removing slag charge does not limit, and for example can directly the slag charge that floats on the mixed solution surface be pulled out to get final product.
As to further improvement of the present invention, under the preferable case, after above-mentioned air blowing slag making processing, can also carry out directional freeze to the mixed solution after the air blowing slag making.In early stage silicon is melted metal (for example aluminium) together and melt altogether, and through specific slag former (Na
2O-SiO
2-CaF
2) after the air blowing slag making handles,, when removing impurity such as P, Al, Ca, can further remove boron impurities through directional freeze, improve the purity of silicon.
Under the preferable case, the starting temperature of said directional freeze is 1000-1500 ℃.Travelling speed from bottom to top is 0.05-1.0mm/min.
After above-mentioned air blowing slag making processing or directional freeze processing, can the product that obtain be cooled off, and pulverize, under the preferable case, said pulverization process makes the particle diameter of silicon grain be crushed to 1-1000um, obtains silicon grain.
According to the present invention, also need the silicon grain that obtains after pulverizing is carried out pickling.Through the above-mentioned silicon grain for preparing is carried out pickling,, can reduce the content of impurity greatly in conjunction with the air blowing slag making refining in early stage.
Above-mentioned pickling can be pickling well known in the art, and under the preferable case, said pickling comprises preliminary pickling and white picking; Said preliminary pickling is carried out in first acid solution, and is concrete, can above-mentioned silicon grain be soaked in first acid solution.Said first acid solution is selected from a kind of in hydrochloric acid, sulfuric acid, the hydrofluoric acid.
For above-mentioned preliminary pickling, can under 45-85 ℃, carry out.Wherein, Sorensen value can change in a big way in first acid solution, is preferably 0.2-8mol/L.The time of preliminary pickling also can change in a big way, and under the preferable case, the time of preliminary pickling is 2-24h.
Said white picking is carried out in second acid solution, and is same, can the silicon grain that pass through after the preliminary pickling be soaked in second acid solution, and said second acid solution is the mixing acid of a kind of composition in nitric acid and hydrochloric acid, the sulfuric acid.
For above-mentioned white picking, can under 25-45 ℃, carry out.Wherein, under the preferable case, Sorensen value is 0.2-8mol/L in said second acid solution.The time of white picking is 8-24h.Above-mentioned second acid solution is a mixing acid, and under the preferable case, said second acid solution is a chloroazotic acid, contains nitric acid and hydrochloric acid in promptly said second acid solution.
When adopting aforesaid method to carry out pickling, can be with residuing in intermediate compound in the mixed solution (AlB for example
2And AlB
12) effectively and fully remove, thereby reduce the foreign matter content in the silicon grain greatly, improve the purity of silicon.
Further under the preferable case, after above-mentioned preliminary pickling and white picking, adopt washed with de-ionized water respectively to neutral, and oven dry.
Through embodiment the present invention is further explained below.
The raw silicon that adopts in the embodiment of the invention and the Comparative Examples is same source; Wherein, Measure through inductive coupling plasma emission spectrograph (ICP-AES) that wherein the foreign matter content situation is following, B:66.355ppm, P:49.405ppm, Fe:1708ppm, Al:682.2ppm, Ti:282.95ppm, Ca:60.39ppm.
Embodiment 1
Present embodiment is used to explain the method for purification of silicon disclosed by the invention.
100 weight part raw silicons and 50 weight part zinc (purity is 99.5%) mixing are put to induction furnace, and heating and melting obtains mixed solution.
To be connected with the porous swivel nozzle of slag making gas (90 parts by volume nitrogen+10 parts by volume water vapour) then, reduce to preheating 5min on the silicon liquid surface.With being inserted in the mixed solution under the porous swivel nozzle, stop to insert down then at 15mm place at the bottom of high-purity silica pot.Feed slag making gas, the pilot-gas flow is 400l/h, and the rotating speed of porous swivel nozzle is 400rad/min.Simultaneously with the 66.7 weight part slag former (Na of 20wt%
2O, the SiO of 40wt%
2, the CaF of 6.7wt%
2) be brought in the above-mentioned mixed solution, the slag making of blowing is handled.
With the mixed solution cooling after the air blowing slag making processing, ingot casting peeling, pulverizing, obtain the silicon grain that particle diameter is 55um-268um.
With above-mentioned silicon grain pickling 5h in 52 ℃ hydrochloric acid soln (concentration is 3.1mol/l), in 45 ℃ deionized water, clean 3h then.The silicon grain that to wash again is pickling 12h in 31 ℃ second acid solution (Sorensen value is 4.3mol/l, chloroazotic acid), and then extremely neutral with washed with de-ionized water, oven dry.Obtain product silicon S1.
Embodiment 2
Present embodiment is used to explain the method for purification of silicon disclosed by the invention.
100 weight part raw silicons and 8 weight part aluminium (purity is 99.5%) mixing are put to induction furnace, and heating and melting obtains mixed solution.
To be connected with the porous swivel nozzle of slag making gas (92 parts by volume air+8 parts by volume water vapour) then, reduce to preheating 5min on the silicon liquid surface.With being inserted in the mixed solution under the porous swivel nozzle, stop to insert down then at 15mm place at the bottom of high-purity silica pot.Feed slag making gas, the pilot-gas flow is 400l/h, and the rotating speed of porous swivel nozzle is 400rad/min.Simultaneously with the 83.3 weight part slag former (Na of 31.2wt%
2O, the SiO of 45wt%
2, the CaF of 7.1wt%
2) join in the above-mentioned mixed solution, the slag making of blowing is handled.
With the mixed solution cooling after the air blowing slag making processing, ingot casting peeling, pulverizing, obtain the silicon grain that particle diameter is 49um-254um.
Above-mentioned silicon grain is soaked 5h in 60 ℃ hydrochloric acid soln (concentration is 4mol/l), in 45 ℃ deionized water, clean 3h then.The silicon grain that to wash again soaks 12h in 31 ℃ second acid solution (Sorensen value is 5.4mol/l, chloroazotic acid), and then extremely neutral with washed with de-ionized water, oven dry.Obtain product silicon S2.
Embodiment 3
Present embodiment is used to explain the method for purification of silicon disclosed by the invention.
100 weight part raw silicons and 15.8 weight part aluminium (purity is 99.5%) mixing are put to induction furnace, and heating and melting obtains mixed solution.
To be connected with the porous swivel nozzle of slag making gas (70 parts by volume argon gas+22 parts by volume oxygen+8 parts by volume water vapour) then, reduce to preheating 5min on the silicon liquid surface.With being inserted in the mixed solution under the porous swivel nozzle, stop to insert down then at 15mm place at the bottom of high-purity silica pot.Feed slag making gas, the pilot-gas flow is 400l/h, and the rotating speed of porous swivel nozzle is 400rad/min.Simultaneously with the 67.6 weight part slag former (Na of 30wt%
2O, the SiO of 32.3wt%
2, the CaF of 5.3wt%
2) join in the above-mentioned mixed solution, the slag making of blowing is handled.
Silicon after the air blowing slag making processing is carried out directional freeze, and the starting temperature of said directional freeze is 1302 ℃, and travelling speed from bottom to top is 0.15mm/min
With the peeling of the silicon ingot after the directional freeze, pulverizing, obtain the silicon grain that particle diameter is 106-598um then.
Above-mentioned silicon grain is soaked 5h in 52 ℃ hydrochloric acid soln (concentration is 3.1mol/l), in 45 ℃ deionized water, clean 3h then.The silicon grain that to wash again soaks 12h in 30.6 ℃ second acid solution (Sorensen value is 6mol/l, chloroazotic acid), and then extremely neutral with washed with de-ionized water, oven dry.Obtain product silicon S3.
Embodiment 4
Present embodiment is used to explain the method for purification of silicon disclosed by the invention.
100 weight part raw silicons and 17 weight part aluminium (purity is 99.5%) mixing are put to induction furnace, and heating and melting obtains mixed solution.
To be connected with the porous swivel nozzle of slag making gas (78 parts by volume nitrogen+8 parts by volume oxygen+24 parts by volume water vapour) then, reduce to preheating 5min on the silicon liquid surface.With being inserted in the mixed solution under the porous swivel nozzle, stop to insert down then at 15mm place at the bottom of high-purity silica pot.Feed slag making gas, the pilot-gas flow is 400l/h, and the rotating speed of porous swivel nozzle is 400rad/min.Simultaneously with the 73 weight part slag former (Na of 28wt%
2O, the SiO of 40wt%
2, the CaF of 5wt%
2) join in the above-mentioned mixed solution, the slag making of blowing is handled.
Silicon after the air blowing slag making processing is carried out directional freeze, and the starting temperature of said directional freeze is 1130 ℃, and travelling speed from bottom to top is 0.65mm/min
With the peeling of the silicon ingot after the directional freeze, pulverizing, obtain the silicon grain that particle diameter is 502-952um then.
Above-mentioned silicon grain is soaked 9h in 59 ℃ hydrochloric acid soln (concentration is 6mol/l), in 45 ℃ deionized water, clean 3h then.The silicon grain that to wash again soaks 12h in 34 ℃ second acid solution (Sorensen value is 5.2mol/l, chloroazotic acid), and then extremely neutral with washed with de-ionized water, oven dry.Obtain product silicon S4.
Embodiment 5
Present embodiment is used to explain the method for purification of silicon disclosed by the invention.
Adopt the method purified silicon identical with embodiment 4, different is in the acid cleaning process, in the air blowing slagging process, repeatedly pulls the slag charge of formation out.
Obtain product silicon S5.
Embodiment 6
Present embodiment is used to explain the method for purification of silicon disclosed by the invention.
Adopt the method purified silicon identical with embodiment 4, different is in the acid cleaning process, only silicon grain is carried out pickling in hydrochloric acid soln, in second acid solution, does not carry out pickling.
Obtain product silicon S6.
Comparative Examples 1
This Comparative Examples is used for the method for purification of comparative illustration silicon disclosed by the invention.
Adopt the method purified silicon identical with embodiment 2, different is not add aluminium in the heating and melting process, only with the raw silicon fusion.
Obtain product silicon D1.
Comparative Examples 2
This Comparative Examples is used for the method for purification of comparative illustration silicon disclosed by the invention.
Adopt the method purified silicon identical with embodiment 6, different is not add aluminium in the heating and melting process, only with the raw silicon fusion.
Obtain product silicon D2.
Performance test
The product silicon S1-S6 that above-mentioned purification is obtained, D1, D2 are with nitric acid and hydrofluoric acid dissolution; In inductive coupling plasma emission spectrograph (ICP-AES); Under thousand grades of purification conditions, test the content of boron impurities in above-mentioned each product silicon, phosphorus, iron, aluminium, calcium, titanium.
The test result that obtains is inserted table 1.
Table 1
| Sample | Boron/ppm | Phosphorus/ppm | Iron/ppm | Aluminium/ppm | Titanium/ppm | Calcium/ppm |
| Raw silicon | 66.355 | 49.405 | 1708 | 682.2 | 282.95 | 60.39 |
| S1 | 0.05921 | 0.8153 | 1.219 | 0.1516 | 1.485 | 0.6584 |
| S2 | 0.04685 | 0.2584 | 2.682 | 0.2586 | 1.358 | 0.3504 |
| S3 | 0.03658 | 0.2154 | 0.05468 | 0.8456 | 0.03801 | 0.05411 |
| S4 | 0.02815 | 0.1513 | 0.05841 | 0.5236 | 0.02354 | 0.02549 |
| S5 | 0.02687 | 0.1268 | 0.03584 | 0.2493 | 0.03584 | 0.05281 |
| S6 | 0.5962 | 0.8621 | 0.09562 | 0.8469 | 0.05698 | 0.1258 |
| D1 | 12.58 | 2.359 | 1.352 | 0.2359 | 1.785 | 0.5821 |
| D2 | 13.65 | 1.358 | 0.02359 | 0.1926 | 0.03694 | 0.01582 |
Can find out that through above-mentioned test result can effectively reduce the foreign matter content in the silicon through method disclosed by the invention, especially the content of boron impurities has obtained remarkable reduction.And after combining directional freeze in the method disclosed by the invention, effect is better.
The above is merely preferred embodiment of the present invention, not in order to restriction the present invention, all any modifications of within spirit of the present invention and principle, being done, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.
Claims (13)
1. the method for purification of a silicon comprises raw silicon and melts metal mixed and heating and melting altogether, obtains mixed solution; In mixed solution, feed slag making gas then and add slag former, the slag making refining of blowing; Pulverize again and pickling; The said metal that melts altogether is selected from aluminium, zinc or the titanium one or more.
2. method of purification according to claim 1 is characterized in that, said weight ratio of melting metal and raw silicon altogether is 0.05-5: 1.
3. method of purification according to claim 1 and 2 is characterized in that, the purity of said raw silicon is greater than 98.0%, and the purity of said aluminium is greater than 99.0%.
4. method of purification according to claim 1 is characterized in that, in the said air blowing slag making refining, the slag making gas of feeding contains water vapour and carrier gas; Said carrier gas is selected from a kind of in the gas mixture of gas mixture, rare gas element and oxygen of air, nitrogen, rare gas element, nitrogen and oxygen.
5. method of purification according to claim 4 is characterized in that, said carrier gas is an air, is benchmark with the TV of said air and water vapour, and the volume of said air accounts for 80-99.9%, and the volume of said water vapour accounts for 0.1-20%; Perhaps, said carrier gas is the gas mixture of gas mixture, rare gas element and the oxygen of nitrogen and oxygen, and wherein, nitrogen or rare gas element account for the 60-98% of slag making volume of gas, and oxygen accounts for 5-30%, and water vapour accounts for 1-35%.
6. method of purification according to claim 1 is characterized in that said slag former contains Na
2O, SiO
2And CaF
2Wherein, Na
2The content of O is 10-65wt%, SiO
2Content be 15-85wt%, CaF
2Content be 1-50wt%.
7. according to claim 1 or 6 described methods of purification, it is characterized in that the weight ratio of said slag former and raw silicon is 0.1-10: 1.
8. method of purification according to claim 1 is characterized in that, said pulverization process makes the particle diameter of silicon grain be crushed to 1-1000um.
9. method of purification according to claim 1 is characterized in that said pickling comprises preliminary pickling and white picking; Said preliminary pickling is carried out in first acid solution, and said first acid solution is selected from a kind of in hydrochloric acid, sulfuric acid, the hydrofluoric acid, and said white picking is carried out in second acid solution, and said second acid solution is the mixing acid of a kind of composition in nitric acid and hydrochloric acid, the sulfuric acid.
10. method of purification according to claim 9 is characterized in that, said preliminary pickling is carried out under 45-85 ℃, and Sorensen value is 0.2-8mol/L in first acid solution, and the time of preliminary pickling is 2-24h; Said white picking is carried out under 25-45 ℃, and Sorensen value is 0.2-8mol/L in second acid solution, and the time of white picking is 8-24h.
11. method of purification according to claim 10 is characterized in that, said second acid solution is a chloroazotic acid.
12. method of purification according to claim 1 is characterized in that, after said air blowing slag making refining, the mixed solution after the air blowing slag making is carried out directional freeze; The starting temperature of said directional freeze is 1000-1500 ℃, and speed from bottom to top is 0.05-1.0mm/min.
13. according to claim 1 or 12 described methods of purification, it is characterized in that, in said air blowing slag making refining process, also comprise the slag charge that produces is removed.
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| CN104878226A (en) * | 2015-05-13 | 2015-09-02 | 大连理工大学 | Method for synthesizing massive silicon-titanium intermetallic compound |
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| CN106517212A (en) * | 2016-12-09 | 2017-03-22 | 永平县泰达废渣开发利用有限公司 | Furnace starting process for melting silicon through induction furnace |
| CN106517212B (en) * | 2016-12-09 | 2018-11-02 | 成都斯力康科技股份有限公司 | A kind of furnace technology melting silicon using induction furnace |
| CN106987901A (en) * | 2017-03-30 | 2017-07-28 | 江西赛维Ldk太阳能高科技有限公司 | A kind of crystalline silicon and preparation method thereof |
| CN107324341A (en) * | 2017-05-26 | 2017-11-07 | 昆明理工大学 | The method that a kind of utilization aluminium and oxygen remove boron impurity in industrial silicon |
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