CN102807220B - Silicon purification method - Google Patents
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- CN102807220B CN102807220B CN201110144039.7A CN201110144039A CN102807220B CN 102807220 B CN102807220 B CN 102807220B CN 201110144039 A CN201110144039 A CN 201110144039A CN 102807220 B CN102807220 B CN 102807220B
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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 day by day serious, this has become two hang-ups that various countries' sustained economic development faces.The advantages such as sun power is widely distributed with it, cleanliness without any pollution become the important channel solving 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 chemically obtain, i.e. improved Siemens, 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 producing 1000 tons of polysilicons a general year needs more than 1,000,000,000 Renminbi.If process bad, the recycle of by-product silicon tetrachloride, will cause severe contamination to environment.The cost of the polysilicon prepared with chemical method reach 30-45 dollar/kilogram, for photovoltaic industry scale operation too expensive.So research and develop a kind of low cost and the production technology of the solar-grade polysilicon of environmental protection is very important.Physical metallurgy purifying polycrystalline silicon is then for this development trend provides possibility.
About the purity requirement that solar-grade polysilicon must meet, the impurity level can admitted for industry is at present: phosphorus is at below 0.5ppm, boron is at below 0.3ppm, the metals content impurities such as iron, calcium, aluminium are less than 0.1ppm, solar cell industry generally also requires that conductive wafer type is P type simultaneously, and ratio resistance is 0.5 more than Ω cm.
At present, the technique that physical metallurgy method purifying polycrystalline silicon relates generally to has pickling, slag refining, vacuum induction melting, directional freeze, electron beam and plasma melting etc.
Vacuum induction melting removal of impurities mainly utilizes some impurity element in silicon if the saturated vapor pressures such as P, Al, Ca are much larger than silicon, under certain high vacuum, impurity is volatilized and enters in gas phase, can obtain good impurity-eliminating effect.But in suitability for industrialized production, the design and manufaction of experiment condition to equipment that obtain high temperature high vacuum has very high requirement, and separate unit is long for working cycle, not easily accomplishes scale production.
B and H when plasma technology is the high temperature utilizing plasma gun to produce
2o or H
2generate volatile gases Deng gas reaction thus B is removed, B content can be down to quite low level (lower than 0.1ppm), must remove C and O also quite obvious simultaneously.But because action of plasma scope is little, power consumption is large, process the time that several kilograms of polysilicons just need more than one hour.Suitability for industrialized production equipment is more complicated and wayward, yields poorly, and cost is high.
Pickling, also referred to as hydrometallurgy, reacts mainly through acid and the metallic impurity of silicon face the object making it to enter in liquid and reach removal.But the removal effect of the method to boron impurities is not obvious.
The ultimate principle of directional solidification technique purifying solar energy level polysilicon is the object utilizing the effect of segregation of impurity element in solid phase and liquid phase to reach purification, obtains the columanar structure along direction of growth proper alignment by unidirectional heat current control simultaneously.The directional solidification growth method of polycrystalline silicon used for solar battery ingot conventional at present mainly contains teeming practice, Bridgman method, heat-exchanging method (HEM) and electromagnetic casting method (EMC).
Air blowing slag refining mainly utilize the thermodynamic stability of the oxide compound of some impurity in slag higher and make impurity be enriched in slag mutually in, then by slag gold be separated remove impurity.For boron impurity, because its segregation coefficient (being 0.8) in silicon is bordering on 1, cannot be removed by directional freeze, and its boiling point is high to 2550 DEG C, is also difficult under a high vacuum remove.But the oxide compound of boron is easier to enter in the basic slag of silicon-dioxide, be beneficial to the 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
In order to overcome to after industrial silicon purification in prior art, the problem that boron impurities content is still higher, the invention discloses a kind of method of purification of silicon, and the polysilicon boron impurities content obtained after being purified to industrial silicon by the method is low, reaches solar level requirement.
The method of purification of silicon disclosed by the invention comprises raw silicon and melts metal mixed altogether and heating and melting, obtains mixed solution; Then in mixed solution, pass into slag making gas and add slag former, carrying out air blowing slag refining; Carry out again pulverizing and pickling; Described melt that metal is selected from aluminium, zinc or titanium altogether one or more.
In the present invention, by first raw silicon being melted together the common melting of metal (such as aluminium), and then by air blowing slag practice, and in conjunction with pickling, the boron impurities that can go out to a great extent in raw silicon, improves the purity of silicon greatly, meets the requirement of solar-grade polysilicon.Contriver finds, alloy system (such as Si-Al alloy system) is formed after raw silicon being melted together the common melting of metal (such as aluminium), and the impurity B in raw silicon can melt together metal (such as aluminium) formed more stable, after boron impurities melts metal (such as aluminium) contact together, stable intermediate compound (intermediate compound of such as Al-B) can be formed, thus boron is brought in slag charge, along with the removal of slag charge, the boron impurities in raw silicon is gone out immediately; And the intermediate compound residued in mixed solution is removed by dissolving in follow-up acid cleaning process, thus greatly reduce the content of the boron impurities in silicon.
Further, above-mentioned method of purification is simple for process, is convenient to industrial extensive enforcement.
Embodiment
In order to make technical problem solved by the invention, technical scheme and beneficial effect clearly understand, below in conjunction with embodiment, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, be not intended to limit the present invention.
The method of purification of silicon disclosed by the invention comprises raw silicon and melts metal mixed altogether and heating and melting, obtains mixed solution; Then in mixed solution, pass into slag making gas and add slag former, carrying out air blowing slag refining; Carry out again pulverizing and pickling; Described melt that metal is selected from aluminium, zinc or titanium altogether one or more.
The raw silicon adopted in above-mentioned method of purification is the industrial silicon for the preparation of solar-grade polysilicon well known in the art, as the raw silicon that purity is greater than 98.0%.Above-mentioned raw materials silicon is by being commercially available.The present invention does not limit for the shape of raw silicon, can be silica flour also can be silico briquette.
According to the present invention, the metal that melts altogether adopted in above-mentioned method of purification is preferably aluminium, and wherein, aluminium is aluminium of the prior art, and be preferably rafifinal, its purity is greater than 99.0%.Further optimization silicon purification system, avoids introducing other impurity.
In the present invention, by raw silicon with when melting metal mixed altogether, the two content can change, under preferable case in a big way, described weight ratio of melting metal and raw silicon is altogether 0.05-5: 1, and being more preferably the weight ratio of melting metal and raw silicon is altogether 0.125-0.3: 1.
Heating and melting can be carried out by a certain amount of raw silicon with after melting metal mixed altogether.Carry out in the equipment that above-mentioned heating and melting can be commonly used in this area, such as, induction furnace can be adopted to heat.Under preferable case, first by raw silicon with melt the induction furnace that metal is placed in plumbago crucible altogether, heat under induction furnace power is 60-80KW, obtain the mixed solution of melting.Above-mentioned heating up process is not particularly limited, as long as can melt metal melting by raw silicon with altogether.
Air blowing slag refining can be carried out after obtaining mixed solution.
According to the present invention, the slag making gas passed into during air blowing slag making, at least containing water vapour, contains carrier gas simultaneously; Described carrier gas is selected from the one in the gas mixture of the gas mixture of air, nitrogen, rare gas element, nitrogen and oxygen, rare gas element and oxygen.Wherein, the vector gas effect in slag making gas of the present invention is: dilution water steam, can increase the flow of mixed gas.
Under preferable case, described carrier gas is air, and with the cumulative volume of described air and water vapour for benchmark, the volume of described air accounts for 80-99.9%, and the volume of described water vapour accounts for 0.1-20%.Similar, described 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%.More 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 is above-mentioned various gas, boron is changed into the oxide compound of boron and the oxyhydroxide (BOH) of boron by oxygen (or the oxygen in air) wherein and water
n.Wherein, the oxyhydroxide of boron is gaseous state, can overflow, reach the object of removal of impurities with air.In addition, when containing oxygen in carrier gas, part in mixed solution can be melted altogether metal (such as aluminium) oxidation, simultaneously silicon melts metal (such as aluminium) when forming alloy (such as Si-Al alloy) together, melt metal (such as aluminium) altogether and can form more stable intermediate compound (such as Al-B) with boron, and be oxidized the oxide compound (such as aluminum oxide) that obtains can be combined melting metal (such as aluminium) altogether with slag former, thus boron impurities is brought in slag charge, by follow-up separation, effectively boron impurities can be gone out, thus reduce the content of boron impurities further.
Above-mentioned rare gas element is well known in the art, is 0 race's gas, is more preferably argon gas in the present invention.
Under preferable case, the present invention adopts porous swivel nozzle to pass into mixed gas in silicon liquid.
Before passing into slag making gas, preferably porous swivel nozzle is carried out preheating on mixed solution surface, warm up time is preferably at 4-6min.Then be inserted in mixed solution by preheated porous swivel nozzle, preferred porous swivel nozzle is inserted into the place of distance container bottom 15-25mm.
After ventilation starts, the rotating speed of porous swivel nozzle is preferably 200-500rad/min.
The flow passing into mixed gas is preferably 300-500l/h, more preferably 350-450l/h.
Continue to pass into slag making gas in fusion process, the aeration time of slag making gas is preferably 50-80min, more preferably 60-70min.
While passing into gas, in mixed solution, add slag former.
According to the present invention, above-mentioned slag former can adopt the slag former of various system of the prior art, such as CaO-SiO
2, Na
2o-SiO
2, CaO-SiO
2-CaF
2, CaO-MgO-SiO
2, CaO-BaO-SiO
2deng.
In the present invention, described slag former is preferably Na
2o-SiO
2-CaF
2system, that is, described slag former contains Na
2o, SiO
2and CaF
2.Concrete, in described slag former, Na
2the content of O is 10-65wt%, SiO
2content be 15-85wt%, CaF
2content be 1-50wt%; Be more preferably Na
2the content of O is 15-55wt%, SiO
2content be 25-65wt%, CaF
2content be 3-20wt%.
In the present invention, when adopting the slag former of above-mentioned system, boron is changed into the oxide compound of boron and the oxyhydroxide (BOH) of boron by the oxygen G&W in the slag making gas passed in mixed solution
nafter, the oxide compound of the boron of formation can highly stable being present in above-mentioned slag former system.As previously mentioned, the oxyhydroxide of boron overflows with the form of gas; Further, metal (such as aluminium) oxidation of melting altogether in mixed solution is formed after oxide compound, can better be compatible with slag charge, thus can more effective removing boron impurities.
In addition, CaF
2the viscosity of slag charge can be reduced thus the mobility of increase slag, and CaF
2the fusing point of slag can be reduced; The main slag that this slag charge is formed is Na mutually
2siO
3, by slag making, have quite a few foreign matter of phosphor (P) can incorporate slag mutually in, thus reach the effect simultaneously removing boron impurities and phosphorus.
According to the present invention, the addition of described slag former can change in a big way, and under preferable case, the weight ratio of described slag former and raw silicon is 0.1-10: 1, is more preferably 0.5-3: 1.
Under preferable case, in order to improve the separation degree of impurity further, reduce the content of impurity, in described air blowing slag refining process, the slag charge removing that can will produce, namely while air blowing slag making, removes slag charge.The method of above-mentioned removing slag charge does not limit, such as, can directly be pulled out by the slag charge floating on mixed solution surface.
As to further improvement of the present invention, under preferable case, after above-mentioned air blowing slag making process, directional freeze can also be carried out to the mixed solution after air blowing slag making.In early stage, silicon is melted metal (such as aluminium) together to melt altogether, and through specific slag former (Na
2o-SiO
2-CaF
2) after air blowing slag making process, by directional freeze, while the impurity such as removing P, Al, Ca, boron impurities can be removed further, improve the purity of silicon.
Under preferable case, the starting temperature of described directional freeze is 1000-1500 DEG C.Travelling speed is from bottom to top 0.05-1.0mm/min.
After above-mentioned air blowing slag making process or directional freeze process, to the product cooling obtained, and can pulverize, under preferable case, described pulverization process makes the particle diameter of silicon grain be crushed to 1-1000um, obtains silicon grain.
According to the present invention, the silicon grain to obtaining after pulverizing is also needed to carry out pickling.By carrying out pickling to the above-mentioned silicon grain prepared, in conjunction with the air blowing slag refining in early stage, the content of impurity greatly can be reduced.
Above-mentioned pickling can be pickling well known in the art, and under preferable case, described pickling comprises preliminary pickling and white picking; Described preliminary pickling is carried out in the first acid solution, concrete, above-mentioned silicon grain can be soaked in the first acid solution.Described first acid solution is selected from the one in hydrochloric acid, sulfuric acid, hydrofluoric acid.
For above-mentioned preliminary pickling, can carry out at 45-85 DEG C.Wherein, in the first acid solution, hydrogen ion concentration can change in a big way, is preferably 0.2-8mol/L.The time of preliminary pickling also can change in a big way, and under preferable case, the time of preliminary pickling is 2-24h.
Described white picking is carried out in the second acid solution, same, the silicon grain after preliminary pickling can be soaked in the second acid solution, and described second acid solution is the mixing acid of a kind of composition in nitric acid and hydrochloric acid, sulfuric acid.
For above-mentioned white picking, can carry out at 25-45 DEG C.Wherein, under preferable case, in described second acid solution, hydrogen ion concentration is 0.2-8mol/L.The time of white picking is 8-24h.Above-mentioned second acid solution is mixing acid, and under preferable case, described second acid solution is chloroazotic acid, namely contains nitric acid and hydrochloric acid in described second acid solution.
When adopting aforesaid method to carry out pickling, intermediate compound (the such as AlB that can will residue in mixed solution
2and AlB
12) effectively and fully remove, thus greatly reduce the foreign matter content in silicon grain, improve the purity of silicon.
Under further preferable case, after above-mentioned preliminary pickling and white picking, adopt washed with de-ionized water to neutral respectively, and dry.
Below by embodiment, the present invention is further detailed.
The raw silicon adopted in the embodiment of the present invention and comparative example is same source, wherein, measured wherein by inductive coupling plasma emission spectrograph (ICP-AES) that foreign matter content situation is as follows, B:66.355ppm, P:49.405ppm, Fe:1708ppm, Al:682.2ppm, Ti:282.95ppm, Ca:60.39ppm.
Embodiment 1
The present embodiment is for illustration of the method for purification of silicon disclosed by the invention.
Put in induction furnace by 100 raw material silicon and 50 weight part zinc (purity is 99.5%) mixing, heating and melting, obtains mixed solution.
Then will be connected with the porous swivel nozzle of slag making gas (90 parts by volume nitrogen+10 parts by volume water vapour), be down to silicon liquid preheating 5min on the surface.Then be inserted in mixed solution by under porous swivel nozzle, insert under 15mm place at the bottom of high-purity silica pot stops.Pass into slag making gas, control gas flow is 400l/h, and the rotating speed of porous swivel nozzle is 400rad/min.Simultaneously by the 66.7 weight part slag former (Na of 20wt%
2the SiO of O, 40wt%
2, the CaF of 6.7wt%
2) be brought in above-mentioned mixed solution, carry out air blowing slag making process.
By the mixed solution cooling after air blowing slag making process, ingot casting peeling, pulverize, obtain the silicon grain that particle diameter is 55um-268um.
By above-mentioned silicon grain pickling 5h in the hydrochloric acid soln (concentration is 3.1mol/l) of 52 DEG C, then in the deionized water of 45 DEG C, clean 3h.Again by water washed silicon grain pickling 12h in second acid solution (hydrogen ion concentration is 4.3mol/l, chloroazotic acid) of 31 DEG C, and then by washed with de-ionized water to neutral, dry.Obtain product silicon S1.
Embodiment 2
The present embodiment is for illustration of the method for purification of silicon disclosed by the invention.
Put in induction furnace by 100 raw material silicon and 8 weight part aluminium (purity is 99.5%) mixing, heating and melting, obtains mixed solution.
Then will be connected with the porous swivel nozzle of slag making gas (92 parts by volume air+8 parts by volume water vapour), be down to silicon liquid preheating 5min on the surface.Then be inserted in mixed solution by under porous swivel nozzle, insert under 15mm place at the bottom of high-purity silica pot stops.Pass into slag making gas, control gas flow is 400l/h, and the rotating speed of porous swivel nozzle is 400rad/min.Simultaneously by the 83.3 weight part slag former (Na of 31.2wt%
2the SiO of O, 45wt%
2, the CaF of 7.1wt%
2) join in above-mentioned mixed solution, carry out air blowing slag making process.
By the mixed solution cooling after air blowing slag making process, ingot casting peeling, pulverize, obtain the silicon grain that particle diameter is 49um-254um.
Above-mentioned silicon grain is soaked 5h in the hydrochloric acid soln (concentration is 4mol/l) of 60 DEG C, then in the deionized water of 45 DEG C, cleans 3h.Again water washed silicon grain is soaked 12h in second acid solution (hydrogen ion concentration is 5.4mol/l, chloroazotic acid) of 31 DEG C, and then by washed with de-ionized water to neutral, dry.Obtain product silicon S2.
Embodiment 3
The present embodiment is for illustration of the method for purification of silicon disclosed by the invention.
Put in induction furnace by 100 raw material silicon and 15.8 weight part aluminium (purity is 99.5%) mixing, heating and melting, obtains mixed solution.
Then will 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), be down to silicon liquid preheating 5min on the surface.Then be inserted in mixed solution by under porous swivel nozzle, insert under 15mm place at the bottom of high-purity silica pot stops.Pass into slag making gas, control gas flow is 400l/h, and the rotating speed of porous swivel nozzle is 400rad/min.Simultaneously by the 67.6 weight part slag former (Na of 30wt%
2the SiO of O, 32.3wt%
2, the CaF of 5.3wt%
2) join in above-mentioned mixed solution, carry out air blowing slag making process.
Silicon after air blowing slag making process is carried out directional freeze, and the starting temperature of described directional freeze is 1302 DEG C, and travelling speed is from bottom to top 0.15mm/min
Then by the silicon ingot peeling after directional freeze, pulverizing, the silicon grain that particle diameter is 106-598um is obtained.
Above-mentioned silicon grain is soaked 5h in the hydrochloric acid soln (concentration is 3.1mol/l) of 52 DEG C, then in the deionized water of 45 DEG C, cleans 3h.Again water washed silicon grain is soaked 12h in second acid solution (hydrogen ion concentration is 6mol/l, chloroazotic acid) of 30.6 DEG C, and then by washed with de-ionized water to neutral, dry.Obtain product silicon S3.
Embodiment 4
The present embodiment is for illustration of the method for purification of silicon disclosed by the invention.
Put in induction furnace by 100 raw material silicon and 17 weight part aluminium (purity is 99.5%) mixing, heating and melting, obtains mixed solution.
Then will 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), be down to silicon liquid preheating 5min on the surface.Then be inserted in mixed solution by under porous swivel nozzle, insert under 15mm place at the bottom of high-purity silica pot stops.Pass into slag making gas, control gas flow is 400l/h, and the rotating speed of porous swivel nozzle is 400rad/min.Simultaneously by the 73 weight part slag former (Na of 28wt%
2the SiO of O, 40wt%
2, the CaF of 5wt%
2) join in above-mentioned mixed solution, carry out air blowing slag making process.
Silicon after air blowing slag making process is carried out directional freeze, and the starting temperature of described directional freeze is 1130 DEG C, and travelling speed is from bottom to top 0.65mm/min
Then by the silicon ingot peeling after directional freeze, pulverizing, the silicon grain that particle diameter is 502-952um is obtained.
Above-mentioned silicon grain is soaked 9h in the hydrochloric acid soln (concentration is 6mol/l) of 59 DEG C, then in the deionized water of 45 DEG C, cleans 3h.Again water washed silicon grain is soaked 12h in second acid solution (hydrogen ion concentration is 5.2mol/l, chloroazotic acid) of 34 DEG C, and then by washed with de-ionized water to neutral, dry.Obtain product silicon S4.
Embodiment 5
The present embodiment is for illustration of the method for purification of silicon disclosed by the invention.
Adopt the Methods For Purification silicon identical with embodiment 4, unlike in acid cleaning process, in air blowing slagging process, repeatedly pull the slag charge of formation out.
Obtain product silicon S5.
Embodiment 6
The present embodiment is for illustration of the method for purification of silicon disclosed by the invention.
Adopt the Methods For Purification silicon identical with embodiment 4, unlike in acid cleaning process, only silicon grain is carried out pickling in hydrochloric acid soln, in the second acid solution, do not carry out pickling.
Obtain product silicon S6.
Comparative example 1
This comparative example is used for the method for purification of comparative illustration silicon disclosed by the invention.
Adopt the Methods For Purification silicon identical with embodiment 2, do not add aluminium unlike in heating and melting process, only by raw silicon melting.
Obtain product silicon D1.
Comparative example 2
This comparative example is used for the method for purification of comparative illustration silicon disclosed by the invention.
Adopt the Methods For Purification silicon identical with embodiment 6, do not add aluminium unlike in heating and melting process, only by raw silicon melting.
Obtain product silicon D2.
Performance test
Product silicon S1-S6, D1, D2 nitric acid that above-mentioned purification is obtained and hydrofluoric acid dissolution, in inductive coupling plasma emission spectrograph (ICP-AES), under thousand grades of purification conditions, test the content of the boron impurities in above-mentioned each product silicon, phosphorus, iron, aluminium, calcium, titanium.
The test result obtained inserts 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 be found out by above-mentioned test result, can be effectively reduced the foreign matter content in silicon by method disclosed by the invention, especially the content of boron impurities obtains remarkable reduction.Further, after in method disclosed by the invention in conjunction with directional freeze, effect is better.
The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.
Claims (8)
1. a method of purification for silicon, comprises raw silicon and melts metal mixed altogether and heating and melting, obtaining mixed solution; Then in mixed solution, pass into slag making gas and add slag former, carrying out air blowing slag refining; Carry out again pulverizing and pickling; Described melt that metal is selected from aluminium, zinc or titanium altogether one or more;
In described air blowing slag refining, the slag making gas passed into contains water vapour and carrier gas;
Described carrier gas is air, and with the cumulative volume of described air and water vapour for benchmark, the volume of described air accounts for 80-99.9%, and the volume of described water vapour accounts for 0.1-20%; Or described carrier gas is the gas mixture of the gas mixture of nitrogen and oxygen, 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%; Described weight ratio of melting metal and raw silicon is altogether 0.05-5:1;
Described slag former contains Na
2o, SiO
2and CaF
2; Wherein, Na
2the content of O is 10-65wt%, SiO
2content be 15-85wt%, CaF
2content be 1-50wt%.
2. method of purification according to claim 1, is characterized in that, the purity of described raw silicon is greater than 98.0%, and the purity of described aluminium is greater than 99.0%.
3. method of purification according to claim 1, is characterized in that, the weight ratio of described slag former and raw silicon is 0.1-10:1.
4. method of purification according to claim 1, is characterized in that, described pulverization process makes the particle diameter of silicon grain be crushed to 1-1000 μm.
5. method of purification according to claim 1, is characterized in that, described pickling comprises preliminary pickling and white picking; Described preliminary pickling is carried out in the first acid solution, and described first acid solution is selected from the one in hydrochloric acid, sulfuric acid, hydrofluoric acid, and described white picking is carried out in the second acid solution, and described second acid solution is the mixing acid of a kind of composition in nitric acid and hydrochloric acid, sulfuric acid.
6. method of purification according to claim 5, is characterized in that, described preliminary pickling is carried out at 45-85 DEG C, and in the first acid solution, hydrogen ion concentration is 0.2-8mol/L, and the time of preliminary pickling is 2-24h; Described white picking is carried out at 25-45 DEG C, and in the second acid solution, hydrogen ion concentration is 0.2-8mol/L, and the time of white picking is 8-24h.
7. method of purification according to claim 6, is characterized in that, described second acid solution is chloroazotic acid.
8. method of purification according to claim 1, is characterized in that, after described air blowing slag refining, carries out directional freeze to the mixed solution after air blowing slag making; The starting temperature of described directional freeze is 1000-1500 DEG C, and speed is from bottom to top 0.05-1.0mm/min.
9.method of purification according to claim 1 or 8, is characterized in that, in described air blowing slag refining process, also comprises the slag charge removing that will produce.
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| CN103011170A (en) * | 2012-12-31 | 2013-04-03 | 大连理工大学 | Method for purifying polysilicon through silicon alloy slagging |
| CN103318894B (en) * | 2013-06-27 | 2016-03-02 | 大连理工大学 | Remove the method for boron in polysilicon |
| CN104773736A (en) * | 2015-03-31 | 2015-07-15 | 杭州太能硅业有限公司 | Method for removing boron impurities in metal silicon |
| CN104817088A (en) * | 2015-05-04 | 2015-08-05 | 日鑫（永安）硅材料有限公司 | Method of low-cost preparing solar-grade polycrystalline silicon |
| CN104878226B (en) * | 2015-05-13 | 2017-02-22 | 大连理工大学 | Method for synthesizing massive silicon-titanium intermetallic compound |
| 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 |
| CN107324341B (en) * | 2017-05-26 | 2020-04-07 | 昆明理工大学 | Method for removing impurity boron in industrial silicon by using aluminum and oxygen |
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| CN102040219A (en) * | 2009-10-14 | 2011-05-04 | 贵阳宝源阳光硅业有限公司 | Method for preparing high-purity silicon by purifying industrial silicon |
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