CN102432021B - Method for preparing polysilicon - Google Patents
Method for preparing polysilicon Download PDFInfo
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- CN102432021B CN102432021B CN 201110276760 CN201110276760A CN102432021B CN 102432021 B CN102432021 B CN 102432021B CN 201110276760 CN201110276760 CN 201110276760 CN 201110276760 A CN201110276760 A CN 201110276760A CN 102432021 B CN102432021 B CN 102432021B
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Abstract
The invention relates to a method for preparing polysilicon, which belongs to the field of metallurgy. The method comprises: 1) a raw material silicon is fused into a liquid state silicon in the air atmosphere, under one atmospheric pressure; 2) a slagging agent is added into the fused liquid state silicon and refined, and a slag is filtered; 3) the liquid state silicon prepared by the step 2) is directionally cooled for obtaining silicon ingots. The method can remove phosphor and boron from the silicon, thus the silicon can reach the standard of the solar energy level polysilicon. Compared to the prior art, the method of the present invention has the advantages of minimized technology step, simplified operation and reduced cost.
Description
Technical field
The present invention relates to a kind of method for preparing polysilicon, particularly prepare the method for solar-grade polysilicon with metallurgy method.
Background technology
Along with improving constantly of global energy consumption, conventional non-regeneration energy can not satisfy the demand of most countries.According to the analysis of world energy sources authoritative institution, to calculate according to fossil energy reserves and the recovery rate verified at present, the Global Oil residual content can be exploited the time limit only 40 years, and the Sweet natural gas residual content can be adopted and is only 60 years, and the coal residual content can be adopted the time limit only 120 years.On the other hand, the exploitation of the disposable energy and application also are major reasons that causes ecological damage and global environmental pollution.Therefore, the exploitation of renewable new forms of energy and use are related to permanent development human and society.
New forms of energy photovoltaic generation industry, as renewable and clean energy resource, because of its have safe and reliable, noiseless, pollution-free, restriction less, the not available advantage of other conventional energy resourcess such as failure rate is low, easy maintenance, resource be wide, being recognized is important new forms of energy of 21 century, be widely used in generate electricity by way of merging two or more grid systems, the aspects such as civilian power generation, communal facility and integrated energy-saving building, the crystalline silicon photovoltaic power generation system occupies the main status in new forms of energy photovoltaic generation market at present.Along with application and the silicon chip processing technology of polycrystalline silicon purifying technology are further ripe, the raising of photoelectric transformation efficiency and the development of other Technologies comprise that the renewable energy source of new forms of energy photovoltaic generation might be finished fully from replenishing the energy to the role transforming of conventional energy resources.
The High Purity Polycrystalline silicon materials are basic products of photovoltaic generation industry, the progress of its production technology be the photovoltaic generation industry can promotion and application the important step of development.How to reduce the cost, environmental contamination reduction, reduction production energy consumption of solar energy polycrystalline silicon, the reliability that improves production safety is the important topic of theCourse of PV Industry.
Impurity in the metallurgical grade silicon almost contains all elements in the periodic table of elements, can be divided into two classes: a class is metallic impurity elements, take Fe, Al, three kinds of elements of Ca as representative; Another kind of is non-metallic element, take phosphorus and two kinds of elements of boron as representative.Its electrical performance indexes of solar-grade polysilicon has strict demand to the control of these foreign matter contents.Particularly very strict to the content requirement of phosphorus and boron, usually require the content of boron less than 0.4ppm, the content of phosphorus is less than 0.7ppm.Two kinds of elements of boron and phosphorus in the purification process are because the singularity of its chemical property becomes Physical purification techniques global problem.
The method of various countries' production polysilicon mainly contains chemical method and metallurgy method in the world at present.Chemical method take the improvement Siemens Method as main.Chemical method changes the chemical state of silicon in technological process, after purifying through a series of chemical reaction, restore into silicon.For example the Siemens Method of improvement mainly utilizes metallurgical grade silicon and anhydrous chlorides of rase H-H reaction to generate trichlorosilane (SiHCl
3), obtaining high-purity trichlorosilane by rectifying again, the trichlorosilane after will purifying at last is reduced into high purity polycrystalline silicon in reduction furnace.Its advantage is that the purity of polysilicon product is high, can reach the requirement of electronic-grade, its shortcoming be energy consumption large, have and pollute and have a large amount of reluctant silicon tetrachloride (SiCl
4) the by product generation.Along with raising and the global financial crisis impact of the whole world on environment protection, the market requirement is the solar-grade polysilicon of low price more.In the case, the requirement of the method for, eco-friendly purifying polycrystalline silicon low to cost is day by day urgent, and metallurgy method purifying polycrystalline silicon advantage has in this respect embodied out gradually.
Metallurgy method is mainly the physical purification technology, also claims Physical.Physical keeps the chemical state of silicon constant in technological process, changes by series of physical silicon is purified.Its advantage is, technical process is short, pollutions is little, energy consumption is lower, and its shortcoming is that extent of purification is lower, and the boron in the silicon and phosphorus impurities can not be reduced to the requirement of solar-grade polysilicon simultaneously, even need to carry out separately dephosphorization or remove the step of boron.
Summary of the invention
For problems of the prior art, the present invention proposes a kind of method for preparing polysilicon, it adopts metallurgy method, can be simultaneously with the requirement to solar-grade polysilicon of the content of boron and phosphorus, and do not need extra dephosphorization or except the boron step.Method technique of the present invention is simple, energy consumption is low, non-pollutant discharge, easy and simple to handle.
The method according to this invention, it may further comprise the steps:
1) at air atmosphere, under 1 normal atmosphere, raw silicon is melt into liquid-state silicon;
2) slag former is joined in the liquid-state silicon of melting in batches refining and elimination slag body;
3) will be by step 2) liquid-state silicon after purifying carries out orientation and cools off, and obtains silicon ingot.
According to the present invention, at air atmosphere, under 1 normal atmosphere, raw silicon is put into the refining furnace heating and melting, form liquid-state silicon.The add-on of raw silicon can be decided according to the refining furnace capacity.In one embodiment, in selected raw silicon, the content of boron is less than or equal to 100ppm, and the content of phosphorus is less than or equal to 30ppm.
According to the present invention, in liquid-state silicon, add slag former, the boron in the silicon, phosphorus impurities are changed the slagging body and in step subsequently, discharge.In one embodiment, described slag former is alkaline slag former.Preferably, described alkaline slag former is by the CaO of 30%-40% weight, the Na of 10%-30% weight
2CO
3SiO with 40%-50% weight
2Form, more preferably, described alkaline slag former comprises the CaO of 36% weight, the Na of 18% weight
2CO
3SiO with 46% weight
2
In another embodiment, the temperature of liquid-state silicon is remained on 1435 ℃-1500 ℃, preferably its temperature is remained on 1455 ℃.Under this reaction conditions, utilize alkaline slag former to the strong adsorption effect of the boron in the silicon, phosphorus impurities, make boron, phosphorus impurities and alkaline slag former form the slag body.If temperature is higher, the gasification of alkaline slag former loss is excessive, and the adsorption effect of boron, phosphorus impurities is relatively poor, and also larger to the container infringement, easily cause container material to the antipollution of product, and also can shorten accordingly the work-ing life of container.If temperature is excessively low, alkaline slag former does not reach impurity-eliminating effect to the adsorption activity meeting variation of boron, phosphorus impurities.
In one embodiment, the silicon of described alkaline slag former total amount and institute's melting is designated as 1 with weight ratio: 1-1: 5, be preferably 1: 1.25.In a preferred embodiment, divide 30-120 equivalent to add described alkaline slag former, the timed interval is 10 minutes.This batch gradation adds, and is conducive to the abundant use of slag former, also is conducive to the removal of boron in the silicon, phosphorus impurities.
According to the present invention, to filtering with the liquid-state silicon of slag body, except removing slag body.Then liquid-state silicon is transferred in the cast container, carried out the orientation cooling, to guarantee that silicon can become the desired column crystal of solar panel by oriented growth.In one embodiment, described cast container filters with energy liquid towards silicon before silicon being transferred to the cast container also with millipore filter, thereby guarantees the purity of silicon.In one embodiment, the rate of temperature fall of directed cooling is 60 ℃/hour.
According to the present invention, prepared silicon is carried out purity check.In one embodiment, in prepared silicon, the content of boron is less than 0.4ppm, and the content of phosphorus has reached the requirement of solar-grade polysilicon less than 0.6ppm.
The invention has the advantages that, the alkaline slag former of the application of the invention, can be simultaneously with the requirement to solar-grade polysilicon of the content of boron and phosphorus, and do not need extra dephosphorization or except the boron step.Compared with prior art, present method has reduced processing step, and operation is simplified greatly, has also reduced cost simultaneously.Treatment temp is also lower, and the loss that has reduced energy consumption, alkaline slag former is few, and impurity-eliminating effect is also better.
Embodiment
The below will be described further a kind of method for preparing solar-grade polysilicon of the present invention by specific embodiment.
Embodiment 1:
With boracic 10ppm, the raw silicon 200Kg of phosphorous 10ppm is put in the refining furnace, at air atmosphere, under 1 normal atmosphere, is electrically heated to silicon and becomes molten state.Keep the liquid-state silicon temperature at 1455 ℃, with 200 kilograms the CaO that contains 72Kg, the Na of 36Kg
2CO
3SiO with 92Kg
2Alkaline slag former divide and put in the liquid-state silicon for 40 times, carry out refining.Each add-on is 5Kg, every minor tick 10 minutes.After refining is finished, with the slag body elimination in the liquid-state silicon, then liquid-state silicon is transferred in the pouring container by the millipore filter of cast container, at last under rate of temperature fall is 60 ℃/hour condition, liquid-state silicon is carried out orientation cool off and obtain silicon ingot.After cooled silicon ingot carried out powder process and clean, carry out purity check, analytical results is boron content 0.35ppm; Phosphorus content 0.6ppm reaches the requirement of solar energy level silicon.
Embodiment 2:
With boracic 100ppm, the raw silicon 100Kg of phosphorous 30ppm is put in the refining furnace, at air atmosphere, under 1 normal atmosphere, is electrically heated to silicon and becomes molten state.Keep the liquid-state silicon temperature at 1455 ℃, with 125 kilograms the CaO that contains 45Kg, the Na of 22.5Kg
2CO
3SiO with 57.5Kg
2Alkaline slag former divide and put in the liquid-state silicon for 100 times, carry out refining.Each add-on is 1.25Kg, every minor tick 10 minutes.After refining is finished, with the slag body elimination in the liquid-state silicon, then liquid-state silicon is transferred in the pouring container by the millipore filter of cast container, at last under rate of temperature fall is 60 ℃/hour condition, liquid-state silicon is carried out orientation cool off and obtain silicon ingot.After cooled silicon ingot carried out powder process and clean, carry out purity check, analytical results is boron content 0.3ppm; Phosphorus content 0.5ppm reaches the requirement of solar energy level silicon.
Can see by above embodiment and Comparative Examples, boron, the phosphorus impurities content of the method according to this invention in can the decrease raw silicon, being that 100ppm is reduced to 0.3ppm with boron from content for example, is that 30ppm is reduced to 0.5ppm with phosphorus from content, has reached the requirement of solar-grade polysilicon.
Although invention has been described with reference to preferred embodiment, without departing from the present invention, can carry out various improvement and can replace wherein material with equivalent it.The present invention is not limited to disclosed specific embodiment in the literary composition, but comprises all technical schemes that fall in the claim scope.
Claims (8)
1. method for preparing polysilicon, it may further comprise the steps:
1) at air atmosphere, under 1 normal atmosphere, raw silicon is melt into liquid-state silicon;
2) alkaline slag former is joined in the liquid-state silicon of melting in batches refining and elimination slag body;
3) will be by step 2) liquid-state silicon of preparation carries out orientation and cools off, and obtains silicon ingot.
Wherein, described alkaline slag former is by the CaO of 30%-40% weight, the Na of 10%-30% weight
2CO
3SiO with 40%-50% weight
2Form.
2. method according to claim 1 is characterized in that, described alkaline slag former comprises the CaO of 36% weight, the Na of 18% weight
2CO
3SiO with 46% weight
2
3. method according to claim 1 and 2 is characterized in that, the temperature of described liquid-state silicon remains on 1435 ℃-1500 ℃.
4. method according to claim 3 is characterized in that, the temperature of described liquid-state silicon remains 1455 ℃.
5. method according to claim 1 and 2 is characterized in that, the silicon of described alkaline slag former total amount and institute's melting is designated as 1 with weight ratio: 1-1: 5, be preferably 1: 1.25.
6. method according to claim 1 and 2 is characterized in that, in step 3) in the rate of temperature fall of directed cooling be 60 ℃/hour.
7. method according to claim 1 and 2 is characterized in that, divides 30-120 equivalent to add described alkaline slag former, and the timed interval is 10 minutes.
8. method according to claim 1 is characterized in that, in selected raw silicon, the content of boron is less than or equal to 100ppm, and the content of phosphorus is less than or equal to 30ppm.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201110276760 CN102432021B (en) | 2011-09-16 | 2011-09-16 | Method for preparing polysilicon |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201110276760 CN102432021B (en) | 2011-09-16 | 2011-09-16 | Method for preparing polysilicon |
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| CN102432021A CN102432021A (en) | 2012-05-02 |
| CN102432021B true CN102432021B (en) | 2013-02-20 |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1143605A (en) * | 1995-08-22 | 1997-02-26 | 李忠莆 | Producing technique for refined silicon |
| CN101905885A (en) * | 2009-06-05 | 2010-12-08 | 贵阳宝源阳光硅业有限公司 | Low-boron molten slag for purifying silicon and preparation method thereof |
| CN101955186A (en) * | 2010-09-19 | 2011-01-26 | 江西盛丰新能源科技有限公司 | Method for preparing polycrystalline silicon by physically removing boron |
| CN102001661A (en) * | 2010-11-22 | 2011-04-06 | 东海晶澳太阳能科技有限公司 | Method for slagging, boron removal and purification of metalluragical silicon |
| CN102134076A (en) * | 2011-01-25 | 2011-07-27 | 云南乾元光能产业有限公司 | Method for removing boron impurity in metallurgical silicon |
-
2011
- 2011-09-16 CN CN 201110276760 patent/CN102432021B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1143605A (en) * | 1995-08-22 | 1997-02-26 | 李忠莆 | Producing technique for refined silicon |
| CN101905885A (en) * | 2009-06-05 | 2010-12-08 | 贵阳宝源阳光硅业有限公司 | Low-boron molten slag for purifying silicon and preparation method thereof |
| CN101955186A (en) * | 2010-09-19 | 2011-01-26 | 江西盛丰新能源科技有限公司 | Method for preparing polycrystalline silicon by physically removing boron |
| CN102001661A (en) * | 2010-11-22 | 2011-04-06 | 东海晶澳太阳能科技有限公司 | Method for slagging, boron removal and purification of metalluragical silicon |
| CN102134076A (en) * | 2011-01-25 | 2011-07-27 | 云南乾元光能产业有限公司 | Method for removing boron impurity in metallurgical silicon |
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