CN1935648A - Method for preparing polycrystalline silicon for solarcell from rice husk - Google Patents
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Abstract
The invention discloses a method for preparing polycrystalline silicon for solar batteries by rice hulls, comprising: preprocessing, i.e. etching in 5-25%high-purity oxidizing acidic water solution at 80-300 deg.C for 30-200 min, washing with water, drying and crushing, and then adding in additive by 1-10 mass shares and extrude-molding at 60-300 deg.C; thermochemical modifying, i.e. controlling temperature by program in a certain atmosphere to prepare proper silicon-carbon composite; melting in high temperature electric cooker, arc furnace, microwave oven or high temperature solar furnace and obtaining melted silicon, directionally solidifying and preparing the polycrystalline silicon. And the produced polycrystalline silicon has a up to 99.9999% purity, able to replace the polycrystalline silicon produced by Siemens process and it has advantages of simple process, low cost and wide raw material sources.
Description
Technical field
The present invention relates to the preparation method of polycrystalline silicon used for solar battery, be specifically related to prepare the method for polycrystalline silicon used for solar battery with rice husk.
Background technology
At present, produce polycrystalline silicon used for solar battery in the world and adopt trichlorosilane reduction method, i.e. Siemens Method substantially.This method complex process, apparatus expensive, cost height.Even so, China does not also grasp the core technology of this method, and the polysilicon in extractive process more than 70% has all discharged by chlorine, not only further strengthened production cost, and environmental pollution is very serious.Therefore, how cheapness prepares polycrystalline silicon used for solar battery in large quantity becomes the key of applying solar cell.Chinese invention patent ZL02135841.9 discloses a kind of cheap method of producing high-purity silicon for solar energy cell, this method needs earlier Pure Silicon Metal to be smelted into silicon melt, in this silicon melt, add lime, ferric oxide, fluorite, be blown into oxygen, chlorine, aqueous hydrogen and argon gas, finally make silicon melt order directional freeze in crystallizer prepare high purity silicon.But the silicon materials purity of producing with this method only is 99.90～99.999%, can only be applicable to the solar cell that class is lower.Chinese patent ZL 95197920.5 has announced a kind of method of making polycrystalline silicon used for solar battery, and earlier with rough silicon and the refining of Calucium Silicate powder melting mixing, molten refined in inert gas atmosphere then is after the vacuum-treat molten silicon evaporates dephosphorization.This method technology is also lower than the simple cost of Siemens Method, but this technology will just can obtain the polysilicon of 6N purity, the production cost height again through molten refined repeatedly after the vacuum-evaporation dephosphorization.Chinese patent ZL 98109237.3 has introduced a kind of method of making silicon for solar cell, this method is to make with extra care by following operation: will solidify the thick refining procedure that becomes Pure Silicon Metal after the silicon-dioxide reduction with carbon, the vacuum dephosphorization of this Pure Silicon Metal of molten refined takes off the boron operation and solidifies refining step.The polysilicon purity that this method is produced is no more than 6N, and technology is complicated, thereby has limited its application.
In a word, there are problems such as energy consumption height, complex process, cost height in existing polycrystalline silicon used for solar battery production method, can't satisfy that market presses for can be in enormous quantities, the low cost production polycrystalline silicon used for solar battery.
Summary of the invention
The objective of the invention is to overcome the shortcoming of prior art, the preparation method of the polycrystalline silicon used for solar battery that a kind of technology is simple, cost is low, raw material sources are wide is provided, method of the present invention is with the rice processed side product---and rice husk is a raw material, by preparing polycrystalline silicon used for solar battery cheaply after physics and the chemical modification.
The present invention realizes by following technology:
A kind ofly prepare the method for polycrystalline silicon used for solar battery, may further comprise the steps with rice husk:
(1) pre-treatment: it is in 5～25% the acid aqueous solution of oxidisability that the rice husk of 100 mass parts is added 800 mass parts concentration, etching is 30～200 minutes under 80～300 ℃ of temperature condition, pulverize behind the washing and drying, add the additive of 1～10 mass parts then, 60～300 ℃ of following extrusion moldings;
(2) thermochemistry modification: with step (1) gained extrusion molding product in argon gas, nitrogen, oxygen, air or vacuum, and under 500～1000 ℃ of temperature condition, pyrolysis 30～300 minutes, preparation silicon and carbon mol ratio are 1/1.8～1/2.2 matrix material;
(3) thermal reduction: in process furnace, melting obtains molten silicon under 1800～2000 ℃ the temperature with step (2) gained matrix material, and directional freeze prepares polycrystalline silicon used for solar battery then.
The acid solution of the oxidisability of described step (1) is one or more and the hydrogen peroxide in sulfuric acid, hydrochloric acid, nitric acid, the perchloric acid, one or both composite the forming in the dioxide peroxide.
The additive of described step (1) is one or more the mixture in polyacrylic acid, starch, polyvinyl alcohol, sucrose, dextrin, polyoxyethylene, the ether of cellulose.
The extrusion molding product that step (2) is used is one or more of sheet structure, columnar structure, tubular structure.
Described process furnace is electric furnace, electric arc furnace, microwave oven or high temperature solar furnace.
Described directional freeze is that the high purity graphite electrode is adopted in arc melting, and the furnace bottom of electric arc furnace, the mouth that slips are built by laying bricks or stones with high purity graphite, and the silicon melt of producing directly carries out directional freeze from bottom to top in high-purity crystallized device.
Described directional freeze is when adopting electric furnace, microwave oven or the melting of high temperature solar furnace, uses the high purity graphite crucible, and the silicon melt of producing carries out directional freeze from bottom to top in high-purity crystallized device.
The present invention is the feedstock production polycrystalline silicon used for solar battery with the rice husk.Rice husk is the maximum by-product in the rice processing, accounts for 20% of paddy gross weight.As shown in table 1, rice husk rich cellulose, xylogen, polysaccharide, inorganic ash content, fat, Protein content is very low.Therefore, as shown in table 2, contain metal oxides such as a large amount of silicon-dioxide and a spot of potassium, calcium, iron, magnesium in the ashes after the rice husk burning.As shown in table 3, can be reduced to extremely low-level by the element beyond silicon-dioxide in the pre-treatment rice husk and the carbon.Therefore, rice husk is the excellent raw material of production HIGH-PURITY SILICON.
The chemical constitution information slip of table 1 rice husk
| Mierocrystalline cellulose | Polysaccharide | Xylogen | Inorganic component | Other |
| 32 | 21 | 24 | 20 | 3 |
Inorganic component information slip in table 2 rice husk
| SiO 2 | K 2O | CaO | Fe 2O 3 | MgO | Al 2O 3 | Other |
| 96.3 | 1.49 | 0.97 | 0.54 | 0.36 | 0.21 | 0.13 |
Inorganic component information slip after table 3 pre-treatment in the rice husk
| SiO 2 | K 2O | CaO | Fe 2O 3 | MgO | Al 2O 3 | Other |
| 99.999 | -- | 0.0003 | 0.0001 | 0.0002 | 0.0002 | 0.0002 |
By pyrolysis purifying rice husk, after adjusting silicon/carbon mol ratio and being about 1/2, carry out silicon melt that carbothermic reduction obtains again through in high-purity crystallized device, carrying out directional freeze from bottom to top.Because the impurities removal effect of directional freeze, impurity is finally stayed the upper surface place of silicon crystal, removes top impurity enriched part and just can obtain required used for solar batteries high-purity polycrystalline silicon.
Have following advantage with respect to prior art the present invention:
Can production purity reach 99.9999% polysilicon by method of the present invention, alternative siemens method is produced polycrystalline silicon used for solar battery, and method of the present invention has the advantage that technology is simple, cost is low, raw material sources are wide.
Embodiment
The present invention is further illustrated below in conjunction with example and accompanying drawing, but embodiments of the present invention are not limited thereto.
Embodiment 1
Prepare the method for polycrystalline silicon used for solar battery with rice husk, may further comprise the steps:
(1) pre-treatment; The rice husk of 500 grams is added in the 4000 gram aqueous solution that contain 20% hydrochloric acid and 5% hydrogen peroxide, under 200 ℃ of temperature condition, etching is 30 minutes in autoclave (polytetrafluoroethyllining lining), pulverize behind the washing and drying, the sucrose that add 25 grams then are in 180 ℃ of following extrusion moldings sheet structure that is the high 5mm of diameter 10mm/.
(2) thermochemistry modification; In air, under 800 ℃ of temperature condition, 1: 2 matrix material is prepared silicon and carbon mol ratio and is in pyrolysis 120 minutes with step (1) gained sheet structure.
(3) thermal reduction; In high-temperature electric resistance furnace, melting obtains molten silicon under 1900 ℃ of temperature with step (2) gained matrix material, directional freeze from bottom to top in high-purity crystallized device then, and excision top impurity enriched partly obtains polycrystalline silicon used for solar battery.Through adopting inductivity coupled plasma mass spectrometry ICP-MS technical testing, its purity reaches 5N, and the content situation of impurity element is as shown in table 4.
Embodiment 2
Prepare the method for polycrystalline silicon used for solar battery with rice husk, may further comprise the steps:
(1) pre-treatment; The rice husk of 500 grams is added in the 4000 gram aqueous solution that contain 5% hydrochloric acid and 5% hydrogen peroxide, under 200 ℃ of temperature condition, etching is 30 minutes in autoclave (polytetrafluoroethyllining lining), pulverize behind the washing and drying, add 5 gram polyoxyethylenes then, in 60 ℃ of following extrusion moldings sheet structure that is the high 5mm of diameter 10mm/.
(2) thermochemistry modification; In argon gas, under 1000 ℃ of temperature condition, 1: 1.8 matrix material is prepared silicon and carbon mol ratio and is in pyrolysis 100 minutes with step (1) gained sheet structure.
(3) thermal reduction; In high-temperature electric resistance furnace, melting obtains molten silicon under 1900 ℃ of temperature with step (2) gained matrix material, directional freeze from bottom to top in high-purity crystallized device then, and excision top impurity enriched partly obtains polycrystalline silicon used for solar battery.Through adopting inductivity coupled plasma mass spectrometry ICP-MS technical testing, its purity reaches 4N, and the content situation of impurity element is as shown in table 4.
Embodiment 3
Prepare the method for polycrystalline silicon used for solar battery with rice husk, may further comprise the steps:
(1) pre-treatment; The rice husk of 500 grams is added in the 4000 gram aqueous solution that contain 20% hydrochloric acid and 5% hydrogen peroxide, under 80 ℃ of temperature condition, etching is 30 minutes in autoclave (polytetrafluoroethyllining lining), pulverize behind the washing and drying, add 5 gram polyvinyl alcohol then, in 180 ℃ of following extrusion moldings sheet structure that is the high 10mm of diameter 20mm/.
(2) thermochemistry modification; In air, under 1000 ℃ of temperature condition, 1: 2.2 matrix material is prepared silicon and carbon mol ratio and is in pyrolysis 30 minutes with step (1) gained sheet structure.
(3) thermal reduction; In high-temperature electric resistance furnace, melting obtains molten silicon under 1900 ℃ of temperature with step (2) gained matrix material, directional freeze from bottom to top in high-purity crystallized device then, and excision top impurity enriched partly obtains polycrystalline silicon used for solar battery.Through adopting inductivity coupled plasma mass spectrometry ICP-MS technical testing, its purity reaches 3N, and the content situation of impurity element is as shown in table 4.
Embodiment 4
(1) pre-treatment; The rice husk of 500 grams is added in the 4000 gram aqueous solution that contain 20% hydrochloric acid and 5% hydrogen peroxide, under 300 ℃ of temperature condition, etching is 30 minutes in autoclave (polytetrafluoroethyllining lining), pulverize behind the washing and drying, add the ether of cellulose of 15 grams then, in 180 ℃ of following extrusion moldings sheet structure that is the high 3mm of diameter 5mm/, and internal diameter is 3mm, external diameter is 10mm, and height is the tubular structure of 10mm, and both mix according to mass ratio at 3: 1.
(2) thermochemistry modification; In air, under 1000 ℃ of temperature condition, 1: 2.1 matrix material is prepared silicon and carbon mol ratio and is in pyrolysis 30 minutes with step (1) gained sheet structure.
(3) thermal reduction; In high-temperature electric resistance furnace, melting obtains molten silicon under 1900 ℃ of temperature with step (2) gained matrix material, directional freeze from bottom to top in high-purity crystallized device then, and excision top impurity enriched partly obtains polycrystalline silicon used for solar battery.Through adopting inductivity coupled plasma mass spectrometry ICP-MS technical testing, its purity reaches 6N, and the content situation of impurity element is as shown in table 4.
Embodiment 5
(1) pre-treatment; The rice husk of 500 grams is added in the 4000 gram aqueous solution that contain 10% hydrochloric acid, 10% sulfuric acid and 5% hydrogen peroxide, under 200 ℃ of temperature condition, etching is 30 minutes in autoclave (polytetrafluoroethyllining lining), pulverize behind the washing and drying, add 15 gram dextrin and 10 gram sucrose then, in 180 ℃ of following extrusion moldings sheet structure that is the high 10mm of diameter 20mm/.And internal diameter is 15mm, and external diameter is 50mm, and height is the tubular structure of 50mm, and both are mixed according to mass ratio 4: 1.
(2) thermochemistry modification; Under oxygen atmosphere, under 500 ℃ of temperature condition, 1: 2 matrix material is prepared silicon and carbon mol ratio and is in pyrolysis 300 minutes with step (1) gained sheet structure.
(3) thermal reduction; In high-temperature electric resistance furnace, melting obtains molten silicon under 1900 ℃ of temperature with step (2) gained matrix material, directional freeze from bottom to top in high-purity crystallized device then, and excision top impurity enriched partly obtains polycrystalline silicon used for solar battery.Through adopting inductivity coupled plasma mass spectrometry ICP-MS technical testing, its purity reaches 5N, and the content situation of impurity element is as shown in table 4.
Embodiment 6
(1) pre-treatment; The rice husk of 500 grams is added in the 4000 gram aqueous solution that contain 10% hydrochloric acid, 10% nitric acid and 5% hydrogen peroxide, under 300 ℃ of temperature condition, etching is 60 minutes in autoclave (polytetrafluoroethyllining lining), pulverize behind the washing and drying, add 20 gram sucrose and 5 gram polyvinyl alcohol then, in 300 ℃ of following extrusion moldings sheet structure that is the high 5mm of diameter 10mm/.
(2) thermochemistry modification; Under vacuum condition, under 800 ℃ of temperature condition, 1: 1.9 matrix material is prepared silicon and carbon mol ratio and is in pyrolysis 120 minutes with step (1) gained sheet structure.
(3) thermal reduction; In high-temperature electric resistance furnace, melting obtains molten silicon under 1900 ℃ of temperature with step (2) gained matrix material, directional freeze from bottom to top in high-purity crystallized device then, and excision top impurity enriched partly obtains polycrystalline silicon used for solar battery.Through adopting inductivity coupled plasma mass spectrometry ICP-MS technical testing, its purity reaches 6N, and the content situation of impurity element is as shown in table 4.
Embodiment 7
(1) pre-treatment; The rice husk of 500 grams is added in the 4000 gram aqueous solution that contain 10% hydrochloric acid, 5% perchloric acid, 5% nitric acid and 5% hydrogen peroxide, under 200 ℃ of temperature condition, etching is 60 minutes in autoclave (polytetrafluoroethyllining lining), pulverize behind the washing and drying, add 25 gram starch then, at 200 ℃ of following extrusion moldings columnar structure that is the high 50mm of diameter 10mm/.
(2) thermochemistry modification; In nitrogen, under 800 ℃ of temperature condition, 1: 2 matrix material is prepared silicon and carbon mol ratio and is in pyrolysis 300 minutes with step (1) gained sheet structure.
(3) thermal reduction; In high-temperature electric resistance furnace, melting obtains molten silicon under 1900 ℃ of temperature with step (2) gained matrix material, directional freeze from bottom to top in high-purity crystallized device then, and excision top impurity enriched partly obtains polycrystalline silicon used for solar battery.Through adopting inductivity coupled plasma mass spectrometry ICP-MS technical testing, its purity reaches 6N, and the content situation of impurity element is as shown in table 4.
Embodiment 8
(1) pre-treatment; The rice husk of 500 grams is added in the 4000 gram aqueous solution that contain 10% hydrochloric acid, 5% sulfuric acid, 5% nitric acid and 5% dioxide peroxide, under 200 ℃ of temperature condition, etching is 60 minutes in autoclave (polytetrafluoroethyllining lining), pulverize behind the washing and drying, add 25 gram sucrose then, at 180 ℃ of following extrusion moldings columnar structure that is the high 5mm of diameter 5mm/.
(2) thermochemistry modification; In air, under 800 ℃ of temperature condition, 1: 2 matrix material is prepared silicon and carbon mol ratio and is in pyrolysis 120 minutes with step (1) gained sheet structure;
(3) thermal reduction; In high-temperature electric resistance furnace, melting obtains molten silicon under 1900 ℃ of temperature with step (2) gained matrix material, directional freeze from bottom to top in high-purity crystallized device then, and excision top impurity enriched partly obtains polycrystalline silicon used for solar battery.Through adopting inductivity coupled plasma mass spectrometry ICP-MS technical testing, its purity reaches 6N, and the content situation of impurity element is as shown in table 4.
Embodiment 9
(1) pre-treatment; The rice husk of 500 grams is added in the 4000 gram aqueous solution that contain 10% hydrochloric acid, 5% sulfuric acid, 5% nitric acid and 5% dioxide peroxide, under 200 ℃ of temperature condition, etching is 60 minutes in autoclave (polytetrafluoroethyllining lining), pulverize behind the washing and drying, add 5 gram polyacrylic acid then, at 300 ℃ of following extrusion moldings columnar structure that is the high 50mm of diameter 50mm/.
(2) thermochemistry modification; In air, under 800 ℃ of temperature condition, 1: 2 matrix material is prepared silicon and carbon mol ratio and is in pyrolysis 120 minutes with step (1) gained sheet structure;
(3) thermal reduction; In high-temperature electric resistance furnace, melting obtains molten silicon under 1800 ℃ of temperature with step (2) gained matrix material, directional freeze from bottom to top in high-purity crystallized device then, and excision top impurity enriched partly obtains polycrystalline silicon used for solar battery.Through adopting inductivity coupled plasma mass spectrometry ICP-MS technical testing, its purity reaches 6N, and the content situation of impurity element is as shown in table 4.
Embodiment 10
(1) pre-treatment; The rice husk of 500 grams is added in the 4000 gram aqueous solution that contain 10% hydrochloric acid, 5% perchloric acid, 5% nitric acid and 5% hydrogen peroxide, under 200 ℃ of temperature condition, etching is 60 minutes in autoclave (polytetrafluoroethyllining lining), pulverize behind the washing and drying, the sucrose that add 25 grams then are at 180 ℃ of following extrusion moldings columnar structure that is the high 30mm of diameter 10mm/.
(2) thermochemistry modification; In air, under 800 ℃ of temperature condition, 1: 2 matrix material is prepared silicon and carbon mol ratio and is in pyrolysis 120 minutes with step (1) gained sheet structure;
(3) thermal reduction; In high-temperature electric resistance furnace, melting obtains molten silicon under 2000 ℃ of temperature with step (2) gained matrix material, directional freeze from bottom to top in high-purity crystallized device then, and excision top impurity enriched partly obtains polycrystalline silicon used for solar battery.Through adopting inductivity coupled plasma mass spectrometry ICP-MS technical testing, its purity reaches 6N, and the content situation of impurity element is as shown in table 4.
Embodiment 11
(1) pre-treatment; The rice husk of 500 grams is added in the 4000 gram aqueous solution that contain 10% hydrochloric acid, 5% sulfuric acid, 5% nitric acid and 5% hydrogen peroxide, under 200 ℃ of temperature condition, etching is 60 minutes in autoclave (polytetrafluoroethyllining lining), pulverize behind the washing and drying, add 50 gram sucrose then, in 180 ℃ of following extrusion moldings sheet structure that is the high 30mm of diameter 50mm/, and internal diameter is 10mm, external diameter is 80mm, and height is the tubular structure of 80mm, and both mix according to mass ratio at 1: 1.
(2) thermochemistry modification; In air, under 800 ℃ of temperature condition, 1: 2.1 matrix material is prepared silicon and carbon mol ratio and is in pyrolysis 120 minutes with step (1) gained sheet structure;
(3) thermal reduction; Step (2) gained matrix material (is adopted the high purity graphite electrode in arc melting, the furnace bottom of electric arc furnace, the mouth that slips are built by laying bricks or stones with high purity graphite), the molten silicon that melting obtains directional freeze from bottom to top in high-purity crystallized device, excision top impurity enriched partly obtains polycrystalline silicon used for solar battery.Through adopting inductivity coupled plasma mass spectrometry ICP-MS technical testing, its purity reaches 4N, and the content situation of impurity element is as shown in table 4.
Embodiment 12
(1) pre-treatment; The rice husk of 500 grams is added in the 4000 gram aqueous solution that contain 10% hydrochloric acid, 5% sulfuric acid, 5% nitric acid and 5% hydrogen peroxide, under 200 ℃ of temperature condition, etching is 60 minutes in autoclave (polytetrafluoroethyllining lining), pulverize behind the washing and drying, add 20 gram sucrose and 30 gram starch then, at 180 ℃ of following extrusion moldings columnar structure that is the high 50mm of diameter 30mm/, and internal diameter is 20mm, external diameter is 80mm, and height is the tubular structure of 80mm, and both mix according to mass ratio at 2: 1.
(2) thermochemistry modification; In air, under 800 ℃ of temperature condition, 1: 2 matrix material is prepared silicon and carbon mol ratio and is in pyrolysis 120 minutes with step (1) gained sheet structure;
(3) thermal reduction; Step (2) gained matrix material (is adopted the high purity graphite electrode in arc melting, the furnace bottom of electric arc furnace, the mouth that slips are built by laying bricks or stones with high purity graphite), the molten silicon that melting obtains directional freeze from bottom to top in high-purity crystallized device, excision top impurity enriched partly obtains polycrystalline silicon used for solar battery.Through adopting inductivity coupled plasma mass spectrometry ICP-MS technical testing, its purity reaches 4N, and the content situation of impurity element is as shown in table 4.
Embodiment 13
(1) pre-treatment; The rice husk of 500 grams is added in the 4000 gram aqueous solution that contain 10% hydrochloric acid, 5% sulfuric acid, 5% nitric acid and 5% hydrogen peroxide, under 200 ℃ of temperature condition, etching is 60 minutes in autoclave (polytetrafluoroethyllining lining), pulverizes behind the washing and drying, add 50 gram sucrose then, 180 ℃ of following extrusion moldings is that internal diameter is 30mm, and external diameter is 100mm, and height is the tubular structure of 100mm, and internal diameter is 20mm, external diameter is 100mm, and height is the tubular structure of 100mm, and both mix according to mass ratio at 3: 1.
(2) thermochemistry modification; In air, under 800 ℃ of temperature condition, 1: 2 matrix material is prepared silicon and carbon mol ratio and is in pyrolysis 120 minutes with step (1) gained sheet structure;
(3) thermal reduction; Step (2) gained matrix material (is adopted the high purity graphite electrode in arc melting, the furnace bottom of electric arc furnace, the mouth that slips are built by laying bricks or stones with high purity graphite), the molten silicon that melting obtains directional freeze from bottom to top in high-purity crystallized device, excision top impurity enriched partly obtains polycrystalline silicon used for solar battery.Through adopting inductivity coupled plasma mass spectrometry ICP-MS technical testing, its purity reaches 4N, and the content situation of impurity element is as shown in table 4.
Embodiment 14
(1) pre-treatment; The rice husk of 500 grams is added in the 4000 gram aqueous solution that contain 10% hydrochloric acid, 5% sulfuric acid, 5% nitric acid and 5% hydrogen peroxide, under 200 ℃ of temperature condition, etching is 100 minutes in autoclave (polytetrafluoroethyllining lining), pulverize behind the washing and drying, add 25 gram sucrose and 20 gram dextrin then, in 140 ℃ of following extrusion moldings sheet structure that is the high 5mm of diameter 10mm/, and internal diameter is 5mm, external diameter is 50mm, and height is the tubular structure of 50mm, and both mix according to mass ratio at 2: 1.
(2) thermochemistry modification; In air, under 800 ℃ of temperature condition, 1: 2 matrix material is prepared silicon and carbon mol ratio and is in pyrolysis 120 minutes with step (1) gained sheet structure;
(3) thermal reduction; With the melting in microwave oven of step (2) gained matrix material, directional freeze from bottom to top in high-purity crystallized device then, excision top impurity enriched partly obtains polycrystalline silicon used for solar battery.Through adopting inductivity coupled plasma mass spectrometry ICP-MS technical testing, its purity reaches 6N, and the content situation of impurity element is as shown in table 4.
Embodiment 15
(1) pre-treatment; The rice husk of 500 grams is added in the 4000 gram aqueous solution that contain 10% hydrochloric acid, 5% sulfuric acid, 5% nitric acid and 5% hydrogen peroxide, under 200 ℃ of temperature condition, etching is 200 minutes in autoclave (polytetrafluoroethyllining lining), pulverize behind the washing and drying, add 10 gram sucrose then and restrain polyoxyethylenes, in 180 ℃ of following extrusion moldings sheet structure that is the high 5mm of diameter 10mm/ with 5, and internal diameter is 5mm, external diameter is 50mm, and height is the tubular structure of 50mm, and both mix according to mass ratio at 2: 1.
(2) thermochemistry modification; In air, under 800 ℃ of temperature condition, 1: 2 matrix material is prepared silicon and carbon mol ratio and is in pyrolysis 120 minutes with step (1) gained sheet structure;
(3) thermal reduction; In the melting of high temperature solar furnace, melting obtains molten silicon under 1900 ℃ of temperature with step (2) gained matrix material, directional freeze from bottom to top in high-purity crystallized device then, and excision top impurity enriched partly obtains polycrystalline silicon used for solar battery.Through adopting inductivity coupled plasma mass spectrometry ICP-MS technical testing, its purity reaches 6N, and the content situation of impurity element is as shown in table 4.
China produces about 4,000 ten thousand tons of rice husk per year, occupy first place in the world, but rice husk is used as refuse and handles as a rule, promptly wastes resource contaminate environment again.Rice husk contains preparation silicon required two kinds of raw materials: silicon-dioxide and carbon, and wherein silicone content is about 10%, and it is promptly annual that we can obtain nearly 4,000,000 tons silicon from rice husk.At present world industry silicon output is about 1,200,000 tons, about 4000 tons in China in 2005 to the demand of high-purity polycrystalline silicon raw material, and wherein 95% with upper inlet.The invention provides the method for preparing polycrystalline silicon used for solar battery with rice husk, not only solved the pollution problem of rice husk, and satisfy the silicon market requirement, have huge commerce, environment and social benefit.
The composition of table 4 embodiment 1-15 gained silicon
| Impurity content (ppm) | |||||||||
| Aluminium | Magnesium | Iron | Calcium | Potassium | Boron | Phosphorus | Other | Purity (%) | |
| Embodiment 1 embodiment 2 embodiment 3 embodiment 4 embodiment 5 embodiment 6 embodiment 7 embodiment 8 embodiment 9 embodiment 10 embodiment 11 embodiment 12 embodiment 13 embodiment 14 embodiment 15 | ＜1 3 18 ＜1 ＜1 ＜1 ＜1 ＜1 ＜1 ＜1 9 7 13 ＜1 ＜1 | ＜1 2 8 ＜1 ＜1 ＜1 ＜1 ＜1 ＜1 ＜1 5 8 3 ＜1 ＜1 | ＜1 6 14 ＜1 ＜1 ＜1 ＜1 ＜1 ＜1 ＜1 13 21 7 ＜1 ＜1 | ＜1 7 54 ＜1 ＜1 ＜1 ＜1 ＜1 ＜1 ＜1 25 17 17 ＜1 ＜1 | ＜1 12 57 ＜1 ＜1 ＜1 ＜1 ＜1 ＜1 ＜1 9 17 12 ＜1 ＜1 | ＜1 2 2 ＜1 ＜1 ＜1 ＜1 ＜1 ＜1 ＜1 4 3 4 ＜1 ＜1 | 2 14 23 ＜1 3 ＜1 ＜1 ＜1 ＜1 ＜1 17 11 23 ＜1 ＜1 | 2 15 20 <1 2 ＜1 ＜1 ＜1 ＜1 ＜1 8 7 17 ＜1 ＜1 | 99.9993 99.994 99.98 99.9999 99.9991 99.9999 99.9999 99.9999 99.9999 99.9999 99.991 99.993 99.99 99.9999 99.9999 |
Claims (8)
1, a kind ofly prepare the method for polycrystalline silicon used for solar battery, it is characterized in that may further comprise the steps with rice husk:
(1) pre-treatment: it is in 5～25% the acid aqueous solution of oxidisability that the rice husk of 100 mass parts is added 800 mass parts concentration, etching is 30～200 minutes under 80～300 ℃ of temperature condition, pulverize behind the washing and drying, add the additive of 1～10 mass parts then, 60～300 ℃ of following extrusion moldings;
(2) thermochemistry modification: with step (1) gained extrusion molding product in argon gas, nitrogen, oxygen, air or vacuum, and under 500～1000 ℃ of temperature condition, pyrolysis 30～300 minutes, preparation silicon and carbon mol ratio are 1/1.8～1/2.2 matrix material;
(3) thermal reduction: in process furnace, melting obtains molten silicon under 1800～2000 ℃ the temperature with step (2) gained matrix material, and directional freeze prepares polycrystalline silicon used for solar battery then.
2, according to claim 1ly prepare the method for polycrystalline silicon used for solar battery with rice husk, the acid solution of oxidisability that it is characterized in that described step (1) is selected from one or more and the hydrogen peroxide in sulfuric acid, hydrochloric acid, nitric acid, the perchloric acid, one or both composite the forming in the dioxide peroxide.
3, according to claim 1ly prepare the method for polycrystalline silicon used for solar battery with rice husk, the additive that it is characterized in that described step (1) is one or more the mixture in polyacrylic acid, starch, polyvinyl alcohol, sucrose, dextrin, polyoxyethylene, the ether of cellulose.
4, the method for preparing polycrystalline silicon used for solar battery with rice husk according to claim 1, the extrusion molding that it is characterized in that described step (1) is 5～50mm for being squeezed into diameter, height is the sheet structure of 3～30mm, perhaps diameter is 5～50mm, height is the columnar structure of 5～50mm, or internal diameter is 3～30mm, and external diameter is 10～100mm, and height is the tubular structure of 10～100mm.
5, according to claim 1ly prepare the method for polycrystalline silicon used for solar battery, it is characterized in that extrusion molding product that step (2) uses is one or more of sheet structure, columnar structure, tubular structure with rice husk.
6, according to claim 1ly prepare the method for polycrystalline silicon used for solar battery, it is characterized in that described process furnace is electric furnace, electric arc furnace, microwave oven or high temperature solar furnace with rice husk.
7, the method for preparing polycrystalline silicon used for solar battery with rice husk according to claim 1, it is characterized in that described directional freeze is when adopting arc melting, use the high purity graphite electrode, the furnace bottom of electric arc furnace, the mouth that slips are built by laying bricks or stones with high purity graphite, and the silicon melt of producing carries out directional freeze from bottom to top in high-purity crystallized device.
8, according to claim 1 or the 6 described methods that prepare polycrystalline silicon used for solar battery with rice husk, it is characterized in that described directional freeze is when adopting electric furnace, microwave oven or the melting of high temperature solar furnace, use the high purity graphite crucible, the silicon melt of producing carries out directional freeze from bottom to top in high-purity crystallized device.
Priority Applications (1)
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| EP2203248A1 (en) * | 2007-10-17 | 2010-07-07 | Jan-Philipp Mai | Method and device for producing silicon |
| CN101673781B (en) * | 2009-09-25 | 2010-11-03 | 邵振亚 | Method for preparing solar cell polysilicon raw material from rice hulls |
| CN102066250A (en) * | 2008-06-16 | 2011-05-18 | N.E.D.硅股份公司 | Method for preparing high-purity metallurgical-grade silicon |
| CN102110740A (en) * | 2010-11-23 | 2011-06-29 | 上海交通大学 | Twice-heat treatment method of directionally solidified polycrystalline silicon solar cell |
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| RU2161124C1 (en) * | 1999-09-16 | 2000-12-27 | Виноградов Виктор Владимирович | Method of preparing rice husk for high-pure silicon dioxide producing |
| CN1116128C (en) * | 2001-05-25 | 2003-07-30 | 吉林大学 | Comprehensive rice husk utilizing method |
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| CN102066250A (en) * | 2008-06-16 | 2011-05-18 | N.E.D.硅股份公司 | Method for preparing high-purity metallurgical-grade silicon |
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| CN103710023A (en) * | 2013-12-04 | 2014-04-09 | 华南理工大学 | Method for preparing porous photoluminescence material by utilization of rice husks |
| CN113252751A (en) * | 2021-05-14 | 2021-08-13 | 杭州电子科技大学 | Detection method for silicon content of rice |
| CN113252751B (en) * | 2021-05-14 | 2022-06-10 | 杭州电子科技大学 | Detection method for silicon content of rice |
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