WO2012000428A1 - Method for preparing high purity silicon - Google Patents

Method for preparing high purity silicon Download PDF

Info

Publication number
WO2012000428A1
WO2012000428A1 PCT/CN2011/076517 CN2011076517W WO2012000428A1 WO 2012000428 A1 WO2012000428 A1 WO 2012000428A1 CN 2011076517 W CN2011076517 W CN 2011076517W WO 2012000428 A1 WO2012000428 A1 WO 2012000428A1
Authority
WO
WIPO (PCT)
Prior art keywords
silicon
powder
mixture
raw
purity
Prior art date
Application number
PCT/CN2011/076517
Other languages
French (fr)
Inventor
Shaobo Peng
Lei SI
Yishun Shen
Zhineng Wu
Original Assignee
Byd Company Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to CN201010218843 priority Critical
Priority to CN201010218843.0 priority
Application filed by Byd Company Limited filed Critical Byd Company Limited
Publication of WO2012000428A1 publication Critical patent/WO2012000428A1/en

Links

Classifications

    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00Silicon; Compounds thereof
    • C01B33/02Silicon
    • C01B33/021Preparation
    • C01B33/023Preparation by reduction of silica or free silica-containing material
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00Silicon; Compounds thereof
    • C01B33/02Silicon
    • C01B33/037Purification
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01PINDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00Physical properties of inorganic compounds
    • C01P2006/80Compositional purity

Abstract

A method for preparing a high purity silicon comprises steps of: providing a raw material mixture containing a quartz sand, an aluminum powder and a fluorite powder; heating the raw material mixture to a temperature of about 1100℃ to about 1700℃ to melt the raw material mixture allowing a thermite reaction to obtain a liquid silicon and a slag; and separating and cooling the liquid silicon to obtain a silicon product, the impurity content of which is less than 1wt%.

Description

METHOD FOR PREPARING HIGH PURITY SILICON
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the priority to and benefits of Chinese Application No. 201010218843.0, filed on June 29, 2010, the content of which is incorporated by reference herein in its entirety.
FIELD
The present disclosure relates to a method for purifying silicon, more particularly to a method for preparing high purity silicon.
BACKGROUND
At present, the high purity silicon is generally prepared through a complicated carbothermal reduction method. Charcoal is often used as a carbon reducing agent, so that a plenty of biomass resources such as trees may be wasted. Besides, the silicon obtained through the carbothermal reduction method may contain an impurity such as B and P with a higher content. Furthermore, the carbothermal reduction method may also need a huge of electric energy to provide the heat energy (for example, the average electric energy for preparing one ton of silicon may be about 12000KWh), which may lead to a great cost.
SUMMARY
One object of the present disclosure is to solve at least one of the above problems.
Embodiments of the present disclosure provide a method for preparing a high purity silicon, comprising steps of: providing a raw material mixture containing a quartz sand, an aluminum powder and a fluorite powder; heating the raw material mixture to a temperature of about 1100°C to about 1700°C to melt the raw material mixture allowing a thermite reaction to obtain a liquid silicon and a slag; and separating and cooling the liquid silicon to obtain a silicon product, the impurity content of which is less than lwt%.
The method for preparing the high purity silicon according to an embodiment of the present disclosure may have at least one of the following advantages. 1) According to an embodiment of the present disclosure, aluminum, instead of carbon, is used as the reducing agent so that the biomass resource may not be wasted.
2) According to an embodiment of the present disclosure, the high purity silicon obtained has a high purity and a huge output, and the content of the impurities, especially B and P, may be lower than before.
3) According to an embodiment of the present disclosure, toxic and harmful gases or solids may not be generated, and the by-product slag may be used as the raw material for producing building materials or cements.
4) Compared with the conventional carbothermal reduction method, the thermite reduction method according to an embodiment of the present disclosure may have less energy consumption.
5) The step of removing the impurity such as B and P is omitted, so that the method according to an embodiment of the present disclosure may be short in technological process and simple in operation.
Additional aspects and advantages of the embodiments of the present disclosure will be given in part in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments of the present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other aspects and advantages of the disclosure will become apparent and more readily appreciated from the following descriptions taken in conjunction with the drawings in which:
Fig. 1 is a flow chart for preparing a high purity silicon according to an embodiment of the present disclosure; and
Fig. 2 is a flow chart for preparing a high purity silicon according to another embodiment of the present disclosure.
DETAILED DESCRIPTION
Reference will be made in detail to embodiments of the present disclosure. The embodiments described herein with reference to the accompanying drawings are explanatory and illustrative, which are used to generally understand the present disclosure. The embodiments shall not be construed to limit the present disclosure. As used herein, the term "high purity silicon" means a silicon product with lower impurity content. The high purity silicon prepared according to an embodiment of the present disclosure may have a purity of at least 99%, and this high purity silicon may also be called as a metallurgical grade silicon. Furthermore, according to another embodiment of the present disclosure, the high purity silicon obtained may have a purity of at least about 99.99% and could be used to prepare the solar battery, and this high purity silicon may also be called as a solar grade silicon. Unless indicated otherwise, the term "%" as used here means percentage by weight.
One object of the present disclosure is to provide a method for preparing a high purity silicon. As shown in Fig. 1, according to an embodiment of the present disclosure, the method for preparing the high purity silicon comprises the steps of: providing a raw material mixture containing quartz sand and an aluminum powder; heating the raw material mixture to a temperature of about 1100°C to 1700°C to melt the raw material mixture allowing an thermite reaction to obtain a liquid silicon and a slag; and separating the liquid silicon from the slag and cooling the liquid silicon to obtain a silicon product, the impurity content of which may be less than lwt%, which indicates that the purity of the high purity silicon is at least about 99%>.
The quartz sand used as a silicon source is known to those skilled in the art, the major component of which is silicon dioxide. According to a specific embodiment of the present disclosure, the quartz sand with a silicon dioxide content of at least about 99wt% may be used as the silicon source. According to an embodiment of the present disclosure, an aluminum powder is used as a reducing agent for preparing the high purity silicon, which will react with silicon dioxide to produce silicon. According to a specific embodiment of the present disclosure, the aluminum powder with a purity of at least about 98wt% may be used. According to an embodiment of the present disclosure, the raw material mixture may further contain calcium oxide and a fluorite powder. Accordingly, the quartz sand, the aluminum powder, the calcium oxide and the fluorite powder which is mainly composed of CaF2 may achieve the fluxing effect and accelerate the melting each other, so that the melting temperature may be decreased so as to further save energy. According to an embodiment of the present disclosure, quick lime may be used as a source of calcium oxide. According to an embodiment of the present disclosure, preferably, the purity of calcium oxide and the fluorite powder may be more than 95wt%.
According to an embodiment of the present disclosure, the particle size of each component in the raw material mixture, such as the quartz sand, the aluminum powder, the calcium oxide and the fluorite powder, may be less than about 1mm. Therefore, each component in the raw material mixture may be mixed with each other sufficiently to increase the effective contact area between the components, so that the reaction may be completely conducted and the reaction rate may be increased.
According to an embodiment of the present disclosure, in the raw material mixture, the weight ratio of the quartz sand to the aluminum powder is about 2: 1 to about 10:7, so that the quartz sand and the aluminum powder may react fully to produce silicon with a high yield. According to an embodiment of the present disclosure, in the raw material mixture, the weight ratio of the quartz sand to the calcium oxide powder may be about 5:2 to about 1 : 1, so that the thermite reaction may be carried out easily because the initial temperature of the thermite reaction may be decreased. Moreover, the calcium oxide powder may sufficiently absorb the reaction product aluminum oxide to promote the reaction. Furthermore, according to an embodiment of the present disclosure, based on the total weight of the raw material mixture, the fluorite powder may be present in an amount of about 5wt% to about 17wt%. Therefore, the viscosity of the melt obtained by the thermite reaction may be moderate so as to facilitate the aggregation of the liquid silicon, and the produced liquid silicon may be separated from the slag easily so as to increase the purity of the obtained silicon.
According to an embodiment of the present disclosure, there are no special limits on the equipment for melting the raw material mixture. According to an embodiment of the present disclosure, the melting of the raw material mixture may be conducted in an induction furnace. Particularly, the quartz sand and the aluminum powder may be mixed to obtain a raw material mixture, which is then added into the induction furnace. After the raw material mixture is melted at a temperature of about 1100°C to about 1700°C , the thermite reaction is started, that is, the reactions shown by the following chemical equations occur:
3Si02+4Al=3 Si+2Al203+Q main reaction
zSi02+xAl203+yCaO→xAl203-yCaO-zSi02 slagging reaction.
According to an embodiment of the present disclosure, the heating process may be as follows: the raw material mixture may be heated to a temperature of about 1000°C to about 1 100°C at a heating rate of about 20°C/min to about 30°C/min, and then the heating rate may be adjusted to about 10°C/min to about 20°C/min and the raw material mixture may be heated until the raw material mixture is melted completely. Then, the thermite reaction may be conducted at a temperature of about 1 100°C to 1700 °C for about 30min to 120min. According to an embodiment of the present disclosure, the reaction may be conducted at a temperature of about 1400°C to 1600°C for about 35min to about 60min. After the reaction is finished, the liquid silicon may be poured out and cooled to obtain a silicon product. With the method for preparing the high purity silicon according to an embodiment of the present disclosure, the thermite reaction between the aluminum powder and the quartz sand may be conducted in the liquid state to obtain a liquid silicon and aluminum oxide. The thermite reaction is an exothermic reaction so that a plenty of heat may be released. Accordingly, after the thermite reaction is started, external heat may not be needed, thus the energy consumption may be reduced. Besides, with the progress of the thermite reaction, the liquid silicon may gradually aggregate to form a big liquid silicon foam, so that the liquid silicon may be easily separated with the slag. With the method for preparing the high purity silicon according to an embodiment of the present disclosure, the raw material mixture may be melted before the thermite reaction, so that the whole reaction is conducted in the liquid state. Therefore, the reaction rate may be increased, and the liquid silicon may be easily aggregated together so that the liquid silicon may be easily separated from the slag.
Because the carbon reducing agent used in the carbothermal reduction method is mainly originated from a plant, the contents of B, P and other impurities in the carbon reducing agent may be high. Accordingly, the silicon product obtained through the carbothermal reduction method may contain impurities such as B and P with a high content According to an embodiment of the present disclosure, the reducing agent is the aluminum powder, in which the impurity may be mainly metal elements and may be easily removed in the subsequent treatment steps. In addition, the thermite reaction belongs to the drastic exothermic reaction, and compared with the carbothermal reduction method, the energy consumption in the thermite reaction may be less. Moreover, the byproduct such as the slag may have high utilization value in industry, for example, could be used to prepare building materials and cements, thus saving the producing cost.
As described above, the impurities in the silicon product obtained through the method for preparing the high purity silicon according to an embodiment of the present disclosure are mainly metal impurities, which may be easily removed by pickling to further purify the silicon product. Specifically, the method for preparing the silicon product according to an embodiment of the present disclosure may also comprise a further purification step, which comprises pickling and directional solidification for the silicon product obtained through the thermite reaction. Accordingly, after the further purification step, the further purified silicon may be obtained.
According to an embodiment of the present disclosure, the obtained high purity silicon may have a purity of above about 99.99%, and consequently could be used to prepare the solar battery. The content of B may also satisfy the requirement of preparing the solar battery. Specifically, according to an embodiment of the present disclosure, the method further comprises the following steps of: grinding the silicon product obtained through the thermite reduction reaction into a silicon powder with an average particle size of about 75um to 150um (equivalent to about 100 mesh to about 200 mesh); and then adding the obtained silicon powder to an pickling solution allowing pickling, for example, stirring and pickling the silicon powder at a temperature of about 25 °C to about 80 °C for about 1 hour to about 4 hours; separating the pickled silicon powder from the pickling solution, and then washing and drying the pickled silicon powder; and finally melting the dried silicon powder and directionally solidifying the melted silicon powder to obtain a directionally solidified high purity silicon. There are no special limits on the method used to conduct directional solidification. According to an embodiment of the present disclosure, the directionally solidified high purity silicon may be obtained through the following steps of: adding the pickled silicon powder into a directional solidification casting furnace to melt the silicon powder and obtain a melted silicon slurry, and then cooling the melted silicon slurry under a pressure of about 5000Pa to about lOOOOPa at a cooling rate of about 30°C/h to 40°C/h along a predetermined direction, for example, from bottom to top. According to some embodiments of the present disclosure, during the pickling process, the impurities such as Fe, Al, Ca, Ti, B and P, may be removed from the silicon product by virtue of the chemical action of an acid. According to some embodiments of the present disclosure, the pickling solution may be a mixture comprising hydrochloric acid, nitric acid and hydrofluoric acid. According to a specific embodiment of the present disclosure, the pickling solution may comprise about 5wt% to about 15wt% of hydrochloric acid, about 5wt% to about 15wt% of nitric acid, and about 5wt% to about 15wt% of hydrofluoric acid. According to some embodiments of the present disclosure, the impurities may be aggregated in a fixed part by directional solidification, so that the impurities in the silicon, such as Fe, Al, Ca, Ti and B may be easily removed. In addition, it has been found by the inventors that P may also be removed by directional solidification. According to some embodiments of the present disclosure, the part of the directionally solidified high purity silicon in which the impurities are enriched may be cut off so as to further increase the purity of the solidified high purity silicon. Therefore, the method for preparing the high purity silicon according to an embodiment of the present disclosure may be short in technological process and simple in operation, because the complicated step of removing the impurities such as B and P is omitted.
In the following, the present disclosure will be described in detail with reference to particular embodiments. These embodiments should not be construed to limit the scope of the present disclosure in any way.
Embodiment 1
Raw materials:
Quartz sand: having a purity of about 99wt% and a particle size of less than about 1mm. Aluminum powder: having a purity of about 99wt% and a particle size of less than about lmm.
Calcium oxide powder: having a purity of about 95wt% and a particle size of less than about lmm.
Fluorite powder: having a purity of about 95wt% and a particle size of less than about lmm. 1) The quartz sand, the aluminum powder, the calcium oxide powder and the fluorite powder were added into a mixer according to a mass ratio of about 5:3 :4:2 and mixed sufficiently to prepare a raw material mixture.
2) The raw material mixture was added into a medium frequency induction furnace, heated to about 1000°C at a heating rate of about 20°C/min, and then heated at a heating rate of about 10°C /min until the raw material mixture was melted completely. The melted raw material mixture was smelted at a temperature of about 1500°C for about 35min to obtain a liquid silicon. After the smelting process, the obtained liquid silicon was poured out and cooled to obtain a metallurgical grade silicon XI .
3) The metallurgical grade silicon XI was washed and dried, and then ground into a silicon powder of about 100 mesh to about 200 mesh. The silicon powder was dipped into an pickling solution (that is, a mixture comprising about 10wt% of hydrochloric acid, about 10wt% of nitric acid and about 10wt% of hydrofluoric acid) and stirred at a temperature of about 60 °C for about 4 hours, followed by washing the pickled silicon powder in deionized water until the solution was neutral and then drying the washed silicon powder. 4) The dried silicon powder was added into a directional solidification casting furnace and heated until the silicon powder was melted completely to obtain a melted silicon slurry. Then the melted silicon slurry was solidified from bottom to top at a cooling rate of about 30°C7h under a pressure inside the furnace of about 5000Pa to obtain a directionally solidified high purity silicon. Finally, after the solidification was finished, the upper end of the directionally solidified high purity silicon in which an impurity was enriched was cut off to obtain a solar grade silicon Yl .
Embodiment 2
Raw materials:
Quartz sand: having a purity of about 99wt% and a particle size of less than about 1mm.
Aluminum powder: having a purity of about 98wt% and a particle size of less than about lmm.
Calcium oxide powder: having a purity of about 95wt% and a particle size of less than about lmm.
Fluorite powder: having a purity of about 95wt% and a particle size of less than about lmm.
1) The quartz sand, the aluminum powder, the calcium oxide powder and the fluorite powder were added into a mixer according to a mass ratio of about 5:3 :5:2.5 and mixed sufficiently to prepare a raw material mixture.
2) The raw material mixture was added into a medium frequency induction furnace, heated to about 1000°C at a heating rate of about 22°C/min, and then heated at a heating rate of about 12°C
/min until the raw material mixture was melted completely. The melted raw material mixture was smelted at a temperature of about 1550°C for about 40min to obtain a liquid silicon. After the smelting process, the obtained liquid silicon was poured out and cooled to obtain a metallurgical grade silicon X2.
3) The metallurgical grade silicon X2 was washed and dried, and then ground into a silicon powder of about 100 mesh to about 200 mesh. The silicon powder was dipped into an pickling solution (that is, a mixture comprising about 10wt% of hydrochloric acid, about 10wt% of nitric acid and about 10wt% of hydrofluoric acid) and stirred at a temperature of about 70 °C for about 3 hours, followed by washing the pickled silicon powder in deionized water until the solution was neutral and then drying the washed silicon powder. 4) The dried silicon powder was added into a directional solidification casting furnace and heated until the silicon powder was melted completely to obtain a melted silicon slurry. Then the melted silicon slurry was solidified from bottom to top at a cooling rate of about 35 °C7h under a pressure inside the furnace of about 6000Pa. Finally, after the solidification was finished, the upper end of the directionally solidified high purity silicon in which an impurity was enriched was cut off to obtain a solar grade silicon Y2.
Embodiment 3
Raw materials:
Quartz sand: having a purity of about 99wt% and a particle size of less than about 1mm.
Aluminum powder: having a purity of about 98wt% and a particle size of less than about lmm.
Calcium oxide powder: having a purity of about 95wt% and a particle size of less than about lmm.
Fluorite powder: having a purity of about 95wt% and a particle size of less than about lmm.
1) The quartz sand, the aluminum powder, the calcium oxide powder and the fluorite powder were added into a mixer according to a mass ratio of about 5:2.5:2: 1 and mixed sufficiently for about 15min to prepare a raw material mixture.
2) The raw material mixture was added into a medium frequency induction furnace, heated to about 1000°C at a heating rate of about 25 °C/min, and then heated at a heating rate of about 15 °C
/min until the raw material mixture was melted completely. The melted raw material mixture was smelted at a temperature of about 1450°C for about 45min to obtain a liquid silicon. After the smelting process, the obtained liquid silicon was poured out and cooled to obtain a metallurgical grade silicon X3.
3) The metallurgical grade silicon X3 was washed and dried, and then ground into a silicon powder of about 100 mesh to about 200 mesh. The silicon powder was dipped into an pickling solution (that is, a mixture comprising about 10wt% of hydrochloric acid, about 10wt% of nitric acid and about 10wt% of hydrofluoric acid) and stirred at a temperature of about 75 °C for about 2 hours, followed by washing the pickled silicon powder in deionized water until the solution was neutral and then drying the washed silicon powder. 4) The dried silicon powder was added into a directional solidification casting furnace and heated until the silicon powder was melted completely to obtain a melted silicon slurry. Then the melted silicon slurry was solidified from bottom to top at a cooling rate of about 32°C7h under a pressure inside the furnace of about 6000Pa to obtain a directionally solidified high purity silicon. Finally, after the solidification was finished, the upper end of the directionally solidified high purity silicon in which an impurity was enriched was cut off to obtain a solar grade silicon Y3.
Embodiment 4
Raw materials:
Quartz sand: having a purity of about 99wt% and a particle size of less than about 1mm.
Aluminum powder: having a purity of about 98wt% and a particle size of less than about lmm.
Calcium oxide powder: having a purity of about 95wt% and a particle size of less than about lmm.
Fluorite powder: having a purity of about 95wt% and a particle size of less than about lmm.
1) The quartz sand, the aluminum powder, the calcium oxide powder and the fluorite powder were added into a mixer according to a mass ratio of about 5 :3.5:4:0.5 and mixed sufficiently for about 15min to prepare a raw material mixture.
2) The raw material mixture was added into a medium frequency induction furnace, heated to about 1000°C at a heating rate of about 28°C/min, and then heated at a heating rate of about 18°C
/min until the raw material mixture was melted completely. The melted raw material mixture was smelted at a temperature of about 1600°C for about 50min to obtain a liquid silicon. After the smelting process, the obtained liquid silicon was poured out and cooled to obtain a metallurgical grade silicon X4.
3) The metallurgical grade silicon X4 was washed and dried, and then ground into a silicon powder of about 100 mesh to about 200 mesh. The silicon powder was dipped into an pickling solution (that is, a mixture consisting of about 10wt% of hydrochloric acid, about 10wt% of nitric acid and about 10wt% of hydrofluoric acid) and stirred at a temperature of about 80 °C for about 3.5 hours, followed by washing the pickled silicon powder in deionized water until the solution was neutral and then drying the washed silicon powder. 4) The dried silicon powder was added into a directional solidification casting furnace and heated until the silicon powder was melted completely to obtain a melted silicon slurry. Then the melted silicon slurry was solidified from bottom to top at a cooling rate of about 36°C7h under a pressure inside the furnace of about 5000Pa to obtain a directionally solidified high purity silicon. Finally, after the solidification was finished, the upper end of the directionally solidified high purity silicon in which an impurity was enriched was cut off to obtain a solar grade silicon Y4.
Embodiment 5
Raw materials:
Quartz sand: having a purity of about 99wt% and a particle size of less than about 1mm.
Aluminum powder: having a purity of about 99wt% and a particle size of less than about lmm.
Calcium oxide powder: having a purity of about 95wt% and a particle size of less than about lmm.
Fluorite powder: having a purity of about 95wt% and a particle size of less than about lmm.
1) The quartz sand, the aluminum powder, the calcium oxide powder and the fluorite powder were added into a mixer according to a mass ratio of about 5:3 :4:2 and mixed sufficiently to prepare a raw material mixture.
2) The raw material mixture was added into a medium frequency induction furnace, heated to about 1000°C at a heating rate of about 30°C/min, and then heated at a heating rate of about 20 °C
/min until the raw material mixture was melted completely. The melted raw material was smelted at a temperature of about 1500°C for about 35min to obtain a liquid silicon. After the smelting process, the obtained liquid silicon was poured out and cooled to obtain a metallurgical grade silicon X5.
3) The metallurgical grade silicon X5 was washed and dried, and then ground into a silicon powder of about 100 mesh to about 200 mesh. The silicon powder was dipped into an pickling solution (that is, a mixture comprising about 10wt% of hydrochloric acid, about 10wt% of nitric acid and about 10wt% of hydrofluoric acid) and stirred at a temperature of about 60 °C for about 4 hours, followed by washing the pickled silicon powder in deionized water until the solution was neutral and then drying the washed silicon powder. 4) The dried silicon powder was added into a directional solidification casting furnace and heated until the silicon powder was melted completely to obtain a melted silicon slurry. Then the melted silicon slurry was solidified from bottom to top at a cooling rate of about 30°C7h under a pressure inside the furnace of about 5000Pa to obtain a directionally solidified high purity silicon. Finally, after the solidification was finished, the upper end of the directionally solidified high purity silicon in which an impurity was enriched was cut off to obtain a solar grade silicon Y5.
Comparative Embodiment 1
Raw materials:
Silica: having a purity of about 99wt% and a particle size of about 5mm to about 30mm.
Charcoal: consisting of about 72% of fixed carbon, about 2.87% of ash and about 20.84% of volatile.
Petroleum coke: consisting of about 84% of fixed carbon, about 0.28% of ash and about 9.11% of volatile.
1) The silica, the charcoal and the petroleum coke were mixed uniformly according to a mass ratio of about 5 : 1.85 : 1.06 to prepare a raw material mixture, and then the raw material mixture was added into a submerged arc furnace to smelt the raw material mixture at high temperature so as to obtain a silicon XC1.
2) The silicon XC1 was washed and dried, and then ground into a silicon powder of about 100 mesh to about 200 mesh. The silicon powder was dipped into an pickling solution (that is, a mixture consisting of about 10wt% of hydrochloric acid, about 10wt% of nitric acid and about 10wt% of hydrofluoric acid) and stirred at a temperature of about 80 °C for about 3.5 hours, followed by washing the pickled silicon powder in deionized water until the solution was neutral and then drying the washed silicon powder.
3) The dried silicon powder was added into a directional solidification casting furnace and heated until the silicon powder was melted completely to obtain a melted silicon slurry. Then the melted silicon slurry was solidified from bottom to top at a cooling rate of about 36°C/h under a pressure inside the furnace of about 6000Pa to obtain a directionally solidified high purity silicon. Finally, after the solidification was finished, the upper end of the directionally solidified high purity silicon in which an impurity was enriched was cut off to obtain a solar grade silicon YCl . Comparative Embodiment 2
Raw materials:
Quartz sand: having a purity of about 99wt% and a particle size of less than about 1mm. Aluminum powder: having a purity of about 98wt% and a particle size of less than about 1mm.
Fluorite powder: having a purity of about 95wt% and a particle size of less than about 1mm.
1) The quartz sand, the aluminum powder and the fluorite powder were added into a mixer and stirred for 15min to obtain a raw material mixture.
2) The raw material mixture was added into a medium frequency induction furnace and heated to about 1000°C at a heating rate of about 20°C/min, and then heated at a heating rate of about 10°C/min until the raw material mixture was sufficiently melted. However, no reaction took place. The melted raw material mixture was smelted at a temperature of about 1500°C for about 35min, but after the smelting process, the silicon could not be separated out.
Performance Test
Inductively coupled plasma mass spectrometer (ICP-MS) was used to measure the contents of B and P in the obtained silicon products. The results are shown in the table 1.
Table 1
Figure imgf000015_0001
As shown in table 1, compared with Comparative Embodiment 1, the contents of B and P in the metallurgical grade silicon XI -X5 may be greatly decreased, which indicates that the method for preparing the metallurgical grade silicon according to an embodiment of the present disclosure may efficiently decrease the contents of B and P in the metallurgical grade silicon. Moreover, the purity of the metallurgical grade silicon prepared according to the method of the present disclosure may be increased. In Embodiments 1-5, the metallurgical grade silicon may be subjected to acid washing and directional solidification to obtain the solar grade silicon. However, after acid washing and directional solidification, the purity of the silicon obtained in Comparative Embodiment 1 may not meet the requirement of solar grade silicon, and the silicon obtained in Comparative Embodiment 1 may contain a plenty of B and P, so that tedious steps should be carried out to remove the impurities. Therefore, the method for preparing solar grade silicon according to an embodiment of the present disclosure may be short in technological process and easy in purification, because the process for removing the impurities such as B and P is omitted.
Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that changes, alternatives, and modifications all falling into the scope of the claims and their equivalents may be made in the embodiments without departing from spirit and principles of the disclosure.

Claims

What is claimed is:
1. A method for preparing a high purity silicon, comprising steps of:
providing a raw material mixture containing a quartz sand, an aluminum powder and a fluorite powder;
heating the raw material mixture to a temperature of about 1100°C to about 1700°C to melt the raw material mixture allowing a thermite reaction to obtain a liquid silicon and a slag; and separating and cooling the liquid silicon to obtain a silicon product, the impurity content of which is less than lwt%.
2. The method according to claim 1, wherein the raw material mixture further contains calcium oxide.
3. The method according to claim 2, wherein each particle size of the quartz sand, the aluminum powder, the fluorite powder and the calcium oxide powder is less than 1mm.
4. The method according to claim 1, wherein the mass ratio of the quartz sand to the aluminum powder is about 2 : 1 to about 10 : 7.
5. The method according to claim 2, wherein the mass ratio of the quartz sand to the calcium oxide is about 5 : 2 to about 1 : 1.
6. The method according to claim 1, wherein the fluorite powder is present in an amount of about 5wt% to about 17wt% based on the total weight of the raw material mixture.
7. The method according to claim 1, wherein the step of heating and melting the raw material mixture comprises:
increasing the temperature at a heating rate of about 20°C/min to about 30°C7min to a temperature of about 1000°C to about 1 100°C, and then adjusting the heating rate to about 10°C /min to about 20°C7min.
8. The method according to claim 1, wherein the raw material mixture is heated at a temperature of about 1400°C to about 1600°C for about 35min to about 60min.
9. The method according to any one of claims 1-8, further comprising the steps of:
grinding the silicon product obtained into silicon powder with an average particle size of about 75μιη ΐο 150μιτι;
adding the silicon powder to an pickling solution allowing pickling;
separating the pickled silicon powder from the pickling solution, and then washing and drying the pickled silicon powder; adding the pickled silicon powder into a directional solidification casting furnace to melt the silicon powder and obtain a melted silicon slurry; and
cooling the melted silicon slurry along a predetermined direction at a cooling rate of about 30 °C/h to about 40°C/h under a pressure of about 5000Pa to about lOOOOPa to obtain a directionally solidified high purity silicon.
10. The method according to claim 9, wherein the pickling solution is a mixture comprising a hydrochloric acid of about 5wt% to about 15wt%, a nitric acid of about 5wt% to about 15wt% and a hydrofluoric acid of about 5wt% to about 15wt%.
11. The method according to claim 9, further comprises a step of cutting down a part of the directionally solidified high purity silicon in which an impurity is enriched.
PCT/CN2011/076517 2010-06-29 2011-06-28 Method for preparing high purity silicon WO2012000428A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
CN201010218843 2010-06-29
CN201010218843.0 2010-06-29

Publications (1)

Publication Number Publication Date
WO2012000428A1 true WO2012000428A1 (en) 2012-01-05

Family

ID=45401396

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2011/076517 WO2012000428A1 (en) 2010-06-29 2011-06-28 Method for preparing high purity silicon

Country Status (1)

Country Link
WO (1) WO2012000428A1 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102627394A (en) * 2012-04-02 2012-08-08 锦州新世纪多晶硅材料有限公司 Method for decreasing content of boron impurity in silicon metal through metallurgical process
CN108190894A (en) * 2018-01-19 2018-06-22 江苏泽龙石英有限公司 A kind of pickling circulation technology of glass sand
CN109233766A (en) * 2018-10-15 2019-01-18 中国石油大学(华东) A kind of high temperature resisting corrosion resisting low-density well cementing liquid and its compositions of additives and application
CN112110637A (en) * 2020-09-07 2020-12-22 齐鲁工业大学 Impurity removal system and impurity removal process for quartz mineral powder
JP2021066645A (en) * 2019-10-28 2021-04-30 Seavac株式会社 Method for producing silicon

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4304763A (en) * 1979-08-16 1981-12-08 Consortium Fur Elektrochemische Industrie Gmbh Process for purifying metallurgical-grade silicon
US4457903A (en) * 1982-03-11 1984-07-03 Heliotronic Forshungs Und Entwicklungsgesellschaft Fur Solarzellen Grundstoffe Mbh Semicontinuous process for the production of pure silicon
WO2004101434A1 (en) * 2003-05-15 2004-11-25 Helmut Engel The metallurgical method of receiving the high purity silicon powder by chemical processing
WO2006041271A1 (en) * 2004-10-12 2006-04-20 The Ministry Of Education And Sciences Of Republic Kazakhstan Republican State Enterprise 'center Of Chemical-Technological Researches' Method of production of pure silicon

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4304763A (en) * 1979-08-16 1981-12-08 Consortium Fur Elektrochemische Industrie Gmbh Process for purifying metallurgical-grade silicon
US4457903A (en) * 1982-03-11 1984-07-03 Heliotronic Forshungs Und Entwicklungsgesellschaft Fur Solarzellen Grundstoffe Mbh Semicontinuous process for the production of pure silicon
WO2004101434A1 (en) * 2003-05-15 2004-11-25 Helmut Engel The metallurgical method of receiving the high purity silicon powder by chemical processing
WO2006041271A1 (en) * 2004-10-12 2006-04-20 The Ministry Of Education And Sciences Of Republic Kazakhstan Republican State Enterprise 'center Of Chemical-Technological Researches' Method of production of pure silicon

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102627394A (en) * 2012-04-02 2012-08-08 锦州新世纪多晶硅材料有限公司 Method for decreasing content of boron impurity in silicon metal through metallurgical process
CN108190894A (en) * 2018-01-19 2018-06-22 江苏泽龙石英有限公司 A kind of pickling circulation technology of glass sand
CN109233766A (en) * 2018-10-15 2019-01-18 中国石油大学(华东) A kind of high temperature resisting corrosion resisting low-density well cementing liquid and its compositions of additives and application
CN109233766B (en) * 2018-10-15 2020-12-08 中国石油大学(华东) High-temperature-resistant corrosion-resistant low-density well cementing fluid, additive composition and application thereof
JP2021066645A (en) * 2019-10-28 2021-04-30 Seavac株式会社 Method for producing silicon
CN112110637A (en) * 2020-09-07 2020-12-22 齐鲁工业大学 Impurity removal system and impurity removal process for quartz mineral powder
CN112110637B (en) * 2020-09-07 2021-04-16 齐鲁工业大学 Impurity removal system and impurity removal process for quartz mineral powder

Similar Documents

Publication Publication Date Title
JP4159994B2 (en) Method for purifying silicon, slag for silicon purification, and purified silicon
CA1133681A (en) Process for purifying silicon, and the silicon so produced
JP4856738B2 (en) Manufacturing method of high purity silicon material
WO2012000428A1 (en) Method for preparing high purity silicon
CN103359736A (en) Method for purifying and preparing silicon carbide powder from crystalline silicon cutting waste mortar
CN102229430B (en) Technical method for preparing solar energy polycrystalline silicon by using metallurgical method
CN104058405B (en) A kind of remove foreign matter of phosphor and the method for boron in metallic silicon
CN107747119A (en) A kind of method for preparing crystalline silicon with the diamond wire cutting waste material of crystalline silicon
CN105540593B (en) A kind of slagging agent living removes the method and its device of boron
CN102260909A (en) Method for purifying silicon
CN101362600B (en) Method for removing boron from polysilicon by wet metallargy
CN102746936A (en) Recycling purification method for carborundum powder in silicon slice cutting waste liquid
CN109704343A (en) A kind of mixture, melting method, metallic silicon and its recovery method
CN107267780A (en) A kind of production method of vananum
CN105293502B (en) A kind of method that refining industrial silicon prepares solar energy level silicon
CN108793170A (en) A kind of ventilation slag making of industrial silicon is smelted combine pretreatment after acid cleaning process
CN105274619A (en) Method for intensively removing boron in metallurgy-grade silicon
CN106082232B (en) The method of intermediate frequency (IF) smelting recovery polishing silica flour
CN102107874A (en) Method for removing boron and phosphorus in silicon at low temperature
CN107312931A (en) It is a kind of at the same reclaim noble metal and prepare HIGH-PURITY SILICON method
CN110467185B (en) Silicon material dephosphorization purification additive and purification method
CN112110450A (en) Method for removing impurity boron in metallurgical-grade silicon
CN108950143B (en) Comprehensive utilization method of phosphorus and iron as yellow phosphorus smelting by-product
CN103693648B (en) A kind of method strengthening the removal of impurities of industrial silicon wet chemistry
Chen et al. High-value recycling of photovoltaic silicon waste: Accelerated removal of impurity boron through Na3AlF6-enhanced slag refining

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 11800173

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase in:

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 11800173

Country of ref document: EP

Kind code of ref document: A1