CN102241399B - A kind of method of preparing low-boron, low-phosphorus high-purity silicon by electrothermal metallurgy process - Google Patents
A kind of method of preparing low-boron, low-phosphorus high-purity silicon by electrothermal metallurgy process Download PDFInfo
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Abstract
A method for preparing low-boron, low-phosphorus high-purity silicon by electrothermal metallurgy process, belongs to metallurgical technology field, carries out according to the following steps: the silicon-dioxide basis raw material and the carbonaceous reducing agent that adopt the weight content≤10ppm of boron and phosphorus; Add binding agent after mixing, make binding material, be pressed into agglomerate, be placed in mineral hot furnace and carry out electric heating smelting, prepare low boron phosphorus HIGH-PURITY SILICON.The inventive method effectively can avoid the furnace bottom rising in smelting process, ensures carrying out continuously of smelting.The present invention is by controlling the content of boron and phosphorus impurities in raw material, control the content of critical impurities boron phosphorus in silicon product, the low boron phosphorus HIGH-PURITY SILICON utilizing electrothermal metallurgy method to prepare, for next step is purified as solar-grade polysilicon provides the raw material of high-quality, this just reduce further production energy consumption and the cost of solar energy polycrystalline silicon.
Description
Technical field
The invention belongs to metallurgical technology field, particularly a kind of method of preparing low-boron, low-phosphorus high-purity silicon by electrothermal metallurgy process.
Background technology
In recent years the oil in the whole world and the resource growing tension such as coal, renewable energy resources sun power becomes 21 century most important new forms of energy because of inexhaustible, clean environment firendly, the advantage such as safe and reliable.Developed country formulates the policy of encourage growth photovoltaic industry one after another, global solar industry entry high-speed development period, in recent years, global photovoltaic industry every year with 40 ~ 50% rate of increase development.The regional sunshine duration of China 2/3, most suitable development sun power, China greatly developed solar energy industry now at more than 2000h/a.
To prepare solar cell critical material used be purity is 6N(99.9999%) polysilicon.The main method of producing solar-grade polysilicon at present in the world has improved Siemens, silane thermal decomposition process and fluidized bed process, the patented technology of these methods rests in outer national champion completely, the production of polysilicon technology of kiloton scale for a long time by U.S., moral, move, the company monopolizing of Deng state.Based on China prepared by solar-grade polysilicon to the active demand of gordian technique, high for the energy consumption existed in existing solar-grade polysilicon production process, the problems such as cost is high and seriously polluted, research and development metallurgy method produces cleaning procedure and the gordian technique of solar-grade polysilicon, form the polysilicon clearer production technology with independent intellectual property right, break international monopoly, realize the low cost of solar-grade polysilicon, less energy-consumption and eco-friendly suitability for industrialized production, this is to the Sustainable development of China's photovoltaic industry, solve energy security and alleviate China's reduction of greenhouse gas discharge pressure and there is great strategic importance.
Improve the complex process of the methods such as siemens, investment is large, energy consumption is high, makes holding at high price of polysilicon.And metallurgy method prepares solar-grade polysilicon that because having, cost is low, low, less investment, the environment amenable advantage of consuming energy and become study hotspot both domestic and external.Current studies in China metallurgy method prepares solar-grade polysilicon, the overwhelming majority is for raw material with the industrial silicon of metallurgical grade or chemical grade or industrial silica fume, adopt the methods such as grinding, pickling, external refining, vacuum refinement and directional freeze to purify, but these methods are all difficult to the boron in silicon and phosphorus impurities the scope being removed to requirement.In silicon boron and phosphorus impurities be difficult to removing, become metallurgy method and prepared the technical bottleneck that solar-grade polysilicon is difficult to realize.
Summary of the invention
When preparing polysilicon for prior art metallurgy method, boron phosphorus critical impurities is difficult to the problem removed, the invention provides a kind of method of preparing low-boron, low-phosphorus high-purity silicon by electrothermal metallurgy process, silica material low for boron phosphorus content and carbonaceous reducing agent and binding agent are together pressed into agglomerate, then prepare the HIGH-PURITY SILICON of low boron phosphorus by electrothermal metallurgy method.
The present invention carries out according to the following steps:
1. Feedstock treating:
Choose SiO
2weight content>=98% and the silica material of the weight content≤50ppm of the weight content≤50ppm of boron and phosphorus, be broken into the powder of granularity≤3mm as silicon dioxide powder; When boron in silicon dioxide powder and phosphorus weight content all≤10ppm time, directly as silicon-dioxide basis raw material; As the weight content > 10ppm of boron in silicon dioxide powder or phosphorus, silicon dioxide powder is mixed with inorganic acid solution, blending ratio is by weight being silicon dioxide powder: inorganic acid solution=1:4 ~ 20, then under 20 ~ 90 DEG C of conditions acid treatment 2 ~ 72h; Surperficial acid solution is removed with water cleaning after acid treatment, drier removal moisture, then under 300 ~ 1200 DEG C of conditions with vacuum tightness≤1000Pa, insulation 0.5 ~ 6h carries out vacuum heat treatment, and the material of acquisition is as silicon-dioxide basis raw material;
Choose the carbon raw material of the weight content≤50ppm of boron and the weight content≤50ppm of phosphorus, be broken into the powder of granularity≤3mm as carbonaceous powder; When boron and phosphorus in carbonaceous powder weight content all≤10ppm, directly as carbonaceous reducing agent; As the weight content > 10ppm of boron or phosphorus in carbonaceous powder, mixed by carbonaceous powder with inorganic acid solution, blending ratio is by weight being carbonaceous powder: inorganic acid solution=1:4 ~ 20, then under 20 ~ 90 DEG C of conditions acid treatment 2 ~ 72h; Surperficial acid solution is removed with water cleaning after acid treatment, drier removal moisture, then under 300 ~ 1200 DEG C of conditions with vacuum tightness≤1000Pa, insulation 0.5 ~ 6h carries out vacuum heat treatment, and the material of acquisition is as carbonaceous reducing agent;
2, batching briquetting:
By silicon-dioxide basis raw material and carbonaceous reducing agent mix, the amount of allocating into of C is by reduction SiO
20.9 ~ 1.0 times of batching of required theoretical carbon amounts, the reaction equation of charge calculation institute foundation is SiO
2+ 2C=Si+ 2CO, wherein C is fixation of C in carbonaceous reducing agent; Then in the material of mixing, add binding agent, the add-on of binding agent is 2 ~ 8% of silicon-dioxide basis raw material and carbonaceous reducing agent gross weight, mixes and makes binding material;
3, electric heating smelting:
Binding material is pressed into the agglomerate of particle diameter 10 ~ 50mm, agglomerate is placed in and adopts the mineral hot furnace of Graphite Electrodes to do to carry out electric heating smelting, make the HIGH-PURITY SILICON of low boron phosphorus; Weight content >=99.9% of Si in low boron phosphorus HIGH-PURITY SILICON, the weight content≤10ppm of boron, the weight content≤10ppm of phosphorus.
In the above-mentioned carbonaceous reducing agent after peracid treatment and vacuum heat treatment and silicon-dioxide basis raw material, the weight content of boron and phosphorus all≤10ppm.
Above-mentioned inorganic acid solution is one or more the mixed acid solution in hydrochloric acid, nitric acid and sulfuric acid, and the weight concentration of inorganic acid solution is 3 ~ 20%.
Above-mentioned carbon raw material refers to the one or more kinds of mixtures in refinery coke, graphite, carbon black, metallurgical coke, gac and charcoal.
Above-mentioned silica material is one or more the mixture in silica, natural quartz, synthetic quartz, quartz sand, fused quartz and discarded quartz crucible.
Above-mentioned silica material is bulk, gravel shape, sheet, briquet shape, Powdered or particulate state.
Above-mentioned binding agent is one in water glass, alcohol, whiteruss and polyvinyl alcohol or several.
Particle diameter 10 ~ 50mm the agglomerate suppressed in aforesaid method, after drying, the requirement of strength of agglomerate is highly free to drop down to cement flooring from 2m and does not pulverize.
In aforesaid method, after acid treatment, dry moisture of removing refers to and to dry to moisture weight content≤3% under 100 ± 5 DEG C of conditions.
In Graphite Electrodes in above-mentioned mineral hot furnace the weight content of phosphorus and boron all≤10ppm.
Method of the present invention is the improvement to preparation HIGH-PURITY SILICON step in the disclosed patent applications " technique of preparing solar-grade polysilicon by adopting high-temperature metallurgy method " such as Xing Pengfei, the technique of preparing solar-grade polysilicon by adopting high-temperature metallurgy method by after pre-treatment, arc smelting, external refining and vacuum refinement, then makes solar-grade polysilicon through directional freeze.Mixed carbon comtent in the method employing batching is 1.1 ~ 1.3 times of theoretical amount, and for crossing carbon amounts batching, the smelting in mineral hot furnace was that carbon amounts is smelted, and this can cause, and furnace bottom goes up gradually, the melting continuously cycle is short; Boron simultaneously in the silicon produced of the method arc smelting and the weight content of phosphorus are all greater than 10ppm, cause subsequent step technique more complicated.Method of the present invention by pickling and high-temperature vacuum process control in advance silicon-dioxide basis raw material and carbonaceous reducing agent in boron and phosphorus content≤10ppm, then add binding agent and be pressed into agglomerate to ensure good air permeability when furnace reduction is reacted, then carry out electric heating smelting, prepare boron phosphorus content all≤the low boron phosphorus HIGH-PURITY SILICON of 10ppm.Mixed carbon comtent in the present invention's batching is 0.9 ~ 1.0 times of theoretical amount, prepares burden for losing carbon, and the smelting in mineral hot furnace is smelted for losing carbon amounts, effectively can avoid the furnace bottom rising in smelting process, ensure carrying out continuously of smelting.
The present invention is by controlling the content of boron and phosphorus impurities in raw material, control the content of critical impurities boron phosphorus in silicon product, the low boron phosphorus HIGH-PURITY SILICON utilizing electrothermal metallurgy method to prepare, for next step is purified as solar-grade polysilicon provides the raw material of high-quality, this just reduce further production energy consumption and the cost of solar energy polycrystalline silicon.
Embodiment
SiO in the silica adopted in the embodiment of the present invention, natural quartz, synthetic quartz, quartz sand, fused quartz and discarded quartz crucible
2weight content>=98%, boron and phosphorus weight content all≤50ppm, be broken into the powder of granularity≤3mm as silica material.
The refinery coke adopted in the embodiment of the present invention, metallurgical coke, graphite, carbon dust, gac, charcoal and artificial charcoal are technical grade product, the weight content of boron and phosphorus all≤10ppm, be broken into the powder of granularity≤3mm as carbon raw material.
The hydrochloric acid soln adopted in the embodiment of the present invention, salpeter solution and sulphuric acid soln are prepared by industrial acids respectively.
The water glass adopted in the embodiment of the present invention, alcohol, whiteruss and polyvinyl alcohol are commercial technical grade product.
In the embodiment of the present invention, dry moisture of removing refers to and to dry to moisture weight content≤3% under 100 ± 5 DEG C of conditions.
embodiment 1
Weight concentration is adopted to be that the sulfuric acid of 20% is as inorganic acid solution;
Adopt and be broken into the powder of granularity≤3mm as silicon dioxide powder by silica, SiO
2weight content 98.0%, the weight content 20ppm of boron, the weight content 35ppm of phosphorus; Mixed with inorganic acid solution by silicon dioxide powder, blending ratio is by weight being silicon dioxide powder: inorganic acid solution=1:15, then under 60 DEG C of conditions acid treatment 18h; Surperficial acid solution is removed with water cleaning after acid treatment, drier removal moisture, then under 1200 DEG C and vacuum condition, be incubated 2h and heat-treat, the material of acquisition is as silicon-dioxide basis raw material; In silica material after pickling and thermal treatment, the weight content of boron is 8ppm, and the weight content of phosphorus is 10ppm;
The refinery coke of employing granularity≤3mm and charcoal are as carbonaceous powder, and wherein the fixing carbon amounts of refinery coke accounts for 80% of total mixed carbon comtent, and the fixing carbon amounts of charcoal accounts for 20% of total mixed carbon comtent; The weight content of the boron wherein in refinery coke is 4ppm, the weight content 8ppm of phosphorus; The weight content of the boron in charcoal is 30ppm, and the weight content of phosphorus is 50ppm; Mixed with inorganic acid solution by carbonaceous powder, blending ratio is by weight being carbonaceous powder: inorganic acid solution=1:20, then under 40 DEG C of conditions acid treatment 36h; Surperficial acid solution is removed with water cleaning after acid treatment, drier removal moisture, then under 800 DEG C and vacuum condition, be incubated 4h and carry out vacuum heat treatment, the material of acquisition is as carbonaceous reducing agent; In carbon raw material after pickling and thermal treatment, the weight content of boron is 8ppm, and the weight content of phosphorus is 10ppm;
Above-mentioned vacuum condition refers to vacuum tightness≤1000Pa;
Silicon-dioxide basis raw material and carbonaceous reducing agent are mixed and made into mixture, and blending ratio is by reduction SiO
20.90 times of batching of C amount needed for reaction theory; Then in the material of mixing, add binder liquid paraffin body, the add-on of whiteruss is 4% of mixture gross weight, makes binding material after mixing;
Binding material is pressed into the agglomerate of particle diameter 10 ~ 50mm, the requirement of strength of agglomerate is highly free to drop down to cement flooring from 2m and does not pulverize.Select the mineral hot furnace being provided with Graphite Electrodes as smelting furnace, the phosphorus in the Graphite Electrodes of mineral hot furnace and boron weight content all≤10ppm.Agglomerate is placed in smelting furnace and carries out arc smelting, prepare low boron phosphorus HIGH-PURITY SILICON, the weight content 99.90% of Si in low boron phosphorus HIGH-PURITY SILICON, the weight content 5ppm of boron, the weight content 10ppm of phosphorus.
embodiment 2
Weight concentration is adopted to be that the hydrochloric acid of 8% is as inorganic acid solution;
Adopt be broken into granularity by natural quartz and be≤silica powder of 3mm as silicon dioxide powder, SiO
2weight content 99.0%, the weight content 6ppm of boron, the weight content 12ppm of phosphorus; Mixed with inorganic acid solution by silicon dioxide powder, blending ratio is by weight being silicon dioxide powder: inorganic acid solution=1:4, then under 90 DEG C of conditions acid treatment 0.5h; Surperficial acid solution is removed with water cleaning after acid treatment, drier removal moisture, then under 1000 DEG C and vacuum condition, be incubated 0.5h and heat-treat, the material of acquisition is as silicon-dioxide basis raw material; In silica material after pickling and thermal treatment, the weight content of boron is 4ppm, and the weight content of phosphorus is 8ppm;
The metallurgical coke of employing granularity≤3mm and gac are as carbonaceous powder, and wherein the fixing carbon amounts of metallurgical coke accounts for 85% of total mixed carbon comtent, and the fixing carbon amounts of gac accounts for 15% of total mixed carbon comtent; The weight content of the boron wherein in metallurgical coke is 15ppm, the weight content 26ppm of phosphorus; The weight content of the boron in gac is 28ppm, and the weight content of phosphorus is 45ppm; Mixed with inorganic acid solution by carbonaceous powder, blending ratio is by weight being carbonaceous powder: inorganic acid solution=1:15, then under 50 DEG C of conditions acid treatment 36h; Surperficial acid solution is removed with water cleaning after acid treatment, drier removal moisture, then under 300 DEG C and vacuum condition, be incubated 6h and carry out vacuum heat treatment, the material of acquisition is as carbonaceous reducing agent; In carbon raw material after pickling and thermal treatment, the weight content of boron is 5ppm, and the weight content of phosphorus is 10ppm;
Above-mentioned vacuum condition refers to vacuum tightness≤1000Pa;
Silicon-dioxide basis raw material and carbonaceous reducing agent are mixed and made into mixture, and blending ratio is by reduction SiO
20.9 times of batching of C amount needed for reaction theory; Then in the material of mixing, add water glass of binder, the add-on of water glass is 8% of mixture gross weight, makes binding material after mixing;
Binding material is pressed into the agglomerate of particle diameter 10 ~ 50mm, the requirement of strength of agglomerate is highly free to drop down to cement flooring from 2m and does not pulverize.Select the mineral hot furnace being provided with Graphite Electrodes as smelting furnace, require phosphorus in the Graphite Electrodes of mineral hot furnace and boron weight content all≤10ppm.Agglomerate is placed in smelting furnace and carries out arc smelting, prepare low boron phosphorus HIGH-PURITY SILICON, the weight content 99.90% of Si in low boron phosphorus HIGH-PURITY SILICON, the weight content 3ppm of boron, the weight content 8ppm of phosphorus.
embodiment 3
Weight concentration is adopted to be that the nitric acid of 5% is as inorganic acid solution;
Adopt and be broken into the powder of granularity≤3mm as silicon dioxide powder by synthetic quartz, SiO
2weight content 99.5%, the weight content 5ppm of boron, the weight content 10ppm of phosphorus, using silicon dioxide powder directly as silicon-dioxide basis raw material;
The metallurgical coke adopting granularity≤3mm is carbonaceous powder, and the weight content of the boron in metallurgical coke is 15ppm, the weight content 26ppm of phosphorus; Mixed with inorganic acid solution by carbonaceous powder, blending ratio is by weight being carbonaceous powder: inorganic acid solution=1:10, then under 40 DEG C of conditions acid treatment 72h; Surperficial acid solution is removed with water cleaning after acid treatment, drier removal moisture, then under 500 DEG C and vacuum condition, be incubated 4h and carry out vacuum heat treatment, the material of acquisition is as carbonaceous reducing agent; In carbon raw material after pickling and thermal treatment, the weight content of boron is 5ppm, and the weight content of phosphorus is 9ppm;
Above-mentioned vacuum condition refers to vacuum tightness≤1000Pa;
Silicon-dioxide basis raw material and carbonaceous reducing agent are mixed and made into mixture, and blending ratio is by reduction SiO
21.0 times of batchings of C amount needed for reaction theory; Then in the material of mixing, add binding agent alcohol, the add-on of alcohol is 6% of mixture gross weight, makes binding material after mixing;
Binding material is pressed into the agglomerate of particle diameter 10 ~ 50mm, the requirement of strength of agglomerate is highly free to drop down to cement flooring from 2m and does not pulverize.Select the mineral hot furnace being provided with Graphite Electrodes as smelting furnace, require phosphorus in the Graphite Electrodes of mineral hot furnace and boron weight content all≤10ppm.Agglomerate is placed in smelting furnace and carries out arc smelting, prepare low boron phosphorus HIGH-PURITY SILICON, the weight content 99.92% of Si in low boron phosphorus HIGH-PURITY SILICON, the weight content 3ppm of boron, the weight content 8ppm of phosphorus.
embodiment 4
Adopt the quartz sand of granularity≤3mm as silicon dioxide powder, SiO
2weight content 99.6%, the weight content 4ppm of boron, the weight content 9ppm of phosphorus, using silicon dioxide powder directly as silicon-dioxide basis raw material;
Adopt the carbon black of granularity≤3mm as carbonaceous powder, the weight content 5ppm of boron, the weight content 8ppm of phosphorus; Using carbonaceous powder directly as carbonaceous reducing agent;
Silicon-dioxide basis raw material and carbonaceous reducing agent are mixed and made into mixture, and blending ratio is by reduction SiO
20.98 times of batching of C amount needed for reaction theory; Then in the material of mixing, add binding agent polyvinyl alcohol, the add-on of polyvinyl alcohol is 2% of mixture gross weight, makes binding material after mixing;
Binding material is pressed into the agglomerate of particle diameter 10 ~ 50mm, the requirement of strength of agglomerate is highly free to drop down to cement flooring from 2m and does not pulverize.Select the mineral hot furnace being provided with Graphite Electrodes as smelting furnace, the phosphorus in the Graphite Electrodes of mineral hot furnace and boron weight content all≤10ppm.Agglomerate is placed in smelting furnace and carries out arc smelting, prepare low boron phosphorus HIGH-PURITY SILICON, the weight content 99.92% of Si in low boron phosphorus HIGH-PURITY SILICON, the weight content 3ppm of boron, the weight content 5ppm of phosphorus.
embodiment 5
Adopt and be broken into the powder of granularity≤3mm as silicon dioxide powder by fused quartz, SiO
2weight content 99.8%, the weight content 3ppm of boron, the weight content 5ppm of phosphorus; Using silicon dioxide powder as silicon-dioxide basis raw material;
Adopt the refinery coke of granularity≤3mm as carbonaceous powder, the weight content 4ppm of boron, the weight content 8ppm of phosphorus; Using carbonaceous powder directly as carbonaceous reducing agent;
Silicon-dioxide basis raw material and carbonaceous reducing agent are mixed and made into mixture, and blending ratio is by reduction SiO
20.95 times of batching of C amount needed for reaction theory; Then in the material of mixing, add water glass of binder and alcohol, 4% of each mixture gross weight of the add-on of water glass and alcohol, makes binding material after mixing;
Binding material is pressed into the agglomerate of particle diameter 10 ~ 50mm, the requirement of strength of agglomerate is highly free to drop down to cement flooring from 2m and does not pulverize.Select the mineral hot furnace being provided with Graphite Electrodes as smelting furnace, the phosphorus in the Graphite Electrodes of mineral hot furnace and boron weight content all≤10ppm.Agglomerate is placed in smelting furnace and carries out arc smelting, prepare low boron phosphorus HIGH-PURITY SILICON, the weight content 99.96% of Si in low boron phosphorus HIGH-PURITY SILICON, the weight content 2ppm of boron, the weight content 4ppm of phosphorus.
embodiment 6
Adopt and be broken into the powder of granularity≤3mm as silicon dioxide powder by the quartz crucible discarded, SiO
2weight content 99.9%, the weight content 2ppm of boron, the weight content 4ppm of phosphorus; Using silicon dioxide powder directly as silicon-dioxide basis raw material;
Adopt the graphite of granularity≤3mm as carbonaceous powder, the weight content 2ppm of boron, the weight content 4ppm of phosphorus; Using carbonaceous powder directly as carbonaceous reducing agent;
Silicon-dioxide basis raw material and carbonaceous reducing agent are mixed and made into mixture, and blending ratio is by reduction SiO
20.93 times of batching of C amount needed for reaction theory; Then in the material of mixing, add binder liquid paraffin body and polyvinyl alcohol, the add-on of whiteruss and polyvinyl alcohol is respectively 3% of mixture gross weight, makes binding material after mixing;
Binding material is pressed into the agglomerate of particle diameter 10 ~ 50mm, the requirement of strength of agglomerate is highly free to drop down to cement flooring from 2m and does not pulverize.Select the mineral hot furnace being provided with Graphite Electrodes as smelting furnace, the phosphorus in the Graphite Electrodes of mineral hot furnace and boron weight content all≤10ppm.Agglomerate is placed in smelting furnace and carries out arc smelting, prepare low boron phosphorus HIGH-PURITY SILICON, the weight content 99.99% of Si in low boron phosphorus HIGH-PURITY SILICON, the weight content 1ppm of boron, the weight content 3ppm of phosphorus.
Claims (4)
1. a method for preparing low-boron, low-phosphorus high-purity silicon by electrothermal metallurgy process, is characterized in that carrying out according to the following steps:
(1) SiO is chosen
2weight content>=98% and the silica material of the weight content≤50ppm of the weight content≤50ppm of boron and phosphorus, be broken into the powder of granularity≤3mm as silicon dioxide powder; When boron in silicon dioxide powder and phosphorus weight content all≤10ppm, directly as silicon-dioxide basis raw material; As the weight content > 10ppm of boron in silicon dioxide powder or phosphorus, silicon dioxide powder is mixed with inorganic acid solution, blending ratio is by weight being silicon dioxide powder: inorganic acid solution=1: 4 ~ 20, then under 20 ~ 90 DEG C of conditions acid treatment 2 ~ 72h; Surperficial acid solution is removed with water cleaning after acid treatment, dry removal moisture again, then under the conditions of 300 ~ 1200 DEG C and vacuum tightness≤100Pa, insulation 0.5 ~ 6h carries out vacuum heat treatment, the material of acquisition as silicon-dioxide basis raw material, the weight content of boron and phosphorus all≤10ppm;
Choose the one or more kinds of mixtures in the carbon raw material refinery coke of the weight content≤50ppm of boron and the weight content≤50ppm of phosphorus, graphite, carbon black, metallurgical coke, gac and charcoal, be broken into the powder of granularity≤3mm as carbonaceous powder; When boron and phosphorus in carbonaceous powder weight content all≤10ppm, directly as carbonaceous reducing agent; As the weight content > 10ppm of boron or phosphorus in carbonaceous powder, carbonaceous powder is mixed with inorganic acid solution, blending ratio is by weight being carbonaceous powder: inorganic acid solution=1: 4 ~ 20, then under 20 ~ 90 DEG C of conditions acid treatment 2 ~ 72h; Surperficial acid solution is removed with water cleaning after acid treatment, dry removal moisture again, then under the conditions of 300 ~ 1200 DEG C and vacuum tightness≤1000Pa, insulation 0.5 ~ 6h carries out vacuum heat treatment, the material of acquisition as carbonaceous reducing agent, the weight content of boron and phosphorus all≤10ppm;
(2) by silicon-dioxide basis raw material and carbonaceous reducing agent mix, the amount of allocating into of C is by reduction SiO
20.9 ~ 0.98 times of batching of required theoretical carbon amounts, the reaction equation of charge calculation institute foundation is SiO
2+ 2C=Si+2CO, wherein C is fixation of C in carbonaceous reducing agent; Then in the material of mixing, add binding agent, the add-on of binding agent is 2 ~ 8% of silicon-dioxide basis raw material and carbonaceous reducing agent gross weight, mixes and makes binding material;
(3) binding material is pressed into the agglomerate of particle diameter 10 ~ 50mm, agglomerate is placed in and adopts the mineral hot furnace of Graphite Electrodes to carry out electric heating smelting, make low boron phosphorus HIGH-PURITY SILICON, weight content >=99.9% of Si in low boron phosphorus HIGH-PURITY SILICON, weight content≤the 10ppm of boron, the weight content≤10ppm of phosphorus.
2. the method for a kind of preparing low-boron, low-phosphorus high-purity silicon by electrothermal metallurgy process according to claim 1, is characterized in that described silica material is one or more the mixture in silica, natural quartz, synthetic quartz, quartz sand, fused quartz and discarded quartz crucible.
3. the method for a kind of preparing low-boron, low-phosphorus high-purity silicon by electrothermal metallurgy process according to claim 1, is characterized in that described binding agent is a kind of or two or more mixture in water glass, alcohol, whiteruss and polyvinyl alcohol.
4. the method for a kind of preparing low-boron, low-phosphorus high-purity silicon by electrothermal metallurgy process according to claim 1, it is characterized in that the weight content of phosphorus and boron in the Graphite Electrodes of mineral hot furnace all≤10ppm.
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| CN1219504A (en) * | 1998-11-11 | 1999-06-16 | 重庆市渝西硅化工有限公司 | Production technique for smelting crystalline silicon with complete quartz sand |
| CN101724902A (en) * | 2009-12-16 | 2010-06-09 | 东北大学 | Process for preparing solar-grade polysilicon by adopting high-temperature metallurgy method |
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| CN1219504A (en) * | 1998-11-11 | 1999-06-16 | 重庆市渝西硅化工有限公司 | Production technique for smelting crystalline silicon with complete quartz sand |
| CN101724902A (en) * | 2009-12-16 | 2010-06-09 | 东北大学 | Process for preparing solar-grade polysilicon by adopting high-temperature metallurgy method |
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