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WO2008145236A1 - Procédé économique de production de si par réduction de sicl4 avec du zn liquide - Google Patents

Procédé économique de production de si par réduction de sicl4 avec du zn liquide Download PDF

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Publication number
WO2008145236A1
WO2008145236A1 PCT/EP2008/003276 EP2008003276W WO2008145236A1 WO 2008145236 A1 WO2008145236 A1 WO 2008145236A1 EP 2008003276 W EP2008003276 W EP 2008003276W WO 2008145236 A1 WO2008145236 A1 WO 2008145236A1
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WO
WIPO (PCT)
Prior art keywords
sicl
process according
mol
bath
chloride
Prior art date
Application number
PCT/EP2008/003276
Other languages
English (en)
Inventor
Eric Robert
Tjakko Zijlema
Original Assignee
Umicore
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
Application filed by Umicore filed Critical Umicore
Publication of WO2008145236A1 publication Critical patent/WO2008145236A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/021—Preparation
    • C01B33/027—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material
    • C01B33/033—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material by reduction of silicon halides or halosilanes with a metal or a metallic alloy as the only reducing agents
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/037—Purification

Definitions

  • the invention relates to the manufacture of solar grade silicon (Si) as a feedstock material for the manufacture of crystalline silicon solar cells.
  • Si solar grade silicon
  • the Si metal is obtained by direct reduction of SiCl 4 , a precursor that is commonly available in high purity grades.
  • Silicon suitable for application in solar cells is commonly manufactured by the thermal decomposition of SiHCl 3 according to the Siemens process or its variants. The process delivers very pure silicon, but it is slow, highly energy consuming, and requires large investments.
  • SiCl 4 An alternative route towards the formation of Si for solar cells is the reduction of SiCl 4 with metals such as Zn.
  • This process has the potential for significant cost reduction because of lower investment costs and reduced energy consumption.
  • the direct reduction of SiCl 4 by Zn in the vapour phase is described in US 2,773,745, US 2,804,377, US 2,909,411 or US 3,041,145.
  • Zn vapour When Zn vapour is used, a granular silicon product is formed in a fluidised bed type of reactor, enabling easier Si separation.
  • an industrial process based on this principle is technologically complex.
  • the production of the silicon as a fine powder is not particularly desirable. Indeed, such a powder can very easily oxidize, particularly at the surface of the grain. This oxidation makes it very difficult to subsequently re-melt the silicon to produce poly- or monocrystalline ingots. A pelletization/compactation step would probably be needed, which complicates the process.
  • Al chlorosilane is fed into a metal melt, preferably aluminum, at a flow rate of less than 1.0 mol%/mol.min of the metal.
  • the process is not further explored for the reaction between SiCl 4 and liquid Zn, and hence no optimisation is proposed.
  • the yield of the reaction with Al calculated by dividing the Si (metallic) recovered by the Si input (as SiC14), is 17.1% or lower. This means that (at least) 82.9% of the Si fed into the reactor is lost by entrainment, or has not reacted. It is clear that a system using Al as reductant is highly uneconomical. Furthermore, aluminum is certainly not desirable as an impurity in HP silicon, which fact puts the whole process at risk.
  • the contacting and the separation steps are performed in a single reactor, and characterised in that the contacting step is performed by injecting SiCl 4 at a molar flow rate between 0.1 and 0.8 mol%/mol.min, and preferably between 0.4 and 0.8 mol%/mol.min of the initial Zn quantity, and with a maximum areal supply rate of 50 kg/min per m 2 of bath surface.
  • the contacting and the separating steps are performed in a single reactor. This is rendered possible by the fact that a major part (more than 50% by weight) of the formed Si is retained in the liquid metal phase.
  • the Si-bearing metal phase as obtained in the contacting step will contain, besides Si as solute, also at least some Si in the solid state. Indeed, when the Zn metal gets saturated in Si, solid Si is also formed as suspended particles, but also a Si-Zn dross is obtained, floating on top of the remaining Zn bath.
  • the Si-Zn dross layer is formed quickly, and the losses of particulate Si by entrainment of evaporating Zn- chloride are adequately limited.
  • the molar supply rate is preferably more than or equal to 0.4 mol%/mol.min.
  • the upper limit of 0.8 mol%/mol.min guarantees that the dross layer is not disturbed to the extent that solid Si is entrained too much by the rising gasses.
  • the presence of a Si-Zn dross on top of the bath helps to reach higher flows, as it also prevents the liquid bath from splashing too high and reduces the entrainment of small droplets with the evolving gases.
  • the maximum areal supply rate of the Zn bath should be limited to 50 kg/min per m 2 of bath surface, enabling to blow large quantities Of SiCl 4 without causing excessive splashing. By performing the process within these limits an optimum in process economy can be obtained, whereby the loss of Si by entrainment with evaporating Zn- chloride is limited to less than 15% (weight).
  • An areal supply rate over 10, and preferably 12 or more kg/min per m 2 of bath surface is advised to perform the process in an economical way. Indeed, a high conversion yield of SiCl 4 into Si can be attained even at high injection speed. In that case, the productivity of the installation is directly linked to the injection flow rate. Thus for a given production of Si, the higher the flow rate, the lower the investment is. Also, it is clear that a bath surface of at least 300 cm 2 , aanndd pprreeffeerraabbllyy aatt llee ⁇ ast 500 cm is advisable in combination with the above mentioned working conditions.
  • the gaseous SiCl 4 is adequately dispersed in the bath, e.g. by using multiple submerged nozzles, a submerged nozzle equipped with a porous plug, a rotating gas injector, or any other suitable mean or combination of means.
  • the SiCl 4 can be injected along with a carrier gas such as N 2 .
  • the purification can advantageously be performed in again the same reactor as the first two process steps.
  • the obtained Zn-chloride can be subjected to molten salt electrolysis, thereby recovering Zn, which can be recycled to the SiCl 4 reduction step, and chlorine, which can be recycled to a Si chlorination process for the production of SiCl 4 ;
  • - Zn that is vaporised in the purification step can be condensed and recycled to the SiCl 4 converting process;
  • the fraction of SiCl 4 that exits the contacting step un-reacted can be recycled to the SiCl 4 converting process, e.g. after condensation.
  • SiCl 4 is reduced with liquid Zn.
  • a Si-bearing alloy containing both dissolved and solid Si can be obtained, while the chlorinated Zn is preferably formed as a vapour.
  • Zn can be retrieved from its chloride, e.g. by molten salt electrolysis, and reused for SiCl 4 reduction.
  • the Si-bearing alloy can be purified at high temperatures, above the boiling 5 points of both Zn and Zn-chloride, but below the boiling point of Si itself (2355 °C).
  • the evaporated Zn can be retrieved and reused for SiCl 4 reduction. Any other volatile element is also removed in this step. It is thus possible to close the loop on Zn, thereby avoiding the introduction of impurities into the system through fresh additions.
  • gaseous SiCl 4 is contacted with liquid Zn at atmospheric pressure, at a temperature above the boiling point of ZnCl 2 (732 °C) and below the boiling point of Zn (907 °C).
  • the preferred operating temperature is 750 to 880 °C, a range ensuring sufficiently high reaction kinetics, while the evaporation of metallic Zn remains limited.
  • the molten Zn is placed in a reactor, preferably made of quartz or of another high purity material such as graphite.
  • the SiCl 4 which is liquid at room temperature, is injected in the zinc via a submerged tube. The injection is performed in the lower part of the Zn-containing vessel.
  • the SiCl 4 which is heated in
  • the tube is actually injected as a gas.
  • the SiCl 4 can be vaporized in a separate device and the vapours fed to the injection tube.
  • the end of the injection tube can be provided with a dispersion device such as a porous plug or fritted glass. It is indeed important to have a good contact between the SiCl 4 and the Zn to get a high reduction yield. If this is not the case, partial reduction to SiCl 2 could occur, or SiCl 4
  • the reduction process produces ZnCl 2 . It has a boiling point of 732 °C, and is gaseous at the preferred operating temperature. It leaves the Zn-containing vessel via the top. 30 The vapours are condensed and collected in a separate crucible. The process also produces Si. The Si dissolves in the molten Zn up to its solubility limit. The Si solubility in the Zn increases with temperature and is limited to about 4% at 907 °C, the atmospheric boiling point of pure Zn.
  • the Si-bearing alloy is allowed to cool down to a temperature somewhat above the melting point of the Zn, e.g. 600 °C.
  • a major part of the initially dissolved Si crystallizes upon cooling, and accumulates together with the solid Si that was already present in the bath, in an upper solid fraction.
  • the lower liquid fraction of the metal phase is Si-depleted, and can be separated by any suitable means, e.g. by pouring. This metal can be directly re-used for further SiCl 4 reduction.
  • the upper Si-rich fraction is then subjected to the purification as mentioned above, with the advantage that the amount of Zn to be evaporated is considerably reduced.
  • the molten silicon can be solidified in a single step, chosen from the methods of crystal pulling such as the Czochralski method, directional solidification and ribbon growth.
  • the ribbon growth method includes its variants, such as ribbon-growth-on-substrate (RGS), which directly yields RGS Si wafers.
  • the molten silicon can be granulated, the granules being fed to a melting furnace, preferably in a continuous way, whereupon the molten silicon can be solidified in a single step, chosen from the methods of crystal pulling, directional solidification and ribbon growth.
  • the solid material obtained can then be further processed to solar cells, directly or after wafering, according to the solidification method used.
  • the Zn, together with typical trace impurities such as Tl, Cd and Pb can be separated from the Si-bearing alloy by vaporisation. Si with a purity of 5N to 6N is then obtained. A special high temperature sparging or bubbling step with Cl 2 and/or a gaseous Si chloride typically leads to Si with even superior purity. For this operation, the temperature is further increased above the melting point (1414 °C) but below the boiling point (2355 °C) of Si. Some of the elements that can be eliminated efficiently by this process step are Cr, Cu, Mn, Al, Ca, B and P.
  • a preferred embodiment consists of purifying the Si-bearing metal phase by heating to a temperature above the melting point of Si and injecting Cl 2 and/or a gaseous Si chloride compound into said metal phase, thereby vaporising Zn, eliminating impurities and obtaining Si metal, whereby the contacting and the separation steps are performed in a single reactor.
  • a further advantage of the invention is that the Si can be recovered in the molten state at the end of the purification process.
  • the Si is produced as a solid that has to be re-melted to be fashioned into wafers by any of the commonly used technologies (crystal pulling or directional solidification).
  • Directly obtaining the Si in the molten state allows for a better integration of the feedstock production with the steps towards wafer production, providing an additional reduction in the total energy consumption of the process as well as in the cost of the wafer manufacturing.
  • the liquid Si can indeed be fed directly to an ingot caster or a crystal puller. Processing the Si in a ribbon growth apparatus is also possible.
  • the molten silicon is then cast into a quartz vessel and allowed to solidify to room temperature. 66 kg of metallic silicon are collected. The Si reaction yield is thus about 88 %. The Si losses can be attributed to the entrainment of particles of Si with the escaping ZnCl 2 vapours, and to the incomplete reduction Of SiCl 4 into Si metal. Of the remaining Si, about 6 kg are found in the ZnCl 2 and about 3 kg in the scrubber.
  • the obtained silicon contains less than 5 ppb of B, 0.05 ppm of P, 0.2 ppm of Al and 0.3 ppm of total metallic impurities. Zn is below 50 ppb.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Silicon Compounds (AREA)

Abstract

L'invention concerne un procédé économique de fabrication de silicium à degré de pureté élevé comme substance de base en vue de la production, par exemple, de cellules solaires au silicium. SiCl4 est converti en métal de Si en mettant en contact du SiCl4 gazeux avec du Zn liquide, dans un procédé comprenant les étapes consistant à : - approvisionner une quantité initiale de bain fondu de Zn dans un réacteur ; - souffler du SiCl4 gazeux dans ledit Zn de bain fondu de Zn, obtenant de cette façon une phase métallique comportant du Si et du chlorure de Zn ; - séparer le chlorure de Zn de la phase métallique comportant du Si ; et - purifier la phase métallique comportant du Si à une température supérieure à la température d'ébullition du Zn ; lesdites étapes de mise en contact et de séparation étant réalisées dans un seul réacteur, et caractérisé en ce que l'étape de mise en contact est effectuée en injectant SiCl4 à un débit molaire compris entre 0,1 et 0,8 % mol/mol.mn, et de préférence entre 0,4 et 0,8 % mol/mol.mn de la quantité initiale de Zn, et avec un débit d'alimentation surfacique maximal de 50 kg/mn par m de surface de bain. Ce procédé ne requiert par de technologies compliquées et permet de conserver le degré de pureté élevé du SiCl4 jusqu'à l'obtention du produit final, étant donné que le seul réactif est Zn, qui peut être obtenu à des degrés de pureté très élevés et recyclé en continu.
PCT/EP2008/003276 2007-05-25 2008-04-24 Procédé économique de production de si par réduction de sicl4 avec du zn liquide WO2008145236A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP07010409 2007-05-25
EP07010409.6 2007-05-25
US92477607P 2007-05-31 2007-05-31
US60/924,776 2007-05-31

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WO2008145236A1 true WO2008145236A1 (fr) 2008-12-04

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011079485A1 (fr) * 2009-12-31 2011-07-07 江苏中能硅业科技发展有限公司 Procédé de production et appareil de production de l'élément silicium
CN107055545A (zh) * 2016-12-09 2017-08-18 永平县泰达废渣开发利用有限公司 一种利用硅粉进行熔炼生产硅锭的工艺
CN110371983A (zh) * 2019-06-28 2019-10-25 陕西宝德赛肯光电材料有限公司 用真空中频感应炉冶炼高纯工业硅的方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20100118258A (ko) * 2009-04-28 2010-11-05 다우어드밴스드디스플레이머티리얼 유한회사 신규한 유기 발광 화합물 및 이를 채용하고 있는 유기 전계 발광 소자

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1111925A (ja) * 1997-06-25 1999-01-19 Sumitomo Metal Ind Ltd 多結晶シリコンおよび塩化亜鉛の製造方法
JPH1192130A (ja) * 1997-09-11 1999-04-06 Sumitomo Sitix Amagasaki:Kk 高純度シリコンの製造方法
WO2006100114A1 (fr) * 2005-03-24 2006-09-28 Umicore Procede de fabrication de si par reduction de sicu a l’aide de zn liquide
WO2007013644A1 (fr) * 2005-07-28 2007-02-01 Sumitomo Chemical Company, Limited Procédé servant à produire du silicium polycristallin
JP2007055891A (ja) * 2005-07-28 2007-03-08 Sumitomo Chemical Co Ltd 多結晶シリコンの製造方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1111925A (ja) * 1997-06-25 1999-01-19 Sumitomo Metal Ind Ltd 多結晶シリコンおよび塩化亜鉛の製造方法
JPH1192130A (ja) * 1997-09-11 1999-04-06 Sumitomo Sitix Amagasaki:Kk 高純度シリコンの製造方法
WO2006100114A1 (fr) * 2005-03-24 2006-09-28 Umicore Procede de fabrication de si par reduction de sicu a l’aide de zn liquide
WO2007013644A1 (fr) * 2005-07-28 2007-02-01 Sumitomo Chemical Company, Limited Procédé servant à produire du silicium polycristallin
JP2007055891A (ja) * 2005-07-28 2007-03-08 Sumitomo Chemical Co Ltd 多結晶シリコンの製造方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Week 200719, Derwent World Patents Index; AN 2007-192504, XP002455076 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011079485A1 (fr) * 2009-12-31 2011-07-07 江苏中能硅业科技发展有限公司 Procédé de production et appareil de production de l'élément silicium
CN107055545A (zh) * 2016-12-09 2017-08-18 永平县泰达废渣开发利用有限公司 一种利用硅粉进行熔炼生产硅锭的工艺
CN107055545B (zh) * 2016-12-09 2019-01-25 成都斯力康科技股份有限公司 一种利用硅粉进行熔炼生产硅锭的工艺
CN110371983A (zh) * 2019-06-28 2019-10-25 陕西宝德赛肯光电材料有限公司 用真空中频感应炉冶炼高纯工业硅的方法

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Publication number Publication date
TW200909349A (en) 2009-03-01

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