WO2012163534A1 - Matériaux de départ pour la production d'une charge de silicium pour applications solaires - Google Patents

Matériaux de départ pour la production d'une charge de silicium pour applications solaires Download PDF

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Publication number
WO2012163534A1
WO2012163534A1 PCT/EP2012/002311 EP2012002311W WO2012163534A1 WO 2012163534 A1 WO2012163534 A1 WO 2012163534A1 EP 2012002311 W EP2012002311 W EP 2012002311W WO 2012163534 A1 WO2012163534 A1 WO 2012163534A1
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Prior art keywords
ppm
ppt
preferred
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quartz
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PCT/EP2012/002311
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English (en)
Inventor
Lars Nygaard
Birger Andresen
Stein Christiansen
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Evonik Solar Norge As
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Priority claimed from EP11168720A external-priority patent/EP2530051A1/fr
Priority claimed from EP11168722A external-priority patent/EP2530050A1/fr
Application filed by Evonik Solar Norge As filed Critical Evonik Solar Norge As
Priority to TW101119766A priority Critical patent/TW201319338A/zh
Publication of WO2012163534A1 publication Critical patent/WO2012163534A1/fr

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    • 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
    • C01B33/023—Preparation by reduction of silica or free silica-containing material
    • C01B33/025—Preparation by reduction of silica or free silica-containing material with carbon or a solid carbonaceous material, i.e. carbo-thermal process
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/90—Carbides
    • C01B32/914—Carbides of single elements
    • C01B32/956—Silicon carbide
    • C01B32/963—Preparation from compounds containing silicon
    • C01B32/97—Preparation from SiO or SiO2

Definitions

  • the present disclosure relates to the field of production of silicon to be used as feedstock for production of solar cell wafers. In particular, it relates to the careful selection and preparation of starting materials for such production.
  • a physical purification method involving refining semi-pure liquid silicon with slag and gas followed by solidification.
  • the solid product is crushed and Fe, Al, Ca and Ti are leached out.
  • the product is then re-melted and subjected to directional solidification. This method is used by the Elkem company.
  • pure quartz is subjected to carbothermic reduction to obtain a silicon liquid, which may be treated by the following steps; gas refining, temperature adjustment, settling, filtering, skimming and directional solidification.
  • a challenge using this method is to produce a silicon product of sufficient purity.
  • the inventors have realized that a method based on a carbothermic reduction of quartz followed by refining in the liquid state is a promising alternative for the production of solar grade silicon. Compared to the physical purification method described above, fewer impurities are removed after the carbothermic reduction in this method. Instead, the inventors have chosen to use starting materials of higher purity. Thus, a silicon product having the characteristics demanded by the solar cell producers may be obtained by a few relatively uncomplicated and energy-efficient refining steps in the liquid state following the carbothermic reduction.
  • a carbon material such as carbon black
  • Some of the starting materials are used in such small particle sizes in order to reach the required purity, that they are preferably agglomerated by pelletizing or briquetting to avoid significant losses when charged to the reduction furnace.
  • the silica or quartz contain 0.5 ppm (w/w) or less boron, preferred 0,1 ppm (w/w) boron and 1 ppm (w/w) or less such as 0.5 ppm (w/w) phosphorous, with a carbon material, such as carbon black, containing 0.5 ppm (w/w) or less boron and 1.0 ppm (w/w) or less phosphorus to produce a silicon carbide product containing 1.5 ppm (w/w) or less boron and 3.0 ppm (w/w) or less phosphorus;
  • compositions comprising the quartz product and the silicon carbide product as defined above, characterized in that the composition is agglomerated.
  • Preferred compositions are pelletized.
  • a carbon material such as carbon black, containing 0.5 ppm (w/w) or less boron and 1.0 ppm (w/w) or less phosphorus to produce a silicon carbide product containing 1.5 ppm (w/w) or less boron and 3.0 ppm (w/w) or less phosphorus;
  • Quartz is a natural occurring silicon dioxide and therefore a crystalline material, in particular highly crystalline > 80 % crystallinity, preferred up to > 99 % crystallinity, such as a-Quartz, ⁇ -Quartz, a-Tridymite, ⁇ -Tridymite, a-Cristobalite, ⁇ -Cristobalite, Moganite and/or Keatite. Due to their crystallinity they are very pure. Impurities may not be located in the crystal lattice.
  • the provided starting materials may be mixed to form a mixture.
  • the weight ratio of the quartz product to the silicon carbide product in such a mixture may be 1 -1.2:1 , such as 1.05-1.15:1 , such as about 1.1 :1 .
  • starting material particles coarser than 2-3 mm are preferably charged directly into the reduction furnace, finer sized particles are preferably used as a raw material in the silicon carbide process or agglomerated before the carbothermic reduction process.
  • the mixture may thus be agglomerated according to the second aspect presented below.
  • the agglomeration process may for example be pelletizing and/or briquetting.
  • boron (B) 0.5 ppm (w/w) to 0.0001 ppt (w/w) , particularly from 0.4 ppm (w/w) to 0.0001 ppt (w/w), preferred from 0.3 ppm (w/w) to 0.0001 ppt (w/w) or particularly preferred 0.35 ppm (w/w) to 10 ppb (w/w); and
  • gallium (Ga) 1 ppm particularly from 0.5 ppm to 0.0001 ppt (w/w), preferred from 0.1 ppm (w/w) to 0.0001 ppt (w/w), particularly preferred 1 ppb (w/w) to 0.0001 ppt (w/w),
  • Ni nickel
  • ppm nickel (Ni) 10 ppm (w/w), particularly from 5 ppm (w/w) to 0.0001 ppt (w/w), preferred from 3.5 ppm und 0.0001 ppt (w/w);
  • Ti titan (Ti) 2 ppm (w/w), particularly from 1.7 ppm (w/w) to 0.0001 ppt, preferred from 1.5 to 0.0001 ppt (w/w);
  • aluminium (Al) 30 ppm (w/w) or from 25 to 0.0001 ppt (w/w) , particularly from 22 ppm (w/w) to 0.0001 ppt (w/w), and
  • gallium (Ga) 1 ppm particularly from 0.5 ppm to 0.0001 ppt (w/w), preferred from 0.1 ppm (w/w) to 0.0001 ppt (w/w), particularly preferred 1 ppb (w/w) to 0.0001 ppt (w/w),
  • Ni nickel
  • ppm nickel (Ni) 10 ppm (w/w), particularly from 5 ppm (w/w) to 0.0001 ppt (w/w), preferred from 3.5 ppm und 0.0001 ppt (w/w);
  • Ti titan (Ti) 2 ppm (w/w), particularly from 1.7 ppm (w/w) to 0.0001 ppt, preferred from 1.5 to 0.0001 ppt (w/w);
  • the reduction agent, carbon may not only be provided as silicon carbide in the carbothermic reduction process. Some of the carbon may also be provided in unreacted form, i.e. as the carbon material described above. Thus, in one embodiment, carbon material of the same quality as that of step c) may be provided as an additional starting material, e.g. as part of agglomerates.
  • the total carbon/oxygen ratio by weight in the starting materials/mixture may for example be equal to or less than 0.75.
  • the starting materials/mixture may be subjected to heating in a carbothermic reduction reaction to produce a liquid silicon product.
  • the starting materials/mixture may be heated to at least 1800 °C, such as to about 2000 °C.
  • the method step c) being performed in a furnace body, said body comprising an inner lining, characterized in that inner said lining comprises:
  • a binding agent or a binding agent such as a resin, e.g. a synthetic resin
  • the first and second starting materials for a carbothermic reduction process being supplied to a reduction furnace body, said body comprising an inner lining comprises:
  • a silicon product containing 1 .5 ppm (w/w) or less boron and 3.0 ppm (w/w) or less phosphorus, in particular a silicon nitride and optionally silicon and c) 0.1 -5 % (w/w) of a reaction product of a binding agent or a binding agent, such as a resin, e.g. a synthetic resin; and, in particular the reaction product of a binding agent, and wherein the sum of this composition is 100 % (w/w).
  • the starting material being in particular reacted in the reaction furnace body to form silicon melt.
  • the first and second starting materials for a carbothermic reduction process being supplied to a reduction furnace body, wherein the reduction furnace body comprising at least a first and a second electrode, at least one of the electrodes comprises:
  • a silicon product containing 1 .5 ppm (w/w) or less boron and 3.0 ppm (w/w) or less phosphorus, in particular a silicon nitride and optionally silicon and; c) 0.1 -5 % (w/w) of a reaction product of a binding agent or a binding agent, such as a resin, e.g. a synthetic resin; in particular the reaction product of the binding agent; and, wherein the sum of this composition is 100 % (w/w).
  • a binding agent or a binding agent such as a resin, e.g. a synthetic resin
  • binding agent may be selected from a resin selected from synthetic phenol-formaldehyde resins or be selected from form a carbohydrate, such as a saccharide.
  • the carbohydrates may be selected from saccharides, disaccharides, monosaccharides, cellulose, hydroxypropylmethylcellulose (HPMC), methyl- cellulose.in particular sucrose, lactose, mannitol, dectrin, dextrose, microcrystalline cellulose, cellulose ether, starch.
  • Preferred the binding agent comprise less than:
  • aluminium (Al) 30 ppm (w/w) or from 20 to 0.0001 ppt (w/w), particularly from 5 ppm (w/w) to 0.0001 ppt (w/w), and
  • boron (B) 1.0 ppm (w/w) to 0.0001 ppt (w/w), particularly from 0.5 ppm (w/w) to 0.0001 ppt (w/w), preferred from 0.4 ppm (w/w) to 0.0001 ppt (w/w) or particularly preferred 0.35 ppm (w/w) to 10 ppb (w/w); and
  • gallium (Ga) 1 ppm particularly from 0.5 ppm to 0.0001 ppt (w/w), preferred from 0.1 ppm (w/w) to 0.0001 ppt (w/w), particularly preferred 1 ppb (w/w) to 0.0001 ppt (w/w),
  • Ni nickel
  • ppm nickel (Ni) 10 ppm (w/w), particularly from 5 ppm (w/w) to 0.0001 ppt (w/w), preferred from 3.5 ppm und 0.0001 ppt (w/w);
  • Ti titan (Ti) 2 ppm (w/w), particularly from 1.7 ppm (w/w) to 0.0001 ppt, preferred from 1.5 to 0.0001 ppt (w/w);
  • furnace body and/or electrode comprise:
  • aluminium (Al) 30 ppm (w/w) or from 25 to 0.0001 ppt (w/w), particularly from 22 ppm (w/w) to 0.0001 ppt (w/w), and
  • boron (B) 1.0 ppm (w/w) to 0.0001 ppt (w/w) , particularly from 0.5 ppm (w/w) to 0.0001 ppt (w/w), preferred from 0.4 ppm (w/w) to 0.0001 ppt (w/w) or particularly preferred 0.35 ppm (w/w) to 10 ppb (w/w); and
  • gallium (Ga) 1 ppm particularly from 0.5 ppm to 0.0001 ppt (w/w), preferred from 0.1 ppm (w/w) to 0.0001 ppt (w/w), particularly preferred 1 ppb (w/w) to 0.0001 ppt (w/w),
  • Ti titan (Ti) 2 ppm (w/w), particularly from 1 .7 ppm (w/w) to 0.0001 ppt, preferred from 1.5 to 0.0001 ppt (w/w);
  • the liquid silicon may subsequently be filtered (e.g. to remove remaining carbides) and/or refined by gas extraction, e.g. with chlorine gas, optionally combined with an inert gas, such as argon.
  • gas extraction e.g. with chlorine gas, optionally combined with an inert gas, such as argon.
  • Such extraction removes aluminium (Al), calcium (Ca) and other elements capable of forming salts or slag with the chlorine gas under the prevailing conditions.
  • Boron (B) and phosphorus (P) are not such elements.
  • the gas extraction with chlorine or of a chlorine argon mixture can be done by supplying the gas or gas mixture through or from the bottom of a graphite crucible or a silicon dioxide comprising crucible.
  • the gas extraction may be followed by refinement by directional solidification.
  • silicon residues may be obtained.
  • the solid silicon ingot obtained from the directional solidification is normally cut to remove a layer from each side because the outer layers normally comprise higher levels of contaminants. Kerfs or swarf from wafer sawing are other examples of silicon residues generated during the downstream processing.
  • the silicon residues may be recycled.
  • recycled silicon material is provided as an additional starting material.
  • the bottom layers and lateral layers cut from the ingots as well as the kerfs/swarf are thus examples of such an additional starting material.
  • the removed top layer may however comprise such high levels of contaminants that it is inappropriate to reuse it the carbothermic reduction reaction.
  • the removed layers and kerfs/swarf may be cleaned before being recycled, e.g. by one or more dressing methods.
  • Step a) of the method may for example comprise at least one of crushing, screening, milling, optical sorting, magnet separation, gravimetric separation, flotation and acidic treatment.
  • at least two, such as at least three, such as at least four, such as at least five, such as at least six, such as at least seven, of the sub- steps are performed. Also, all of the sub-steps may be performed.
  • step a) may comprise the following steps for preparation of the quartz/quarts required 1 . selective mined in the quarry based upon pre investigation of the deposit, 2. crushing down the selected quarts (23mm - 4mm), 3. optical sorting of the selected quarts fraction based upon differences in colour and corresponding chemical analyses, such as UV-A, UV-Vis and/or IR-spectrum based sorting; 4. washing of the selected quarts.
  • the following steps may be performed: 1. crushing down the quarts after optical sorting and washing (-400 micron), 2. flotation of the quarts powder to remove minerals from the quarts, 3. acid washing of the quartz powder to remove trace elements like Fe and Al, 4. washing in pure water after acid washing.
  • the purpose of the crushing and milling is to obtain smaller pieces of the quartz and thus expose impurities.
  • the quartz is however already crushed to appropriately sized pieces when delivered to a site where the above method is carried out.
  • the quartz may be split into different fractions by the substep of screening, and over-sized particles may be returned to the substep of crushing and/or the substep of milling.
  • the screening may also separate different size fractions to dedicated process steps.
  • visible impurities may be detected. Some impurities may for example be detected as dark spots in the quartz or discolored particles and the pieces containing such dark spots or the discolored particles may be removed.
  • a transport arrangement such as a conveyor belt.
  • a piece having an impurity it may be removed from the transport arrangement, e.g. by blowing compressed air at the piece or by a mechanical arrangement.
  • the removed impure particles may be further crushed and optically sorted again to increase the quartz yield.
  • a magnet preferably an electric magnet
  • a magnet for separating magnetic material, such as iron-containing minerals.
  • pieces of crushed quartz e.g. from the sub-step of crushing or the substep of optical sorting, may be transported through a device for magnet separation on a transport arrangement, such as a conveyor belt.
  • Pieces containing a sufficient amount of iron- containing minerals are removed from the transport arrangement by a force generated by a magnetic field.
  • Strongly magnetic minerals, such as magnetite, franklinite, and pyrrhotite can be removed by low-intensity magnetic separators.
  • a high-intensity device can also separate minerals with weaker magnetic properties, such as oxide iron ores, e.g. limonite and siderite, as well as iron-bearing manganese, titanium, and tungsten ores and iron-bearing silicates.
  • a mineral with a density deviating from that of quartz can be removed, for example by immersing the crushed quartz in a liquid that has a density in-between those for the quartz and the mineral.
  • some acid soluble minerals can be removed after being dissolved in a solution of an acid like sulfuric acid, hydrochloride acid, nitric acid and/or hydrofluoric acid.
  • the selection of acid(s), concentration, temperature and processing time are adapted for each specific combination of minerals it is necessary to remove.
  • the low levels of contaminants in the quartz product are the result of the selected quartz raw material and the selected preparation step(s).
  • Step a) may require milling of the quartz to fine fractions to make it possible to remove unwanted minerals as liberated particles. Quartz and other materials finer than 2 or 3 mm in average diameter is preferably agglomerated before being charged to the reduction furnace or used as a raw material in the silicon carbide process because otherwise they may blow out of the furnace with the process gases. Step a) may also give quartz pebbles having an average diameter of 3-25 mm that are clean enough to be charged directly into the reduction furnace. Particles coarser than 25 mm may be heated too slowly. Thus, they may not be sufficiently preheated when they reach a high-temperature zone under the electrode in the reduction furnace and as a result, the silicon yield in the process may be reduced.
  • the quartz product obtained from step a) contains 0.5 ppm (w/w) or less boron and 1 .0 ppm (w/w) or less phosphorus. Preferably, it contains 0.25 ppm (w/w) or less boron and 0.5 ppm (w/w) or less phosphorus.
  • the quartz product obtained from step a) may for example contain 300 ppm (w/w) or less, such as 250 ppm (w/w) or less, aluminium and/or 60 ppm (w/w) or less, such as 40 ppm (w/w) or less, iron.
  • the sum of all metal impurities in the quartz product obtained from step a) is 500 ppm (w/w) or less, such as 400 ppm (w/w) or less, such as 300 ppm (w/w) or less, preferred equal to less than 200 ppm (w/w) to 0.01 ppt (w/w).
  • the sum of all metal impurities are defined as the aforementioned metals, in particular comprise all metals that can be analytically detected, and are different from silicon.
  • the inventors have realized that carbon black derived from natural gas is best suited for step c). This is because such carbon black may be obtained at a economically viable price and has a high purity.
  • the carbon material used in step c) contains 0.5 ppm (w/w) or less boron, 1.0 ppm (w/w) or less phosphorus. Preferably it contains 0.30 ppm (w/w) or less boron, 0.6 ppm (w/w) or less phosphorus, 5 ppm (w/w) or less aluminium and/or 2 ppm (w/w) or less iron, preferred 1 ppm (w/w) or less than 0.1 ppm (w/w) to 0.0001 ppt (w/w). In one embodiment, it contains 0.20 ppm (w/w) or less boron and 0.3 ppm (w/w) or less phosphorus.
  • the carbon material may be used both in agglomerates as a starting material for the carbothermic reduction process and for the production of pure silicon carbide.
  • the silicon carbide product obtained from step c) contains 1.5 ppm (w/w) or less boron and 3.0 ppm (w/w) or less phosphorus.
  • it contains 1.0 ppm (w/w) or less, such as 0.75 ppm (w/w) or less, such as 0.5 ppm (w/w) or less, boron.
  • it preferably contains 2.0 ppm (w/w) or less, such as 1.2 ppm (w/w) or less, such as 0.8 ppm (w/w) or less, phosphorus.
  • the silicon carbide may be produced in a rotating plasma heated furnace, such as the one developed at SINTEF in Trondheim, Norway. The use of the normal Acheson silicon carbide process is less preferred as it may contaminate the silicon carbide, but it is proved that a modified Acheson process may give a silicon carbide of sufficient purity.
  • the average diameter of the silicon carbide provided as a starting material, or any agglomerate of which it is part, is preferably 2-25 mm for the same reasons as discussed above. Most preferred is an average diameter of 10-15 mm.
  • the starting materials for the carbothermic reduction may be premixed in appropriate proportions.
  • the step of charging the starting materials may be simplified.
  • such a starting materials mixture may provide for easier handling and more efficient logistics, in particular if they are agglomerated, e.g. pelletized.
  • an agglomerated, such as pelletized composition comprising the quartz product and the silicon carbide product according to the first aspect.
  • the agglomerated composition may be referred to as agglomerates and the pelletized composition may be referred to as pellets.
  • the weight ratio of the quartz product to the silicon carbide product may for example be 1.0-1.2:1 .0, such as 1.05-1 .15, such as about 1.1 :1 .0.
  • the agglomerated composition of the second aspect may for example comprise a binder.
  • the binder of the present disclosure may for example be carbohydrates composed of carbon, oxygen and hydrogen. Examples of such carbohydrates are purified mono-, di- or polysaccharides of biological origin.
  • binders Most oxygen and hydrogen in the carbohydrate binders will react to form gaseous compounds before the carbothermic reduction takes place while some of the carbon normally will take part in the reduction process.
  • Other binders composed of the same three elements, such as alcohols and other hydrocarbons may provide the same benefit. Resins may also be used as the binder.
  • Water and/or silica fume may be added to the composition to aid the aggregation and improve the strength of the agglomerates.
  • the water is preferably purified, such as de-ionized, to prevent contamination.
  • the water normally separates from the agglomerate before the reduction process starts.
  • the silica fume may for example be filtered out of flue gases from the carbothermic reduction process (see figure 1 , 117).
  • the silica fume fills the spaces between the individual pieces/particles in the mix that is agglomerated.
  • the silica fume may have a surface area of at least 5000 m 2 /kg, such as at least 10000 m 2 /kg.
  • the surface may be measured by a nitrogen adsorption technique.
  • the binder may for example constitute 1-10 % (w/w), such as 2-10 % (w/w), such as 4-8 % (w/w) of the silica agglomerates.
  • the water may for example constitute 2-10 % (w/w), such as 4-8 % (w/w) of the silica agglomerates.
  • the silica fume may for example constitute 1-20 %, such as 1-10 % (w/w), such as 2-8 % (w/w) or 3-7 % (w/w), of the agglomerates. Wherein the sum of all components in the composition is 100 % (w/w).
  • the average diameter of the agglomerates of the present disclosure may for example be 10-20 mm, such as 10-15 mm.
  • a functional arrangement for drying and hardening of agglomerates may be a part of an agglomeration plant.
  • the individual solid components may for example be provided in the agglomerated composition as powders having an average particle sizes below 0.3 mm.
  • the agglomerates of the present disclosure may for example be pellets or briquettes.
  • Figure 1 shows an embodiment of a system for producing solar grade silicon.
  • a natural quartz having low levels of contaminants, in particular boron and phosphorus, is selected.
  • the selected natural quartz 101 is added to a quartz processing plant 102, in which the natural quartz undergoes one or more of the steps of crushing, screening, milling, optical sorting, magnet separation, gravimetric separation, flotation and acidic treatment.
  • Optical sorting comprises optical detection of impurities in the natural quartz.
  • the impurities may be visible as dark spots.
  • the optical sorting may comprise the removal of the pieces of material on which such spots have been detected by means of compressed air. That is, such pieces may be blown off a transport belt, such as a conveyor belt or the like.
  • the acidic treatment may comprise dissolving and removing impurities.
  • the magnet separation comprises the removal of pieces of material containing magnetic minerals.
  • quartz 103 from the quartz processing plant 102 is added to a silicon carbide production plant 105, to which carbon black 104 of high purity is also added.
  • carbon black may for example be derived from natural gas.
  • the same type of processed quartz 106 from the quartz processing plant 102 is added, together with recycled silicon metal 107 from downstream positions in the system and silicon carbide 108 from the silicon carbide production plant 105, to an arrangement for weighing and mixing 109.
  • the appropriately mixed material is then added to a reduction furnace/reaction vessel 1 11 by means of charging equipment 110.
  • powders of the silicon carbide 108 and the processed quartz 106 may be mixed to form a composition that is pelletized and added to the reduction furnace/reaction vessel 11 1 .
  • Additives aiding the aggregation of the components of the pellets may also be used in such a composition.
  • the weight ratio of quartz to silicon carbide in the material added to the reduction furnace 1 1 1 is about 1.1 :1 .
  • a smoke hood 112 is arranged above the reduction furnace 111 to collect gases formed during the reduction process.
  • said furnace body comprise: (i) 80 to 95 % (w/w) of a silicon carbide product containing 1.5 ppm (w/w) or less boron and 3.0 ppm (w/w) or less phosphorus;
  • a reaction product of a binding such as a resin, e.g. a synthetic resin and/or a carbohydrate; and, wherein the sum of this composition is 100 % (w/w).
  • the collected gases are routed, via a duct 116, to a device for flue gas filtering and dust treatment 117.
  • the device 117 comprises a chimney 118 through which the purified gases are expelled.
  • Silica fume may be separated from the device for flue gas filtering and dust treatment 117 and added to the composition to be pelletized to facilitate aggregation.
  • An electrode 113 preferably composed of graphite or an electrode that comprise: (i) 80 to 95 % (w/w) of a silicon carbide product containing 1.5 ppm (w/w) or less boron and 3.0 ppm (w/w) or less phosphorus; (ii) 5 to 20 % (w/w) of a silicon product containing silicon nitride and optionally silicon containing 1.5 ppm (w/w) or less boron and 3.0 ppm (w/w) or less phosphorus; and (iii) 0.1 to 5 (w/w) of a reaction product of a binding, such as a resin, e.g.
  • a second electrode 1 14 or set of electrodes also preferably composed of graphite or of the
  • Electrode(s) 113 and electrode 114 are connected to a power source 1 15, such as a DC or AC power source, for generating an electric arc that heats the carbothermic reduction process.
  • the silicon melt formed in the reduction furnace 114 is tapped through a tapping zone of the reduction furnace 114 into a ladle 119, which has been preheated by a ladle preheating device 135.
  • an inert gas such as argon, may be bubbled through the ladle to stir the silicon melt therein. Material may be continuously added to the reduction furnace 111.
  • the filled ladle 119 is moved to an arrangement for chlorine refining, during which chlorine gas, optionally together with an inert gas, such as argon, is bubbled through the liquid silicon in the ladle 1 19 to react with impurities, such as aluminium or calcium, to form chloride salts, e.g. AICI 3 and CaCI 2 .
  • impurities such as aluminium or calcium
  • chloride salts e.g. AICI 3 and CaCI 2
  • the arrangement for chlorine refining preferably comprises means tor heating 120, such as inductive heating, of the liquid silicon. This is to ensure that the silicon remains liquid during the process. If the chlorine refining is done in the holding furnace the heating is done by induction.
  • the refining may also be done in a ladle.
  • the ladle may either be pre-heated by heating elements or by using induction.
  • the refined silicon melt is then, optionally after filtering, added to a preferably preheated crucible 122 on a device for directional solidification in filling position 123.
  • the refined silicon may also be stored in an induction furnace or holding furnace for some time before being added to the preheated crucible 122.
  • the device comprises a furnace 124 having heating elements 125.
  • the device for directional solidification is set to its processing position 126, in which the crucible 122 is placed in the furnace 124.
  • the crucible 122 is cooled from below to generate a bottom-up solidification, which results in a concentration of impurities in the top layer of the formed solid silicon ingot.
  • the crucible 122 is then removed from the ingot in a crucible removal step 127. This normally involves breaking the crucible 122 to release the ingot.
  • the ingot is then cut to remove the outermost layer of its sides and bottom as well as the impurities containing top layer in an ingot cutting step 128.
  • the ingot may then be subjected to the steps of etching and washing 129 packing 130 and storage 131 , before it is transported to a customer, which may re-crystallize the ingot and then cut it to wafers for the production of solar cell panels.
  • the ingot is cut into blocks/bricks before cleaning, packing and sending to customer.
  • All or some of the side and bottom layers removed in the ingot cutting step 128 are recycled to the process, preferably to the arrangement for weighing and mixing 109, after a step of milling, sandblasting and/or crushing 132.
  • the top layer from the ingot cutting step 128 is wasted to prevent accumulation of impurities in the system 100.
  • the milling, sandblasting and/or crushing step 132 also produces some waste.

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  • Silicon Compounds (AREA)

Abstract

Cette invention concerne un procédé de préparation d'un premier et d'un second matériau de départ pour un procédé de réduction carbothermique, comprenant les étapes suivantes : a) préparer un produit quartzique contenant 0,5 ppm (p/p) ou moins de bore et 1 ppm (p/p) ou moins de phosphore à partir d'un quartz naturel ; b) utiliser une partie dudit produit quartzique à titre de premier matériau de départ ; c) faire réagir une partie du produit quartzique avec un matériau carboné, tel que le noir de carbone, contenant 0,5 ppm (p/p) ou moins de bore et 0,4 ppm (p/p) ou moins de phosphore pour obtenir un produit de carbure de silicium contenant 1,5 ppm (p/p) ou moins de bore et 3,0 ppm (p/p) ou moins de phosphore ; d) utiliser ledit produit de carbure de silicium à titre de second matériau de départ. Une composition à l'état aggloméré comprenant le produit quartzique et le produit de carbure de silicium est également décrite.
PCT/EP2012/002311 2011-06-03 2012-05-31 Matériaux de départ pour la production d'une charge de silicium pour applications solaires WO2012163534A1 (fr)

Priority Applications (1)

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TW101119766A TW201319338A (zh) 2011-06-03 2012-06-01 用於製造太陽能級矽進料之起始材料

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EPEP11168722 2011-06-03
EPEP11168720 2011-06-03
EP11168720A EP2530051A1 (fr) 2011-06-03 2011-06-03 Corps de four de réduction
EP11168722A EP2530050A1 (fr) 2011-06-03 2011-06-03 Matériaux de départ pour la production de produit de départ en silicone à qualité solaire

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WO2012163534A1 true WO2012163534A1 (fr) 2012-12-06

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2749531A4 (fr) * 2011-08-24 2015-05-13 Taiheiyo Cement Corp Poudre de carbure de silicium et procédé pour produire celle-ci
CN114174217A (zh) * 2019-08-08 2022-03-11 施米德硅晶片科技有限责任公司 用于制备含硅材料的方法和装置

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GB2008559A (en) * 1977-09-09 1979-06-06 Goldblatt N Z Production of silicon
GB2150128A (en) * 1983-11-26 1985-06-26 Int Minerals & Chem Corp Production of silicon from raw quartz
EP0177894A2 (fr) * 1984-10-12 1986-04-16 SAMATEC-SOCIETA' ABRASIVI E MATERIALI CERAMICI S.p.A. Procédé de préparation de silicium métallique spécialement utilisé dans l'industrie photovoltaique
EP0243880A1 (fr) * 1986-04-29 1987-11-04 Dow Corning Corporation Carbure de silicium comme produit de départ pour la production de silicium
EP2036855A2 (fr) * 2007-09-14 2009-03-18 General Electric Company Système et procédé de production de silicone à qualité solaire
WO2009153151A1 (fr) * 2008-06-16 2009-12-23 N.E.D. Silicon S.P.A. Procédé de préparation d'un silicium de qualité métallurgique de haute pureté
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GB2008559A (en) * 1977-09-09 1979-06-06 Goldblatt N Z Production of silicon
GB2150128A (en) * 1983-11-26 1985-06-26 Int Minerals & Chem Corp Production of silicon from raw quartz
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EP2036855A2 (fr) * 2007-09-14 2009-03-18 General Electric Company Système et procédé de production de silicone à qualité solaire
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DE102008041334A1 (de) * 2008-08-19 2010-02-25 Evonik Degussa Gmbh Herstellung von Silizium durch Umsetzung von Siliziumoxid und Siliziumcarbid gegebenenfalls in Gegenwart einer zweiten Kohlenstoffquelle
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2749531A4 (fr) * 2011-08-24 2015-05-13 Taiheiyo Cement Corp Poudre de carbure de silicium et procédé pour produire celle-ci
CN114174217A (zh) * 2019-08-08 2022-03-11 施米德硅晶片科技有限责任公司 用于制备含硅材料的方法和装置

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