A kind of method of leading mixed gas into metal silicon solution
Technical field
The present invention relates to from (MG) silicon of metallurgical grade to remove impurity particularly phosphorus (P), boron (B), oxygen (O), carbon (C) to make the method for solar level (SG) silicon.This method is particularly related to and imports mixed gas in proportion in smelting process.
Background technology
In recent years, because to the energy/environmental problem, such as the consumption of the mineral fuel energy and showing great attention to of global warming issue, the feasible needs that can be used as the silicon of solar cell material increase sharply.Along with the fast development of photovoltaic industry, solar cell is higher than the development of polycrystalline silicon semiconductor to the rate of growth of polysilicon demand.The ultimate production of whole world solar cell in 1994 has only 69MW, and 2004 just near 1200MW, in short 10 years, just increased by 17 times.Scholarly forecast photovoltaic industry will become one of most important basic energy resource above nuclear power in first half 21st century.
Solar energy polycrystalline silicon mainly contains three sources at present, and the one, the fragment of production semiconductor integrated circuit silicon single crystal; The 2nd, the by-product of multichip semiconductor crystal, the i.e. material of residue end to end of single crystal rod; The 3rd, the solar energy polycrystalline silicon that the polycrystalline silicon semiconductor business men is produced with unnecessary production capacity.
In the world electronic-grade high-purity (>11N) mainstream technology of polycrystalline silicon raw material preparation is the Siemens Method and the chlorine hydrogen silicon (SiHCl that looses
3) reduction method and silane (SiH4) thermal decomposition method, countries in the world also have the improvement of use Siemens Method (being Russian method), silane thermal decomposition process, fluidized bed method, metallurgy method simultaneously, wherein improve Siemens Method and account for global output more than 80%.This method is selected technical grade silicon for use, through each step reaction purify back purity reach 11 " 9 " and above be the semiconductor grade polysilicon, and the purity of solar-grade polysilicon is just can meet the demands more than 6 " 9 ".The characteristics of improvement Siemens Method are that investment is huge, the technical requirements height, and environmental pollution is serious.But any method no matter is on average purified the power consumption of per kilogram polycrystalline silicon raw material all about 250~400 degree, high energy consumption, and the low output of high investment is the high major cause of polycrystalline silicon raw material cost, seriously restricts the universal use of solar cell.
The production capacity of solar energy polycrystalline silicon is subject to the production capacity of semiconductor grade polysilicon.Therefore, market in urgent need seek a kind of new, can mass production lower-cost high purity polycrystalline silicon method simultaneously.
For example, CN101122047 has announced a kind of method for manufacturing polycrystalline silicon used for solar battery, and the means that adopt silicon monoxide disproportionation, acid dipping separation and vacuum melting to combine are undertaken by following six steps: (1) uses chemical pure industrial silicon and height
Chinese patent application 200410003090.6 discloses a kind of method and apparatus that is prepared hyperpure silicon by Pure Silicon Metal, by to raw material crushing, impurity chemical combination, three sequential steps principles of crystallization purifying, adopt following working procedures combination operation: Pure Silicon Metal is broken for fine particle to increase surface-area; The way of difference aerating oxygen, adding hydrochloric acid, feeding chlorine is carried out combination reaction to the impurity in the silicon in silicon grain, so that the impurity in the silicon generates oxide compound or muriate; Utilize high temperature the muriate evaporative removal of low sublimation temperature, utilize the eutectoid point characteristic of the little and oxide compound of individual element segregation coefficient again, with middle solidification technology or directional solidification technique further the Impurity removal in the silicon.By above-mentioned technology and the device impurity in the silica removal of making a return journey, be the Pure Silicon Metal purifying hyperpure silicon goods.
Chinese patent application 200710052244.4 discloses a kind of low energy consumption purifying and preparation method for polycrystalline silicon raw material, at first will pulverize through the Pure Silicon Metal that reduction is handled, use pickling such as chloroazotic acid, hydrofluoric acid again, send into the continuous induction melting furnace fusion after the pickling, temperature forms horizontal temperature gradient and vertical temperature gradient in the continuous induction melting furnace, and the silicon materials that come out from continuous induction melting furnace enter zone melting furnace, makes and forms interval thermograde in the zone melting furnace, the utilization heat method that becomes is got rid of the silicon quarrel, can obtain the silicon of 99.9999% purity.
Adopt above method, Pure Silicon Metal is after elementary smelting, after remelting, directional freeze, sorting, can reach silicone content greater than 99.999% purity, but the solar-grade high-purity silicon material is greater than 99.999% except silicone content, content that also must all the other impurity of control.In the contained impurity of the silicon that is used for solar cell, the content of some elements, particularly phosphorus and boron must be by strict control, its reason be P, B foreign matter content what can determine the conduction type and the doping effect of silicon materials.Therefore, existing many research is used for removing P, the B impurity of Pure Silicon Metal.
For example, Chinese patent CN101054178 discloses a kind of boron removal method of polysilicon, the steps include: polysilicon block is pulverized, ball milling, screen silica flour; Silica flour with the organic solvent processing of deoiling, and is removed iron powder in the silica flour; The silica flour of the deironing of deoiling is put in the container, again container is put in the High Temperature Furnaces Heating Apparatus, carry out wet-oxygen oxidation, again cooling; The silica flour of cooling back taking-up is put into hydrofluoric acid solution corrode, remove the zone of oxidation of sample surfaces; Water cleans silica flour to effusive water repeatedly and shows till the neutrality, with the silica flour drying of anhydrating, target product.
Chinese patent application 03803266.X provides a kind of method that can remove the B element in the silicon.According to this method, the raw silicon and the slag that contain boron are melted, and make the axle rotation stir molten silicon thus by rotation/driving mechanism.Slag is scattered in the molten silicon, quickens boron thus and removes reaction.Can further effectively utilize the SiO that contains at least 45 quality %
2Slag, or will be blown in the molten silicon with introducing gas as purifying reaction with water vapor blended gas.
Chinese patent application 200480035884.9 discloses a kind of impurity of removing to make the method for solar energy level silicon from metallurgical grade silicon, this method may further comprise the steps: (1), the metallurgical grade silicon that will contain metallic impurity and nonmetallic impurity grind to form the about 5000 microns silicon grain powder of diameter, (2), under the solid-state situation of silica flour maintenance, it is heated to the temperature that is lower than the silicon fusing point under vacuum, (3), the silica flour after will heating keep sufficiently long for some time to remove at least a metal or nonmetallic impurity under described temperature.This method can be in solid-state rather than it handled during melting condition at metallurgical grade silicon, and the impurity of removal mainly is phosphorus.
Above method can only be removed wherein a kind of main impurity, and can not remove titanium (Ti, 1725 ℃ of fusing points), boron (B, 2300 ℃ of fusing points), carbon (C, 3550 ℃ of fusing points) in the Pure Silicon Metal simultaneously.
Its temperature generally is controlled at about 1600 ℃ in the Pure Silicon Metal purification process, the problem that is run in purification process is that some the high-melting-point materials in the Pure Silicon Metal can not fuse, be difficult to discharge and reject, so that can not reach the purpose of purification, so seeking the remelting purification that a kind of new purifying technique is realized Pure Silicon Metal for a long time always.
In the fusion process of Pure Silicon Metal,, also must import gas with various for improving the metal quality.Traditional gas reaction method is to import pure gas in the smelting furnace step by step, it is blown in the molten metal, make it in the Pure Silicon Metal liquation, produce a kind of agitaion, obtain balance so that smelt the malconformation of component and temperature, to reach the effect of separating impurity.Existing gas imports top blast or the bottom blowing boundling gas mode of all adopting, and concrete general method is the straight-through gas duct of 3mm for adopting one or more diameter, imports in the melting container under certain pressure.For example, Chinese invention patent CN1066888 provides a kind of air supply element for metallurgical furnace bottom and manufacture method, and this method mainly is applicable to gas bottom blowing and supplying systems such as various steel melting furnaces, refining furnace and ladle.Its major technique feature is that difform stainless steel tube is embedded in the refractory materials tile of trough of belt.And with refractory mortar the slit of remainder is filled up, then several pieces refractory materials tiles are bonded to one with binding agent.The sectional dimension of gas supply element stainless steel tube: circular Φ 0.1~3.0mm, square (0.1~3) * (0.1~3) mm, rectangle (0.2~2) * [0.3~(brick is wide by-30)] mm.Be to guarantee gas communication, conduit is not blocked, and it goes out atmospheric pressure must be bigger, so gas produces fierce boiling after importing liquid, causes the waste of a large amount of gases, increases cost, and conduit the suck-back phenomenon easily takes place and stops up.Under the situation that pore stops up, for once and must change its work-ing life, wastes energy and increase workload and production cost.
For improving gas supply element, improve smelting efficiency, China utility model ZL93218398.0 provide a kind of metallurgical furnace bottom blowing gas supply element, it is characterized in that this gas supply element is a composite structure, and it is made up of top, body, bottom, air flue, air chamber and airway.Top, body and bottom adopt magnesia ventilation property stamp mass, magnesia carbon refractory and full magnesia material to form respectively.And magnesia ventilation property stamp mass is a particulate state.This method has adopted the magnesia knotting bed of material of particulate state, avoided airway directly to contact with liquation, but these particles are loose distributed filling in the product, particle can be shifted mutually, the space skewness, therefore after gas enters liquation, still be difficult to avoid fierce boiling and the gas waste that causes, also can't avoid conduit suck-back phenomenon.
Chinese invention patent CN1168416 discloses a kind of bottom for metallurgical vessel air feed with diffuse type ventilated element and manufacture method thereof, is applicable to converter, electric furnace and various refining furnace.It is made up of refractory materials core and shell, and the composition of its main refractory materials (weight %) is MgO:80~95%, Al
2O
30.5~5%, grain graininess<4mm of used MgO, production method is: according to chemical composition scope mixes refractory materials core batching, the top of the ventilated element shell air chamber of packing into, high-pressure molding, low-temperature bake 20~150 hours again.This method has overcome loose particles bonded shortcoming in the preceding method, but the employed particle of this method is bigger, and its diameter is the mm level, therefore is lack of communication evenly; Gap between particles is bigger, under the situation that the gas supply is interrupted suddenly, still is difficult to avoid the suck-back phenomenon.Liquation easily enters in the space and stops up.
After existing metallic silicon smelting is come out of the stove all be splendid attire in block has the insulated tank of refractory materials, contain silicon bucket bottom and be equipped with single or multiple pore entrance holes, the aperture is generally more than 3mm.Gas enters melted silicon and shows as the boundling state, and whole air guide process can not be intermittently, otherwise melted silicon easily flows backwards and stop up the air outlet, and for once just must change, and will bake hot vessel again work-ing life, wastes energy and increases workload and production cost.And the saturation vapour pressure of P, B impurity element and segregation coefficient and silicon are very approaching, therefore are difficult to remove P, B impurity in the metal.Pure gas imports the purpose that the P in the silicon liquid, B, O, C is difficult to react thereby be difficult to reach reject.
Generally speaking, the purification of metallurgical grade silicon comprises removal phosphorus (P), boron (B), oxygen (O), carbon (C) and various hybrid metal.Although in the past 30 years neutral and alkalis a lot of effort, but still do not have the method for commercial-scale economy can be used for metallurgical grade silicon risen to be fit to the silicon that solar level is used.Some problems of implementing the commercial size method comprise that mainly the mode with economy removes boron and the phosphorus in the metallurgical grade silicon.So the removal of P, B impurity is the main technical barrier of purifying metal silicon.Because the shortcoming that existing ventilation introduction method exists is expected new gas introduction method in the art always.
Summary of the invention
The object of the present invention is to provide the method in a kind of mixed gas importing silicon liquid, this method had both been eliminated in the traditional method silicon liquid and has easily been flow backwards and block the shortcoming of airway, eliminate traditional pure gas again and imported P, B, O, the C impurity that is difficult to eliminate in the silicon liquid, this method can make hydrogen, oxygen, enter silicon liquid simultaneously in proportion, produce fierce reaction with P, B, O, C in the silicon liquid, produce P, B, O, the C phenomenon that gasify, discharge the purpose that reaches these four kinds of constituent contents in the reduction silicon liquid with gas.
The technical solution used in the present invention is as follows:
1, the making communicating pores is young in the pneumatic outlet of 10 μ m;
2, respectively closely be arranged in as a whole according to the air guide kind pneumatic outlet;
3, pneumatic outlet is placed in the bottom of reaction vessel;
4, will fuse to 1800 ℃ melted silicon and pour in the container that the gas gatherer is housed;
5, gas with various is imported respectively in the melted silicon, its ratio is oxygen 50%, hydrogen 25%, water vapour 25%, gaseous tension 3KG.
6, each end of operation reject wall of container skull afterreaction container can continue to use.
Communicating pores of the present invention is young to be made in the following technical scheme of the pneumatic outlet employing of 10 μ m:
1, selects resistant to elevated temperatures material high pure metal oxide compound;
2, the high pure metal oxide compound is ground to the particle of 75~10 μ m sizes;
3, in metal oxide particle, add alkaline liquid, and stir;
4, the high pure metal oxide particle that stirs is packed into forming mould;
5, mould is warmed to 750~850 ℃, places under the above press device of 500T, suppress 3~6 hours, die sinking taking-up product when treating that temperature is reduced to 50 ℃;
6, product was positioned over the lucifuge place 5~12 days, allows alkaline liquid continue volatilization;
7, product is delivered to carried out sintering in the High Temperature Furnaces Heating Apparatus, be warming up to 1000 ℃, be incubated 48 hours, cool to 200 ℃ of taking-ups with 1~5 ℃ speed per hour again with 1~5 ℃ the speed of per hour heating up.
8, give vent to anger after a sintering finishes, the metal tubing and make sheath with metal sheet of packing in the head bottom of giving vent to anger is to guarantee that gas is overflowed by the top.The metal sheet sheath is provided with the hole, so that conduit passes.
High pure metal oxide compound used in the present invention, can be that fusing point is higher than 2500 ℃, and the metal oxide of stable in properties is a kind of or mixture in magnesium oxide (2852 ℃ of fusing points), zirconium white (2710 ℃ of fusing points), the hafnium oxide (2780~2920 ℃ of fusing points) etc. for example, and its purity is preferably in more than 99.99%.In one embodiment of the invention, selected metal oxide is a zirconium white.
Alkaline liquid used in the present invention can be a sodium hydroxide, and its concentration is 1%~40%.
Liquid volume that the present invention added and metal oxide particle volume ratio are 0.1~1: 1, and its optimum volume ratio is for can make blended metal oxide particle and liquid be in the thickness state.
The interior shape of forming mould used in the present invention can be for an Any shape that needs of giving vent to anger, so that produce the head of giving vent to anger of desired shape on demand.
The head of giving vent to anger of the present invention, its arrangement mode can be various, for example, can use the head of giving vent to anger separately, and its bottom is provided with three conduits, and these conduits can have multiple arrangement mode, and for example trilateral is respectively applied for and imports hydrogen, oxygen and water vapour; Also can make a plurality of heads of giving vent to anger, each head bottom of giving vent to anger is provided with a conduit, is respectively applied for the importing gas with various, and the head of then these being given vent to anger closely combines use.For preventing the inter gas premature reaction, except the sheath of bottom, next-door neighbour's the also available metal sheet that carries out of giving vent to anger between the head is isolated.Because gas mixes in silicon liquid, intense reaction takes place, produced localized hyperthermia, make that P, B, O, the C in the melted silicon removes with the gaseous emission volatilization.
The gas importing time of the present invention is: hydrogen 0.5~3h, water vapour 0.5~3h, oxygen 2~6h.
The head of giving vent to anger that the present invention manufactures, avoided supply conduit to contact with the direct of liquation, waste residue, it both can allow the gas of supply conduit evenly be given vent to anger by intergranular space, can eliminate again since the shearing force that liquation and gas bring in stirring, surging force to the direct effect of conduit.Simultaneously, because the zirconia particles diameter that the present invention adopts is a micron order, so the space is little between the zirconia particles, gap between particles is very even, because capillary existence, so liquation is difficult for suck-back and enters in the space of giving vent to anger that makes.A product of giving vent to anger that adopts manufacture method of the present invention to produce, gas is given vent to anger evenly, helps effectively improving liquation and flows, and makes uniformity of temperature profile in the liquation, and sufficient reacting is effectively removed impurity, avoids the gas waste simultaneously.Particle voids is little, be difficult for to stop up, and each its surperficial skull of end of operation reject can continue to use, and helps prolonging the work-ing life of head self of giving vent to anger.
Can be by method of the present invention with the P in the melted silicon, B, the most of volatilization of O, C reject, method of the present invention has the advantage that technology is simple, equipment is simple, running cost is low, reliable and stable.
Embodiment
The present invention will be further described below in conjunction with embodiment, but following embodiment only provides reference and explanation usefulness, but not the present invention is limited.
At first adopt following steps to make the head of giving vent to anger, its step is as follows:
1, selects resistant to elevated temperatures material high-purity zirconia;
2, high-purity zirconia is ground to the particle of 75~10 μ m sizes;
3, adding concentration in zirconium white is 25% sodium hydroxide liquid, and the liquid volume of adding be for can make blended zirconia particles and liquid be in the thickness state, and stirs;
4, the high-purity zirconia that stirs is packed into forming mould;
5, mould is warmed to 800 ℃, places under the above press device of 500T, suppress 4 hours, die sinking taking-up product when treating that temperature is reduced to 50 ℃;
6, product was positioned over the lucifuge place 10 days, allows sodium hydroxide continue volatilization;
7, product is delivered to carried out sintering in the High Temperature Furnaces Heating Apparatus, be warming up to 1000 ℃, be incubated 48 hours, cool to 200 ℃ of taking-ups with 2 ℃ speed per hour again with 2 ℃ the speed of per hour heating up.
8, give vent to anger after a sintering finishes, the metal tubing and make sheath with metal sheet of packing in gas head bottom is to guarantee that gas is overflowed by the top.
Gas imports the melted silicon method:
1, it is young in the head of giving vent to anger of 10 μ m to make three communicating poress with above-mentioned steps, and installs the metal sheet sheath.One of them cross section is a rectangle, and its long-width ratio is 2: 1, is used to import water vapour, and two cross sections are square in addition, and its length of side is wide for the former, is respectively applied for and imports hydrogen and oxygen.;
2, these three heads of giving vent to anger are combined to become a cross section be big foursquare air-guide part, given vent to anger and isolate mutually with metal sheet between the head, prevent from that inter gas from mixing too early to react;
3, will be arranged in the whole head of giving vent to anger and be placed in the bottom of reaction vessel, and connect the air guide conduit of different gas;
4, will fuse to 1800 ℃ melted silicon and pour in the container that the gas gatherer is housed;
5, gas with various is imported respectively in the melted silicon, its ratio is oxygen 50%, hydrogen 25%, water vapour 25%, gaseous tension 3KG.
6, melted silicon poured out and checks the air outlet degree of impairment after ventilating continuously one hour.
The present invention has made the perforation micropore head of giving vent to anger, be used to import gas with various, prevent the too early hybrid reaction of gas, make gas that intense reaction takes place in the melted silicon to produce localized hyperthermia that the P in the melted silicon, B, O, C remove with the gaseous emission volatilization in melted silicon and gas with various imported.And the perforation micropore of the present invention head of giving vent to anger be difficult for to stop up, through practical application:
1, connects a micropore air outlet slight damage at every turn, can use continuously more than 50 times.
2, following variation takes place in the P in the melted silicon, B, O, C:
P reduces to 30ppm by original 40ppm, descends 25%;
B reduces to 9pm by original 12m, descends 25%;
P reduces to 3000ppm by original 6000ppm, descends 50%;
C reduces to 600ppm by original 1500ppm, descends 40%.