CN102040219A - Method for preparing high-purity silicon by purifying industrial silicon - Google Patents
Method for preparing high-purity silicon by purifying industrial silicon Download PDFInfo
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Abstract
The invention discloses a method for preparing high-purity silicon by purifying industrial silicon. In the method, by combining the production of industrial silicon, externally refined silicon melt is directly used, oxidization slagging is performed in external refining equipment to remove boron, deslagged silicon melt is lifted and poured into phosphorous removal equipment, and when the silicon melt slowly cools down to room temperature after reduction slagging for removing boron, the slag layer and high-purity-content surface layer of the obtained silicon ingots are removed, and the obtained silicon ingots are crushed to 20 to 50 mesh powder, the powder is soaked in high-purity hydrochloric acid, washed and dried; and finally, oriented solidification is performed to further remove metal impurities, and thus, high-purity silicon with B content less than 0.5ppm, P content less than 1ppm and total metal impurity content less than 1ppm is obtained.
Description
Technical field: the invention belongs to industrial silicon refining techniques in the metallurgical industry smelting, the preparation method who relates to a kind of HIGH-PURITY SILICON, relate in particular to a kind ofly, directly utilize the external refining silicon melt to be raw material, prepare the production technology of HIGH-PURITY SILICON by a series of removal impurity operations in conjunction with industrial silicon production.
Background technology: the silicone content of industrial silicon generally reaches 97-99%, this other industrial silicon purity of level is lower, be of limited application, in order to enlarge silicon kind and range of application, generally will carry out external refining by the next silicon melt of hot stove from the ore deposit, adopt the bottom to feed oxidizing gas, will remove mutually by entering gas phase or slag behind the oxidation of impurities, the equipment of employing is " two-maing ladle " or the device with certain heating.This secondary refining method can be removed most calcium, aluminium in the silicon, obtains the chemical pure silicon of each model, and range of application further enlarges, and has increased the added value of silicon simultaneously.
Along with the silicon product is made sectionalization, the market demand potential of high purity silicon is huge, as wait until the raw material or the auxiliary agent of purposes as processing semiconductor, processing solar cell, processing high frequency electrical equipment, processing high purity material curative agent, production organosilicon, silicon solar cell particularly, along with energy growing tension, it is to reduce the production cost of silicon for solar cell significantly that sun power is popularized the key of utilizing.In addition, along with multiscale HIGH-PURITY SILICON market constantly enlarges, the silicon purification techniques towards become more meticulous more, cheap direction more develops.
Obviously, the industrial silicon that utilizes existing industrial silicon external refining purification techniques to obtain can not be met the need of market far away, is badly in need of providing the method for purified silicon a kind of cheapness, easy realization of industrialization.In existing disclosed HIGH-PURITY SILICON production method, it is the most sophisticated adopting the chemical method technology of Siemens Method.But this technological core is grasped abroad, and the technological process of production is long, and the by-product cyclic environment pollution is serious and have danger, and investment is big, and production cost is higher, and downstream user is difficult to accept.Be unfavorable for applying of derived product.
In order to avoid the great demand of Siemens Method, and the high passive situation of production cost to fund, domestic and international many research institutions multiple new method of purification that begins one's study, in these novel methods, representational physical metallurgy method because of it has cost advantage, is the focus that people paid close attention to.Metallurgy purification method mainly contains and solidifies removal of impurities, the removal of impurities of high vacuum high temperature evaporation, removing impurities by oxidation, acidleach removal of impurities, slag making removal of impurities, and aforesaid method can not be removed plurality of impurities in the silicon simultaneously.In general, metallic impurity generally can be removed well by oxidation refining, pickling, directional freeze in the silicon; Nonmetallic impurity in the silicon such as phosphorus, boron physicochemical property at normal temperatures are stable, and general method can not be removed well.Report is arranged, utilize the phosphorus full vapour pressure of closing at high temperature to be far longer than silicon, by the high vacuum high temperature evaporation phosphorus impurities is removed effectively, existing disclosure of the Invention number is CN101318655A, denomination of invention is a kind of method and device of removing foreign matter of phosphor in the silicon, and this method adopts the dephosphorization of twin-cathode ray beam refining purification techniques below high vacuum 10-3pa, realized working continuously, sample is in a small amount well removed the phosphorus effect.But this method exists deficiency to be, produce so high vacuum condition, and facility investment is relatively large, the energy consumption height, and high-vacuum apparatus is difficult for being amplified to the suitability for industrialized production level of extensiveization.For the boron impurity in the silicon, its boiling point is up to 2550 ℃, and the method by the high temperature high vacuum does not have obvious effects, and chemical property is stable, and with general acid-respons, the way of pickling is not inoperative to it yet, segregation coefficient is big, and the method by directional freeze also is difficult to remove.Many patents are also disclosed the method for removing boron both at home and abroad, as patent of invention number 98105942.2 " removing the method and apparatus of boron from Pure Silicon Metal " is the Pure Silicon Metal container that silicon oxide makes of packing into, with non-transfer type plasma body, the transfer type plasma body, combination between the heating unit such as high-frequency induction and resistance, Pure Silicon Metal is melted to more than 1550 ℃, above melt, use hollow plasma torch made of copper, spray into plasma jet at a certain angle, the mixed gas of water vapor and hydrogen or carbon monoxide or paraffinic hydrocarbons, wherein water vapor accounts for the 10-40% volume of above-mentioned three class mixed gas total amounts, hydrogen accounts for the 5-90% of above-mentioned three class mixed gas total amounts, also is blown into the mixed gas of water vapor and the combination of rare rare gas element from the bottom porous.This technology is for carrying out powerful stirring action to molten silicon, adopt by rotatingfield or by being blown into gas and conventional liquation paddling process such as stir, by be blown into oxidizing gas make boron become boron oxide and from molten silicon volatilization remove boron, reached and removed the boron purpose.But this method also exists limitation to be: the amount of making the plasma fluid with argon, the rare rare gas element of helium is big, and cost is higher; The heat energy utilization rate is low, and energy consumption is bigger than normal; Plasma jet and reducing gas are blown into melt liquid level from the melt top, and silicon splashes and causes damage.Be not suitable for extensive industrialization.
Summary of the invention: purpose of the present invention, being will be from the hot stove in smelting industrial silicon ore deposit next " silicon water " in conjunction with the production of industrial silicon, by a series of simple removal of impurities operations, prepare boron content＜0.5ppm, the HIGH-PURITY SILICON of phosphorus content 1ppm and total inclusion metallic content＜1ppm, with the simplest equipment, minimum production process, minimum cost are produced highly purified silicon, to satisfy the requirement of growing market to HIGH-PURITY SILICON.
The present inventor, in order to achieve the above object, test, work out complete the purifying of a cover finally and prepare the simple method of HIGH-PURITY SILICON by industrial silicon through secular groping, mainly use in silicon melt, to add the method that special slag carries out slag making, remove nonmetallic impurity in the silicon.
Slag making of the present invention, principle is meant that the special slag that utilizes in nonmetallic impurity in the silicon melt such as boron, phosphoric and the adding silicon melt is by complexing or chemical reaction, the product that forms can on float to the silicon melt surface or sink to the slag phase of silicon melt bottom, slag and purified silicon melt are separated, reach the impurity elimination purpose.
In experiment, the contriver finds that the oxide compound ratio of boron is easier to enter in the basic slag, and the present invention promptly is by by the industrial silicon refining time, feeds oxidizing gas with the boron oxidation, reaches the purpose of removing boron thereby make boron oxide compound enter special slag.But utilize slag and the operational condition of removing boron, not obvious to the removal effect of phosphorus.Find again in the experiment, under protection of inert gas, the phosphorus in the industrial silicon can with calcium alloy with strong reducing property or calcium cpd generation chemical reaction, reaction product enters the slag phase, by separating the slag phase, thereby reaches the purpose of removing foreign matter of phosphor in the silicon.
A kind of purification by industrial silicon of the present invention prepares the method for HIGH-PURITY SILICON, is in conjunction with industrial silicon production, directly utilizes the external refining silicon melt, carries out oxidative slagging and remove boron in external refining equipment; Remove the silicon melt behind the boron slag, on pour into the equipment of dephosphorization, reduction slag making dephosphorization; Silicon melt controlled chilling speed after the dephosphorization slowly cools to room temperature, the silicon ingot that obtains is removed slag blanket, top layer that foreign matter content is high, be crushed to granularity 20-50 order, enter again in the high purity hydrochloric acid and soak, clean, oven dry is carried out directional freeze at last and is further removed metallic impurity, obtains B content＜0.5ppm, P content＜1ppm, the HIGH-PURITY SILICON of total inclusion metallic content＜1ppm;
The present invention finishes by following operation steps: A, oxidative slagging remove boron: pour " two-maing ladle " lining that fills in advance except that boron molten slag into from the silicon water that the hot stove in smelting industrial silicon ore deposit comes, utilize silicon under molten state, from " two-maing ladle " bottom aerating oxygen, carry out oxidative slagging in the metallic impurity in the silicon oxide melt and remove boron, most of calcium, aluminium are simultaneously in removing silicon, boron becomes oxide compound and enters slag and remove in the lump mutually, and the oxidation refining time is controlled at 10-50min; B, reduction slag making dephosphorization: finish oxidative slagging except that behind the boron, to " two-man ladle " and go to the casting workshop by the dolly of coming out of the stove, updip is poured upper strata silicon liquid in the dephosphorization equipment crucible into, crucible is equipped with the dephosphorization slag in advance in the dephosphorization equipment, after filling with silicon in the crucible, seal bell immediately, and started vacuum pump, extracted furnace air out; Under reaching the certain vacuum condition in the stove, stop to vacuumize, feed rare gas element, make stove inner and outer air pressure unanimity, start heating unit, silicon is kept under molten state-10-50min; C, matting: after dephosphorization finishes, control silicon melt speed of cooling is to room temperature, open bell, take out silicon ingot, remove slag blanket and foreign matter content is high top layer all around after, be crushed to the 20-50 order, putting into high-purity dilute hydrochloric acid soaked 2-4 hour, further remove slag and the metallic impurity that are soluble in dilute hydrochloric acid, pure water cleans the neutrality to washing lotion PH, oven dry; D, accurate pointing solidify: the silicon with oven dry, in directional solidification furnace, carry out accurate pointing, and further remove metallic impurity, get target product;
Above-mentioned external refining equipment is meant the equipment that existing industrial silicon carries out external refining, is meant " two-maing ladle " more specifically, and above-mentioned dephosphorization equipment is meant the device with heating, is meant vacuum induction melting furnace more specifically, carries out oxidative slagging in " two-maing ladle " lining and removes boron; In vacuum induction melting furnace, reduce the slag making dephosphorization;
When reduction slag making dephosphorization, vacuum condition is meant that the vacuum tightness of induction heater is between 500-1000pa;
The boron molten slag that removes of the present invention is made up of following compounds: CaO-SiO2, CaO, CaF2, NaO-SiO2; Remove each component composition mass percentage content of boron molten slag 70-95%CaO-SiO2,10-1%CaO, 10-0.5%CaF2,10-3.5%NaO-SiO2 respectively, adding remove the 5-50% that the boron molten slag quality accounts for the silicon melt total mass; The dephosphorization slag is made up of the calcium alloy with reductibility or calcium cpd and fusing assistant, auxiliary agent, more specifically is meant by any one or two kinds of and CaF2, CaCL2, CaO among CaAl, CaSi, CaSiAl, CaSiMg, CaMg, CaC2, the Ca3N2 and forms jointly; Each component composition mass percentage content difference 55-95% calcium alloy of dephosphorization slag or compound, 10-0.5%CaF2,20-1%CaCL2,15-3.5%CaO, the dephosphorization slag quality of adding accounts for the 5-40% of silicon melt total mass;
Carry out oxidative slagging is made up of following compounds except that boron molten slag in " two-maing ladle " lining: CaO-SiO2, CaO, CaF2, NaO-SiO2; Remove each component composition mass percentage content of boron molten slag 70-95%CaO-SiO2,10-1%CaO, 10-0.5%CaF2,10-3.5%NaO-SiO2 respectively, adding remove the 5-50% that the boron molten slag quality accounts for the silicon melt total mass; In vacuum induction melting furnace, reduce slag making, the dephosphorization slag is made up of the calcium alloy with reductibility or calcium cpd and fusing assistant, auxiliary agent, more specifically is meant by any one or two kinds of and CaF2, CaCL2, CaO among CaAl, CaSi, CaSiAl, CaSiMg, CaMg, CaC2, the Ca3N2 and forms jointly; Each component composition mass percentage content difference 55-95% calcium alloy of dephosphorization slag or compound, 10-0.5%CaF2,20-1%CaCL2,15-3.5%CaO, the dephosphorization slag quality of adding accounts for the 5-40% of silicon melt total mass;
Silicon melt after the dephosphorization, controlled chilling speed slowly cools to room temperature, is that the silicon melt speed of cooling is controlled at 10-30 ℃/min.
Matting of the present invention is meant that being diluted to mass concentration with analytical pure hydrochloric acid is 10-20%, removes the boron dephosphorization and is crushed to granularity 20～50 purpose silicon grains and soak.
The present invention carries out oxidative slagging and removes boron when directly utilizing external refining equipment and silicon melt to carry out oxidation refining, saved solid silicon reflow process and energy consumption, has removed the HIGH-PURITY SILICON production cost low, has saved facility investment.The present invention is in conjunction with the slag refining techniques, according to impurity different qualities in the silicon, by adding different slags and the impurity generation chemical reaction in the silicon melt, reaction product enters the slag phase, by separating the slag phase, reach and remove the impurity purpose,, further remove unsegregated slag and metallic impurity in the silicon again in conjunction with the wet purification principle, technical process is short, operational condition is easy to realize industrialization, and energy consumption is low, greatly reduces production cost.
Embodiment: embodiment 1, the present invention finish according to the following steps:
1, will add the lining of " two-maing ladle " of purified the industrial silicon furnace in advance except that boron molten slag, " silicon water " inflow that the hot stove in smelting industrial silicon ore deposit comes " is two-mand ladle ", when silicon liquid reaches 1/3rd silicon bag degree of depth, promptly opens " two-maing ladle " bottom oxygen valve, stir silicon melt, carry out oxidative slagging and remove boron.Behind the reaction 15min, promptly close oxygen, leave standstill silicon liquid and treat silicon, slag layering.
Removing the boron molten slag composition is: 82%CaO-SiO2,2%CaO, 8%CaF2,8%NaO-SiO2.Add the quality of removing boron molten slag and account for silicon melt quality 10%.
2, will " two-man ladle " and be pulled to slag making dephosphorization workshop by the dolly of coming out of the stove and carry out dephosphorization operation, on toppled over silicon liquid after, continue to feed pressurized air 3～5min, prevent the obstruction of air dispelling hole, take white residue after a while off, wait the boron that removes of pending next stove to operate.
3, the dephosphorization slag is added in advance in the plumbago crucible bucket in the 100kg vacuum induction melting furnace, " two-maing ladle " goes to the dephosphorization workshop by the dolly of coming out of the stove, and updip is poured upper strata silicon liquid in the plumbago crucible bucket into, has sealed bell immediately, and the startup vacuum pump, extract furnace air out; When vacuum reaches 600pa in the stove, stop to vacuumize, and feed rare gas element such as argon gas, make stove inner and outer air pressure unanimity.Start induction heating device simultaneously, make silicon under molten state, keep 25min.The dephosphorization slag is formed: 80%CaC2,5%CaF2,5%CaCL2,10%CaO.The quality that adds the dephosphorization slag accounts for silicon melt quality 10%.
4, after dephosphorization finishes, stop induction heating, control silicon melt speed of cooling, keep 20 ℃ of per minute coolings, to be cooled to room temperature, open bell, take out silicon ingot, after removing slag blanket and foreign matter content is high top layer all around, be crushed to granularity 20 orders, put into analytically pure dilute hydrochloric acid and soaked 3 hours, dilute hydrochloric acid concentration is 10%, clean to washing lotion pH value neutrality oven dry at last with pure water.
5, accurate pointing solidifies: the silicon with oven dry, in directional solidification furnace, carry out accurate pointing, and further remove metallic impurity, get target product.
Sampling analysis, subordinate list 1 as a result.
Embodiment 2, comparative example 1 change the slag amount that adds, and it is siliceous amount 20% that adding removes boron molten slag, and the dephosphorization slag is 15% of a siliceous amount, and other condition is with embodiment 1.
Sampling analysis, subordinate list 1 as a result.
Embodiment 3, comparative example 1 change the slag amount that adds, and it is siliceous amount 30% that adding removes boron molten slag, and the dephosphorization slag is 20% of a siliceous amount, and other condition is with embodiment 1.
Sampling analysis, subordinate list 1 as a result.
Embodiment 4,1, will add the lining of " two-maing ladle " of purified the industrial silicon furnace in advance except that boron molten slag, " silicon water " inflow that the hot stove in smelting industrial silicon ore deposit comes " is two-mand ladle ", when silicon liquid reaches 1/3rd silicon bag degree of depth, promptly opens " two-maing ladle " bottom oxygen valve, stir silicon melt, carry out oxidative slagging and remove boron.Behind the reaction 30min, promptly close oxygen, leave standstill silicon liquid and treat silicon, slag layering.Removing the boron molten slag composition is: 90%CaO-SiO2,2%CaO, 1%CaF2,7%NaO-SiO2.Add the quality of removing boron molten slag and account for silicon melt quality 20%.
2, will " two-man ladle " and be pulled to slag making dephosphorization workshop by the dolly of coming out of the stove and carry out dephosphorization operation, on toppled over silicon liquid after, continue to feed pressurized air 3～5min, prevent the obstruction of air dispelling hole, take white residue after a while off, wait the boron that removes of pending next stove to operate.
3, the dephosphorization slag is added in advance in the plumbago crucible bucket in the 100kg vacuum induction melting furnace, " two-maing ladle " goes to the dephosphorization workshop by the dolly of coming out of the stove, and updip is poured upper strata silicon liquid in the plumbago crucible bucket into, has sealed bell immediately, and the startup vacuum pump, extract furnace air out; When vacuum reaches 1000pa in the stove, stop to vacuumize, and feed rare gas element such as argon gas, make stove inner and outer air pressure unanimity.Start induction heating device simultaneously, make silicon under molten state, keep 30min.The dephosphorization slag is formed: 40%CaMg and 50%CaC2,2%CaF2,5%CaCL2,3%CaO.The quality that adds the dephosphorization slag accounts for silicon melt quality 15%.
4, after dephosphorization finishes, stop induction heating, control silicon melt speed of cooling, keep 20 ℃ of per minute coolings, to be cooled to room temperature, open bell, take out silicon ingot, after removing slag blanket and foreign matter content is high top layer all around, be crushed to granularity 20 orders, put into analytically pure dilute hydrochloric acid and soaked 3 hours, dilute hydrochloric acid concentration is 12%, clean to washing lotion pH value neutrality oven dry at last with pure water.
5, accurate pointing solidifies: the silicon with oven dry, in directional solidification furnace, carry out accurate pointing, and further remove metallic impurity, get target product.
Sampling analysis, subordinate list 1 as a result.
Embodiment 5,1. will add the lining of " two-maing ladle " of purified the industrial silicon furnace in advance except that boron molten slag, " silicon water " inflow that the hot stove in smelting industrial silicon ore deposit comes " is two-mand ladle ", when silicon liquid reaches 1/3rd silicon bag degree of depth, promptly opens " two-maing ladle " bottom oxygen valve, stir silicon melt, carry out oxidative slagging and remove boron.Behind the reaction 30min, promptly close oxygen, leave standstill silicon liquid and treat silicon, slag layering.Removing the boron molten slag composition is: 85%CaO-SiO2,2%CaO, 1%CaF2,12%NaO-SiO2.Add the quality of removing boron molten slag and account for silicon melt quality 15%.
2. will " two-man ladle " is pulled to slag making dephosphorization workshop by the dolly of coming out of the stove and carries out dephosphorization operation, on toppled over silicon liquid after, continue to feed pressurized air 3～5min, prevent the obstruction of air dispelling hole, take white residue after a while off, wait the boron that removes of pending next stove to operate.
3. the dephosphorization slag is added in advance in the plumbago crucible bucket in the 100kg vacuum induction melting furnace, " two-maing ladle " goes to the dephosphorization workshop by the dolly of coming out of the stove, and updip is poured upper strata silicon liquid in the plumbago crucible bucket into, has sealed bell immediately, and the startup vacuum pump, extract furnace air out; When vacuum reaches 1000pa in the stove, stop to vacuumize, and feed rare gas element such as argon gas, make stove inner and outer air pressure unanimity.Start induction heating device simultaneously, make silicon under molten state, keep 40min.The dephosphorization slag is formed: 40%CaMg and 50%CaAl, 2%CaF2,5%CaCL2,3%CaO.The quality that adds the dephosphorization slag accounts for silicon melt quality 15%.
4. after dephosphorization finishes, stop induction heating, control silicon melt speed of cooling, keep 20 ℃ of per minute coolings, to be cooled to room temperature, open bell, take out silicon ingot, after removing slag blanket and foreign matter content is high top layer all around, be crushed to granularity 50 orders, put into analytically pure dilute hydrochloric acid and soaked 3 hours, dilute hydrochloric acid concentration is 12%, clean to washing lotion pH value neutrality oven dry at last with pure water.
5. accurate pointing solidifies: the silicon with oven dry, in directional solidification furnace, carry out accurate pointing, and further remove metallic impurity, get target product.
Sampling analysis, subordinate list 1 as a result.
Embodiment 6,1. will add the lining of " two-maing ladle " of purified the industrial silicon furnace in advance except that boron molten slag, " silicon water " inflow that the hot stove in smelting industrial silicon ore deposit comes " is two-mand ladle ", when silicon liquid reaches 1/3rd silicon bag degree of depth, promptly opens " two-maing ladle " bottom oxygen valve, stir silicon melt, carry out oxidative slagging and remove boron.Behind the reaction 40min, promptly close oxygen, leave standstill silicon liquid and treat silicon, slag layering.Removing the boron molten slag composition is: 85%CaO-SiO2,2%CaO, 1%CaF2,12%NaO-SiO2.Add the quality of removing boron molten slag and account for silicon melt quality 15%.
2. will " two-man ladle " is pulled to slag making dephosphorization workshop by the dolly of coming out of the stove and carries out dephosphorization operation, on toppled over silicon liquid after, continue to feed pressurized air 3～5min, prevent the obstruction of air dispelling hole, take white residue after a while off, wait the boron that removes of pending next stove to operate.
3. the dephosphorization slag is added in advance in the plumbago crucible bucket in the 100kg vacuum induction melting furnace, " two-maing ladle " goes to the dephosphorization workshop by the dolly of coming out of the stove, and updip is poured upper strata silicon liquid in the plumbago crucible bucket into, has sealed bell immediately, and the startup vacuum pump, extract furnace air out; When vacuum reaches 1000pa in the stove, stop to vacuumize, and feed rare gas element such as argon gas, make stove inner and outer air pressure unanimity.Start induction heating device simultaneously, make silicon under molten state, keep 40min.The dephosphorization slag is formed: 40%CaMg and 50%Ca3N2,2%CaF2,5%CaCL2,3%CaO.The quality that adds the dephosphorization slag accounts for silicon melt quality 15%.
4. after dephosphorization finishes, stop induction heating, control silicon melt speed of cooling, keep 20 ℃ of per minute coolings, to be cooled to room temperature, open bell, take out silicon ingot, after removing slag blanket and foreign matter content is high top layer all around, be crushed to granularity 50 orders, put into analytically pure dilute hydrochloric acid and soaked 3 hours, dilute hydrochloric acid concentration is 15%, clean to washing lotion pH value neutrality oven dry at last with pure water.
5. accurate pointing solidifies: the silicon with oven dry, in directional solidification furnace, carry out accurate pointing, and further remove metallic impurity, get target product.
Sampling analysis, subordinate list 1 as a result.
Quality after subordinate list 1 industrial silicon is purified
From embodiment 1-3 as can be seen, with the increase that add to remove boron, dephosphorization slag amount, boron in the silicon, phosphorus content are on a declining curve.From embodiment 4-6, change the composition that adds slag, and operational condition, little to quality influence.
Below in conjunction with the embodiments the present invention detailed explanation and explanation have been carried out, but those skilled in the art understand, do not breaking away from the spirit and scope of the invention, any change, improvement, variant and the equivalent of the embodiment of the invention is all in the scope of the invention of claims definition.
The present invention is by test, " the silicon water " that the hot stove in smelting industrial silicon ore deposit is next, by a series of simple removal of impurities operations, prepared boron content＜0.5ppm, the HIGH-PURITY SILICON of phosphorus content 1ppm and total inclusion metallic content＜1ppm, with the simplest equipment, minimum production process, minimum cost is produced highly purified silicon, satisfy of the requirement of growing market to HIGH-PURITY SILICON, significantly reduced the cost of silicon for solar cell, be silicon solar cell, sun power is popularized and is utilized, further create condition for the target of national energy-saving and emission-reduction, had bigger economic benefit and social benefit prospect.
Claims (8)
1. purify by industrial silicon and prepare the method for HIGH-PURITY SILICON for one kind, it is characterized in that directly utilizing the external refining silicon melt, in external refining equipment, carry out oxidative slagging except that boron in conjunction with industrial silicon production; Remove the silicon melt behind the boron slag, on pour into the equipment of dephosphorization, reduction slag making dephosphorization; Silicon melt controlled chilling speed after the dephosphorization slowly cools to room temperature, the silicon ingot that obtains is removed slag blanket, top layer that foreign matter content is high, be crushed to granularity 20-50 order, enter again in the high purity hydrochloric acid and soak, clean, oven dry is carried out directional freeze at last and is further removed metallic impurity, obtains B content＜0.5ppm, P content＜1ppm, the HIGH-PURITY SILICON of total inclusion metallic content＜1ppm.
2. a kind of the purification by industrial silicon according to claim 1 prepares the method for HIGH-PURITY SILICON, it is characterized in that the present invention finishes by following operation steps: A, oxidative slagging remove boron: pour " two-maing ladle " lining that fills in advance except that boron molten slag into from the silicon water that the hot stove in smelting industrial silicon ore deposit comes, utilize silicon under molten state, from " two-maing ladle " bottom aerating oxygen, carry out oxidative slagging in the metallic impurity in the silicon oxide melt and remove boron, most of calcium, aluminium are simultaneously in removing silicon, boron becomes oxide compound and enters slag and remove in the lump mutually, and the oxidation refining time is controlled at 10-50min; B, reduction slag making dephosphorization: finish oxidative slagging except that behind the boron, to " two-man ladle " and go to the casting workshop by the dolly of coming out of the stove, updip is poured upper strata silicon liquid in the dephosphorization equipment crucible into, crucible is equipped with the dephosphorization slag in advance in the dephosphorization equipment, after filling with silicon in the crucible, seal bell immediately, and started vacuum pump, extracted furnace air out; Under reaching the certain vacuum condition in the stove, stop to vacuumize, feed rare gas element, make stove inner and outer air pressure unanimity, start heating unit, make silicon under molten state, keep 10-50min; C, matting: after dephosphorization finishes, control silicon melt speed of cooling is to room temperature, open bell, take out silicon ingot, remove slag blanket and foreign matter content is high top layer all around after, be crushed to the 20-50 order, putting into high-purity dilute hydrochloric acid soaked 2-4 hour, further remove slag and the metallic impurity that are soluble in dilute hydrochloric acid, pure water cleans the neutrality to washing lotion PH, oven dry; D, accurate pointing solidify: the silicon with oven dry, in directional solidification furnace, carry out accurate pointing, and further remove metallic impurity, get target product.
3. a kind of the purification by industrial silicon according to claim 1 and 2 prepares the method for HIGH-PURITY SILICON, it is characterized in that external refining equipment is meant the equipment that existing industrial silicon carries out external refining, be meant " two-maing ladle " more specifically, dephosphorization equipment is meant the device with heating, be meant vacuum induction melting furnace more specifically, carry out oxidative slagging in " two-maing ladle " lining and remove boron; In vacuum induction melting furnace, reduce the slag making dephosphorization.
4. a kind of the purification by industrial silicon according to claim 3 prepares the method for HIGH-PURITY SILICON, and when it is characterized in that reducing the slag making dephosphorization, vacuum condition is meant that the vacuum tightness of induction heater is between 500-1000pa.
5. a kind of the purification by industrial silicon according to claim 1 and 2 prepares the method for HIGH-PURITY SILICON, it is characterized in that removing boron molten slag and is made up of following compounds: CaO-S iO2, CaO, CaF2, NaO-SiO2; Remove each component composition mass percentage content of boron molten slag 70-95%CaO-SiO2,10-1%CaO, 10-0.5%CaF2,10-3.5%NaO-SiO2 respectively, adding remove the 5-50% that the boron molten slag quality accounts for the silicon melt total mass; The dephosphorization slag is made up of the calcium alloy with reductibility or calcium cpd and fusing assistant, auxiliary agent, more specifically is meant by any one or two kinds of and CaF2, CaCL2, CaO among CaAl, CaSi, CaSiAl, CaS iMg, CaMg, CaC2, the Ca3N2 and forms jointly; Each component composition mass percentage content difference 55-95% calcium alloy of dephosphorization slag or compound, 10-0.5%CaF2,20-1%CaCL2,15-3.5%CaO, the dephosphorization slag quality of adding accounts for the 5-40% of silicon melt total mass.
6. a kind of the purification by industrial silicon according to claim 3 prepares the method for HIGH-PURITY SILICON, it is characterized in that removing boron molten slag and is made up of following compounds: CaO-SiO2, CaO, CaF2, NaO-SiO2; Remove each component composition mass percentage content of boron molten slag 70-95%CaO-SiO2,10-1%CaO, 10-0.5%CaF2,10-3.5%NaO-SiO2 respectively, adding remove the 5-50% that the boron molten slag quality accounts for the silicon melt total mass; The dephosphorization slag is made up of the calcium alloy with reductibility or calcium cpd and fusing assistant, auxiliary agent, more specifically is meant by any one or two kinds of and CaF2, CaCL2, CaO among CaAl, CaSi, CaSiAl, CaSiMg, CaMg, CaC2, the Ca3N2 and forms jointly; Each component composition mass percentage content difference 55-95% calcium alloy of dephosphorization slag or compound, 10-0.5%CaF2,20-1%CaCL2,15-3.5%CaO, the dephosphorization slag quality of adding accounts for the 5-40% of silicon melt total mass.
7. a kind of the purification by industrial silicon according to claim 1 and 2 prepares the method for HIGH-PURITY SILICON, it is characterized in that the silicon melt speed of cooling is controlled at 10-30 ℃/min.
8. a kind of the purification by industrial silicon according to claim 1 and 2 prepares the method for HIGH-PURITY SILICON, it is characterized in that matting is meant that being diluted to mass concentration with analytical pure hydrochloric acid is that 10-20% soaks silico briquette.
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