CN101423221A - Silicon vacuum smelting purification method employing powder metallurgy - Google Patents
Silicon vacuum smelting purification method employing powder metallurgy Download PDFInfo
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- CN101423221A CN101423221A CNA2008102028222A CN200810202822A CN101423221A CN 101423221 A CN101423221 A CN 101423221A CN A2008102028222 A CNA2008102028222 A CN A2008102028222A CN 200810202822 A CN200810202822 A CN 200810202822A CN 101423221 A CN101423221 A CN 101423221A
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Abstract
The invention discloses a silicon vacuum smelting and purifying method by adopting powder metallurgy. The powder silicon material is cast into block shape and arranged in a vacuum smelting furnace or other equipment where powder is not suitable for being added to be processed or purified; furthermore, the powder silicon material can be added with an adhesive and uniformly mixed before being cast into block shape; the method firstly presses and forms the powder material; after being pressed as block-shaped material, the powder is added into the vacuum furnace, thus avoiding the loss of the silicon material, the pollution easily caused on the furnace and vacuum system and the influence on the service life of the vacuum smelting equipment; the method also aims at providing an adhesive which can easily form the nonmetal crystal silicon material which is lack of normal properties of metal such as ductility, plasticity, high hardness and large brittleness and extremely difficult to be pressed and formed at normal temperature; meanwhile, the adhesive causes the increment of the impurities of the silicon, and can react with the existing impurities of the silicon to separate the impurities from the silicon so as to improve the efficiency and purity.
Description
Technical field
The present invention relates to silicon purification smelting technique field, particularly a kind of will Pure Silicon Metal through pulverizing and wet purification after make bulk, enter vacuum melting again and purify and obtain the process for extracting of solar energy level silicon.
Background technology
In the process of the production of silicon and purification, especially in the process of physics or metallurgy method (also comprising chemical method) preparation purified silicon, mostly be earlier Pure Silicon Metal to be pulverized, afterwards with acid or alkali or other solution and silica flour reaction, because the area of the silicon material after pulverizing increases, therefore, reagent can be as much as possible with silicon in especially metallic impurity reaction of impurity.The mode of this solid-liquid ion-exchange can be removed metallic impurity in the silicon with lower cost most ofly, and still, this method is difficult to remove the nonmetallic impurity in the silicon, especially phosphorus and boron etc.
In order to remove dephosphorization and boron, also to adopt the method for vacuum melting.But, through the silica flour after the solid-liquid ion-exchange,, after putting into vacuum oven, be easy to be extracted out outside the stove by vacuum because granularity is less, not only cause the loss of silicon material, also cause easily influencing the life-span of vacuum melting equipment in the stove and the pollution of vacuum system.
At present, the existing mode that adopts compression moulding is handled metal and other non-metallic minerals such precedent of purifying, and still, also has no talent the silicon material was adopted same mode.And, both helped the silicon material fixed by adding the mode of suitable binding agent, and can assist removal impurity again, nobody delivered same method more.
Summary of the invention
Main purpose of the present invention is to address the above problem, a kind of silicon vacuum smelting purification method that adopts powder metallurgy is provided, this method is pressed powder earlier, after being pressed into block material, put into vacuum oven again, can avoid causing the loss of silicon material, also cause easily influencing the life-span of vacuum melting equipment in the stove and the pollution of vacuum system; Another purpose provides binding agent, this binding agent can with lack ductility that metal often has and plasticity, hardness height at normal temperatures, fragility is big, and the very big nonmetal crystalline silicon material of the difficulty that causes compression moulding, be easy to moulding, this binding agent not only causes the increasing of impurity in the silicon simultaneously, can also react with existing impurity in the silicon, impurity is wherein separated from silicon, raise the efficiency and purity.
In order to achieve the above object, technical scheme provided by the invention is: a kind of silicon vacuum smelting purification method that adopts powder metallurgy is that powdered silicon material is cast into bulk, puts into equipment that vacuum melting furnace or other be not suitable for placing powder in processing or purify;
Before the silicon material is cast into bulk, powdered silicon material is added binding agent, and stir;
Binding agent is to contain the content that pollutes silicon material impurity to be lower than 0.01% simple substance or compound;
Binding agent contains aerobic, hydrogen and other solid oxygen element; Gu the oxygen branch that oxygen element contains at high temperature just discharges;
Binding agent is that the compound or the mixture of one or more above-mentioned substances in the materials such as CaO, MgO, BaO, FeO, CaF2, Na2O, SiO2, H2O, AL2O3, NaOH, BaCO3, Ba (OH) 2 and Na2CO3 constitutes.
The present invention adopts the principle of work and the beneficial effect of the silicon vacuum smelting purification method of powder metallurgy: this method makes silicon material die cast, put into vacuum oven again, can avoid causing the loss of silicon material, also cause easily influencing the life-span of vacuum melting equipment in the stove and the pollution of vacuum system.
This method also adopts binding agent to make silicon material die cast, and on the one hand, this binding agent will help hardening of silica flour and grumeleuse, reduce the powder on surface, on the other hand, because the relation that will purify, the binding agent that is added definitely can not contain or minute quantity contains the material that is difficult to remove from silicon.
Because Pure Silicon Metal is to belong to crystal, more crisp, and fusing point is higher, reaches 1414 degrees centigrade, the hardness height, thereby Pure Silicon Metal is difficult to the method for common powder metallurgy or die casting it pressure be melted after being broken into powder, needs to adopt binding agent for this reason.After adopting binding agent, behind the pressurized, silica flour is compressed silica flour in mould, mutual extrusion between the powder particle, and the silicon material becomes bulk.Binding agent increases the intensity of silico briquette.
But because the follow-up needs of silicon material carry out the purification of solar level, therefore, the adding of any material all must be very careful in the silicon material.Otherwise, will cause the very difficult removal of impurity, bring difficulty for follow-up purification.For this reason, the tackiness agent that the present invention is earlier selected requires purity more than 99.99%.
In silicon, several elements are arranged, as Al, B, P waits element because in the periodic table of elements, be positioned at element silicon around, the character and the silicon of simple substance element at high temperature are very approaching, and is therefore, difficult to remove.With the B element is example, adopts vacuum melting, and the fusing point of B is than also high more than 1000 degree of silicon; Adopt directional freeze, the segregation coefficient of B in silicon is 0.8, with 10 minutes approaching, therefore, almost can not be when directional freeze by solid-liquid separation.And at high temperature the saturated vapor pressure of B is the order of magnitude of 10-4Pa, and than little two orders of magnitude of silicon, therefore, vacuum outgas also can't allow B volatilize.Therefore, B is that a kind of extremely is difficult to the element that separates and remove in silicon.Therefore, had better not contain these elements in the binding agent.
Binding agent of the present invention, easy agglomerative has also played the effect of air release agent, slag former and fractional condensation agent when vacuum melting simultaneously when impelling silica flour in compression moulding.When vacuum melting, the partial impurities in the silicon material and the element of binding agent form oxide compound or other compound and volatilize in high-temperature vacuum; The element of partial impurities and binding agent or formation binding agent forms new firm compound in addition, and this new compound is owing to be insoluble to silicon, and proportion and silicon are variant, or be sunken to bottom the silicon liquid, when solidifying, silicon liquid solidifies at first, or float on silicon liquid surface, when crystallization, become white residue, thereby from silicon liquid, separate out; Also have some impurity such as boron and phosphorus etc. and element reaction in binding agent or the binding agent to generate firm compound, though this compound proportion and silicon liquid are approaching, or because content can not from silicon, separate out very little, but because the segregation coefficient in silicon is more much smaller than the segregation coefficient of phosphorus and boron, therefore, when silicon solidifies, be enriched to the top of silicon ingot because of the effect of segregation.
The binding agent that the present invention narrated, a kind of by in CaO, MgO, BaO, FeO, CaF2, Na2O, SiO2, H2O, Al2O3, NaOH, the materials such as BaCO3, Ba (OH) 2, Na2CO3, or the compound of several materials or mixture constitute.At different impurity, selected binding agent is different.In addition, too big as fruit granule, also need to add silicate and or vinyl cyanide etc., increase the intensity of ingot bar.
These binding agents are in as binding agent, also as the reactant of degasification and slag making, because under the situation of powder, carried out good the mixing with silica flour, very big with the contact area of silicon, therefore, when carrying out the high-temperature vacuum melting, can fully react with silicon, play the effect of impurity elimination and purification to greatest extent.
For example, aerating oxygen and boron reaction generate boron oxide compound, and volatilization at high temperature then is a kind of method of removing boron from silicon.But when the content of boron during less than 5 PPM, the boron of this trace be removed, if adopt oxygen blown mode, oxidation can take place and cause a large amount of losses of silicon in silicon too.And the selected binding agent of the present invention, can form a kind of composite salt at low temperatures, under high temperature, oxygen just disengages, and reacts with boron in the silicon, form boron trioxide, under vacuum and high temperature, volatilize, further remove boron thereby reach, simultaneously, contained protium can prevent the oxidation of silicon, thereby can reduce the purpose of silicon material loss again.Not only fully impurity elimination is purified, and can also play energy-conservation effect.
In the silicon material fusion stage, oxide compound in metal in the binding agent and the silicon material and silicate are taken oxygen formula oxidizing reaction by force, simultaneously, also take place to decompose and discharge oxygen, in such process, produced bonded white residues such as metal oxide-silicon-dioxide, some sinks to crucible bottom more greatly because of proportion these white residues, and some gently floats over silicon liquid surface because of proportion.This process can be eliminated about 30% phosphorus and 10% boron.
Spend and carry out in the process of vacuum melting in the scope of 1900 degree temperature and reach 1500 in temperature, because furnace pressure is less, but boron is very little because of saturation vapour pressure, so the rate of volatilization of pure boron is very little.The tackiness agent that the present invention added at high temperature discharges oxygen, and combining with boron becomes boron oxide compound, and the saturation vapour pressure of this boron oxide compound boron that compares is much bigger, and therefore, the rate of volatilization of oxide compound is bigger than boron, and in the evaporable process, boron also is pulled away.In this process, can eliminate about 60% phosphorus and 30% boron.After this process was finished, the phosphorus in the silicon material can remove about 90%, and boron also has about 40%.
Afterwards, anticipate in the process of solidifying at silicon, the metal M in the binding agent has formed the boride of metal with B, and the fusing point of this oxide compound is very high, though proportion is bigger, because content is very little, floats over silicon liquid surface so can't form slag from silicon.But the chemical bond ionization energy of this boron oxide compound is bigger, therefore, can not rupture in the process that silicon liquid solidifies, and the segregation coefficient of this compound in silicon has only 0.01, therefore, in the process of silicon liquid, directional solidification, will be with boron to be come out by fractional condensation from silicon together.Because the segregation coefficient of pure boron is 0.8, therefore, this method is removed effect of boron and will be improved one more than the order of magnitude than method that need not any binding agent.Similar reaction also takes place in this binding agent and phosphorus.In this process, boron and phosphorus all are removed respectively about 90% once more, and phosphorus is removed 99% altogether in the silicon, and boron is removed about 94%.But the silicon ingot of the height of the 10-15% of the top of silicon ingot is the impurity enriched district, will excise in use.
Embodiment:
On behalf of the present invention, the example that the listed parameter of following application example is only used as the present invention be subjected to the restriction of the data in the cited example.For example, time of the composition of the weight of silicon material and impurity component, pressure range, binding agent and ratio and pressurization etc.
Example 1: during work, adopt the silica flour through solid-liquid ion-exchange impurity elimination, the purity of this silicon material is 4N, and the concentration of major impurity is respectively in the silicon: Fe:20ppm, Al:30ppm, Ca:20ppm, B:6ppm, P:20ppm, Ti:6ppm., the granularity of silicon material is 200 orders.
Silica flour is evenly stirred, be charged to afterwards in the mould, the volume of mould is 60 x, 60 x 30mm, and adopting the pressure of pressure die-casting machine is 300 tons.Behind the die cast, the ingot bar that die casting is good withdraws from.So repeatedly, die casting goes out a collection of.
After pressing, ingot bar is swung in quartz crucible, the crucible size is as the criterion with the technology of smelting furnace.This example adopts the crucible of 720 x, 720 x 420mm, after the silica flour ingot bar is occupied, in the vacuum oven of packing into.
After being warmed up to 1450 degree silicon material fusings, melting 5 hours begins directional freeze afterwards, behind the removal impurity layer, and the silicon material that obtains, Fe, Ca, Ti remove substantially fully, adopt icp ms to detect.B drops to 0.8ppm from 6ppm, and P drops to 0.6ppm from 20ppm, and Al is 0.5ppm.
Example 2: most of identical with embodiment 1, difference is:
Carry out batch mixing earlier, with silica flour and binding agent thorough mixing, evenly stir, binding agent is that the compound or the mixture of one or more above-mentioned substances in the materials such as CaO, MgO, BaO, FeO, CaF2, Na2O, SiO2, H2O, Al2O3, NaOH, BaCO3, Ba (OH) 2 and Na2CO3 constitutes, here adopt MgO, BaO, FeO equal proportion mixture, be charged to afterwards in the mould, the volume of mould is 60 x, 60 x 30mm, and adopting the pressure of pressure die-casting machine is 300 tons.Behind the die cast, the ingot bar that die casting is good withdraws from.So repeatedly, die casting goes out a collection of.
After pressing, ingot bar is swung in quartz crucible, the crucible size is as the criterion with the technology of smelting furnace.This example adopts the crucible of 720 x, 720 x 420mm, after the silica flour ingot bar is occupied, in the vacuum oven of packing into.
When being warmed up to the 300 degree left and right sides, there is gas from the silicon material, to overflow.When 900 spent, descending appearred in vacuum tightness once more.After 1450 degree silicon material fusings, melting 5 hours begins directional freeze afterwards.
The resulting silicon material of this technology, Fe, Ca, Ti remove substantially fully, adopt icp ms to detect.B drops to 0.5ppm from 6ppm, and P drops to 0.1ppm from 20ppm, and Al is 0.2ppm.
| Element (ppm) | Silicon (%) | Iron | Aluminium | Calcium | Phosphorus | Boron | Titanium |
| Composition before handling | 99.99 | 20 | 30 | 20 | 20 | 6 | 6 |
| Handle the back composition | 99.9995 | <0.1 | 0.2 | <0.1 | 0.1 | 0.5 | <0.1 |
The silicon materials of the composition in the last table can directly carry out the making of solar cell.
Example 3: during work, adopt the silica flour of handling through simple acidleach, the purity of this silicon material is 3N, and the concentration of major impurity is respectively in the silicon: Fe:120ppm, Al:80ppm, Ca:80ppm, B:8ppm, P:40ppm, Ti:20ppm., silicon material granularity are 100 orders.
Carry out batch mixing earlier, with silica flour and binding agent thorough mixing, evenly stir, binding agent is that the compound or the mixture of one or more above-mentioned substances in the materials such as CaO, MgO, BaO, FeO, CaF2, Na2O, SiO2, H2O, Al2O3, NaOH, BaCO3, Ba (OH) 2 and Na2CO3 constitutes, here adopt SiO2, the H2O mixture of 1:2 ratio to be charged in the mould afterwards, the volume of mould is 30 x, 30 x 10mm, and adopting the pressure of pressure die-casting machine is 60 tons.Behind the die cast, the ingot bar that die casting is good withdraws from.So repeatedly, die casting goes out a collection of.
After pressing, ingot bar is swung in quartz crucible, the crucible size is as the criterion with the technology of smelting furnace.This example adopts the crucible of 600 x, 600 x 320mm, after the silica flour ingot bar is occupied, in the vacuum oven of packing into.
Silicon material temperature is warmed up to 300 degree when above, and vacuum tightness has the decline sign in the furnace charge, and showing has gas to overflow from the silicon material.When 900 spent, descending appearred in vacuum tightness once more.After 1900 degree silicon material fusings, melting 5 hours begins directional freeze afterwards.
The resulting silicon material of this technology, Fe, Ca, Ti remove substantially fully, adopt icp ms to detect.B drops to 1ppm from 6ppm, and P drops to 0.1ppm from 20ppm, and Al is 0.2ppm.
| Element (ppm) | Silicon (%) | Iron | Aluminium | Calcium | Phosphorus | Boron | Titanium |
| Composition before handling | 99.9 | 120 | 80 | 80 | 40 | 8 | 20 |
| Handle the back composition | 99.999 | 0.7 | 1.7 | 0.1 | 1.2 | 1.0 | <0.1 |
The material of last table also can carry out the making of sun power solar cell, but efficient is on the low side.If be used for monocrystal pulling microsection manufacture again, then can be the same substantially with the purity of chemical method.
In sum, provided by the inventionly provide a kind of silicon vacuum smelting purification method that adopts powder metallurgy can avoid causing the loss of silicon material, also cause easily influencing the life-span of vacuum melting equipment in the stove and the pollution of vacuum system; Another purpose provides binding agent, this binding agent can with lack ductility that metal often has and plasticity, hardness height at normal temperatures, fragility is big, and the very big nonmetal crystalline silicon material of the difficulty that causes compression moulding, be easy to moulding, this binding agent not only causes the increasing of impurity in the silicon simultaneously, can also react with existing impurity in the silicon, impurity is wherein separated from silicon, raise the efficiency and purity.
Though the present invention utilizes the foregoing description to carry out at length setting forth, and is not to limit the present invention, any those skilled in the art should do various changes and modification, without departing from the spirit and scope of the present invention, should be considered as protection scope of the present invention.
Claims (5)
1, a kind of silicon vacuum smelting purification method that adopts powder metallurgy, it is characterized in that: the metallurgical silicon vacuum smelting purification method in the confused end of this employing is that powdered silicon material is cast into bulk, puts into equipment that vacuum melting furnace or other be not suitable for placing powder in processing or purify.
2, the silicon vacuum smelting purification method of employing powder metallurgy according to claim 1 is characterized in that: described the silicon material is cast into bulk before, powdered silicon material is added binding agent, and stirs.
3, the silicon vacuum smelting purification method of employing powder metallurgy according to claim 2 is characterized in that: described binding agent is to contain the content that pollutes silicon material impurity to be lower than 0.01% simple substance or compound.
4, the silicon vacuum smelting purification method of employing powder metallurgy according to claim 3 is characterized in that: described binding agent contains aerobic, hydrogen and other solid oxygen element; The oxygen branch that described solid oxygen element contains at high temperature just discharges.
5, the silicon vacuum smelting purification method of employing powder metallurgy according to claim 4 is characterized in that: described binding agent is that the compound or the mixture of one or more above-mentioned substances in the materials such as CaO, MgO, BaO, FeO, CaF2, Na2O, SiO2, H2O, Al2O3, NaOH, BaCO3, Ba (OH) 2 and Na2CO3 constitutes.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102134076A (en) * | 2011-01-25 | 2011-07-27 | 云南乾元光能产业有限公司 | Method for removing boron impurity in metallurgical silicon |
| CN102642836A (en) * | 2012-04-19 | 2012-08-22 | 江苏美科硅能源有限公司 | Powder material charging, furnace feeding, ingot casting and purifying method |
| CN102862988A (en) * | 2011-07-05 | 2013-01-09 | 上海普罗新能源有限公司 | Vacuum solid purification method of silicon by powder metallurgy |
| CN103395788A (en) * | 2013-07-25 | 2013-11-20 | 江西赛维Ldk太阳能高科技有限公司 | Ingot-casting silicon powder with controllable grain size as well as preparation method and application thereof |
| CN104838023A (en) * | 2012-12-10 | 2015-08-12 | 昭和电工株式会社 | MAethod for producing silicon-containing aluminum alloy ingot |
| CN113294997A (en) * | 2021-05-11 | 2021-08-24 | 江苏秦烯新材料有限公司 | Device and method for smelting chloride-containing silicon slag with strong corrosivity |
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2008
- 2008-11-17 CN CNA2008102028222A patent/CN101423221A/en active Pending
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102134076A (en) * | 2011-01-25 | 2011-07-27 | 云南乾元光能产业有限公司 | Method for removing boron impurity in metallurgical silicon |
| CN102134076B (en) * | 2011-01-25 | 2012-09-05 | 云南乾元光能产业有限公司 | Method for removing boron impurity in metallurgical silicon |
| CN102862988A (en) * | 2011-07-05 | 2013-01-09 | 上海普罗新能源有限公司 | Vacuum solid purification method of silicon by powder metallurgy |
| CN102642836A (en) * | 2012-04-19 | 2012-08-22 | 江苏美科硅能源有限公司 | Powder material charging, furnace feeding, ingot casting and purifying method |
| CN104838023A (en) * | 2012-12-10 | 2015-08-12 | 昭和电工株式会社 | MAethod for producing silicon-containing aluminum alloy ingot |
| CN103395788A (en) * | 2013-07-25 | 2013-11-20 | 江西赛维Ldk太阳能高科技有限公司 | Ingot-casting silicon powder with controllable grain size as well as preparation method and application thereof |
| CN103395788B (en) * | 2013-07-25 | 2015-05-20 | 江西赛维Ldk太阳能高科技有限公司 | Ingot-casting silicon powder with controllable grain size as well as preparation method and application thereof |
| CN113294997A (en) * | 2021-05-11 | 2021-08-24 | 江苏秦烯新材料有限公司 | Device and method for smelting chloride-containing silicon slag with strong corrosivity |
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