CN102862988A - Vacuum solid purification method of silicon by powder metallurgy - Google Patents
Vacuum solid purification method of silicon by powder metallurgy Download PDFInfo
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- CN102862988A CN102862988A CN2011101860938A CN201110186093A CN102862988A CN 102862988 A CN102862988 A CN 102862988A CN 2011101860938 A CN2011101860938 A CN 2011101860938A CN 201110186093 A CN201110186093 A CN 201110186093A CN 102862988 A CN102862988 A CN 102862988A
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Abstract
The invention discloses a vacuum solid purification method of silicon by powder metallurgy, comprising the following steps: 1) casting powdery silicon materials into a block, putting the silicon block into a vacuum furnace or a device which is not suitable for receiving powders, conducting vacuum pumping, heating up to 500-1400 DEG C, and preserving the het for 5-25h; 2) cooling to room temperature, then taking out the silicon materials, crushing, and pickling to obtain purified silicon. According to the invention, the loss of the silicon materials in vacuum pumping and pollution of powdery silicon to the furnace and the vacuum system which affect the service life of the vacuum smelting unit can be avoided, and the application of the binding agent is beneficial for separating impurities from silicon, thus the purification purpose can be achieved.
Description
Technical field
The present invention relates to a kind of silicon method of purification, particularly relate to a kind of silicon vacuum solid method of purification that adopts powder metallurgy.
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 first Pure Silicon Metal to be pulverized, afterwards with acid or alkali or other solution and silica flour reaction, because the area change of the silicon material after pulverizing, 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 most of metallic impurity in the silicon with lower cost, and still, this method is difficult to remove the nonmetallic impurity in the silicon, especially phosphorus and boron etc.
For except dephosphorization and boron, also to adopt the method for the solid-state or liquid purification of high-temperature vacuum.But, through the silica flour after the solid-liquid ion-exchange, because granularity is less, after putting into vacuum oven, be easy to be extracted out outside the stove by vacuum, not only cause the loss of silicon material, also easily cause affecting the life-span of vacuum smelting equipment in the stove and the pollution of vacuum system.
At present, the existing mode that adopts compression moulding is processed the precedent that metal and other non-metallic minerals are purified, and still, also nobody adopted same mode to the silicon material.And by adding the mode of suitable binding agent, both helped the silicon material fixed, and avoid the loss of silicon material, can assist again removal impurity, nobody delivered same method more.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of silicon vacuum solid method of purification that adopts powder metallurgy.By with making bulk after the pulverizing of Pure Silicon Metal process and the wet purification, enter again vacuum oven and carry out solid-state purification, can obtain solar energy level silicon.
For solving the problems of the technologies described above, the silicon vacuum solid method of purification of employing powder metallurgy of the present invention comprises:
(1) the silicon material with powdery is cast into bulk, puts into vacuum oven or other is not suitable for placing the equipment of powder, vacuumizes, and is heated to 500～1400 ℃, and is incubated 5～25 hours;
(2) be cooled to room temperature after, the silicon material is taken out, broken, pickling removing the reactant of particle surface, thereby reach the purpose of removal of impurities, obtain at last the silicon of purifying, i.e. solar energy level silicon.
In the described step (1), before the silicon material of powdery is cast into bulk, can in the silicon material of powdery, adds binding agent, and stir.Wherein, binding agent is lower than 0.01% simple substance or compound for the content that pollutes silicon material impurity; The binding agent that preferably contains aerobic, hydrogen or other solid oxygen element wherein, Gu the oxygen that oxygen element contains divides, at high temperature just discharges; Especially preferred, binding agent is selected from: CaO, MgO, FeO, CaF
2, Na
2O, SiO
2, H
2O, Al
2O
3, NaOH and Na
2CO
3Deng in the material one or more.The additional proportion scope of silicon material and binding agent is: binding agent accounts for 10%～50% of cumulative volume.
In the described step (1), vacuum tightness is 0.1～10Pa.
Pickling in the described step (2) comprises: carry out acidity with hydrofluoric acid, wherein, the mass concentration of hydrofluoric acid is 5%～20%; Fragmentation in the step (2) is the granular size that is crushed to used silicon material.
The present invention puts into vacuum oven again by with silicon material die cast, can avoid causing in vacuum the loss of silicon material and silica flour in the stove and the pollution of vacuum system, affects the life-span of vacuum smelting equipment.
In addition, the present invention also adopts binding agent, make silicon material die cast, on the one hand, this binding agent will help hardening of silica flour and grumeleuse, reduces the powder on surface, on the other hand, because the relation of purifying, the binding agent that adds 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, hardness is high, 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, mutually extruding 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, with causing the very difficult removal of impurity, bring difficulty to subsequent purification.For this reason, the tackiness agent that the present invention is first selected requires purity more than 99.99%.
In silicon, several elements are arranged, such as elements such as Al, B, P because in the periodic table of elements, be positioned at element silicon around, character and the silicon of simple substance element at high temperature are very approaching, therefore, relatively are difficult to remove.Take the B element as example, adopt vacuum melting, the fusing point of B also high more than 1000 is spent than silicon; Adopt directional freeze, the segregation coefficient of B in silicon is 0.8, and approached in 10 minutes, therefore, almost can not be by solid-liquid separation when directional freeze.And at high temperature the saturated vapor pressure of B is 10
-4The order of magnitude of pa, than little two orders of magnitude of silicon, therefore, vacuum outgas also can't allow B volatilize.Therefore, B is a kind of element of separating and removing of extremely being difficult in silicon.Therefore, had better not contain these elements in the binding agent.
Binding agent of the present invention when easily condensing, has also played the effect of the reagent under vacuum when impelling silica flour in compression moulding.When vacuum solid is incubated, partial impurities in the silicon material and the element of binding agent form gaseous oxygen compound or other compound and volatilize in high-temperature vacuum, another part solid reaction products rests between silicon grain and the particle, is removed in subsequently fragmentation, acid cleaning process.
Binding agent of the present invention is by CaO, MgO, FeO, CaF
2, Na
2O, SiO
2, H
2O, Al
2O
3, NaOH, Na
2CO
3A kind of Deng in the material, or the compound of several materials or mixture consist of.For different impurity, selected binding agent is different.In addition, too large such 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 removal of impurities reactant, because in the situation that powder has carried out good the mixing with silica flour, very large with the contact area of silicon, therefore, when carrying out the high-temperature vacuum insulation, can fully react with the impurity on silicon grain surface, simultaneously, the impurity in the silicon grain to silicon face diffusion and lasting and binding agent reaction, plays the effect that impurity elimination is purified owing to the existence of concentration gradient to greatest extent.
For example, pass into the reaction of oxygen and boron and generate boron oxide compound, then at high temperature volatilization 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 occur 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, until under the high temperature, oxygen just disengages, react with boron in the silicon, form boron trioxide, under vacuum and high temperature, volatilize, thereby reach further except boron, simultaneously, contained protium can prevent the oxidation of silicon, thereby can reduce again the purpose of silicon material loss.Not only fully impurity elimination is purified, and can also play energy-conservation effect.
The tackiness agent that the present invention adds 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 larger than boron, and in the process of volatilization, boron also is pulled away.In this process, can eliminate about 60% phosphorus and 30% boron.
Therefore, in the method for the present invention, be heated to a certain temperature that is lower than silicon material fusing point and keep certain hour, in whole purification process, keep certain vacuum tightness, the gaseous compound that the reaction of impurity in the silicon material and binding agent is formed is constantly taken away, simultaneously, binding agent can make and lack at normal temperatures ductility and the plasticity that metal often has, hardness is high, fragility is large, cause the very large nonmetal crystalline silicon material of difficulty of compression moulding to be easy to moulding, this binding agent not only can not cause the increasing of impurity in the silicon simultaneously, can also react with existing impurity in the silicon, impurity is wherein separated from silicon, reach the purpose of purification.
Embodiment
The example that the listed parameter of following application example is only used as the present invention does not represent the restriction that the present invention is subjected to 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.
Following examples all adopt the silica flour through solid-liquid ion-exchange impurity elimination, and the purity of this silica flour 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 silica flour is 200 orders.
Tackiness agent in following examples, purity is more than 99.99%.
Embodiment 1
Silica flour is fully mixed with binding agent, uniform stirring, wherein, binding agent is MgO, FeO, CaF
2The mixture of equal proportion, and binding agent accounts for 10% of cumulative volume, is charged to afterwards in the mould, and the volume of mould is 60 * 60 * 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, after the silica flour ingot bar is occupied, in the vacuum oven of packing into, vacuumize, vacuum tightness is 0.1Pa.
After being warmed up to 500 ℃, be incubated 25 hours, then furnace cooling is to room temperature, the silica flour ingot bar is taken out carry out fragmentation (being crushed to the granular size of used silicon material), be after 5% hydrofluoric acid cleans 12 hours, to obtain the silicon material with mass concentration.
With the silicon material that obtains, detect through icp ms, can't detect Fe, Ca, Ti, illustrate that namely Fe, Ca, Ti remove substantially fully, and detect: B drops to 0.8ppm from 6ppm, and P drops to 0.6ppm from 20ppm, and Al is 0.5ppm.Therefore, can obtain solar energy level silicon.
Embodiment 2
Carry out first batch mixing, silica flour is fully mixed with binding agent, uniform stirring, wherein, binding agent is MgO, FeO, Na
2CO
3The equal proportion mixture, and binding agent accounts for 20% of cumulative volume, is charged to afterwards in the mould, the volume of mould is 60 * 60 * 30mm, 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, after the silica flour ingot bar is occupied, in the vacuum oven of packing into, vacuumize, vacuum tightness is 2Pa.
After being warmed up to 1000 ℃, be incubated 15 hours.Then furnace cooling is to room temperature, and the silica flour ingot bar is taken out carry out fragmentation, be after 10% hydrofluoric acid cleans 8 hours, to obtain the silicon material with mass concentration.
With the silicon material that obtains, detect through icp ms, can't detect Fe, Ca, Ti, illustrate that namely Fe, Ca, Ti remove substantially fully, and detect: B drops to 0.5ppm from 6ppm, and P drops to 0.3ppm from 20ppm, and Al is 0.2ppm.Therefore, can obtain solar energy level silicon.
Embodiment 3
Silica flour is fully mixed with binding agent, uniform stirring, wherein, binding agent is that weight ratio is 1: 2 SiO
2, H
2O mixture, binding agent account for 30% of cumulative volume, are charged to afterwards in the mould, and the volume of mould is 30 * 30 * 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, after the silica flour ingot bar is occupied, in the vacuum oven of packing into, vacuumize, vacuum tightness is 5Pa.
After silicon material temperature degree is warmed up to 1400 ℃, be incubated 5 hours.Then furnace cooling is to room temperature, and the silica flour ingot bar is taken out carry out fragmentation, be after 15% hydrofluoric acid cleans 5 hours, to obtain the silicon material with mass concentration.
With the silicon material that obtains, detect through icp ms, can't detect Fe, Ca, Ti, illustrate that namely Fe, Ca, Ti remove substantially fully, and detect: B drops to 1ppm from 6ppm, and P drops to 0.1ppm from 20ppm, and Al is 0.2ppm.Therefore, can obtain solar energy level silicon.
Embodiment 4
Silica flour is fully mixed with binding agent, uniform stirring, wherein, binding agent is CaO, Na
2O, Al
2O
3, the NaOH equal proportion mixture, binding agent accounts for 50% of cumulative volume, is charged to afterwards in the mould, the volume of mould is 60 * 60 * 30mm, 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, after the silica flour ingot bar is occupied, in the vacuum oven of packing into, vacuumize, vacuum tightness is 10Pa.
After being warmed up to 500 ℃, be incubated 25 hours, then furnace cooling is to room temperature, the silica flour ingot bar is taken out carry out fragmentation, be after 20% hydrofluoric acid cleans 2 hours, to obtain the silicon material with mass concentration.
With the silicon material that obtains, detect through icp ms, can't detect Fe, Ca, Ti, illustrate that namely Fe, Ca, Ti remove substantially fully, and detect: B drops to 0.8ppm from 6ppm, and P drops to 0.6ppm from 20ppm, and Al is 0.5ppm.Therefore, can obtain solar energy level silicon.
Although the present invention utilizes above-described embodiment 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 (10)
1. silicon vacuum solid method of purification that adopts powder metallurgy comprises:
(1) the silicon material with powdery is cast into bulk, puts into vacuum oven or is not suitable for placing the equipment of powder, vacuumizes, and is heated to 500～1400 ℃, and is incubated 5～25 hours;
(2) be cooled to room temperature after, the silicon material is taken out broken, pickling, the silicon that obtains purifying.
2. the method for claim 1 is characterized in that: in the described step (1), before the silicon material of powdery is cast into bulk, adds binding agent in the silicon material of powdery, and stir; Wherein, binding agent accounts for 10%～50% of cumulative volume.
3. method as claimed in claim 2 is characterized in that: described binding agent is lower than 0.01% simple substance or compound for the content that pollutes silicon material impurity.
4. method as claimed in claim 3 is characterized in that: described binding agent is the binding agent that contains aerobic, hydrogen or solid oxygen element, wherein, Gu the oxygen that oxygen element contains divides, at high temperature just discharges.
5. method as claimed in claim 4, it is characterized in that: described binding agent is selected from: CaO, MgO, FeO, CaF
2, Na
2O, SiO
2, H
2O, Al
2O
3, NaOH, Na
2CO
3In one or more.
6. the method for claim 1, it is characterized in that: in the described step (1), vacuum tightness is 0.1～10Pa.
7. the method for claim 1, it is characterized in that: the pickling in the described step (2) comprises: carry out acidity with hydrofluoric acid.
8. method as claimed in claim 7, it is characterized in that: the mass concentration of described hydrofluoric acid is 5%～20%.
9. the method for claim 1, it is characterized in that: the fragmentation in the described step (2) is the granular size that is crushed to used silicon material.
10. the method for claim 1, it is characterized in that: in the described step (2), the silicon of purification is solar energy level silicon.
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Citations (4)
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|---|---|---|---|---|
| CN201056060Y (en) * | 2007-06-13 | 2008-05-07 | 浙江昱辉阳光能源有限公司 | Silica flour cake pressing device |
| CN101423221A (en) * | 2008-11-17 | 2009-05-06 | 上海普罗新能源有限公司 | Silicon vacuum smelting purification method employing powder metallurgy |
| CN101671026A (en) * | 2009-09-29 | 2010-03-17 | 包头市山晟新能源有限责任公司 | Pickling impurity removal method and equipment and method and system for purifying polysilicon |
| CN101844768A (en) * | 2010-05-20 | 2010-09-29 | 厦门大学 | Method for removing phosphorus and boron from metallurgical-grade silicon |
-
2011
- 2011-07-05 CN CN2011101860938A patent/CN102862988A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201056060Y (en) * | 2007-06-13 | 2008-05-07 | 浙江昱辉阳光能源有限公司 | Silica flour cake pressing device |
| CN101423221A (en) * | 2008-11-17 | 2009-05-06 | 上海普罗新能源有限公司 | Silicon vacuum smelting purification method employing powder metallurgy |
| CN101671026A (en) * | 2009-09-29 | 2010-03-17 | 包头市山晟新能源有限责任公司 | Pickling impurity removal method and equipment and method and system for purifying polysilicon |
| CN101844768A (en) * | 2010-05-20 | 2010-09-29 | 厦门大学 | Method for removing phosphorus and boron from metallurgical-grade silicon |
Non-Patent Citations (1)
| Title |
|---|
| J.C.S.PIRES ET AL.: "The purification of metallurgical grade silicon by electron beam melting", 《JOURNAL OF MATERIALS PROCESSING TECHNOLOGY》 * |
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Application publication date: 20130109 |