CN103553049B - The medium melting being applied to polycrystalline silicon purifying is connected preliminary directional solidification processes - Google Patents
The medium melting being applied to polycrystalline silicon purifying is connected preliminary directional solidification processes Download PDFInfo
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Abstract
The invention belongs to field of polycrystalline silicon purification, be specifically related to a kind of medium melting being applied to polycrystalline silicon purifying and be connected preliminary directional solidification processes, comprise medium melting, silico briquette to be purified and slag agent are reacted, the boron impurity of going out in silicon, after it is characterized in that medium melting terminates, is placed in the preliminary apparatus for directional solidification under atmospheric condition by silicon liquid, adopt the mode of the cold drawn ingot of bottom water, the metallic impurity in silicon liquid are gathered top and is removed.The invention has the advantages that the cycle is short, production efficiency is high, and technique is simple, and save energy, cost is low.
Description
Technical field
The invention belongs to field of polycrystalline silicon purification, be specifically related to a kind of medium melting being applied to polycrystalline silicon purifying and be connected preliminary directional solidification processes.
Background technology
World today's energy dilemma and environmental pollution pressure are also deposited, and people are badly in need of cleaning, safety, continuable new forms of energy.Sun power, as meeting the energy required like this, always is the target that people pursue.People are the utilizations of its heat effect to the use of sun power the earliest, but are difficult to the needs meeting modern society completely.Until the discovery of photoresistance, the manufacture of solar cell, the Land use systems that people find sun power new.Silicon is as the most desirable feedstock of solar cell, impurity wherein mainly contains the nonmetallic impuritys such as metallic impurity and B, P such as Fe, Al, Ca, and these impurity elements can reduce the Compound Degree of silicon crystal grain interface photo-generated carrier, and the Compound Degree of photo-generated carrier determines the photoelectric transformation efficiency of solar cell, removing these impurity so effective has vital effect in the application aspect of solar cell.
The development of solar photovoltaic industry depends on the purification to polycrystalline silicon raw material.The purifying technique of polycrystalline silicon raw material mainly relies on following several technique at present: Siemens Method, silane thermal decomposition process, gas fluidized bed process and metallurgy method.Wherein, metallurgy method has development potentiality because possessing simple, the lower-cost advantage of technique.At present, metallurgy method technique mainly contains four large process procedures, medium melting, directional freeze, electron beam melting and ingot casting.
In traditional metallurgy method technical process, medium melting technology can only remove the B impurity in polysilicon, removal effect is not had for metallic impurity, and a large amount of metallic impurity bring very large pressure can to follow-up directional solidification processes, therefore directional freeze process often needs repetition 1 ~ 2 time, causes larger spending cost.Silicon liquid after medium melting all needs through process of setting, in silicon ingot after natural coagulation process, owing to there is not thermograde in process of cooling, therefore there is not gradient in the distribution of metallic impurity, metallic impurity and silicon ingot cannot be separated, epidermis still needs to remove the impurity removal process that just can carry out next step simultaneously.
Summary of the invention
According to above the deficiencies in the prior art, the present invention proposes a kind of medium melting being applied to polycrystalline silicon purifying and is connected preliminary directional solidification processes, preliminary directional freeze is added between medium melting and directional freeze two process procedures, thus remove most of metallic impurity, alleviate the pressure of follow-up directional freeze, only need carry out a directional freeze.
A kind of medium melting being applied to polycrystalline silicon purifying of the present invention is connected preliminary directional solidification processes, comprise medium melting, silico briquette to be purified and slag agent are reacted, boron impurity in removing silicon, after medium melting terminates, silicon liquid is placed in the preliminary apparatus for directional solidification under atmospheric condition, adopts the mode of the cold drawn ingot of bottom water, the metallic impurity in silicon liquid are gathered top and is removed.
Preferred version of the present invention is as follows: preferably include following steps:
(1) medium melting: the plumbago crucible in Medium Frequency Induction Heating Furnace adds the slag agent and whole silico briquette to be purified that account for slag agent total mass 20%, controlling heating power makes it all melt, then divide and add residue slag agent for 3 ~ 5 times and carry out melting, smelting temperature is 1600 ~ 1800 DEG C, the smelting time at every turn added is 20 ~ 30min, pours in heat resisting iron mould after melting by old for upper strata slag; Repeat above-mentioned medium fusion process 1 ~ 3 time, the new slag agent at every turn added divides 2 ~ 5 times and adds;
(2) preliminary directional freeze: after last medium melting is terminated, the old slag accounting for old slag total mass 80 ~ 90% is poured in heat resisting iron mould, then silicon liquid and the old slag of residue being poured in preliminary apparatus for directional solidification is preheating in the plumbago crucible of 1000 ~ 1300 DEG C in advance, under this preliminary apparatus for directional solidification is placed in atmospheric condition, adjustment ruhmkorff coil power, on plumbago crucible, induction generation electric current makes plumbago crucible continue intensification of being heated, controlling silicon liquid temp is 1450 ~ 1550 DEG C, melting 10 ~ 30min, then the water-cooled ingot pulling mechanism started bottom plumbago crucible starts to draw ingot, ingot direction is drawn to be downwards away from the furnace lining direction of plumbago crucible outer wall, stop when excess silicon liquid in plumbago crucible is initial silicon liquid total mass 10 ~ 20% drawing ingot, supernatant liquid is poured in cast iron die, remainder stove is chilled to room temperature, namely obtain 4N(4N after taking-up silicon ingot effects on surface does sandblasting and refer to that silicone content is more than 99.99%) silicon ingot.
Wherein, in step (1), silico briquette to be purified is preferably metallurgical grade silicon, and in described metallurgical grade silicon, silicone content is 97.0 ~ 99.9wt%, and boron impurities content is 10 ~ 20ppmw.
In step (1), in each medium fusion process, the mass ratio of silicon liquid and slag agent is preferably 0.5 ~ 3:1.
Plumbago crucible in step (1) in Medium Frequency Induction Heating Furnace adds the slag agent and whole silico briquette to be purified that account for slag agent total mass 20%, preferably controls heating power 200 ~ 300KW and makes it all melt.
Ingot speed of drawing in step (2) is preferably 4 ~ 6cm/h, owing to being preliminary directional freeze, instead of strict directional freeze, so draw ingot speed, make it complete in the short period of time, improve whole work efficiency.
Furnace lining in step (2) is preferably made by refractory mortar.The effect of furnace lining is the effect playing insulation, is drawing in ingot process, and the plumbago crucible of pull-out furnace lining part can dispel the heat in a large number, thus causes thermograde, and metallic impurity are upwards assembled.
In the present invention, preliminary apparatus for directional solidification is different from proper apparatus for directional solidification, is in atmospheric conditions, instead of under vacuum condition; Be not incubated sleeve, but substitute insulation effect with furnace lining; Because heat insulation effect is not obvious, so directional solidification effect is general, but most of metallic impurity can be removed equally, alleviate the pressure of directional freeze.In addition, when the silicon liquid after medium melting being terminated pours the plumbago crucible in preliminary apparatus for directional solidification into, also can pour the old slag of a small part into, object is that old slag can float on silicon liquid surface, plays the effect of isolated air, prevents silicon liquid oxidation.The silicon liquid that this part old slag last can follow residue 10 ~ 20% is discharged together, and this part silicon liquid remaining can containing a large amount of metallic impurity.
The invention has the advantages that: (1) is by combining medium melting with preliminary Rapid Directional Solidification technique, on the basis of removing boron impurity, also most of metallic impurity can be removed, boron impurities content in silicon material is made to be less than 0.3ppmw, thus silicon ingot reaches more than 4N level, greatly shorten the purification number of times of follow-up directional solidification processes, reduce and produce pressure, save energy; (2) in preliminary Rapid Directional Solidification process, under liquid state, top impurity enriched part is poured out, save and solidify rear tailing removal process, avoid wastage of material; (3) complete two kinds of liquid techniques are connected, and can save power consumption 3000 ~ 4000 KWhs/ton, make medium melting production cost reduce by 2000 ~ 3000 yuan/ton, and can realize continuous prodution.
Embodiment
Below in conjunction with embodiment, the present invention is described further.
Embodiment 1:
(1) select materials: silico briquette 600kg to be purified is metallurgical grade silicon, in described metallurgical grade silicon, silicone content is 97.0 ~ 99.9wt%, and boron impurities content is 10 ~ 20ppmw.Conventional silico-calcium system slag former is selected in slag agent, and total amount is 2400kg, is divided into two parts, and as twice medium fusion process, thus in each medium fusion process, white residue ratio is 0.5:1.
(2) medium melting: the plumbago crucible in Medium Frequency Induction Heating Furnace adds the agent of 240kg slag and whole silico briquette to be purified, controlling heating power 250KW makes it all melt, then divide and add residue slag agent for 5 times and carry out melting, smelting temperature is 1600 DEG C, the smelting time at every turn added is 20min, pours in heat resisting iron mould after melting by old for upper strata slag; Repeat above-mentioned medium fusion process 1 time, the new slag agent at every turn added divides 5 times and adds;
(3) preliminary directional freeze: after last medium melting terminates, the old slag accounting for old slag total mass 80% is poured in heat resisting iron mould, then silicon liquid and the old slag of residue being poured in preliminary apparatus for directional solidification is preheating in the plumbago crucible of 1300 DEG C in advance, under this preliminary apparatus for directional solidification is placed in atmospheric condition, adjustment ruhmkorff coil power, on plumbago crucible, induction generation electric current makes plumbago crucible continue intensification of being heated, controlling silicon liquid temp is 1550 DEG C, melting 30min, then the water-cooled ingot pulling mechanism started bottom plumbago crucible starts to draw ingot, ingot direction is drawn to be downwards away from the furnace lining direction of plumbago crucible outer wall, wherein, furnace lining selects refractory mortar to make, ingot speed is drawn to be 4cm/h.Stop when excess silicon liquid in plumbago crucible is initial silicon liquid total mass 15% drawing ingot, poured into by supernatant liquid in cast iron die, remainder stove is chilled to room temperature, takes out after silicon ingot effects on surface does sandblasting and namely obtains high-quality 4N silicon ingot.
Embodiment 2:
(1) select materials: silico briquette 600kg to be purified is metallurgical grade silicon, in described metallurgical grade silicon, silicone content is 97.0 ~ 99.9wt%, and boron impurities content is 10 ~ 20ppmw.Conventional silico-calcium system slag former is selected in slag agent, and total amount is 1000kg, is divided into five parts, and as five medium fusion process, thus in each medium fusion process, white residue ratio is 3:1.
(2) medium melting: the plumbago crucible in Medium Frequency Induction Heating Furnace adds the agent of 40kg slag and whole silico briquette to be purified, controlling heating power 300KW makes it all melt, then divide and add residue slag agent for 3 times and carry out melting, smelting temperature is 1800 DEG C, the smelting time at every turn added is 30min, pours in heat resisting iron mould after melting by old for upper strata slag; Repeat above-mentioned medium fusion process 4 times, the new slag agent at every turn added divides 4 times and adds;
(3) preliminary directional freeze: after last medium melting is terminated, the old slag accounting for old slag total mass 90% is poured in heat resisting iron mould, then silicon liquid and the old slag of residue being poured in preliminary apparatus for directional solidification is preheating in the plumbago crucible of 1000 DEG C in advance, under this preliminary apparatus for directional solidification is placed in atmospheric condition, adjustment ruhmkorff coil power, on plumbago crucible, induction generation electric current makes plumbago crucible continue intensification of being heated, controlling silicon liquid temp is 1450 DEG C, melting 20min, then the water-cooled ingot pulling mechanism started bottom plumbago crucible starts to draw ingot, ingot direction is drawn to be downwards away from the furnace lining direction of plumbago crucible outer wall, wherein, furnace lining selects refractory mortar to make, ingot speed is drawn to be 6cm/h.Stop when excess silicon liquid in plumbago crucible is initial silicon liquid total mass 20% drawing ingot, poured into by supernatant liquid in cast iron die, remainder stove is chilled to room temperature, takes out after silicon ingot effects on surface does sandblasting and namely obtains high-quality 4N silicon ingot.
Claims (6)
1. the medium melting being applied to polycrystalline silicon purifying is connected preliminary directional solidification processes, comprise medium melting, silico briquette to be purified and slag agent are reacted, boron impurity in removing silicon, after it is characterized in that medium melting terminates, silicon liquid is placed in the preliminary apparatus for directional solidification under atmospheric condition, adopts the mode of the cold drawn ingot of bottom water, the metallic impurity in silicon liquid are gathered top and is removed;
Specifically comprise the following steps:
(1) medium melting: the plumbago crucible in Medium Frequency Induction Heating Furnace adds the slag agent and whole silico briquette to be purified that account for slag agent total mass 20%, controlling heating power makes it all melt, then divide and add residue slag agent for 3 ~ 5 times and carry out melting, smelting temperature is 1600 ~ 1800 DEG C, the smelting time at every turn added is 20 ~ 30min, pours in heat resisting iron mould after melting by old for upper strata slag; Repeat above-mentioned medium fusion process 1 ~ 3 time, the new slag agent at every turn added divides 2 ~ 5 times and adds;
(2) preliminary directional freeze: after last medium melting is terminated, the old slag accounting for old slag total mass 80 ~ 90% is poured in heat resisting iron mould, then silicon liquid and the old slag of residue being poured in preliminary apparatus for directional solidification is preheating in the plumbago crucible of 1000 ~ 1300 DEG C in advance, under this preliminary apparatus for directional solidification is placed in atmospheric condition, adjustment ruhmkorff coil power, on plumbago crucible, induction generation electric current makes plumbago crucible continue intensification of being heated, controlling silicon liquid temp is 1450 ~ 1550 DEG C, melting 10 ~ 30min, then the water-cooled ingot pulling mechanism started bottom plumbago crucible starts to draw ingot, ingot direction is drawn to be downwards away from the furnace lining direction of plumbago crucible outer wall, stop when excess silicon liquid in plumbago crucible is initial silicon liquid total mass 10 ~ 20% drawing ingot, supernatant liquid is poured in cast iron die, remainder stove is chilled to room temperature, take out after silicon ingot effects on surface does sandblasting and namely obtain 4N silicon ingot.
2. the medium melting being applied to polycrystalline silicon purifying according to claim 1 is connected preliminary directional solidification processes, it is characterized in that in step (1), silico briquette to be purified is metallurgical grade silicon, in described metallurgical grade silicon, silicone content is 97.0 ~ 99.9wt%, and boron impurities content is 10 ~ 20ppmw.
3. the medium melting being applied to polycrystalline silicon purifying according to claim 1 is connected preliminary directional solidification processes, it is characterized in that the mass ratio of silicon liquid and slag agent in each medium fusion process in step (1) is 0.5 ~ 3:1.
4. the medium melting being applied to polycrystalline silicon purifying according to claim 1 is connected preliminary directional solidification processes, it is characterized in that the plumbago crucible in step (1) in Medium Frequency Induction Heating Furnace adds the slag agent and whole silico briquette to be purified that account for slag agent total mass 20%, control heating power 200 ~ 300KW and make it all melt.
5. the medium melting being applied to polycrystalline silicon purifying according to claim 1 is connected preliminary directional solidification processes, it is characterized in that the ingot speed of drawing in step (2) is 4 ~ 6cm/h.
6. the medium melting being applied to polycrystalline silicon purifying according to claim 1 is connected preliminary directional solidification processes, it is characterized in that the furnace lining in step (2) selects refractory mortar to make.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102602933A (en) * | 2011-01-20 | 2012-07-25 | 江西开昂新能源科技有限公司 | Polycrystalline silicon purifying device and method |
| CN102849743A (en) * | 2012-09-25 | 2013-01-02 | 青岛隆盛晶硅科技有限公司 | Polysilicon purification method and device by reverse induced solidification |
| CN103072997A (en) * | 2013-02-04 | 2013-05-01 | 福建兴朝阳硅材料股份有限公司 | Method and device for removing metal impurities in polycrystalline silicon |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102602933A (en) * | 2011-01-20 | 2012-07-25 | 江西开昂新能源科技有限公司 | Polycrystalline silicon purifying device and method |
| CN102849743A (en) * | 2012-09-25 | 2013-01-02 | 青岛隆盛晶硅科技有限公司 | Polysilicon purification method and device by reverse induced solidification |
| CN103072997A (en) * | 2013-02-04 | 2013-05-01 | 福建兴朝阳硅材料股份有限公司 | Method and device for removing metal impurities in polycrystalline silicon |
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