CN103073000A - Method for removing boron through plasma auxiliary slagging - Google Patents
Method for removing boron through plasma auxiliary slagging Download PDFInfo
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- CN103073000A CN103073000A CN2013100464355A CN201310046435A CN103073000A CN 103073000 A CN103073000 A CN 103073000A CN 2013100464355 A CN2013100464355 A CN 2013100464355A CN 201310046435 A CN201310046435 A CN 201310046435A CN 103073000 A CN103073000 A CN 103073000A
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Abstract
The invention relates to a method for removing boron through plasma auxiliary slagging. The method comprises the following steps of heating a silicon block in a medium-frequency induction furnace graphite crucible, and dissolving the silicon block into silicon liquid; adding a slagging agent into the silicon liquid, continuously heating the silicon liquid until the slagging agent is completely melted, and keeping the temperature of the silicon liquid, wherein the slagging agent consists of Na2CO3, K2CO3 and SiO2; preheating a graphite rod with a vent, after the graphite rod is fully preheated, inserting a ventilating rod into the silicon liquid, and introducing oxygen; meanwhile, starting a high-pressure plasma generator, ionizing the oxygen in an oxygen passage into oxygen ions at the room temperature, and filling the oxygen ions into the silicon liquid through the graphite rod; and filling the silicon liquid into a temperature-keeping furnace to be solidified, and after a silicon ingot is cooled, removing slag blocks on the surface of the silicon ingot. By the method, the slag amount can be effectively reduced, silicon loss caused when silicon is wrapped in slag is reduced, the cost for purifying polycrystalline silicon is reduced, the content of boron in refined low-boron polycrystalline silicon obtained after purification is relatively low, and the boron-removing effect is good.
Description
Technical field
The present invention relates to a kind of polycrystalline silicon purifying technical field, particularly relate to the novel method of the auxiliary slagging boron removal of a kind of plasma.
Background technology
Energy dilemma and traditional energy have become the main restricting factor of society and the national economic development to the pollution of environment.For keeping Sustainable development, all actively readjusting the energy structure in countries in the world, greatly develops renewable energy source, and polysilicon solar cell becomes the focus of global concern.The technique that the employing improved Siemens prepares high purity polycrystalline silicon is comparatively complicated, and cost of investment is high, will greatly increase the battery price with its preparation solar cell.And metallurgy method purifying polycrystalline silicon technique is relatively simple, and is with low cost, and to the less that pollutes of environment, become the main development direction of solar-grade polysilicon.
Polycrystalline silicon purifying is mainly removed impurity element wherein, such as Al, Fe, C, P, B etc., and the non-metallic elements such as P, B are difficult for removing, boron particularly, because the segregation coefficient of boron in silicon is 0.8, close to 1, and saturation steam forces down, and removes by traditional directional freeze or vacuum melting to reach requirement.And the content of boron impurity has a great impact the performance of solar cell, requires boron content not to be higher than 0.3ppm, the study hotspot that therefore to explore various effective low-cost boron removal methods are polycrystalline silicon purifyings.At present mainly by the boron impurity in the techniques such as air blowing, slag making, plasma body, the directional freeze removal silicon.
Patent CN102452651A discloses the technique that a kind of wet oxygen plasma body is removed boron impurity in the silicon, form oxygen containing wet oxygen plasma flame by radio-frequency (RF) plasma reactor, silicon liquid surface is purged, although present method is feasible, can effectively reduce the content of boron from industrial silicon, but still have following problem on industrial application: at first, the removal effect of boron is the difficult purity requirement that reaches solar-grade polysilicon still.Secondly, the high-temperature plasma flame temperature is high, and the silicon loss is large, and apparatus expensive, is not suitable for industrial scale operation.
US Patent No. 5788945 discloses and has a kind ofly helped the method for slag agent by continuous adding in silicon liquid, and helping slag agent composition is 60%CaO and 40%SiO2, and boron drops to 1ppmw from 40ppmw.This method that helps the slag agent that adds continuously because it is more to wrap up in silicon in the slag, causes the silicon loss large, and helps the consumption of slag agent relatively too high in the slagging process, causes cost to increase, and silicon also can produce certain metallic pollution simultaneously.
Patent CN102320610A discloses the refining of a kind of high frequency electromagnetically induced, repeatedly the polysilicon of slag making takes off the boron method of purification in batches, slag former is that Na2CO3 and SiO2 mix according to weight ratio 1:1, adopt the refining of this high frequency electromagnetically induced, repeatedly the polysilicon of slag making takes off the boron method of purification in batches, although can make the content of boron below 0.1ppm, satisfy the high purity requirement of solar-grade polysilicon, but since slagging process in except effect of boron be not fine, the slag former consumption is relatively too high, cause cost to increase, and more owing to wrapping up in silicon in the slag, cause the silicon loss large.
Summary of the invention
The object of the present invention is to provide the novel method that a kind of technique is simple, cost is low, the high pressure plasma of suitable Industry Promotion is assisted slagging boron removal, the method adopts first intermediate frequency furnace induction heating industrial silicon in plumbago crucible, then in silicon liquid, add slag former, the fusing reaction, and adopt graphite rod in silicon liquid, to lead to the oxygen stirring; Open ion generator, partial oxidation is ionized into oxonium ion is directly injected into and carries out refining in the silicon liquid.By the mode that plasma and slag making combine, significantly reduce the content of boron in the silicon, after cooling, remove the refining low boron polysilicon after silicon silicon ingot surface clinker can obtain purifying.The inventive method has solved that the slag former consumption is high, the problem of high-temperature plasma apparatus expensive, has reduced cost, is convenient to industrialization and uses.
In order to realize purpose of the present invention, the following technical scheme of special employing:
The method of the auxiliary slagging boron removal of a kind of high pressure plasma may further comprise the steps:
(1) silico briquette is packed into heats in the medium-frequency induction furnace plumbago crucible, and be fused into silicon liquid;
(2) in silicon liquid, drop into slag former, continue heating slag former is melted fully, and keep the silicon liquid temp; Described slag former is by Na
2CO
3, K
2CO
3With SiO
2Form;
(3) will after preheating fully, venting pin be inserted in the silicon liquid with the graphite rod preheating of vent channel, begin logical oxygen;
(4) open simultaneously the high-pressure ion producer, at room temperature the oxygen in the oxygen channel is ionized into oxonium ion also by in the graphite rod Implanted Silicon liquid;
(5) the silicon liquid that obtains in the step (4) is injected holding furnace and solidify, after the silicon ingot cooling, remove silicon ingot surface clinker, the refining low boron polysilicon after obtaining purifying.
High-temperature plasma is that the boron in the silicon is become the effusion of lower boiling boron compound gas except boron, and slagging boron removal is boron to be oxidized to boron oxide enter slag system and remove.The method of the auxiliary slagging boron removal of high pressure plasma provided by the invention, at first adopting the cryogenic high pressure plasma method that partial oxidation is ionized into oxonium ion is directly injected in the silicon liquid, increased the concentration of oxonium ion in the silicon liquid, can effectively reduce the quantity of slag, reduce the silicon loss that causes because wrap up in silicon in the slag, and the selected high pressure plasma generator apparatus of present method is simple, cost is low, easy use, and the technological operation of employing is simple, selected Na
2CO
3～K
2CO
3～SiO
2The agent of two alkalimetal oxide slag can effectively be oxidized to boron oxide to boron and enter slag system, pollutes few.In addition, the method for the auxiliary slagging boron removal of high pressure plasma provided by the invention, the content of boron is lower than 0.3ppmw in the refining low boron polysilicon after obtaining purifying, and except effect of boron is good, is conducive to extensive Industry Promotion.
In the described step (1), adopt intermediate frequency induction heating device with the silico briquette heat fused, the temperature of silicon liquid is 1500～1800 ℃.
In the described step (2), by mass percentage, Na
2CO
3Be 25%～35%, K
2CO
3Be 25%～35%, SiO
2Be 30 ~ 50%.
The present invention adopts the two alkalimetal oxide slag agent of Na2CO3～K2CO3～SiO2 except boron, when Na2CO3 is 25%～35%, K
2CO
3Be 25%～35%, SiO
2When being 30 ~ 70%, the agent of two alkalimetal oxide slag is best with the effect of boron oxidation, can effectively remove the boron in the industrial silicon, and few with respect to other boron removal method pollution, is conducive to extensive Industry Promotion.
Preferably, in the described step (2), by mass percentage, Na
2CO
3Be 30%～35%, K
2CO
3Be 30%～35%, SiO
2Be 30%～40%.
In the described step (2), the mass ratio of described silico briquette and slag former is 1:0.6～1.
Among the present invention, the consumption of slag former is relatively less, has greatly reduced the silicon loss of wrapping up in silicon in the slag and causing, and reduced cost for purification, and the content of boron is very low in the polysilicon after purifying, and refining effect is good.
Preferably, in the described step (2), the mass ratio of described silico briquette and slag former is 1:0.8～1.0.
Among the present invention, the mass ratio of silico briquette and slag former is 1:0.8～1.0 o'clock, can greatly reduce the boron content in the purified silicon, except effect of boron very good.
In the described step (2), keep the silicon liquid temp at 1500～1800 ℃.Under this temperature, the negative oxygen ion that injects from graphite rod and oxygen can be to greatest extent and boron generation oxidizing reaction, except effect of boron best.
In the described step (3), the flow of described oxygen is 5～12L/min, and the ventilatory response time is 25～35min.
In the described step (4), the operating voltage of described high pressure plasma producer is 20～30KV, conduction time 1～3h.
Compared with prior art, beneficial effect of the present invention is:
(1) method of the auxiliary slagging boron removal purifying polycrystalline silicon of high pressure plasma provided by the invention can effectively reduce the quantity of slag, reduces the silicon loss that causes because wrap up in silicon in the slag, reduces the cost of purifying polycrystalline silicon;
(2) selected Na
2CO
3～K
2CO
3～SiO
2The agent of two alkalimetal oxide slag can effectively be oxidized to boron oxide to boron and enter slag system, pollutes few;
(3) content of boron is very low in the refining low boron polysilicon after the purification, and it is good to remove effect of boron;
(4) boron removal method of the present invention is simple, and is easy to operate, and selected high-pressure ion generator apparatus is simple, cost is low, is conducive to extensive Industry Promotion.
Description of drawings
Fig. 1 is the device synoptic diagram of the auxiliary slagging boron removal of high pressure plasma provided by the invention
Wherein: 1～high pressure plasma power supply; 2～oxygen cylinder; 3～high pressure plasma producer; 4～rubber hose; 5～steel pipe; 6～steel bushing; 7～ventilation graphite rod; 8～Medium frequency induction plumbago crucible; 9～coil.
Embodiment
Below in conjunction with embodiment the present invention is described in more detail; but not thereby limiting the invention; under the prerequisite that does not break away from design philosophy of the present invention, the various changes and modifications that those skilled in the art make technical scheme of the present invention all belong to protection scope of the present invention.
Take by weighing primary industry silicon 50kg, silico briquette is packed into heat in the medium-frequency induction furnace plumbago crucible, and be fused into silicon liquid, keeping temperature is 1500 ℃.
Take by weighing composite fluxing medium, composite fluxing medium Na
2CO
3～K
2CO
3～SiO
2Be by weight percentage: Na
2CO
3Be 25%, K
2CO
3Be 25%, SiO
2Be 50%, the mass ratio of composite fluxing medium and industrial silicon is 0.6:1, i.e. 30kg.
In silicon liquid, drop into the powdery composite fluxing medium, continue heating slag former is melted fully, and keep the silicon liquid temp at 1500 ℃.
Will be with the graphite rod preheating of vent channel, after the preheating venting pin is inserted into and begins logical oxygen in the above-mentioned silicon liquid, the gas flow of described oxygen is 5L/min, the ventilatory response time is 30min.
Open the high pressure plasma producer, at room temperature ducted oxygen partial ionization is become oxonium ion and be injected in the silicon liquid, described voltage is 20KV, conduction time 1h;
Silicon liquid obtained above is injected holding furnace solidify, after the silicon ingot cooling, remove silicon ingot surface clinker, the refining low boron polysilicon after obtaining purifying is denoted as A1.
(1) take by weighing primary industry silicon 50kg, silico briquette is packed into heat in the medium-frequency induction furnace plumbago crucible, and be fused into silicon liquid, keeping temperature is 1700 ° of C.
(2) take by weighing the composite slag agent, with composite slag agent Na
2CO
3～K
2CO
3～SiO
2Be by weight percentage: Na
2CO
3Be 30%, K
2CO
3Be that 30%, SiO2 is 40%, the mass ratio 0.8:1 of composite slag agent and industrial silicon, i.e. 40kg.
(3) in silicon liquid, drop into the powdery slag former, continue heating slag former is melted fully, and keep the silicon liquid temp at 1700 ° of C.
(4) will be with the graphite rod preheating of vent channel, after the preheating venting pin is inserted into and begins logical oxygen in the above-mentioned silicon liquid, the gas flow of described oxygen is 10L/min, the ventilatory response time is 25min.
(5) open the high-pressure ion producer, at room temperature ducted oxygen partial ionization is become oxonium ion and be injected in the silicon liquid, described voltage is 25KV, conduction time 2h;
(6) silicon liquid obtained above is injected holding furnace and solidify, after the silicon ingot cooling, remove silicon ingot surface clinker, the refining low boron polysilicon after obtaining purifying is denoted as A2.
(1) take by weighing primary industry silicon 50kg, the silicon material is packed into heat in the medium-frequency induction furnace plumbago crucible, and be fused into silicon liquid, described with the silico briquette heat fused, be to adopt intermediate frequency induction heating device with the silico briquette heat fused, Heating temperature is 1800 ℃.
(2) take by weighing the composite slag agent, with composite slag agent Na
2CO
3～K
2CO
3～SiO
2Be by weight percentage: Na
2CO
3Be 35%, K
2CO
3Be 35%, SiO
2Be 30%, the mass ratio 1:1 of composite slag agent and industrial silicon, i.e. 50kg.
(3) in silicon liquid, drop into the powdery slag former, continue heating slag former is melted fully, and keep the silicon liquid temp at 1800 ℃.
(4) will be with the graphite rod preheating of vent channel, after the preheating venting pin is inserted into and begins logical institute gas in the above-mentioned silicon liquid, the gas flow of described oxygen is 12L/min, the ventilatory response time is 35min.
(5) open the high-pressure ion producer, at room temperature ducted oxygen partial ionization is become oxonium ion and be injected in the silicon liquid, described voltage is 30KV, conduction time 3h;
(6) silicon liquid obtained above is injected holding furnace and solidify, after the silicon ingot cooling, remove silicon ingot surface clinker, the refining low boron polysilicon after obtaining purifying is denoted as A3.
Comparative Examples 1
With embodiment 1 difference be: embodiment 1 ionic medium generator power is closed only pass into oxygen, other parts are with embodiment 1.
Refining low borosilicate after obtaining purifying is denoted as B1.
Comparative Examples 2
With embodiment 2 differences be: embodiment 2 ionic medium generator powers are closed only pass into oxygen, other parts are with embodiment 2.
Refining low borosilicate after obtaining purifying is denoted as B2.
Comparative Examples 3
With embodiment 3 differences be: embodiment 3 ionic medium generator powers are closed only pass into oxygen, other parts are with embodiment 3.
Refining low borosilicate after obtaining purifying is denoted as B3.
Experimental example 1
The boron assay:
With the result of gained in above-described embodiment, get the silicon ingot central part, by the content of B in ICP～MS measurement silicon, measuring result such as table 1.
Table 1
| ? | B／ppmw | Test set |
| Raw material | 2.1 | ICP～ |
| Embodiment A | ||
| 1 | 0.28 | ICP～ |
| Embodiment A | ||
| 2 | 0.26 | ICP～ |
| Embodiment A | ||
| 3 | 0.23 | ICP～MS |
| Comparative Examples B1 | 0.92 | ICP～MS |
| Comparative Examples B2 | 0.76 | ICP～MS |
| Comparative Examples B3 | 0.62 | ICP～MS |
As can be seen from Table 1: embodiment has had significantly reduction with respect to the content of the B of Comparative Examples; Illustrate that method of the present invention can effectively remove boron impurity in the silicon, be fit to industrial scale operation.
Claims (9)
1. the method for the auxiliary slagging boron removal of plasma is characterized in that, may further comprise the steps:
(1) silico briquette is packed into heats in the medium-frequency induction furnace plumbago crucible, and be fused into silicon liquid;
(2) in silicon liquid, drop into slag former, continue heating slag former is melted fully, and keep the silicon liquid temp; Described slag former is by Na
2CO
3, K
2CO
3With SiO
2Form;
(3) will after preheating fully, venting pin be inserted in the silicon liquid with the graphite rod preheating of vent channel, begin logical oxygen;
(4) open simultaneously the high pressure plasma producer, at room temperature the oxygen in the oxygen channel is ionized into oxonium ion also by in the graphite rod Implanted Silicon liquid;
(5) the silicon liquid that obtains in the step (4) is injected holding furnace and solidify, after the silicon ingot cooling, remove silicon ingot surface clinker, the refining low boron polysilicon after obtaining purifying.
2. method according to claim 1 is characterized in that, in the described step (1), adopts intermediate frequency induction heating device with the silico briquette heat fused, and the temperature of silicon liquid is 1500～1800 ℃.
3. method according to claim 1 is characterized in that, in the described step (2), by mass percentage, and in the described slag former, Na
2CO
3Be 25%～35%, K
2CO
3Be 25%～35%, SiO
2Be 30 ~ 50%.
4. method according to claim 3 is characterized in that, in the described step (2), by mass percentage, and in the described slag former, Na
2CO
3Be 30%～35%, K
2CO
3Be 30%～35%, SiO
2Be 30%～40%.
5. method according to claim 1 is characterized in that, in the described step (2), the mass ratio of described silico briquette and slag former is 1:0.6～1.
6. method according to claim 5 is characterized in that, in the described step (2), the mass ratio of described silico briquette and slag former is 1:0.8～1.
7. method according to claim 1 is characterized in that, in the described step (2), keeps the silicon liquid temp at 1500～1800 ℃.
8. method according to claim 1 is characterized in that, in the described step (3), the flow of described oxygen is 5～12L/min, and the ventilatory response time is 25～35min.
9. method according to claim 1 is characterized in that, in the described step (4), the operating voltage of described high pressure plasma producer is 20～30KV, conduction time 1～3h.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103833036A (en) * | 2014-01-08 | 2014-06-04 | 福建兴朝阳硅材料股份有限公司 | Low-cost method for corundum crucible slagging and boron removal |
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| CN103833036A (en) * | 2014-01-08 | 2014-06-04 | 福建兴朝阳硅材料股份有限公司 | Low-cost method for corundum crucible slagging and boron removal |
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Effective date of registration: 20210616 Address after: No.1-2, fukeng huyangtangbei Road, Sheshan village, Nanyang Town, Shanghang County, Longyan City, Fujian Province 364211 Patentee after: Fujian Shanghang Xingheng silicon products Co.,Ltd. Address before: 364211 Nanyang Industrial Zone, Shanghang County, Longyan City, Fujian Province Patentee before: FUJIAN XING THE ZHAOYANG SILICON MATERIALS Co.,Ltd. |