CN102534666B - Electrochemical double refining purification method for high purity silicon and high purity aluminum - Google Patents
Electrochemical double refining purification method for high purity silicon and high purity aluminum Download PDFInfo
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Abstract
The invention belongs to the technical field of purification of silicon and aluminum, particularly relates to an electrochemical double refining purification method for high purity silicon and high purity, which includes the following detailed steps: 1 refining and purifying alloy: mixing raw materials of metal aluminum and metallurgy silicon are smelted by adopting an alloy refining method, impurity boron in metallurgy silicon is removed, and aluminum-silicon alloy is obtained; 2 electrolytic separating: aluminum-silicon alloy serves as an anode, stainless steel serves as a cathode, low temperature fused salt serves as electrolyte, constant current electrolysis is conducted, anode mud gathered in the anode is polycrystalline silicon, and aluminum is gathered in the cathode; and 3 post-processing: the polycrystalline silicon gathered in the anode is smashed, acid pickled to remove impurities, washed by deionized water, filtered and dried to obtain low-boron polycrystalline silicon, the aluminum gathered in the cathode is washed and dried to obtain high purity aluminum. The electrochemical double refining purification method can effectively remove the impurity boron in the metallurgy silicon, is good in purification effect and high in environment-friendly benefit. Recycling rate of the aluminum is above 93%, and purity of the aluminum is above 99.999%.
Description
Technical field
The invention belongs to the technical field that silicon and aluminium are purified, particularly a kind of method of utilizing the two Refining silicon of electrochemical method and aluminium.
Background technology
Solar energy industry obtains various countries' energy strategy attention as a kind of green regenerative energy sources of high-environmental, and especially, after nuclear incident occurs in Japan, solar energy industry heats up again.Meanwhile, industry is also more and more higher for the requirement of solar cell material.At present, most widely used solar cell is silion cell.In order to guarantee its photoelectric transformation efficiency, more than the purity of its important composition silicon materials need to reach 6N.Low-cost solar battery has become one of bottleneck of heliotechnics widespread use with the preparation of polysilicon.
The production method of solar-grade polysilicon, adopts Siemens Method or improved Siemens more, i.e. chemical vapour deposition (CVD) method, and purifying industrial silicon obtains polysilicon.Its cardinal principle is that industrial silicon is processed into trichlorosilane (or silicon tetrachloride) with hydrochloric acid, purify after above-mentioned trichlorosilane (or silicon tetrachloride), then with High Purity Hydrogen reduction vapour deposition, obtain high purity polycrystalline silicon in Siemens reactor (or Bed).These methods are mainly used for producing electronic grade high-purity silicon.For the production of a large amount of solar-grade polysilicons, there is more shortcoming.On the one hand, technical process link is many, the time is long, and intermediate product severe toxicity, explosive, easily leads to Serious Accident, and energy consumption is high, seriously polluted; On the other hand, the attaching problem of core technology and intellecture property has also seriously restricted the popularization of these techniques.
Compare with chemical method, metallurgy method purifying industrial silicon has the advantages such as technical process is relatively simple, energy consumption is low, environmental pollution is little, therefore enjoy people to pay close attention to.Metallurgy method need to realize in conjunction with multiple treatment technology the purification of industrial silicon conventionally, and these technology comprise (the CN 101122047A such as directional freeze, plasma melting, vacuum electron beam melting; CN87104483; CN1890177A; ZL96198989.0; ZL98105942.2; ZL98109239.3 and ZL95197920.5).By directional solidification technique, can realize the removal of most of impurity in industrial silicon, but not obvious to the removal effect of boron impurities and phosphorus; And because the saturated vapor pressure of phosphorus is higher, by vacuum melting, can realize the removal of foreign matter of phosphor.Directional freeze and vacuum melting technology are comparatively ripe purification techniquess, can be applicable to the purification of industrial silicon.Like this, the key that metallurgy method purifying industrial silicon is prepared solar-grade polysilicon is just the removal of boron impurities.The removal of boron impurities mainly adopts slag refining, plasma oxidation refining and alloying fractional condensation etc.Slag refining, part that can be removed boron impurities, is limited to the partition ratio of boron between slag-Jin, be difficult to make the boron impurities content in silicon up to standard, and waste residue amount is large, and environmental problem is outstanding; Plasma oxidation refining, can effectively remove boron impurities, but equipment is complicated, service temperature is high, condition is harsh, is only confined at present bench scale.Alloying fractional condensation method reduces and the obvious rule declining with temperature at the partition ratio of separating out between solid silicon and melt according to boron impurities, adopt suitable metal of alloying element and industrial silicon to carry out melting, after cooling, by steps such as pickling, remove alloy element and impurity, reach the object of purified silicon.
At present, most study, the best alloy system of refining effect are aluminum silicon alloy system.And the shortcoming of the method is that alloy usage quantity is large, reagent consumption is large, and Matter Transfer, energy consumption problem are given prominence to.Especially aluminium is as a kind of important light metal, and it reclaims the cost for purification that price is seriously limiting polysilicon.
Summary of the invention
The object of the invention is to overcome above-mentioned not enough problem, the method of the electrochemical double refining purification of a kind of HIGH-PURITY SILICON and rafifinal is provided, adopt the means of electrochemical double refining, effectively the aluminium in silumin after refining and modifying and silicon are separated, both reclaimed efficiently and obtained rafifinal, also effectively remove the boron impurities in polysilicon, there is higher environmental benefit and economic benefit.
The technical scheme that the present invention adopted is for achieving the above object: the method for the electrochemical double refining purification of a kind of HIGH-PURITY SILICON and rafifinal, concrete steps are as follows: (1) refining and modifying is purified: adopt refining and modifying method to carry out melting to the mixing raw material of metallic aluminium and metalluragical silicon, remove the boron impurities in metalluragical silicon, thereby obtain aluminum silicon alloy; (2) electrolytic separation: aluminum silicon alloy is as anode, and stainless steel is as negative electrode, and low-temperature molten salt, as electrolytic solution, carries out constant-current electrolysis, and the anode sludge of anode enrichment is polysilicon, cathodic enrichment aluminium; (3) aftertreatment: the polysilicon of anode enrichment is carried out to fragmentation, pickling impurity removal, washed with de-ionized water, filtration and dry, obtain the polysilicon of low boron, the aluminium of cathodic enrichment is cleaned, is dried acquisition rafifinal.
In the purification of described (1) refining and modifying, the purity of metallic aluminium is massfraction 90%-99%, and the purity of metalluragical silicon is massfraction 98%-99%.
The concrete technology parameter that described (1) refining and modifying is purified is: smelting temperature is 700-1400 ℃, and soaking time is 0.5-4h, and cooling rate is 0.1-20 ℃/min.
In the purification of described (1) refining and modifying, in aluminum silicon alloy, the massfraction of metallic aluminium is 20%-80%.
Low-temperature molten salt in described (2) electrolytic separation is NaCl-AlCl
3or NaCl-AlCl
3-KCl, wherein AlCl
3molar fraction be 30%-65%.
Described (2) electrolytic separation concrete technology parameter is: current density 10-200 mA/cm
2, electrolysis temperature 60-300 ℃, electrolysis time 0.5-6h.
In described (3) aftertreatment, the sour reagent of pickling impurity removal is one or more in hydrochloric acid, hydrofluoric acid, nitric acid, sulfuric acid and chloroazotic acid, and acid concentration is 1.0 ~ 6.0mol/L.
Unusual effect of the present invention is:
1, using metallic aluminium and metalluragical silicon is raw material, adopts refining and modifying method to purify to metalluragical silicon, can effectively remove the boron impurities in metalluragical silicon, and its refining effect is good, and environmental benefit is high.
2, for the Si-Al alloy after solidifying, adopt electrochemical techniques to realize the output of the separation of aluminium silicon, the recovery of aluminium and rafifinal.The recovery utilization rate of aluminium reaches more than 93%, and purity reaches more than 99.999%.
Accompanying drawing explanation
Accompanying drawing 1 is process flow sheet of the present invention.
Embodiment
Below in conjunction with specific embodiments and the drawings, describe the present invention in detail, but the present invention is not limited to specific embodiment.
Implementation column 1
A method for the electrochemical double refining purification of HIGH-PURITY SILICON and rafifinal, follows these steps to carry out the operations such as silicon, alloy refining, electrolytic separation and processing after correlation:
(1) refining and modifying is purified: the segregation coefficient of impurity reduces along with the reduction of temperature.Adopt refining and modifying method of purification that silicon and aluminium are configured to alloy and can effectively reduce the liquidus temperature of alloy melt, thereby the impurity such as boron are suppressed in melt, and silicon is improved as its purity of primary phase.Adopting refining and modifying method is that the metallic aluminium of massfraction 90.0% and purity are that the mixing raw material of massfraction 98.0%, the boron content metalluragical silicon that is 14ppmw carries out melting and removes the boron impurities in metalluragical silicon to purity, thereby obtains aluminum silicon alloy.The concrete technology parameter that refining and modifying is purified is: smelting temperature is 700 ℃, and soaking time is 0.5h, and cooling rate is 0.1 ℃/min, and in aluminum silicon alloy, the massfraction of metallic aluminium is 80%.
(2) electrolytic separation: in the various metallic elements of anode aluminum silicon alloy, only have aluminium to dissolve on anode, and silicon, the inactive metallic element of copper geometric ratio aluminium do not dissolve, and still stay in alloy, therefore, be dissolved in electrolytic solution to obtain Al
3+preferentially on negative electrode, deposit, and silicon precipitates as the anode sludge.Adopt aluminum silicon alloy as anode, stainless steel is as negative electrode, and low-temperature molten salt, as electrolytic solution, carries out constant-current electrolysis, and the anode sludge of anode enrichment is polysilicon, cathodic enrichment aluminium.Low-temperature molten salt in electrolytic separation is NaCl-AlCl
3, AlCl wherein
3molar fraction be 30%, electrolytic separation concrete technology parameter is: current density 200 mA/cm
2, 300 ℃ of electrolysis temperatures, electrolysis time 6h.
(3) aftertreatment: the polysilicon of anode enrichment is carried out to fragmentation, pickling impurity removal, washed with de-ionized water, filtration and dry, obtain the polysilicon of low boron, the aluminium of cathodic enrichment is cleaned, is dried acquisition rafifinal, the sour reagent that the polysilicon of anode enrichment is carried out to pickling impurity removal is hydrochloric acid, and acid concentration is 6.0mol/L.
The purity check detected result of the polysilicon of the low boron of gained and rafifinal is: the purity of the polysilicon of low boron is massfraction 99.95%, and boron impurities content is 0.56 ppmw, and the purity of rafifinal is massfraction 99.9993%, and the rate of recovery is 93.6%.
Implementation column 2
A method for the electrochemical double refining purification of HIGH-PURITY SILICON and rafifinal, follows these steps to carry out the operations such as silicon, alloy refining, electrolytic separation and processing after correlation:
(1) refining and modifying is purified: adopting refining and modifying method is that the metallic aluminium of massfraction 99.0% and purity are that the mixing raw material of massfraction 99.0%, the boron content metalluragical silicon that is 11ppmw carries out melting and removes the boron impurities in metalluragical silicon to purity, thereby obtain aluminum silicon alloy, the concrete technology parameter that refining and modifying is purified is: smelting temperature is 1400 ℃, soaking time is 4h, cooling rate is 20 ℃/min, and in aluminum silicon alloy, the massfraction of metallic aluminium is 20%.
(2) electrolytic separation: adopt aluminum silicon alloy as anode, stainless steel is as negative electrode, and low-temperature molten salt, as electrolytic solution, carries out constant-current electrolysis, and the anode sludge of anode enrichment is polysilicon, cathodic enrichment aluminium, the low-temperature molten salt in electrolytic separation is NaCl-AlCl
3-KCl, wherein AlCl
3molar fraction be 65%, electrolytic separation concrete technology parameter is: current density 10mA/cm
2, 60 ℃ of electrolysis temperatures, electrolysis time 0.5h.
(3) aftertreatment: the polysilicon of anode enrichment is carried out to fragmentation, pickling impurity removal, washed with de-ionized water, filtration and dry, obtain the polysilicon of low boron, the aluminium of cathodic enrichment is cleaned, is dried acquisition rafifinal, the sour reagent that the polysilicon of anode enrichment is carried out to pickling impurity removal is hydrochloric acid, and acid concentration is 1.0mol/L.
The purity check detected result of the polysilicon of the low boron of gained and rafifinal is: the purity of the polysilicon of low boron is massfraction 99.91%, and boron impurities content is 0.67 ppmw, and the purity of rafifinal is massfraction 99.9992%, and the rate of recovery is 95.4%.
Implementation column 3
A method for the electrochemical double refining purification of HIGH-PURITY SILICON and rafifinal, follows these steps to carry out the operations such as silicon, alloy refining, electrolytic separation and processing after correlation:
(1) refining and modifying is purified: adopting refining and modifying method is that the metallic aluminium of massfraction 95.5% and purity are that the mixing raw material of massfraction 98.2%, the boron content metalluragical silicon that is 15ppmw carries out melting and removes the boron impurities in metalluragical silicon to purity, thereby obtain aluminum silicon alloy, the concrete technology parameter that refining and modifying is purified is: smelting temperature is 1200 ℃, soaking time is 1h, cooling rate is 1.5 ℃/min, and in aluminum silicon alloy, the massfraction of metallic aluminium is 40%.
(2) electrolytic separation: adopt aluminum silicon alloy as anode, stainless steel is as negative electrode, and low-temperature molten salt, as electrolytic solution, carries out constant-current electrolysis, and the anode sludge of anode enrichment is polysilicon, cathodic enrichment aluminium, the low-temperature molten salt in electrolytic separation is NaCl-AlCl
3-KCl, wherein AlCl
3molar fraction be 50%, electrolytic separation concrete technology parameter is: current density 50mA/cm
2, 100 ℃ of electrolysis temperatures, electrolysis time 3h.
(3) aftertreatment: the polysilicon of anode enrichment is carried out to fragmentation, pickling impurity removal, washed with de-ionized water, filtration and dry, obtain the polysilicon of low boron, the aluminium of cathodic enrichment is cleaned, is dried acquisition rafifinal, the sour reagent that the polysilicon of anode enrichment is carried out to pickling impurity removal is nitric acid, and acid concentration is 2.0mol/L.
The purity check detected result of the polysilicon of the low boron of gained and rafifinal is: the purity of the polysilicon of low boron is massfraction 99.94%, and boron impurities content is 0.45 ppmw, and the purity of rafifinal is massfraction 99.9996%, and the rate of recovery is 98.8%.
Implementation column 4
Follow these steps to carry out the operations such as silicon, alloy refining, electrolytic separation and processing after correlation:
(1) refining and modifying is purified: adopting refining and modifying method is that the metallic aluminium of massfraction 96.8% and purity are that the mixing raw material of massfraction 98.8%, the boron content metalluragical silicon that is 12ppmw carries out melting and removes the boron impurities in metalluragical silicon to purity, thereby obtain aluminum silicon alloy, the concrete technology parameter that refining and modifying is purified is: smelting temperature is 1000 ℃, soaking time is 3h, cooling rate is 10 ℃/min, and in aluminum silicon alloy, the massfraction of metallic aluminium is 60%.
(2) electrolytic separation: adopt aluminum silicon alloy as anode, stainless steel is as negative electrode, and low-temperature molten salt, as electrolytic solution, carries out constant-current electrolysis, and the anode sludge of anode enrichment is polysilicon, cathodic enrichment aluminium, the low-temperature molten salt in electrolytic separation is NaCl-AlCl
3, AlCl wherein
3molar fraction be 40%, electrolytic separation concrete technology parameter is: current density 100mA/cm
2, 200 ℃ of electrolysis temperatures, electrolysis time 4h.
(3) aftertreatment: the polysilicon of anode enrichment is carried out to fragmentation, pickling impurity removal, washed with de-ionized water, filtration and dry, obtain the polysilicon of low boron, the aluminium of cathodic enrichment is cleaned, is dried acquisition rafifinal, the sour reagent that the polysilicon of anode enrichment is carried out to pickling impurity removal is sulfuric acid, and acid concentration is 3.0mol/L.
The purity check detected result of the polysilicon of the low boron of gained and rafifinal is: the purity of the polysilicon of low boron is massfraction 99.96%, and boron impurities content is 0.42 ppmw, and the purity of rafifinal is massfraction 99.9998%, and the rate of recovery is 94.9%.
Claims (5)
1. the method for the electrochemical double refining purification of a HIGH-PURITY SILICON and rafifinal, it is characterized in that, concrete steps are as follows: (1) refining and modifying is purified: adopt refining and modifying method to carry out melting to the mixing raw material of metallic aluminium and metalluragical silicon, smelting temperature is 700-1400 ℃, soaking time is 0.5-4h, cooling rate is 0.1-20 ℃/min, removes the boron impurities in metalluragical silicon, thereby obtains aluminum silicon alloy; (2) electrolytic separation: aluminum silicon alloy is as anode, and stainless steel is as negative electrode, and low-temperature molten salt, as electrolytic solution, carries out constant-current electrolysis, current density 10-200 mA/cm
2, electrolysis temperature 60-300 ℃, electrolysis time 0.5-6h, the anode sludge of anode enrichment is polysilicon, cathodic enrichment aluminium; (3) aftertreatment: the polysilicon of anode enrichment is carried out to fragmentation, pickling impurity removal, washed with de-ionized water, filtration and dry, obtain the polysilicon of low boron, the aluminium of cathodic enrichment is cleaned, is dried acquisition rafifinal.
2. the method for the electrochemical double refining purification of a kind of HIGH-PURITY SILICON according to claim 1 and rafifinal, it is characterized in that: in the purification of described (1) refining and modifying, the purity of metallic aluminium is massfraction 90%-99%, and the purity of metalluragical silicon is massfraction 98%-99%.
3. the method for the electrochemical double refining purification of a kind of HIGH-PURITY SILICON according to claim 1 and rafifinal, is characterized in that: in the purification of described (1) refining and modifying, in aluminum silicon alloy, the massfraction of metallic aluminium is 20%-80%.
4. the method for the electrochemical double refining purification of a kind of HIGH-PURITY SILICON according to claim 1 and rafifinal, is characterized in that: the low-temperature molten salt in described (2) electrolytic separation is NaCl-AlCl
3or NaCl-AlCl
3-KCl, wherein AlCl
3molar fraction be 30%-65%.
5. the method for the electrochemical double refining purification of a kind of HIGH-PURITY SILICON according to claim 1 and rafifinal, it is characterized in that: in described (3) aftertreatment, the sour reagent of pickling impurity removal is one or more in hydrochloric acid, hydrofluoric acid, nitric acid, sulfuric acid and chloroazotic acid, and acid concentration is 1.0 ~ 6.0mol/L.
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| CN103173780B (en) * | 2013-03-01 | 2015-06-03 | 中南大学 | Method and device for preparing solar polycrystalline silicon material by semi-continuous molten salt electrolysis |
| CN104372380B (en) * | 2014-11-18 | 2016-08-24 | 辽宁石化职业技术学院 | A kind of low-temperature molten salt method prepares High Pure Chromium |
| CN104846402A (en) * | 2015-04-17 | 2015-08-19 | 内蒙古机电职业技术学院 | Apparatus and method for low temperature electrolysis separation of silicon-aluminum alloy |
| CN105063660B (en) * | 2015-08-03 | 2017-07-04 | 中南大学 | A kind of method that nano-silicon powder is directly prepared in electrorefining processes |
| CN109252045B (en) * | 2018-10-31 | 2020-04-07 | 东北大学 | Method for extracting metal aluminum and ferrosilicon alloy from aluminum-containing mineral |
| CN111748828B (en) * | 2020-06-05 | 2022-05-06 | 北京科技大学 | Method for recycling copper, silver, selenium and tellurium through molten salt electrolysis of copper anode slime |
| CN115305508A (en) * | 2021-05-08 | 2022-11-08 | 郑州大学 | Method for producing metal aluminum and polysilicon by using high-silicon aluminum-containing resource |
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