CN105084367A - Method for removing polysilicon wire cutting waste impurities by potential dispersion-microwave pickling process - Google Patents
Method for removing polysilicon wire cutting waste impurities by potential dispersion-microwave pickling process Download PDFInfo
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Abstract
The invention relates to a method for removing polysilicon wire cutting waste impurities by a potential dispersion-microwave pickling process. According to the method, after silicon and silicon carbide particles in the polysilicon wire cutting waste are dispersed under alkaline conditions, a microwave reinforced pickling process is utilized to remove the impurities boron, phosphorus and iron. The method comprises the following steps: pretreating the cutting waste, removing the polyethylene glycol solution, and drying to obtain silicon-silicon carbide mixed powder; and adding a weakly-alkaline solution with a certain concentration to regulate the pH value to 12-14, stirring uniformly, putting into ultrasonic waves to sufficiently disperse the particles, neutralizing the solution, and carrying out the microwave reinforced pickling process. The method has the advantages of simple technical process and stable technical parameters; and the weakly-alkaline solution is utilized to regulate the pH value so as to change the surface potential of the particles, and thus, the particles can be sufficiently dispersed. The weakly-alkaline solution can be recycled, thereby effectively reducing the discharge. The microwave field can be utilized to obviously reinforce the pickling reaction, thereby obviously shortening the pickling reaction time and obviously enhancing the impurity removal efficiency.
Description
Technical field
The present invention relates to purifying polycrystalline silicon Linear cut waste recovery technology, especially adopt the pickling of weak base reagent current potential dispersion-microwave to remove the method for the impurity such as boron, phosphorus in this waste material.
Background technology
At present, silicon single crystal and the polysilicon chip of producing solar cell mainly adopt multi-wire saw to process, and in the course of processing, can produce a large amount of cutting slugs, except the polyoxyethylene glycol as abrasive suspension agent, solid break flour is the impurity such as silicon carbide (70%), silicon (25%) and Fe mainly.According to existing research work, polyoxyethylene glycol can be used as suspension agent by the method Recovery and recycle such as centrifugal, and remaining pressed powder waste material, then great majority are for extracting silicon carbide wherein.And for silica flour material wherein, then well do not apply outlet.Consider the high purity source formation of itself, and quite most of (at least 30%) is cut into break flour shape by mill in cutting process, if the further enrichment of the technology of comparatively economical and efficient can be adopted, be separated, be purified to the purity of solar-grade polysilicon, thus recycling can make solar energy polycrystalline silicon battery material, then not only resource utilization recovery is achieved for the polycrystalline silicon raw material cutting waste material of costliness, and for the reduction of current solar energy polycrystal silion cell cost, also there is very important realistic meaning.The silicon of these chip waste materials, the purity of itself has reached more than the 5N required by solar cell, other impurity are as silicon carbide, scrap metal etc., it should be all with it the mode of physical mixed, therefore be should be able to by the enforcement of simple, cheap multiple technologies means theoretically, make it to realize enrichment, purification, reach the purity of solar energy level silicon.
From polycrystalline silicon cut waste, be purified to the purity grade of solar energy level silicon, two most important difficult problems or challenge will be faced.One is the efficient removal of fine SiC powder in cutting wasted powder, and especially the removing of most sic powder thought by granularity and silica flour.Otherwise silicon-carbide particle may be difficult to cost-effective removing in the follow-up high temperature purification stage, thus significantly impact the photoelectric conversion usefulness of polysilicon.Another difficult problem is then the deep removal problem of the boron cut in waste material, phosphorus impurities.Consider pyrometallurgical method remove in silicon boron, phosphorus to degree up to standard technically almost cannot, therefore we must will be removed to Passing Criteria the boron in cutting wasted powder, phosphorus in the incident stage.Otherwise full technical process all will be had no chance can the high-purity solar energy polycrystalline silicon of economical and efficient ground production department.Around these two crucial problem, we have carried out distinctive research and development.Inside us disclosed patent (201210162413.0), propose the effective ways adopting wet separation ultrafine SiC powders wherein, for the Silicon-rich powder of preliminary concentration sample being realized chip powder by simple wet process, also need impurity wherein as iron, copper, boron, phosphorus etc. remove process, pickling is conventional method, but it seems from the result of current open report, ubiquity pickling efficiency is low, degree of depth pickling is removed and is difficult to the difficult problem reaching polysilicon requirement.Around the solution of this problem, in this patent the wet process acid generally adopted at present is dissolved to a kind of more fruitful pickling impurity-removing method of the open process removing soluble impurity.
There are some technology to be used for removing the method for various metallic impurity in chip powder at present, had the method for conventional pickling, as disclosed in article (Tzu-HsuanTsai), at normal temperatures and pressures, the HNO of waste material and 1M concentration
3stirring reaction 40 minutes, the content of Fe can drop to 0.57%.Use above impurity-removing method, removal effect is remarkable, but along with the prolongation in reaction times, removal efficiency declines, and final removal degree is still difficult to the restriction requirement meeting foreign matter content.
Summary of the invention
In order to solve the problem, the object of this invention is to provide a kind of technical process simple, processing parameter is stablized, and dust removal rate significantly improves, effective emissions reduction, the current potential dispersion-microwave acid wash that can reduce costs again removes the method for polysilicon lines cutting waste material impurity.
Technical scheme of the present invention is: current potential dispersion-microwave acid wash removes the method for polysilicon lines cutting waste material impurity, in the method, first Linear cut waste material uses the process of surface potential regulation and control-centrifuging, obtain the silica flour of Si content more than more than 80%, wherein the content of Fe is the content of 5.56%, Cu is 0.31%.Fig. 1 is the electromicroscopic photograph of this silica flour.The particle diameter of silica flour is approximately 0.8 μm, and has agglomeration, and metallic impurity should be attached on Si particle or be mixed among reunion.According to solid-liquid phase reaction principle of dynamics, acid solution only has when fully contacting with metallic impurity, and it is more thorough that reaction just can be carried out.So, first regulate more than pH to 12 with the ammonia soln containing organic acid ammonium salt in the present invention, then use ultrasonication silica flour, fully can disperse, allow metallic impurity fully come out.Because microwave has the feature of the micro stirring divergent function on the fast and powerful molecular scale of body heat temperature raising, effectively can promote contacting and reaction of metallic impurity and acid solution, so carry out pickling impurity removal in microwave field, not only can Reaction time shorten, impurity-eliminating effect also can be fairly obvious.
Specifically comprise the following steps:
Step 1. is divided in advance:
Get a certain amount of organic polysilicon lines such as polyoxyethylene glycol of having removed and cut wasted powder, after adding deionized water according to liquid-solid ratio 3 ~ 6:1wt, stir 30 ~ 60 minutes, be that the pH value of the ammonia soln adjustment silica flour solution of the organic acid ammonium salt of 8-15% is to 12-14 by concentration, after stirring, put into ultrasonic wave and disperse, after 30 ~ 60 minutes, obtain silica flour solution, for subsequent use;
Step 2. neutralizes:
Be 3000-5000 rev/min by the mixing solutions after step 1 processes at centrifugal rotational speed, centrifugation time is 15 ~ 25 minutes, after centrifugation, supernatant liquor can recycle, after the silica flour taking-up of lower floor, add a small amount of deionized water and stirring evenly, and be that the salt acid for adjusting pH of 3mol/l is to neutral by concentration, obtain suspension, for subsequent use;
The pickling of step 3. microwave:
Adding the inorganic acid solution that a certain amount of concentration is 2mol/l-5mol/l in suspension step 2 obtained, put into microwave chemical reactor, is 500-1000w at microwave power, reacts after 5 ~ 20 minutes and takes out, for subsequent use;
Step 4. filtering drying:
By the suspension after step 3 processes, filter, use deionized water wash 3 ~ 5 post-dryings, the high-purity silicon powder obtained, the boron in described high-purity silicon powder and the content of phosphorus all can reach the requirement of the two foreign matter content in solar-grade polysilicon.
Further, described organic acid ammonium salt salts solution is ammonium citrate, ammonium oxalate, ammonium tartrate or oxysuccinic acid ammonium.
Further, described inorganic acid solution is hydrochloric acid, nitric acid, sulfuric acid or citric acid.
Further, in described silica flour, the clearance of iron can reach more than 90%, and the content of boron and phosphorus is all less than 0.1ppm.
Principle of the present invention is: the method passes through acid cleaning process, at pretreatment stage, more than ammoniacal liquor adjust ph to 12, now particle electrostatic repulsion is each other larger, effectively can resist the reunion of particle, and assistant with ultrasonication, make particle can after disperse more fully, with make by sweep along silica flour particulate group in the impurity such as boron, phosphorus come out.In addition, microwave is used fully to strengthen pickling reaction process, make by the effect of reunion powder body due to microwave, under the auxiliary stirring of polar molecule strenuous exercise, wrapped impurity can be released fully, acid molecule is spread fully, penetrate in powder agglomerates, realize with between acid molecule with nonmetal chip microparticle contacting and reacting fully, thus by abundant for nonmetal chip particles, fully be converted into the nonmetallic ion form be dissolved in the aqueous solution, thus by simple filter, pickling, washing, just can be quick, efficiently by nonmetallic impurity washing removing.
The present invention is compared with existing report or disclosed technology, and the beneficial effect had is:
(1) technical process of the present invention is simple, and processing parameter is stablized, and can fully disperse, than the good impurity removing effect of direct pickling with the surface potential that weak caustic solution regulates pH to change particle.
(2) weak caustic solution can Reusability, both can effective emissions reduction, can reduce costs again.
(3) carry out significantly strengthening pickling reaction with microwave field, the pickling reaction response time obviously shortens than traditional stirring and pickling, and dust removal rate significantly improves.
Accompanying drawing explanation
Fig. 1 is the electromicroscopic photograph of the present invention's silica flour used.
Fig. 2 is the impurity basic flowsheet of coal preparation that current potential dispersion-microwave acid wash removes in silicon single crystal and polysilicon lines cutting waste material.
Embodiment
Following examples just in order to set forth and illustrate the technical scheme that above summary of the invention is contained better, within being not limited only to actual conditions cited by embodiment and process parameters range.
Embodiment 1:
After the mixed powder of silicon and silicon carbide is added deionized water according to liquid-solid ratio 4:1, stir 40 minutes.Be the pH value to 12 that the ammoniacal liquor of the ammonium citrate of 8% regulates this silica flour solution by concentration, after stirring, put into ultrasonic wave and disperse, put into centrifuge tube after within 30 minutes, taking out and carry out centrifugation, centrifuge speed is 4500 revs/min, and centrifugation time is 15 minutes.After centrifugation, supernatant liquor can recycle, and after the silica flour taking-up of lower floor, adds a small amount of deionized water and stirring, and extremely neutral with the salt acid for adjusting pH of 3mol/l.
Add the hydrochloric acid soln of 3mol/l in this silica flour suspension, put into microwave chemical reactor, microwave power is 500W, reacts after 10 minutes and takes out.Solution after overpickling, filter, use deionized water wash 5 post-dryings, obtain the silica flour after removal of impurities, the clearance of its iron can reach 95%, and the content of boron and phosphorus is all less than 0.1ppm.
Embodiment 2:
After the mixed powder of silicon and silicon carbide is added deionized water according to liquid-solid ratio 5:1, stir 40 minutes.It is the pH value to 12.5 that the ammonia soln of the ammonium tartrate of 15% regulates this silica flour solution by concentration, after stirring, put into ultrasonic wave and disperse, put into centrifuge tube after within 40 minutes, taking out and carry out centrifugation, centrifuge speed is 4000 revs/min, and centrifugation time is 18 minutes.After centrifugation, supernatant liquor can recycle, and after the silica flour taking-up of lower floor, adds a small amount of deionized water and stirring, and extremely neutral with the salt acid for adjusting pH of 3mol/l.
Add the sulphuric acid soln of 3mol/l in this silica flour suspension, put into microwave chemical reactor, microwave power is 1000W, reacts after 8 minutes and takes out.Solution after overpickling, filter, use deionized water wash 5 post-dryings, obtain the silica flour after removal of impurities, the clearance of its iron can reach 93%, and the content of boron and phosphorus is all less than 0.1ppm.
Embodiment 3:
After the mixed powder of silicon and silicon carbide is added deionized water according to liquid-solid ratio 6:1, stir 50 minutes.It is the pH value to 13 that the ammonia soln of the oxysuccinic acid ammonium of 15% regulates this silica flour solution by concentration, after stirring, put into ultrasonic wave and disperse, put into centrifuge tube after within 45 minutes, taking out and carry out centrifugation, centrifuge speed is 3500 revs/min, and centrifugation time is 20 minutes.After centrifugation, supernatant liquor can recycle, and after the silica flour taking-up of lower floor, adds a small amount of deionized water and stirring, and extremely neutral with the salt acid for adjusting pH of 3mol/l.
Add the sulphuric acid soln of 3mol/l in this silica flour suspension, put into microwave chemical reactor, microwave power is 800W, reacts after 12 minutes and takes out.Solution after overpickling, filter, use deionized water wash 5 post-dryings, obtain the silica flour after removal of impurities, the clearance of its iron can reach 92%, and the content of boron and phosphorus is all less than 0.1ppm.
Embodiment 4:
After the mixed powder of silicon and silicon carbide is added deionized water according to liquid-solid ratio 3:1, stir 60 minutes.It is the pH value to 13.5 that the ammonia soln of the ammonium oxalate of 10% regulates this silica flour solution by concentration, after stirring, put into ultrasonic wave and disperse, put into centrifuge tube after within 50 minutes, taking out and carry out centrifugation, centrifuge speed is 4000 revs/min, and centrifugation time is 20 minutes.After centrifugation, supernatant liquor can recycle, and after the silica flour taking-up of lower floor, adds a small amount of deionized water and stirring, and extremely neutral with the salt acid for adjusting pH of 3mol/l.
Add the salpeter solution of 3mol/l in this silica flour suspension, put into microwave chemical reactor, microwave power is 900W, reacts after 10 minutes and takes out.Solution after overpickling, filter, use deionized water wash 5 post-dryings, obtain the silica flour after removal of impurities, the clearance of its iron can reach 92%, and the content of boron and phosphorus is all less than 0.1ppm.
Embodiment 5:
After the mixed powder of silicon and silicon carbide is added deionized water according to liquid-solid ratio 5:1, stir 30 minutes.It is the pH value to 14 that the ammonia soln of the ammonium citrate of 10% regulates this silica flour solution by concentration, after stirring, put into ultrasonic wave and disperse, put into centrifuge tube after within 60 minutes, taking out and carry out centrifugation, centrifuge speed is 4000 revs/min, and centrifugation time is 20 minutes.After centrifugation, supernatant liquor can recycle, and after the silica flour taking-up of lower floor, adds a small amount of deionized water and stirring, and extremely neutral with the salt acid for adjusting pH of 3mol/l.
Add the hydrochloric acid soln of 3mol/l in this silica flour suspension, put into microwave chemical reactor, microwave power is, 700W, reacts after 18 minutes and takes out.Solution after overpickling, filter, use deionized water wash 5 post-dryings, obtain the silica flour after removal of impurities, the clearance of its iron can reach 93%, and the content of boron and phosphorus is all less than 0.1ppm.
Claims (3)
1. current potential dispersion-microwave acid wash removes the method for polysilicon lines cutting waste material impurity, and it is characterized in that, the method specifically comprises the following steps:
Step 1. is divided in advance:
Get a certain amount of organic polysilicon lines such as polyoxyethylene glycol of having removed and cut wasted powder, after adding deionized water according to liquid-solid ratio 3 ~ 6:1wt, stir 30 ~ 60 minutes, be that the pH value of the ammonia soln adjustment silica flour solution of the organic acid ammonium salt of 8-15% is to 12-14 by concentration, after stirring, put into ultrasonic wave and disperse, after 30 ~ 60 minutes, obtain silica flour solution, for subsequent use;
Step 2. neutralizes:
Be 4000-6000 rev/min by the silica flour solution after step 1 processes at centrifugal rotational speed, centrifugation time is 15 ~ 25 minutes, after centrifugation, supernatant liquor can recycle, after the silica flour taking-up of lower floor, add a small amount of deionized water and stirring evenly, and be that the salt acid for adjusting pH of 3mol/l is to neutral by concentration, obtain silica flour suspension, for subsequent use;
The pickling of step 3. microwave:
Add the inorganic acid solution that a certain amount of concentration is 2mol/l-5mol/l in silica flour suspension step 2 obtained, put into microwave chemical reactor, react under microwave power is 500-1000w after 5 ~ 20 minutes and take out, for subsequent use;
Step 4. filtering drying:
By the solution after step 3 processes, filter, by deionized water wash 3 ~ 5 post-dryings, must reach the silica flour of 4-6N, the boron in silica flour and the content of phosphorus all can reach the content requirement of the two impurity in solar-grade polysilicon.
2. method according to claim 1, is characterized in that, described organic acid ammonium salt is ammonium citrate, ammonium oxalate, ammonium tartrate or oxysuccinic acid ammonium.
3. method according to claim 1, is characterized in that, described inorganic acid solution is hydrochloric acid, nitric acid, sulfuric acid or citric acid.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113582185A (en) * | 2021-08-09 | 2021-11-02 | 长沙新立硅材料科技有限公司 | Method for preparing solar-grade silicon raw material by using silicon mud waste |
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| US20100215561A1 (en) * | 2006-12-29 | 2010-08-26 | Lan C W | Recovery method of silicon slurry |
| CN102351184A (en) * | 2011-07-18 | 2012-02-15 | 矽明科技股份有限公司 | Method for recovering silicon carbide, high-purity silicon and dispersion liquid from silicon material linear cutting waste mortar |
| CN102659111A (en) * | 2012-04-28 | 2012-09-12 | 南京远齐环保科技有限公司 | Method for recovering silicon and silicon carbide from silicon wafer cutting waste mortar |
| CN102659112A (en) * | 2012-05-23 | 2012-09-12 | 北京科技大学 | Method for recovering silicon powder from monocrystalline and polycrystalline silicon cutting wastes by utilizing potential adjustment centrifugal process |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20100215561A1 (en) * | 2006-12-29 | 2010-08-26 | Lan C W | Recovery method of silicon slurry |
| CN102351184A (en) * | 2011-07-18 | 2012-02-15 | 矽明科技股份有限公司 | Method for recovering silicon carbide, high-purity silicon and dispersion liquid from silicon material linear cutting waste mortar |
| CN102659111A (en) * | 2012-04-28 | 2012-09-12 | 南京远齐环保科技有限公司 | Method for recovering silicon and silicon carbide from silicon wafer cutting waste mortar |
| CN102659112A (en) * | 2012-05-23 | 2012-09-12 | 北京科技大学 | Method for recovering silicon powder from monocrystalline and polycrystalline silicon cutting wastes by utilizing potential adjustment centrifugal process |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113582185A (en) * | 2021-08-09 | 2021-11-02 | 长沙新立硅材料科技有限公司 | Method for preparing solar-grade silicon raw material by using silicon mud waste |
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