CN102602934B

CN102602934B - Production method for removing slag agent of boron impurity in slagging method

Info

Publication number: CN102602934B
Application number: CN 201110025326
Authority: CN
Inventors: 陈应天
Original assignee: BEIJING YINGTIAN YANGGUANG SOLAR ENERGY TECHNOLOGY Co Ltd
Current assignee: BEIJING YINGTIAN YANGGUANG SOLAR ENERGY TECHNOLOGY Co Ltd
Priority date: 2011-01-21
Filing date: 2011-01-21
Publication date: 2013-09-18
Anticipated expiration: 2031-01-21
Also published as: CN102602934A

Abstract

The invention relates to a production method for removing a slag agent with a boron impurity precast bar in a slagging method, as a condition of being different from the production method of the conventional slagging method, a calcium oxide-sodium oxide type production method is utilized, rather than a calcium oxide-sodium dioxide type production method in the prior art. The new production method can purify raw materials with low cost, can generate a uniform effect in a mixing process due to an expanding process, and can conveniently separate a silicon material and residues by using a water quenching method after melting.

Description

A kind of production method of in slag practice, removing the slag agent of boron impurity

Technical field

A kind of method that relates to purifying silicon materials particularly uses slagging process effectively to remove the new prescription of the slag agent of boron impurity in metallurgical Physical or severe radiation catalysis method from industrial silicon.

Background technology

The method of present chemical method purifying silicon materials, Siemens Method particularly, improved Siemens and silane thermal decomposition process, although can reach the purity that the electronic-grade silicon material comprises the solar level silicon materials, current consumption is very big, the exhaust emissions of four silicon oxide can cause suitable pollution to environment, has to make the method for people's other more cheap more easily purified silicons of seeking me.

Refine in the method for silicon in many siemenss that are different from, metallurgical Physical is owing to can directly refine HIGH-PURITY SILICON from industrial silicon, and power consumption is less, and is pollution-free, is subject to people's very big attention always.The characteristics of metallurgical Physical are with the various impurity in the industrial silicon, comprise boron, phosphorus and metal, adopt diverse ways to remove.Yet because " diagonal lines " principle in the periodic table of chemical element, boron is very identical with many physics, the chemical property of silicon, even the character of their various compounds is also close.This has just caused the great difficulty that uses metallurgical Physical separating boron from silicon.In order to overcome this difficulty, people have tested many methods, comprise air blast, wet method plasma flame method and slag practice etc.Estimate with regard to economy and practicality, the possibility of slag practice success is the highest.

Slag practice uses boron different solubleness in slag and molten silicon, and boron is extracted from industrial silicon.In this patent, we are called the purification factor, as the sign of purification efficiency with the ratio of the boron content in the silicon before purifying and the boron content after the purification.People mainly carry out effort from two aspects in order to pursue the higher purification factor: the firstth, manage to improve the contact area of silica flour and slag agent, and the secondth, seek the prescription of better slag agent.Up to now, except present inventor's work, the obtained best purification factor of slag practice is 5.5.And the present inventor is in grinding of severe radiation catalysis method is real, from improving white residue contact surface (document 2: Chen Yingtian, " a kind of blending means of the process Raw at purification process of high-purity silicon ", number of patent application: 201110000236.1) and two aspects of seeking newly to fill a prescription made significant improvement, the purification factor has reached more than 10.

Slag former in traditional slag practice of prior art comprises SiO ₂And alkaline metal oxide.This basic oxide comprise and are used alone or as a mixture CaO, MgO, Na ₂O, K ₂O, BaO etc. and Co, Mg, Na, K, the carbonate of Ba etc.People use these with SiO ²Be that main material has been made prescription miscellaneous, however after all these, its primary structure is SiO ₂And CaO, in such prescription, SiO ₂Be to use as oxygenant, the Main Function of CaO is the eutectic point that reduces the slag agent.We are referred to as SiO ₂-CaO type prescription.

The prescription of tradition slag practice is with SiO ₂-CaO is main, and except strengthening its oxygenizement, studying carefully its major cause is because the eutectic temperature of slag agent need to be down near the fusing point of silicon.At SiO ₂In the phasor of CaO mixture, the ratio of these two kinds of compositions generally is to be in SiO ₂In CaO equivalent or the prescription situation near equivalent, in this situation, eutectic point is about 1500 ° of C.

This traditional SiO ₂There is following shortcoming: 1.SiO in-CaO prescription ₂Boron content in the raw material is difficult for removing.In fact, the boron impurity in the industrial silicon is originally to derive from carbon reduction reaction and generates in the process of silicon, be left behind by the boron impurity that originally contained in the silicon dioxide mine, yet in self-heating circle, boron-containing impurities or few boracic do not contain the SiO of matter ₂Be relatively more rare, and contain the SiO of boron ₂Not easy-to-use simple method is removed.Therefore, the boron impurity content in the slag agent is the major obstacles that improves the purification factor.2. conventional formulation is a kind of mixing of simple material, and the mixing of such material no matter how abundant stirring is, all can not be seen the microcosmic homogenizing in fact.This also is the reason that the purification factor can not improve greatly.

In sum, the present invention has disclosed a kind of traditional SiO that is different from ₂The prescription of-CaO type, new prescription can overcome two large shortcomings of conventional formulation, the puffing process that its mixing is accompanied by can improve silica flour greatly with the mixing uniformity of slag agent, its raw material can purifying be the atomic little raw material of boron-containing impurities, and can use easily later on the method for the shrend that document 3 invents that the silicon material is separated in residue in melting, (document 3: Chen Yingtian, the method of＜＜a kind of divided silicon and surplus slag〉〉 number of patent application 201010282839.0) reached at present the purification factor greater than 10 state of the art, and the scope of the 20-30 that is not difficult more to bring up to.

Summary of the invention

A kind of prescription of removing efficiently the slag agent of boron impurity in slag practice is characterized by in this prescription, and the main component of slag agent is accompanied by puffing process for its mixing, and boron impurity content is the CaO-Na of trace extremely ₂The O system.Realize that this prescription may further comprise the steps:

1) seeks the Na that occurring in nature exists ₂CO ₃, measure the wherein content of boron, select its content to be less than or far fewer than Xppm(X＜1) raw material;

2) CaO that exists on the market is gone boron process, comprising steps such as water purification soak, precipitates, dewaters.

3) will be through step 2) the CaO sampling and measuring, if confirm that wherein boron content is less than or does not reach this target far fewer than Yppm(, repeating step 2), until reach this target.

4) CaO in the step 3) is dried or dried to a certain extent, as long as wherein the quality of CaO can be calculated then passable.

5) with the CaO in the step 4) and the Na in the step 1) ₂CO ₃Mix with certain proportion, its ratio is with CaO and the Na of drying ₂The quality of O is calculated.

6) the slag agent of the mixing in the step 5) silica flour with certain proportion is mixed.

7) use document 2 (document 2: Chen Yingtian,＜＜a kind of is in the blending means of the process Raw of purification process of high-purity silicon〉〉 number of patent application is that the method for 201110000236.1 defineds realizes the expanded of mixture, reach sufficient mixed uniformly purpose, make the front bar-shaped or block pre-mixture of melting.

We further illustrate the characteristics of the summary of the invention of above-mentioned prescription by following explanation:

1) the boron content among the CaO can be by step 2) the listed repeatedly water purification boron method of going of cleaning reduces, and this method is not only simple, and can realize low cost fabrication;

2) to Na ₂Boron content among the O is more much lower than requiring among the CaO, cheap raw material easy to use;

3) according to document 2, the Na in the prescription ₂CO ₃Can be used as expanded promotor, be convenient to make the white residue mixture of high uniformity;

4) in conventional formulation, because CaO and SiO ₂Ratio substantially be in the middle part of phasor, its eutectic point is lower, extremely near the fusing point of silicon, the volatilization of silicon is few in the melting, and silicon, slag separate and can realize with the precipitator method of long period, certainly, as everyone knows, precipitator method divided silicon can not reach cleaner purpose.Utilize the prefabricated mixture of new prescription, in the high melt process, temperature is higher, can cause the volatilization of a large amount of silicon, must shorten as far as possible smelting time, for reaching this purpose, use the silicon of this prescription can carry out according to the method in the document 3 easily with the separation of residue, describe simply, can realize by the method for shrend.

5) well-known, as oxygenant, employed SiO in the Performance Ratio conventional formulation of employed CaO in the new prescription ₂Performance poor, yet above prescription can be in conjunction with using prior art, namely the severe radiation catalysis method that proposes of document 1 uses light-catalysed method accelerating oxidation reaction;

6) although that CaO gets fusing point is higher, separately use can not be in slag practice purified silicon, yet at the Na described in the present invention's prescription ₂Other salts of O or Na are such as Na ₂CO ₃Adding the effect of solubility promoter is but arranged, can greatly reduce CaO-Na ₂The eutectic point of O system.

Specific embodiments for example

We use a kind of specific embodiment that the present invention is described in more detail: select industrial silicon, boron content is 15ppm, selects CaO, and boron content is 3ppm, selects Na ₂CO ₃, boron content is 0.5ppm.At first with CaO according to summary of the invention step 2) description go boron to process, repeat this treating processes and reach five times, the boron content decrease among the CaO is dried CaO to 0.08ppm, gets 9.4 kilograms of CaO after the oven dry, Na ₂CO ₃0.6 kilogram, 10 kilograms of industrial silicons produce pre-mixture according to the step of document 2, carry out melting according to the severe radiation catalysis method of the defined of document 1, and the boron content behind the sampling and measuring is 1ppm, and the purification factor reaches 15.

Claims

1. a production method of removing the slag agent of boron impurity in slag practice is characterized by, and the main component of slag agent is accompanied by the extremely micro-CaO-Na of boron impurity content of puffing process for its mixing ₂O realizes this extremely CaO-Na of trace of boron impurity that has ₂The step of O system is as follows:

1) seeks the Na that occurring in nature exists ₂CO ₃, measure the wherein content of boron, select its content to be less than the raw material of 0.5ppm;

2) CaO that exists on the market is gone boron process, comprising the water purification step of soaking, precipitate, dewater;

3) will be through step 2) CaO get and claim to measure, confirm that wherein the content of boron is less than 0.1ppm, if do not reach this target, repeating step 2), until reach this target;

4) CaO in the step 3) is dried;

5) with the CaO in the step 4) and the Na in the step 1) ₂CO ₃Mix with certain proportion, this ratio is described as Na ₂CO ₃Account for CaO and Na ₂CO ₃Mixed gross weight ratio is 2%～10%;

6) the slag agent of the mixing in the step 5) silica flour with certain proportion is mixed;

7) use bar-shaped or block pre-mixture before prescriptive procedure is made melting: the slag agent of the oxygenant of the silica flour of the industrial silicon of powdery and powdery composition in the described method in the situation that drying stir fully, to add in such mixture in the normal pressure atmosphere of the room temperature that is placed on cleaning behind a certain proportion of water purification, mixture is with heat release, foaming, boiling, temperature rises to 80 ℃-100 ℃, namely carry out so-called puffing process, total mass depending on mixture, this process continued dozens of minutes by several hours, until heat release and boiling process are complete, volumetric expansion after expanded is to several times or tens times of original volume, this process extremely is similar to the fermenting process of dough, to further stir through the mixture after expanded, send into extrusion machinery and carry out moulding, after the moulding, through drying course, in this process, all dry or partially desiccated, even if all oven dry, total mass after the oven dry will have than the total mass of original raw material a certain proportion of increase, explanation is in said process, there is crystal water to produce, mixture behind whole oven dry or the partially desiccated, the pre-mixture before the namely melting presents bar-shaped or block.

2. the production method of in slag practice, removing the slag agent of boron impurity according to claim 1, it is characterized in that the slag agent of the mixing in the step 5) silica flour with certain proportion is mixed described in the step 6), the ratio of this mixing, ratio with slag agent gross weight and silica flour weight represents, ratio is 0.8～1.2.