Research And Application Of Typical Impurity Behavior In Organic Silicon Smeltin

Organic silicon has special requirements for the content of typical impurities such as Fe,Al,Ca,Ti and P.Al and Ca can be removed by blowing oxygen refining,while Fe,Ti,P and other impurities have no effective refining removal method.In order to produce high-quality organic silicon products,manufacturers usually use high-quality silica（low Fe,Al,Ca,Ti,etc.）and high-quality reducing agent（high carbon and low impurity combination reducing agent,charcoal ratio is generally more than 50%）for production.charcoal consumption has problems of ecological damage,raw material procurement difficulties and high cost.This paper for the introduction of typical impurities in organic silicon,migration,distribution rules,on the basis of this,using low charcoal（20%）combination reducing agent,through raw material optimization group,strengthening smelting control,optimize refining in addition,etc.,test produced a high proportion（average 93.19%）of organic silicon products,for low cost and efficient production of organic silicon products explore a appropriate production technology path.The specific research contents include the following points:（1）The introduction,migration and distribution of typical impurities in the industrial silicon smelting system are analyzed by theoretical calculation.It is found that in the smelting process,the impurity Fe into the furnace gas is weak;Al and Ca impurities are deposited in the furnace,and some are reduced into crude silicon,and the proportion of entering the furnace gas is low,and the migration behavior of the two shows certain cooperativity.The equilibrium distribution of the impurity Fe is enriched in the industrial silicon products,while the impurities Al and Ca are enriched in the refined slag.（2）The transition behavior of typical impurities in the process of industrial silicon smelting is discussed in combination with thermodynamics.The study shows that the mixed Fe oxide will undergo deposition,reduction and combination into the furnace,and shows strong affinity between Fe-Si.As a result,the impurity Fe;the mixed Al oxide and Ca oxide will gradually change to calcium feldspar and accumulate,and gradually reduce Al and Ca to gaseous matter,and a large amount of gasification is absorbed with the furnace gas into the upper material layer.（3）The main phase transition and impurity evolution in electric furnace are analyzed,and the distribution of typical impurities is studied.The analysis shows that in the lower part of the loose material layer,some silica is completely converted intoαsquare quartz,the Al content is increased significantly;the porous silicon carbide forming layer is mainlyβSi C and Si,and theαSi C and Ca₃Al₂Si₃O₁₂;the main layer isβSi C,αSi C,Si,Ca₃Al₂Si₃O₁₂ andαsquare quartz;the silicon pool area is mainly composed ofβSi C,αSi C,Si,Ca₃Al₂Si₃O₁₂ and Ca₂Al₂Si O₇.Several impurities of Fe,Al,Ca and Ti mainly enter industrial silicon and silicon slag,among which Fe is easy to reduce into industrial silicon,Al and Ca mostly enter silicon slag after oxidation and refining,and Ti is distributed in industrial silicon and silicon slag;P mainly enters the micro silicon powder,and a small amount is distributed in industrial silicon.（4）The three impurity removal techniques of slag making refining,flux refining and directional solidification and the combination of several kinds of them were studied and analyzed.It was found that slag refining（Ca O-Si O₂ slag system）improved Al removal by 97.80%,but only29.97%and 40.74%;slag-directional coagulation combination can improve the removal rate of metal impurities up to 98.15%and 53.00%,but only 33.33%;slag-flux-directional coagulation combination for impurity removal,and the removal rate of Fe,Ti,and P reaches 97.79%,71.03%and 92.04%respectively.The results show that flux refining and vacuum directional solidification significantly improve the removal rate of impurities Fe,Ti and P,and achieve the purpose of combined refining.（5）The low carbon（20%）combined reducing agent was used to test the industrial production of organic silicon.The results show that it is feasible to produce high proportion of organic silicon products with low charcoal（20%）combined reducing agent through reasonable raw material distribution,strengthening smelting control,optimizing refining and removing impurity,and realize the industrial application of blue carbon in industrial silicon production.The analysis shows that Fe is mainly derived from silica and cleaned coal,with about 0.58 and 0.4;Al is also mainly derived from silica and cleaned coal,about 0.6 and 0.4;Ca is mainly derived from charcoal and cleaned coal,about 0.8 and 0.18;Ti is mainly derived from silica and cleaned coal,with more than 85%;P mainly comes from silica,with more than 90%.The control content of Fe in the product requires the control content of Fe in silica and cleaned coal;the control content of Ti in the product requires the control content of Ti in silica and cleaned coal;and the control content of P in the product requires the control content of P in silica.Although the impurities Al and Ca are easy to remove in the subsequent oxygen blowing refining,the oxides of both will have some impact on the smelting temperature and reducing agent consumption in the smelting process,so they should be controlled in raw materials according to certain requirements.