冶金级硅熔渣精炼深度除硼研究

发布时间：2018-01-03 19:36

本文关键词：冶金级硅熔渣精炼深度除硼研究　出处：《昆明理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着全球能源消耗增加,太阳能光伏迅速发展,现已成为新能源行业中的重要部分。太阳能级多晶硅是生产制造太阳能电池的重要原料。冶金法由于成本低、能源消耗低、对环境污染小等优点,已成为制备太阳能级多晶硅的重要方法。冶金级硅中硼、磷以及其他杂质的去除是冶金法面临的重要课题。太阳能级多晶硅对于杂质硼的要求是低于0.3ppmw,因为硼会降低少子寿命,从而影响太阳能电池的光电转换效率。本论文以冶金级硅中杂质硼的深度去除为研究目的,通过两种新型三元熔渣CaO-SiO2-ZnCl2和CaO-SiO2-Zn0来探索熔渣精炼除硼的最优实验条件。还对B203在CaO-SiO2二元熔渣中的扩散传质问题进行实验研究,明确了造渣除硼过程的限制性环节。利用CaO-SiO2-ZnCl2和CaO-SiO2-ZnO三元系作为造渣剂,分别在电阻炉和感应炉中对冶金级硅进行精炼除硼实验。结果表明:(1)在电阻加热条件下,对于CaO-Si02-ZnCl2渣系,20%ZnCl2添加量时除硼效果最好,可将硼含量降低到11.95ppmw;对于CaO-SiO2-Zn0渣系,10%ZnO添加量时除硼效果最好,可将硼含量降低到7.51ppmw。两种渣系的除硼效果都随渣硅比的增加而增强,当渣硅比为2:1时除硼效果最好,硼含量分别降低到7.92ppmw和12.09ppmw。精炼时间为3h时,两种渣系可以分别将杂质硼去除至8.91ppmw和8.02ppmw。精炼温度为1823K时,硼含量分别降低到11.95ppmw和13.41ppmw。(2)在电磁感应加热条件下,46%CaO-46%SiO2-8%ZnO熔渣可以将硅中硼含量从12.94ppmw降低至2.18ppmw。通过酸洗可以使硅中硼含量进一步降低至1.52ppmw,去除率提高到88.25%。(3)精炼硅中残留锌经过酸洗以后可进一步降低至4ppmw;通过真空蒸馏处理以后精炼硅中的锌可以降低至0.05ppmw。利用毛细管-熔池扩散装置对B203在37%Ca0-63%Si02二元熔渣中的扩散系数进行了实验测定。并根据37%Ca0-63%Si02二元熔渣精炼实验结果计算了 B203在二元熔渣中的传质系数,从而得到了反应界面与熔渣间的边界层厚度。结果表明:在1723K温度下,在4mm孔径石墨毛细管中扩散30min后,B203在37%Ca0-63%SiO2渣中的扩散系数为5.265×10-9m2/s。利用37%CaO-63%Si02熔渣在直径为35mm的刚玉坩埚中对冶金级硅进行造渣精炼,可以得到B203在37%Ca0-63%SiO2熔渣中的传质系数为6.2×10-6 m/s。渣硅反应界面和熔渣一侧的有效边界层厚度为0.849mm。由此发现B203在熔渣中传质过程是熔渣精炼除硼的限制性环节。
[Abstract]:With the global increase in energy consumption, the rapid development of solar photovoltaic, has become an important part of the new energy industry. Solar grade polysilicon production is an important raw material for manufacturing a solar cell. The metallurgical method because of low cost, low energy consumption, little pollution, has become an important method for preparation of solar grade silicon from metallurgical grade silicon. In the removal of boron, phosphorus and other impurities is an important subject in metallurgy face. Solar grade polysilicon is lower than 0.3ppmw for the impurity boron requirements, because boron will reduce the lifetime, thus affecting the photoelectric conversion efficiency of solar cell. In this paper, boron impurities in metallurgical grade silicon removal depth for the purpose of the study by two new three yuan slag CaO-SiO2-ZnCl2 and CaO-SiO2-Zn0 to explore the optimal experimental conditions of boron slag in refining. The diffusion B203 in CaO-SiO2 two yuan in the slag. The experimental study, the slagging boron restricted link process. Using CaO-SiO2-ZnCl2 and CaO-SiO2-ZnO three series as slag, respectively of metallurgical grade silicon on resistance furnace and induction furnace refining experiment of boron removal. The results showed that: (1) under the condition of heating resistance, for CaO-Si02-ZnCl2 slag system, adding amount 20%ZnCl2 when the boron removal effect is the best, the boron content was reduced to 11.95ppmw; for CaO-SiO2-Zn0 slag system, 10%ZnO adding boron removal effect is best, can be reduced to the boron content of boron removal efficiency of 7.51ppmw. two kinds of slag are increased with the increase of the ratio of silicon slag increases, when the silicon slag ratio was 2:1 boron removal the best effect, the boron content were reduced to 7.92ppmw and 12.09ppmw. refining time of 3H, two kinds of slag can respectively be boron removal to 8.91ppmw and 8.02ppmw. refining temperature is 1823K, the boron content were reduced to 11.95ppmw and 13.41ppmw. (2) in electrical The magnetic induction heating conditions, 46%CaO-46%SiO2-8%ZnO slag can be boron content in silicon is reduced from 12.94ppmw to 2.18ppmw. by pickling can make silicon boron content further reduced to 1.52ppmw, the removal rate increased to 88.25%. (3) after pickling after zinc refining can be further reduced to 4ppmw residues in silicon; by vacuum distillation after processing in silicon zinc refining can be reduced to 0.05ppmw. by capillary - pool diffusion device was measured on the diffusion coefficient of B203 in 37%Ca0-63%Si02 of two yuan in the slag. The mass transfer coefficient and refining experimental results to calculate B203 in two yuan in two yuan according to the 37%Ca0-63%Si02 slag slag, thus obtained the thickness of boundary layer and the interface reaction between the slag. The results showed that: at the temperature of 1723K, 30min in 4mm graphite capillary pore diffusion after the diffusion coefficient of B203 in 37%Ca0-63%SiO2 slag is 5.265 * 10-9m2/s. by 37% CaO-63%Si02 slag in diameter of corundum crucible 35mm in metallurgical grade silicon slag refining, mass transfer coefficients can be obtained in B203 37%Ca0-63%SiO2 in the slag for the boundary layer thickness of 6.2 * 10-6 m/s. silicon slag and slag on the side of the interface reaction of 0.849mm. which found mass transfer in slag B203 slag removal is the limiting step of boron refining.

【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN304.12

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