【作者】 刘燕；

【导师】 邢鹏飞；

【作者基本信息】 东北大学 ， 化学工程， 2010， 硕士

【摘要】 全球面临能源短缺与环境保护的双重压下,这促进了太阳能光伏产业的快速发展。而太阳能级晶体硅制备的关键技术被国外所垄断,导致我国太阳能级晶体硅主要依赖进口。在切割太阳能级晶体硅过程中,约50wt%的晶体硅被切磨成高纯硅粉进入到切割废料中。如能将废料中的高纯硅粉加以回收并作为制备太阳能级晶体硅的原料,既可实现资源的回收利用,还可减少我国晶体硅的进口；另外,作为磨料的碳化硅也很有回收价值。因此研究从太阳能级切割废料中回收高纯硅和碳化硅具有重要的应用前景和实际意义。本课题以挪威REC公司提供的太阳能级晶体硅切割废料为研究对象,通过XRD、XRF、化学定量分析、粒度分析等对废料物性做了详细的研究。结果表明：废料中含硅30.50wt%,碳化硅34.90wt%,水和聚乙二醇26.63wt%,铁及其氧化物5.36wt%,其他2.61wt%,粒度主要集中在1.0～23.8μm范围内。物理沉降实验,考察不同沉降时间、固液比、分散剂条件对切割废料中硅与碳化硅分离效果的影响。结果表明：在固液比为0.08,沉降时间为5h,含聚乙二醇的切割废料沉降效果较好,在此条件下得到的上层硅富集料中硅含量为79.OOwt%,碳化硅含量为12.83wt%,铁含量为6.84wt%,粒度分布在1.0-10.8μm范围内；下层料硅含量为10.32wt%,碳化硅含量为84.73wt%,铁含量为3.83wt%,粒度分布在1.2-23.8μm范围内。盐酸除铁实验,考察了浸出时间、浸出温度、盐酸浓度等囚素对硅富集料中铁浸出率的影响,并通过正交实验得到了最佳实验条件：浸出时间为3h,浸出温度为70。C,浸出液浓度为15wt%,搅拌速度为150r/min,液固比为4：1,在此优化条件下铁浸出率可达97.00wt%,硅富集料中的铁含量由6.84wt%降低到了0.22wt%。碳化硅的回收实验,研究了不同酸浓度、反应时间、反应温度等条件对沉降底料中碳化硅纯度的影响,结果表明最佳条件是：5wt%氢氟酸和8wt%硝酸,反应时间为2h,反应温度为60℃,液固比为5：2,搅拌速度为120r/min,在此条件下浸出底料中碳化硅纯度为98.54wt%,符合碳化硅切割磨料要求的纯度标准；粒度主要集中在1.2-11.4μm范围内,占总体积的90%。高温熔炼初探实验,结果表明温熔炼将硅富集料中的硅凝聚到一起是可行的。更多还原

【Abstract】 Because of the shortage of the energy and the problems of environment, the reproducible energies, especially PV(photovoltaic) industry, have got rapid development in recent years. The solar grade silicon(SOG-Si), which is used for manufacturing solar cell, mainly prepared by method of improved-Siemens technology. Its key technology is monopolized by few overseas enterprises, which made China have to import great amount of SOG-Si very year. Even though, during the crystalline silicon rod cutting process, about50wt%of it was loss since crystalling silicon is cut into high purity silicon powder and become a part of slurry. If high purity silicon in slurry can be recycled and used as raw materials for preparing solar-grade silicon, it will have an important significance for both resource recycling and reducing the import amount of solar-grade silicon in our country. In addition, silicon carbide powder in slurry, which is use as abrasive in cutting crystalline silicon, can be reused if it can be recovered from the slurry. Therefore, recovering high purity silicon and silicon carbide powder from the slurry is becoming more and more important with the development of PV industry.In this thesis, the recovery of high purity silicon, silicon carbide from the cutting slurry of crystalline silicon was investigated. The cutting slurry is provided by Norway’s REC solar company. The slurry is composed of high purity silicon30.50wt%, silicon carbide34.90wt%, polyethylene glycol (PEG) and water26.63wt%, and a small amount of iron5.36wt%. Their sizes are distributed between1.0μm and23.8μm.Physical sedimentation experiments for the silicon enrichment from slurry are carried out in detail. The sedimentation time, solid-liquid ratio and other factors on the effect of silicon enrichment have been studied. The results show that the optimum sedimentation conditions are as follows:solid-liquid ratio is0.08, sedimentation time is5h, in the condition of containing PEG in slurry, and optimum results obtained with the optimum conditions as:silicon in enrichment layer is up to79.00wt%and silicon carbide is decreased down to12.83wt%, their sizes are distributed between1.0μm and10.8μm; silicon in sedimentation layer is10.32wt%and silicon carbide is84.73wt%. Their sizes are distributed between1.2μm and23.8μm.The removal of iron from enriched silicon slurry is also researched by the method of hydrochloric acid leaching. In the process of removing, leaching time, leaching temperature, hydrochloric acid concentration and other factors on the effect of iron removing have been investigated in detail, and the optimum leaching conditions were obtained. The best leaching conditions are as follows:the temperature is70℃, the concentration of hydrochloric acid is15wt%, the leaching time is3h and the liquid-solid ratio is4:1. The removal rate of iron in enriched-silicon slurry is up to97wt%by using the optimum leaching conditions.During the research of recycling silicon carbide powder from cutting slurry, mixed acid concentration, reaction time, reaction temperature and other factors on the effect of impurities removing have been discussed in detail. The best reaction conditions are as follows:mixed acid concentration is5wt%HF and8wt%HNO3, reaction time is2h, the temperature is60℃, the liquid-solid ratio is5:2. With the optimum conditions, silicon carbide with the purity of98.54wt%is obtained, which can match the standards of purity silicon carbide abrasive. Their sizes are distributed between1.2μm and11.4μm.Melting preliminary experiments of the enriched silicon slurry with content of85.04wt%have been studied, the results show that melting of agglomerating silicon from cutting slurry is feasible.更多还原