冶金级硅和硅铁在真空电磁悬浮下除磷基础研究

Using relative inexpensive raw material, metallurgical grade silicon (MG-Si), as starting materials for the production of solar grade silicon is one of the most economical way to make solar cells. Traditional methods of refining is an effective way to remove most impurities in molten silicon with the exception of phosphorus and boron. Removing boron and phosphorus of silicon is one of important project in solar grade silicon production.Using vacuum electromagnetic levitation technology, dephosphorization from metallurgical grade silicon and ferrosilicon by vacuum electromagnetic levitation will be achieved in order to explor the rule how to control dephosphorization. The surface oscillation and the inner heat and mass transfer will be studied for the sake physical modeling under the effect of electromagnetie field and vaccum conditions. Explore the mechanism of suspended molten drops by the eddy current heating of vacuum electromagnetic levitation. The relationship conditions of thermodynamics and kinetics will be clarified for Dephosphorization in Si - P and Si - Fe - P system. The multi-component redistribution of solutes with vacuum electromagnetic levitation will be investigated in order to clarify the rule of coupling field with the electromagnetic field, temperature field and flow field on phosphorus removal effect. Finally, Using vacuum electromagnetic levitation technology solar grade silicon samples will be prepared from relative inexpensive raw material,metallurgical grade silicon. Achieve quantificational characterization of microstructure and dephosphorization from metallurgical grade silicon and ferrosilicon by vacuum electromagnetic levitation will be achieved in order to explor the rule how to control dephosphorization, which will promote the development the theoretical model and experimental basis for the application of technology.

冶金级工业硅作为太阳能级硅材料最初始的原料价格低廉，若直接用来作为太阳能电池的原料，将会极大的节约成本。传统的熔炼法是提纯该材料的有效手段，却较难以脱除熔融硅中的磷和硼。因此，硅的除去磷及硼成为制造太阳能级硅材料领域研究的重要课题。本项目拟采用真空电磁悬浮技术，实现冶金级硅和硅铁材料除去磷，探求真空电磁悬浮形成机理与除磷主动控制规律。研究悬浮高温熔滴表面振荡运动和内部传热传质规律，建立电磁场与真空耦合作用下液态熔滴的物理模型；探索电磁悬浮涡流效应对熔滴悬浮的机理，揭示Si-P 及 Si-Fe-P体系中磷的热力学、动力学的条件。探索真空电磁悬浮对多组元溶质再分配的作用，阐明电磁场、温度场、流场耦合场对除磷作用的规律。实现在真空电磁悬浮条件下，使用价格低廉的硅材料制备太阳能级硅，定量表征微观组织结构，揭示真空电磁悬浮形成机理与除磷主动控制规律，并为该应用技术提供理论和试验依据。

冶金级工业硅作为太阳能级硅材料最初始的原料其价格低廉，传统的熔炼法是提纯该材料的有效手段，却较难以脱除熔融硅中的磷。本研究从真空电磁悬浮机理出发，研究了冶金级硅及硅铁合金在真空电磁悬浮下除磷的机理，对揭示真空电磁悬浮条件下冶金级硅精炼机理有着重要的科学意义，对材料的提纯和新材料的制备有着重要基础理论价值。本研究主要研究内容、重要结果、关键数据包括：（1）研究悬浮高温熔滴稳定悬浮规律发现，熔滴悬浮平衡位置在悬浮线圈几何位置下2.5毫米处。金属熔滴在电磁悬浮熔化过程中振荡，当在线圈电流范围在300-450A的条件下，熔滴的振荡频率为10-30Hz之间。（2）研究真空电磁悬浮下冶金级硅和硅铁熔滴的温度场和多组元浓度场引发的对流效应表明：熔滴内部温度差在1-4K的范围内；熔滴内部的流场存在强烈的涡流，冶金级硅熔滴中心的流速可以达到0.583m/s；熔滴的形变比增加，熔滴内部的涡流不断发展，电磁搅拌效果不断增强，熔滴受到的电磁升温效果也不断增强。（3）研究冶金级和硅铁在高温凝固过程中的传热传质规律表明：电磁悬浮对熔滴凝固组织有很大的细化作用。当体系为高真空状态，温度区间是1450-2250K范围内时，电磁悬浮条件下熔滴的脱磷过程中，整个传质过程的主要限制性环节为液相边界层中的传质过程。随着精炼温度逐渐升高，扩散系数增大，传质系数由4.68E-05升高到5.76E-05。（4）真空电磁悬浮下冶金级硅和硅铁中去除磷与悬浮条件间的关联规律研究表明：电流，频率，材料性质、熔滴尺寸，线圈形状等参数的无因次数组与电磁力有定量的关联。（5）研究了耦合场对多组元溶质再分配的作用、磷迁移的机理、Si-P 及 Si-Fe-P体系中磷的热力学、动力学的条件。研究表明：在Ar-H2混合气氛条件下电磁悬浮精炼Si-Fe-P三元金属熔滴在高温1723K-2123k时表面生成的磷氢化合物以PH、PH2，PH3形式存在。