Evaluation of Factors on Removing Boron from Silicon by Slag Refining Under Atmospheric Conditions
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Upgraded metallurgical grade silicon (Si) is available for high-efficiency solar cells. In the present article, Si refining with CaO-SiO2-CaF2 slags is carried out under open atmosphere, and orthogonal analysis is applied to evaluate the influencing factors. The results show that the influence order of the objective factors is: (1) slag/Si ratio > (2) refining time > (3) original slag basicity > (4) CaF2 content and that the slag/Si ratio acts as the key factor in boron removal. It is observed that boron decreases effectively within 30 min refining period. Moreover, the slags are pulverized when the basicity is > 1.39 because of the β-γ phase transition of Ca2SiO4, and the pulverization is beneficial to the separation of Si from slag.
This work was supported by funding from the ShangNan ZhongJian Industrial Co., Ltd., in Shaanxi Province and Project of Natural Science Foundation of Fujian Province (Grant No. 2014J01209). The authors thank Ms. Karen Doyle, JOM Editorial Office, and Dr. Tao Wang, Subject Editor, for sincere help. The authors especially thank Associate Professor Qijin Cheng and research scientist Dr. Song He for the English revision.