Abstract
Slag refining is one of the few metallurgical methods for efficient removal of boron from silicon. In industrial slag refining for production of silicon for photovoltaic applications, the relationship between the slag composition and the mass transfer rate of boron from metal to slag is of great importance. The kinetics of boron removal from liquid silicon during slag refining has been investigated in the present work by means of several small-scale experimental series at temperatures between 1,600°C and 1,650°C. Slag and metal, in batch weights of 30 g, were heated together in a graphite crucible placed in a resistance-heated tube furnace. The slags were produced from powdered SiO2, CaO, and MgO. The oxides applied were of high purity. Experiments were carried out at slag-to-metal ratios of 1 or 2, where the silicon initially contained approximately 250 ppm boron. Metal–slag mass transfer coefficients were calculated based on chemical analyses of the silicon and ranged from 1.7 μm/s for slag consisting of equal amounts of SiO2 and CaO by weight, to 4.3 μm/s for a 40%–40%–20% SiO2-CaO-MgO slag.
Similar content being viewed by others
References
J. Cai, J.-t. Li, W.-h. Chen, C. Chen, and X.-t. Luo, Trans. Nonferrous Metals Soc. China 21, 1402–1406 (2011).
A.A. Istratov, T. Buonassisi, M.D. Pickett, M. Heuer, and E.R. Weber, Mater. Sci. Eng. B Solid State Mater. Adv. Technol. 134, 282–286 (2006).
M.D. Johnston and M. Barati, Sol. Energy Mater. Sol. Cells 94, 2085–2090 (2010).
K. Morita and T. Miki, Intermetallics 11, 1111–1117 (2003).
L.A.V. Teixeira and K. Morita, ISIJ Int. 49, 783–787 (2009).
L.A.V. Teixeira, Y. Tokuda, T. Yoko, and K. Morita, ISIJ Int. 49, 777–782 (2009).
D.-w. Luo, N. Liu, Y.-p. Lu, G.-L. Zhang, and T.-j. Li, Trans. Nonferrous Metals Soc. China 21, 1178–1184 (2011).
H. Nishimoto, K. Morita, in Supplemental Proceedings from The Minerals, Metals & Materials Society. (Wiley, 2011).
FactSage, version 6.2, 2010. www.factsage.com.
J.A. Duffy and M.D. Ingram, J. Non-Cryst. Solids 21, 373–410 (1976).
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Krystad, E., Tang, K. & Tranell, G. The Kinetics of Boron Transfer in Slag Refining of Silicon. JOM 64, 968–972 (2012). https://doi.org/10.1007/s11837-012-0382-5
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11837-012-0382-5