Model Implementation of Boron Removal Using CaCl{sub 2}-CaO-SiO{sub 2} Slag System for Solar-Grade Silicon

Journal Article · Fri Dec 15 04:00:00 EST 2017 · Metallurgical and Materials Transactions B, Process Metallurgy and Materials Processing Science

DOI:https://doi.org/10.1007/S11663-017-1105-7· OSTI ID:22856061

Chen, Hui; Wang, Ye; Zheng, Wenjia; Li, Qincan; Yuan, Xizhi ^[1]; Morita, Kazuki ^[2]

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1. Sichuan University, School of Chemical Engineering (China)
2. University of Tokyo, Department of Materials Engineering (Japan)

A new CaCl{sub 2}-CaO-SiO{sub 2} slag system was recently proposed to remove boron from metallurgy-grade silicon by oxidized chlorination and evaporation. To further investigate the boron transformation process at a high temperature, a model implementation to present the transfer of boron from molten silicon to the gas phase via slag is introduced. Heat transfer, fluid flow, the chemical reactions at the interface and surface, the mass transfer and diffusion of boron in the molten silicon and slag, and the evaporation of BOCl and CaCl{sub 2} were coupled in this model. After the confirmation of the thermal field, other critical parameters, including the boron partition ratios (L{sub B}) for this slag from 1723 K to 1823 K (1450 °C to 1550 °C), the thicknesses of the velocity boundary layer at the surface and interface, the mass transfer coefficients of the boundary layer at the surface and interface, and partial pressure of BOCl in the gas phase were analyzed to determine the rate-limiting step. To verify this model implementation, boron removal experiments were carried out at various temperatures and with various initial mass ratios of slag to silicon (μ). The evaporation rate of CaCl{sub 2} was also measured by thermogravimetry analysis (TGA).

• OSTI ID: 22856061
• Journal Information: Metallurgical and Materials Transactions B, Process Metallurgy and Materials Processing Science, Journal Name: Metallurgical and Materials Transactions B, Process Metallurgy and Materials Processing Science Journal Issue: 6 Vol. 48; ISSN 1073-5615; ISSN MTBSEO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BORON
BOUNDARY LAYERS
CALCIUM CHLORIDES
CALCIUM OXIDES
CHLORINATION
DIFFUSION
EVAPORATION
FLUID FLOW
HEAT TRANSFER
MASS TRANSFER
METALLURGY
PARTIAL PRESSURE
SILICON
SILICON OXIDES
SLAGS
TEMPERATURE RANGE 0400-1000 K
THERMAL GRAVIMETRIC ANALYSIS