The Rate of Boron Removal from Molten Silicon by CaO-SiO2 Slag and Cl2 Treatment

Abstract

In order to optimize a boron removal process by slag refining to obtain solar grade silicon, the rate of boron removal from molten silicon using CaO-SiO2 slag was investigated at 1823 K in an Ar atmosphere. The rate of boron removal was found to be controlled by mass transfer in molten slags, and the mass-transfer coefficient of boron in molten slag in the present experimental condition was evaluated. Some experiments on chlorination of boron in silicon and that of borate in slag using Cl2 gas were also carried out. Experimental results showed that the slag refining process with chlorination was proposed as a promising method for the boron removal from molten silicon.

Keywords

• solar grade silicon
• refining
• boron
• slag
• chlorination
• mass transfer