Phosphorus Removal in Metallurgical-Grade Silicon via a Combined Approach of Si-Fe Solvent Refining and SiO<sub>2</sub>-TiO<sub>2</sub>-CaO-CaF<sub>2</sub> Slag Refining

Phosphorus Removal in Metallurgical-Grade Silicon via a Combined Approach of Si-Fe Solvent Refining and SiO<sub>2</sub>-TiO<sub>2</sub>-CaO-CaF<sub>2</sub> Slag Refining

As a critical impurity in the production of solar-grade silicon, the concentration of phosphorus (P) significantly affects photoelectric conversion efficiency. To address the challenge of P removal in solar-grade silicon production, this study proposes a combined process of Si-Fe solvent refining an...

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Bibliographic Details
Main Authors: Yi Zhong, Qing Zhao, Juncheng Li
Format: Article
Language:English
Published: MDPI AG 2025-06-01
Series:Metals
Subjects:
metallurgical-grade silicon
phosphorus removal
solvent refining
slag treatment
Si-Fe-Ti phase
Ca<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>
Online Access:https://www.mdpi.com/2075-4701/15/6/668
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Summary:As a critical impurity in the production of solar-grade silicon, the concentration of phosphorus (P) significantly affects photoelectric conversion efficiency. To address the challenge of P removal in solar-grade silicon production, this study proposes a combined process of Si-Fe solvent refining and SiO<sub>2</sub>-TiO<sub>2</sub>-CaO-CaF<sub>2</sub> slag treatment. Under conditions utilizing collaborative refining with an alloy composition of Si-10 wt. %Fe and a slag composition of 32 wt. %SiO<sub>2</sub>-48 wt. %CaO-10 wt. %TiO<sub>2</sub>-10 wt. %CaF<sub>2</sub>, the removal rate of P in silicon can reach up to 96.8%. This paper investigates the effectiveness of combining solvent refining with slag making under fixed conditions of a Si-10 wt. %Fe alloy paired with various slag systems (no slag addition, binary slag SiO<sub>2</sub>-TiO<sub>2</sub>, ternary slag SiO<sub>2</sub>-CaO-TiO<sub>2</sub>, and quaternary slag SiO<sub>2</sub>-TiO<sub>2</sub>-CaO-CaF<sub>2</sub>). Based on the experimental results, the optimal TiO<sub>2</sub> content in the slag system for maximizing P removal was analyzed and determined. Finally, leveraging both theoretical analysis and experimental findings, the mechanism of P removal was elucidated as a dual process: P is oxidized into Ca<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> within the slag phase, and residual P is captured by the Fe-Si-Ti ternary phase.
ISSN:2075-4701

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