Study on the efficient removal of boron impurities in silicon melting using biomass ash additive

This study investigated the use of biomass ash as an additive for reducing the boron (B) content in industrial silicon (Si). Coffee shell, a biomass rich in alkali earth metals, was selected for its potential to effectively remove non-metallic impurities from industrial silicon. A series of single-factor experiments was designed to systematically examine the effects of biomass ash content, smelting temperature, and refining time on B removal. The experimental results indicated that under optimized process conditions, the ideal biomass ash addition was 5 wt.%, the suitable smelting temperature was 1500℃, and the optimal refining time was 240 min. Under these conditions, the B content in industrial Si was significantly reduced from 100.46 ppmw to 12.08 ppmw, thereby achieving a removal rate of 87.98%. This method offered a novel approach for purifying industrial Si and facilitating the effective utilization of biomass resources. It has significant implications for advancing the sustainable development of the Si materials industry.