Slag refining at various viscosity conditions for SiC inclusion removal during Si scraps recycling

SiC inclusions in cast Si ingots are a key problem for Si quality and in the recycling of top-cut Si scraps. In this paper, SiC separation and Si recovery in the CaO–SiO2–MgO slag refining process were studied by varying temperature, slag/Si–SiC mass ratio, slag composition, and holding time. When the viscosity of the mixed system viscosity was 0.1575 Pa s, it was the best condition for the migration of SiC inclusions from Si to slag, and the removal ratio of SiC is 91.6%. The results indicated that low-viscosity slag and a long holding time are conducive to the migration of SiC. Further Image Pro software analysis showed that increasing the MgO content to 30mol% is beneficial to promote the migration of SiC. It is also found that the system viscosity effected the size of SiC in the slag phase. This work improves the removal of key inclusion SiC, reducing the cost of Si recovery.