The silicon off-grade or slag material is a by-product from production of silicon metal of ≥99% purity. To ensure the quality of the product line, top portion of the melt is separated when draining from the electric-arc furnace. The less pure portion of silicon metal typically contains higher contents of iron, aluminum, calcium and other slags. With the employment of density separation machines, different grades of silicon slag/off-grade silicon are segregated efficiently.
The silicon slag or off-grade material is much cheaper than ≥99% purity silicon metal, and has many industrial
For example, It is Used as de-oxidizing agent in steel production to reduce oxygen levels in the melt via reaction such as
Si + 2 O (in liquid Fe) ––> SiO2
(SiO2 is formed as a solid dispersed in molten Fe, and subsequently floats to the surface of the melt. It is
removed by either skimming or by draining molten iron from the bottom);