Process for separating silica from silicate-bearing materials

Abstract

A process for removing silicon from a silicate-bearing material. The silicate-bearing material is analyzed for its silicon content and mixed with a controlled quantity of carbon as indicated by the analysis. The carbon is limited to an amount less than the stoichiometric amount necessary to react with the silicon to form silicon carbide. The silicate-bearing material/carbon mixture is formed into a first phase and interposed with a second phase containing additional carbon to form a reaction mixture. The reaction mixture is subjected to a carbothermal reduction reaction to reduce silica in the silicate-bearing material to silicon monoxide. At the temperatures involved in the reaction, the silicon monoxide is in the gaseous phase and readily diffuses from the first phase into the second phase where the diffused silicon monoxide reacts with the additional carbon in the second phase to form silicon carbide. The silicon carbide formation reaction occurs in the gaseous phase so that the silicon carbide is deposited in the second phase in the form of fine fibers. The silicon carbide fibers may be separated from the reaction mixture residue by conventional mechanical separation techniques. The first phase residue has a reduced silica content and may also be mechanically separated from the second phase.