Silicon smelting process

A process for producing silicon via reduction of silicon dioxide with silicon carbide in a silicon smelting furnace, the silicon smelting furnace having

• (A) a furnace body, the furnace body being a substantially closed vessel, defining a reaction zone for containing solid reactants and molten silicon;
• (B) a shaft suitable for containing solid particulates of carbon and suitable for passing gases from the furnace body through the shaft, the shaft being attached to the top of the furnace body at a first opening in the furnace body;
• and
• (C) an energy source, said energy source being fit into the furnace body through a second opening in the furnace body;
• the process comprising:
• (D) providing an initial feed mixture to the reaction zone, said initial feed mixture consisting essentially of an equimolar mixture of silicon carbide and silicon dioxide;
• (E) loading the shaft with carbon, the quantity of carbon being essentially two moles of carbon per mole of the silicon dioxide in the reaction zone;
• (F) applying energy to the reaction zone to effect conversion of the initial feed mixture to molten silicon, gaseous silicon monoxide and carbon monoxide;
• the gaseous carbon monoxide passing through the shaft loaded with carbon, the gaseous silicon monoxide passing into the shaft and reacting with the carbon to form silicon carbide;
• (G) recovering the molten silicon from the reaction zone;
• (H) mixing the silicon carbide formed in the shaft with an essentially equimolar quantity of an additional portion of silicon dioxide to form a second mixture;
• and loading the second mixture to the reaction zone;
• (I) loading the shaft with carbon, the quantity of carbon being essentially two moles of carbon per mole of the silicon dioxide loaded to the reaction zone;
• (J) applying energy to the reaction zone to effect conversion of the silicon dioxide and silicon carbide to molten silicon, gaseous silicon monoxide and carbon monoxide;
• the gaseous carbon monoxide passing through the shaft loaded with carbon, the gaseous silicon monoxide passing into the shaft and reacting with carbon to form silicon carbide;
• (K) recovering the molten silicon from the reaction zone;
• and
• (L) repeating steps (H) through (K).