Coupled production of high purity silicon and alumina

A process for the production of silicon and alumina comprising the following steps:

• i. In an aluminothermic step, contacting an aluminium metal with
• a molten slag comprising an alkaline earth metal oxide and a silicon dioxide, or
• an alkaline earth metal oxide and a silicon dioxide particularly wherein the alkaline earth metal oxide comprises or essentially consists of calcium oxide,
• under conditions facilitating an aluminothermic reaction;
• thereby forming silicon and an alkaline earth metal oxide aluminate slag in separate phases;
• ii. separating the silicon and the alkaline earth metal oxide aluminate slag in a separation step;
• iii. in a conversion step, converting the alkaline earth metal oxide aluminate slag to alumina and alkaline earth metal oxide, wherein said alkaline earth metal oxide is re-fed in the aluminothermic step;
• characterized in that
• the aluminium metal of the aluminothermic step is provided by a procedure comprising the steps of
• melting of aluminium scrap or a combination of different aluminium alloys to yield a primary aluminium melt, particularly at a temperature of 700 to 1000° C., more particularly 800° C. to 900° C.;
• adjusting said primary aluminium melt to a content of
• 8 to 14% (w/w) of silicon, particularly 11.5% to 12.5% of silicon, more particularly 11.8% to 12.2% of silicon, or to 12.0% of silicon
• cooling said primary aluminium melt to below 660° C., particularly to 580 to 620° C., over 5 to 50 hrs, whereby a precipitate is formed, and said precipitate is separated from said aluminium melt, whereby a secondary aluminium melt is obtained which is used in the aluminothermic step
• after solidification or
• directly in molten form.