Abstract: A process for continuous or batchwise melting of silicon powder in particular, powder having a large amount of fines, and a melting crucible for carrying out this process are specified. The melting crucible is designed so that a melt pool having a certain minimum height and which is covered by unmelted silicon powder is provided. Thus, added material first comes into contact with silicon powder which is already present and only gradually reaches the melting zone. The amount of melt produced which exceeds the minimum height of the melt pool flows out of the melting crucible. The minimum height is maintained in the process by using a crucible which has a siphon-like outlet in the base.

Abstract: The slag portion can easily be removed from molten mixtures of slag and silicon by subjecting such mixtures to a hydrostatic pressure difference with respect to a space separated from them by one or more separating walls of graphite or silicon carbide, preferably provided with circular to slot-shaped apertures. Such separating walls are permeable to both the slag and silicon when present alone, but permeable only to the slag when a molten mixture of slag and silicon is present.

Abstract: Pure silicon is obtained in a semicontinuous process by reducing quartz sand with aluminum in a slag medium based on alkaline earth metal silicates. The slag serves thereby simultaneously as a solvent for the aluminum oxide that forms and as an extraction medium for impurities that occur. The silicon formed separates out of the silicate slag and can be separated off. The aluminum oxide produced by the reduction can be separated from the slag and used for recovery of reusable aluminum.