Abstract
The generation and accumulation of refinery slag in silicon processing is a matter of high importance. The slags researched in the paper contain up to 70% of Si elements. This negatively affects the efficiency of Si production due to lower product recovery. Hence, one of the possible ways to dispose of the slags is to process them aiming to produce additional Si and aluminium-silicon alloys. The paper shows that the slag main components are carbon silicide, quartz and cristobalite, amorphous silica, calcium and aluminum oxides, carbon and element silicon inclusions. It suggests a slag processing method that includes melting the infeed that contains slag, metallic aluminum, and flux at 1250-1350 °C. The flux used was calcium oxide and calcium fluoride. The paper covers the influence of various factors of silicon-containing slag processing (melting temperature, CaF2 content in the CaF2 and CaO flux, the size of the slag particles) on the silicon extraction. The resulting mathematical model equation, proven to be accurate, describes the extraction of silicon in the form of Al-Si alloy from the refinery slag. The max silicon to alloy extraction rate equaled 51.43 % and was obtained at 1350 °C, the CaF2 content in (CaF2+CaO) equaled 20% with the slag particle size of 1.21 mm.
Keywords:
silicon production, refining slag, slag processing, silicon extraction, Al-Si alloys