China Nonferrous Metallurgy

Secondary aluminum ash contains a large amount of alumina, aluminum and aluminum nitride, as well as some fluorides and chloride salts, which are hazardous wastes. At present, the commonly used aluminum recovery technologies, acid leaching method and alkali leaching method, have the problems of harsh process conditions, low recovery rate, high energy consumption, large material consumption and low added value of products. In this study, alkali sintering method was used to recover alumina from secondary aluminum ash. The effects of sintering temperature on aluminum nitride conversion, alkali aluminum ratio, sintering time and forming method on alumina recovery were investigated, and the main conclusions were obtained as follows. Under the experimental conditions of sintering temperature 1423K, sintering time 40min, alkali to aluminum ratio 1.1 and dry pressing, the maximum dissolution rate of alumina is 94.23%. Through the analysis of the composition and phase of the leaching residue of sodium aluminate clinker of secondary aluminum ash, the main components of the clinker after calcination by alkali sintering method are Al₂O₃ and Na₂O, accounting for 49.70% and 28.06% respectively, and the main components of the residue after standard leaching of clinker are CaO, Al₂O₃ and MgO. The contents were 25.46%, 20.27% and 15.80%, respectively; The decomposition rate of AlN in secondary aluminum ash is higher, which can reach more than 95%, and the leaching toxicity of resource products is below 30mg/L. In summary, this paper uses alkali sintering method for resource utilization of secondary aluminum ash, and realizes harmless treatment of secondary aluminum ash for nitrogen removal and fluorine fixation, which has the advantage of high utilization rate of environmentally friendly resources, and lays a theoretical foundation for subsequent large-scale industrialization.