Purification of alumina-containing sweepings by dry air classification methods

The article deals with the formation and processing of waste at aluminum production plants. Based on the analysis of literary sources and practical data, the reasons for the formation of metallurgical waste in the territory of the Russian Federation are established. The analysis of research conducted in scientific organizations is presented. It was found that one of the most promising for waste processing is alumina-containing sweepings formed during the production of liquid aluminum in Soderberg cells during various process operations. Alumina-containing sweepings are waste of complex variable composition swept away in electrolysis shops. It was found that alumina-containing sweepings consist of cryolite (Na₃AlF₆), chiolite (Al₃F₁₄Na₅), corundum (Al₂O₃), siderite (FeCo₃), pyrite (FeS₂), quartz (SiO₂), feldspar ((Ca, Na)(Al, Si) AlSi₂O₈), carbonaceous matter and (NaF)•1,5CaF₂•AlF₅ technogenic phase. Their processing is of interest due to the fact that they contain a significant amount of valuable components (Na₃AlF₆, Al₂O₃, AlF₃) that can be extracted and reused in aluminum production to reduce the cost per unit. The problem is that sweepings contain components (SiO₂, Fe₂O₃), which have a negative effect on the electrolysis process when in contact with electrolyte. The data obtained when studying the chemical composition of monofractions made it possible to conclude that the exclusion of the dark (grayish-black mass) with the maximum content of impurities (SiO₂, Fe₂O₃) will substantially solve the stated problem of the study. Based on the hypothesis put forward, the paper presents the results of 0—10 mm and 0—5 mm sweepings air classification in cascade-gravity and centrifugal classifiers. Based on the studies conducted, we recommend using 0—10 mm sweepings air classification in the cascade gravity classifier in the processing flow of alumina-containing sweepings of aluminum production.

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