Chlorination of Alumina Obtained from Nepheline Concentrate Processing and Comparative Assessment of the Complete Aluminum Production Cycle

Аннотация

Abstract—Extended tests of alumina fluid chlorination are performed. The implementation of the chlorine technology is possible when using alumina, which has a high reactivity with chlorine. The improved nepheline technology for obtaining such an oxide is proposed: non-desilicated aluminate liquors undergo carbonization followed by separation of aluminum hydroxide with sodium hydroaluminosilicate and its calcination at 600–800°C. The proposed upgrade, compared to the existing method, is less energy intensive. Two-stage desilication is eliminated, and more favorable conditions are created for the low-temperature digestion of sintered material, reducing the secondary losses of alumina and alkali. The technological parameters of charge chlorination, both powdered and pelleted, are worked out on a scaled-up installation in fluidized bed conditions. The operational and capital cost of a complete aluminum production cycle based on the chlorine technology are evaluated in comparison with the conventional alumina production according to the Bayer process and subsequent electrolysis of cryolite-alumina melts. The comparative cost analysis has shown the advantages of the chlorine technology at the stage of aluminum chloride electrolysis (up to 30%) and the presence of additional costs at the stage of obtaining the intermediate product for chlorination. The chlorine method of aluminum production in modern conditions has the prospects of development not as a mass technology, but as an effective process for obtaining high-purity aluminum (HPA) in small workshops.