Feasibility Study of the Use of Nepheline-Limestone Charges Instead of Bauxite

Nepheline is one of the raw materials used to produce alumina, which is the main component in the charge for the production of primary aluminum. Certain complications arise during the production process in the course of the charge’s heat treatment. This article discusses results of studies made of the formation of sublimates of alkali compounds during the dry sintering of a nepheline-limestone charge. It also addresses the matter of replacing imported “bauxite” alumina by Russian-made “nepheline” alumina. It is shown that a substantial portion of the sublimates is absorbed by the charge at different stages of its heat treatment. It is recommended that the remaining alkalis be taken out of the sintering operation by using a special bypass, which is similar to a practice employed in the production of Portland cement. The main theoretical results of the studies were corroborated in commercial trials performed together with the Danish company FLSmidth at its facilities in the U.S.