Behavior analysis of silica in aluminum production by alumina carbothermic reduction–chlorination process in vacuum

In present work, the behavior of silica was investigated experimentally in the alumina carbothermic reduction process and chlorination process in the temperature range of 1173 K–1763 K. The phase of slags, surface morphology and composition of condensate were examined by means of XRD, SEM and EDS. The results showed that SiC was produced by SiO2 and C in the temperature range of 1573 K–1673 K, while alumina transformed into corundum completely, then Al4SiC4 was produced by SiC and intermediates (Al4C3 and Al4O4C) obtained during carbothermic reduction of alumina at about 1763 K. In the chlorination process, the silicon-containing materials in the condensate were not found. Because SiO2 consumed Al3C4 and Al4O4C, then the recovery rate of aluminum decreased. It was inferred that silica may be unfavourable for aluminum extracted from alumina by carbothermic reduction–chlorination process in vacuum.

► The behavior of silica in alumina carbothermic reduction and chlorination processes is studied.
► And Al4SiC4 produced would block chlorination reaction.
► This article is helpful to learn carbothermic reduction-chlorination processes of bauxite.