Efficient improvement for the direct reduction of high-iron red mud by co-reduction with high-manganese iron ore

Abstract

Millions of tons of red mud produced as a by-product of the alumina industry by Bayer process not only threatens the environment but also causes waste of secondary resources. To recover iron from red mud, the technology of reduction roasting-magnetic separation to treat high-iron red mud was developed; however, it was difficult to upgrade by separating iron and alumina. In this paper, the effects of high-manganese iron ore on the direct reduction process of high-iron red mud were investigated through various tests such as reduction temperature, reduction time, C/Fe mass ratio, and addition amount of high-manganese iron ore. The results showed that the metallization rate of the direct reduction of high-iron red mud reaches 84.07% roasting at 1150 °C, 150 min and C/Fe mass ratio of 2.0. By synergistic reducing with 60% high-manganese iron ore, the metallization rate increased to 93.52%. The results of phase and microstructure evolution analysis showed that adding high-manganese iron ore, the content of ilmenite, hercynite and fayalite were reduced, and pyrophanite, galaxite and tephroite were formed, indicating that MnO, one of the reduction products of high-manganese iron ore, can react with ilmenite, hercynite and fayalite to generate pyrophanite, galaxite and tephroite in the reduction process, and further dissociated FeO, which was conducive to the reduction of high-iron red mud.