Smelting Reduction of Bauxite Residue and Beneficiation By-product in View of a Leachable Slag and Pig Iron Production

During the production of alumina with the commercial Bayer process, Bauxite Residue (red mud) is
produced, which is one of the largest industrial waste streams currently, in alumina production. A
more sustainable way for the production of alumina from bauxite without Bauxite Residue (BR)
production is the Pedersen Process, which also enables the use a wider range of bauxite qualities, in
terms of silica and iron. This process, is a combined pyrometallurgical-hydrometallurgical process.
In this study, two waste materials from the bauxite mineral processing and alumina industry are
treated to produce pig iron and a feedstock for alumina production. The scope of the present work is
to study the possibility of using the above raw materials in the Pedersen Process, for the utilization
of BR. Industrially produced Bauxite Residue (BR) and a calcium-carbonate rich bauxite mineral
beneficiation by-product are milled and then mixed in different portions with lime. These mixtures
are smelted at elevated temperatures and the iron oxide is reduced by carbon. This yields separable
pig iron and calcium-aluminate slag products. The slag and metal produced are thoroughly analyzed.
It is shown that the main slag phases, their amounts and distribution in the produced slags are
different for different utilized mixtures. Moreover, it is also shown that the produced slags are
promising for further application of the method to utilize the industrial waste and byproduct.