Iron Recovery from Bauxite Residue Through Reductive Roasting and Wet Magnetic Separation

Chiara Cardenia,Dimitris Panias,Efthymios Balomenos

doi:10.1007/s40831-018-0181-5

Chiara Cardenia, Dimitris Panias + Show 1 more

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https://doi.org/10.1007/s40831-018-0181-5

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Abstract

The scope of this work is to develop and optimize a reductive roasting process followed by wet magnetic separation for iron recovery from bauxite residue (BR). The aim of the roasting process is the transformation of the nonmagnetic iron phases found in BR (namely hematite and goethite), to magnetic ones such as magnetite, wüstite, and metallic iron. The magnetic iron phases in the roasting residue can be fractionated in a second stage through wet magnetic separation, forming a valuable iron concentrate and leaving a nonmagnetic residue containing rare earth elements among other constituents. The BR-roasting process has been modeled using a thermochemical software (FactSage 6.4) to define process temperature, Carbon/Bauxite Residue mass ratio (C/BR), retention time, and process atmosphere. Roasting process experiments with different ratios of C/BR (0.112 and 0.225) and temperatures (800 and 1100 °C), 4-h retention time, and, in the presence of N2 atmosphere, have proven almost the total conversion of hematite to iron magnetic phases (> 99 wt%). Subsequently, the magnetic separation process has been examined by means of a wet high-intensity magnetic separator, and the analyses have shown a marginal Fe enrichment in magnetic fraction in relation to the sinter.

Highlights

IntroductionBauxite is an important ore that is widely used to produce metallurgical-grade alumina (the precursor for aluminum production) and chemical-grade alumina/aluminum hydroxide for many industrial applications through the Bayer process [1]
Bauxite is an important ore that is widely used to produce metallurgical-grade alumina and chemical-grade alumina/aluminum hydroxide for many industrial applications through the Bayer process [1]
This work has demonstrated that iron oxides contained in bauxite residue have been transformed into magnetite and maghemite after roasting process in the presence of metallurgical coke as carbon source (C/BR ratio = 0.180) at 800 °C

Summary

Introduction

Bauxite is an important ore that is widely used to produce metallurgical-grade alumina (the precursor for aluminum production) and chemical-grade alumina/aluminum hydroxide for many industrial applications through the Bayer process [1]. Iron content in bauxite residue (14–45 wt%) is not as high as in average iron ores (60 wt%) used in the iron industry [7], the gradual depletion of available ores and the demand for sustainable industrial processing have encouraged technology development based on secondary raw materials with almost zero-waste production [15]. In this framework, iron recovery from bauxite residue has attracted major attention, as the iron recovered can be used as feedstock in the iron industry [11]

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