Abstract

Carbothermic reduction of iron ores in blast furnaces leads to 3-4 Gt of CO2 released into the atmosphere annually, which accounts for about 10% of global CO2 emissions. SIDERWIN, an alternative carbon-free iron-making technology under development by ArcelorMittal Global R&D, involves the direct production of metallic iron by low-temperature (110 °C) aqueous electrolysis of iron ore suspensions in a highly concentrated caustic electrolyte. The effectiveness of this new technology has been so far mainly demonstrated at bench scale for the case of electroreduction of synthetic iron oxides. According to ArcelorMittal's previous work, the current density and efficiency of the process are drastically impacted by the mineralogy of the iron oxide compound/mineral and its purity. Given the wide range of mineralogical composition of iron ores, there exists a need to systematically study the effect of ore mineralogy on the conversion of iron oxide minerals to metallic iron deposits and to identify ways for their efficient electrolysis. As the first step, a good understanding of the reduction mechanism and the effect of mineral properties on iron deposition in an iron oxide suspension with planar electrode configuration is required. A recently-launched research project at McGill University under the sponsorship and support of ArcelorMittal aims to contribute to the development of this potential breakthrough technology via a comprehensive study integrating mineral processing and hydrometallurgy laboratory technical expertise. In particular as part of the project we seek to establish how the mineralogy of different origin iron ores (after their detailed characterization) impacts the electrolytic metal deposition operation in terms of current density & efficiency as well as purity & morphology of metal deposit. In this presentation, we plan to give an overview of the project and provide highlights from the collected so far bench scale electrolytic tests. In particular the reactivity of several iron oxide minerals and ores will be discussed and compared to previous published data. An important finding is that the use of planar electrodes and mechanical agitation is important in promoting the electrochemical reduction of the iron oxide particles and the formation of metallic iron (> 97 wt.% purity) deposit at a high current density, twice as high at least in comparison to established non-ferrous (e.g. zinc) industrial electrolytic operations.

Acknowledgments: This work is supported via a NSERC/ArcelorMittalDofasco Alliance Grant