Low temperature reduction of iron oxide fines

Abstract

India continues to emerge as a major iron and steel producing country in the world and is likely to consolidate its position further, once the National Steel policy is fully realized. However, increase in steel production is likely to strain the natural resource and calls for technology to minimize waste. Blast furnace ironmaking is still and is likely to remain in near future the most dominant route for producing hot metal. It is well known that for production of one tonne of sized ore, the feed for blast furnace, almost an equivalent amount of undersize is generated. A major part of this undersize is converted to useful feed stock for blast furnace through sintering. However, extra fineness makes a significant fraction of this undersize unsuitable for sintering and approximately 18 – 25% of slime generated during washing of ROM ore adds up to the quantity of unutilized/underutilized fines. This fraction is of concern due to impact on ecology as well as loss of huge iron value. The current paper presents a brief review on various processes developed towards utilization of fines and their current status. It has been observed that none of the proposed processes could offer a commercially matured technology as an alternate to blast furnace iron making and thus energy intensive pelletization of fines and their subsequent reduction at relatively high temperature appears to be the only viable option, currently available. Thermodynamic consideration of gaseous reduction of iron oxide indicates that it is possible to convert hematite directly to metallic iron, bypassing the FeO stage at temperature below 570oC. A few fundamental studies have been reported, indicating feasibility of such low temperature reduction within a reasonable time. On the basis of analysis of existing alternate ironmaking propositions, the literature reporting on low temperature reduction and a few preliminary gaseous reduction experiments in the laboratory in static bed, the authors have proposed a conceptual scheme of counter current reactor for low temperature reduction of iron oxide fines.