Open Access Conference Proceedings

Alkaline metals like sodium and potassium are generally known as unwanted elements in ironmaking processes. Beside the negative effects on refractory and coke consumption, alkalis have negative influence on the mechanical stability of the feed material. Former research work has shown the correlation between alkali content and the destruction of iron ore pellets. To investigate the effects of sodium and potassium on all kinds of lumpy iron carriers, reduction and tumbling tests were executed under various experimental conditions. Limonitic and hematitic raw ores and pellets were doped by alkali bearing aqueous solutions to soak the particles. Investigations by SEM and microprobe showed different alkali adsorption properties of mineralogical phases of the feed materials. Elevated contents of sodium and potassium were detected in limonite, gangue and glass phases after soaking. The doped materials were reduced in a vertical retort furnace according to ISO standards and at conditions comparable to those of industrial processes. After tumbling of the reduced material the grain size distribution was determined. A significant effect of alkalis on disintegration, degradation and sticking behaviour of lumpy iron carriers during reduction could be demonstrated. Additionally the different impacts of sodium and potassium were quantified. Due to investigations on different types of lump ore and pellets, various effects of sodium and potassium on mechanical properties were measurable.

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