Can Penalty Elements in Iron Ore be Determined with XRF?

Mining & Minerals - Evaluations / Other Metals

Ali Somarin blogs that iron ores are rocks and minerals from which metallic iron can be economically extracted during the mining process. Waste elements other than iron (Fe) in iron ore dilute the overall grade of the ore and incur a smelter penalty. Penalty elements change the physical properties of iron and can impede the proper operation of the smelting facility. The ore beneficiation process at a mine is designed to remove as much waste and penalty elements as possible prior to ore transport and smelting. The phosphorous (P) content of the iron is a tightly controlled variable in steel making. It can increase the hardness and strength of steel when present between 700 and 1200 ppm, yet the presence of P > 2000 ppm can make steel brittle at room temperature. Many iron deposits are hosted in banded iron formations (BIFs).

These deposits are metamorphosed banded chert (a chemical precipitate in oceans composed mainly of SiO₂) and contain large amounts of hematite (Fe₂O₃). Silicon (Si) is a common penalty element in these iron ores. Most Si is slagged off during smelting, but at temperatures > 1,300 °C (2,327 °F) it can form an alloy with Fe. Aluminum (Al) is present in clays, micas, and feldspars in some iron ore deposits and in limestone flux used in steel making. Small amounts of Al (< 1%) can increase the viscosity of the slag, which impedes the operation of the furnace. Sulfur (S) can be present as sulfides in iron ore and the coal used in the smelting process. At concentrations > 300 ppm, S causes brittleness in hot iron and iron cannot be used in steel making. Modern steelmakers add manganese (Mn) in proportion to the S to remove it from the steel as a sulfide (MnS). To see the results, including the correlation curves comparing lab results vs. those obtained with the XRF analyzer, download the Penalty Elements in Iron Ore application note.

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