PLSR as a new XRD method for downstream processing of ores: – case study: Fe2+ determination in iron ore sinter

Abstract

The use of high-speed detectors made X-ray diffraction (XRD) become an important tool for process control in mining and metal industries. Decreasing ore qualities and increasing prices for raw materials require a better control of processed ore and a more efficient use of energy. Traditionally quality control of iron ore sinter has relied on time-consuming wet chemistry. The mineralogical composition that defines the physical properties such as hardness or reducibility is not monitored. XRD analysis in combination with Rietveld quantification and statistical data evaluation using partial least-squares regression (PLSR) has been successfully established to determine the mineralogical composition and the Fe2+ content of iron ore sinter within an analysis time of less than 10 min per sample. A total of 35 iron ore sinter samples were measured and evaluated using PLSR and the Rietveld method. The results were compared with wet chemistry data. PLSR results show accuracy for the Fe2+ content of ±0.14%. No pure phases, crystal structures, or complex modeling of peak shapes are required. The Rietveld method was used to quantify the total phase composition of the samples. The Fe2+ content could be calculated from all phases present. Both methods take the full XRD pattern into account and can be simultaneously applied on the same measurement. PLSR was found to be the more robust method if only Fe2+ results are required. The Rietveld method helps predict other parameters such as the compressional strength of the sinter by monitoring all existing phases (e.g., larnite, C2S, or silico-ferrite of calcium and aluminum phases).