# Rudomain Iron Ore Treatment by High-Temperature Reduction
## 3 Results and Discussion
### Material Research of Metallised DRI pellets  
The material research of the produced DRI pellets was primarily focused on the examination of the highest quality products and on the identification of differences in the quality of metallised DRI pellets. The study was carried out with the following samples of metallised pellets that were produced from the Rudomain ore (R7 sample):  
DRI 1--a sample obtained by reduction in the Marsh furnace (designated as MF2);  
DRI 3--a sample obtained by reduction in the electric induction furnace (designated as EIF8). The total Fe content of the DRI pellets was analysed by two methods: with XRF and AAS analysis. High agreement in the analysis of total Fe was achieved within both methodologies in the metallised products. The identification of the chemical composition of DRI pellets (Table 6) showed that DRI 1 sample with Fe\({}_{\text{TOTAL}}\) of 78.08 wt% approached the maximum theoretical value of Fe\({}_{\text{TOTAL}}\) (80 wt%) for 100% reduction of Rudomain. The calculated degree of reduction for DRI 1 was 95.6%. The metallised product DRI 1 exhibited a low content of total carbon (0.68%, analysed by IR with an Elemental Vario device); this result proved not only the effective utilisation of a carbon-based reducing agent (charcoal) but also the fact that the amount of produced carbides (primarily Fe\({}_{3}\)C) was not large. The contents of undesirable phosphorus and sulphur impurities were very low for DRI pellets. The sulphur content was analysed not only by XRF analysis but also by IR analysis using the Elemental Vario device. There was a high correlation with both methodologies. In the process of metallisation in EIF, we did not manage to reduce the Rudomain iron ore to the same extent as was achieved with the Marsh furnace (DRI 1). The calculated degree of reduction with the DRI 3 sample was 79.3%. Figure 11: Tests of reduction in EIF using an IR camera. An X-ray diffraction analysis showed that the content of SiO\({}_{2}\) (analysed by the XRF) was present in Rudomain samples in the form of silica, and the F\({}_{\text{TOTAL}}\) was contained in form of hematite. In addition to these major phases, we also identified a complex compound of cronstedtite (chemically alkaline iron silicate Fe\({}^{2+}\)Fe\({}^{3+}\)(Si,Fe\({}^{3+}\))\({}_{2}\)O\({}_{5}\))(OH)\({}_{4}\) and a complex of hydroxides of iron silicates. We also identified a non-stoichiometric form of magnetite but with a low probability of occurrence (Table 7). An X-ray phase analysis of the metallised product DRI 1 confirmed reduction processes by identifying iron-based phases (metallic Fe, ferrosilicon, and iron carbide) that corresponded to the chemical composition of the samples. Furthermore, the DRI 1 sample contained free graphite, silica, and a high-temperature form of cristobalite (Table 8). A subsequent microscopic EDX analysis carried out using the Tescan MIRA3 microscope confirmed that there were differences between the quality of DRI 1 (the best product of metallisation in optimal reduction conditions in the Marsh resistance furnace) and the quality of DRI 3 (the product of metallisation in the electric induction furnace) metallised pellets. The microstructure of DRI 1 contained a significantly higher amount of grains formed by the reduction than those observed in DRI 3 pellets produced in EIF. Major parts of the DRI 1 sample consisted of continuous formed areas of metallic iron, low-carbon iron carbide (Fe\({}_{2}\)C\({}_{0.05}\)), and ferrosilicon with a low silica content (Fe\({}_{3}\)Si). The microstructure of the DRI 1 sample was observed to also contain cristobalite (SiO\({}_{2}\)) located on the surface of the iron areas formed by the reduction. Cristobalite is a high-temperature form of the original silica contained in the Rudomain ore. The microstructure also contained the signs of the reduction mechanism, in particular continuous zones of iron produced by reduction on the original hematite grains. Melted iron grains with residual carbon were also observed