Elemental deportment and chemical structure evolution of iron ore during direct reduction in hydrogen atmosphere

Direct reduced iron (DRI) technologies have been developed as an alternative route for iron production alleviating the need for separate cokemaking and sintering operations. This study aimed to provide an insight into DRI production using H2 in terms of elemental content change and chemical structure evolution for improved environmental control of the process. In this work, a sample of goethite was treated from room temperature to 1000 °C in 10 vol% H2 in helium in a fixed-bed reactor. The investigated elements were divided into three groups: i) major elements (Fe and Al), ii) alkali and alkaline earth metal elements (mainly Na, K and Ca), iii) transition and post-transition metals (Ni, Cu, Zn, Pb, Cd, etc.) and iv) non-metal and metalloid elements (P, S, As, etc.) The elemental changes of iron ore with temperature were firstly determined by X-ray fluorescence (XRF) analysis and inductively coupled plasma–mass spectrometry (ICP-MS). X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and Raman spectrometry were employed to confirm the reactions and investigate the iron ore’s chemical changes during direct reduction. XRD analysis indicated the stepwise reduction of goethite → hematite → magnetite → wustite for the goethite sample. FT-IR and Raman spectrometry revealed the transformation of chemical groups with temperature. Results showed that no obvious changes could be noticed after heating the sample to 200°C in terms of the elemental contents and chemical structure. Further treatment of the sample to 500°C and subsequently 1000°C resulted in the content changes of some elements due to the weight loss of hydrated water by heating and reduction of the ore sample, respectively.