Hydrogen direct reduction (H2-DRI) is the leading route to decarbonising ironmaking, and for current ore grades, in particular gangue rich Australian ores, is likely to proceed via direct reduction coupled with an electric smelting pathway. Iron ore agglomeration has long been optimised for the blast furnace and must be revisited for low-carbon routes. Specifically, sintering and reduction need to be considered together to achieve the appropriate chemistry, mineralogy and microstructural architecture.
Conventional iron ore sinter is designed around a calcium ferrite bonding matrix, principally the silico-ferrites of calcium and aluminium (SFCA and SFCA-I). The formation of these phases and their precursor calcium ferrites (C2F, CF, CFA) has been well studied in a blast furnace context (Nicol et al., 2018), but their behaviour under hydrogen at lower reduction temperatures remains essentially uncharacterised. Synthetic sinter analogues in the quaternary Fe2O3-CaO-SiO2-Al2O3 system provide the starting point (Webster et al., 2012). Sintered specimens of varied mineralogy are characterised by ex-situ Rietveld quantitative phase analysis, including amorphous content via an external standard approach, and later examined by hydrogen based thermogravimetric analysis (TGA). In situ laboratory X-ray diffraction follows phase evolution in real time through heating and cooling, capturing the formation and decomposition of the SFCA-series phases and a transient high-temperature phase observed over a narrow interval on cooling. A laboratory based, higher energy Mo source in-situ hydrogen reduction sample environment extends the work toward combining sintering and reduction within a single experiment, investigating the metallisation behaviour of complex mineralogical assemblages. Our goal is to establish validated ex-situ and in-situ protocols that integrate complementary characterisation capabilities and provide a workflow for identifying suitable sinter phase assemblages for hydrogen based ironmaking.