Currently, direct reduction of iron ore is used in many parts of the world to manufacture metallic iron (Direct Reduced Iron, DRI) at relatively high purity (86-94% total Fe, depending on the quality of the iron ore) and high metallization degrees (92-96%). It is often hot-compacted as Hot Briquetted Iron (HBI), for ease and safety of handling, shipping and storage. Iron ore is reduced in shaft, fluidized bed or rotary kiln furnaces in the solid state, using reformed natural gas, syn gas or coal as reductant.
HBI/DRI serve as a key ferrous feedstock material for EAF steelmaking. HBI/DRI with their very low content of metallic impurities dilute impurities contained in steel scrap used in EAFs and enable production of higher-grade steel products via the EAF route.
The bulk transport of DRI has inherent risks. Because no melting of the iron appears during DRI-production, it is porous or spongy in nature with a large surface to mass ratio. This allows easy access of gaseous reactants, in particular oxygen and water vapor, to the iron surface and makes DRI (and HBI) susceptible to re-oxidation (which is exothermic), especially in a hot humid environment, which in turn can lead to self-heating and temperature build-up and accumulation of hydrogen. The susceptible to re-oxidation depends not only on the surface area of the DRI and HBI but also on the chemical composition. Actually, a density of 5000 kg/m³ is defined to be needed that the material is safe for maritime transport. This density was defined without considering the effect of chemical composition of the DRI/HBI. Therefore the re–oxidation behavior of different sample types has to be investigated in order to define real values for required density depending on the type of the sample.
An excessive literature study should be carried out in order to evaluate the re–oxidation process and to define parameters influencing the re–oxidation behavior. Based on the results, methods should be determined, which allows to characterize the re-oxidation behavior of different industrial DRI/HBI samples. Preeliminary tests should be done using availible laboratory equibment at the Chair of Ferrous Metallurgy.