First steps in the endeavour to determine particle properties in the direct reduction process of iron ore pellets

The direct reduction (DR) of iron ores provides an environmentally friendly alternative to conventional blast furnace steelmaking, resulting in significantly reduced CO₂ emissions. In a DR shaft furnace, coarse and packed iron ore particles, as pellets or lumps, descend under gravity while a reducing gas mixture of hydrogen and carbon monoxide (syngas) crosses the system in the upward direction. During this descent, the mechanical properties of the particles, such as friction and cohesion, affect the ore flow and are influenced by temperature and composition changes due to gas-solid reactions. Quantifying solid phase flowability is crucial to prevent particle interlocking and stagnant zones. Standard apparatus and procedures were developed to characterise bulk flow properties for fine powders and cannot be used with coarse iron ores. This study addresses the challenge of pioneering an approach to calibrate a discrete element method (DEM) applied to coarse particles starting from experimental data, extracted from customised experiments run on slightly modified rotational shear testing equipment in conditions that do not allow the derivation of bulk properties, to characterize a simplified mechanical system composed of coarse wooden spheres. The close agreement between experimental data and DEM simulations validates this approach for large particles. The next step is to characterise iron oxide pellets under process conditions to understand the impact of cohesion and friction on flow properties and refine DEM model parameters for simulating the DR process accurately.