Direct reduction of iron (DRI) using hydrogen is considered one of the most viable green ironmaking methods. This method uses green hydrogen as the reducing agent, which reacts with oxygen in iron oxide, forming water vapor (as a byproduct), with no CO2 emissions. Because of its high heat and mass transfer, fluidized beds are being investigated for use in DRI. 

The aim of this project is to improve the understanding of reactive, cohesive particulate flows for the fluidized bed hydrogen-ironmaking process. Iron powder is a clean, safe, and cost-effective energy carrier, because of its high (volumetric) energy density. Fluidized beds have high heat and mass transfer rates between the fluid and solid phase and may be used for large-scale applications of iron fuel reduction. However, high particle-particle contacts can lead to sintering of fuel particles.

The goal of the first work package is, for the first time, to obtain experimental data (e.g. restitution coefficient) of particle-particle/wall interaction when the particle surface material is undergoing sticking/sintering at elevated temperatures. These data, describing the energy dissipation or cohesive force during particle collisions, are essential inputs for numerical simulations of such cohesive particulate flows, which are conducted at Eindhoven University of Technology.

The second work package aims to understand and prevent the sintering during hot fluidization of iron particles in a lab scale facility. A direct comparison of a reactive hot bubbling bed and a spouted fluidized bed with same dimensions (di = 5 cm, h = 50 cm) will be done to investigate changes in particle-particle contact to break cohesive bonds caused by sintering. The experimental investigation will span over different temperatures (up to 950 °C), gas velocities, H2/N2 ratios and for different reduction-oxidation cycles. Changes in reactivity of the material during operation will be evaluated with an online hydrogen sensor. The fluidization state is evaluated via fast Fourier transform of the measured bed pressure drop. Particle samples will be collected during hot operation with an attached water-cooled, nitrogen purged mechanism. The particles will be assessed regarding their reduction state, particle size and surface morphology.