Direct Reduction of Iron-Ore in Fluidized Beds

In order to carry out investigations of one of the most advantageous direct reduction processes, the fluidized bed reactors, computational tools need to be utilized. One such tool is the Computational Fluid Dynamics - Discrete Element Method (CFD-DEM) method. In this work, two of the most common types of models that represent the reactions between solid particles and fluids are implemented into the CFD-DEM library. Levenspiel (1999) describes these models as the Shrinking Particle Model (SPM), where the solid particle reacts with the fluid and changes its size, and the Unreacted Shrinking Core Model (USCM), where after reacting a product layer is formed around the layer that impedes the reaction rate. The SPM is used to verify communication between the CFD and DEM sides, whereas the USCM is used to represent the reduction of iron-ore. The USCM is validated with a case that considers only a single iron-ore particle that reacts with a gas mixture of CO and N2. The results are then compared with available experimental data that uses the ISO 4695 conditions at 950 ◦C and 50 Nl/min. We investigate possible parameters that influence the reduction process such as the particle porosity and pore diameter. Also, the reaction parameters such as the frequency factor, activation energy and the equilibrium constants are investigated by comparing the fractional reduction rates of simulations with experiments. These outcomes give us insight about the total reduction process.