A Formulation of Multi-interface Shrinking Core Model for Gaseous Reduction of Hematite

With the increasing interest in gas-based DRI production in shaft furnaces, there is a growing demand for a closed-form solution to describe the reduction rates of hematite to magnetite, magnetite to wüstite, and wüstite to iron. This study utilizes a mass balance approach to develop the governing equations of the multi-interface shrinking core model, which are then solved analytically. The innovation of this approach lies in its ability to generate a closed-form solution, with the potential to be applied to both single- and any multi-interface problems. The results are validated against findings from existing literature, and the kinetic parameters are calculated based on experimental data. Additionally, rate-controlling step analysis is performed by deriving the three rate equations in terms of various resistances and comparing their magnitudes. The findings show that as temperature and particle size increase, pore diffusion becomes the dominant controlling mechanism, overtaking interface resistance.