Multiscale modeling of counter-current moving bed reactor for direct reduction of iron oxide: Unveiling influence of solid shape and pressure

Significant attention has been directed towards the direct reduction of iron oxide (DRI) due to its potential for reducing carbon dioxide emissions compared to the blast furnace. The DRI furnace, known as a shaft furnace, operates as a multi-scale reactor with a moving bed and counter-current flow. The mesoscale modeling of iron ore pellets involves deriving the reaction rate equation, while closure is achieved for mass, energy, and Ergun equations at the macro-modeling scale. Despite various studies, the impact of pellet shape and pressure profile on the process has not been explored extensively. In this research, the developed model, based on the unreacted shrinking core model (USCM), employs a non-isothermal, non-isobaric, steady-state, and heterogeneous approach. The investigation considers Leva's shape factor in three scenarios: 100% non-spherical, 20% nonspherical, and 10% non-spherical pellets, revealing their influence on metallization degree (MD). Additionally, pressure variations, increased or decreased by 50 kPa, are examined for the first time, revealing their effects on conversion and temperature profiles in both gas and solid phases. A 50 kPa increase in inlet pressure achieves 100% MD approximately 0.95 m before the reduction zone's end. Moreover, the effects of sponge iron production rate and H2/CO on MD are investigated.