A numerical study on process intensification of hydrogen reduction of iron oxide pellets in a shaft furnace

In this paper, techno-economically feasible technologies for improving the performance of a shaft furnace for hydrogen reduction of iron oxide pellets are explored using a simplified algebraic model in combination with a computational fluid dynamics -based shaft furnace model. The former determines the theoretical maximum gas utilization degree that corresponds to the thermodynamic limit regarding iron ore reduction by hydrogen. The latter clarifies, from a kinetic viewpoint, how the performance indicators respond to variations in the main operating parameters, including iron ore reducibility, top gas pressure and reduction zone length. The results show that an increase in the heat utilization ratio leads to a higher theoretical maximum gas utilization degree and thus, increasing the heat utilization ratio by means for process intensification can give rise to a higher gas utilization degree. An increase in each of those three operating parameters yields a higher heat utilization ratio, but extending the reduction zone lowers furnace productivity. Therefore, enhancing pellet reducibility and increasing the operating pressure are considered effective means for process intensification of the shaft furnace, for which optimal operating parameters are finally determined. The findings of this work may serve as guidelines for the design of more efficient hydrogen shaft furnace operations.