Numerical simulation of flash reduction in a drop tube reactor with variable temperatures

A computational fluid dynamics (CFD) model was developed to accurately predict the flash reduction process, which is considered an efficient alternative ironmaking process. Laboratory-scale experiments were conducted in drop tube reactors to verify the accuracy of the CFD model. The reduction degree of ore particles was selected as a critical indicator of model prediction, and the simulated and experimental results were in good agreement. The influencing factors, including the particle size (20–110 μm), peak temperature (1250–1550°C), and reductive atmosphere (H₂/CO), were also investigated. The height variation lines indicated that small particles (50 μm) had a longer residence time (3.6 s) than large particles. CO provided a longer residence time (~1.29 s) than H₂ (~1.09 s). However, both the experimental and analytical results showed that the reduction degree of particles in CO was significantly lower than that in H₂ atmosphere. The optimum experimental particle size and peak temperature for the preparation of high-quality reduced iron were found to be 50 μm and 1350°C in H₂ atmosphere, and 40 μm and 1550°C in CO atmosphere, respectively.