2015 Volume 55 Issue 9 Pages 1797-1805
In order to take the advantage of the large reaction surface of fine iron ore concentrates and expect a high reaction rate without sticking or agglomeration problems, a suspension gas-solid reaction system was designed to explore the feasibility of fast direct reduction of fine iron ore. In this study, upward gas flow was used to prolong the particles’ falling time. Pure silica particles were chosen as the dispersion agent. The Stokes gas-particle model with the relaxation time concept was applied to accurately model the falling process. Highly metallized porous iron particles over 90% of Rd (reduction degree) were obtained at 1273 K with 20.1 s of hydrogen reduction. The morphology evolution characteristics of the fine particles during reduction were investigated via SEM, and a conceptual diagram was formulated in this paper in order to well understand the relationship between the reduction condition and the structural evolution. The shrinking core model was introduced to analyzing the reduction kinetics in this experiment system, which indicates that the microstructure evolution of the particle during reduction can be influenced by temperature and the resistance of internal mass transfer cannot be ignored under this experiment condition especially in the later stage of reduction.