Fluidization behavior and reducibility of iron ore fines during hydrogen-induced fluidized bed reduction

A laboratory fluidized bed reactor was used to investigate the fluidization behavior and reducibility of various iron ore fines. Hydrogen was chosen as a reducing agent across a temperature range of 873–1073 K. The magnetite ore used exhibited strong sticking behavior after the initiation of metallic iron formation. All other tested ores fluidized sufficiently well when subjected to the same high reduction temperatures. Parallel kinetic analysis was conducted using a previously developed model to include three rate-limiting step types. The trend of apparent activation energy was correlated with the degree of reduction. Additionally, the influence of varying the specific gas rate was investigated. The results show the variation in reducibility as a result of different interactions, which influence the rate-limiting mechanisms of nucleation and the undertaken chemical reactions, which vary as a function of temperature and degree of conversion. The apparent activation energies, determined from the reduction of wustite to metallic iron, were in the range of 15–60 kJ/mol, depending on the iron ore used and the degree of conversion. The change in apparent activation energy deriving from the increased specific gas rate can be explained by an increasing nucleation effect, especially at lower reduction temperatures.