The reduction kinetics of a pure and a Ca-added hematite, as well as of two iron oxide-containing metallurgical wastes, were studied by means of isothermal TG measurements, using H2 or CO as reducing agents. Below 900 K, the wastes were far less reactive than the pure or Ca-added hematite. This phenomenon was attributed to retardation of the hematite-magnetite transformation by surface Na and Si. Above 1000 K, however, the reaction rates for the wastes and for the Caadded hematite were higher than that of the pure hematite. The higher reactivities were attributed to the effects of the Ca on the microstructure of the product layer. The models of nucleation and growth processes were applied to describe the isothermal TG curves at low temperatures and in the vicinity of the rate minimum, while the model for gas-film diffusion control could be used in the case of high reaction rates.
ASJC Scopus subject areas
- Chemical Engineering(all)