Abstract: The kinetic behavior of reduction for iron (III) oxides was studied by means of TG-DTA thermal analyzer under temperature programed and isothermal conditions with Hydrogen as the reducing gas. The main results show that:
(I) using single kinetic model to fit the overall reductive reactions is impossible. The reduction by hydrogen proceeds in several steps:
Fe_2O3 ~A→Fe_3O_4 ~B→FeO ~C→Fe
It can be treated with different kinetic equations for different periods.
(II) During the first period (including the step A and step B), the main process is nucleation, growth and transformation of Fe_3O_4; the Erofeev equation is better than the Contracting Sphere Model. During the second period (Step C), the main process is reduction of FeO, the Cubic Net Model may be satisfied.
(III) The Fe_3O_4 and FeO are formed as intermediates. The transformation of Fe_3O_4 is the controlling step. FeO may react and vanish rapidly at higher temperature.
(IV) The kinetic parameters in different periods were obtained. The machanism of the reaction was proposed and explained in some detail.