Peter the Great St. Petersburg Polytechnic University (St. Petersburg, Russia):

A. I. Demidov, Dr. Chem., Prof., the Higher School of Physics and Materials Technology, e-mail: demidov1902@gmail.com
I. A. Markelov, Graduate Student, the Higher School of Physics and Materials Technology

The results of calculation of the standard Gibbs free energy of the reactions of iron oxides reduction by hydrogen at different oxide to reductant ratios in the temperature range of 900-1600 K are presented in this paper. The calculation is based on the principle of independence of the reactions in the system. It is shown that if iron (III) oxide is taken, then at 1:3 oxide to hydrogen ratio the equilibrium position in the indicated temperature range is shifted to the right, and the reaction product is iron. The production of iron from iron (II, III) oxide is possible at 1:4 oxide to hydrogen ratio and temperatures above 1200 K. Iron can be obtained from oxygen-rich wüstite at temperatures higher than 1400 K. The standard Gibbs free energy change calculations of oxygen-poor wüstite with hydrogen reaction show that the equilibrium position is shifted to the left, to the reactant side. A shift of the equilibrium position to the right can be achieved at high hydrogen to water ratio in the gas phase. Iron can interact with iron oxides Fe₂O₃, Fe₃O₄, FeO_(1+x"), as a result, the reaction products are Fe₃O₄, FeO_(1+x"), FeO_(1+x'). Thermodynamic calculations indicate that iron oxides FeO_(1+x") and FeO_(1+x'), in turn, can interact with Fe₂O₃ to form Fe₃O₄, and Fe₃O₄ can interact with FeO_(1+x') to form FeO_(1+x"). Thus, the overall process of the reduction of iron from oxides by hydrogen is proposed to be considered as a sequential reduction of iron from oxides containing iron of different oxidation states, from Fe (III) to Fe (II).

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