The processes of iron oxides’ reduction have a complex physicochemical mechanism, with the participation of solid, liquid, and gaseous substances. The article discusses the existing models for the reduction of iron oxides and provides data on the thermodynamic possibility of carrying out the reactions of their reduction through the solid and gas phases. Experimental data on the reduction of iron from industrial scale, obtained by the DSC (differential scanning calorimetry) method, show the kinetic dependence of the rate and completeness of recovery on external factors: pressing pressure during sample preparation and the reagents’ composition. The pressing pressure, under conditions of iron ions’ solid-phase diffusion, has the significant effect by increasing the reagents’ contact area. Under conditions of iron ions’ comprehensive diffusion, the pressing pressure does not affect the reduction processes rate. The introduction of 10 mass.% flux into the raw mixture composition leads to a partially liquid-phase diffusion of iron ions and weakens the effect of the pressing pressure in this process. An ion diffusion-catalytic mechanism is proposed to describe the observed effects during the reduction of iron oxide of technogenic origin.

The article presents the results of a study of formation mechanism of magnesia-ferrite when heated siderites of the Bakal deposit with different iron oxide content in an inert and oxidizing atmosphere. It was established that in the case of firing in an inert atmosphere, the decomposition of siderite with high iron content begins at a lower temperature and the enthalpy of such decomposition is less. This effect can be explained by the different phase composition of the samples. The main phases formed under conditions of oxidative firing are hematite and magnesia-ferrite. The amount of hematite and magnesia-ferrite produced in the samples with different iron oxide content during firing in an oxidizing atmosphere is different. Siderite with high content of iron oxides contains more hematite in the firing products than magnesia-ferrite, and siderite with a low content of iron oxides contains more magnesia-ferrite in the firing products than hematite. Formed under conditions of oxidative firing magnesia-ferrites are solid solutions and differ in the degree of substitution of iron and magnesium ions. In siderites with high content of iron oxides, the degree of substitution of magnesium ions with iron ions is greater than in samples with a low content of iron oxides. Since the siderites of the Bakal deposit are poor ore formations, the considerable amount of magnesia-ferrite formed in them during firing makes it difficult to separate silicate and iron-oxide firing products by traditional enrichment methods. Wustite in the products of oxidative firing is not detected, because under these conditions it is in a metastable state and in the presence of a weakly oxidizing atmosphere is converted into magnetite. The scientific novelty is the explanation of the mechanism of siderite decomposition and the description of products of such decomposition. Understanding of the mechanism of decomposition of siderite from the Bakal deposit made it possible to develop the technology of reductive firing of siderite to facilitate separation of its products, and which consists in the regulation of the phase composition of silicate products of reductive firing, ensuring the collapse of magnesia-ferrite and output of iron oxide in a separate phase. The developed technology can be used to provide high-quality enrichment of siderite from the Bakal deposit.

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