Changes in phase composition of soderites of the bakal deposit at heating

Abstract

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.

Transformation of siderite in the zone of hypergenesis

“…The process of change in the hypergenesis zone differs significantly from the process of artificial oxidation of siderite ores, carried out in the preparation of the charge for the blast-furnace and converter processes [8][9][10].…”

“…The common popular name "bog ore" is very unfortunate, because the genesis of these formations, as a rule, has nothing to do with swamps. Many siderite deposits are of industrial importance, in particular, the Bakal deposit (the South Urals, the Chelyabinsk region) [5][6][7][8][9][10]. But the direct use of siderite ore from this and similar deposits is impossible.…”

Diversity of Iron Oxides: Mechanisms of Formation, Physical Properties and Applications

“…A more frequently discovered combination is the co-existence of α-Fe 2 O 3 and Fe 3 O 4 crystal phases (Table 9). They can be found in natural ore samples and can be explained by abiotic [303][304][305][306][307][308] or biogenic [309][310][311] processes. Besides these natural formations, such combinations of iron oxide phases can be synthetically obtained with the use of chemical [312][313][314], physical [315] or biomimetic [316] techniques.…”