THERMODYNAMIC MODELING OF CARBON-THERMAL REDUCTION OF IRON CHROMITE
DOI:
https://doi.org/10.34185/1991-7848.2019.01.05Keywords:
iron chromite, reduction, carbides, carbon, thermodynamic modelingAbstract
Analysis of the literature data about conditions and mechanism of the reactions of solid-phase reduction of iron chromite has shown that so far there is no single understanding of both the process mechanism and its physicochemical regularities. The complexity of the thermodynamic analysis of such a process lies in its multivariance. Depending on the process conditions, the final reduction products may have different phase and chemical composition.
The purpose of this work is a thermodynamic analysis of iron chromite reduction by carbon at temperatures that preclude the appearance of liquid phases.
A thermodynamic analysis of the main reactions in the Cr-O-C and Cr-Fe-O-C systems, occurring with the formation of metal and carbide phases of different composition, was performed. The obtained data allow us to predict phase transformations during the reduction of Cr2FeO4 with carbon from a thermodynamic point of view. The temperatures of the Cr2FeO4 reduction starting were determined under the conditions for the formation of a metal product and carbides when solid carbon, iron carbide and chromium carbide are used as reducing agents. The hypothesis of the sequence of iron and chromium reduction from chromite at temperatures precluding the appearance of liquid phases was confirmed. A probable scheme for the formation of metal and carbide phases is proposed. Thermodynamic modeling of the carbon-thermal reduction of iron chromite was performed at different O/C ratios, as well as with the addition of Fe3O4 and Cr2O3 to the system. With the constant Cr/Fe ratio and temperature, it is the O/C ratio that determines the phase composition of the product. Thus, thermodynamic conditions of carbon-thermal reduction of Cr2FeO4 can be determined to obtain a low carbon ligature.
At the same time, without a comprehensive study of solid phase reduction process of Cr2FeO4, it is almost impossible to establish a sequence of phase and chemical transformations in the Cr-Fe-C-O system; therefore, it is necessary to study the kinetic features of the process and also analyze the patterns of solid phase formation.
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