Study of the Carbothermic Reduction of the Elements of the Cr2O3-FeO-CaO-SiO2-MgO-Al2O3 System by Thermodynamic Simulation

Thermodynamic simulation in a liquid state is performed to study the possibility of reduction of the elements of the multicomponent Cr2O3-FeO-CaO-SiO2-MgO-Al2O3 system. The parameters of the initial state of the system are as follows: the temperature range (t) is 1500-1800 degrees C, the step is 100 degrees C, the total system pressure is 0.1 MPa, and the amount of nitrogen is 2.24 m(3). The aim of the work is to study the influence of the amount of gas-cleaning dust added to an ore on the reduction of the elements in making ferrochrome in the given temperature range. The oxide system composition corresponds to the chromium ore ((%) 38 Cr2O3, 11.1 FeO, 0.17 CaO, 15 SiO2, 29.7 MgO, 6 Al2O3) and the gas-cleaning dust (15.5 Cr2O3, 7.5 FeO, 0.8 CaO, 67.3 SiO2, 7.2 MgO, 1.7 Al2O3) that are used to produce medium-carbon ferrochrome. The dust content in a mixture was 0, 5, 10, and 20%. Carbon was used as a reducing agent. The consumption of the reducing agent is increased by 10% of the stoichiometry for the reduction of Fe and Cr and by 8% of the metal mass for the formation of iron, chromium, and silicon carbides. The simulation is carried out using HSC Chemistry 6.12 (Outokumpu, Finland) software package. The thermodynamic data of the CrO(II) compound are introduced into the database, and the thermochemical characteristics of the compounds CaCr2O4, SiC, Cr3C2, Cr7C3, Cr23C6, and Fe3C, which exist in the database, are refined. It was determined that increase in the melt temperature from 1500 to 1700 degrees C is found to increase the degree of chromium reduction (eta(Cr)) from 90.2 to 94.8% at various dust contents in the system. An increase in the dust content in a mixture from 0 to 20% decreases eta(Cr). The maximum value of eta(Cr) is characteristic of a dust-free system: it is 94.8% at (CaO + MgO)/(SiO2) = 2.0 and t = 1700 degrees C. The chemical compositions of the metal and slag melts are determined. The amount of [Cr] = 64-65.6% at a melt temperature of 1700 degrees C. The simulation results can be used to analyze the reduction processes occurring in chromium-containing systems and alloy production technologies.