Thermodynamic Simulation of the Carbothermic Reduction of Chromium from the Cr2O3–FeO–CaO–SiO2–MgO–Al2O3 Oxide System

Abstract: The carbothermic reduction of chromium from the Cr2O3–FeO–CaO–SiO2–MgO–Al2O3 oxide system is subjected to thermodynamic simulation in the temperature range 1673–1973 K at a step of 50 K, a total pressure of 0.1 MPa, and an amount of nitrogen of 2.24 m3. The oxide system is represented by the chromium ore (wt %) 38 Cr2O3, 11.1 FeO, 0.17 CaO, 15 SiO2, 29.7 MgO, 6 Al2O3, and low-carbon ferrochromium slag. It contains (wt %) 13 Cr2O3, 4 FeO, 41.6 CaO, 21.2 SiO2, 12.8 MgO, and 7.4 Al2O3 and is added to the ore in an amount of 0, 5, 10, and 20%. Carbon is used as a reducing agent, and its consumption is increased by 10% from 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 thermodynamic simulation is carried out using the 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 existing in the database, namely, CaCr2O4, SiC, Cr3C2, Cr7C3, Cr23C6, Fe3C, and Al4C3, are refined. The results of thermodynamic simulation demonstrate that an increase in the process temperature from 1673 to 1973 K increases the reduction of chromium (ηCr) at various slag contents in the system. An increase in the slag content in the system from 0 to 20% decreases ηCr from 94.8 to 94% at 1973 K. The reduction of chromium is maximal for the system composition with 0% slag. The chemical composition of the metal at a 1973 K and 0% slag is (wt %): 65.6 Cr, 22.7 Fe, 0.26 Si, and 11.5 C. The thermodynamic simulation results can be used to develop a technology for producing a chromium-containing alloy when a low-carbon ferrochromium slag is involved in metallurgical processing. © 2021, Pleiades Publishing, Ltd.