Carbothermic Reduction of Cr₂O₃ and Fe₂O₃ under Nonisothermal Condition

Abstract

An investigation of the reduction of Cr₂O₃ and Fe₂O₃ by graphite was carried out using a nonisothermal gravimetric technique under an argon atmosphere, in a temperature range from 600 to 1973K. In the case of Cr₂O₃-C system, the reduction reaction proceeds through two stages. At first, Cr₂O₃ is reduced by graphite to form chromium carbide, and then the rest of Cr₂O₃ by the chromium carbide. The activation energies of the reaction are evaluated from 270 to 293 kJ/mol in the first stage and from 327 to 359 kJ/mol in the second stage. Excess graphite addition increases the reduction degree, and chromium carbide is obtained. Magnesia addition delayed the reduction, while hematite addition accelerates it. In the case of Fe₂O₃-C system, the reduction proceeds through three steps. In the first stage, Fe₂O₃ is reduced by graphite to form Fe₃O₄. In the second stage, Fe₃O₄ is reduced to form FeO. In the third stage, FeO is reduced to form Fe. The activation energies of the reaction are 504 kJ/mol in the first stage, 858 kJ/mol in the second stage and 243-312 kJ/mol in the third stage. Excess graphite addition increases the reduction degree.