Experimental Verification of the Thermodynamics of Critical Aspects of the Carbothermic Reduction of Alumina. Part 1: Experimental Result of Reacting Al₂O₃-C Mixtures

The thermodynamics of several aspects of the carbothermic reduction of the alumina process were experimentally verified. The current thermodynamics are based on solution models for the Al₂O₃-Al₄C₃ system and the free energies of formation of a number of phases. In Part I of this paper, the results of reacting carbon and alumina mixtures at high temperatures 2173 K to 2323 K (1900 °C to 2050 °C) are presented. The amount of CO evolved was measured and slag samples analyzed. The initial slag or carbide formation at alumina saturation was measured to be 2220 K (1947 °C) and 1.76 pct C. The slag-making temperature and composition in the liquid region were determined and at carbide saturation were measured to be 2273 K (2000 °C) and 6.29 pct C, respectively. Considering the experimental challenges at the high temperature, with the exception of the initial slag composition, the agreement with the predicted thermodynamics is good.