Isothermal oxidation kinetics of ilmenite concentrate powder from Panzhihua in air

The objective of this study was to establish the kinetics of oxidation of ilmenite concentrate powders, which promotes reduction via the oxidation process. In this paper, the kinetics of the oxidation of ilmenite concentrate powders from low temperature to high temperature was studied comprehensively using the thermal gravity method. The reaction mechanism and model function were studied using two different classical methods, and then the results were compared. The results showed that, when the oxidation temperature was below 973 IC (700 degrees C), the reaction mechanism is the three-dimensional diffusion, and the model function was G(alpha) = (1-2/3 alpha) (1-alpha)(2/3) (alpha, reaction degree). When the temperature was above 1273 K (1000 degrees C), the reaction mechanism is random nucleation and subsequent growth, and the model function was G(alpha) = [-In(1-alpha)](1/3). No single model function can fit well the oxidation process at 1023 K (750 degrees C), 1073 C (800 degrees C), 1123 K (850 degrees C), and 1173 K (900 degrees C); thus, a multistage mechanism was proposed to explain the reaction process; this mechanism includes three-dimensional diffusion, random nucleation and subsequent growth in the order of increasing reaction degree. The apparent activation energies for the oxidation were also studied using two different methods: 199.43 and 194.01 kJ/mol at 873 degrees C (600 degrees C), 923 K (650 degrees C), and 973 I<(700 degrees C); 4.11 and 3.96 kJ/mol at 1273 degrees C (1000 degrees C), 1373 K (1100 degrees C), and 1473 K (1200 degrees C). The relationship of oxidation degree with time and temperature is also discussed, which is helpful for the selection of the parameters of the oxidation process. (C) 2017 Elsevier B.V. All rights reserved.