Isothermal oxidation kinetics of ilmenite concentrate powder from Panzhihua in air

- The kinetics of the oxidation of ilmenite concentrate powders was studied comprehensively.
- Different mechanisms transformation in a very wide range of oxidization temperature is proposed.
- The reaction mechanism and apparent activation energies were studied by different methods.
- A novel process of extraction of high titanium mineals (slag) from ilmenite concentrate is proposed.

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 K (700 °C), the reaction mechanism is the three-dimensional diffusion, and the model function was Gα=1−23α−1−α2/3 (α, reaction degree). When the temperature was above 1273 K (1000 °C), the reaction mechanism is random nucleation and subsequent growth, and the model function was G(α) = [− ln(1 − α)]1/3. No single model function can fit well the oxidation process at 1023 K (750 °C), 1073 K (800 °C), 1123 K (850 °C), and 1173 K (900 °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 K (600 °C), 923 K (650 °C), and 973 K (700 °C); 4.11 and 3.96 kJ/mol at 1273 K (1000 °C), 1373 K (1100 °C), and 1473 K (1200 °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.

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