Effect of V₂O₅ During Oxidation Roasting of Pellet: Non-isothermal Kinetic Analysis and Microstructure Evolution

The influence of V₂O₅ of iron ore during oxidation process was examined by thermogravimetric analysis using a non-isothermal thermogravimetric analysis technology. The oxidation process could be divided into two stages. The kinetic mechanism and apparent activation energy (E) were studied using the Coats–Redfern (C–R) method. The obtained results showed that diffusion model was the best mechanism describing effectively oxidation process of iron ore under different V₂O₅. The values of E showed a decreasing trend with the increase of V₂O₅ addition in the whole oxidation process, indicating that the V₂O₅ was conducive to improve the oxidation kinetic conditions. And the fluctuation amplitude of E at stage II (10.489 kJ/mol) was greater than that at stage I (4.019 kJ/mol). With the amount of V₂O₅ increasing, microstructure study of pellets indicated that the growth pattern of grains was disrupted, resulting in abnormal grain growth and an increase in porosity. Thus, the loose structure of pellets could facilitate the internal diffusion of reaction gas at this moment. The oxidation kinetic conditions were improved and the values of E decreased ultimately.

Oxidation kinetic analysis of the iron ore with different V₂O₅ additions.