Phase transformation and roasting kinetics of vanadium slag in air atmosphere

Abstract

The essential supply of vanadium for production, vanadium slag, is generally extracted by way of roasting-leaching process. In roasting, it was located that the leaching charge of vanadium improved and the break of spinel is more obvious with the rise of roasting temperature. The phase transformation of vanadium slag happened in the roasting process, but it is unclear that the “kinetic triplet factors” of the activation of vanadium slag after roasting. Therefore, the apparent activation energy (E) and the pre-exponential factor (A) of olivine and spinel oxidation were obtained by FWO method and KAS method. The E value were 140.97 kJ/mol (olivine) and 214.68 kJ/mol (spinel). The pre-exponential factors were 446491.41 min−1 (olivine) and 420236191.33 min−1 (spinel). The chemical reaction control and 3-D diffusion Zhuraalev-Lesokin-Tempelman mechanism model were determined by Malek method. The results show that the activation energy of vanadium oxidation process can be increased by increasing the roasting temperature at 1100 K-1250 K, which makes the conversion of spinel phase difficult. From the perspective of kinetics, it is important to select a reasonable roasting temperature to improve the activation roasting efficiency of vanadium slag. This study provides some theoretical guidance for strengthening the roasting process and efficient extraction of V element of vanadium slag.