Abstract: Vanadium slag was treated by calcium roasting to improve the vanadium leaching rate. The effects of the operational parameters including particle size， heating rate， holding temperature， holding time and amount of additive of CaO on the roasting efficiency were investigated. The oxidation kinetics of vanadium slag was analyzed on the basis of TG-DSC curves. The results indicated that lowering heating rate is beneficial to improve the vanadium oxidation efficiency， and the vanadium leaching rate increases markedly when the holding temperature is higher than 600℃. The vanadium leaching rate reaches to 9331% under the optimum conditions of the particle size of 48~75μm， m(CaO)/m(V2O5)=042， the heating rate of 2℃·min-1， the holding time of 150 min at 850℃. The oxidation process of vanadium spinel is described by a thirdorder reaction and the apparent activation energies at the heating rates of 5 and 10℃·min-1 are 26765 and 25603kJ·mol-1， respectively.

Key words: vanadium slag, vanadium leaching rate, calcium roasting, oxidation kinetics, apparent activation energy