Additive-Free Roasting Technique for Extracting Vanadium from Residue of Mica-Type Vanadium-Bearing Stone Coal

To explore the feasibility of vanadium extraction from residue of mica-type stone coal containing vanadium by additive-free roasting process,with mica-type stone coal from the northwest of China as the research object,heat energy of stone coal was obtained by circulating fluid bed combustion. The combustion residue was processed through fine grinding technology and additive-free roasting.In the roasting process,experiments were carried out to figure out the effect of the particle size of residue,roasting temperature,roasting time and air velocity on the leaching rate of vanadium. The results showed that roasting temperature had a significant influence on the increase of vanadium recovery,lower roasting temperature could not effectively destroy the lattice structure of roscoelite. And when roasting temperature was high enough to effectively destroy the lattice structure of mica,it was still difficult to extract vanadium if low valence vanadium separated from roscoelite could not be oxidized to the high valence compound containing vanadium. In the roasting process,an oxidizing atmosphere contributed to oxidize low valence vanadium to the high valence compound containing vanadium and accelerated the separation of low valence vanadium from roscoelite. It was feasible to extract vanadium from mica-type stone coal containing vanadium by fine grinding technology and additive-free roasting process,under the acid leaching conditions of 20 ℃,sulfuric acid concentration of 0. 54 mol·L- 1,no helper leaching agent and standing for 2 h,the leaching rate of vanadium could reach 83.81%.