Experimental Study On Vanadium Extraction From Vanadium Slag With Low Calcination

The experimental employed an industry slag which had been produced by duplex process in a factory of Pan Zhihua (contained with9.28%V and1.85%Ca) as the sample. Compared with the previous research material, the vanadium slag in this study contains higher V and higher Ca content. The composing of the slag mainly include Fe and Si, Ti, Ca, V, Mn and a small amount of P, Al, Na, Cr.etc. The mineralogical composition of this vanadium slag is mainly composed of spinel phases, olivine phases and pyroxene phases. The crystals microstructure of the slag which has a smooth and close texture can be seen from the photographs of scanning electron microscope (SEM).Thermodynamic calculation shows that the oxidation and decomposition of the main phase in vanadium slag will be spontaneous happened in the roasting process (low calcium). The exploring experiment proves that the sodium carbonate solution can benefit V2O5and CaV2O6leaching rate. Indeed, the addition of calcium oxide which is much valued in water leaching and acid leaching can be ignored in this process.Thus, a novel V-extraction process, namely the roasting (low calcium)-alkali leaching (Na2CO3) process had been investigated in this thesis. The vanadium slag had been researched, vanadium-iron spinel was found to be the main phase of vanadium. The feasibility had been proved based on the study of thermodynamics calculation and experimental. Through the experimental on the effect of parameters,82.6%leaching rate of vanadium had been obtained (roasting temperature at850℃, roasting time at120min,160g/L Na2CO3solution, stirring rate400r/min, leaching temperature at90℃, leaching time at150min and L:S=20:1). When employed pressure leaching method in the leaching process to enhance the utilization factor of Na2O3,88.8%leaching rate of vanadium had been obtained (leaching temperature at180℃,L:S=10:1).The analysis of kinetics shows that the process of sodium carbonate solution leaching is according with the description of shrinking core model. The effect of the stirring speed on the flow field of leaching solution and leaching rate had been the investigated by PIV Flow detection. Meanwhile,"the maximum effective stirring speed" was explained by "Cavitation effect".