Research On Calcification-roasting Mechanism Of Vanadium Slag

Recently, because of the environmental pollution of the waste and exhaust gases by sodium roasting technique becomes more and more serious, calcification roasting vanadium technology has gradually been used in the actual production. calcification roasting vanadium technology has reduced environmental pollution. However vanadium slag composition is very complex, sometimes the effect of extraction of vanadium is instability, Therefore, the research on calcification-roasting mechanism of vanadium slag is necessary.This article takes the vanadium slag of Panzhihua Iron and Steel Plant as raw material, and calcification roasting-acid leaching process. Analysis of the morphology of vanadium slag before roasting, and the effect of roasting temperature, calcium vanadium ratio on the morphology of vanadium slag after leaching and after roasting by the use of XRD analysis, SEM analysis, microscope. The conclusions were obtained as follows:(1) The vanadium slag is consisting of vanadium iron spinel which is light gray and irregular lumps, fayalite which is massive, pyroxene which is dark gray.(2) Vanadium iron spinel mainly contains of iron, vanadium, titanium, manganese, chromium, magnesium and some other elements, fayalite mainly contains of silicon, iron, manganese, magnesium, pyroxene mainly contains of calcium, aluminum, magnesium, iron, oxygen are all distributed in these three regions, the content of iron and titanium at the edge of vanadium iron spinel is higher than the content of iron and titanium at the center, but the content of vanadium is just in the opposite, the content at the center is higher than the content the edge.(3) The phase changes of the slag by calcification roasting include:the oxidation and decomposition of the Vanadium iron spinel,the oxidation and decomposition of fayalite, vanadium-containing phases and CaO reaction generates calcium vanadium and the oxidation and decomposition of pyroxene, in the range of700～900℃,calcium vanadium can be produced by the reaction of CaO and vanadium-containing phase.(4) The content of iron, titanium and manganese is relatively high in the vanadium-rich region, when the content of CaO is low in the vanadium slag. The iron vanadium, manganese vanadium in the vanadium slag would transform into calcium vanadium when the content of CaO improve. Excessive amount of CaO and silicate will react into insoluble calcium when the content of CaO is overdose.(5) To improve the roasting temperature is conducive to the formation of calcium vanadium, However, Pyroxene would react wrapped in calcium vanadium surface when the temperature reaches940℃,it would be effect of the phases which contains vanadium to be oxide.(6) To improve the content of CaO can be increased to the vanadium leaching rate, however, excessive amount of CaO and silicate will react into high melting point and insoluble Ca2SiO4when calcium vanadium ratio reached0.8,it would impact on the leaching effect.(7) To improve the roasting temperature can be increased to the vanadium leaching rate, but the too much high temperature will affect leaching effect of vanadium, because of the reaction of silicate, vanadium is difficult to be leached when temperature reached940℃.(8) To improve the roasting time can be increased to vanadium leaching rate, Leaching effect of vanadium was perfect when the roasting time reached4h, but secondary reaction among the roasted products would happened when the roasting time was too long.