Alternative reagents for roasting Suncor oil sands fly ash

Abstract

Several roasting reagents, including Na₂CO₃, Na₂SO₄, NaNO₃ and CaO, were tested on Suncor fly ash to try to improve the vanadium extractions achieved with salt roasting. Up to 95% V was extracted using Na₂CO₃ additions of greater than 50%, while the other reagents generally gave lower vanadium extractions than roasting with NaCl or than roasting with no reagents. Leaching with 100 g/l H₂SO₄ increased the vanadium extractions, but dissolved large amounts of Al and Si into solution. Leaching with 100 g/l Na₂CO₃ gave only modest improvements in the vanadium extraction, except for samples roasted with CaO, where up to 70% of the vanadium was leached. Thus, sodium carbonate is the only reagent tested that gave both high vanadium extractions and low levels of impurities in solution; thus, it could be used as an alternative to roasting with NaCl, but higher Na₂CO₃ additions (> 35%) would required to achieve vanadium extractions of greater than 75%. Characterisation with X-ray diffraction and scanning electron microscopy was also used to study the mineralogy of the roasted ash formed using these reagents.