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.