Recycling of Petroleum Refinery Catalysts for Ferro-Alloy Production

Abstract

The spent catalysts discarded from the petroleum refinery operations contain a substantial amount of valued metals such as Mo, Ni and V up to 30 mass% in total together with sulfur and residual oil. Recently, the smelting reduction process of this resource using the carbothermic reaction is being developed and commercialized to recover these metals in the form of ferro-alloys. The process route starts with dry catalysts that are melted in an arc furnace at temperatures around 1500-1600° under a reducing condition. Heavy metals sink to the bottom as carbon saturated molten alloys and are separated from liquid slag containing high alumina originally present in the catalyst up to 70 mass%. It has been shown that this pyrometallurgical route has the advantage of a complete recycling scheme: metals for manufacturing special ferro-alloys, the slags for manufacturing special cements or synthetic fluxes. The process has the advantages over the hydrometallurgical route in terms of cost effectiveness and environmental issues. In the present work, an overview of newly developed recycling process for spent catalysts will be presented together with some experimental data related to this process. Ferro-vanadium and ferro-nickel-molybdenum alloys were successfully manufactured with high recovery ratios of over 92% and 95%, respectively, via the smelting reduction and the selective vanadium oxidation processes.