Refractory metals recovery from industrial wastes

Refractory metals like Mo and V are alloyed in the special steels like heat-resisting, tool, ship and pipe steels for the improvement of their physical and mechanical properties. Most of refractory metals are refined as by-products in the other metals production processes. Recently, it becomes difficult to open new mines up for the environmental pollution issues, and as the results, it pays attention to recover them from industrial wastes as Mo and V resources instead of new mines development, because these wastes contain higher MoS₂ in spent lubricant, MoO₃ in oil refining catalysis and V₂O₅ in an domestic heavy oil combustion ash than the natural minerals containing them. In the present work, it was tried that these refractory metals was recovered as Fe-alloys because more than 80% of refractory metals are used as steel alloying elements and the energy consumption for reduction and production to Fe-alloys are less than that of pure refractory metals production. At first, the recover principal of Fe-Mo alloy from spent lubricant, in which Mo existed as MoS₂, was experimentally established via their oxidizing roast and reduction processes at 1773K based on the knowledge of Cu process metallurgy. The spent lubricant mixed with CaCO₃, Fe₃O₄ and C was reduced in a Cgr. crucible at 1773K. The mixed sample melted completely and separated into slag and metal phases. In the second step, the recovery of Fe-V alloy from V₂O₅ in the combustion ash of Orinoco tar was tried. The ash mixed with CaO and C was reduced in a Cgr. crucible at 1773K. The mixed sample melted completely and separated into slag and metal containing vanadium carbide. V was not almost observed in slag phase, and it meant that most of V in ash was recovered as vanadium carbides into the metal phase. The metal was Fe-Ni alloy. In the present work, Fe-Ni-V-C quo-ternary isothermal section phase diagram was experimentally assembled at 1773K. As the result, 53.3mass%Fe-42.2mass%Mo-4.3mass%C alloy from spent lubricant and 37.4mass%Fe-46.4mass%Ni-12.3mass%Si-2.1mass%C alloy - VxCy mixture from Orinoco tar combustion ash by the reduction with carbonaceous materials were successfully recovered in the present work.