Thermodynamics of Sulfur in Carbon Saturated Ni-Mo Alloys

Nickel-molybdenum alloys can be produced by the carbothermic reduction of spent catalysts containing nickel and molybdenum discarded from the petroleum refinery operations for desulfurization. However, sulfur can be picked up into alloy melts from the sulfur bearing spent catalysts during the smelting process. Thermodynamics of sulfur in this alloy melt is very important for producing low sulfur Ni-Mo alloys to be used in steel industry. In the present study, thermodynamic interaction coefficients of carbon and molybdenum on sulfur in carbon saturated liquid Ni-Mo alloys were measured using the slag/metal equilibration technique at 1 773 and 1 873 K. The equilibrium sulfur distribution was measured between a slag with a known sulfide capacity and carbon saturated liquid Ni-Mo-S alloys of various compositions. The carbon solubility in liquid Ni-Mo alloy was significantly changed with molybdenum content, and the specific effects of carbon and molybdenum on sulfur was determined using Wagner's formalism as the first- and second-order interaction parameters.