Roasting Kinetics of Molybdenite Concentrates

Abstract

Roasting of MoS2 concentrate is an important step in the production of commercial molybdenum trioxide. The oxidation kinetics of two different molybdenum concentrates was investigated at temperatures from 440 to 640 °C. For both concentrates the oxidation is fairly slow and incomplete below 500 °C. The rates increase with increasing temperatures up to about 570-600 °C before becoming fairly constant. One of the concentrates showed a tendency for sintering above 620 °C while this was not observed for the other sample.To explain the rate data, a kinetic model involving the formation of MoO2 as a first step followed by the oxidation to MoO3, was proposed. The activation energy was found to the same (22 kJ/mol) for both steps and it is argued that the rate is controlled by the diffusion of oxygen through a porous product layer of oxides.