Investigation of the Roasting Behavior of Mixtures of Molybdenum Trioxide and Molybdenum Concentrates

In this paper, a new process of roasting molybdenum concentrates with the addition of molybdenum trioxide (MoO3) was proposed. Using molybdenum disulfide (MoS2) to represent molybdenum concentrates and based on theoretical studies and experimental investigations, the roasting behavior and reaction routes were identified by thermodynamic calculations, thermogravimetric analysis, and characterization of the reaction process and reaction products. The effects of the MoO3/MoS2 ratio, reaction time, and temperature as well as the forming pressure of pellets on the solid–solid reaction of MoO3 and MoS2 were investigated, and the products were characterized using X-ray diffraction, scanning electron microscopy, and carbon–sulfur analysis. The optimum MoO3/MoS2 ratio was determined as 6.5, and the optimum reaction conditions were a temperature of 650 °C and a holding time of 60 min. The particle size of MoO2 increased gradually with the extension of the holding time, and finally, MoO2 particles with a particle size of 1.1 μm could be obtained. The sulfur content of the product MoO2 decreased significantly with the increase in the MoO3/MoS2 ratio or reaction temperature, and after this desulfuration process, the minimum sulfur content of the products was 98 ppm. Comparing powder samples with molded samples formed at 50 MPa revealed that a certain pressure promoted the reaction with an efficiency increase of about 14.6%.