Short-flow preparation of pure MoO3 from CaCO3-added molybdenite concentrate pellet by sublimation with flue gas recirculation

Abstract

Abstract Existing methods for processing molybdenite (MoS2) concentrates into pure materials suffer from waste pollution and complex procedures. In this work, a new flowsheet for pure MoO3 production from MoS2 concentrates has been established based on the combination of calcified roasting, sublimation, and flue gas recirculation (FGR). Fundamentals of MoO3 separation from CaCO3-added MoS2 concentrate pellet with the atmosphere containing O2 and high-proportion SO2 are investigated. The reaction feasibilities and rates of MoS2 oxidation, CaMoO4 transformation and MoO3 sublimation are fully discussed, along with the influence mechanism of CaCO3. The results indicate that SO3 formation plays an important role in CaMoO4 transformation, and the addition of CaCO3 can result in faster MoO3 separation due to the increase of melting point of oxidized pellet and the formation of highly porous structure. With the guidance of fundamentals, detailed experiments are performed to obtain suitable conditions for improving the recovery efficiency of Mo. As a result, over 94% of Mo is separated as pure MoO3 when MoS2 concentrate pellets are added with 60% CaCO3 and roasted at 775 °C for 2 h in the atmosphere containing 25% SO2. Finally, an overall flowsheet for pure MoO3 production from MoS2 concentrate is presented and evaluated. Compared with existing processes, the new flowsheet can achieve higher production efficiency and less pollution.