Study Of Microwave Activated Roasting Of Molybdenite

The low sulfur content molybdenum trioxide got in this study was by a new technology that is the microwave activation roasting process of molybdenite.Process conditions of non-activated and activated roasting molybdenite were studied,and the specific surface area,the oxidation properties,lattice constant,microstructure and morphology of molybdenite were analysed and characterized by the laser particle size analyzer,thermogravimetric(TG),X-ray diffraction(XRD),scanning electron microscope(SEM).Meanwhile,based on the gas-solid multiphase unreacted core model,the weightloss curve and differential thermal curve,the oxidation roasting kinetics and thermodynamics of molybdenite were studied,and the effect of temperature and heating rate on oxidation roasting were also studied systematacially.Conclusions are as follows.(1)The optimum condition of traditional roasting is:16g raw material roasted at650? for 120 minutes.(2)Microwave activation promotes deep oxidation process of the later oxidizing roasting period and reduces the reaction temperature,that make the molybdenite fully oxidised to release more heat.Increasing the output power of microwave,extening the microwave radiation time and reducing the material weight is beneficial to reduce the amount of residual sulphur in molybdenum calcine eventually.(3)Microwave activation has a certain impact on performance and structure on molybdenite.Microwave activation can effectively reduce the residual sulfur content of molybdenum calcine in molybdenite oxidation roasting,e.g.the residual sulphur content was reduced from 0.391% to 0.098%.microwave activation can effectively reduce the residual amount of sulfur of molybdenum calcine and average particle size of molybdenite,while increasing the specific surface area of molybdenite..As the extensionof microwave activation time,crystal cell volume and grain size of MoS2 were reduced,the micro strain was increased slightly.At the same time,the surface topography of molybdenite becomes more loose,but layered structure do not change.In addition,the oxidation property was changed significantly,with the extension of activation time,molybdenite conversion rate become bigger after 547?,and the rate of weightlessness is increased from 5.59% to 6.92% at 600?.(4)Thermodynamics analysis showed that oxidation roasting of molybdenite is irreversible strong exothermic reaction,the higher the temperature,the faster the oxidation rate of molybdenite.At 350~500?,the conversion rate of molybdenite is low,and the apparent activation energy calculated by the Arrhenius equation is 80.14 kJ/mol while the reaction is controlled by internal diffusion.At 540~630?,the conversion rate of molybdenite become significantly higher,and the apparent activation energy is 90.42kJ/mol while the reaction is controlled by chemical reaction.Heating rate has influence on oxidation roasting process of molybdenite significantly,the lower heating rate,the higher conversion rate of molybdenite is,and the more quantity of heat emitted by oxidation.