Study On Preparation Of Micron Scale CeO₂ By Spray Pyrolysis

Rare earths are widely used for their excellent properties in magnetic,electrical,optical and catalytic activities.The traditional preparation technology for separating rare earth oxides has problems such as poor dispersion performance,generation of effluent and easy agglomeration phenomenon.Spray pyrolysis technology is an effective way to realize the short process of rare earth separation due to the short technical process,simple process and environmental friendly,and has become a hot spot for the research of new process for the preparation of functional materials.In this paper,the industrial production line product CeCl₃·7H₂O was used as the experimental raw material to prepare cerium oxide by spray pyrolysis technology.Using the spray pyrolysis furnace built by the group,the effect of temperature on the pyrolysis process,phase composition and particle size was investigated under the pyrolysis conditions of 550℃,650℃,750℃and 850℃,respectively,using the temperature of the pyrolysis furnace as a variable.The physical model of the spray pyrolysis furnace was constructed by applying simulation software using numerical simulation calculations.The k-εturbulence model,discrete phase model and chemical reaction model were applied to computational fluid dynamics to realize the three-dimensional numerical simulation calculation of the spray pyrolysis furnace.（1）Combined with the laboratory spray pyrolysis reaction device,using spray pyrolysis technology to prepare rare earth oxides from rare earth chlorides,focusing on the process parameters of direct pyrolysis of CeCl₃·7H₂O solution to generate Ce O₂,investigating the effect of pyrolysis temperature on the particle size of the product,and analyzing and characterizing the resulting product by XRD,SEM and other detection methods,at the heating zone temperature of 650°C,the At the heating zone temperature of650°C and carrier gas pressure of 0.25 MPa,ultra-fine cerium oxide particles with an average particle size of about 21.3μm were obtained,while at the temperature of 550°C,there existed CeCl₃that did not have time to react,and the particle size obtained at this time was larger,with an average particle size of 77.1μm.（2）Analysis of cerium oxide powder obtained by spray pyrolysis can be obtained:the purity of cerium oxide obtained by spray pyrolysis is high,and the product contains only a very small amount of carbon and the higher the temperature,the less carbon.（3）Further analysis of the change of temperature and water vapor content in the pyrolysis furnace,it is found that at the same pyrolysis temperature,the distribution of water vapor content and temperature show the same trend of change.（4）Finally,the influence of pyrolysis furnace temperature on the velocity is analyzed.The higher the temperature in the furnace wall heating area,the smaller the maximum velocity is.The maximun velocity reaches about 1m/s near 1/4 of the central axis.The change of the overall average velocity decreases with the increase of the temperture of hot air,which is mainly due to the influence of air viscosity.The higher the temperature is,the more viscous the air is,and the more it hinders the droplets and the lower the velocity.Finally,the content distribution of HCl was analyzed.HCl gas was generated at the bottom of the pyrolysis furnace,indicating that rapid reaction occurred when heated,and the content of HCl near the wall of the furnace increased about 0.04%compared with that at the central axis.