Study On Denitrification Of Rare Earth Concentrate And Its Denitrification Performance Of NH₃-SCR

Air pollution caused by the massive use of fossil fuels is increasing.Among them,nitrogen oxides?NO_X?is one of the main atmospheric pollutants.Selective catalytic reduction?SCR?is the mainstream technology of NOx emission control,and catalyst is the core and key of this technology.At present,vanadium-titanium-based SCR catalysts for industrial applications have many shortcomings.Therefore,the development of new catalytic materials has become a research hotspot in this field.The catalyst with rare earth oxide as the main active component has high preparation cost,complicated process and is difficult to be widely applied.This thesis directly uses the rare earth concentrate to prepare the NH₃-SCR catalyst.it is not necessary to extract the purified material from the natural minerals and prepare the catalyst,thereby avoiding the complicated extraction and re-preparation process.In this thesis,the rare earth concentrate is decontaminated by acid leaching and alkali roasting.The surface of the rare earth is modified while increasing the percentage of the rare earth element and the transition metal.In order to achieve the purpose of utilizing the synergistic action of various metals in natural minerals to achieve the removal of nitrogen oxides.In this thesis,the rare earth concentrate was modified by acetic acid leaching,hydrofluoric acid leaching,alkali addition roasting,etc.,aiming to expose elements such as strontium,iron and strontium in the rare earth concentrate to the surface of rare earth concentrate.XRF,XRD,SEM,BET observation of mineral phase structure and changes in surface of rare earth concentrates on the surface of concentrates and concentrates;testing of catalysts prepared from rare earth concentrates by using NH₃-TPD,NO-TPD and activity tests The performance was verified;the active elements exposed to the surface of the concentrate were verified by XPS.The results show:?1?After treatment,the active components of the rare earth concentrate are exposed on the surface of the active powder,and the crystallinity of the active component of Ce₇O₁₂ is reduced on the surface of the active powder,and the catalytic reduction effects of various metal oxides such as barium,iron and strontium are obvious;?2?Forming a rough surface inclusion on the surface of the active powder after molding,so that the specific surface area thereof is increased,and the specific surface area of the active powder after the alkali acid roasting treatment is increased,the surface void is small,which is favorable for gas adsorption and Catalytic reaction;acid,alkali,acid-base co-treatment has important effects on the redox properties of the catalyst,NH₃ and NO adsorption characteristics,and the comprehensive performance of the active powder prepared by the alkali acid co-treatment is relatively good;?3?The surface active component of the active powder is mainly Ce,and coexists in the form of Ce?III?and Ce?IV?;secondly,Fe exists in two valence states of Fe?III?and Fe?II?.The composition of Fe?III?is more;after the combined treatment of acetic acid,hydrofluoric acid and alkali roasting,the catalytic activity of rare earth concentrates shows synergistic effect;?4?The active powder prepared by the acid-base treated rare earth concentrate has a reaction temperature of 400?,and the NO content is 600 ppm,NH₃:NO=1:1.5,and the O₂concentration is 3%.Up to 87.4%.