Study On NH₃-SCR Denitration Characteristics Of Rare Earth Tailings Modified By ?-Al₂O₃

With the development of production,NOx has caused serious environmental problems in my country.Among them,acid rain and photochemical smog are the main ones.The emission of nitrogen oxides has become an increasingly serious problem.Today's main denitration technologies are selective catalytic reduction technology?SCR?and selective non-catalytic reduction method?SNCR?.Among them,NH₃-SCR technology using NH₃ as a reducing agent has the advantages of simple structure,no secondary pollution,no by-products,and high denitration rate.Therefore,NH₃-SCR technology has become the mainstream denitration technology for industrial applications.Baiyun Ebo rare earth tailings are rich in a variety of metal oxides with good catalytic activity?Fe,Mn and Re?required by the catalyst.This condition makes it possible for rare earth tailings to be used as natural catalysts.The denitration activity test platform of furnace and Fourier infrared flue gas analyzer.Investigate different addition ratios of pseudo-boehmite?15%,35%,50%,65%,80%?,mixing with different ball milling times?1h,2h,3h,4h?to prepare different catalyst particle sizes?10 mesh,20 mesh,40 mesh?,changing different airspeeds(50000h^-1,20000h^-1,10000h^-1,8000h^-1,5000h^-1),different oxygen content?3%,4%,5%?For the effect of denitration activity,the denitration activity experiments were conducted at different temperatures?100?,150?,200?,250?,300?,350?,400??.Then through XRD,SEM,H₂-TPR,NH₃-TPD,XPS,BET and other characterization methods to explore the relationship between rare earth tailings denitrification performance and its structure and denitrification mechanism research.The main conclusions are as follows:The research on the catalyst denitration performance found that:1000-mesh?-Al₂O₃modified 200-mesh rare-earth tailings by ball milling.The best working condition is the best addition amount of?-Al₂O₃ is 50%,and the best ball-milling of?-Al₂O₃ and rare-earth tailings At a time of 2h,the optimal catalyst particle size is 20 mesh,and the operating parameters also have a certain effect on the denitrification performance.The optimal space velocity is 8000h^-1and the optimal oxygen content is 4vol%.SEM results show that?-Al₂O₃ is highly dispersed on the sample surface.When the amount of?-Al₂O₃ is too large?65%,80%?,?-Al₂O₃ has poor agglomeration and dispersion on the surface of the mineral,and the agglomeration phenomenon is not conducive to the denitrification.The method of ball milling makes the dispersion of active material and acid sites better,which is conducive to the improvement of denitration activity.The specific surface area indicates that the addition of?-Al₂O₃ increases the specific surface area of the catalyst,increases the pore structure,increases the contact time between the reactants and the catalyst,reduces the internal and external diffusion resistance of the gas,and thus improves the catalytic activity.NH₃-TPD showed that the addition of?-Al₂O₃ increased the acid sites on the catalyst surface and the amount of adsorption increased.H₂-TPR and XPS indicate that the addition of?-Al₂O₃ through ball milling improves the catalyst's ability to adsorb oxygen and promotes denitrification activity.Ball milling also makes the catalyst surface active substances?Fe,Ce?more dispersed and the catalyst's reducing ability is enhanced In the catalyst,Fe³⁺is reduced to Fe²⁺and Ce⁴⁺is reduced to Ce³⁺.Electron transfer between Fe³⁺/Fe²⁺and Ce⁴⁺/Ce³⁺is beneficial to the catalytic reaction.