基于构型差异的SCR脱硝催化剂碱金属中毒失活机制研究OA

[Objective]With the popularization of co-combustion of high-alkali coal in Xinjiang,systematic studies on the difference and mechanism of alkali metal poisoning resistance between honeycomb and plate SCR catalysts remain insufficient.Most existing researches are based on the simulation of single alkali metal salts in the laboratory,whereas actual fly ash constitutes a complex mixture.The significant discrepancy between simulated conditions and real flue gas from high-alkali coal combustion results in limited engineering guidance value of relevant research findings.[Methods]In this work,actual fly ash from power plants was adopted,and typical flue gas conditions were simulated in a laboratory fixed-bed reactor.The physical and chemical property changes of fresh and aged honeycomb and plate SCR catalysts were compared.Combined with specific surface area measurement,NH3-TPD analysis of surface acidity,XPS characterization of vanadium valence states and other techniques,the deactivation behaviors of the two catalysts upon alkali metal poisoning were systematically investigated.[Results]Although plate catalysts are more susceptible to sintering deactivation under extreme high-alkali conditions,and bulk diffusion deactivation is difficult to recover via physical or mild chemical regeneration,their denitrification efficiency decays more slowly than that of honeycomb catalysts.At the same alkali loading,the denitrification activity of honeycomb catalysts decreased by 29.5%within 4 800 hours,while that of plate catalysts only dropped by 24.6%.The vanadium valence cycle of honeycomb catalysts is more easily interrupted by alkali metals,which suppresses the"fast SCR pathway"relying on NO→NO2 conversion.Moreover,their Brønsted acid sites are more prone to neutralization by alkali metals.[Conclusion]Therefore,plate catalysts are the preferred choice for long-term denitrification in industrial scenarios involving co-combustion of high-alkali coal.