Study On The Effect Of Chemical Poisoning On Activity Of DeNO_x Catalyst For Coal-fired Flue Gas

Nitride oxides?NOx?is one of the most important atmospheric pollutants and the main precursor of pollution such as smog,acid rain and photochemical smog.It has received close attention from all sectors of society.Selective catalytic reduction?SCR?has become the most widely used technology for reduction NOx emission.DeNOx catalysts are the core components of SCR technology and have a great impact on the SCR system.The commonly used commercial catalyst is V₂O₅-WO₃/TiO₂ catalysts,which is usually arranged in high temperature and high dust environment in coal-fired power plants.Its activity is easily affected by various alkali/alkaline earth metals and other components in fly ash,resulting in catalyst poisoning,which is one of the most prominent problems that inhibit the activity of catalysts.While the deactivation will directly affect the normal operation of SCR system and the safety of downstream equipment,but also greatly increase the cost of SCR system.In this paper,commercial V₂O₅-WO₃/TiO₂ catalysts were used as the research object,and the effects of alkali/alkaline earth metals K,Na,Ca,Mg and P and Fe elements on the activity of commercial V₂O₅-WO₃/TiO₂ catalysts were studied.First of all,prepare the K,Na,Ca,Mg deposited V₂O₅-WO₃/TiO₂ catalysts through an impregnation method.The influence of K,Na,Ca,Mg on the performance of the V₂O₅-WO₃/TiO₂ catalyst selective catalytic reduction of NO by NH3 was investigated.Experimental results showed that in the case of the same poisoning concentration,the higher the V₂O₅ content,the more the catalyst activity decreases,where as the less the catalyst activity decreases.The deposition of K,Na,Ca,Mg has different negative effect on the activity of the V₂O₅-WO₃/TiO₂ catalysts.we have found this regular:K>Na>Mg>Ca.The increase of amount of alkali/alkaline earth metals could aggravate the negative.The K,Na,Ca,and Mg poisoning catalyst activity decay curves were plotted and activity estimates were made.The samples were characterized by BET,XRD,NH3-TPD,H2-TPR,etc.the results indicated that the alkali/alkaline earth metals deposited could reduce the specific surface area,pore volume,acid amount and acid strength of the catalysts,and also reduce the redox ability of the catalysts,which could be considered as the main reasons for the deactivation.Secondly,The influence of phosphorus?P?,iron?Fe?on the performance of the catalystic activity was investigated.The results showed that P can cause V₂O₅-WO₃/TiO₂ catalyst poisoning and has negative effect on the activity of catalysts.The P poisoning catalyst activity decay curve was plotted and activity estimates were made.The doping of P will decrease the specific surface area,pore volume and redox ability of the catalyst,and finally has negative effect on the activity of the catalysts.Experimental results showed the deposition of Fe has no obvious effect on the activity of the catalysts.Through the study,clearing the influence laws and mechanisms of alkali/alkaline earth metals,phosphorus and iron on the activity of the catalysts.These studies can provide the theoretical support for the detection of fresh catalysts and the operation of used catalysts.It can also help catalyst manufacturers improve the SCR catalyst formulation and configuration to make it suitable for different characteristics of coal combustion.It is of great significance to formulate a reasonable catalyst regeneration and replacement life management program.