Research On Regeneration Of Waste Flue Gas Denitrification SCR Catalyst In Thermal Power Plants

During the combustion of coal,a large amount of nitrogen oxides?NO_x?is released.As one of the major air pollutants,NO_x may cause acidic rain and haze,which damages the ecological environment severely and endangers people's health.Therefore,great attention has been paid to the emission reduction of NO_xin recent years.The selective catalytic reduction?SCR?technology is the most effective process of removing NO_x.It is characterized by high denitrification activity and good selectivity.Catalyst is the core of SCR denitration system and V₂O₅-WO₃?MoO₃?/TiO₂ is the most widely used denitration catalyst in coal-fired power plants.The actual operation environment of SCR catalyst is complex,so the catalyst will gradually be deactivated and eventually abandoned due to various reasons.It is necessary to dispose the waste catalyst properly to avoid environmental pollution and resource waste.Regeneration is the best way to dispose the waste SCR catalyst.Therefore,this paper is concerned with study of the deactivition mechanism and regeneration method of SCR catalyst.The deactivition mechanism of industrial V₂O₅-WO₃/TiO₂catalyst was characterized by XRF,XRD,TEM and FTIR.And the study of cleaning regeneration and activation regeneration for deactivated catalyst were carried out by orthogonal design.The results are as follows:?1?A large amount of fly ash deposited on the surface and the honeycomb pores of the deactivated SCR catalyst.The specific surface area and pore structure properties of the catalyst did not change significantly.The support TiO₂is still maintains the anatase type,and the active ingredients V₂O₅ and WO₃ did not agglomeration.But alkali metal K,alkaline earth metal Ca,and SO₃ has been detected in the deactivated catalyst.Beyond that,the active components of the catalyst have occurred to a certain degree of loss.Therefore,the denitration activity of the SCR catalyst decreased..?2?The deactivated SCR denitration catalyst was regenerated by alkaline washing with aqueous ammonia and acid washing with nitric acid in turn.For the regenerated samples,orthogonal analysis was carried out with the denitration efficiency of 360?as the index.The analysis of the orthogonal experiments showed that the best cleaning and regeneration process of waste SCR catalyst is to wash the deactivated catalyst with 0.05 mol/L aqueous ammonia for 10minutes,and then treat it with 0.15 mol/L nitric acid for 10 minutes.By using this process to regenerate the waste SCR catalyst,the harmful substances covered on the surface of catalyst such as ammonium sulfate,alkali metal and alkaline earth metal can be removed.The crystal structure of support TiO₂ will not be affected too.However,some active components will be lost at the same time,so the denitrification activity of SCR catalyst can not be effectively recovered only by cleaning treatment.?3?After cleaning and regeneration,the active components in the deactivated SCR catalyst were supplemented.The results showed that V₂O₅ and WO₃ could maintain a relatively even distribution on the catalyst surface within the load examined,and no crystallization occurred.At the same time,with the increasing of loading of active components,the denitration efficiency of the regenerated SCR catalyst increases.V₂O₅ mainly affects the low-temperature activity of SCR catalysts,while WO₃ has a great effect on the high-temperature activity of the catalysts.Both of them promote the denitrification efficiency of regenerated catalysts in the whole test temperature window.For the denitration activity at 360?,the best loading sequence is to load vanadium first and then tungsten,which can not only enhance the interaction between V₂O₅ and the support,but also facilitate the enrichment of WO₃ on the catalysts surface.The calcination temperature has little effect on the denitration activity of the regenerated catalysts.Therefore,after considering the denitration activity and investment cost,the optimal parameter combination of activation regeneration is that:the loading of V₂O₅ is 1.2%,the loading of WO₃ is 6%,tungsten oxide loaded after vanadium oxide and roasting at a temperature of 500?.The denitration efficiency of the best regenerated SCR catalyst is 98.36%.