A Study On The KCI Poisoning Law And Anti Poisoning Method Of The V₂O₅/TiO₂ SCR Catalyst In The Presence Of SO₂

SCR denitration technology has been widely used due to its high denitration efficiency and no harmful by-products.The most widely used commercial catalyst is vanadium-tungsten-titanium catalyst.Vanadium-tungsten-titanium catalysts in biomass power plants and biomass blended coal power plants are susceptible to KCl in flue gas,which causing catalyst poisoned and deactivated,denitration efficiency decreased.While the poisoning temperature and poisoning content of KCl have different effects on the catalyst.It is important to study the activity of the catalyst under different poisoning conditions and to explore the regular of poisoning for the stable operation of the catalyst.At the same time,how to regenerate the poisoning catalyst by treatment and adjust it on the basis of the existing catalyst formula to achieve better anti-KCl poisoning performance is of great significance for prolonging the catalyst life.In this paper,firstly,the commercial vanadium-tungsten-titanium catalyst was used as the research object,and the activity of KCl poisoning catalyst at different K/V and different calcination temperatures was studied.Based on the activity test and the characterization of the catalyst which was carried out by NH₃-TPD and H₂-TPR,the poisoning mechanism of the catalyst under different poisoning conditions was obtained.The results show that different calcination temperatures and different K/V have different effects on the poisoning of vanadium-tungsten-titanium catalyst.The activity of the catalyst decreases further with the increase of KCl poisoning content?0.5,1.0,1.5?.With the increase of calcination temperature?320?,345?,370?,395?,420??,the activity of the catalyst showed an increasing trend between 345?-370?.While in other temperature ranges,the calcination temperature increased,which made the catalyst poisoning deactivation more serious.The denitration efficiency drops more.Then,the poisoned vanadium-tungsten-titanium catalyst can be regenerated by SO₂treatment,the activity of the poisoned catalyst is recovered and the activity intensity after recovery is also consistent with the order of activity intensity during poisoning.It is characterized by NH₃-TPD and H₂-TPR that the addition of KCl weakens the redox performance of the vanadium-tungsten-titanium catalyst,reduces the number and intensity of acid sites,and decreases the adsorption capacity of NH₃,thus reducing the activity.After the SO₂ treatment,although the strong acid sites were not recovered,the number of weakly acidic sites was restored.So the catalyst activity was regenerated and the denitration efficiency was increased.Secondly,a novel V₂O₅-Ce?SO₄?₂/TiO₂ high efficiency and anti-KCl poisoning catalyst was prepared.Based on the commercial V₂O₅-WO₃/TiO₂ catalyst,Ce?SO₄?₂was used instead of WO₃ to modify the catalyst.By comparing the denitrification activity and surface acidity of the novel catalyst and vanadium-tungsten-titanium catalyst before and after poisoning,highlight the advantages and causes of anti-KCl poisoning of the novel catalyst.The results show that the activity of the vanadium-cerium-titanium catalyst fresh sample is slightly lower than that of the vanadium-tungsten-titanium catalyst in the low temperature region,but the activity is almost same in the high temperature region.However,after the KCl poisoning,the activity of the vanadium-cerium-titanium catalyst can still maintain the high activity.Under the most severe poisoning conditions?K/V=1.5,calcination temperature is420°C?,there is still 45%catalytic efficiency,while vanadium-tungsten-titanium catalyst is only 5%at this time.So it can be summarized that the vanadium-cerium-titanium catalyst has strong anti-KCl poisoning ability.While the poisoned vanadium-cerium-titanium catalyst continues to be treated by SO₂,the catalyst can restore activity to fresh samples or even higher.It is characterized by NH₃-TPD and H₂-TPR that the acid number of fresh vanadium-cerium-titanium catalyst is lower than that of vanadium tungsten titanium catalyst,but the number of acid sites of vanadium-cerium-titanium catalyst after KCl poisoning and SO₂ treatment.And acid strength is stronger than vanadium tungsten titanium catalyst.Moreover,the vanadium-cerium-titanium catalyst can maintain the redox of the vanadium site before and after poisoning,at the cost of sacrificing the redox of the cerium sites.With the increase of K/V,the redox of the vanadium sites are reduced.However,the redox of the cerium sites were released.It can be seen from the above analysis that the vanadium-cerium-titanium catalyst can maintain its overall acidity and redox property before and after KCl poisoning,thereby maintaining its activity.Vanadium-cerium-titanium is a highly effective anti-KCl poisoning SCR denitration catalyst.