Research On Recovery And Resource Utilization Of Waste SCR Catalyst Carrier TiO₂

In order to control the emission of nitrogen oxides(NO_x),selective catalytic reduction(SCR)flue gas denitrification technology has been widely used in China's coal-fired power plants,the core of which is catalyst.At present,V₂O₅-WO₃/TiO₂catalyst is the most widely used denitration catalyst in coal-fired power plants.Due to the fact that not all the catalyst can recover its activity after deactivation,a large amount of waste catalyst will be produced every year.However,the waste catalyst has been included in China's hazardous waste management,and it is mainly composed of valuable metal oxides such as those containing V,W and Ti.Therefore,it is of great significance to study related technologies for the safe treatment and resource utilization of waste catalysts.The main research contents and conclusions are as follows:1.The enhanced mechanical ball milling method was used to promote the dispersion of waste SCR catalyst carrier particles.The effect of process conditions such as the type of dispersant,solution pH,dispersant mass concentration and ball milling time on the particle size of the recovered waste catalyst carrier particles is systematically investigated.The experimental results show that the addition of sodium lauryl sulfate or polyoxyethylene lauryl ether during ball milling can enhance particle dispersion.The optimal process conditions for enhanced ball milling dispersion are polyoxyethylene lauryl ether as the dispersant,the pH of the solution is 6.7,the mass concentration of the dispersant is 10 g/L,and the milling time is 2 h.This process can reduce the median diameter of waste catalyst particles from 32.50?m to 2.19?m,and improve the quality of the recovered carrier TiO₂ for reuse.2.The waste SCR catalyst was washed by NH₄F/H₂SO₄ method to remove the impurities mainly containing alkali and Si O₂ in the waste catalyst.The recovered carrier mainly composed of Ti and W was obtained,which met the purity requirements of industrial titanium tungsten oxide powder.The recovered carrier was used to prepare a re-synthesis catalyst,and the difference between the physicochemical characteristics and catalytic activity of the deactivated catalyst and the fresh catalyst was studied.The experimental results show that,compared with the deactivated catalyst,the specific surface area of the re-synthesis catalyst,the ratio of V⁴⁺/V⁵⁺increases,and the reduction performance of vanadium is restored.At the same time,the activity of the re-synthesis catalyst is much higher than that of the deactivated catalyst,and it shows good N₂selectivity.3.Phosphoric acid-treated TiO₂ support was obtained by impregnation method,and V₂O₅-WO₃/TiO₂ catalysts with different P contents were prepared.The experiment results show that the addition of P can increase the denitration activity of the V₂O₅-WO₃/TiO₂ catalyst,especially the catalytic activity in the low temperature zone.And when the P₂O₅ content is 2.0%,the catalyst activity is best improved.The NH₃-TPD results show that adding P can increase the number of weak acid sites on the catalyst surface.