Migration And Curing Characteristics Of Arsenic In Waste SCR Denitrification Catalyst

At present,most coal-fired power plants was faciliated SCR denitrification system,while most of the catalyst will lose the activity after 2-3 years of operation due to sintering,fouling,arsenic?As?poisoning.Since the waste catalyst contains volatile heavy metal As,it must be treated or recovered to avoid secondary pollution.In this work,the migration characteristics of As in water bath were investigated.The heat release characteristics of As in waste catalyst were also studied.Based on the information,the experimental and thermodynamic calculations were used to study the effects of CaO and Fe₂O₃ on the arsenic fixation in the waste catalyst.Firstly,the surface morphology of the waste catalyst was observed by SEM,and its chemical composition was analyzed by XRD.The elemental composition of the waste catalyst was analyzed by XRF,automatic solid mercury analyzer and ICP-OES technical.Subsequently,the migration characteristics of waste catalyst under leaching conditions were investigated.The results show that the As in the catalyst own the highest content among all the?metal?elements,with the mass fraction of up to 1.5%?54.72 mg/L?.When leaching with deionized water,As in the catalyst easily dissolves in the filtrate with concentration of634.2mg/L.When leaching with acid solution,the pH value of leaching solution has great impact on As leaching behavior.Smaller pH value of leaching solution generally means higher solubility.Then,the high temperature heat release characteristics of As in waste catalyst and the fixation of CaO and Fe₂O₃ in arsenic under high temperature were discussed by experiment and thermodynamic calculation.The heat release characteristics show that the As in the waste catalyst start to evaporate at 600?and form gaseous As₄O₆,and increasing temperature promotes the release of arsenic.The volatilization ratio can achieve 84.6%at1000?,while the volatilization ratio was only 12.7%when the catalyst was doped with 5%CaO.Furthermore,CaO can effectively inhibit the As volatilization between 600-1000?with the best inhibition effect at 3%of CaO concentration.As a comparison,Fe₂O₃ has a weak inhibitory effect on As volatilization.CaO can effectively inhibit the dissolution and transfer of As into water environment.