Serious catalyst attrition occurred in selective catalytic reduction(SCR)system of a domestic ultra-supercritical 660 MW unit once-through boiler

leading to the failure of the SCR device.Statistics shows the attrition area focused on near side of the boiler.Combined with the numerical simulation and testing data

the formation mechanism of the catalyst attrition was analyzed and the major reason is that the uneven distribution of fly ash causes the fly ash particles concentrate at the near side of the boiler and scour the catalyst's local area for a long time.Through regulating the positions of the Group I guidance plates at the horizontalπ-type flue duct

reducing the guiding plate number and increasing aguiding percussion device

the diffusion performance of the ash particles at the horizontalπ-type flue duct was improved.The relative root-mean-square of mass concentration of the fly ash at the horizontalπ-type flue duct decreased from0.331 to 0.241

resulting in a more even distribution of flue gas flow field and fly ash particle field at the horizontalπ-type flue duct and the vertical flue duct at top of the catalysts.Thus

the serious catalyst attrition problem was solved.