Deactivation and Regeneration of Commercial SCR Catalysts Used in a 660 MW Coal-Fired Power Plant

Used commercial SCR catalysts (30000 hours) obtained from a 660 MW coal-fired plant in Zhejiang Province (China) were examined by SEM, BET, NH₃-TPD, XRF and XPS to investigate their deactivated and regeneration mechanisms. Fresh commercial SCR catalysts were chosen for comparison. The results indicate that depositions containing salts of alkali metals (K and Na) and compounds of arsenic and ammonium sulfate block pores of the catalyst, which decreases its BET surface. Moreover, the acidity of the SCR catalysts decreases due to the reaction of metal ions with activated acidic sites on the SCR catalyst surface. After catalyst regeneration with 0.5 mol·L^-1 dilute sulphuric acid, the activity of denitration increases from 42.62% to 78.30% at 350℃. Regeneration by pickling can effectively remove alkali metals from the surface of the catalysts, which also has certain effects in the removal of arsenic and ammonium sulfate. In addition, the augment of acidity and the increase of chemical adsorption oxygen proportion were examined after pickling, which are found beneficial to increase activity of deactivated commercial SCR catalysts for denitration.