660MW燃煤电厂商用SCR催化剂的失活与再生

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

以某660 MW燃煤电厂运行30000 h的商用SCR脱硝催化剂为实验对象,在新鲜催化剂为参照下,结合SEM、BET、NH_3-TPD、XRF和XPS等表征方法,考察了商用SCR脱硝催化剂失活原因和硫酸清洗再生效果。结果表明:运行30000 h的SCR脱硝催化剂失活的主要原因是碱金属(K和Na)、砷和硫酸盐在催化剂表面沉积,堵塞了催化剂的微孔,降低了催化剂比表面积,并且碱金属、砷等与催化剂表面酸性活性位点反应,降低了催化剂表面的酸性强度。运行30000 h的SCR脱硝催化剂经过稀硫酸再生后,350°C脱硝性能由42.62%提升到78.30%。酸洗再生能有效脱除催化剂表面的碱金属,对砷和硫酸盐也有一定脱除作用,并有利于SCR脱硝催化剂表面酸性强度增加,化学吸附氧含量比例提升,这些均能提高SCR脱硝催化剂脱硝活性。

Used commercial SCR catalysts（30000 hours） obtained from a 660 MW coal-fired plant in Zhejiang Province（China） were examined by SEM, BET, NH_3-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.