Aiming at solving the problem of abnormal black appearance of SCR denitrification catalyst in a power plant

the black catalyst samples were detected and diagnosed by X-ray diffraction

combustible content determination and leaching solution IC analysis. The black color of catalyst was caused by the deposition of ammonium bisulfate carrying the black fly ash

which was related to the fact that the inlet flue gas temperature of the denitrification system was lower than the minimum continuous ammonia injection temperature(MOT) during the shutdown process. The results of catalyst performance evaluation on the pilot-scale bench show that

the key parameters such as denitrification efficiency

ammonia slip

SO_2/SO_3 conversion rate can meet the performance requirements during the chemical life cycle. The catalyst performance can be recovered and continue to be used when the operating temperature reaches the design temperature. Based on the case of this accident and the mechanism of ammonium bisulfate poisoning

the operation and management suggestions of the catalyst at low load are put forward. The diagnosis method and conclusion of the catalyst operation accident provide the reference for the analysis and solution of similar problems.