Abstract: Regarding the significant impacts of flue gas flow fields and ash deposition on the SCR catalyst lifetime prediction in practice, the SCR reactor potential is proposed to represent and evaluate the macroscopical performance of multilayer series catalyst based on the analysis of the mass field and laboratory test data. Combined with the characterization of catalyst activity, a novel methodology is established to evaluate the macroscopical performance and precisely predict the catalyst lifetime by adopting the potential and activity degradation function. Through the degradation function of the catalyst of each layer, the specific plans of catalyst addition, replacement and regeneration can be determined. This method has been successfully used for the comparison and selection of the ultra-low NOx emission retrofitting plan of a 1 000-MW unit. The outcome indicates that low NOx combustion retrofit and used catalyst regeneration are both efficient and economical ways to improve the SCR performance. Nevertheless, the combination of these two methods together can achieve the best effects.

Key words: thermal power plant, de-NOx, SCR reactor potential, catalyst activity, macroscopical performance, lifetime prediction