台灣某火力電廠機組SCR選擇性脫硝觸媒使用10多年後因觸媒失活而塗補再生’但 使用2年後發現部分觸媒支撐材有破裂之情形，破裂觸媒的放置位置集中於煙氣出口轉角 處，本文從背景調查、現場勘查、觸媒表面觀察、支撐材材質分析、表面成分分析、金相 組織分析、剖面成分分析等多方面綜合探討火力電廠機組SCR選擇性脫硝觸媒破損之原因。 根據分析結果觸媒支撐材之破壞屬長時運轉應力腐蝕破壞所造成，長期運作下，煙氣出口 轉角處成爲最先產生應力腐蝕破壞之區域。

SCR catalyst installed in a fossil power plant of Taipower had been regenerated due to deactivation after ten years’ service. However, a part of the catalyst's substrate was ruptured after two years’ reinstall. The destroyed catalyst's substrate was always occurred at the flue gas export corner. The purpose of this article is to find out the reasons of failure for SCR catalyst's substrate by background analysis and site investigation methods which included surface observation, analysis of substrate material, surface composition analysis, microstructure analysis and the profile composition analysis. According to the results of analysis, the main reason of catalyst substrate failure was due to stress corrosion cracking during long-term operation, and the initial region of stress corrosion cracking was occurred at flue gas export corner.