T22合金沉積混燒生質炭／煤之高溫腐蝕研究

High-temperature Corrosion of T22 Alloy under Co-firing of Biomass Charcoal / Coal Deposits

本研究主要探討T22鍋爐用鋼在400℃至600℃經1至25小時沉積混燒生質炭／煤之高溫腐蝕行為。從實驗得知，混燒生質炭／煤之氧化動力學皆遵守高溫氧化拋物線型定律，金屬損失量皆隨溫度及時間之增加而增加，400℃及500℃相較於600℃之金屬損失量較不明顯。於600℃混燒生質炭／煤所造成之金屬損失量約為空氣氧化之1.5至2倍；單純燃燒生質炭所造成之金屬損失量約為單純燃燒煤的0.7倍。經比較沉積混燒不同比例之生質炭／煤得知，生質燃料經炭化後之生質炭，可以有效去除S、Cl等元素，於燃燒過程所產生之灰燼、氣氛相較於純煤含有較低含量的硫、氯和鉀，鋼材在高溫時受到這些元素的侵害較低，故金屬損失量會因添加生質炭比例的增加而減少。沉積混燒不同比例生質炭／煤之高溫腐蝕機制，初期生質炭或煤尚未燃燒釋放出硫、氯等元素，為單純高溫氧化行為。後期為硫、氯等元素與合金產生硫化或氯化破壞氧化皮膜（oxide scale）之熱腐蝕行為。

The purpose of this study is to discuss high-temperature corrosion behavior of T22 alloy under several different conditions. According to experimental results, both oxide kinetics of biomass charcoal and coal followed the parabolic law; the amount of metal loss increased with both temperature and time increase. We varied 3 environmental factors. There were 3 temperatures: 400, 500 and 600 ℃; 5 time exposures: 1, 4, 9, 16, 25, hours. Finally, we used 5 different fuel mixtures: 0 %, 10 %, 20 %, 30 % and 100 % of biomass charcoal, with balance being black anthracite coal. The results indicate that a higher proportion of biomass charcoal in the fuel will lead to less loss of metal. Therefore, steels could suffer less damage from these elements at high temperature. As the result, the amount of metal loss would decrease with an increasing proportion of biomass charcoal.