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  • 學位論文

過渡金屬含浸選擇性還原觸媒去除煙道氣中多重汙染物之研究

Removal of Multiple Pollutants from Coal-Fired Utility Flue Gases with Transition Metal Oxide-Doped Catalysts

指導教授 : 席行正

摘要


隨著世界能源需求持續成長,火力發電需求隨之提高,然而火力發電是主要空氣固定污染源之一,其排放污染物中包含重金屬如汞和酸性氣體如氮氧化物與硫氧化物等。鑒於其對環境的影響,2011年美國通過Mercury and Air Toxics Standards (MATS),此法將對燃煤電廠排放之重金屬汞、酸性氣體和其他有毒物種增加額外的排放限制。選擇性還原觸媒(SCR觸媒)是目前燃煤電廠常選用來控制氮氧化物之優良技術,相關研究也證實選擇性還原觸媒對元素態汞有良好的氧化效能,因此可提高後端濕式脫硫設備(Wet FGD)之除汞成效。本研究探討應用商用SCR觸媒同時氧化元素態汞、還原氮氧化物和去除硫氧化物之成效,並進一步利用過渡金屬鹽類進行SCR觸媒改質,藉由過渡金屬的催化活性以提升SCR觸媒對污染物之催化特性。本研究之SCR觸媒分別含浸5 wt% 釩、5 wt% 錳或5 wt% 銅,觀察SCR觸媒原樣與經過渡金屬鹽含浸之SCR觸媒,其物化性質之差異性,並評估在煙氣條件與氮氣條件下氧化元素態汞及去除氮氧化物及硫氧化物之成效,期許此材料能符合多重污染物去除策略。實驗結果顯示,SCR觸媒原樣與過渡金屬鹽改質之SCR觸媒的表面外觀沒有明顯變化,觸媒實驗結論顯示,氮氣條件下其觸媒對汞的氧化效率為6-23%,在模擬煙氣條件下觸媒對汞的氧化效率為45-97%,對氮氧化物的還原效率為65-89%,而不論是SCR觸媒原樣或經過渡金屬改質之SCR觸媒對SO2都有高去除效果。評估在三種過渡金屬鹽中,以釩鹽改質之SCR觸媒最具多重污染物去除之潛力。

並列摘要


Since the world’s economy grows rapidly, energy demand has kept growing. In recent years, the consumption of fossil energy for power generation in Taiwan was increased and caused a significant emission of pollutants from power plants. Mercury (Hg), NOx and SOx emissions from power plants have been the major focus of environmental works due to their severe health effects. In 2011, United States passed the Mercury and Air Toxics Standards (MATS), which regulates the emission limits for mercury, acidic gases, and other toxic species from coal- and oil-fired boilers. Multipollutant emission control has been extensively discussed recently, in general, referring to utilize one control device to simultaneously removal multipollutants, such as Hg, NOx, and SOx. In this study, the co-benefit effects of DeNOx catalysts on oxidation of Hg0 and removal of NOx, and SOx are evaluated. V2O5-WO3/TiO2 DeNOx catalysts was surface modified with transition metal oxides for simultaneously oxidizing Hg and removing NOx and SOx. A simulated coal-combustion flue gas generation platform associated a Hg/flue gas component monitoring system was established for experiments. The effects of chemical and physical properties of surface-modified samples on multipollutant controls are discussed. The results indicated that after transition metal oxides were doped, the surface area of catalysts increased but the total pore volume decreased. No significant changes on the morphology of SCR surface after surface modification. Results also showed that the Hg0 oxidation of DeNOx catalyst can be greatly improved after metal oxide doping. The Hg0 oxidation of raw DeNOx catalyst was approximately 48%; but the average Hg0 oxidation percentage of V2O5, Mn3O4, and CuO-modified DeNOx catalysts were > 70%, with the V2O5-modified catalyst having the greatest oxidation to up to 95%. The reduction of NOx was 65-89%; both raw and modified SCR greatly enhanced the SO2 removal. V-modified SCR showed the greatest potential for multipollutant controls in coal-combustion flue gaess.

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