應用MnOx-CeO2/TiO2觸媒同時去除煙道氣中NO、汞及戴奧辛之研究;Application of MnOx-CeO2/TiO2 for simultaneously removing NO、Mercury and PCDD/Fs in flue gas

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Title:	應用MnOx-CeO2/TiO2觸媒同時去除煙道氣中NO、汞及戴奧辛之研究;Application of MnOx-CeO2/TiO2 for simultaneously removing NO、Mercury and PCDD/Fs in flue gas
Authors:	林宣宏;Lin,Syuan-Hong
Contributors:	環境工程研究所
Keywords:	汞;戴奧辛;NOx;選擇性觸媒還原;多重污染物控制;NO;Dioxin;Mercury;SCR;multi-pollutant emission control
Date:	2014-08-29
Issue Date:	2014-10-15 17:26:29 (UTC+8)
Publisher:	國立中央大學
Abstract:	透過單一空氣污染防制設備達到多重污染物控制，可降低投資及運轉成本並減少占地面積，故近年來日受重視。選擇性觸媒還原(SCR)程序主要應用於NOx之排放減量，文獻指出目前觸媒技術也應用於戴奧辛之去除及元素汞之轉化。本研究利用不同條件製備MnOx-CeO2/TiO2觸媒以同時轉化NO、戴奧辛及汞，期望發展在較低操作溫度(<250oC)下能順利進行SCR反應之觸媒，獲取較佳之觸媒製備條件，並提高SCR技術之商業價值並降低操作成本。研究結果指出在NO去除方面，系統之操作條件為500 ppm NO、等量之NH3及氧含量10%，通過觸媒床總流量為2 lpm，改變觸媒配比、空間流速、操作溫度及鍛燒溫度皆會影響NO之去除效率，以鍛燒溫度400oC製備之Mn0.4-Ce0.13/Ti1-400oC為觸媒，當操作溫度為200oC，空間流速分別為20000 h-1、50000 h-1及80000 h-1時，NO之去除效率分別為100%、97.92%及82.73%。操作溫度由200oC上升至300oC時，開始有NO2之生成，並進一步發現隨NO2生成量增加，NOx之去除效率隨之下降。提高鍛燒溫度會造成觸媒燒結現象（sintering），使得小晶粒聚集成大晶粒，降低觸媒活性。在戴奧辛去除方面，戴奧辛去除效率隨著操作溫度的升高而呈現先下降後上升的趨勢，150oC、200oC及250oC之去除效率分別為98.3%、94.7%及99.4%，且破壞效率於操作溫度200oC顯著提升至91.8%，而吸附效率則明顯下降為2.9%。Mn0.4-Ce0.13/Ti1-400觸媒於200oC下對PCDD之去除效率達95.5%，對PCDF之去除效率為94.8%。在元素汞轉化測試方面，在150oC即有良好之轉化效率，並隨溫度上升(150、200及250oC)而略微增加，分別達87.5%、88.9%及89.1%。本研究成果指出在操作溫度200oC時，觸媒對NO、戴奧辛及元素汞有良好之去除或轉化效率。;Simultaneous control of multiple pollutants with a single air pollution control process not only reduces the capital and operating costs but also decreases the floor space. This concept has received much attention recently. Selective catalytic reduction (SCR) process is mainly used in reducing NOx emission, literature indicates that the current SCR catalyst technology is also effective in removing dioxins and oxidizing elemental mercury. This study investigates the effectiveness of MnOx-CeO2/TiO2 catalysts prepared with different conditions for converting three pollutants including NO, dioxin and Hg in gas streams. The objective is to develop the innovative SCR catalysts which can be operated at a lower temperature (<250oC) for high removal efficiency. The experimental results indicate that the NO conversion efficiency achieved with Mn0.4-Ce0.13/Ti1-400 catalyst reaches 97.9% when operated at 200oC. The results also show that NO2 was significantly formed as the operating temperature increased from 200oC to 300oC, and the increased NO2 generation will reduce NOx removal efficiency. The PCDD/F removal efficiencies achieved at 150oC, 200oC and 250oC are 98.3%, 94.7% and 99.4%, respectively. The PCDD/F destruction efficiency achieved with Mn0.4-Ce0.13/Ti1-400 catalyst reach 91.8% and the PCDD/F adsorption efficiency decreased to 2.9% as the temperature was controlled at 200oC. Experimental results also indicate that the Hg0 conversion achieved with Mn0.4-Ce0.13/Ti1-400 catalyst at 150oC, 200oC and 250oC reach 87.5%, 88.9% and 89.1%, respectively. The results indicate the Mn0.4-Ce0.13/Ti1-400 catalyst can be operated at 200oC for effective removal or conversion of dioxin, NO and mercury from gas streams simultaneously.
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