以臭氧深度氧化NO之效率探討;Evaluation of NO Conversion via Ozone Catalytic Oxidation

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Title:	以臭氧深度氧化NO之效率探討;Evaluation of NO Conversion via Ozone Catalytic Oxidation
Authors:	盧鈺雯;Lu, Yu-Wen
Contributors:	環境工程研究所
Keywords:	臭氧;一氧化氮;五氧化二氮;臭氧催化氧化;ozone;nitrogen oxides;nitrous pentoxide;ozone catalytic oxidation
Date:	2023-08-09
Issue Date:	2024-09-19 17:40:10 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究開發臭氧結合觸媒之脫硝技術(Ozone catalytic oxidation, OZCO)，利用臭氧強氧化之特性，可將煙氣中NO氧化為NO2與N2O5，此系統結合濕式洗滌塔，透過N2O5之高溶解特性有效的去除NOx，研究以TiO2及CeO2為觸媒載體，利用負載不同雙金屬觸媒氧化NO，比較觸媒之間的差異對NO氧化效率之影響。研究主要分為兩大部分探討脫硝技術開發，第一部分為摻雜金屬氧化物之TiO2及CeO2觸媒於NO氧化效率試驗，實驗結果顯示O3/NO比值、操作溫度及停留時間對NO氧化效率皆有重大影響。本研究以含浸法製備10 wt% FeMn/TiO2、CoMn/TiO2及FeMn/CeO2觸媒，FeMn/TiO2於100℃ N2O5產率為79±2.84%，FeMn/CeO2於100℃ N2O5產率為85±1.6%，當操作溫度上升至150℃時，因為動力學及熱力學的限制造成N2O5產率分別下降至48.9±1.03%及46.1±2.0%，此外，當停留時間由1.2 s上升至2.4 s時，未添加觸媒之N2O5產率由22.5±1.24%上升至57±0.62%，採用FeMn/CeO2觸媒之N2O5產率由53±1.9%上升至61±3.7%，由結果可知於較短之停留時間 (1.2 s)添加觸媒可顯著的提升N2O5產率，另外，測試觸媒及溫度對O3分解效率的影響，於未添加觸媒條件，臭氧分解效率隨溫度增加而上升，FeMn/TiO2、CoMn/TiO2及FeMn/CeO2觸媒於25℃~150℃皆展現100%的臭氧分解效率，研究結果顯示本研究製備之觸媒具優異的臭氧分解性能。本研究利用COMSOL Multiphysics軟體建立模型，結果顯示實驗數值與模擬數值整體趨勢接近，但N2O5及NO2之模擬數值略高於實驗數值，可能原因為氣相之N2O5及NO2較不穩定，容易沉積於管壁。最後，設計濕式洗滌塔並串聯臭氧氧化系統，研究不同濃度之N2O5氣流對NO去除效率之影響，以純水為洗滌液，分析出流水之組成分，結果顯示含有較高濃度之N2O5氣流展現接近100%之NOx去除率，且出流水之主要成分為硝酸。;Integration of ozone (O3) catalytic oxidation (OZCO) with wet scrubbing has a high potential for effective removal of NOx, due to the solubility enhancement from oxidation of NO to N2O5. This study focuses on the factors affecting NO oxidation, including the ratio of O3/NO, the operating temperature and the presence of catalyst. Fe, Co, and Mn loaded on TiO2 and CeO2 support material were prepared for experimental tests. The results indicate that the ratio of O3/NO has a critical effect on NO oxidation. When O3/NO ratio < 1, NO is converted to NO2. Meanwhile, NO2 is converted into N2O5 as O3/NO ratio exceeds 1. Notably, with O3/NO ratio of 1.7 and FeMn/CeO2 catalyst, the yield of N2O5 exceeds 80% at 100°C with 2.4 s of residence time, with no ozone leftover is detected. As the temperature is increased to 150℃, N2O5 starts to decompose into NO3 and NO2. In addition, the effects of catalyst and temperature on O3 decomposition efficiency are evaluated. In the absence of a catalyst, the ozone decomposition efficiency increases with increasing temperature. An FeMn/TiO2, CoMn/TiO2 and FeMn/CeO2 catalysts achieve 100% ozone decomposition efficiency within the temperature range of 25°C to 150°C. The results of kinetic model slightly overestimates due to N2O5 deposition on the reactor wall as confirmed by the presence of white powder. This paper demonstrates that the application of N2O5 in an absorption system can effectively reduce the usage of chemicals and water.
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