觸媒對多孔性介質爐之預混燃燒現象之影響; Effects of catalysis on premixed combustion in a porous media burner

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Title:	觸媒對多孔性介質爐之預混燃燒現象之影響;Effects of catalysis on premixed combustion in a porous media burner
Authors:	張宏禾;Hung-Ho Chang
Contributors:	機械工程研究所
Keywords:	觸媒;甲烷;燃燒;多孔性介質;methane;catalysis;combustion;porous media
Date:	2003-07-02
Issue Date:	2009-09-21 11:42:54 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本論文主要是利用實驗方法來研究甲烷，氫氣和空氣預混燃氣在多孔性陶瓷介質燃燒爐中的燃燒現象，另外在多孔性介質表面塗上不同的催化劑，此催化劑成分分別是氧化鑭和氧化鎂。實驗中將甲烷與空氣預先做均勻的混合，再送入燃燒爐中燃燒，等火焰穩定之後再通入所需要的氫氣流量。實驗中使用LabView 程式控制空氣及甲烷之流量、監測爐內溫度分布，並計算當量比及平均流速。燃燒爐的內徑是2.54公分、外徑10公分且高度20公分，裡面放了七塊多孔性介質，表面塗有催化劑的多孔性介質擺在燃燒爐的中間位置，實驗中討論爐體結構、當量比、流速、氫氣莫爾分率的改變對火焰造成的影響，並探討一氧化碳、氮氧化物和總碳氫濃度對以上各參數之影響。實驗測試的當量比條件為0.5、0.55、0.6和0.7，而氫氣在燃料中的比例為0、0.3和0.6。結果顯示在多孔性陶瓷介質燃燒爐中放置塗有催化劑的陶瓷塊有助於火焰燃燒溫度的提昇，增加燃燒效率。實驗結果也發現多孔性陶瓷介質燃燒爐燃燒時所產生的CO和的排放量相當低。添加氫氣會影響到火焰的位置，但可增加火焰速度或是造成燃燒速率過於快速。 The combustion characteristics of premixed hydrogen- methane-air mixture in a porous media burner with catalysts are studied experimentally. La2O3 and MgO are used as the catalysts in this work. They are supported on highly porous SiC and Al2O3 forms. Flow rates are controlled by mass flow meters. Gas temperature within the burner and CO, NOX, THC emissions are monitored throughout the experiments. Results show that the flame temperature is increased by adding catalysts due to the increased reaction rate. Flame positions are different for different material burners. For Al2O3 porous burners, flame is usually stabilized in the middle of the burner. But for SiC burners, flame is stabilized at near the inlet due to higher thermal conductivity of SiC. In addition, the stable region is wider for SiC burner and the flame temperature is higher due to better preheating effects. Addition of hydrogen in the methane-air mixture does not change the flame temperature very much. Although hydrogen does promote chemical reaction, but it also has higher thermal conductivity and cooling by convection is enhanced due to increase flame speed. For burners without catalysts, CO emission increases with the equivalence ratio and flame speed slightly because of shorter residence time. But the concentrations are all less than 15ppm. For burners with catalysts, the CO emissions are all reduced to below 5ppm. The catalysts do promote CO to CO2 conversion. On the other hands, NOX emissions are all in the range of 10-15 ppm.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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