流體化床燃燒爐中燃料分子結構對氮氧化物排放之研究

The Effect of the Molecular Structure of Nitrogen Compounds on NOx Emission in a Bubbling Fluidized Bed Combustor

紀奕廷(I-Ting Chi)

指導教授 ： 錢建嵩

中原大學/工學院/化學工程研究所/碩士(2014年)

https://doi.org/10.6840/cycu201400605

摘要

本研究係於一總高5.0 m之實驗室規模之氣泡式流體化床燃燒爐中進行實驗，其乾舷區內徑為0.154 m之圓柱體，燃燒室為0.22 m × 0.11 m之矩形。選用吡啶、吡咯、喹啉、硝基苯、苯胺、1-萘胺、精酸胺及尿素之模型化合物，與活性碳顆粒混合配製出含氮量範圍1.50-1.61 wt%的燃料，矽砂為床質，探討不同化學結構之模型化合物、床溫、乾舷區溫度及燃料含水量等各操作參數對NO排放濃度的影響。
實驗結果顯示NO及CO主要為於燃燒室內生成，隨著乾舷區高度增加而減少。煙氣中CO為促進NO還原反應條件之一。燃燒活性碳時，焦炭氮同時與NO進行異相生成及還原反應，所以NO排放濃度維持一定；NO生成隨氧濃度及乾舷區溫度增加而增加，未隨著床溫增加而增加。
NO轉化率隨燃料氮的含氮結構不同而有所差異。若以硝基形式為主，NO有較高排放濃度及較高轉化率的表現；雜環形式的吡啶、吡咯與喹啉，以及芳香胺形式的苯胺與1-萘胺其NO的排放濃度和轉化率則較低。各類化合物中，碳數愈多，乾舷區內之NO還原率愈高；若結構中具有苯環或含氧之官能基可以減少NO生成。燃燒模型化合物，NO排放濃度隨床溫增加而呈現先增加後減少之趨勢，因為在高溫狀態下碳與NO之非均相還原反應。燃料中水分增加，雖然會造成CO濃度增加，但可以有效減少NO排放濃度。

關鍵字

流體化床燃燒爐 ； 氮氧化物 ； 含氮模型化合物

並列摘要

The objective of this study is to investigate the effect of the molecular structure of nitrogen compound on NOx emission. Experiments are conducted in a bench-scale bubbling fluidized bed combustor (BFBC). The feeding material is prepared by mixing the model compounds including pyridine, pyrrole, quinoline, nitrobenzene, aniline, 1-naphthylamine, urea, and arginine, with activated carbon to keep overall nitrogen content at 1.50-1.61 wt%. In this study, the effects of operating parameters such as bed and freeboard temperatures, and moisture content on NO emission are also investigated.
The results reveal that burning pure activated carbon, NO emission changed insignificantly as the bed temperature increased from 750 to 900℃. It is due to that part char-N produces NO through the heterogeneous reaction. The other remnants of char-N reduce NO through the heterogeneous reduction at the same time. The remarkable feature is that the NO and CO concentration are high inside the bed and decrease progressively along the freeboard toward the exit flue gas in all experiment. The decrease of the NO concentration along the freeboard is probably due to the predominance of destruction reactions by CO. Besides, the NO emission increases with freeboard temperature increased. The conversion of the fuel-N to NO is correlated with nitrogen-containing model compound type. The nitrobenzene of aromatic compound is the highest in NO conversion among all tests and followed by heterocyclic compounds and aromatic amino compound. The oxygen-containing compounds are the lowest. The results of adding moisture to the feeding mixtures are showed that NO emission is significantly reduced, while CO emission is increased.

並列關鍵字

Nitrogen oxides ； Nitrogen contained model compounds ； Fluidized bed combustor

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