小型流體化床中操作參數對氧化亞氮排放之研究

The Effects of Operation on Nitrous Oxide Emission in a Bench-scale Fluidized Bed Combustor

陳志達(Chih-Ta Chen)

指導教授 ： 錢建嵩

中原大學/工學院/化學工程研究所/碩士(2002年)

https://doi.org/10.6840/cycu200200291

摘要

近年來，氧化亞氮的排放引起多方注意，因為N2O已在1997年的京都議定書中，列入六種溫室氣體之一，因其會造成溫室效應，使得地球溫暖化。N2O的另一危害是當其上升至臭氧層時，會與臭氧(O3)發生反應，使得臭氧層減少，而讓紫外線直射地球表面，造成危害。在流體化床燃燒爐(FBC)中，因其燃燒溫度比其他型式燃燒爐的燃燒溫度低，故N2O的生成量較高，因此降低N2O排放便成為一大課題。本研究係於一內徑0.025m之小型流體化床燃燒爐中進行，燃料為木炭及焦炭，並加入黃豆或尿素混燒，床質為石英砂，於不同的操作條件下，探討N2O之排放與操作條件之間的關聯性。操作參數包括：空床氣速、砂床溫度及混燒量，並以統計方法來找出操作參數與N2O排放之間的關係，且找出參數何者最重要，以期求出N2O減量的方法。

研究結果顯示，木炭與黃豆或尿素混燒時，N2O之排放會與氣速、床溫及混燒量三者有關，且兩參數之間會交互影響。而在焦炭與黃豆或尿素混燒時，N2O之排放則只有與床溫及混燒量有關，而參數間的交互影響不明顯。將實驗所得之數據，經由回應曲面法分析後，可得到N2O排放之預測式。木碳與黃豆(尿素)混燒下得到之預測式，其迴歸係數R-squared 為0.945 (0.973)，表示預測值與實驗值之關聯性高，關係式的可信度也越高。而在焦炭與黃豆(尿素)混燒下得到之關係式，其迴歸係數R-squared 為0.82 (0.82)，這是剔除關聯性不大的參數後，所得到之值，在可接受的範圍，表示關係式可用來預測N2O之排放。

探討個別參數對N2O排放之影響，由實驗結果顯示，床溫為最大影響之參數，其次是黃豆(尿素)之混燒量，氣速效應影響最小。溫度方面，當床溫增加時，N2O排放會下降。混燒量方面，發現當黃豆及尿素之混燒量增加時，N2O排放跟著上升，但在低床溫(750℃)及低氣速下，黃豆混燒量增加，會減少N2O排放。氣速方面，氣速增加，表示停滯時間減少，而N2O之排放則是呈現下降趨勢。

關鍵字

氧化亞氮

並列摘要

In this work, all the experiments were carried out in a 0.25 mm I.D. bench-scale fluidized bed combustor. Wood coal, coke, soybean and urea were used as feeds and quartz sand was employed as the bed material. The effects of various operating parameters, such as velocity (residence time), bed temperature, and co-combustion percentage on N2O emissions have been investigated.

The experimental results show difference in the co-combustion of soybean and urea. In wood coal, the emission of N2O was well correlated with operating parameters, velocity, bed temperature, and co-combustion percentage, with a determination coefficient R-squared of 0.945 for soybean and 0.973 for urea. In the part of coke, the emission of N2O was well correlated with operating parameters, bed temperature, and co-combustion percentage, with a determination coefficient R-squared of 0.82 for soybean and 0.82 for urea. Effect test indicates that the bed temperature has the most significant influence on the emission of N2O. The effect of temperature was more significant than the effect of velocity. In the wood coal and soybean co-combustion, the emission of N2O, only, was reduction in the low bed temperature and low velocity. But, in the co-combustion of urea, the experimental results show the emission of N2O increased with urea.

並列關鍵字

nitrous oxide

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