小型下抽式生質能氣化爐之研究

Study of Small Downdraft Biomass Gasifier

陳尚瑋(Shang-Wei Chen)

指導教授 ： 馬小康

國立臺灣大學/工學院/機械工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.01410

摘要

本研究以構造簡單、使用方便的固定床下抽式氣化爐配合稻殼進行氣化實驗，在不同的空氣進氣量、點火高度、燃料預燒時間、燃料含水量以及燃料尺寸等不同操作條件下，研究氣化爐產氣的成分、熱值、產氣量以及熱值輸出功率等，找出最佳的操作參數，並將其以生命週期分析的方式探討是否有發展潛力，成為穩定的燃氣來源。實驗進行的方式為將燃料於氣化爐內點燃之後，由爐體上方之進料器投料、產生的燃氣排出爐體後經由冷卻與過濾裝置淨化，排至燃燒器燃燒觀察，整個實驗過程都對溫度與空氣流量進行監控，並每10分鐘於產氣出口作一次氣體採樣。由實驗結果發現，本氣化爐的空氣流量偏低，當量比介於0.010 ~ 0.057導致反應溫度不夠高只能帶出燃料的揮發份，在此情況下空氣進氣量的增加可提高產氣量。點火高度若太高或過低，皆無法維持產氣輸出的熱值，本實驗最佳之點火高度為330mm。若將燃料愈燒後供給低空氣流量，則能明顯提升產氣熱值。使用未乾燥的燃料會導致爐體溫度下降且無法提升產氣熱值，而混何磨碎的燃料會造成空隙被堵塞並使反應趨向上層燃燒。以生命週期分析冷煤氣效率為3.02%的實驗四，計算出產氣之碳排放量為0.051kg CO2-Eq/MJ，略小於天然氣，在未來有繼續研究和發展的空間。

關鍵字

下抽式氣化爐 ； 生命週期分析 ； 生質燃料 ； 合成氣

並列摘要

In this study, a simple-structure fixed bed downdraft gasifier is used with rice husk as fuel to build up an experiment process. We discuss the gas composition, heating value, gas production rate, and heat output of gasifier with different operating conditions, which includes air inlet flow rate, ignition point, fuel preheating time, fuel moisture content, and fuel size. Determine the proper operation condition and use life cycle assessment to analysis the developing potential. The fuel is ignited in the gasifier and the additional fuel is fed with the upper manual feeding device. The product gas is cooled and cleaned then burn in a burner for flame observation. The gasifier temperature and air flow rate are monitored during the experiment and the gas is sampled every 10 minutes.
Experimental results of the gasifier indicate that the air inlet flow rate is lower. The equivalence ratio is between 0.010~0.057, which cause lower temperature and can only take out the volatile matter. In this condition, the gas production rate is rising as the air inlet flow rate increase. The proper ignition point is at 330mm and the heating value decreases in either higher or lower place. The preheated fuel can raise the heating value of gas with lower air inlet. Using undried fuel would cause the temperature drop down and reduce the gas heating value. The pulverized fuel would block the fuel gap and make the flame surface moving toward upper layer. The experiment No.4 with cold gas efficiency 3.02% is taken into life cycle assessment. The carbon emission of product gas is calculated as 0.051kg CO2-Eq/MJ, which is lower than using natural gas.

並列關鍵字

downdraft gasifier ； life cycle assessment ； biomass ； syngas

參考文獻

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