Investigation of Effect of Improved Air Supply System on Gasification Efficiency in Downdraft Gasifier and Thermoelectric Modulus

為因應全球氣候變遷及溫室氣體減量，世界各國著重發展生質能源作為節能減排之方式。氣化技術即為使用生質能源之一種重要方式。本研究主要針對燃料為稻殼，進料率為1.8 kg/hr之下抽式氣化爐進行進氣系統改良，探討以不同進氣口角度進氣對於氣化效率的影響。實驗部分首先以不同當量比、進氣口角度、單向或多向等條件於下抽式氣化爐進行氣化實驗，實際分析產氣成分後，找出何種參數下合成氣熱值有最高值，之後在此條件下於爐壁貼上熱電模組再次進行氣化實驗，觀察其廢熱回收效益。最後整合熱值、冷煤氣效率、合成氣成分以及爐體溫度之分佈，探討此改變是否對氣化效率有所影響。 實驗結果顯示，在同樣當量比下，改良進氣系統以三向45度角進氣有最高的合成氣熱值與冷煤氣效率，在當量比為0.2時其值分別為10.67 MJ/m3及62.20%；這樣的結果與原本以單向90度進氣之系統相比，其最高熱值與冷煤氣效率分別為8.88 MJ/m3及44.11%，可見對氣化效率的提高有一定程度影響。在廢熱回收方面，於當量比0.2，以三向45度角進氣進行氣化實驗時，熱電模組之最大能量轉換密度為20.0 W/m2。To reduce the emission of greenhouse gases and improve the crisis of climate change, many countries make efforts actively on the technologies of renewable biomass energy. One of the promising technology, gasification, is also developing rapidly and widely applied in industrial use. Therefore, to improve the gasification performance, the aim of this study is to investigate the major parameters, such as equivalence ratio, air inlet angle, multi inlets of airflow and the characteristics of the higher heating value (HHV) of syngas and cold gas efficiency (CGE) by adjusting the air supply system in the bench-scale of feed rate of 1.8 kg/hr downdraft fix-bed gasifier which used rice husk as fuel. Moreover, the thermoelectric modulus was applied into the system to explore the efficiency of the waste recovery as the gasifier system operating under the optimum gasification performance. The results showed that the optimum higher heating value of 10.67 MJ/m3 and cold gas efficiency of 62.20% were obtained when equivalence ratio was 0.2 and the angle of the air inlet was 45 degrees under the case of 3-way air inlets. Compared with the air supply system which the angle was 90 degrees and single air inlet, the HHV and CGE were 8.88 MJ/m3 and 44.11% respectively. Thus the improved air supply system can increase both HHV and CGE effectively. In waste heat recovery respect, the results showed that the maximum power density of thermoelectric modulus can reach up to 20.0 W/m2