彭子桓 探討鹼金族元素在流體化床氣化爐燃燒過程對生質能產氣的影響
The effect of alkali metals on efficiency of gas generation during fluidized bed biomass gasification process
摘要
本研究主要應用人工模擬廢棄物並混合不同添加劑(鹼金族 Na 與 K，鹼土族 Ca)，
模擬燒結去流體化行為對於氣泡式流體化床氣化爐產氣的影響。除了去流體化時 間外，產氣效率的評估分為氣體組成、氣體產量、碳轉化效率、氣體熱值與總體
能量轉化效率。起初先探討不同操作溫度(700℃、800℃、900℃)、當量比
(Equivalence ratio, ER；0.2、0.3、0.4)、水氣與生質物比(Steam/biomass ratio, S/B： 1、1.5、2)。 而在基礎測試實驗中，再未添加鹼金族的情形下，隨著溫度與 ER 的提升，產氣 量與碳轉化效率有升高的趨勢。溫度越高與能量轉換與氫氣比例亦越高。而S/B 最佳建議比例為1.5 倍。而當添加 0.7 %鹼金族 Na 或 K 後，皆有提升氫氣產量的 趨勢。而在搭配1.5 倍的水氣後，所獲得氣體產量與碳轉化效率更高，但氣體熱 值與能量轉換有下降的情形。且研究中亦發現了無論產氫量、產氣量、碳轉化效 率及能量轉化K 皆比 Na 要來的好，而當改變鹼金族濃度(0.1 – 0.7 %)時可以提高 氫氣體產量，但去流體化行發生後會降低碳轉化效率、氣體熱值及能量轉化效 率。而當添加0.7 %鹼土族金屬 Ca 後，燒結去流體化的時間有延長的趨勢，且也 有助於氫氣的產量，隨著去流體化時間的延長，產氣量、碳轉化效率、氣體熱值 及能量轉化效率也有不同的表現。
The aim of this study determines the effects of agglomeration/defluidization in buble fluidized bed gasification process. The artificial biomass consisted alkai metals and alkaline earth metal to simulate the agglomeration/defluidization. The operating temperature, ER and S/B were considered in the gasification process. The
defuilization time and the gas generation behavior (gas composition, gas yield, carbon conversion, heat value of gas and cold gas effiviency) were determined. The results indicate that increasing temperature and ER were promoted the gas yield and carbon conversin. And the high tempertuare also increased the rate of hydrogen in the syngas and the cold gas effiviency. So, the 1.5 S/B was the best parameter in this study.
When the alkai metal was added into the artificial biomass, the gas composition, gas yield and carbon conversion were increased. The heat vale of gas and the cold gas effiviency were decreased with the 1.5 S/B. The potassium was better than sodium in the gas generation behavior. On other hand, increasing the concentration of the alkai metals could promote the rate of hydrogen in the syngas. However, it may increase the risk of agglomeration/defluidization. After the agglomeration/defluidization, the
carbon coversion, the heat value of gas and cold gas effiviency were desreased. Addition of alkaline earth metal (Ca) not only could inhibit the
agglomeration/defluidization, but also increase the rate of hydrogen in the syngas. This result shows that the gas generation behavior in buble fluidized bed gasification process is affected not only the alkai metals and alkaline earth metal but also the agglomeration/defluidization behavior.
