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|Title: ||燃料噴霧粒徑對於節能式甲醇重組器暫態產氫特性之研究 （新制多年期第2年）|
|Issue Date: ||2009-12-30 10:43:42 (UTC+8)|
|Abstract: ||本研究設計一小型甲醇重組器，分為兩部分針對產氫之暫態過程進行研究。第一部分探討甲醇噴霧粒徑對於冷起動之暫態反應及產氫特性的影響；第二部分則針對重組器節能方法對於產氫特性的影響進行研究。進行主要研究之初，先以部分氧化法找出最佳冷起動及氫氣產率的操作參數，包括甲醇進料率及O2/C 等，再以此參數進行自發熱重組法探討噴霧顆粒的影響及節能的效果。節能方法即利用廢熱回收方式以提升產氫效果。經實驗結果發現，在較小的甲醇進料流率下，改變噴霧粒徑SMD 值對於重組器冷起動及產氫特性有明顯的影響。大致上較小的噴霧粒徑可得到較佳的甲醇轉化效率及快速的冷起動效果，但有最佳值的存在，亦即噴霧粒徑並非越小越好。甲醇進料率在24.9cc/min，配合噴霧粒徑30.1μm，觸媒溫度達200℃所需時間只須73 秒。不同甲醇進料流率，需搭配適當的噴霧粒徑才可獲得較佳的氫氣濃度。另外，採用熱回收方式雖可將高溫氣體回流至重組器外壁氣套，對重組器具有保溫的效果，減少系統對外的熱傳損失。但本研究發現，若氣流的導入位置不對，反而會使氣流對重組器造成冷卻效果，而使重組效果變差。於是本研究再針對原設計之熱回收系統改善之後，其測試結果則可獲得改善。與原系統相較下，在冷起動暫態過程，熱傳損失可減少37kJ/min 左右，而在穩態時可減少4kJ/min~6kJ/min 左右。在使用熱回收操作方式後，冷起動過程之甲醇轉換效率皆有明顯提升，比原系統高約11%左右，在穩態則高約2~3%；熱效率在穩態時也比原系統高出約5%左右。而在有效利用熱回收之後，氫氣產率也明顯從原系統的53%提升至熱回收者的58%。因此可以發現，在甲醇重組器採用熱回收方式之後，可使系統的整體效率明顯提升，但必須注意熱回收氣流的導入方向與位置。|
A small methanol reformer was designed to investigate the performance of hydrogen production in this study. The work was divided into two parts, the first was to explore the particle size of fuel spray on the cold start and hydrogen production; the second was to study the effect of energy saving schemes on the reforming. In the beginning, a partial oxidation reforming was performed to determine the parameters for the reformer for the best cold start and hydrogen yield, including the methanol supply rate and O2/C ratio. As a result, these parameters were then used for the study of the effects of particle size and energy saving on the reforming performance. The results showed that the effect of fuel particle size influenced the cold start and hydrogen production significantly in the conditions of the small methanol flow rates. On the whole, it had a best rapid cold start with a suitable particle size. Moreover, the time for the catalyst temperature reaching 200oC was only 73 sec with the methanol flow rate of 24.9cc/min and 30.1μm SMD of particle size. In addition, better hydrogen production was obtained with the appropriate particle size for each methanol flow rate. Furthermore, the heat transfer loss of the reformer could be reduced by recycling the reformate gas with high temperature into the outer gas jacket of the reformer. However, the reforming effect could get worse because of the cooling effect caused by the recycled gas stream. The gas jacket of the reformer was therefore re-designed, and the performance of the reformer was improved. Concerning the heat transfer loss, it had the improvement of 37kJ/min for the transient condition, and 4-6kJ/min for steady state. The methanol conversion efficiency had 11% improvement for the cold start, and 2-3% for the steady; and the thermal efficiency was improved by 5%. Further, the hydrogen yield was also raised from 53% to 58% by applying the heat recycling scheme. That is, the reforming performance could be improved by recycling the high temperature reformed gas stream; nevertheless the proper design of the flow path of the recycled gas was very important.
|Appears in Collections:||[機械工程系所] 研究計畫|
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