Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/2335
標題: 氨氣熱裂解產氫之數值探討
Numerical study of Hydrogen Production by Ammonia Decomposition
作者: 張嘉軒
Chang, Chia-Hsuan
關鍵字: 重組器;NH3 decomposition;氨氣熱裂解反應;填充床法;氨氣轉換率;packed-bed reactor;partially filled reactor;decomposition efficiency;volumetric feed rate
出版社: 機械工程學系所
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摘要: 
本文對使用在燃料電池上的重組器進行氨氣熱裂解產氫反應之模擬分析。使用FLUENT數值分析軟體探討圓管反應器中,觸媒層厚度變化、使用觸媒量的多寡以及不同溫度在不同流速下對氨氣熱裂解產氫反應之影響。
首先,參照文獻的圓管反應器尺寸、反應參數以及反應條件,將模擬結果與文獻做比對,得到良好的一致性後,以此對自行設計之圓管反應器進行氨氣熱裂解產氫反應。
圓管反應器之設計為流體由入口進入一壁面絕熱之乾淨流道後,
進入有填充著觸媒的反應區,此段壁面邊界條件將設為一等溫壁面,與一等熱通量兩種。最後在此段反應產生的氫氣、氮氣與未反應完全的氨氣,再經由一段壁面絕熱之乾淨流道流至出口。
模擬結果為溫度與流速變化是影響氨氣轉換率中最重要的因素,溫度愈高以及流速愈慢的情況下,反應效果愈好。在相同觸媒填充方式下,觸媒量的多寡,對氨氣轉換率的影響甚小。而在相同的觸媒使用量下,氨氣熱裂解反應會隨著觸媒層厚度增加,而提升其轉換效率;但在等熱通量壁面的條件下,e/R=1(填充床法)時,則會有最小的轉換率。

關鍵字:重組器、氨氣熱裂解反應、填充床法、氨氣轉換率。

The goal of this study aims to explore more understanding regarding the hydrogen production from NH3 decomposition for fuel cell applications. A numerical model based on the commercial computational fluid dynamics package Fluent is developed to solve the governing equations simultaneously. The numerical model is verified using the available experimental data reported in the literature using packed Ni-Pt/Al2O3 particles as the catalyst in a cylindrical reactor.
Based on the good agreement between the numerical and experimental data, the established numerical model is extended to investigate the NH3 decomposition efficiency using partially filled catalyst layer inside the reactor. It is intended to examine the flow effect on the NH3 decomposition. Under the same catalyst loading and NH3 feed rate, it is found that the packed bed reactor has better performance as compared with those with partially filled catalyst layers under the isothermal reaction. The reason may be attributed to that the decomposition is essentially temperature governed and flow plays insignificant role during the isothermal chemical reaction.
Since heat flux is usually applied at the reactor wall in practical operation of reactor, the present study also investigate the NH3 decomposition efficiency with heat flux applied at the reactor wall. Under such thermal condition, it is found that the reactor with partially filled catalyst layer has better performance as compared with the packed bed reactor. This is because of large temperature gradient generated by the fast flow outside the catalyst layer.
For both isothermal and applied heat flux operated reactors, the present study also shows that NH3 volumetric feed rate is an important factor that determining the decomposition efficiency in addition to the type of catalyst.

Keywords: NH3 decomposition, packed-bed reactor, partially filled reactor, decomposition efficiency, and volumetric feed rate.
URI: http://hdl.handle.net/11455/2335
其他識別: U0005-2108200911142200
Appears in Collections:機械工程學系所

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