本文借助COMSOL套裝軟體，以數值模擬方式探討內部觸媒為Ni/Al2O3圓管固定床反應器之周邊設定對CO甲烷化反應之影響，如模型建立時反應管前無填充觸媒之長度、管外熱損失、流量，管壁材料。由於反應屬於放熱量較大之反應，且對溫度極為敏感，故需注意不能只單單針對觸媒填充區做計算，而且要回溯到尚未填充觸媒之區域。結果顯示，越長的前置管會使進入觸媒區的氣體溫度越高。本文使用不鏽鋼管(AISI 316)、鋁管(ASTM 6061-T6)、紅銅管(銅含量>95%)三種常見管材做計算，不同的管壁材料各自具有不同的熱傳特性，尤其在這種放熱量大的更是需要注意熱傳的影響。在絕熱時，這三種管材，銅管最能表現出均溫的效應。管外熱損失則是設定不同的熱對流係數以模擬反應管絕熱的程度，我們發現有熱損時，在轉換率下降不多時，可以接受較廣入口溫度範圍。另外，反應熱會增加反應溫度亦會藉由管壁傳往入口並同時對氣體產生預熱作用。所以，一旦反應產生之後，溫度上升會增加氣體分子碰撞的機率，反應速率也會非常快速的攀升，導致反應多數集中在反應管子前端。整體來說，適當的預熱、管壁熱傳能力越好，將會使CO甲烷化效率更好。

This paper investigates how surrounding setting affects the CO methanation in catalyst Ni/Al2O3 tubular fixed bed reactor by numerical analysis with commercial software COMSOL. The settings include length of the tube before reactants contact the catalyst, heat loss from wall and inlet, flow rate and materials of reactor. Since CO methanation is a strong exothermic reaction and is sensitive to the reaction temperature, we need not only consider the catalyst region but also the whole tube. As a result, adiabatically, longer the tube before reactants contact the catalyst, the higher will the temperature increases. This paper considers three different materials, stainless steel(AISI 316),aluminum (ASTM 6061-T6) and copper( copper content>95%). Each material has different thermal conductivity which plays an important role in heat transfer. Cases show that copper can achieve better temperature consistency. In addition, we consider different heat convection coefficient in order to simulate heat dissipation of the reactor outer surface. With better heat dissipation, the reactor can withstand a greater range of inlet temperature. Furthermore, we discover that the heat of reaction will increase the reaction temperature and also preheats the reactant gas by conduction from the wall of reactor. Consequently, once the reaction initiate, temperature rises which promotes the probability of air molecular collision and thus making reaction rate even faster resulting in that the reaction almost only take place at the front end of the reactor. Therefore, with appropriate preheating and heat transfer of reactor wall, we can achieve a greater performance of CO methanation.

第一章 緒論 1
1.1 前言 1
1.2 文獻回顧 1
1.3 研究目的 8
第二章 反應器 9
2.1驗證用之模型 9
2.2不同前置管長之反應器模型 10
第三章 數學模式與數值方法 11
3.1 模擬軟體介紹 11
3.2基本假設 12
3.3 統御方程式 12
3.4 化學反應 15
3.5 邊界條件 16
3.6數值方法 18
第四章 結果與討論 19
4.1 等溫模型 19
4.1.1反應動力式驗證 19
4.1.2等溫下不同流量之影響 22
4.2絕熱模型 24
4.2.1不同前置管長的影響 24
4.2.2絕熱時不同流量的影響 28
4.2.3不同管壁材料的影響 32
4.2.4入口處管壁不同邊界條件的影響 38
4.3有熱損失之模型 40
4.3.1不同外壁熱對流係數的影響 40
4.3.2不同管壁的影響 42
4.3.3不同流速的影響 45
4.3.4管內CO分布情形 47
第五章 結論 51
5.1結論 51
5.2 未來展望 53
參考文獻 54

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