研究生: |
王奕翔 Wang,Yi-Xiang |
---|---|
論文名稱: |
觸媒質量分布對吸附助效甲烷蒸汽重組反應器之性能影響 Effect of Catalyst Mass Distribution on the Performance of Sorption Enhanced Methane Steam Reforming Reactor |
指導教授: |
許文震
Sheu, Wen-Jenn |
口試委員: |
王訓忠
陳建宏 |
學位類別: |
碩士 Master |
系所名稱: |
工學院 - 動力機械工程學系 Department of Power Mechanical Engineering |
論文出版年: | 2022 |
畢業學年度: | 110 |
語文別: | 中文 |
論文頁數: | 223 |
中文關鍵詞: | 甲烷蒸汽重組 、氧化鈣吸附 、填充床 |
外文關鍵詞: | methane steam reforming, calcium oxide adsorption, packed bed |
相關次數: | 點閱:2 下載:0 |
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本次研究以模擬方式進行實驗,實驗之數值模型會把整段觸媒床分為前後二段,並在固定吸附劑與觸媒質量比(ζ)、水烷比(S/C)、WHSV,以及在吸附劑質量平均分布的前提下,將前段觸媒床中部分觸媒質量調配至後段觸媒床,目的是為了改善在達到終止時間時,後段觸媒床中氧化鈣吸附劑利用率不高的問題,並觀察管狀氧化鈣吸附助效甲烷蒸汽重組反應器中的各個內部反應狀態,解釋在不同時段中,觸媒床內各反應速率的發生次序及分布現象。
本研究會利用CaO作為吸附劑來吸附總體甲烷蒸汽重組反應所產生之CO2以利於促進甲烷蒸汽重組反應的進行,而CaO吸附CO2的放熱反應也能夠作為熱量供給甲烷蒸汽重組反應,至於觸媒載體則會選擇Ni/Al2O3,用以提升觸媒能夠進行反應之表面積。
整體模擬反應會分為三組階段,依序為階段一、過渡階段、階段二,其中階段一之產氣會含有較高的氫氣含量,而在過渡階段時,由於觸媒床中吸附劑失效區會逐漸擴大,會使的CO2無法有效的被下游處新鮮的CaO吸收便被送往反應器出口,導致吸附反應速率開始下降,而這也將連帶影響甲烷蒸汽重組反應一起減弱,使此階段的氫含量開始驟降,而到了階段二時,觸媒床中吸附劑失效區幾乎會佔據整個觸媒床並失去吸附效果,所以此時觸媒床的主導反應會變為甲烷蒸汽重組反應,而整個觸媒也會因為蒸汽重組反應的吸熱效果變為低溫區。
本次研究發現,相較於觸媒床吸附劑與觸媒質量平均分布的案例,觸媒床前半部分配2g觸媒、後半部分配8g觸媒,其操作終止條件時間(在y_(CO,out)=1%所對應之時段)會延長16.68%,操作終止條件時間前的H2產量則會提升16.7%,而氧化鈣轉化率則會提升15.57%,把部份觸媒質量調整至觸媒床後段中,由結果來看,此種方法可以有效提升在操作終止條件時間時觸媒床吸附劑的轉化率,並能夠改善在操作終止條件時間時觸媒床吸附劑無法有效利用之問題。
而本研究也得出另一項結論,那就是出口溫度將會影響CO之出口去水莫爾分率,進而決定系統的終止時間,而整體觸媒床的溫度分布越均勻,通常能夠對應較高的產氫能力以及氧化鈣轉化率。
The numerical model of this study divides the entire catalyst bed into two parts, the front and the back, and the fixed adsorbent-to-catalyst mass ratio (ζ), water-alkane ratio (S/C), WHSV, and adsorbent mass average distribution, part of the catalyst mass in the front catalyst bed is allocated to the rear catalyst bed, the purpose is to improve the usage rate of the calcium oxide adsorbent when the termination time is reached.
We would observe the various internal reaction states in the tubular calcium oxide adsorption-assisted methane steam reforming reactor explain the occurrence order and distribution of each reaction rate in the catalyst bed in different time periods.
The reaction stage of this model is divided into three stages, namely: stage one, transition stage, and stage two. The gas produced in stage one has a higher hydrogen concentration. In the transition stage, due to the disability of capturing CO2 adsorbent in the catalyst bed. The failure area will gradually expand, so that the CO2 cannot be effectively absorbed by the fresh CaO downstream and then sent to the reactor outlet, resulting in a decrease in the adsorption reaction rate. In the second stage, the adsorbent failure area in the catalyst bed will almost occupy the entire catalyst bed, so the dominant reaction of the catalyst bed will become methane steam reformation reaction, and the entire catalyst will also become a low temperature region due to the endothermic effect of the steam reforming reaction.
In this numerical model, the catalyst bed will be divided into two sections, and discussion will focus on the difference in the hydrogen production at the time of operation termination conditions by the adjusted catalyst mass at fixed adsorbent to catalyst mass ratio (ζ), water/alkane ratio (S/C), WHSV, and the adsorbent mass ratio condition. It has been found that catalyst mass adjusted to the latter part of the catalyst bed can effectively improve the conversion rate of CaO. Compared with the case of average distribution catalyst mass, the case of catalyst mass distribution 2g in the front and 8g in the rear, its operation termination time will be extended 16.68%, the H2 production will increase 16.7%, and the CaO conversion rate will increase 15.57%.
The outlet temperature will also affect the molar fraction of the CO outlet, which can affect the termination time of the system. The temperature distribution of the entire catalyst bed can correspond to higher hydrogen production and the higher the CaO conversion rate.
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