二氧化碳捕捉及脫附裝置之數值模擬

Numerical Simulation of Carbon Dioxide Capture and Desorption in a Tube Filled with Activated Carbon and Zeolite

賴宏昇(Lai Hong Sheng)

指導教授 ： 陳俊勳

國立交通大學/工學院/機械工程系所/碩士(2019年)

摘要

本文採用ANSYS FLUENT軟體，針對圓柱型裝置中二氧化碳之物理吸脫附行為進行暫態模擬預測。首先和參考文獻進行模擬驗證，微小誤差原因主要來自於模擬版本差異，然後再進行參數模擬。入口速度保持在0.01m/s，而模擬參數除兩種吸附材料(活性碳及沸石)外，其餘為吸脫附材料的幾何形狀安排設計配置。在吸附時，活性碳能將CO2濃度在三種幾何形狀(三層薄片結構、兩層球型結構及三層球型結構)可分別降至17.9、18.15及18.1%，而沸石僅能降至18.88、18.95及18.9%。此時再將吸附濃度做為脫附初始濃度，而在脫附時活性碳能將CO2濃度由17.9脫附至19.2％；18.15脫附至18.95％及18.1脫附至18.9％，而沸石僅能將CO2濃度由18.88%脫附至19.4%；18.95%脫附至19.3%及18.9%脫附至19.25%。此吸脫附表現可以觀察出此流速的吸脫附效果並不理想，主要是流體在吸脫附裝置內之滯留時間愈短，其可吸脫附反應時間也越短所導致。為改善此一現象，在日後研究中在排氣管末端加裝氣體減速裝置是必要的。且經由比較可以看出活性碳之吸脫附能力優於沸石，故在吸附劑選擇上活性碳為較佳的選擇。最後，做進口溫度上調整，以313K、320K以及325K分別來觀察變化，以在325K時的吸脫附效果會比其餘的較低溫條件表現來的好，顯示溫度對吸脫附表現扮演非常重要的角色。

關鍵字

活性碳 ； 沸石 ； 物理吸附 ； ANSYS ； CFD ； 脫附

並列摘要

In this thesis, the ANSYS FLUENT (CFD Code) was adopted to simulate the transient adsorption/desorption phenomena of carbon dioxide (CO2) in a cylindrical tube. First, the simulation verification was carried out with a previous study. The reason of the insignificant discrepancy is mainly due to the different version of code. After that, the parametric study was performed. The inlet velocity was fixed at 0.01 m/s. In addition to the two adsorbent materials (activated carbon and zeolite), the arrangement and geometry of the adsorbent/desorbing materials, and inlet temperature were the parameters. Activated carbon can reduce the CO2 concentrations from 20 to 17.9, 18.15 and 18.1% in three geometric shapes, whereas zeolite can only be reduced to 18.88, 18.95 and 18.9% during adsorption. Then, the resultant adsorption concentration distributions were taken as the initial conditions for the following desorption. Activated carbon increases CO2 concentration from 17.9 to 19.2%; 18.15 to 18.95% and 18.1 to 18.9% for the three geometric arrangement during desorption. On the other hand, zeolite only increases CO2 concentration from 18.88% to 19.4%; 18.95% to 19.3% and 18.9% to 19.25%. By comparison, it can be seen that the adsorption/desorption capabilities of activated carbon is better than that of zeolite, so activated carbon is a preferred choice in adsorbent/desorption selection. Finally, the effects of inlet temperatures at 313K, 320K and 325K were studied. It is found that the adsorption/desorption effects at 325K has the best performance, indicating that temperature plays an important role on the performance. It can be observed that the flow rate used in this study (0.01 m/s) is too small and not realistic. The main problem is that the shorter the stay time in the absorbent/recycle agent, the shorter the reaction time for adsorption/desorption. In order to improve this situation, it is necessary to install a gas reduction device at the end of the exhaust pipe or change the geometry and arrangement of absorbent/recycle agent in future research.

並列關鍵字

activated carbon ； zeolite ； physical adsorption/desorption ； ANSYS FLUENT ； CFD

參考文獻

參考文獻

[1] D. Gielen, "Energy technology perspectives," Paris: International Energy Agency, 2016.

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[3] 何無忌, "移動排碳源捕獲之挑戰與研發策略," 中華民國第40屆力學會議, 2016.

[4] 林宇騰, "管狀碳源捕捉裝置之數值模擬," 碩士論文, 國立交通大學, 2018.