- 學位論文
以質量平衡模式分析中空纖維薄膜吸收二氧化碳之質量傳送
Mass transfer analysis on the hollow fiber membrane absorption of CO2 using the mass balance law
摘要
本次研究的重點將會放在建立起中空纖維膜管模組氣體吸收反應器的反應模式與理論架構。在實驗中，將使用水和單乙醇胺溶液(MEA)為吸收劑，將吸收劑通入殼側；而CO2/N2：15/85混合氣體通入管側，並以質量平衡模式去對實驗做相互印證。 以水為吸收劑時，在本實驗的操作範圍內，總質傳係數會隨著液體流速的增加而增加，而不會隨著氣體流速的增加而減少。以MEA(aq)為吸收劑時，在本實驗的操作範圍內，其結果和水的結果一樣，而其總質傳係數會比以水為吸收劑時高了許多。以水為吸收劑的總質傳係數和以MEA(aq)為吸收劑時的總質傳係數之間的差值，會隨著液體流速的增加而變大。 而在以水或MEA為吸收劑且不回流實驗裝置的系統下，實驗值與模擬的結果之間表準偏差相差10以下，因此該質量平衡模式是可以描述本實驗之系統。在模擬的過程中我們發現到各個操作條件下的有效長度，而影響有效長度最大的變因是在於MEA的濃度，有效長度會隨著MEA濃度的增加減少。之後再使用該數值模擬方式，模擬以水或MEA吸收劑循環裝置之條件下，其氣體出口端的濃度變化，當中導入液體滯留時間與氣體滯留時間的項；當吸收劑以回流的方式循環系統時，水吸收劑受到液體流速的影響是較為顯著，而MEA受到氣體流速的影響較為明顯。
並列摘要
The main study focused on the model building of hollow fiber absorption of CO2 and the mass transfer theory. The model was based on non-wetted mode in which the absorbent (water or MEA) flows into shell side and the well-mixing gas (CO2/N2) flow into lumen side; whereas the liquid flow in the shell side was characterized by Happel’s free surface model. After the experiment, we used the mass balance law to simulate the system and check up the results. During the operating conditions, the mass transfer coefficient (Koverall) of water to CO2 was positive proportion to the liquid flow rate, and had no difference with the gas flow rate. When the absorbent was MEA, the tendency was the same as water, and Koverall of MEA is bigger than water and the difference became more pronounced as the increasing of liquid flow rate. For the simulation result of water absorbet or MEA absorbent in non-recycle way, the standard deviation between experimental results was less than 10, so we can announce that the the model we used can describe the system well. In the simulation results of MEA in non-recycle way, we found that the effective length was changed more pronounced with concentration of MEA, effective length was positive proportion to the concentration of MEA. After we build up the simulation method, we used the model to simulate the system when the absorbent was recycled and the larger module. After the simulation, we can know that the physical absorption was more siginificantly influenced by liquid flow rate, the time when gas output concentration was equal to inlet concentration, and chemical absorption was more siginificantly influenced by gas flow rate.