旋轉填充床中黏度對質傳影響之研究

The Effect of Viscosity on Mass Transfer in a Rotating Packed Bed

陳昱劭(Yu-Shao Chen)

指導教授 ： 劉懷勝

國立臺灣大學/工學院/化學工程學研究所/博士(2004年)

https://doi.org/10.6342/NTU.2004.00063

摘要

超重力場技術已成為製程強化範疇中的重要發展之一，所謂超重力場技術是利用液體與氣體在離心力場中進行接觸以增強質傳，此種設備又被稱為旋轉填充床。過去文獻中已經針對旋轉填充床的各項特性提出釵h實驗結果，然而，卻尚未有研究者系統地探討超重力系統中液體黏度與質傳之間的關係。
本論文利用氣提溶氧為實驗系統，探討旋轉填充床中牛頓流體(甘油溶液)與非牛頓流體(CMC溶液)之黏度對質傳的影響。實驗結果顯示，液膜質傳係數會隨著離心力的增加而增加，隨著液體黏度的增加而下降，但是下降的幅度不若傳統填充床中明顯，暗示超重力場系統在高黏度環境下強化質傳的效果將更為明顯。另一方面，以旋轉盤上的液膜流動為基礎，並進一步考慮填充物之堆積效應，則能夠藉由理論分析計算旋轉填充床中非牛頓流體之液膜厚度、表徵黏度與質傳係數。此外，改變填充床之內、外半徑則可觀察端效應的變化。利用理論計算得到之表徵黏度，並考慮端效應的影響，對實驗值迴歸則可得到一液膜質傳係數經驗式，能夠適用於本研究與文獻中各種實驗系統。
其次，利用水與甘油溶液吸收空氣中的揮發性有機物為實驗系統，對旋轉填充床中之氣膜質傳係數與氣體流態進行分析。結果發現氣體流動特性與傳統填充床中類似，因此可以利用傳統填充床之氣膜質傳係數關係式預測超重力場系統之實驗值。另外，本論文同時對超重力場系統中之液液微觀混合系統與液固吸附系統的特性進行研究。在液液微觀混合系統中，離心力有助於混合效率的提昇，超重力場系統之混合效率也優於其他混合器，而提高微觀混合效率則能夠降低質傳的阻力。在液固吸附系統中，提高轉速可使吸附速率增加，與傳統填充床相比，旋轉填充床具有較高的吸附速率與吸附量。

關鍵字

旋轉填充床 ； 超重力場 ； 微觀混合 ； 質傳 ； 黏度

並列摘要

The application of a rotating packed bed (i.e. Higee) has become one of the most significant developments in the field of process intensification. It is achieved by contacting liquids and vapors in a centrifugal field to intensify mass transfer. Though the characteristics of a rotating packed bed have been widely studied in literatures, the influence of liquid viscosity on mass transfer was not systematically investigated.
In this study, experiments of deoxygenation were performed with viscous Newtonian fluids (glycerol solutions) and non-Newtonian fluids (CMC solutions). Results showed that mass transfer could be enhanced by centrifugal force, and reduced by increasing liquid viscosity. Less influence of liquid viscosity on mass transfer was obtained in a rotating packed bed than in a packed column, indicating that a more significant enhancement on mass transfer could be achieved in a rotating packed bed as liquid viscosity increases. On the other hand, a theoretical analysis based on laminar liquid film flow on a rotating disk with the assumption of the randomly inclined surfaces in a rotating packed bed was developed to predict the film thickness, apparent viscosity and mass transfer coefficient. Besides, the end effects in a rotating packed bed was investigated with various radii of the packed bed. Based on the calculated values of apparent viscosity, a correlation taking end effects into consideration was obtained to predict the liquid-side mass transfer coefficient. Agreement between the predicted values and the experimental values of the liquid- side mass transfer coefficient in this study as well as in literatures was quite good.
Further, the characteristics of gas-side mass transfer coefficients and gas-flow behavior were investigated based on the experiments of absorbing VOCs into water and glycerol solutions. It is found that the gas-flow behavior was similar to that in a packed column, and a correlation for a packed column was applicable to predict the gas-side mass transfer coefficient in a rotating packed bed. In addition, the characteristics of a liquid-liquid micromixing system and liquid-solid adsorption system were investigated. Results showed that, in a rotating packed bed, micromixing efficiency could be enhanced by centrifugal force, and was higher than other mixing devices. The mass transfer resistance may be reduced with increasing micromixing efficiency. Besides, in a liquid-solid adsorption system, the adsorption rate increased with increasing rotational speed. Compared with a packed column, higher rate and amount of oil adsorbed were obtained in a rotating packed bed.

並列關鍵字

higee viscosity ； mass transfer ； rotating packed bed

參考文獻

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