Abstract:

Laser induced fluorescence (LIF) technique was employed to investigate the influence of additive component in gas phase on interfacial convection in the process of water-CO₂ dissolution. CO₂ concentration distributions in the liquid and their evolutions were obtained. Liquid side mass transfer coefficients were estimated using the measurement results. Rayleigh convection in the liquid occurred during water-CO₂ dissolution due to density gradient near the interface. The results showed that with the addition of ethanol of a low concentration (<8.47 mg·L^-1) in the gas, the Rayleigh convection enhanced and liquid side mass transfer was enforced. With further increase of ethanol concentration in the gas, Rayleigh convection and thus the liquid side mass transfer were inhibited. The experimental results also showed that the addition of dichloromethane in the gas is enhanced by both Rayleigh convection and the liquid side mass transfer for the process of CO₂ dissolution in water. With the increase of the concentration of dichloromethane in the gas, the liquid mass transfer coefficient tended to become constant.

Key words: laser induced fluorescence, interfacial Rayleigh convection, mass transfer coefficient, mass transfer enhancement factor

摘要：

采用激光诱导荧光（LIF）观测方法考察了在气相中分别添加乙醇和二氯甲烷分别对CO₂在水中溶解过程界面对流的影响，得到了液相中CO₂浓度分布及其演化的观测结果，通过物料衡算得到了相应条件下的液相传质系数。CO₂溶解过程会出现由密度梯度引起的Rayleigh对流。实验结果表明，当添加的乙醇含量小于8.47 mg·L^-1时，Rayleigh对流会被增强，进而促进了CO₂的溶解；随着气相中乙醇含量的增大，Rayleigh对流反而被抑制；气相添加二氯甲烷会显著增强Rayleigh对流，提高了CO₂的传质速率，随着气相二氯甲烷含量的增大，CO₂在水中溶解过程的液相传质系数呈现先加强后恒定的趋势。

关键词: 激光诱导荧光, 界面Rayleigh对流, 传质系数, 传质增强因子