The Study On Mass Transfer Across The Gas-liquid Interface For Ethanol Desorption

Gas-liquid mass transfer is a very common phenomenon in chemical processes. Better understanding of the interfacial mass transfer behaviors, and further improvement in mass transfer theories are great importance for chemical industries. In this work, experiments were conducted to investigate the mass transfer process for the desorption of ethanol from ethanol-aqueous solution under the condition of gas-liquid co-current flow, The concentration and velocity distributions in the vicinity of the interface were measured and the mass transfer coefficient was estimated, and the analysis on the influential factors for the mass transfer was made.The Real-time Laser Holographic Interferometry was applied to measure the concentration distribution in the vicinity of the interface during the desorption process under different conditions of gas-liquid co-current flow. The experimental results revealed that, the decrease of concentration within boundary layer with approaching to the interface was in a parabolic form, and the concentration gradient increased as increasing the Reynolds numbers of both the gas and liquid, The fathomable near-surface concentration increased with increasing gas phase Reynolds numbers, and decreased with increasing liquid phase Reynolds numbers. The concentration boundary layer thickness decreased with increasing Reynolds numbers of both gas and liquid phases.With Laser Doppler Anemometer, experiments were conducted to investigate the liquid flow field inside the simulator channel. We obtained the time averaging velocity distribution in the vicinity of the interface, and the results indicated a logarithmic decrease in velocity with approaching to the interface.The above experimental results were used for estimating liquid mass transfer coefficients via an approach of mass balance based on an elementary volume near the interface, and average mass transfer coefficients in the liquid phase were obtained for different flowing conditions. The results were compared to those calculated with two-film model, and correlated with several influential factors.