Taylor flow and mass transfer of CO2 chemical absorption into MEA aqueous solutions in a T-junction microchannel

The mass transfer of CO2 chemical absorption into monoethanol amine (MEA) aqueous solutions under Taylor flow in a T-junction microchannel was investigated experimentally using a high speed camera and two pressure sensors. Overall liquid side volumetric mass transfer coefficient (kLa), specific interfacial area (a), and overall liquid side mass transfer coefficient (kL) were obtained in terms of the image analysis and processing. The influences of operating conditions on overall volumetric mass transfer coefficient were studied systematically. Experimental results show that the bubble length decreases exponentially along the microchannel due to the CO2 reactive absorption. For a given concentration of MEA aqueous solution, both kLa and kL increase significantly with the increase of the ratio of the gas and liquid flow rates until closing to a constant. For different concentrations of MEA aqueous solutions, there exists a turning point in the flow rate ratio of gas and liquid phases. Before this point, lower concentration of MEA aqueous solution lead to higher kLa, while reverse tendency is found after this point. A semi-empirical correlation for predicting CO2 overall volumetric mass transfer coefficient accompanied with fast chemical absorption in the microchannel was proposed based on Higbie's unsteady-state diffusion theory, and the predicted values agreed well with the experimental data.