An effective hybrid solvent of MEA/DEEA for CO2 absorption and its mass transfer performance in microreactor

The gas-liquid two-phase flow and the mass transfer characteristics for CO2 absorption into the binary amine mixture of monoethanolamine (MEA) and N,N-diethylethanolamine (DEEA) aqueous solution were investigated in T-junction microchannel reactor with a square cross-section. The effects of gas-liquid flow rate and absorbent concentration on bubble length, velocity and mass transfer coefficient were studied. Three flow regimes including slug-bubbly flow, slug flow and slug-annular flow were observed under experimental condition, and the gas-liquid two-phase flow pattern map was depicted. It is found that the transitions between three flow regimes depend primarily on the competition of forces exerted on bubble in the T-junction. The kinetics of CO2 absorption into blended amine aqueous solutions was analyzed to understand the mass transfer enhancement mechanism of new hybrid solvent. Furthermore, the liquid-side overall mass transfer coefficient k(L) and the liquid-side overall volumetric mass transfer coefficient k(L)a were determined through processing experimental images recorded by a high-speed camera. The results show that k(L)a is in the range of (3.04-20.07) s(-1) in this work, which is 2-3 orders of magnitude higher than that in the conventional equipment. The dimensionless Damkohler number (Da) and Peclet number (Pe) are introduced to correlate the liquid-side volumetric mass transfer coefficient, new correlation shows good prediction accuracy with the average deviation of 3.64%.