Hydrodynamics and gas-liquid mass transfer in a cross-flow T-junction microchannel: Comparison of two operation modes

Abstract

Hydrodynamics and gas-liquid mass transfer of CO2-monoethanolamine (MEA) aqueous solution were investigated experimentally in a cross-flow T-junction microchannel. Two operation modes were compared, namely OM-1 (gas entering the branch channel, liquid flowing into the main channel) and the opposite feed mode OM-2 (gas entering the main channel, liquid flowing into the branch channel). The effects of gas and liquid rates and MEA concentrations in the two operation modes were studied in terms of bubble and liquid slug lengths, specific interfacial area, liquid-side mass transfer coefficient (kL), liquid-side volumetric mass transfer coefficient (kLa) and pressure drop (Δp). The results show that the variations of kLa and Δp with the total rate of two phases present a turning point in both two operation modes. Before the turning point, the gas rate is the key factor increasing the kLa and Δp, after that, the liquid rate would predominate. Notably, kL is more likely to be affected by the liquid rate. Comparing with OM-2, more dispersed gas-liquid distribution in OM-1 can be observed, which enhances the mass transfer but simultaneously increases the pressure drop. However, OM-2 is beneficial to a narrower residence time distribution in the liquid phase and better mass transfer performance under a strict energy requirement. This work could provide guidance for the operation of a cross-flow T-junction microreactor based on specific product requirements and energy consumption restrictions.