Enhancement of Gas-Liquid Two-Phase Flow and Mass Transfer in the Baffled Microchannel

The enhancement of gas-liquid two-phase flow and mass transfer in the baffled microchannel were investigated experimentally for CO₂ absorption into monoethanolamine/1-butyl-3-methylimidazolium tetrafluoroborate (MEA/ [Bmim][BF₄]) aqueous solutions. Three flow patterns were observed in the baffled microchannel: Taylor-bubbly flow, Taylor flow and broken-Taylor flow. The influences of baffle size on gas-liquid flow, mass transfer rate and pressure drop were explored via varying the MEA/[Bmim][BF₄] concentration ratio, gas-liquid flow rate and blockage ratio. The mass transfer enhancement by baffles relied dramatically on the gas-liquid two-phase flow characteristics. For the Taylor-bubbly flow occurring at low gas flow rates, the mass transfer performance was less affected by varying the liquid flow rate, the concentration ratio, or the blockage ratio. Once the flow entered the Taylor flow regime at moderate gas flow rates, mass transfer performance would be obviously affected. As the gas flow rate was further increased, the flow fell into a broken-Taylor regime, the higher fluid disturbance and bubble breakup would take place in this case, and the mass transfer would be greatly enhanced. Under higher two-phase flow rates, lower MEA/[Bmim][BF₄] concentration ratios and larger blockage ratios, the mass transfer intensification is more pronounced and the enhancement factor could reach to 1.5 with an acceptable increase in pressure drop 0.3 kPa (20% in relative term) compared to the unobstructed microchannel.. This work could serve as guidance for chemical process intensification and the design of equipment miniaturization.