Mass and heat transfer characteristic in MEA absorption of CO₂ improved by meso-scale method

CO₂ capture affords to control the greenhouse gas emissions effectively. Monoethanolamine (MEA) absorption of CO₂ shows great potentials to mitigate the industrial CO₂ emission. Unfortunately, it is an energy-intensive process. A meso-scale model was developed to characterize coupling effects between micro-scale and phase-scale to intensify the MEA absorption process. Mass transfer coefficient (MC) and Nusselt number (Nu) are used to determine the mechanisms among micro-scale, phase-scale and meso-scale. It is found that meso-scale MC and Nu do not equal to the sum of micro-scale and phase-scale values due to the interaction effects between micro-scale and phase-scale. MEA conformer, O-N distance, temperature and slip velocity significantly affect the meso-scale MC and Nu due to their strong impacts on film structure and interphase area. The liquid film thickness and length decrease by 40% and 32% as slip velocity increased from 0.1 m/s to 0.3 m/s, respectively, while the interphase area increases by 6%. The energy consumption is reduced to 2.65 GJ/t under the gGt MEA conformer, saving 17% energy against the experiment baseline case. The meso-scale model is proved to be a useful method to intensify the amine solutions absorption of CO₂. Adjusting pH value, concentrating the amine solution to 9 kmol/m³, extremely increasing the absorption temperature up to 353.15 K and adding nano Fe₃O₄ are the feasible ways to achieve the meso-scale intensification effects.