A curved gas-liquid counter-current flow tube-in-tube microreactor for efficient CO2 absorption

Achieved efficient CO 2 absorption in curved TiTR under counter-current flow. • Overall volumetric mass transfer coefficient up to 0.97 s −1 . • Enhancement factor of gas-liquid mass transfer reached 1.35. • Trade-off between mass transfer enhancement and energy consumption evaluated. • Empirical correlation for mass transfer coefficient with 15% error. In recent years, the substantial emission of carbon dioxide (CO 2 ) has caused increasingly severe environmental issues. In response, policies related to carbon neutrality and carbon emission reduction have been rolled out. To achieve these goals, the efficient capture of CO 2 is essential. This work systematically elucidated the gas-liquid two-phase counter-current mass transfer mechanism for an efficient CO 2 absorption process using a curved tube-in-tube reactor (TiTR), which has a wide gas-liquid contact area and a new reactor structure. The variation of CO 2 absorption efficiency and the overall gas-liquid volumetric mass transfer coefficient ( k L a ) under different experimental conditions, including curvature diameter, pitch, and liquid flow rate, was systematically examined. Through the optimization of experimental conditions, the enhancement factor of k L a , which was defined as the ratio of k L a of the curved TiTR to that of the straight TiTR, reached 1.35, and k L a was up to 0.97 s −1 . In addition, the trade-off between mass transfer enhancement and energy consumption in the CO 2 absorption enhancement process within TiTRs with different geometries was evaluated. Finally, on the basis of the experimental data, an empirical equation correlating k L a with experimental parameters was further proposed. This equation can be used to predict the gas-liquid mass transfer in TiTRs.