Effects of Varying Spiral-Ring Pitches on CO₂ Absorption by Amine Solution in Concentric Circular Membrane Contactors

The CO₂ absorption flux while using monoethanolamide (MEA) solution in a spiral-wired channel was significantly enhanced by optimizing both the descending and ascending spiral ring pitch configurations within the filled channel. In this study, two distinct spiral ring pitch configurations were integrated into concentric circular membrane contactors to augment CO₂ absorption flux. Spiral rods were strategically inserted to mitigate concentration polarization effects, thereby reducing mass transfer boundary layers and increasing turbulence intensity. A theoretical one-dimensional model was developed to predict absorption flux and concentration distributions across varying MEA absorbent flow rates, CO₂ feed flow rates, and inlet CO₂ concentrations in the gas feed. Theoretical predictions of absorption flux improvement were validated against experimental results, demonstrating favorable agreement for both ascending and descending spiral ring pitch operations. Interestingly, the results indicated that descending spiral ring pitch operations achieved higher turbulent intensity compared to ascending configurations, thereby alleviating concentration polarization resistance and enhancing CO₂ absorption flux with reduced polarization effects. Specifically, under conditions of a 40% inlet CO₂ concentration and 5 cm³/s MEA feed flow rate, a notable 83.69% enhancement in absorption flux was achieved compared to using an empty channel configuration. Moreover, a generalized expression for the Sherwood number was derived to predict the mass transfer coefficient for CO₂ absorption in concentric circular membrane contactors, providing a practical tool for performance estimation. The economic feasibility of the spiral-wired module was also assessed by evaluating both absorption flux improvement and incremental power consumption. Overall, these findings underscore the effectiveness of optimizing spiral ring pitch configurations in enhancing CO₂ absorption flux, offering insights into improving the efficiency and economic viability of CO₂ capture technologies.