Evaluation of CO2 absorption by blended piperazine and Methyldiethanolamine solvents in rotating packed bed

Abstract

Chemical absorption using amine solvents remains the most mature technology for CO2 capture, while large equipment footprint and mass-transfer limitations restrict its industrial deployment. This study evaluates the gas-liquid mass transfer of CO2 absorption by a blended MDEA-PZ solvent (preferred 24 wt% MDEA- 6 wt% PZ) in a rotating packed bed (RPB) for process intensification. The effects of gas and liquid flow rates, inlet CO2 concentration, solvent loading, temperature, and rotational speed on absorption performance were systematically examined. Correlations for absorption efficiency, the overall volumetric mass-transfer coefficient (KGa), and the height of a transfer unit (HTU) were established. Orthogonal analysis revealed that gas flow rate, inlet CO2 concentration, and solvent loading are the dominant factors, collectively contributing for over 80% of the overall effect. Under optimal operating conditions, the absorption rate reached 3.39 mmol/s. Compared to a conventional packed bed (PB), the RPB exhibited superior compactness and higher KGa across tested conditions. Although RPB's total energy consumption slightly exceeded PB's, its relative energy penalty diminished markedly with increasing inlet CO2 concentration, indicating a favorable energy compactness trade off. Beyond conventional parametric evaluation, this study identifies a loading-dependent transition behavior in absorption performance. Combined with bench-scale continuous cyclic experiments, it further provides a systematic assessment of the relationship between performance enhancement and energy implications in intensified CO2 capture systems.