Mass Transfer Evaluation of CO2 Absorption in a Wetted Wall Column

The chemical absorption of CO₂ in solvents is considered as one of the mature process options for reducing CO₂ emissions in power plants. Solvents with fast mass transfer rates and high CO₂ carrying capacity are therefore desired and continue to be explored to reduce equipment size and its associated capital cost. The wetted wall column provides a relatively facile assessment of solvent mass transfer characteristics and was used in this study to analyze the performance of 30 wt% monoethanolamine (MEA) for CO₂ absorption at utility flue gas concentrations that will pertain over the height of an absorber in post-combustion CO₂ capture process.

In this work, different CO₂ gas concentrations were absorbed by MEA at various carbon loadings and the flux measured. The overall mass transfer of CO₂ into MEA was evaluated by considering the relative contributions of the gas and liquid side resistances. The applicability of the pseudo-first order approximation and the instantaneous reaction were assessed for the different conditions to determine the appropriate reaction regimes. It was determined that at lean solvent conditions with low driving force (representative of conditions at the top of an absorber), mass transfer was well modeled by the pseudo-first order approximation.