Solvent concentration effect on mass transfer pinch in CO2 absorber using aqueous monoethanolamine

Solvent concentration is a crucial design parameter in CO2 capture using amine scrubbing since high solvent concentration enhances theoretical absorption capacity. However, the solvent concentration effect on absorption capacity under practical CO2 absorber operations has yet to be studied. This study investigates the effect of solvent concentration on mass transfer pinch in CO2 absorber. Adiabatic, intercooled, and isothermal absorbers using aqueous monoethanolamine (MEA) are modeled in Aspen Plus® with altered solvent concentrations in a wide range of operating CO2 lean loadings. Critical CO2 lean loadings are identified in adiabatic absorbers where the minimum liquid rate required significantly increases due to temperature bulge-induced mass transfer pinch. At critical lean loadings, high-concentration MEA deviates the most from the isothermal operation, experiencing severe penalties from the temperature bulge. The low-concentration MEA suffers less because its high liquid rate helps suppress the temperature bulge effect. Solvent intercooling benefits high-concentration MEA most when operated near the critical lean loading. This work identifies optimal intercooling strategies and operating lean loadings for solvents at varying concentrations, highlighting the necessity of solvent intercooling at high solvent concentrations. The findings will facilitate capitalizing on the benefits of enhanced absorption capacity and contribute to developing cost-effective CO2 capture processes.