Experimental validation of kinetics and VLE of carbon di-oxide absorption in aqueous MEA at deep removal conditions

The increasing attention for deep removal (99 %+) of carbon di-oxide (CO₂) from flue gases, requires confirmation of absorption kinetics and VLE under the relevant operating conditions. In this work, the CO₂ absorption rate and the equilibrium capacity in aqueous solution of 5 M Mono-ethanolamine (MEA) is investigated for the deep-removal regime (2000 ppm to 100 ppm CO₂) using a stirred-cell contactor. The absorption flux is measured over a temperature range of 20–45 °C with solvent loadings from 0 to 0.36 mol CO₂/mol MEA, while the equilibrium capacity is evaluated between 30–60 °C, at solvent loadings ranging from 0.05 to 0.35 mol CO₂/mol MEA. For the accurate measurement of absorption kinetics under these conditions, the gas-phase mass transfer coefficient (k_g) was characterized using various solvent systems. The kinetic and VLE data presented in this work covers the experimental conditions not studied before, still very relevant to the deep CO₂ removal operating conditions. The absorption kinetics are reported as the absorption flux per unit driving force (referred to as specific absorption flux). The specific absorption flux allows an independent assessment of absorption kinetics (as a function of solvent loading and temperature), unaffected by possible errors introduced by the solubility and diffusivity data. The specific absorption flux is described using an Arrhenius type equation. The application of specific absorption flux for calculating the absorber column height in Aspen Plus is illustrated with a typical Natural gas combined cycle (NGCC) case.