A rate based model of a packed column for CO2 absorption using aqueous monoethanolamine solution

A comprehensive and simplified rate based mathematical model of a packed column for CO2 capture using aqueous monoethanolamine (MEA) solution is developed. The absorption unit model takes into account the effect of kinetic reactions on the mass transfer, the thermodynamic non-idealities, the hydraulics of the random packing and the absorber dimensions (diameter and height). It is implemented into the optimization environment GAMS (General Algebraic Modeling System).The proposed NLP model was validated by comparison of obtained results with published experimental data. Good accuracy of results has been obtained for experimental pilot plant scales. Once validated, the model was used to investigate the influence of main process parameters and the effect of different correlations to compute the effective interfacial area for mass transfer (a/at) on the absorption efficiency. Obtained results indicate that model solutions depend strongly on the correlations used to compute the (a/at). In addition, results assuming thermal equilibrium and thermal non-equilibrium in liquid and vapor phases were also compared. For both conditions and specific cases, similar concentration and temperature profiles in the liquid phase in the absorber were obtained.Finally, results obtained by solving different optimization problems are discussed. More precisely, the optimization consisted in determining the operating conditions to maximize the absorption efficiency defined as the ratio between the CO2 recovery in rich solution and the packing volume of the column. The effect of the main process parameters on the optimized results was also investigated.

► Simple mathematical models are possible to develop with reasonable accuracy of results.
► Equilibrium model accurately predicts experimental data for low gas flow-rate (0.14 mol/s).
► Rate based models are preferred for medium flue-gas flow-rate (737.00–927.00 mol/s).
► An optimal diameter distribution along the absorber improves the process efficiency.