A thermodynamic robust model to assess hybrid solvents for CO₂ capture

The molecular-based soft-SAFT equation of state has been applied to describe the chemisorption of CO₂ in non-aqueous hybrid solvents of mixtures of AMP and glycols. The reactive nature of the CO₂ absorption process in non-aqueous amines was implicitly modelled by the formation of CO₂-amine physical aggregates bounded by strong and localised intermolecular interactions. This modelling framework only required VLE data on the absorption of CO₂ in amine solvents, without the need for additional information such as speciation reactions or equilibrium constants. Subsequently, the developed models were used to examine the CO₂ capture performance of these hybrid solvents in terms of absorption cyclic capacity and heat of regeneration as key performance indicators using a simple and short-cut estimation method. Results show that for the same total amine mass concentration, non-aqueous AMP solvents possess a 30-40% decrease in total heat of regeneration compared to their aqueous counterparts at the expense of a 20-50% reduction in cyclic capacity. These results validate the reliability of the molecular modelling approach as an attractive and valuable tool for the screening of chemical solvents and process modelling.