Modelling Phase Equilibria of Sulphur Compounds in Mixtures Relevant to Carbon Capture and Storage with New Association Schemes

This study models the phase equilibria of the sulphur compounds – SO₂, H₂S, and COS – in mixtures relevant to carbon capture and storage (CCS). The modelling tool used is the cubic plus association (CPA) equation of state. Modelling of binary and multicomponent mixtures of these sulphur compounds with CO₂, water, glycols, methane, and other inert compounds is performed. In the modelling approach, sulphur compounds are treated as inert or cross-associating (solvating) compounds with multiple association sites, culminating in the proposal of new association schemes. Throughout the study, the predictive and correlative performance of CPA is assessed. It has been found that the allocating of association sites for the sulphur compounds leads to improved modelling of phase equilibria behaviour. Further analysis against multicomponent systems will need to be performed to conclude on the appropriate association schemes for these compounds.