Thermodynamics analysis of CO2 condensation in supersonic flows for the potential of clean offshore natural gas processing

The separation technology of carbon dioxide (CO2) is a key step to achieve high efficient carbon capture and storage targets. In the present study, we propose a new concept to remove CO2 from the offshore natural gas industry, which utilises the combined effect from nonequilibrium condensation phenomena in the supersonic flow and cyclonic separation process from swirling flows. The feasibility study of this concept is evaluated by using computational fluid dynamics modelling. The effect of thermodynamics properties on the phase change process in supersonic flows is analysed in detail. The results show that the supersonic flow can condense 28% CO2 in a liquid state from the main gas flow based on the real gas model. Nine orders of magnitude differences are observed between the mass generations due to the nucleation process and droplet growth process, which indicates that the droplet growth process contributes more significantly to the mass transfer during CO2 condensations. The ideal gas model both under-predicts the mass flow rate and the liquid fraction by 25% and 46% compared to the real gas model. This study demonstrates the potential application of the CO2 separation using the phase change behaviour in supersonic flows.