A potential strategy of carbon dioxide separation using supersonic flows

Carbon capture and storage (CCS) is one of the most promising technologies to tackle climate challenges. The separation of carbon dioxide (CO2) is the key step to achieve the economic and technical objectives of CCS. The present study proposes a potential strategy to separate CO2 using the phase change behavior in supersonic flows, which is not only a clean process of CO2 processing but also provides an efficient way to maximum utilize the thermal energy. To this end, a condensation flow model based on the real gas thermodynamics is developed to obtain an accurate evaluation of the heat and mass transfer due to the homogeneous condensation process of CO2 in supersonic flows. The prediction accuracy of the ideal gas model and real gas model is compared, and the result shows that the real gas condensation model presents a more accurate prediction of CO2 supersonic condensation with the root mean square error (RMSE) of 0.0147. The sensitivity of the two models to inlet pressure is analyzed, which shows that the ideal gas model under-estimated the liquid fractions of CO2 condensation by 2.8% of the total mass as well as over-estimated the latent heat by 20.1% at Wilson point during the heat transfer process. The condensation performances and Wilson point characteristics of CO2 are analyzed by using the real gas model. The prediction model of the relationship between the degree of supercooling, pressure, and expansion rate at the Wilson point was established with the mean relative error of 0.176% and the relative RMSE of 2.275% respectively, which is of great help for further forecasting to obtain the regularity of known data for CO2 separation in supersonic flows.