Non-equilibrium condensation in flue gas and migration trajectory of CO₂ droplets in a supersonic separator

Previous studies have found that supersonic separation has the possibility to capture CO₂ from flue gas, thereby reducing carbon emissions. In this study, a CFD model is proposed to describe the non-equilibrium condensation in the nozzle. Based on the condensation parameters and discrete particle model, the motion behavior of CO₂ droplets in the supersonic separator is predicted, and the effects of initial saturation and initial supercooling on the separation efficiency and non-equilibrium condensation are clarified. The results show that three representative migration trajectories are summarized based on the effect of centrifugal force on the motion behavior of CO₂ droplets. Increasing the initial saturation and initial supercooling can greatly improve the liquefaction capacity and separation capacity of the separator. When the initial saturation increases by 0.12, the liquefaction capacity and droplet separation efficiency increase by 44.6% and 41.2%, respectively. When the initial supercooling increases by 9.01 K, the liquefaction capacity and separation efficiency increase by 24.1% and 16.1%, respectively.