Supersonic separation benefiting the decarbonization of natural gas and flue gas

Supersonic separation utilizes the cryogenics created by gas expansion to purify the mixture. This method is a novel carbon capture scheme. In this work, the models of N₂-CO₂ (flue gas) and CH₄-CO₂ (natural gas) are established to calculate the condensation flow. The condensation behavior of CO₂ in natural gas and flue gas is clarified respectively, and the difference between the two is compared for the first time. Under the same conditions, CO₂ in flue gas reaches the limit non-equilibrium state first, forming non-equilibrium condensation with limit nucleation rate of 7.78 × 10²⁰ m⁻³s⁻¹ and maximum droplet growth rate of 8.19 × 10⁻³ m s⁻¹. However, the maximum droplet growth rate in natural gas is only 2.22 × 10⁻³ m s⁻¹, which implies that the interphase mass transfer rate in flue gas is larger during the CO₂ condensation. In addition, the condensation behavior of CO₂ in natural gas is more sensitive to the changes of inlet parameters. This work provides an invaluable contribution to the development of supersonic carbon capture.