Title Supersonic Condensation and Separation Characteristics of CO2-Rich Natural Gas under Different Pressures

Supersonic separation technology is a new natural gas sweetening method for the treatment of natural gas with high CO2 (carbon dioxide) content. The structures of the Laval nozzle and the supersonic separator were designed, and the mathematical models of supersonic condensation and swirling separation for CO2-CH4 mixture gas were established. The supersonic condensation characteristics of CO2 in natural gas and the separation characteristics of condensed droplets under different inlet pressures were studied. The results show that higher inlet pressure results in a larger droplet radius and higher liquid phase mass fraction; additionally, the influence of centrifugal force is more pronounced, and the separation efficiency and removal efficiency of CO2 are higher. When the inlet pressure is 6 and 9 MPa, the liquefaction efficiency at the Laval nozzle outlet increases from 56.90% to 79.97%, and the outlet droplet radius increases from 0.39 to 0.72 μm, and the removal efficiency is 31.25% and 54.52%, respectively. The effects of inlet pressures on the removal efficiency of the supersonic separator are complicated and are controlled by the combined effects of liquefaction capacity of the nozzle and centrifugal separation capacity of the swirl vane.