Investigation of supersonic separation mechanism of CO2 in natural gas applying the Discrete Particle Method

In order to study the separation mechanism of CO2 droplets and natural gas in a supersonic separator, different structure of cyclones were designed and the flow characteristics of natural gas in the supersonic separator were numerically calculated. The mathematical model of the continuous phase (methane gas) and the dispersed phase (CO2 droplets) was established, the distribution of the gas flow field and the droplets paths in the supersonic separator were obtained using Discrete Particle Method, the droplet separation efficiency was defined, and the effect of the droplet sizes and speed on the separation efficiency were analyzed. The results show that there is an obvious restriction relation between the pressure and tangential velocity distribution caused by the swirl blade, a balanced point (optimized structure) is necessary to achieve the purpose of condensation and separation of CO2 droplets. And the separation efficiency increases with the increase of droplet size and the CO2 droplets can be separated completely when the droplet size is greater than 1.5 mu m. The initial axial velocity has no obvious effect on the separation efficiency of the supersonic separator.