Numerical study on the influence of supersonic nozzle structure on the swirling condensation characteristics of CO2

Compared with other natural gas processing methods, supersonic separation technology has the advantages of small floor space, no internal moving components, and no chemical additives. At present, the research on supersonic separation technology mainly focuses on dehydration and heavy hydrocarbon removal, and there is little research on the use of supersonic separator to separate CO2 from natural gas. In order to study the influence of nozzle structure on the supersonic swirling condensation characteristics of CO2, a CO2-CH4 mixed gas condensation flow model was established, and the swirling condensation process of CO2 in the supersonic nozzle was simulated by the Fluent software. The results show that the liquefaction efficiency and separation efficiency of the separator increase with the increase of the nozzle expansion section length. When there is no back pressure at the nozzle outlet, increasing the nozzle expansion angle will increase the liquefaction efficiency but decrease the separation efficiency. The nozzle designed with Witoszynski curve has the highest CO2 liquefaction efficiency. Considering the above factors, the nozzle expansion length and angle are finally determined to be 100 mm and 3 degrees.