Decarburization of oilfield associated gas based on supersonic speed expansion and condensation technology

Key words:  oilfield associated gas  carbon dioxide  nozzle  supersonic speed  condensation

Abstract:

Oilfield associated gas usually contains a large amount of carbon dioxide and other acidic gases. In order to improve the quality of oilfield associated gas, it is necessary to remove carbon dioxide from the natural gas. The application of supersonic speed cyclone separation technology to natural gas to remove carbon dioxide is a new path, but the condensation characteristics of carbon dioxide under supersonic speed flow conditions need to be further clarified. A mathematical model of the phase transition process of carbon dioxide in the Laval nozzle was established, the supersonic speed condensation and flow characteristics of carbon dioxide were discussed, and the influence of inlet temperature and pressure conditions on the supersonic speed condensation characteristics of carbon dioxide was analyzed. The results show that the carbon dioxide will condense in the expansion section behind the throat of the nozzle, forming a large number of carbon dioxide droplets. With the increase of the temperature of the nozzle inlet, although the number of droplets produced by the condensation increases, the mass fractions of the liquid phase on the nozzle outlet and the central axis decrease, and the condensation position becomes closer to the nozzle outlet. With the increase of the inlet pressure of the nozzle, the pressure and temperature of the mixed gas at the nozzle outlet increase, and the corresponding velocity decreases. The number of droplets generated by carbon dioxide condensation in the nozzle decreases, and the mass fractions of the liquid phase at the nozzle outlet and central axis increase.