Evaluation of dynamic behaviors in varied swirling flows for high-pressure offshore natural gas supersonic dehydration

Abstract

The dehydration process involving the supersonic separator (SS) proves advantageous for the high-pressure offshore natural gas industry. By adeptly harnessing energy conversion from pressure to cold energy, the SS efficiently condenses and separates water vapor. In this process, swirl strength is the critical factor. To clarify the influences of different swirl strengths on flow field characteristics, droplet behavior, film formation, separation performance, and energy conversion of the SS in high-pressure offshore natural gas, a computational model was established and validated in this study. The prediction results of three representative thermodynamic models were compared in the Laval nozzle and the SS. The results show that the NIST real gas model possesses the highest prediction accuracy compared to the other two models. The inlet pressure has a significant influence on the separation performance of the SS. The maximum values of water vapor removal rate, dew point depression, optimum droplet diameter, and optimum droplet concentration can increase to 81.75 %, 37.65 K, 3.3 μm, and 0.0026 kg s−1, respectively. The swirl strength significantly influences separation performance and energy conversion. Notably, the normal swirl strength achieves the maximum separation performance, showcasing a water vapor removal rate surpassing that of strong swirl strength by 18.03 %. The temperature drop exhibits maximum deviations of 20.70 % and 12.51 % compared with weak and strong swirl strengths. Moreover, the utilization of supersonic separators in the pre-dehydration process results in a substantial cost reduction of $ 6,691,060 over a 20-year period.