Joule-Thomson effect and flow behavior for energy-efficient dehydration of high-pressure natural gas in supersonic separator

Abstract

The supersonic separator liquefies and removes water vapor of natural gas by using the pressure energy and cold energy recycles. To analyze the energy efficiency of the supersonic separation process, a novel CFD model combined with the Eulerian-Lagrangian model and the Eulerian wall film model was established for high-pressure conditions with Redlich-Kwong real gas model. The accuracy of the present model was validated based on the existing experimental data. The Joule-Thomson effect, entropy generation, and flow behavior were studied coupling with processes of swirl and phase change. The results showed that inlet pressure influences flow characteristics, entropy generation, and optimum parameters of the foreign droplets. As the inlet pressure rises from 6 bar to 120 bar, the centrifugal acceleration increases by 27.8%, the temperature drop caused by the Joule-Thomson effect increases from −0.1 K to 28.5 K, and the entropy generation decreases by 14.69% from 615.5 J kg−1 K−1 to 525.1 J kg−1 K−1. For the heterogeneous condensation, the optimum diameter of inlet foreign droplets increases by 100% from 1.7 μm to 3.4 μm, and the concentration increases by 177.8% from 0.0009 kg s−1 to 0.0025 kg s−1, which can maximize the dehydration efficiency to 78.9%.