Process Simulation Investigation of Purification and Deacidification in Supersonic Separation Process for Natural Gas Treatment

The Supersonic separation method is a novel and advanced technology for natural gas purification to condense and separate H2O, heavy hydrocarbon components, and other harmful impurities such as H2S and CO2 from raw natural gas. In order to study the performance of the supersonic separation process in natural gas purification and deacidification, the equivalent model of the supersonic separator was established in the process simulation software HYSYS, and process performance was simulated by using the Peng–Robinson equation of state. Evaluation indexes of process performance were put forward. The results show that due to the effective utilization of self-generating cold energy from the supersonic separator end, the improved process can have a better overall performance than the no precooling one. With the large-scale increase of feed pressure, H2S and CO2 removal rates are gradually larger, but the CH4 and pressure recovery effects are getting suppressed on a small scale of 5%. When the inlet pressure is about 10 MPa, the performance is the best: about 72% CH4 and 68% pressure energy can be recovered respectively, and H2S and CO2 removal rates are as high as 95% and 78% respectively. In addition, the change of the CO2 fraction at process inlet has a limited influence on the evaluation indexes of CH4 recovery and CO2 removal effects, and the CH4 recovery rate and CO2 removal rate are around 71% and 75% respectively. Hence, the supersonic separation process presents an excellent performance and adaptability for natural gas purification and deacidification.