Research On Natural Gas Liquefaction Technology Based On Supersonic Flow Phase Transition Condensation Mechanism

Since ENGO and Shell introduced natural gas swirling technology into the field of natural gas processing in 1996,ENGO and Shell have achieved airtight leak-free,compact,non-rotating components and the ability to achieve expansion at the same pressure drop compared to throttles Lower temperature and other characteristics,aroused widespread concern of researchers in various countries.Especially in the field of deep dehydration and deep cooling,it has broad application prospects.If it can be applied to the field of natural gas liquefaction,the existing natural gas liquefaction process can be greatly simplified and the energy consumption level of the system can be greatly reduced.In an earlier study,researchers conducted a study of supersonic dewatering devices and put them into industrial applications and showed more excellent dewatering efficiency than the corresponding conventional dehydration devices,but the core technology of nozzle design for supersonic dehydration had no public report.However,the application of supersonic swirling separators based on this principle to the field of natural gas liquefaction is extremely immature at present.Although some researchers in China have been conducting corresponding researches,most of them stay in the theoretical stage,and considering the swirling situation under the full three-dimensional hypersonic simulation needs to be further carried out,there is no precedent for industrial applications.Therefore,the system design and research of natural gas liquefied supersonic swirling separator are suitable for industrial applications become the focus of this dissertation.In this dissertation,the research status of the supersonic swirling separation technology,the structure design method of supersonic swirling separator and the basic theory and numerical simulation technology of supersonic swirling separation were investigated.The effects of supersonic swirling technology on the production of LNG the application prospects,to determine the main research content.Based on the study of spontaneous condensation mechanism of high-speed expansion of gas,a two-fluid mathematical model of gas-swirling supersonic condensation flow is established.By combining the structural design analysis with the internal flow mechanism,a three-dimensional full flow field simulation is carried out.Taking the production parameters of an LNG peak shaving station as an example,the detailed design and scheme comparison of various parts of the supersonic swirling separator were carried out.An experimental system was designed and constructed to test the core indexes affecting the supersonic nozzle performance,so the indoor experiment is used to test the optimal operation range of the key process parameters of the designed device by the combination of experiment and numerical simulation.A complete design scheme of the supersonic swirling separator for LNG,the optimal structure size,judging principle and analysis method of the best entrance parameter are obtained.In order to promote the industrial application of the technology,the subject focuses on the liquefaction efficiency of the supersonic nozzle with the designed structure,which shows that although the supersonic nozzle has higher liquefaction efficiency than the throttle valve,it does not have an absolute advantage.In order to improve the liquefaction efficiency of supersonic nozzle by adding LNG condensing core and multistage nozzle series combination shows that this method can obviously improve the liquefaction efficiency.On the basis of this,aiming at a domestic LNG peak shaving station,the liquefaction process was optimized by the supersonic swirling separator studied in this paper,and the LNG production process with supersonic swirling separator was modified.After optimization,the energy consumption of the process system is 37% lower than that of the original process system,which shows that the technology has a good application prospect.Finally,through summarizing the research contents,research conclusions and innovations,the future research direction and ideas are put forward.