Study On Supersonic Expansion Liquefaction Technology Of Natural Gas

So far,the research on laval nozzle is mostly focused on the area of using its supersonic expansion to refrigerate the natural gas to a lower dew point,and very few attention is paid to the area of using its supersonic expansion to liquefy natural gas.Based on gas dynamics,fluid mechanics and numerical heat transfer theory,with the help of HYSYS and Fluent software,the article aims to research natural gas liquefaction characteristics in the nozzle to apply it to the design and improvement of the liquefaction process by changing inlet and outlet gas pressure and temperature furtherly,achieving the primary exploration of the liquefaction of natural gas in the laval nozzle.Build the methane and mixture of methane,ethane and propane flow model in the nozzle to research and analyze its flow condition and possibility of liquefaction.And then,build the one-dimensional steady model of nozzle isenthalpic process and choke valve isentropic process to explore the liquefaction characteristics of nozzle and choke valve.Based on those research,apply the nozzle to design a liquefaction process of the regulator station and improve a N2-CH4 expansion liquefaction process.The research shows that,the fluid velocity,the Mach number increase and the gas pressure,temperature,density decrease in the nozzle.Finally the mixed gas reaches the pressrure and temperature condition of liquefaction in the nozzle.And increasing inlet gas pressure and decreasing inlet gas temperature,outlet gas pressure,methane ratio in the mixed gas could enlarge the liquefaction ratio in the nozzle.It is easier for mixed gas to liquefy in nozzle than in choke valve and the nozzle's isenthalpic liquefaction ratio is higher than choke valve's isentropic liquefaction ratio.The designed liquefaction process of nozzle in the regulator station achives the purpose of pressure regulating and has good applicability.Its liquefaction ratio is 18%.The performance per watt and water cooling load of the improved liquefaction process by nozzle are lower than choke valve and increasing the gas pressure and decreasing the gas temperature can reduce the performance per watt of the liquefaction process.