超声速旋流分离器内天然气液化过程研究

Study on Natural Gas Liquefaction Process within Supersonic Cyclone Separator

目前关于超声速旋流分离器内天然气凝结液化过程的研究较少,为此,通过数值模拟计算对Laval喷管内气体凝结液化过程进行研究,并分析喷管结构对凝结液化的影响。研究结果表明,甲烷气体在喷管内发生了自发凝结现象,但凝结冲波现象并不明显,这与甲烷气体凝结过程液滴生长较慢且凝结潜热较小有关;随着喷管膨胀率的增大,气体过冷度增加越快,其能更早达到凝结液化条件(Wilson点);喷管内最大成核率、液滴数目及湿度(液化率)均随膨胀率的增大而增大,膨胀率从6 000 s-1增大到12 000 s-1,成核率最大值增加154.8%,液滴数目增加79.5%,喷管出口湿度增加51.7%,较大程度提高了液化率;对于扩张段长度固定的喷管,过大膨胀率将导致气体温度或压力低于三相点而无法液化;不同膨胀率及不同入口条件下液化率均较低,需进一步开展多级液化研究。

Few studies have been conducted on the natural gas condensation and liquefaction process within supersonic cyclone separator. The natural gas condensation and liquefaction process within the Laval nozzle is researched by numerical simulation and the effect of the nozzle structure on the condensation liquefaction is analyzed. The results show that the methane gas condenses spontaneously in the nozzle. But the condensation shock waves phenomenon is not obviously, which is a result of the slow droplet growth and little latent heat of condensa- tion during methane gas condensation process. With the nozzle expansion rate increases, the gas undercooling increment becomes larger, and the gas will reach its condensation liquefaction conditions （ Wilson point） sooner. The maximum nucleation rate, the number of droplets and humidity （liquefaction rate） within the nozzle increases with the increase of expansion rate. When the expansion rate increase from 6 000 s^-1 to 12 000 s^-1, the maximum nucleation rate, the number of droplets and the nozzle outlet humidity will respectively increase 154. 8% , 79.5% and 51.7 % , thus greatly improving liquefaction rate. For the fixed length expansion nozzle, excessive expansion rate will make the gas temperature or pressure lower than the triple point, and unable to liquefy the gas. Lower liquefaction rate will be obtained under different expansion rate and inlet conditions, so that multi-stage liquefaction research need to be further studied.