Numerical Simulation And Design Optimization On A Supersonic Natural Gas Cyclone Dewatering Device

The natural gas extracted directly from the wellhead contains large amounts of water and heavy hydrocarbons.These substances are liable to condense during transportation,which will not only reduce the transportation capacity of the whole pipeline,but also cause corrosion of equipment.So dehydration treatment of natural gas is necessary.On the basis of overcoming the shortcomings of the traditional dehydration method,a new supersonic cyclone dewatering technology is generated.According to the kinetic and thermodynamic principles,it combines the expansion and condensation with the cyclone separation,realizing the separation of water vapor and heavy hydrocarbons from natural gas.With the advantages of high efficiency,simple process,long-term reliability,green environmental protection et al,the application prospect of this technology is broad.In this paper,the design method of each component of dewatering device was put forward,and the detailed design calculation was carried out in the actual conditions and temperament conditions.Then the corresponding three-dimensional numerical calculation model was established accordingly.The flow characteristics,condensation characteristics and separation characteristics of natural gas in the supersonic cyclone dewatering device were studied by using ANSYS14.0 software.The results showed that the Mach number could reach 2 at a low temperature of 165 K and the tangential velocity was 60m/s,which could realize fully water vapor condensation and separation.There were three kinds of motion trace of the small droplets formed by water vapor.Their average diameter was 2?m,and most of them could be separated.The location of the shock was located in the diffuser behind the discharge port,facilitating temperature recovery and pressure recovery without destroying the condensing environment.On the basis of the study of the internal flow field,took the separation temperature,separation efficiency,the tangential velocity and shock position as optimization indicators to study the influence of different structure parameters to determine the final structure size.Finally,the normal operating range and the variable working conditions of the dewatering device were analyzed.The results showed that the influences of different structural changes on the optimization indexes were different,and the optimal structure should be determined according to the actual situation.Normal pressure loss ratio range of dewatering device was 35% to 70%.The maximum dew point could be reduced to 23 K when the inlet pressure was 4MPa,the temperature was 300 K and the pressure loss ratio was 70%.The dewatering device can also obtain the ideal dew point drop by changing the inlet and outlet pressure and temperature.It can be seen that the designed supersonic cyclone dewatering device has a good adaptability to the pressure and temperature changes,which can meet the domestic gas field engineering applications.