Study On The Technology Of Pre-Dehydration Of Supersonic Separators In Wen23 Gas Storage

Wen23 gas storage is a depleted gas reservoir with a wellhead pressure,high gas production,high temperature and so on.In the actual operation of the station there is a large loss of triethylene glycol,equipment construction difficulties and other issues.Therefore,in order to meet the development and application of gas storage,make full use of gas storage gas wellhead pressure and high temperature characteristics,the use of pre-drainage in the gas station pre-dehydration,in the collection station of triethylene glycol dehydration dehydration.The supersonic separator is a new technology in the field of natural gas dehydration.It has the advantages of high efficiency,compact structure and no hydrate.However,the design and use of supersonic separator in the high pressure station are less.So the high pressure of the actual site of the supersonic separator carried out the following research:Firstly,the design of the nozzle of the supersonic separator under high pressure was carried out with the existing basic data of Wen23 gas storage.For the tapered section of the nozzle,the Witoszynski curve,the Witoszynski displacement curve,the Bicubic curve and the Quintic curve are designed respectively.The tapered tube structure,the involute angle is designed with 2°,4°,6°,8°,respectively.Fluent software was used to simulate the flow field of nozzles with different structures.Considering the actual operating conditions in the field,the nozzle was designed with Witoszynski curve and 6° expansion angle.The use of the structure of the nozzle can be the earliest natural gas and heavy hydrocarbon condensation to provide low temperature environment,the best cooling effect,the nozzle outlet to obtain a more uniform flow field.Secondly,the vortex blades in the supersonic separator are designed.Since the position of the swirl vane of the rear type separator is closely related to the position of the aerodynamic shock wave,the position of the shock in the nozzle is calculated by using the continuity equation,with the simulation it is shown that the theoretical calculation is close to the numerical simulation results,and the calculation method has some reference value for the shock position in the nozzle.At the same time,keep the nozzle inlet parameters unchanged,the export back pressure is reduced,the shock wave position to the nozzle exit direction,the shock wave area width increases,the shock wave after the distribution of high turbulence,the outlet temperature is low,is not conducive to follow-up station field triethylene glycol dehydration,the nozzle pressure ratio should be controled.According to the location of the shock wave to determine the vortex blades,and the pre-type separator and post-type separator simulation was studied,the results show that the tangential velocity of the post-type separator is the largest,and the post-splitter is used to carry out the vortex.Thirdly,in order to calculate the dehydration efficiency and effective operating range of the supersonic separator,the water vapor condensation in the methane-water two-component in the nozzle was simulated and the relationship between the condensed shock and the position of the shock wave was studied.The results showed that:(1)The L-K actual gas mixing law is used to calculate the critical parameters and the molar specific heat of the mixed gas,which can be well consistent with the position of the condensed shock wave in the experimental results.(2)When the aerodynamic shock wave is far from the condensed shock wave,it has little effect on the condensation.When the aerodynamic shock wave approaches the condensed shock wave,even when the two shocks coincide,the condensation is greatly weakened.(3)Increasing the inlet pressure and reducing the inlet temperature of the nozzle can increase the radius of the condensate droplets,increase the liquid mass fraction and advance the condensing shock wave position,which is beneficial to the subsequent cyclone dewatering.In the early stage of the operation of the gas storage,the dewatering rate of the supersonic separator is higher in the case of high flow rate and high liquid content ratio.The back pressure of the outlet has little effect on the condensation shock position,nucleation rate and droplet number.(4)The design of the supersonic separator dehydration efficiency between 11%-51%,combined with the actual operating conditions,control pressure ratio of 68.75% or less,taking into account the natural gas still need to transport to the users,so the export back pressure is not low at 5MPa.Lastly,considering the fact that the supersonic separator is less practical in the field,this paper uses HYSYS software to simulate the whole dehydration process.The results show that the supersonic separator can adapt well to the pre-dehydration of the station,while the J-T valve can not.The change of temperature and pressure of natural gas has a great influence on the dehydration of later triethylene glycol,while the change of water content has little effect on water dew point.Considering the dehydration efficiency of triethylene glycol and the supersicer separator,the temperature of the supersonic separator is controlled at 35-45°C to ensure that the supersonic separator is in the effective operating range and reduce the effect on the subsequent dehydration of triethylene glycol.