| The Low Temperature Separator(LTS)is a key equipment for the purification system of natural gas exported from underground gas storage.It is mainly used to remove the liquid impurities carried in high-pressure natural gas to reduce its dew point,so as to meet the gas quality requirements of long-distance transportation pipelines in China.As the core component of LTS,the existing vane-type separation element(VSE)has a narrow scope of application conditions and is easy to cause the secondary entrainment when the inlet gas velocity is relatively high,which leads to the decline of separation performance for the equipment.In order to solve this problem,two methods to optimize the gas-liquid separation performance of VSE are proposed from the aspects of structure optimization and surface modification.Furthermore,the reasons for significant reduction of separation efficiency under high pressure are discussed.The research results are intended to provide theoretical guidance and new ideas for the performance optimization of VSE.Aiming at the low separation efficiency of VSE,a novel type of VSE with grooves as the reinforcement structure is proposed in this dissertation.With the throttling effect of grooves,the inertial force exerted on the tiny droplets is significantly enhanced due to the acceleration of airflow.When the air inlet velocity is relatively high,the grooves can also suppress the secondary entrainment by blocking the movement of liquid film on the wall.Therefore,its separation efficiency is more than 10.0% higher than that of the traditional folding-line-type VSE.Compared with the single-hook-type and doublepocket-type separation elements,the smaller pressure drop makes the quality factor much higher due to the fact that their separation efficiency is very close.Concerning the high possibility of secondary entrainment of VSE at high inlet gas velocity,the superhydrophobic/microchannel surfaces are prepared on the aluminum alloy surface by chemical etching and precision milling,to increase the hydrophobicity of the separated material,hence reducing the interfacial adhesion between the droplets and wall.The main reason for the improvement of separation efficiency is that the liquid film on the wall drains faster and the secondary entrainment decreases significantly because of the change of surface properties.When the inlet gas velocity is 6m/s,the separation efficiency of the hydrophobic separation element with microchannel is improved by 9.7% than the hydrophilic separation element,but the pressure drop does not change significantly.The separation performance of VSE under high pressure is investigated by numerical simulation.Compared with the ordinary pressure,the separation efficiency is obviously reduced at the operating pressure of 4～6 MPa and the pressure drop increases significantly.This is mainly because that significant increase in density of gas phase lead to the reduction of the inertial force exerted on the droplets,and the surface tension of liquid phase decrease gradually with the increase of operation pressure,so the liquid film on the wall is difficult to drain and the secondary entrainment is easy to occur.Based on the above simulation results,the separation performance prediction models are established by applying the response surface method(RSM)and multiple quadratic regression method,and an optimal structure is found accordingly,which can achieve efficient gasliquid separation at a low pressure drop.The above research results are intended to put forward new ideas for improving the separation performance of VSE,and guide the subsequent optimization design by establishing the prediction models for its separation performance,so as to meet the requirements of low resistance and high efficiency gasliquid separation under high-pressure conditions. |
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