Numerical Simulation For Gas-liquid Separator Distribution Characteristics In LNG Systems In Rolling Conditions

With the increasingly of natural gas consumption in China,the exploitation of land natural gas has been unable to meet the demand,and offshore gas resources have become an important source of energy to ease energy pressure.As a key equipment of phase separation in the offshore gas liquefaction process,the liquid refrigerant separated from the separator provides cooling for heat exchanger,and gas phase provides refrigerant for the subsequent process.Gravity separators are used in offshore platforms and floating tankers with its simple structure and easy to large.Its separation efficiency effects on the performance of the heat exchanger and even a great impact on the liquefaction system,so it is necessary to study the separation characteristics of the separator.In this paper,FLUENT software is used to simulate the gravity gas-liquid separator.First,this paper describes the numerical calculation method of FLUENT software.Second,simplify the model of the gravity separator for numerical simulation,divide the grid and perform grid-independent validation.Finally,the calculation model,boundary condition and so on needed for numerical simulation are selected,and the separation efficiency is taken as the evaluation index of the separation characteristics of the separator.We mainly study the effect of sloshing conditions on the separation characteristics in this paper.In real sea conditions,the main factors affecting the sloshing includes roll,pitch and heave,and it is simplified as roll and heave according to the symmetry of the separator structure.The change of the gas outlet liquid flow and separation efficiency of the gravity separator under different amplitude and period conditions is studied respectively,aiming at the two kinds of sloshing conditions.It is found that the liquid flow rate and separation efficiency of the separator are sinusoidal changes with time,and the sloshing condition reduces the separation efficiency: The larger the amplitude,the more violent the flow,the worse the separation effect of the separator on the two-phase flow.In the offshore gas liquefaction process,operating parameters are different with different stages of mixed refrigerant composition.The difference between the size of the associated equipment and the operating conditions results in a change in the structural parameters of the separator.The effects of different refrigerant flow,dryness,separator diameter,height,inlet and outlet diameter on the separation effect were studied respectively under the same sloshing conditions.The results show that different operation and structural parameters have different influence on the separation characteristics.Finally,the structure of the separator is improved according to the results of sloshing parameters,operating parameters and structural parameters.The separation characteristics of baffle,porous clapboard combined box and the two together are studied respectively.The results show that the separation efficiency decreases with the increase of the angle of the baffle.The porous separator has obvious effect on the stable flow field,and the separation efficiency decreases with the increase of the porosity of the box.Under the joint action,the separator performance has improved significantly.