Numerical Model Analysis And Optimization Of Gas-Solid Two-Phase Flow In Cyclone Separator

As a centrifugal device for separating a gas-solid,cyclone separators have been widely used in industrial systems such as pharmaceutical industry,petroleum industry,and coal-fired power generation.In the ethylene cracking unit,the cyclone separator is placed at the outlet of the quenching oil pump to separate the impurities(such as powder)from the oil,so that the quality of the product can be further improved.In this paper,a CFD mathematical model is established to calculate the gas-solid two-phase flow in the cyclone separator of the ethylene cracker,from wich the internal flow law can be understood deeply and comprehensively.Structural optimization provides a basis for a good combination of simulation and industrial applications.Firstly,the fluid dynamics characteristics of the gas phase in the cyclone separator were studied by using the Reynolds stress model.The velocity distribution and pressure distribution of the gas phase were analyzed.The results show that:(1)the tangential velocity and axial velocity of the cyclone separator calculated by the RSM model agree well with the experimental values;(2)A good symmetry of airflow can be seen in the cylindrical section,but after entering the cone region,the symmetry of is destroyed by the secondary eddy current.However,the airflow vector entering the exhaust pipe still has better symmetry and is not affected by the airflow of the intake pipe under a strong swirl field;(3)the maximum total pressure of cyclone separator appears at the inlet of intake pipe.And the total pressure presents a decreasing trend from cylinder to cone.Secondly,the random orbit model is used to study the particle motion and separation characteristics in the cyclone separator.The effects of the diameter of the exhaust pipe,the insertion depth and the length of the cylinder column on the separation performance are investigated.The results show that:(1)large size particles are subjected to stronger centrifugal force;(2)a large amount of particles are escaped from exhaust pipe and the escaped particles will be reduced when the particle size is increased to 6μm.The particles are substantially completely captured when the particle size is increased to 15 μm;(3)the separation efficiency is the highest when De = 72 mm and HC=335mm,respectively.And the separation efficiency and pressure drop of the cyclone will increase with the insertion depth of the exhaust pipe.