Study On Gas Hlod-up Fraction And Modei Of Three-pass Dividing Wall Column

Dividing Wall Column(DWC)is used for the separation of three components mixture,and equipment and energy consumption investment of DWC is lower than traditional distillation column by 30%.Three-pass Dividing Wall Column possesses the advantages of DWC and the following advantages:1)possess reasonable distribution of gas-liquid two phases contact area on tray,reduce the dead bubbling area,reduce the gradient of liquid level on tray;2)increase effectively the weir length,improve the capacity of the tray,increase production capacity;3)Three-pass Dividing Wall Column only need to add a rectangular downcomer on the basis of the traditional single weir tray for transformation.So,it is also very important that researching the liquid on the tray.Gas hold-up fraction on three-pass dividing wall tray was experimentally observed by using the electrical conductometry,The study was carried out within an air-water system in an organic glass column with 1200 mm in an inner diameter.The distribution of gas hold-up fraction above the tray floor was evaluated and discussed.Experimental results show that when the height from tray floor is less than 60mm,the average gas hold-up fraction of small bubbling area on the three-pass dividing wall tray is higher than that of big bubbling area.When the height from tray floor is more than 60mm,the average gas hold-up fraction of small bubbling area is lower than that of big bubbling area.On the plane whose height from tray floor is about 35mm(the lowest test height),the difference of uneven distribution of gas hold-up fraction on big bubbling area and small bubbling area is the maximum,and then becomes smaller with the increase of the height from tray floor,and finally tends to zero.On the plane whose height from tray floor is 125mm,the wall effect of the flat wall bubbling area is weaker than the curve wall bubbling area.The difference of uneven distribution of gas hold-up fraction on different bubbling area all tend to zero while the height from tray floor is more than 125mm.On the basis of predecessors' work,new average liquid hold-up fraction correlations were fitted through the experimental data to further improve the mathematical model which describes the interaction force between gas and liquid two-phase(drag model).Then,the CFD model of gas and liquid two-phase flow on the tray is established.We used UDF tools to program based on Fluent 6.3 software in order to solve the established mathematical model.Sieve Tray and Three-pass Dividing Wall Column were simulated by using a new mathematical model,and the results of simulation were compared with the experimental data.It shows that new mathematical model can describe the experimental data better than the mathematical model before,for the two different types of tray.Especially,the advantages are more apparent in the main contact area of gas and liquid two-phase.