Study On Hydrodynamic Characteristics In An Agitated Sieve Plate Extraction Column

The extraction column is an important type of separation equipment that has wide applications in chemical industry.The agitated sieve plate extraction column is composed of alternating agitating sections and settling sections,the adjacent sections are separated by a sieve plate,which can reduce back mixing and improve separation efficiency.Flooding characteristics and drop size in the extraction column are both critical hydrodynamic characteristics,which reflecting flow situation and influencing the treatment capacity and adaptability of the column.The research on hydrodynamic characteristics in extraction column is the premise and foundation for the application.The flooding characteristics were studied in an agitated sieve plate extraction column in this dissertation.It is found that under different flow rate,rotor speed and physical properties,different flooding phenomena such as aggregation,phase inversion,overflow,emulsification and entrainment will occur in the extraction column.In terms of flow rate and rotor speed,different operation areas are divided.It is found that the flooding characteristics of different systems are quite different.System with low interfacial tension is easy to disperse,the rotor speed in the operation area is low,system with high interfacial tension is hard to pass through the mesh,the rotor speed in the operation area is high,system with high density difference is easy to convection,thus not prone to flood,system with high viscosity is hard to perform momentum transfer,so prone to flood.In addition,the introduction of organic solute will reduce the interfacial tension and make the flooding curve move to the low rotor speed region.The drop size were studied in the agitated sieve plate extraction column in this dissertation.It is found that the lognormal distribution model can describe the drop size distribution.The drop size decreases with the increase of rotor speed,and increases with the increase of two-phase flow rate.System with low interfacial tension is easy to disperse,the droplets are small,system with high density difference has low holdup,the droplets are also small,and system with high viscosity is hard to perform momentum transfer,so the droplets are larger.In addition,in the mass transfer systems,the two-phase flow rate will affect the interfacial tension of the system by affecting the solute concentration,and then change the drop size.Based on the experiments in the agitated sieve plate extraction column under mass transfer,a correlation for estimating the average drop size is proposed.The maximum deviation between the calculated values and the experimental values is-16.1%,and the average deviation is 5.6%.