| As a new solvent,ionic liquids show significant advantages in reaction and separation fields for its unique characteristics.It is necessary to study the flow and transfer characteristics in order to achieve the industrialization of ionic liquids.It is found that the pure ionic liquids have high viscosity,which can lead to lower mass transfer efficiency.As a viscosity reduction measure,adding a small amount of water in the ionic liquid can greatly reduce the viscosity and improve the mass transfer efficiency.In addition,it is difficult to reach water-free during the synthesis and use process of ionic liquids.Therefore,it is very necessary to carry out research on ionic liquids with trace amounts of water.In this context,methods of experiments and computational fluid dynamics(CFD)simulations were used to study the single bubble and multi-bubble behaviors in aqueous ionic liquids.The main research contents and results are as follows:(1)The bubble behaviors in aqueous ionic liquids were studied by experimental.The bubble shape,size and distribution in aqueous ionic liquids were investigated through high-speed camera technology.The gas holdup was calculated by bed expansion method,and the influence of the gas velocity and water content on gas holdup were investigated.It is found that the behaviors of bubbles in ionic liquids are very different from that in water.Water content has a great influence on the bubble behaviors in ionic liquids.With the decrease of water content in ionic liquids,the gas holdup and the bubble diameter increase,and the distribution of bubbles become broader.(2)The single-bubble behaviors in aqueous ionic liquid were studied by simulation.The VOF method were used to track the gas-liquid interface.The influences of water content on the bubble deformation and motion velocity were investigated.The simulation results were validated based on the experimental data in the literature.The velocity field and pressure field around the bubble were measured to analysis the causes of bubble motion and deformation.The study found that with the increase of water content in ionic liquids,the bubble deformation and the bubble velocity increase.The study of single bubble behaviors in aqueous ionic liquid can be a foundation for the study of multi-bubble and can provide a basis for the reactor design.(3)The multi-bubble behaviors in aqueous ionic liquid were studied by simulation.A CFD-PBM model was established to study the bubble distribution.A FCCS model was used to predict the physical property of the mixture of water and ionic liquids,the accuracy of the model was verified by the experimental results and compared with the single bubble model,the CFD-PBM model is more consistent with experimental results.The effects of water content and gas velocity on the gas holdup,velocity field,and the size and distribution of bubbles were investigated.The results of simulation found that with the increase of water content,the gas holdup decrease,with the decrease of water content and gas velocity the gas holdup and liquid velocity in radial distribution are more symmetrical. |
