Study On Chaotic Mixing Intensification And Distribution Law Of Liquid-liquid In Mixer Settler

As a common extraction equipment,the mixer settler has the characteristics of simple structure and strong adaptability,while the problems of high energy consumption and low efficiency still exist in the traditional mixer settler.At the same time,the mixed isolation zone which seriously affects the mixing efficiency exists in the mixing chamber during the operation of the mixer settler.As an important part of the mixing chamber of the mixer settler,the impeller plays an important role in providing energy for the fluid mixing and strengthening the liquid-liquid two-phase chaotic mixing.The rationality of the design of the impeller is directly related to the production efficiency of the mixer settler.In this work,the mixing degree of liquid-liquid two-phase chaos mixing was effectively improved by introducing an elastic combination impeller into the mixer settler.Meanwhile,the structure of the flow field and the distribution of dispersed phase droplets also had a positive effect.Firstly,the chaotic characteristic parameters such as Lyapunov exponent(LLE)and multi-scale entropy(MSE)were obtained to indirectly reflect the chaotic mixing degree of the two phases in the mixing chamber.In the meantime,the mixing enhancement of the flow field in the elastic impeller system was studied.Secondly,the smart online particle analysis technology(SOPAT)was used to obtain the real-time distribution of droplets in the mixing chamber during the stirring process,and the particle size distribution of droplets in the dispersed phase was analyzed and studied.Finally,the difference of flow field structure and velocity field distribution in continuous phase was analyzed by particle image velocimetry(PIV)in different impeller systems.According to the experimental data,the following conclusions could be obtained:(1)The elastic combination impeller system could take advantage of the coupling effect between the spring and the rigid blades in the mixing process to provide shear force to the flow field.Meanwhile,the irregular stretching and bending movement of the spring in the mixing process also strengthened the chaotic mixing of liquid-liquid biphase in the mixing room.At the same stirring speed,the LLE of the elastic combination impeller system and the rigid-flexible impeller system increased by 18.3%～ 74.6% and 8.8% ～ 25.2% respectively compared with that of the rigid impeller system,and the LLE of the elastic combination impeller system increased by 10.5% ～ 26.6%compared with that of the rigid-flexible impeller system.(2)When the wire diameter and outer diameter of the spring are 0.6mm and 7mm respectively,and the length of the spring is 1.2 times of the pitch between the two impeller,the flow field chaos is strong.(3)The particle size distribution range of dispersed phase droplets in the mixing chamber under the system of elastic combination impeller system,the system of rigid-flexible impeller and the system of rigid impeller are respectively 15～ 450μm,15～500μm and 15～ 650μm,and the maximum peak sizes are respectively 190μm,260μm and 360μm.(4)Rigid impeller system presents three circulation flow field structure layout,and rigid-flexible combination impeller and elastic combination impeller as a result of the existence of flexible plate and a spring,increase the mixing chamber flow of central place affected by the stress,thus forming the columnar high-speed flow area near wall,flow field are binary structure,reduce the surface area of the flow field in the mixed area.In summary,The elastic combination impeller system can enhance the chaotic mixing of liquid and liquid in the mixing chamber,increase the number of droplets in the dispersed phase,reduce the particle size of droplets in the dispersed phase,and optimize the flow field structure.