The Study Of Stirring And Mixing Process In Crystallizer Based On CFD

Mixing and stirring process is one of the most important operation units in chemical engineering, medical and food industry. And mixing equipments have been widely used in many industrial processes. For the research methods of mixing process, experimental method have been replaced by computer simulation and experimental method. In recent years,the simulation method of computational fluid dynamics have been widely used in the mixing process study.The study of mixing process used Computational Fluid Dynamics method has been developed rapidly in recent years.In this paper, stirring and mixing process in crystallizer is simulated by using Computational Fluid Dynamics method which is verified with experimental and literature data. Simulation research is divided into the following aspects: firstly, the selection of the impeller types, whitch is based on the flow field generated by impeller in favor of particles suspension in crystallizer; secondly, the optimization of feeding locations, whitch is based on the mixing efficiency; thirdly, the selection of impeller position, whitch is based on the flow field, mixing efficiency, and uniformity of the crystal phase distribution; then the distribution of crystal phase under different crystal size and different impeller speed is simulated; finally, appropriate improvement is made in the shape of the crystallizer.Through the simulation results: the Hydrofoil Impeller is selected, because it can generate more favorable flow field for the suspension of crystal phase; for the double-flat impeller, the central feeding position is selected, because the mixing time at this position is the shortest, and mixing efficiency is the highest; when the tank height is 270mm, and the inner diameter of the tank is 190mm, the impeller span is 100mm, the flow field is much more better, mixing time is short, the uniformity of crystal phase is good, and the stirring power is not large; as the impeller speed increases, the distribution of crystal phase is more uniform, combined with the speed of stirring in the crystallization process should not be too large, the proposed selection of the stirring speed range is from 150rpm to 200rpm; with the increase in particle size of crystal phase, the distribution of crystal phase in the crystallizer is more and more worse, so the stirring speed is proposed to increase with the size of crystal phase grows in the whole crystallization process; by changing the round type bottom of the traditional crystallizer into the double circular-arc type bottom, the dead zone at the bottom of the crystallizer can be effectively eliminated, hence the double circular-arc type bottom of the crystallizer is proposed to be used in the industrial process. A combination of literature and experimental data are used to verify the simulation method in this paper. In order to verify the feasibility of CFD simulation, the simulation results were compared with the literature or experimental results, which provided the basis for the numerical study.