Simulation And Optimization In Stirred Tank For High Viscosity Fluids

The flow of high viscosity material is very complex in the stirred tank, so it is difficult to be solved by the method of experiment. At present, the designing of stirred tank is depended on experience and experiment, and is leaking in support of experiment theories. Computational Fluid Dynamies(CFD) is used to analyze the flow charaeters of fiuid, which can not only save a lot of resource, but also get some important local data that can not be gathered in experiment. Now CFD is regarded more and more in the designing and optimization in chemical engineering fields.In this paper, the commercial software package FLUENT 6.3 was used with multiple reference frames(MRF) impeller rotation model. Fluid set up the establishment of a simplified model with GAMBIT ,and for high-viscosity materials hydro1yzed gelatin with double ribbon stirred tank was simulated. The result showed that the double ribbon impeller could simulate detailed information on distribution of velocity and through change s/d, find a suitable value of 1. The optimum stirring speed was somewhere near 60 r/min. The result was provided the theoretical basis for the design of the double ribbon impeller.But double ribbon stirred tank was a certain defect, so numerical simulation was carried out on other two kinds of agitators. The double ribbon stirred tank,screw-ribbon stirred tank and INTERMIG-ribbon stirred tank were compared and analysied. Their flow field, velocity field, mixing time and power consumption were simulated. Speed of INTERMIG-ribbon stirred tank near the axis was improved. Tracer spread of the INTERMIG-ribbon stirred tank was faster than the other two stirred tank, and Mixed better. Mixed death zone of the INTERMIG-ribbon stirred tank did not exist. Power consumption of the INTERMIG-ribbon stirred tank was lower than screw-ribbon stirred tank. In view of all these factors,it was found that INTERMIG-ribbon tank was more suitable for the simulation in the materials.At the same time, the INTERMIG-ribbon stirred tank viscosity scope of application is simulating, identify the best material to apply the range of viscosity was 2.3 Pa·s～52 Pa·s. Then enlarge INTERMIG-ribbon tank was simulated, and analysis its flow field, velocity field, the mixing time and power. Simulation shows that the increase in power with the speed increase was not linear, when the speed was reached to certain value, power increase with the speed of the trend was more quickly. Tracer in the stirred tank could be faster with better mixing. In view of all these factors, mixed was fast and effective the INTERMIG-ribbon stirred tank. Its power consumption was low and application was wide. So it was a successful stirred tank.