Computational Fluid Dynamics Simulation Of Stirred Tank Reactor

Stirred equipment is widely used in chemical, food, metallurgy, paper making, oil and water treating industry, especially in chemical industry, stirred tank reactor is one of the most widely used reactor in the production of chemical industry. Although there are lots of theoretical and experimental study, the study of mixing and design methods are not developed well up to now. The semiempirical methods are still the main tools for design and scale-up industry processes. To meet the purpose for optimal design, scale-up and fully understand the processes occurring in stirred tank reactor, there are needs for abundant experimental measurements and mathematical models to measure and describe the characteristics of flow in such reactors. Recently years, Computational Fluid Dynamics(CFD) is used in the study of flow and mixing characteristics in stirred tank reactor, it can save much time and resource, it shows great advantage ,it will have great influence in the study, exploitation and design of the stirred tank reactor.In this study, based on the function provided by the commercial CFD software (Fluent), three-dimensional flow fields are carefully studied. It is found that the results of flow field using standard k-εturbulent model are in good agreement with the fact; the liquid arround the impeller is radial,according to this, the gas-liquid flow treated by the turbine stieeer can get well effect; two liquid rings are distributed around the stirred impeller, but the velocity magnitude is smaller than the data of experiment. Through the simulation of the turbulent, it is found that the distribution of the turbulent kinetic energy is the same with the turbulent intensity, most of the turbulent kinetic energy is concentrated in the field of impeller, 80 percent of the turbulent dissipation ratio is in the field of impeller and it's trail flow. The gas-liquid flow in the stirred tank reactor was simulated too. Two liquid rings are also distributed around the stirred impeller, but the liquid ring above the stirred impeller is bigger because of the gas's existence; the distribution of the gas are well appeared, radial distribution is good ,we can see that the turbine stirrer is proper to treat the gas-liquid reaction,it has longer stick time; most of the turbulent kinetic energy is in the field of stirrer and the gas inlet.Through the simulation of the double deck stirred tank, it is found that around the gradient impeller, there is only one liquid ring, it is well accord with the fact; compare the mixing time in the two kind of double deck stirred tank, we can found that the axial mixing situation in the double combined stirred tank is better than the double turbine stirred tank with all other's condition same,it gives a better combine pattern of stirrer to the big H/D gas-liquid reactor.