Analysis On Flow Field And Structural Optimization Of Fermentation Stirred Tank

This paper is a part of the research project: Extraction of High Concentration Fermentation Liquid and Clean Production Technologies of Glutamate, supported by State 863 Project (No.2006AA020303-02).The flow field distribution and power consumption are two important parameters for investigating the performance of stirred tank. Based on the prototype of an actual fermentation stirred tank, this paper carried out the flow field analysis and structural optimization by using numerical simulations. The main researches and conclusions are as follows:(1) According to the analysis and compare between the stirred tank with and without draft-tube through the simulation of flow field, find that under the cooperation of impellers and draft-tube, the flow in the axial direction has been reinforced, and the mixture effect of fluids arranging in the upper layer and lower layer respectively has been improved evidently. At the same time, the liquid near the impeller no longer rotate along with the impeller. As a result, the power consumption of mixture has been declined by 12% compared with the situation without a draft-tube, and the flow field in the tank has become an ideal one.(2) After the analysis of many groups of structures by choosing structure parameters, there are some satisfied combinations among them, In these conditions, the flow field in the tank has been a ideal one that flows in a inerratic way.(3) The researches about the influence of impeller rotating in different speed and the difference in power consumption have been conducted. According to our conclusion, the increase of the rotate speed of impeller incline to little change in the flowing pattern of the fluids in the tank. However, the power consumption will triple if doubling the rotating speed of impeller.(4) Compared with single-paddle stirred tank, the power consumption of dual-paddle stirred tank increases as mush as 170%, but a better flow field distribution comes out, with larger effective mixed area. In addition, After researching the difference of the flow filed owing to different distance between two paddles of the dual-paddle stirred tank, the results show that: an appropriate increase in the distance is conducive to improve the mixing effect and lower power consumption.And the simulation results are more in line with the experimental results.The conclusions of this paper are useful for structure optimal design of industrial stirred tank.