Design And Simulation Of Dissolved Oxygen Margin Control Parameters In Fermentation System

Microbial fermentation technology has become the focus of current research as the increasing demand for new products such as human insulin,antibodies and various enzyme preparations in recent years.Dissolved oxygen is an important parameter in biological fermentation system,the yield and quality of fermentation products can be guaranteed if appropriate dissolved oxygen margin can be maintained in the process of biological fermentation.It is proved that the dissolved oxygen is related to the rotor speed,species,installation height and gas distributor in the biological fermentation system.The dissolved oxygen can be controlled by studying the influence of these factors on the characteristics of gas-liquid dispersion and gas holdup in the internal flow field of the biological fermentation tank.Using Computational Fluid Dynamics(CFD)to numerical simulation the flow field in the fermentation tank.The 3D modeling of biological fermentation system is created by SolidWorks 2014 including tank,baffle,paddle and gas distributor and so on,then import it into workbench 19.0 for preprocessing.An Euler-Euler two-fluid flow model is chosen in FLUENT numerical simulation while setting water to liquid phase and air to gaseous phase,and selecting the standard k-ε model as turbulence model.There are conditions of four groups of blade speed,three groups of blade installation position,three groups of minute volume for comparative study.The characteristics of local gas holdup and power variation before and after ventilation are analyzed,the results show that the overall gas-liquid dispersion effect is the best,the flow field inside the fermentation tank is most evenly mixed while the blade rotation speed is 400 rpm,the gas throughput is 184.23 L/min and the lower blade mounting height is 0.2 m when the space between the double blade is 0.5 m.And the RPD is 0.80,the power decreases by 20.3% after ventilation under this working condition.The results of numerical simulation are reasonable and can provide some references for further design and optimization of biological fermentation system.