Study On Flow Characteristics And Oxygen Dissolving Property Of Stirred Tank Bioreactor With Perturbed-Bladed Turbines

Stirred bioreactor is an important bioreactor, the stirring system serving as its core component. Over a long period of time, researchers conducted thorough investigations on the performance of six-flat-blade turbine impeller and applied it to industrial production. In recent years, researchers began to pay attention to the development of new agitators, but no researchers have conducted gas-liquid agitation investigations by applying perturbed turbine impeller to bioreactor.In this paper, the author takes the pictures of the gas-liquid stirring process using the high-speed photography, and intuitively compares bubble sizes and distribution patterns in the case of using different agitators by analyzing the light and dark portions of the pictures. The intuitive analysis of the pictures shows that compared to standard six-flat-blade turbine impeller, bubbles present a more even distribution in stirring tank when using perturbed turbine impeller. Matlab is used to develop a program to recognize these pictures so as to obtain the sizes of the bubbles in the stirring tank. The analysis result indicates that compared to standard Rushton turbine impeller, the bubbles produced by perturbed turbine impeller have a more centralized size probability distribution and a smaller average size.In this paper, the Euler-Euler two-fluid model, the multi-reference frame and the standard k-ε equation are employed to conduct numerical simulation of the gas-liquid agitating process occurring in the stirring tank when using perturbed turbine impeller and Rushton turbine impeller respectively. The comparison between the simulation data of flow field in the agitator tank and the PIV experiment result and between the stirring power simulation value and the experiment test result proves that the simulation result is basically valid. The comparison of the simulation data such as flow field, gas holdup, turbulence energy, and shear force from different agitators indicates that perturbed turbine impeller is apparently advantageous.On the basis of the data simulation, the author also carries out the experiment intended to measure oxygen transfer coefficient using the sodium sulfite method and the activated sludge culture experiment. The former experiment indicates that compared to standard Rushton turbine impeller, perturbed turbine impeller shows a better gas-liquid-agitation dissolved oxygen capacity. The latter experiment indicates that bioreactor provided with perturbed turbine impeller shows a better oxygen dispersity under actual working conditions.The research findings in this paper can be helpful for further researches and industrial optimization of agitating bioreactor.