Study On Hydrodynamics And Oxygen Mass Transfer Performance Of The Hemi-cambered Pitched Blade Turbines

The gas-liquid stirred reactor is widely used in chemical,metallurgy,biological,fermentation,food and other industries because of its simple operation and strong applicability.The oxygen mass transfer coefficient is the key parameter in the design of gas-liquid agitation reactor,especially for the industrial application of new stirrers.In this paper,a new type of hemi-cambered pitched blade turbine(HCP)was proposed.The experimental study of stirred tank was carried out in a pilot scale.The oxygen mass transfer and hydrodynamics performance were simulated by CFD,and optimized the structure of the HCP.First,the effects of gas distributor,stirring speed and gas flow rate on the oxygen mass transfer coefficient,stirring power and overall gas holdup were investigated.The results show that the overall gas holdup and oxygen mass transfer coefficient of the four structures(HCP1-0.5mm,HCP1-10 mm,HCP2-0.5mm,HCP2-10mm)increase with the increase of stirring speed and gas flow rate,and the stirring power increases with the increase of stirring speed,and decreases with the increase of gas flow rate.Combined with unit volume power and apparent gas velocity,the empirical formulas for oxygen mass transfer coefficient and gas holdup were established.Secondly,Eulerian-Eulerian multiphase flow model along with population balance model were used to study the HCP,and the overall gas holdup,the stirring power and the oxygen mass transfer coefficient were verified by the experiment results,which provided a reliable numerical simulation method for the HCP.The results show that the overall mean bubble diameter decreases as the stirring speed increases and the gas flow rate decreases.The overall mean bubble diameter of HCP1-0.5mm,HCP2-0.5mm and HCP2-10 mm decrease at the same conditions.Finally,the structure of HCP was further optimized by CFD simulation.The results show that the cutting mode and the projected area of the blade in vertical direction have important influence on the oxygen mass transfer efficiency.The oxygen mass transfer efficiency increases with the reduction of the projected area of the blade in the vertical direction under the same cutting mode.The impeller structure with the highest oxygen mass transfer efficiency was obtained: GEO6.