Research On Enhnced Oxygen Mass Transfer Process In A Higee Reactor

The oxidation processes are widely found in biochemical industries,such as enzymatic reactions and aerobic fermentation reactions.Air is generally used as an oxidant in the production of such processes.And it has the characteristics of wide source and convenient access,which can reduce production costs.Oxygen is a poorly soluble gas and the rate of oxidation is limited by oxygen mass transfer.Therefore,in order to improve production efficiency and oxygen utilization rate,it is an urgent question to strengthen the oxygen mass transfer process of aerobic biochemical reaction.In this work,combined with the advantages of Higee reactor and stirred reactor,an internal loop rotating bed reactor which is suitable for oxidation systems was developed to enhance the oxygen transfer process.The effects of filling fluid volume,rotating speed and ventilation capacity on the oxygen transfer coefficient(kLa)were investigated through water-air system firstly.And the structure of the rotating bed rotor and bubble diffuser were optimized to further improve the oxygen transfer performance of the reactor.Based on these,the internal loop rotating bed reactor was applied to the enzymatic synthesis of gluconic acid,in addition,the operating condition of enzymatic reaction and the parameters of rotating bed reactor were optimized.The feasibility and advantages of internal loop rotating bed reactor in biochemical reaction were explored.The results show that:(1)In water-air system,the optimum operating condition for the oxygen transfer performance of the internal loop rotating bed reactor are as follows:filling liquid V=4.4 L,rotating speed N=600 r·min-1,ventilation G=0.2 m3·h-1,at which time kLa is 0.01577 s-1.(2)In water-air system,when the diameter of the bubble diffuser is reduced from 3 mm to 1 mm,the oxygen mass transfer coefficient increases.The oxygen transfer coefficient of the reactor increases when the single-layered wire mesh is added to the rotor,and the hydrophobic wire mesh can further improve the oxygen mass transfer performance of the rotating bed.The oxygen transfer coefficient in the internal loop rotating bed reactor is 8 times that of the stirred reactor,under the same rotating speed,gas-liquid ratio and diameter of the bubble diffuser.(3)The concentration of glucose solution has little effect on its viscosity,and has little effect on the oxygen transfer coefficient in the system.When the concentration increases from 0 to 20%,the oxygen mass transfer coefficient keeps constant about 0.01600 s-1.The activity of glucose oxidase reaches the highest when the temperature of solution was 35℃ and pH=6.The addition of enzymes and gas flow rate had a significant effect on the reaction rate,however the effect of rotating speed was minor.Compared with the stirred reactor,the oxidation reaction rate of the internal loop rotating bed reactor was 15 times of that in the stirred reactor.