Intensification Of Oxygen Mass Transfer Performance In A Rotating Bar Reactor

Biocatalysis technology uses enzymes or cells as catalysts for chemical conversion,which is one of the key technologies to achieve green and sustainable development of chemical industry.Oxidation reaction is an important type of biocatalytic reaction,and there is a problem that oxygen transfer rate does not match the oxygen uptake rate.In industry,the dissolved oxygen in the reactor is generally improved by increasing the stirring speed,but there is a problem that the shear force can damage the enzymes or cells in the system.As a novel type of biochemical equipment,rotating bar reactor(RBR)has the advantages of small shear force,high heat transfer coefficient and excellent mixing performance.This work focuses on the RBR through structural innovation research to further enhance its oxygen mass transfer enhancement effect.In this work,the influences of rotational speed,gas flow rate and liquid flow rate on the oxygen mass transfer coefficient of the RBR were investigated by water-air system and bubble behavior was observed by high-speed camera.It was proposed that the bottom and the inner shaft of the RBR were respectively set up gas distributing tray and disturbing device to improve gas dispersion and liquid disturbance.By comparing and analyzing the oxygen mass transfer coefficient,average bubble diameter and bubble rise velocity,the optimal structure of the RBR was determined.On this basis,catalyzed oxidation of glucose to produce sodium gluconate was adopted as the working system to study the influence of technological parameters on the yield of sodium gluconate.The main findings are as follows:1.The oxygen mass transfer coefficient of the RBR increased firstly and then decreased with the increase of the rotational speed and the liquid flow rate.The oxygen mass transfer coefficient of the RBR increased with the increase of the gas flow rate.The process conditions with excellent oxygen mass transfer coefficient were as follows:rotational speed N=500 rpm,gas flow rate QG=40 L/h,liquid flow rate QL=20 L/h.2 The addition of gas distributing tray at the bottom of the RBR could effectively break the bubbles,reduced the size of the bubbles,and then enhanced the mass transfer performance;The addition of disturbing device to the inner shaft of the RBR could not only disturb the flowing liquid,but also redisperse the bubbles.When the bore diameter of the gas distributing tray was 2 mm and the number of turbulence column was 19,the maximum oxygen mass transfer coefficient was about 0.0156 s-1.3.The concentration of glucose solution prepared in the experiment had almost no effect on viscosity of glucose solution and had little effect on the oxygen mass transfer coefficient of the RBR;At the temperature of 36℃ and the pH value of 6,the catalytic activity of glucose oxidase was the highest;The increase of GOD additive amount,rotational speed,gas flow rate and liquid flow rate promoted the formation of sodium gluconate.Compared with the report in the literature,the average productive rate of sodium gluconate in the RBR was about 4 times that in the stirred tank reactor.