Study On Flow Field And Structure Optimization Of Air-lift Loop Reactor With Multiple Draft Tubes

As a kind of important reactor in petrochemical field and water treatment,loop reactors have been studied for many years to acquire better gas-liquid distribution effect and mass transfer performance.In many kinds of loop reactors,loop reactors with low aspect ratio could reduce liquid level in large processing capacity,and reduce energy consumption further.So,loop reactors with low aspect ratio are chose to be studied by numerical simulation in the paper.During the research,some defects of the flow field have been found and the corresponding improvement approaches have been adopted.Firstly,after changing straight draft tube into sawtooth draft tube,the trend of fluid flowing to close the draft tube has been weakened.And the utilization of the inner space has been improved.Meantime,the lateral disturbance of flow get stronger first and get weaker then with the increase of the sawtooth height and the sawtooth number.Secondly,compared with the sawtooth draft tube,the reducing draft tube has more prominent effect.Because it could improve the liquid circulation velocity dramatically and enhance mass transfer.And above all,this kind of structure could be used on both straight draft tube and sawtooth draft tube to get further improvement.Thirdly,the conical draft tube,especial the two-stage conical draft tube,could not only possess all of the above advantages,but also have simpler structure to be manufactured easily.Fourthly,loop reactor with multiple coaxial draft tubes could get the flow pattern in order.Therefore,not only the flow pattern becomes more regular,but also the liquid circulation velocity becomes higher than before.Finally,bubble characteristics in the multi-stage air-lift reactor and all of the above loop reactors have been studied by the combination of population balance model and Eulerian-Eulerian two-fluid model.