| Activated sludge treatment is one of the most widely used methods in the wastewater treatment field at present. The gas-liquid transfer efficiency in the aeration tank, which is the key reactor of the activated sludge treatment system, has immediate relations with the cost and efficiency of the wastewater treatment. Based on the achievements of other scholars and CFD software, this paper aimed at simulating gas-liquid flow field. Thus it can provided theoretical basis for the rational designing, accessing, and controlling of the aeration tank operation. We choose an aeration tower in a deer factory to be the research object. Numerical simulation of gas-liquid flow field has been finished using k ?εmodel and Eulerian multiphase model. We find that the calculated results accord with the theoretical analysis and show that numerical simulation can display the state of gas-liquid field fully. These prove that numerical simulation is a powerful tool for the design of aeration tank.The paper analyzes the effect of gas-liquid transfer and gas holdup on the flow of various operating parameters; the results give a theoretical criterion for how to optimize the design of aeration tank.Otherwise, some ideas about how to optimize the structure are be suggested and have been simulated. We find that circumfluence will accelerate gas-liquid transfer, if a draft-tube has been added to the aeration tower. In addition, the paper also analyzes the effect of gas-liquid transfer on various structure parameters of the draft-tube, the results give us some useful reference for how to select the structure of draft-tube to obtain higher gas-liquid transfer rate.At last, the paper analyses the application of a new convergence-divergence draft-tube to aeration tank. k ?εmodel and Eulerian multiphase model is used to simulate the gas-liquid fluid with different structure parameters of the convergence-divergence draft-tube, and the results shows that aeration tower and convergence-divergence draft-tube can combined to be a new kind of wastewater treatment. Because of convergence-divergence structure, stream of flow in the tower will be more disorganized and the use of dissolved oxygen also will be... |
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