Numerical Simulation Study On Optimization Of Ventilation Arrangement In Aeration Tank

With the increase of population and the acceleration of urbanization in China,the situation of water resources will be more studied.However,due to the unbalanced distribution of resources on the earth,excessive demand for resources produces a considerable social burden,which is the primary problem that we must face and solve in order to improve our living standards and quality.With General Secretary Xi's elaboration on the construction of ecological civilization at the 19th National Congress,we have to face various problems,such as resource constraints,environmental pollution and degradation of ecosystem self-repair.Because the treatment of sewage is imminent,this paper analyses the commonly used activated sludge treatment methods.The aeration tank reactor in sewage treatment plant was selected as the model,and different flow field parameters and different cross-section values were compared.Determine the influence law of different ventilation hole layout,and select the appropriate ventilation hole layout.In this paper,the model of oxidation ditch process is established by using Fluent software,and the hydraulics characteristics of oxidation ditch are simulated.The main conclusions are as follows:(1)Gas-liquid two-phase flow model is established for different grid partitioning modes of aeration tank.RNG k-e model is used for turbulence model,Euler model for multiphase flow model and velocity inlet for ventilation hole.The section diagram of aeration pipe of aeration tank model is extracted,and the streamline vector diagram is analyzed.Comparing with the measured phenomena,the results show that the flow field in the tank can be simulated better by choosing the grid generation method.In model validation 2,numerical simulation of inverted umbrella aeration tank is carried out.The characteristic section is selected to analyze and predict the flow field in the aeration tank,and the DO in the plane of the statistical section is compared with the experimental data.Verify that the solution model can correctly simulate the gas-liquid two-phase flow in the aeration tank.(2)Simplified aeration pipe was used to simulate the layout of ventilation holes.The analysis of streamlines and vectors showed that the recirculation of streamlines at the multi-phase interface of mixed liquid streamlines in cross-section resulted in unstable flow pattern in the pool,and there were more irregular vector arrows in the middle of cross-section(3)By analyzing the cross-sectional non-uniformity coefficient and vertical velocity of different ventilation holes,it can be found that changing the orientation of the ventilation holes strengthens the vertical velocity of the middle area or both sides of the aeration pipe in varying degrees,but also leads to large difference between different sections and unfavorable mixing When the non-uniformity coefficient is upward,the velocity of each section in the aeration tank is uniform,and there is a stable circulation loop.It is beneficial to air-active blending(4)As the internal factor of aeration effect of aeration pipe in direct reaction aeration tank,air content is also the key reference standard for comparing different aeration pipe arrangement The surface average void fraction values of different cross sections are counted and the void fraction distribution curve is drawn.We can intuitively draw the conclusion that the air void fraction value is higher in many characteristic sections when the air vent is upward,so we choose the optimal arrangement of the air vent.