| During the wastewater treatment process,aeration energy accounts for more than 50%of total operating energy.In recent years,with China's requirements for the upgrading of wastewater treatment plants and the increasing energy of wastewater treatment,the selection of aeration devices and the adjustment of working conditions have important roles in saving energy.Studying the aeration system and applying it to the optimization of process operation can achieve the purpose of energy saving.The thesis includes three parts:First,the experiments of oxygen transfer efficiency under different working conditions was made,and the influence of different working conditions on the oxygen transfer efficiency according to the various factors was analyzed.Then the gas-liquid two-phase numerical simulation was done.On the basis of the experiment,the FLUENT software was used to establish the mathematical model as same as the experimental conditions,the gas-liquid two-phase hydraulic characteristics of the aeration process was simulated,and the influence of hydraulic parameters in the oxygen transfer process was analyzed;Finally,based on ASM2d coupled with aeration control,the simulation and optimization of the anaerobic-oxic multilevel anoxic-oxic process were researched,the process model was established by using WEST software,and energy saving was achieved through the optimization adjustment of aeration control.The main conclusions are as follows:(1)The results of oxygen transfer efficiency in the aeration tank show that:1)when the volume of aeration changes in a certain range,Kla(20)and SOTR increase linearly with the increasing volume of aeration,SOTE decreases with the increasing volume of aeration;Ep decreases with the increasing volume of aeration.2)when the depth of aeration changes in a certain range,Kla(20)increases slightly with the increasing depth of aeration,SOTR and SOTE increase linearly with the increasing depth of aeration;3)Under the same volume of aeration,EP increases with the increasing depth of aeration.The increase of SOTE plays a major role in the change of Ep.These indicate that the energy loss of the lo w depth of aetation is more obvious in the projects;4)The experiment of bubbles movement during the aeration process by using a high-speed camera shows:The distribution of bubbles is uniform when the volume of aeration changes in the 0.75?1.00 m3/h range.The oxygen utilization rate dereases when the volume of aeration is 1.25 m3/h.(2)The results of the numerical simulation of gas-liquid two-phase show that:1)the volume of aeration changes in the 0.50?1.25 m3/h range,the distribution range of the two-phase velocity fields increases with the increase of the volume of aeration,and the range of the slowing zones decrease.When the volume of aeration is 1.00 m3/h,the distribution of velocity fields and flow regime are the best.The average gas volume fraction increases with the increase of the volume of aeration.When the volume of aeration is 1.00 m3/h,the gas distribution is most uniform.When the volume of aeration is between 1.00?1.25 m3/h,the gas-liquid two-phase mixture better.When the volume of aeration is 1.00 m3/h,the aeration devices are most efficient;2)When the height-diameter ratio is between 1.0?2.0,the distribution of velocity fields gradually stabilizes with the height-diameter ratio increases,and the range of the slowing zones increase.As the height-diameter ratio increases,the gas-liquid two-phase mixing speed increases.When the height-diameter ratio is 1.5,the velocity fields is stable and the turbulent kinetic energy is appropriate,which is conducive to oxygen transfer.(3)The result of the simulation and the optimization of the anaerobic-oxic multilevel anoxic-oxic process based on ASM2d coupling aeration control show that:1)When the dissolved oxygen concentration is between 1?4 mg/L,the dissolved oxygen concentration has little effect on the effluent COD concentration and the effluent TP concentration.The effluent NH3-N concentration decreases with the increase of the dissolved oxygen concentration,and the rate of decrease is faster when the dissolved oxygen concentration is between 1?2 mg/L,and the TN concentration of the effluent increases with the increase of the dissolved oxygen concentration.2)Adjust the aeration intensity by establishing an aeration control model.In the premise that the water quality meets the standard,the average daily electric energy after optimization is reduced by 8.08%than before. |
PDF Full Text Request