| Aeration biochemistry is the process of using aerobic bacteria in activated sludge to engulf and degrade organic pollutants in sewage to achieve sewage purification treatment,which is the core link of sewage treatment process.Controlling the smooth operation of the aeration fan to ensure the stable air supply pressure is a necessary condition for improving the content of dissolved oxygen in the pool water,meeting the oxygen required by aerobic microorganisms,and fully mixing and contacting the activated sludge and sewage,so as to realize the efficient and stable production of the aeration biochemical process.Taking the SBR(sequential batch activated sludge method)aeration fan control system of Songyuan Sewage Plant in Jilin Province as the research background,in order to overcome and reduce the interference and impact caused by the cycle switching process of the aeration tank and the change of external environmental factors on the stable operation of the fan,this thesis deeply studies and analyzes the surge phenomenon and basic principle of the fan,proposes to combine the fixed limit and variable limit method,calculate and set the anti-surge limit according to the different speed range of the fan for anti-surge control,and combine the adaptive fuzzy PID control algorithm.To further improve the stability of the aeration fan operation,the aeration fan control system program is designed based on the Siemens S7-400 PLC platform.Specific research contents includes the following aspects:(1)The operation process of the aeration fan,the role and process flow of the aeration link of the sewage plant and the main control content were introduced;The surge and anti-surge control of the aeration fan system were studied,the working principle of the fan system,the load characteristics of the pipe network and the common anti-surge control methods of the aeration fan system were analyzed,the system anti-surge line was established,and the anti-surge control scheme of the aeration fan system was proposed.(2)The control system program and man-machine interface are designed,and the process flow description and program design analysis are carried out for the main control loop.Aiming at the problems of the anti-surge PID control algorithm of the aeration fan,the fuzzy control algorithm is used to improve it.Simulink in MATLAB software is used to compare and analyze the conventional control algorithm with the improved control algorithm.And by querying the fuzzy control table,the adaptive fuzzy PID algorithm is realized in PLC.The results of MATLAB simulation curve and PLC program simulation test show that the improved adaptive fuzzy PID control algorithm has achieved a good control effect on the aeration fan system,and has been improved in terms of overshot,response speed,adjustment time,etc.The actual measured value of the optimized fan inlet flow rate can be stable around the set value.The deviation fluctuation is significantly reduced,the overall anti-interference ability of the system is improved,the phenomenon of fan surge is effectively avoided,the stability of air supply pressure is ensured,and the efficiency of sewage treatment is improved. |
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