Research On Chlorination Control System Of Water Plant

As the development of social economy, the security of drinking water attracts more and more attention across the nation, the water companies and downstream water plants call for higher water quality. Disinfection process of water treatment is one of the important parts, which is the last barrier to ensure the safety of drinking water, and currently chlorination is still widely used as the water plant’s disinfection process in the our nation. In this background, it is urgently needed to design and develop safe and reliable automatic control systems of based on the analysis of chlorine dosing section, and controlling the residual chlorine of the water plant’s treated water within safe and reasonable scope is of great practical significance.This thesis begins with the actual treating process, describes the processing sequence of water treatment, chlorination point, the choice of chlorine-containing medicines, and the chemical reaction mechanism of chlorination process. The control objective of residual chlorine, characteristics of chlorination process and factors effecting residual chlorine target is obtained based on process research. Then the thesis starts from conventional control method, introduces PID control and cascade control system of water chlorination system, especially focuses on the analysis of cascade control’s application in chlorination systems, which includes the selection of master control object and vice-control object, identification method of object model. Then with actual investigation, the thesis introduces the architecture of Mingshan water plant’s control system at Benxi. After analysis of chlorination system’s PLC control program, the closed-loop control metod of modifing the amount of chlorine coefficient by residual chlorine feedback factor is summed up. Becauae of long reaction time from the chlorination point to the cleanning water tank, chlorination system have a long delay time and the system’s accurate mathematical model is difficult to obtain, this thesis attempts to apply fuzzy control as intelligent control algorithm in chlorination control system. However, due to the fuzzy controller is almost equivalent to PD controller, which does not contain integral action, it is difficult to eliminate static bias. While using fuzzy control algorithm to optimize the conventional PID controller, the parameter’s tuning of which is not dependent on the object’s mathematical model and parameters can be adjusted online, real-time control requirements is fulfilled.Finally, through the Matlab simulation, compared with the traditional PID control, dynamic response, adaptive capacity and anti-jamming capability of the fuzzy controller and fuzzy PID controller is analysed. This design of fuzzy PID controller combines the advantages of fuzzy control and PID algorithm, a better control effect of residual chlorine can be achieved.