Study On Application Of DCS Control System In Wastewater Treatment Process Of Inorganic Silicon Production Enterprises

With the rapid development of China’s industrial economy,a large amount of industrial wastewater has been generated,which leads to the increasingly serious problem of water pollution in China.It not only effects on people’s lives,but also restricts the sustainable development of the economy seriously.Industrial sewage treatment is a frequent discussed topic,and it is usually high-cost and low-output.For the sake of energy conservation,emission reduction,cost reduction and efficiency improvement,the enterprises must focus on improving the efficiency and technology of sewage treatment.In China’s thirteenth five-stage,wastewater treatment has been a focused issue and attracts many business investments.In this study,wastewater treatment in an inorganic silicon plant is considered as the research object,and the pivotal process has been researched and optimized.Then,an optimal control strategy is proposed for solving the technical problem in pH control during acid-base neutralization process.The simulation research and comparative analysis results validate the effectiveness and reliability.The specific contents are as follows:(1)The current situation of wastewater treatment and the DCS system application is elaborated.And the research progress of pH control strategy in the wastewater treatment process is summarized and reviewed.(2)The pivotal process of the sewage treatment is researched and optimized.There is a problem that the pH value and the pH valve have to be adjusted and switched repeatedly in the neutralization section.For solving this problem,a rough tune and fine tune scheme is proposed,it also improves the convenience and operation efficiency of the pH adjustment;In view of the time delay characteristic of pH measurement process and the frequent maintenance of pH electrode,the pH detection position was moved to reduce the delay time and measurement error,enhance the stability of pH detection and reduce the maintenance cost.In view of the problems in the flocculation section,such as the unsatisfactory flocculation effect and the difficulty in estimating the flocculation end point,some schemes,such as adding mixer,buffer tank and turbid meter,were proposed to further improve the mixing effect and flocculation efficiency.(3)Focusing on the wastewater collection pool in the neutralization section,the pH control strategy is carried out with the simulation experimental modeling.Aiming at the problems of a large time lag,large inertia,nonlinearity and overshoot and oscillation that caused by the conventional PID control strategy in acid-base neutralization process,a step-response method is used to establish the non-parametric model of pH neutralization process in wastewater collection tank.Second-order approximation and mathematical calculations are utilized to obtain the dynamic characteristic equations described by transfer function.Then based on above work,a control strategy based on fuzzy-Smith control and expert fuzzy control is proposed.The SIMULINK toolbox based on MATLAB platform,is utilized to design and simulate the fuzzy controller,and the performance is compared to the classical PID control strategy.The results show that the overshoot and response speed of the fuzzy-Smith control with integral action are better.The performance of the expert fuzzy control is better than the classical fuzzySmith control.It has little overshoot and high dynamic response characteristics.It is an effective method to solve the process control of a large time delay and is suitable for application in the existing sewage treatment process.(4)Based on the improved wastewater treatment process and its control requirements,an automatic control scheme of the whole sewage treatment process is designed.Then,on the basis of statistics of the whole system monitoring and control points,the ECS-100 DCS control system of Zhejiang supcon is applied for system integration design,including DCS hardware selection and monitoring configuration.It lays a solid foundation for further study of process optimization,control strategy implementation and system debugging.