Design Of Automatic Control And Monitoring System For Plant-level Water Purification

Tap water production is one of the key basic industries related to the national economy and people’s livelihood.With the development of society and the progress of science and technology,people’s demand for the stability and reliability of tap water quality is constantly increasing,and the demand for automatic control of water purification production is also increasing.Based on the engineering requirement of a new water purification plant in Shanxi Province and combined with the water treatment process,this paper completes the design of distributed automatic control and real-time monitoring system for the production and operation of water purification,and develops a centralized monitoring and control system for the production and operation of the whole plant based on WinCC,including hardware circuit construction,software system development and communication connection configuration.The specific work of this paper is as follows:(1)The overall control scheme of the system is formulated and the key process control algorithm is studied.The relationship between flocculant dosage and turbidity,pH and flow rate of raw water was studied,and a mathematical model of flocculant dosage based on similar operation data of waterworks was established.In VC environment,the control program of optimizing dosage based on periodic self-operation of field data is designed.According to the characteristics of large time delay in coagulation process,the turbidity of effluent from sedimentation basin is introduced as feedback to form a compound loop control system.According to the actual situation of effluent turbidity,the parameters are adjusted by using fuzzy PID control to complete online control of dosage.(2)According to the process requirements,the control program of each control unit is compiled.Seven Siemens CPU315-2PN/DP workstations were used as control layer workstations.According to the control requirements of each process,the PLC control procedures and HMI interfaces were compiled by TIA Protal V14 software.The operation of each equipment in flocculation and sedimentation workshop,filter and backwash workshop,as well as the coordinated operation control of the whole process production were completed,and the acquisition of each process parameter was realized in time.It can be adjusted to ensure the quality of water treatment.(3)Design a monitoring system suitable for the production and operation of the plant-level water purification system.WinCC configuration software is used to design the upper computer monitoring system consisting of the main interface,staff management system,parameter setting system,operation recording system,alarm recording system and process monitoring interface.It can dynamically display the production process of each process,the running status of each equipment and the trend curve of each parameter.It has abundant interface functions.Establish staff management database,production and operation database,fault and alarm database,complete the real-time adjustment,recording,archiving and management of process parameters in each link.(4)The communication network is constructed by using ring Ethernet to complete the data communication between each PLC control station and management monitoring system.By using time-sharing communication method,the link redundancy is realized,and the problems of large data flow,network congestion and communication delay are solved.It has the characteristics of high reliability,high exchange rate and strong anti-interference ability.In the overall structure of the plant-level water purification system,the hardware configuration has high expansibility and easy networking.While completing the control function required by the factory,it can effectively improve the automation level of the water plant,reduce the intensity of labor production and effectively guarantee the reliability of water supply and water quality safety.