The Design And Realization Of Water Treatment Control System For Thermal Plant

In recent years, while the economy is developing exceedingly fast and steadily, more variable resources are needed in our country, especially the electric power. Our electric industry develops very quickly, mainly the power of thermal plant. Water in power plant can transfer the power and cool the medium, and the water quality is a significant factor of thermal equipment (boiler, turbine etc) safety and economical operation. In our country, the water treatment technology used in most power plants is relatively backward. Meanwhile, most water treatment systems are still controlled manually. The automatic degree is low, and water quality is difficult to hit the specified target. Therefore, to design an automatic control system for water treatment, which can operate continuously and stably with high automation is a priority.In this thesis, the control object is water treatment technology of thermal plant, the design rule is that the system can operate safely, accurately and reliably. By means of scientific method and modern way, in order to meet the requirements of producing technology, the design and realization of whole water treatment control system is achieved.Firstly, according to the situation of local equipments, the type of control system is ascertained. The water treatment equipments are abundant and variable. Besides, the locations are separate and most of the equipments are far away from the console cabinet. Therefore, we decide that this system is a remote I/O control system.Secondly, the hardware configuration is achieved based on quantities and types of the equipments. The control system is composed of industry computer,PLC primary station,slave station and local equipments. The data exchange between PLC controller and industry computer is achieved by way of industry Ethernet; the communication between PLC primary station and slave station is achieved based on PROFIBUS-DP protocol.Then, according to actual control requirements, the program of PLC is finished. the operation of single equipment,single water treatment technology step and the automatic operation of the whole technology can be achieved in the control system. Therefore, the PLC program can be composed of three kinds of control blocks above.Finally, the HMI of industry computer is achieved by way of WinCC HMI design software developed by Siemens Company. The HMI is composed of technology pictures and other function pictures. The technology pictures can be used to control the whole local technology procedure, but also the important parameters can be supervised; other function pictures including alarm pictures,report system and tendency chart can be used to supervised the important technology parameters.The water treatment control system in the thesis is used in reality after debugging work, it runs steadily, and the anticipated purpose is achieved.