The Design And Implement Of Control System In Natural Circulation Boiler Based On PCS7

The natural circulation boiler is choosed as the controlled object,and the Siemens PCS7 is choosed as the control system.All control loops are configured by CFC of SIMATIC S7,and many control methods are used in control loops,such as cascade control,split-ranging control,variable-ratio control,three-element control,feedback control,etc.These control methods realize the control function of superheated steam pressure,superheated steam temperature,oxygen content in flue gas,boiler water level and hearth negative pressure.It can weaken the coupling effect between variables and make the system run smoothly.In the control system,sequence control is applied and the configuration of sequence control is completed with SFC of SIMATIC S7.It can finish the sequential execution according to the requirements of production process.It can make the boiler system realize the function of automatic control from the cold driving to normal production and automatic stop in emergency circumstance.Safety instrument system is designed,and it can realize the function of over limit alarm,safety interlock and emergency stop.The design of HMI is accomplished with WinCC configuration software.HMI includes process interface,controller interface,alarm logging interface,history data archiving interface and trend curve interface.According to HMI,operators can monitor and manage the production process.