Fieldbus Application In Automatic Control System Of Stripping Process Removing Ammonia And Its Intelligent Control Study

Production wastewater in chemical enterprise is wastewater with high ammonia nitrogen concentration, which don't utilize the traditional sewage treatment methods to further process until passing through the remove ammonia pretreatment. The stripping process is often used to process wastewater with high ammonia nitrogen concentration. Because in stripping process, sewage temperature and pH in stripping towers are primary influential factors on stripping efficiency, control effect of the control system adjusting sewage temperature and pH is the core in the control system.According to the remove ammonia pretreatment system of Dupont Changshu Fluoro Technology Limited Company, this paper designs the distributed control system with Simens S7-300 PLC basing on the PROFIBUS fieldbus, and depicts the control system's network, hardware and software in detail. The control system adopts WINCC as the operation platform to watch and control 30 process parameters, which includes temperature, water level, flux, pH, wind content, ammonia nitrogen content, COD etc and water pump, metering pump, valve etc. And according to process requirement the system realize the closed-loop control on water level, temperature, pH and so on.This paper detailedly introduces the fuzzy control principle, fundamental operation methods and analyze several kinds of fuzzy controller's basic framework that used commonly at present. In order to enhance control effect about sewage temperature at the bottom of the stripping towers and reduce the run cost, this paper designs the fuzzy controller of the sewage temperature at the bottom of the stripping towers. The framework of the fuzzy controller adopt the discrete domain of two-dimensional fuzzy controller which take error and error change rate as input language variable and take valve opening increase as output language variable. Based on summarizing the expert's control experience, this paper designs the fuzzy controller's control rule and calculated the control lookup table with MATLAB.On the basis of experiments this paper obtains the step response curve of sewage temperature at the bottom of stripping towers, according to which this paper obtains the transfer function of sewage temperature at the bottom of the stripping towers. In order to realize the optimal control effect of sewage temperature at the bottom of the stripping towers, this paper compiles the PID procedures utilizing the Siemens PLC function block SFB41 and the lookup procedures of the fuzzy controller utilizing storage area indirect addressing mean. this paper carry out an experiment with the PID and fuzzy control. On the basis of the experiment this paper compare the PID control effect with fuzzy control effect of sewage temperature at the bottom of the stripping towers. According to sewage temperature demanded by process at the bottom of the stripping towers, this paper realizes the closed-loop control to sewage temperature at the bottom of the stripping towers.