An Intelligent Control System Used In Ammonia Distilling Process

Ammonia distilling is to distill the residual ammonia from the blast section in an ammonia still, which evaporate the wolatile ammonia into the saturator to increase the production of vitiol ammonia and send waste water to biochemistry section to decontaminate. Therefore, if it is abnormal in ammonia distilling section, the production of vitiol ammonia will be unqualified and the biochemistry section will be abnormal too.which will leads the transnormal of sewage let. And the key to keep the distilling stable is the tempratue at top of the tilling tower, the temperature must be controlled between 103℃ and 105℃ in order to keep the distilling stable. But distilling tower temperature control is a typic big time-lag system, and the control of it is always a difficult problem in coak producing industry.This paper desighs an ammonia distilling control system with S7-300 PLC of SIEMENS Corporation based on the rebuilding condition of the ammonial distilling system of Wugang Jiaohua Corporation, which monitors eighteen technics parameters including temperatures pressures liquid levers and fluxs and controls nine parameters of them.According to the characteristic that the liquid surface of the trough and the ammonia water folw-in ammout affect each other, after summarizing the experience of the operating wokers, a intelligent expert control algorithm is propsed.Taking the engineering facts into account, according to the characteristic of big timelag system, this paper conbiles PID control and fuzzy control and designs a kind of fuzzy sef-tunning PID control algorithm, and then applys it in the control of temperature at top of distilling tower.The fuzzy self-tunning PID control system consists of two parts which are parameter adjustable PID system and fuzzy control system. Its inputs are error e and error change ec and adust its PED parameters kp , kt, kd online with fuzzy induce method based on the normal PIDcontroller. It can fulfill the command of different e and ec for PID parameters, which gives the controlled object a better static and dynamic performance.A simmulating experiment is made with the fuzzy self-tunning PID controller designed in this paper in MATLAB, the intelligent expert control algorithm and the fuzzy sef-tunning PID control algorithm are combined in the paper to make a experiment to sumulate the real ammonia distilling process with the EFPT pocess apparatus, the result shows the validity of the approch proposed in this paper.