The Decoupling Control Of Alcohol Rectifying Tower

Chinese government strongly supports the development of the aqueous alcohol as new fuel. Many countries research it because it will be the Substitute for petroleum. The high- purity alcohol distillation is very important in the production process of fuel alcohol. But the alcohol distillation tower system is a multivariable, coupled, nonlinear and time-varying system. By now, automatic control for the alcohol distillation tower system is still a difficult technical problem. Because of the serious coupling among variables, perfect control result can be hardly got by single loop PID controller. Traditional manual control tends to cause failures. For example the temperature is difficult to be lowered to the set point after rising abruptly, which will cause the system reach stable state for a long time. So, studying how to realize the automatic control for the alcohol rectifying tower system in order to improve the reliability of its operation and enhance its automatic control rate is significant in academic and practical feild.At first, this dissertation introduces the history of distillation techniques briefly. Then it focuses on the analysis of the coupling of alcohol distillation columns and select the control variables of decoupling control. In this paper, It gives full consideration to the coupling between the alcohol distillation column. For the top temperature and the bottom, I design a fuzzy-decoupling control system: making the given value of bottom temperature and top temperature as the center, and the regional is divided into positive deviation and negative deviation. According to different regional bias, it controls the reflux and reboiler power. And the output signal is sent back directly to the Fuzzy control loop. The simulation of the fuzzy decoupling controller gets a well control effect.On the other hand, this dissertationr's work is to implement fuzzy decoupling algorithm in the application of laboratory equipment. The communication method is DDE. I configurates the server to KingView and MATLAB for the client. The fuzzy decoupling complier call for KingView, and changing the original model of PLC called for PID controller. Last I Implement the control method which can switches between fuzzy decoupling controller and PID controller.