Study On Temperature Control Of Vinyl Chloride Polymerization Reactor Based Onadaptive Fuzzy PID Control

Polyvinyl chloride(PVC) is an important chemical products that widely used in many fields. The most critical aspect in the PVC production process is the vinyl chloride polymerization occurred in the batch reactor. The most important parameter is the reaction temperature, the temperature control performance directly affects the quality of PVC products. Therefore, precise control of reaction temperature in the PVC production process is particularly important. However, the polymerization process have features such as nonlinear, time-varying and time delay and so on, it is difficult to establish accurate mathematical model, the traditional PID control method can hardly reach excellent control performance. Therefore, it is imperative to find a better control method to achieve precise control of polymerization reactor temperature.In this paper, vinyl chloride suspension polymerization was studied. The mechanism model of polymerization reaction process was build and simplified. New controllers was designed based on the feature of PVC production process and the requirements of polymerization process to the control system that achieved excellent control performance.Firstly, the author designed polymerization temperature fuzzy controller using fuzzy control theory based on the simplified model, including design of the controller structure , fuzzification of inputs and outputs, establishment of membership functions, design of fuzzy rules, defuzzification of inputs and outputs. and the polymerization temperature PID controller was simply designed, a set of control parameters with good performance was obtained using industrial turning method. Simulation of the two controllers provides a theoretical basis and initial parameters for the design of the following adaptive fuzzy PID controller.Secondly, the adaptive fuzzy PID controller was designed base on the design of fuzzy and PID controller and PID parameter self-tuning rules. The later simulation analysis showed its advantages and shortcomings, then some improvements was made against the disadvantages of the controller. The results of MATLAB simulation showed that among the four controllers, the improved adaptive fuzzy PID temperature controller get less overshoot and steady-state error then others, so it solved the problem of temperature control in the PVC polymerization better.