Design And Development Of Control System Based On DCS In Chemical Production Of PVC

The production process of PVC with suspension method is strict to the control system, which highly depended on the parameters of temperature. The hysteresis of the factors such as the high demand and the reaction kettle with exothermic reaction material inhomogeneity, reactor temperature interaction make the temperature control more complicated, especially when the reactor is in the stage of polymerization and drying process.Based on this problem, this paper designed a distributed control system which from top to bottom, and the advanced control algorithm is successfully embedded into the distributed control system.Firstly, based on the control requirements of the production of polyvinyl chlorideproduced with the suspension method, and according to the control points design the overall structure of distributed control system, including DCS control system manufacturers and models, the I/O card, card cage type, the control requirements of the control station and operation station hardware, connecting terminal and so on.Secondly, the control station, operator station, engineer station configuration design, the configuration of the system mainly consists of two parts:the DCS control system hardware configuration and the PC configuration software to the control process when system is on real-time monitoring. Then, establish the control station connecting channel between host computer and lower computer, which is base on the RS485 bus and Modbus protocol communication between DCS control system and the third equipment such as inverter.Thirdly, the design of distributed control system is based on the production process of PVC by using the conventional control algorithm and the design of advanced control algorithm. The conventional control algorithm consists of a single loop control, cascade control, feedforward control, ratio control. Advanced control is mainly including controller based on neural network algorithm. When the conventional control algorithm can not meet the requirement of production, use advance control method instead of it.This meet the production requirements without disturbance between the advanced control system and the conventional control method. To realize the real-time control of the reaction kettle, designed Centralized monitoring system.Finally, design the PVC production monitoring system interface by using SUPCON software AdvanTrol-Pro, and throngh the control station, signal conversion from field data real-time are displayed and processed. Control system of PVC is freedom to switch to realize manual and automatic, conventional control andadvanced control. Put the completed control system into the industry, analysis the operation results which shows that the advanced control algorithm of DCS has good control effect on the production of PVC.