Model Based Temperature Control System Design For A Jacketed Reactor

Jacketed reactor is a commonly used reaction vessel in chemical engineering applications, for which temperature control is taken as one of the main regulation methods in practice, and therefore, has been an important research topic in the chemical and industrial process control field for a long time. Due to the indirect heat transfer mode and the internal reaction complexity of a jacketed reactor, it has been classified as a typical nonlinear system with time delay and large inertia in response. Since traditional control methods have obvious deficiencies such as the large overshoot and long settling time for temperature regulation, advanced control methods have been appealed to overcome these deficiencies.To overcome the problems of low control accuracy, high energy consumption for system operation, and unfriendly man-machine interaction involved with the existing temperature control devices for jacketed reactors, the thesis designs a temperature control system which consists of a programmable logic controller (PLC), frequency inverter, compressor, heating tube, thermocouples, monitoring computer, etc. The monitoring system is designed by using the LabVIEW software package, which provides an intuitive man-machine interface and data communication for hardware devices, while facilitates the programming of complex control algorithms and store historical operation data. The PLC plays an important link between the control algorithm and controlled object. On one hand, it should transmit the real-time temperature to the monitoring computer; On the other hand, it give a real-time command of the actuators based on receiving the control signal from the monitoring computer.Taking a 4-liter jacketed reactor for case study, by proposing a step response model identification method, integrating type transfer function models with time delay are established for the heating-up and cooling-down processes, respectively, based on the reactor characteristics of energy transfer. To overcome the deficiency of relatively large overshoot in the heating-up or cooling-down response of a traditional unity feedback control scheme, the thesis adopts a two-degrees-of-freedom internal model control structure to propose a new design method for the set-point tracking and load disturbance rejection, based on the identified models. To deal with the control saturation problem for practical applications, controller tuning methods are also proposed to comply with the practical constraints for implementation, so as to facilitate engineering applications.Based on the designed temperature control system, experiments are performed to verify the proposed identification and control algorithms. Firstly, the heating-up and cooling-down process models are established by using the step response data of these processes. The results show that the proposed identification algorithms can effectively identify the temperature response characteristics of a jacketed reactor, obtaining quite good fitting effect. Then, temperature control experiments are performed based on the control system design in terms of the identified models. By comparison with the existing control methods, the effectiveness and advantage of the proposed control method are verified which can realize precise temperature control for a jacketed reactor.