Diagnosis of Abnormal Situations in a Continuous Solution Polymerization Reactor

Abstract

This work presents results on the problem of robust on‐line diagnosis of abnormal situations in the case of the free‐radical solution polymerization of styrene in a continuous well‐mixed reactor operating under feedback control. The control system is constituted of a model predictive control strategy in conjunction with a ratio control law. The proposed fault diagnosis system is based on an open‐loop approach, which uses a linearized model of the polymerization process for the implementation of a bank of reduced‐order unknown input observers. Each observer is designed to detect changes in a particular process parameter, external disturbance or malfunctioning of sensors and actuators. Fault isolation is obtained through a structured residual approach; meanwhile, fault estimation is performed using the degree of freedom remaining in the observer design. The effectiveness of the proposed technique is verified through numerical simulations carried out on a well‐defined industrial styrene polymerization benchmark.magnified image

Optimization and control of a continuous polymerization reactor

“…The phenomenological model of this styrene reactor was first published in 1990 and, since then, it has been widely used as a benchmark for process control studies (Maner et al, 1996;Gazi et al, 1996;Kendi and Doyle, 1998;Prasad et al, 2002;Asteasuain et al, 2006;Sotomayor et al, 2007). Prasad et al (2002) implemented a nonlinear MPC strategy for the control of the properties of the polymer.…”

A Critical Overview of Sensors for Monitoring Polymerizations

“…‘consider the state of the reactor as dangerous when both the first and second derivatives of temperature are positive’). See, for instance, Chien and Penlidis3 for some earlier classical references on the subject; Zhang et al597 on a process monitoring approach; Sotomayor and Odloak598 on observer‐based general fault diagnosis; Lou et al599 on diagnosis of impurity levels in a copolymerization process (with a discussion on observability and optimal experimental design in order to reduce fault misclassification); Sotomayor et al600 on diagnosis of abnormal situations in continuous solution polymerization; and, more recently, Sharmin et al601 on monitoring, data handling and fault detection issues for LDPE autoclaves. A related, potentially serious, problem that arises when handling data from sensors is the effect of numerous measurement errors and their propagation into the analysis.…”

A Dual Mode MPC Scheme for Nonlinear Processes

“…The model of the polymerization process is described by the following equations (Sotomayor et al, 2007):…”

“…A : area of heat transfer Cp : specific heat of the fluid in the reactor The numerical values of the model parameters and usual operating conditions of the reactor can be found in Sotomayor et al (2007). The control objective in the reactor is to maintain the reaction temperature (T) at the desired value by manipulating the flow of initiator (Q i ) and the flow of fluid to the cooling jacket (Q c ).…”