Heat release estimator based globally linearizing control of a chemical reactor t

P Anand, J Sridhar, Ch Venkateswarlu
2003 Indian Journal of Chemical Technology   unpublished
An energy model based,. globally. � controller (EMBGLC), supported by a deterininistic filter, is presented for temperature control or an exitth erinic batch reactor. The deterministic ruter is used to estimate the rate of heat release required for the· cOn�Ue�� �.,results of the EMBGLC supported by the deterininistic ruter are compared with the EMBGLC b�, f.)n o�r: ai!terministi � heat release estimators including a direct energy b8Iance and a kinetic rate express ion., �(·t �;swt$·, sIiO �{
more » ... �;swt$·, sIiO �{ that :tbe ' EMBGLC based on deterministic ruter provides better performance for the temperature ,tqofr6rO.r the, � iotherniiC batch cbemical reactor. Chemical processes have been traditionally operated using conventional controllers. Specific controller problems associated with chemical processes severely limit conventional control performance. Therefore, advanced control strategies have become an important part of the control structure for improving performance. Model based control, forms one class of advanced control strategies. Such control strategies use mathematical models of the process to infer control action. In the recent years, diffe rential geometry have been used as an effective tool for the analysis and design of non-linear process control synthesis, similar to the way that Laplace transforms and linear algebra have been used for the linear control systems analysis and design. An understanding of the structural characteristics of non-linear systems can be obtained using differential geometric concepts. A tutorial on diffe rential geometry methods is given by Kravaris and Kantorl for non-linear process control system design. Globally linearizing controf aims at finding global non-linear transformations on the states and/or the manipulated inputs so that the transformed system reduces to a linear input-output system. A simple PI controller is then used on the linear input-output variables. Chemical reactors, especially batch reactors occupy a special position in chemical processing industries. Realizing the advantages offered by the advanced controllers, various model based controllers involving f UCT Communication No. 020109 rigorous process models have been reported for batch reactors3,4. Although rigorous process model is quite useful in deriving efficient controllers, developing and validating rigorous models involving reaction mechanisms and reaction kinetics require considerable time and effort. Therefore, control strategies based on models that avoid reaction kinetics and instantaneous composition measurements, but preserve the rigouressness by instantaneous estimation of unknown information are quite beneficial. In this study, an energy balance model is used to derive a globally linearizing control strategy, the performance of which is evaluated by applying for temperature tracking of an exothermic batch chemical reactor. The rate of heat release required for the control strategy is estimated using a deterministic filter. Further, deterministic estimators such as direct energy balance and kinetic rate expression are also used to provide the rate of heat release required for the controller. The results of the energy model based globally linearizing controller (EMBGLC) with deterministic filter are compared with that of EMBGLC based on direct energy balance and kinetic rate expression.