NONLINEAR ADAPTIVE TEMPERATURE CONTROL OF MULTIPRODUCT, SEMIBATCH POLYMERIZATION REACTORS

This paper considers the temperature control of semi-batch polymerizat ion reactors in which some of the following issues must be considered: (i) production of multiple products in the same reactor; (ii) changin g heat transfer characteristics, during a batch and from batch to batc h; (iii) time varying and nonlinear reaction rate due to changing mono mer concentration and diffusion controlled termination reactions (gel effect); (iv) the absence of detailed kinetic models for the reactors. The industrial challenge problem published by Chylla and Haase [Chyll a, R. W. and Haase, D. R. (1993) Temperature control of semi-batch pol ymerization reactors (with corrected updates). Comput. Chem. Eng. 17, 257-264) is used as the simulation basis for evaluating these problems . A nonlinear adaptive controller consisting of a nonlinear controller (based on differential geometric concepts) coupled with an extended K alman filter (which uses only readily available data and knowledge) is shown to provide excellent control in all the above situations. In pa rticular, the on-line estimation is critical for the strong performanc e of the nonlinear controller over a broad range of conditions. PID co ntrollers with feedforward terms can perform well at one set of condit ions, however, they require retuning as conditions and products change . (C) 1997 Elsevier Science Ltd.