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Robust optimal control of polymorphic transformation in batch crystallization
Author(s) -
Hermanto Martin Wijaya,
Chiu MinSen,
Woo XingYi,
Braatz Richard D.
Publication year - 2007
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.11266
Subject(s) - setpoint , robustness (evolution) , crystallization , optimal control , batch processing , computer science , process engineering , mathematics , control theory (sociology) , biological system , chemical engineering , mathematical optimization , chemistry , control (management) , engineering , biology , biochemistry , artificial intelligence , gene , programming language
One of the most important problems that can arise in the development of a pharmaceutical crystallization process is the control of polymorphism, in which there exist different crystal forms for the same chemical compound. Different polymorphs can have very different properties, such as bioavailability, which motivates the design of controlled processes to ensure consistent production of the desired polymorph to produce reliable therapeutic benefits upon delivery. The optimal batch control of the polymorphic transformation of L‐glutamic acid from the metastable α‐form to the stable β‐form is studied, with the goal of optimizing batch productivity, while providing robustness to variations in the physicochemical parameters that can occur in practice due to variations in contaminant profiles in the feedstocks. A nonlinear state feedback controller designed to follow an optimal setpoint trajectory defined in the crystallization phase diagram simultaneously provided high‐batch productivity and robustness, in contrast to optimal temperature control strategies that were either nonrobust or resulted in long‐batch times. The results motivate the incorporation of the proposed approach into the design of operating procedures for polymorphic batch crystallizations. © 2007 American Institute of Chemical Engineers AIChE J, 2007