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Optimal operation of multivessel batch distillation columns

Authors

  • H. I. Furlonge,

    1. Centre for Process Systems Engineering, Imperial College of Science, Technology and Medicine, London SW7 2BY, United Kingdom
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  • C. C. Pantelides,

    1. Centre for Process Systems Engineering, Imperial College of Science, Technology and Medicine, London SW7 2BY, United Kingdom
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  • E. Sørensen

    Corresponding author
    1. Dept. of Chemical Engineering, University College London, London WC1E 7JE, United Kingdom
    • Dept. of Chemical Engineering, University College London, London WC1E 7JE, United Kingdom
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Abstract

Increased interest in unconventional batch distillation column configurations offers new opportunities for increasing the flexibility and energy efficiency of batch distillation. One configuration of particular interest is the multivessel column, which can be viewed as a generalization of all previously studied batch column configurations. A detailed dynamic model was used for comparing various optimal operating policies for a batch distillation column with two intermediate vessels. A wide variety of degrees of freedom including reflux ratios, product withdrawal rates, heat input to the reboiler, and initial feed distribution were considered. A mixture consisting of methanol, ethanol, n-propanol and n-butanol was studied using an objective function relating to the economics of the column operation. Optimizing the initial distribution of the feed among the vessels improved column performance significantly. For some separations, withdrawing product from the vessels into accumulators was better than total reflux operation in terms of energy consumption. Open-loop optimal operation was also compared to a recently proposed feedback control strategy where the controller parameters are optimized. The energy consumption of a regular column was about twice that of a multivessel column having the same number of stages.

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