A strategy for closed-loop optimization of batch distillation columns is proposed. The optimal reflux rate is calculated off-line for several feed compositions, and is correlated to the composition profile that is found in the column at the end of the startup phase. Since this composition profile can be estimated on-line by a state observer, it is possible to determine on-line the closed-loop optimal reflux ratio to be used with any feed of unknown composition. Results for binary and ternary systems indicate that, by using this procedure, the column performance can be improved by as much as 30percent with respect to a conventional open-loop optimal strategy.
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