Optimal programming of ideal and extractive batch distillation: single vessel operations

This work addresses the problem of optimal programming of multi-component b atch distillation columns with a single vessel (batch rectifier, batch stri pper, middle vessel and extractive middle vessel) so as to maximize an annu alized profit function. A smooth price function is formulated for product v aluation, allowing to release traditional purity constraints. The solution is the optimal batch policy of top/bottom withdrawals. A simplified cascade model is developed for separation calculations, offering several operation al patterns. Ideal and non-ideal mixtures can be handled with this model th at is proposed as a substitute for traditionally used Fenske-Underwood-Gill iland cascades. Batch separations of ideal quaternary feeds are optimally p rogrammed for the first three operations aforementioned. The extractive mid dle vessel column was optimally programmed for production of anhydrous etha nol from hydrated, nearly azeotropic, alcohol with ethylene-glycol as entra iner. All applications considered fixed number of stages, heat duty, and, i n the extractive system, fixed pump-around rate of entrainer. (C) 2001 Else vier Science Ltd. All rights reserved.