Improvement of energy efficiency and production performance in a heteroazeotropic batch distillation unit: A study on decanter control and feeding strategy

• Different configurations of a batch distillation unit are studied in separation of a self-entrained heteroazeotropic mixture. • A decanter is found to be an efficient element to improve energy and separation efficiency of BDU. • Liquid level control is recognized as the key parameter in decanter and BDU performance. • The Inverted batch distillation configuration offers a significant improvement in energy and production performance. • Feeding rate is identified as a key parameter in inverted batch distillation. Dehydration of methyl isobutyl ketone (MIBK) using a batch distillation unit has been investigated through process simulation. Applying a decanter for upgrading the heteroazeotropic distillation is analyzed in different aspects. The unit performance dependency on the feed quantity, decanter design/control policy, decanter holdup volume, and subsequent phase separation quality are evaluated in detail. Feed quantity is recognized as a key factor influencing unit performance. Although increasing the feed quantity leads to a higher production rate (SPF) and lower specific energy cost (SEC), the optimal feed quantity is identified as the point beyond which further improvements in these variables become negligible. Also, reflux initiating time, liquid–liquid separation grade, loss of the desired component along with the effluent stream, and holdup loss at the end of the process are recognized as functions of decanter holdup quantity. Accordingly, a perfect decanter with a large holdup volume is not necessarily the best option. The evaluation indicates that an effective decanter lies on a larger aqueous phase holdup and smaller organic phase holdup, as long as it is capable of efficiently separating the liquid phases (over 75% separation efficiency for each phase). It is found that applying a well-designed and properly controlled decanter for the mixture separation (MIBK-water) can improve the unit recovery by up to 6% and the production rate (and energy cost) by up to 7% compared to a conventional batch distillation unit. Furthermore, an inverted batch distillation configuration with a gradual feeding policy is applied as an alternative and compared to other operation policies. The feeding schedule is found to be the key factor in this mode. The results reveal that an inverted distillation unit equipped with a properly designed and controlled decanter provides up to 17% improvement in energy and production rate as well as 7% in recovery for a 9% shorter process time compared to a conventional batch distillation unit.