Contents lists available at ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur Optimizing reboiler duty and reflux ratio profiles of vapor recompressed batch distillation Sidharth Sankar Parhi a , Gade Pandu Rangaiah b , Amiya K. Jana a, ⁎ a Energy and Process Engineering Laboratory, Department of Chemical Engineering, Indian Institute of Technology, Kharagpur, 721302, India b Department of Chemical and Biomolecular Engineering, National University of Singapore, 117585, Singapore ARTICLE INFO Keywords: Vapor recompressed batch distillation Design of simulated experiments Multi-objective optimization Energy savings Dynamic reboiler heat duty Dynamic reflux ratio ABSTRACT Batch distillation columns are more energy inefficient than their continuous analogous. These batch columns commonly operate at a fixed reboiler duty and even reflux ratio. To improve their energetic potential, an attempt is made to optimize the reboiler duty, and reflux ratio profiles of the conventional batch scheme and its vapor recompressed counterpart. For this, an advanced version of the genetic algorithm is employed under the multi- objective optimization (MOO) framework. This stochastic optimization method (i.e., elitist non-dominated sorting genetic algorithm) is utilized to find a cluster of optimum points formally known as the Pareto-optimal front. Then, one optimal point is selected using the technique for order of preference by similarity to ideal solution method with entropy information for weighting of objective functions, for selecting one of the Pareto- optimal solutions. Using these procedures, we first optimize the conventional column considering reboiler heat duty and reflux ratio profiles as decision variables along with others. Then, it is retrofitted by employing a vapor recompression based heat pump. Further, the MOO framework is used to design vapor recompressed batch distillation configuration in the new plant scenario. All these schemes are finally evaluated in terms of energy and cost savings, and total annual production (TAP). The TAP is increased reasonably, and the raw material requirement is reduced significantly for the conventional column operated at variable reboiler duty as compared column operated at constant reboiler heat duty mode. With the adaptation of vapor recompression in the conventional column, a significant reduction in energy is achieved without compromising TAP as compared to the optimal conventional column operated at dynamic reboiler heat duty and reflux mode. 1. Introduction It has been widely accepted that human civilization is exploiting natural resources at a much faster rate than they are being regenerated [1]. This leads to rapid depletion of natural reserves as most of the world’s energy demand is still fulfilled by combustion of fossil fuel (∼86%). This, in turn, liberates harmful greenhouse gases to the at- mosphere, which contribute to environmental pollution, global warming and climate change. The exponential rise in energy demand and substantial degradation in petroleum reserves have motivated re- search in improving the thermodynamic efficiency of energy-intensive processes such as distillation, through process intensification (PI). PI shows a promising future for environmental sustainability, better quality of product and flexibility while integrating safety. Distillation is employed for the separation of liquid mixtures on the basis of the volatility of the constituent components. In process in- dustries, it exclusively accounts for around 95% of all fluid separations [2] and 40% of total energy consumption [3]. The overall thermo- dynamic efficiency of distillation is very low at 5–20% due to the ir- reversible losses concerning heat and mass transfer, and pressure drop [4]. Heat integrated distillation schemes are well established in both industrial scale (e.g., vapor recompressed column (VRC) [6–12] and dividing wall column (DWC) [13–15]) and pilot/lab scale (heat in- tegrated distillation column (HIDiC)) [16–19]. Their feasibility has been mostly scrutinized for continuous distillation. Batch distillation is more energy inefficient compared to its con- tinuous analogous. The application of batch processing has experienced a renewed attention recently, especially in low-volume, pharmaceutical and high-value-added chemical industries. The heat pump system is used on batch columns, including its conventional configuration [7,20–22], middle vessel batch [23–25] and batch distillation with a side withdrawal [26,27]. Due to the dynamic nature of the batch pro- cessing, batch VRC is more complicated and challenging over its con- tinuous counterpart. To get maximum savings in energy and cost from https://doi.org/10.1016/j.seppur.2018.12.066 Received 16 September 2018; Received in revised form 1 December 2018; Accepted 23 December 2018 ⁎ Corresponding author. E-mail address: akjana@che.iitkgp.ernet.in (A.K. Jana). Separation and Purification Technology 213 (2019) 553–570 Available online 24 December 2018 1383-5866/ © 2019 Elsevier B.V. All rights reserved. T