CHEMICAL ENGINEERING TRANSACTIONS VOL. 76, 2019 A publication of The Italian Association of Chemical Engineering Online at www.aidic.it/cet Guest Editors: Petar S. Varbanov, Timothy G. Walmsley, Jiří J. Klemeš, Panos Seferlis Copyright © 2019, AIDIC Servizi S.r.l. ISBN 978-88-95608-73-0; ISSN 2283-9216 Energy Consumption in Sharp and Non-Sharp Splits of Ideal Ternary Mixtures Sergi Expósito a , Jordi Bone a, *, Alexandra Elena Bonet-Ruiz a , Joan Llorens a , Petrica Iancu b , Valentin Plesu b a University of Barcelona, Faculty of Chemistry, Department of Chemical Engineering and Analytical Chemistry, Martí i Franquès Street 1, 6th Floor, 08028 Barcelona, Spain b University POLITEHNICA of Bucharest, Department of Chemical and Biochemical Engineering - Centre for Technology Transfer in the Process Industries, 1, Gh. POLIZU Street, Building A, Room A056, RO-011061 BUCHAREST, Romania bonet@ub.edu Most of the distillation processes deal with multicomponent mixtures, existing a great quantity of distillation sequences for this process. The sharp splits available for an ideal ternary mixture are the direct and the inverse distillation sequence scheme in which the compounds are separated in two different columns. There are non- sharp splits in which all the compounds are separated in a single distillation column that can incorporate a side column. Unfortunately, to choose non-sharp splits schemes, there is no heuristic that can provide information about the recommended cases, e.g. a single distillation column in which the intermediate boiling compound is collected by a side stream at the required purity or by other possibilities, such as the use of a side stripper or a side rectifier. The literature about this subject is very scarce, and many times when the non-sharp splits are used, no comparison with the sharp split alternatives is provided. Therefore, the cases for which the literature suggests the use of side columns are further studied, e.g. BTX (Benzene, Toluene, Xylene) mixtures separation. For many case studies, the results obtained show that the energy savings achieved, due to the use of side columns, are not significantly higher than the best sharp split process schemes. However, these results do not discard that for some other situations; the side column could be the most advantageous case. Usually, it is considered that when the desired purity of the main product in a stream is reached, the impurities proportion do not affect significantly the energy consumption, and for most of the systems, this is true. However, for a mixture with a molar composition of 10 % isopentane, 10 % pentane and 80 % hexane (mol), when split in the respective compounds at a purity of 95 % (mol), very different energy requirements are depicted depending on the proportion of isopentane and hexane, present in the pentane stream obtained in a direct sequence process . The rigorous simulation results illustrate that almost 60% of the energy required to separate the above- mentioned mixture is saved when the pentane stream carries a mixture of isopentane and hexane. In addition, the environmental impact has been analyzed for each case studied, being reduced in the same way as the energy consumption does. 1. Introduction Distillation, which is the separation technique used most in the chemical and petrochemical industry, is highly energy-intensive. Therefore, there has been an active search for means to reduce energy usage and costs (Malinen and Tanskanen, 2009). 90 % of all separation units and 5 % of the global energy demand can be attributed to distillation (Humphrey, 1995). This process is used to obtain different pure components of a mixture, although in some cases, to obtain more than one pure component is possible by the use of conventional sequences (direct or indirect distillation) or thermally-coupled columns processes, like the side-rectifier or the side-stripper distillation. Thermally-coupled columns offer a great opportunity to reduce energy consumption (Triantafyllou and Smith, 1992). Usually, these columns are proposed directly as a better choice than direct or indirect sequences but many times, the results of non-conventional sequences are not compared with the conventional ones to confirm this DOI: 10.3303/CET1976134 Paper Received: 18/03/2019; Revised: 16/07/2019; Accepted: 22/07/2019 Please cite this article as: Exposito S., Bonet-Ruiz J., Bonet-Ruiz A.E., Llorens J., Iancu P., Plesu V., 2019, Energy Consumption in Sharp and Non-Sharp Splits of Ideal Ternary Mixtures, Chemical Engineering Transactions, 76, 799-804 DOI:10.3303/CET1976134 799