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Energy Efficient Trace Removal by Extractive Distillation

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Energy Efficient Trace Removal by Extractive Distillation Energy efficient trace removal by extractive distillation Citation for published version (APA): Jongmans, M. T. G. (2012). Energy efficient trace removal by extractive distillation. Technische Universiteit Eindhoven. https://doi.org/10.6100/IR732573 DOI: 10.6100/IR732573 Document status and date: Published: 01/01/2012 Document Version: Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, please follow below link for the End User Agreement: www.tue.nl/taverne Take down policy If you believe that this document breaches copyright please contact us at: [email protected] providing details and we will investigate your claim. Download date: 24. Sep. 2021 Energy Efficient Trace Removal by Extractive Distillation M.T.G. Jongmans Doctoral Committee Chairman prof. dr. J. Meuldijk Eindhoven University of Technology Promoter prof. dr. ir. A.B. de Haan Eindhoven University of Technology Assistant promoter dr. ir. B. Schuur Eindhoven University of Technology Examiners prof. dr. ir. M.C. Kroon Eindhoven University of Technology prof. dr. ir. G.J. Witkamp Delft University of Technology dr. ir. D.C. Nijmeijer University of Twente prof. dr. ir. A. Nijmeijer University of Twente ir. G. Bargeman AkzoNobel Chemicals B.V. This project was an ISPT project (Institute for Sustainable Process Technology, The Netherlands). Energy Efficient Trace Removal by Extractive Distillation Jongmans, M.T.G. ISBN: 978-90-386-3148-6 A catalogue record is available from the Eindhoven University of Technology Library. Printed by Gildeprint, Enschede, The Netherlands. Copyright © M.T.G. Jongmans. The Netherlands, 2012. All rights reserved. Energy Efficient Trace Removal by Extractive Distillation PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Technische Universiteit Eindhoven, op gezag van de rector magnificus, prof.dr.ir. C.J. van Duijn, voor een commissie aangewezen door het College voor Promoties in het openbaar te verdedigen op woensdag 20 juni 2012 om 16.00 uur door Mark Theodorus Gerardus Jongmans geboren te Standdaarbuiten Dit proefschrift is goedgekeurd door de promotor: prof.dr.ir. A.B. de Haan Copromotor: dr.ir. B. Schuur Summary Summary Separation processes contribute for about 40–70 % to the total energy requirements of the chemical process industry. Especially when trace removal is required to manufacture high purity products, traditional separation technologies become extremely expensive and are not providing satisfying solutions. In this work, trace removal is defined as the separation of impurities or (by) products at a level of 100–1000 ppm. The main reason for trace removal separation is the need to meet the purity demanded by customers further processing and/or legislation. Distillation is currently used to conduct 90–95 % of all separations in the chemical process industry. The drawbacks of distillation are the poor energy efficiency and selectivity. These drawbacks are above all applicable to cases where impurities have to be removed with molecular structures closely resembling the main component (and hence, having similar boiling points) and are present at ppm level in a highly concentrated, organic stream. Two representative industrial examples are the separation of ethylbenzene traces (~100 ppm) from styrene and dichloroacetic acid (DCA) traces (~1000 ppm) from monochloroacetic acid (MCA). Both are examples of close-boiling mixtures (= low relative volatility). A well-established technology to separate close-boiling mixtures is extractive distillation. In extractive distillation, a solvent is added to a distillation column to alter the relative volatility of the system to be separated, and, thereby, to reduce the capital and operational expenditures (OPEX and CAPEX). Nowadays, extractive distillation is already applied to produce high purity products in benzene, toluene, xylene processes with purities up to 99.995 wt%. Therefore, the main objective of the research described in this thesis was to investigate whether extractive distillation could be a promising technology to obtain high purity products for the two representative industrial examples. For both cases, the trace removal and bulk separation were both performed by extractive distillation processes to be able to replace the current separation processes, and thus also achieving process intensification. Sulfolane, which is a commonly applied organic solvent, and a wide range of ionic liquids (ILs) were investigated for the separation of ethylbenzene from styrene to obtain ethylbenzene impurity levels lower than 10 ppm in styrene. Complexing agents (extractants) were studied to separate DCA from MCA to obtain high purity MCA (wDCA < 50 ppm). First, a solvent/extractant screening study was performed for both industrial cases followed by the measurement of binary and ternary liquid–liquid and vapor–liquid equilibrium data for the selected solvents and the regression of these data by thermodynamic models. Subsequently, the parameters obtained from the regressions were used in equilibrium stage process models to setup a conceptual process design for the extractive distillation processes I Summary including solvent regeneration. The conceptual process models that were developed using Aspen Plus®, were applied for the calculation of the energy requirements, leading to the operational expenditures (OPEX). The capital expenditures (CAPEX) were estimated using the Aspen Process Economic Analyzer®, and finally the total annual costs (TAC) were estimated from the OPEX and CAPEX. The current distillation unit was used as the benchmark process for the ethylbenzene/styrene system. The extractive distillation process for the MCA/DCA system could not be compared to the current separation process, because no process data is available about this process. Therefore, the added production costs per tonne of MCA product were calculated and compared to the current high purity MCA market price. Ethylbenzene/styrene A proper solvent should have a high selectivity as well as a high solvent capacity for the mixture to be separated by extractive distillation. Preferably, the solvent is even fully miscible with the ethylbenzene/styrene system, which was observed for the benchmark solvent sulfolane, whereas from the IL screening study it was found that ILs form multiple liquid phases with the ethylbenzene/styrene system. However, several ILs outperformed the benchmark solvent sulfolane with selectivities up to 2.5, whereas sulfolane displayed a solvent selectivity of about 1.6. Furthermore, it was observed from the IL screening study that a clear trade-off exists between the solvent capacity and selectivity. The ILs 3-methyl- N-butylpyridinium tetracyanoborate ([3-mebupy][B(CN)4]), 4-methyl-N-butylpyridinium tetrafluoroborate ([4-mebupy][BF4]), and 1-ethyl-3-methylimidazolium thiocyanate ([EMIM][SCN]) were selected as promising candidates to study in more detail. The solvent capacities for ethylbenzene and styrene increase in the order of [EMIM][SCN] > [4- mebupy][BF4] > [3-mebupy][B(CN)4]. The selectivity for the ethylbenzene/styrene system decreases in the same order. Binary and ternary phase equilibrium data were obtained for the systems ethylbenzene + styrene + selected ILs, and ethylbenzene + styrene + sulfolane. The NRTL model was able to correlate the phase equilibrium data adequately, and the parameters that were obtained by regression of the experimental data were used in the following chapters in the process simulations. A very important factor in extractive distillation processes is the recovery of the solvent. If that cannot be done adequately and cost effectively, the process cannot be competitive. Therefore, a screening of several IL recovery technologies was performed, for which the IL [4-mebupy][BF4] was taken as a model IL. It was found that this IL should be purified to at least 99.6 wt% in the regeneration section to maintain the distillate and bottom purity requirements for the primary separation of ethylbenzene and styrene in the extractive distillation column. From the TAC, the overall conclusion can be drawn that evaporation using very low pressures (P < 10 mbar)
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