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Design and Control of Ethanol/Benzene Separation by Energy-Saving Extraction-Distillation Process Using Glycerol as an Effective Heavy Solvent Wei-Cheng Shen, and I-Lung Chien Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.9b03095 • Publication Date (Web): 08 Jul 2019 Downloaded from pubs.acs.org on July 17, 2019
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Industrial & Engineering Chemistry Research
Paper submitted for publication in Ind. Eng. Chem. Res.
Design and Control of Ethanol/Benzene Separation by Energy-Saving Extraction-Distillation Process Using Glycerol as an Effective Heavy Solvent
Wei-Cheng Shen and I-Lung Chien*
Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
*
Corresponding author. I-Lung Chien, Tel: +886-2-3366-3063; Fax: +886-2-2362-3040; E-mail:
[email protected] 1
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Revised: July 5, 2019
ABSTRACT An energy-efficient extraction-distillation process for separating ethanol/benzene is investigated in this paper. Compared with other separation methods (i.e., azeotropic distillation, extractive distillation and pressure-swing distillation), solvent extraction remains to be one of the most preferable separation methods because the separation principle is achieved by their relative solubility in two different immiscible liquid phases without energy usage. Thus, lower operating cost by utilizing an extractiondistillation separation process is expectable with finding of an effective solvent. In this work, glycerol as a heavy solvent, is used to extract ethanol from benzene in the extraction column. Since the extract phase inevitably contains some benzene and also ethanol is not a stable node in the operating distillation region, two alternative distillation sequences can be considered to obtain ethanol product at purity specification and also purify glycerol for recycling back to extraction column. Experimental data from ternary
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(ABE) fermentation broth. The results showed that a
significant reduction of energy consumption can be achieved compared to the distillation process. For the acetic acid16, bioethanol17 n-propanol18, pyridine19, acetonitrile20 and propylene glycol methyl ether21,
22
dehydration processes, effective solvents such as
MTBE, n-dodecane, diisopropyl ether, n-propyl chloride and 2-ethylhexanoic acid were successfully adopted in hybrid 0
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systems. Furthermore, special
design concepts are introduced into solvent extraction for separating of a ternary mixture.
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Industrial & Engineering Chemistry Research
Yi et al.23 designed an alternative process to recover methanol and toluene in water without adding an additional component in the system. Not only it could avoid the potential problems of having another component in the system, it also showed noticeable energy savings. For the above separation processes involving extraction, very few papers had studied the addition of heavy solvent in the extraction-distillation system. Most of them employed low-boiling organic solvents except for Martinez et al.17 and Zhao et al.21. Despite using heavy solvents in their research17, 21, the design concept differed from general extraction-distillation system. Both of them designed an extraction column followed by an extractive distillation configuration for further purification of the heavy solvent and recycled it back to the extraction column and the extractive distillation column. In the following study, high-boiling solvent is proposed to carry almost all of the ethanol into the extract stream and making only benzene remains in the raffinate stream. Since the extract phase inevitably contains some benzene to form a ternary mixture, two alternative distillation sequences can be considered to obtain ethanol product at purity specification and also purify solvent to be recycled back to the extraction column. Moreover, rigorous verifications of thermodynamic ternary < (LLE) model and binary "
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