Separation of n-heptane/isobutanol via eco-efficient vapor recompression-assisted distillation: process optimization and control strategy

Abstract

In this study, vapor recompression and heat integration assisted distillation arrangements with either the low or high pressure in the reflux drum are proposed to reduce and/or eliminate the application of the costly refrigerant for the separation of n-heptane and isobutanol mixture. The high-pressure arrangement with vapor recompression and heat integration is the most attractive among these four intensified configurations since it can reduce total annual cost by 18.10%, CO₂ emissions by 75.01% based on natural gas (78.78% based on heavy oil fuel), and second-law efficiency by 61.20% compared to a conventional refrigerated distillation system. Furthermore, exergy destruction in each component is calculated for the heat integration configurations and is shown in pie diagrams. The results demonstrate that the high-pressure configuration presents unique advantages in terms of thermodynamic efficiency compared to the low-pressure case. In addition, dynamic control investigation is performed for the economically efficient arrangement and good product compositions are well controlled through a dual-point temperature control strategy with almost negligible product offsets and quick process responses when addressing 20% step changes in production rate and feed composition. Note that there are no composition measurement loops in our developed control schemes.

Graphical abstract

Keywords

n-heptane/isobutanol / vapor recompression / heat integration / low and/or high-pressure options

References

[1] Hu E, Gao Z, Liu Y, Yin G, Huang Z. Experimental and modeling study on ignition delay times of dimethoxy methane/n-heptane blends. Fuel, 2017, 189: 350–357

[2] Danon R, Alhseinat E, Peters C, Banat F. Solubility of heptane in aqueous solutions of methyldiethanolamine (MDEA). Fluid Phase Equilibria, 2016, 415: 18–24

[3] Yusoff M N A M, Zulkifli N W M, Masjuki H H, Harith M H, Syahir A Z, Khuong L S, Zaharin M S M, Alabdulkarem A. Comparative assessment of ethanol and isobutanol addition in gasoline on engine performance and exhaust emissions. Journal of Cleaner Production, 2018, 190: 483–495

[4] Magee W L. Method for preparation of alkyl vanadates. US Patent, 4351775, 1982-09-28

[5] Wang Y, Zhang Z, Xu D, Liu W, Zhu Z. Design and control of pressure-swing distillation for azeotropes with different types of boiling behavior at different pressures. Journal of Process Control, 2016, 42: 59–76

[6] Zhang Q, Shi P, Hou W, Yang S, Zeng A, Ma Y, Yuan X. Dynamic control analysis of an eco-efficient side-stream extractive distillation configuration. Separation and Purification Technology, 2020, 239: 116525

[7] Feng Z, Shen W, Rangaiah G P, Dong L. Design and control of vapor recompression assisted extractive distillation for separating n-hexane and ethyl acetate. Separation and Purification Technology, 2020, 240: 116655

[8] Wang Y, Liang S, Bu G, Liu W, Zhang Z, Zhu Z. Effect of solvent flow rates on controllability of extractive distillation for separating binary azeotropic mixture. Industrial & Engineering Chemistry Research, 2015, 54(51): 12908–12919

[9] Cui C, Liu S, Sun J. Optimal selection of operating pressure for distillation columns. Chemical Engineering Research & Design, 2018, 137: 291–307

[10] Risco A, Plesu V, Heydenreich J A, Bonet J, Bonet-Ruiz A E, Calvet A, Iancu P, Llorens J. Pressure selection for non-reactive and reactive pressure-swing distillation. Chemical Engineering and Processing-Process Intensification, 2019, 135: 9–21

[11] You X, Rodriguez-Donis I, Gerbaud V. Low pressure design for reducing energy cost of extractive distillation for separating diisopropyl ether and isopropyl alcohol. Chemical Engineering Research & Design, 2016, 109: 540–552

[12] Luyben W L. Distillation column pressure selection. Separation and Purification Technology, 2016, 168: 62–67

[13] Cui C, Sun J. Rigorous design and simultaneous optimization of extractive distillation systems considering the effect of column pressures. Chemical Engineering and Processing-Process Intensification, 2019, 139: 68–77

[14] Wang Y, Qi P, Yang X, Zhu Z, Gao J, Zhang F. Exploration of a heat-integrated pressure-swing distillation process with a varied-diameter column for binary azeotrope separation. Chemical Engineering Communications, 2019, 206(12): 1689–1705

[15] Luyben W L. Design and control comparison of alternative separation methods for n-heptane/isobutanol. Chemical Engineering & Technology, 2017, 40(10): 1895–1906

[16] Feng Z, Shen W, Rangaiah G P, Lv L, Dong L. Process development, assessment, and control of reactive dividing-wall column with vapor recompression for producing n-propyl acetate. Industrial & Engineering Chemistry Research, 2018, 58(1): 276–295

[17] Li Q, Feng Z, Rangaiah G P, Dong L. Process optimization of heat-integrated extractive dividing-wall columns for energy-saving separation of CO₂ and hydrocarbons. Industrial & Engineering Chemistry Research, 2020, 59(23): 11000–11011

[18] Leo M B, Dutta A, Farooq S. Process synthesis and optimization of heat pump assisted distillation for ethylene-ethane separation. Industrial & Engineering Chemistry Research, 2018, 57(34): 11747–11756

[19] Luyben W L. High-pressure versus low-pressure auxiliary condensers in distillation vapor recompression. Computers & Chemical Engineering, 2019, 125: 427–433

[20] Pleşu V, Bonet Ruiz A E, Bonet J, Llorens J. Simple equation for suitability of heat pump sse in distillation. Computer-Aided Chemical Engineering, 2014, 33: 1327–1332

[21] Douglas J M. Conceptual design of chemical processes. New York: McGraw-Hill, 1988, 289–315

[22] Gadalla M A, Olujic Z, Jansens P J, Jobson M, Smith R. Reducing CO₂ emissions and energy consumption of heat-integrated distillation systems. Environmental Science & Technology, 2005, 39(17): 6860–6870

[23] Waheed M A, Oni A O, Adejuyigbe S B, Adewumi B A, Fadare D A. Performance enhancement of vapor recompression heat pump. Applied Energy, 2014, 114: 69–79

[24] Seader J D, Henley E J, Roper D K. Separation Process Principles. Hoboken: John Wiley & Sons, Inc, 2010, 258–286

[25] Zhang Q, Liu M, Zeng A. Performance enhancement of pressure-swing distillation process by the combined use of vapor recompression and thermal integration. Computers & Chemical Engineering, 2019, 120: 30–45

[26] Zhang Q, Yang S, Shi P, Hou W, Zeng A, Ma Y, Yuan X. Economically and thermodynamically efficient heat pump-assisted side-stream pressure-swing distillation arrangement for separating a maximum-boiling azeotrope. Applied Thermal Engineering, 2020, 173: 115228

[27] Shi P, Zhang Q, Zeng A, Ma Y, Yuan X. Eco-efficient vapor recompression-assisted pressure-swing distillation process for the separation of a maximum-boiling azeotrope. Energy, 2020, 196: 117095

[28] Yang S, Zhang Q, Ma Y, Yuan X, Zeng A. Eco-efficient self-heat recuperative vapor recompression-assisted side-stream pressure-swing distillation arrangement for separating a minimum-boiling azeotrope. Industrial & Engineering Chemistry Research, 2020, 59(29): 13190–13203

[29] Luyben W L. Distillation Design and Control Using AspenTM Simulation. Hoboken: John Wiley & Sons, Inc, 2013, 145–184

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