Exergy Analysis and Heat Integration of Distillation Columns Using Thermal Coupling Method for Separation of Ternary Mixture

Document Type : Research Article

Authors

Department of Chemical and Petroleum Engineering, Sharif University of Technology, Azadi Street, Tehran, Iran

Abstract

Despite distillation's popularity in the industry, it is highly energy-intensive. Heat integration is, therefore essential considering the recent energy crisis. This paper presents thermal coupling as an approach for separating the ternary mixture of n-pentane, n-hexane, and n-heptane. In this method, the first column supplies vapor to the second column while its reboiler is removed. The thermal coupling method is evaluated using two classical arrangements, direct and indirect with and without heat integration. Simulation of separation processes is carried out using Aspen HYSYS, and distillation columns are simulated using the rigorous solving method rather than the shortcut method. The simulation results are compared to those obtained using the shortcut method (minimum produced steam). Furthermore, exergy analysis is used for assessing processes in addition to energy analysis. It has been demonstrated that direct sequence provides better results than indirect sequence. Moreover, direct-thermal coupling is considered the most efficient process among the four investigated processes. It has been concluded that compared to the indirect process without heat integration, the direct-thermal coupling sequence can reduce energy consumption and exergy loss by 69% and 55%, respectively, as well as improve exergy efficiency by 9%.

Keywords


[1] Hernández, S., Segovia-Hernández, J.G., Rico-Ramírez, V., 2006, Thermodynamically equivalent distillation schemes to the Petlyuk column for ternary mixtures, Energy, 31(12), 2176–2183. https://doi.org/10.1016/j.energy.2005.10.007
[2] Galvin, J.B., Marashi, F., 1999, n-Pentane, Journal of Toxicology and Environmental Health, Part A, 58(1-2), 35-56. https://doi.org/10.1080/009841099157412
[3] Huang, C., 2008, Polyneuropathy induced by n-hexane intoxication in Taiwan. Acta Neurologica Taiwanica, 17(1), 3-10.
[4] Zhang, Q.S., Chen, S.J., Zhang, L., Cui, Q., Liu, Z.J., Wang, H.Y., 2016, Dynamic adsorption of n-heptane/methylhexane/2, 2, 4-trimethylpentane and refining of high purity n-heptane on UiO-66, Journal of Porous Materials, 23, 165–173. https://doi.org/10.1007/s10934-015-0067-x
[5] Sun, J., Wang, F., Ma, T., Gao, H., Wu, P., Liu, L., 2012, Energy and exergy analysis of a five-column methanol distillation scheme, Energy, 45(1), 696–703. https://doi.org/10.1016/j.energy.2012.07.022
[6] Xu, L., Gao, L., Yin, X., Yuan, X., 2018, Improving performance of dividing wall column using multistage vapor recompression with intermediate reboiler, Chemical Engineering Research and Design, 134, 382–391. https://doi.org/10.1016/j.cherd.2018.04.023
[7] Šulgan, B., Furda, P., Labovská, Z., 2023, Economic and environmental assessment of heat pump integration in thermally coupled hybrid separation, Chemical Engineering Journal, 471, 144298. https://doi.org/10.1016/j.cej.2023.144298
[8] Yang, A., Su, Y., Chien, I.L., Jin, S., Yan, C., Wei, S., Shen, W., 2019, Investigation of an energy-saving double-thermally coupled extractive distillation for separating ternary system benzene/toluene/cyclohexane, Energy, 186, 115756. https://doi.org/10.1016/j.energy.2019.07.086
[9] Babaie, O., Nasr Esfahany, M., 2013, The effects of feed splitting and heat integration in classical arrangements on cost minimization in separation of ternary mixture, Chemical Engineering and Processing: Process Intensification, 63, 37–43. https://doi.org/10.1016/j.cep.2012.10.007
[10] Engelien, H.K., Skogestad, S., 2005, Multi-effect distillation applied to an industrial case study, Chemical Engineering and Processing: Process Intensification, 44(8), 819–826. https://doi.org/10.1016/j.cep.2004.06.015
[11] Cui, C., Zhang, Q., Zhang, X., Sun, J., 2020, Eliminating the vapor split in dividing wall columns through controllable double liquid-only side-stream distillation configuration, Separation and Purification Technology, 242, 116837. https://doi.org/10.1016/j.seppur.2020.116837
[12] Wei, D., Li, G., Kong, L., Tan, X., 2021, Energy-saving investigation and techno-economic analysis of separation of ibuprofen sodium mother liquor using thermally coupled distillation, Journal of Environmental Chemical Engineering, 9(4), 105442. https://doi.org/10.1016/j.jece.2021.105442
[13] Cui, C., Zhang, X., Lyu, H., Wang, S., Sun, J., Qu, Y., Wu, W., Bo, C., Wong, D.S.H., Zhang, Q., 2021, Process intensification in ternary distillation via comparative grassroots and retrofit designs: A case study of distilling an industrial multicomponent C6 alkane mixture in caprolactam processing, Chemical Engineering and Processing-Process Intensification, 164, 108423. https://doi.org/10.1016/j.cep.2021.108423
[14] Javed, A., Hassan, A., Babar, M., Azhar, U., Riaz, A., Mujahid, R., Ahmad, T., Mubashir, M., Lim, H.R., Show, P.L., Khoo, K.S., 2022, A Comparison of the Exergy Efficiencies of Various Heat-Integrated Distillation Columns, Energies, 15(18), 6498. https://doi.org/10.3390/en15186498
[15] Kazemi, A., Mehrabani-Zeinabad, A., Beheshti, M., 2018, Evaluation of various heat pump assisted direct, indirect, Petlyuk and side stripper sequences for three-product separations, Chemical Engineering Science, 181, 19–35. https://doi.org/10.1016/j.ces.2018.02.007
[16] Bi, R., Yan, K., Yang, H., Tan, X., Xiang, S., 2023, Simulation and optimization of the thermally coupled reactive distillation column for producing toluene diisocynate, AIChE Journal, 69(1), e17648. https://doi.org/10.1002/aic.17648
[17] Sayadzadeh, M.E., Samani, M.R., Toghraie, D., Emami, S., Eftekhari, S.A., 2023, Numerical study on pollutant emissions characteristics and chemical and physical exergy analysis in Mild combustion, Energy. 278, Part B, 128001. https://doi.org/10.1016/j.energy.2023.128001
[18] Zhang, Z., Lou, C., 2023, Thermodynamics second-law analysis in an unsteady conduction and radiation heat transfer system with internal heat source, International Journal of Heat and Mass Transfer, 203, 123848. https://doi.org/10.1016/j.ijheatmasstransfer.2023.123848
[19] Huang, W., Liu, Y., Zheng, D., Chen, X., Yang, M., Li, Y., Li, X., 2022, Exergy-environment assessment for energy system: Distinguish the internal and total exergy loss, and modify the contribution of utility, Energy Conversion and Management, 251, 114975. https://doi.org/10.1016/j.enconman.2021.114975
[20] Ding, S., Guo, B., Hu, S., Gu, J., Yang, F., Li, Y., Dang, J., Liu, B., Ma, J., 2022, Analysis of the effect of characteristic parameters and operating conditions on exergy efficiency of alkaline water electrolyzer, Journal of Power Sources, 537, 231532. https://doi.org/10.1016/j.jpowsour.2022.231532
[21] Engelien, H.K., Skogestad, S., 2004, Selecting appropriate control variables for a heat-integrated distillation system with prefractionator, Computer Aided Chemical Engineering, 14, 407-412. https://doi.org/ 10.1016/S1570-7946(03)80149-9
[22] Smith, J.M., Van Ness, H., Abbott, M., Swihart, M., 2017, Introduction to Chemical Engineering Thermodynamics, 8th Edition, McGraw Hill.