## 4 Conclusions  
This paper presented a unique comparison between the separation and economic performances of EG, DMSO, and PG as extractive distillation solvents for IPA dehydration from its azeotrope with water. A conventional three-column extractive distillation (TCED) process was selected for comparison. The aim was to obtain the optimal operating and design parameters of the EDCs, which offer a distillate product with a minimum of 99.92 mol% IPA. For the SRC, the aim was to obtain very well-regenerated solvents (with only 5 ppm water), but also a water flow (as distillate) with a loss below 2 ppm solvent. We mention that the entire TCED process for the PG solvent case was carried out in a \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **TCED PG \({}^{*}\)** & **SH PG \({}^{*}\)** & **TCED EG** & **SH EG** & **TCED DMSO** & **SH DMSO** \\ \hline Capital cost (\({}^{\text{a}}\)), USD & 10,371,453 & 10,173,728 & 6,187,377 & 5,519,908 & 6,824,645 & 7,028,530 \\ \hline Capital cost saving (\% difference) & - & 1.90 & - & 10.79 & - & +2.9 \\ \hline Utility cost, USD/y & 3,236,748 & 2,726,795 & 2,119,247 & 1,758,288 & 2,148,365 & 1,923,793 \\ \hline Utility cost saving (\% difference) & - & 15.78 & - & 17.03 & - & 10.45 \\ \hline TAC (\({}^{\text{a}}\)), USD/y & 6,693,899 & 6,116,673 & 4,181,706 & 3,598,257 & 4,423,247 & 4,266,637 \\ \hline TAC saving (\% difference) & - & 8.69 & - & 13.95 & - & 3.54 \\ \hline \hline \end{tabular} \({}^{*}\) All data are from previous work [18]. \({}^{\text{(a)}}\) Includes the cost of purchasing the solvent (at the start-up of the plant).  
\end{table} 
Table 4: Results of economic evaluation for IPA/water dehydration by TCED processes with various solvents. previous study [18], and the data obtained were used for comparison with the EG and DMSO solvents. Also, the optimal operating parameters of the PC are common to the three investigated cases and are those previously obtained. In the second part of the work, the possibility of saving sensible heat from hot water streams (from the PC bottom flow and the distillate flow from the SRC) as well as the sensible heat of hot solvents was investigated. The proposed thermal integration process was assigned the SH flowsheet. The results of the economic evaluation show that both the TCED flowsheet and the improved SH flowsheet do not bring satisfactory results in the case of the DMSO solvent. Ethylene glycol seems to be a solvent with good results in the dehydration of IPA, which can reduce total annual costs by 13.95%, in the case of the heat integration process (SH) compared to the conventional TCED flowsheet. However, EG has a serious disadvantage: it is very toxic to human and animal health, pollutes the environment, is non-biodegradable, and has a high obtainment cost. All these disadvantages are overcome by PG. Consequently, the selection of propylene glycol (PG) or ethylene glycol (EG) as a solvent for the extractive distillation process in the dehydration of isopropyl alcohol (IPA) is left to the discretion of the developer. The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app15126430/s1](https://www.mdpi.com/article/10.3390/app15126430/s1)]([https://www.mdpi.com/article/10.3390/app15126430/s1](https://www.mdpi.com/article/10.3390/app15126430/s1)), Table S1. Binary interaction parameters of the NRTL thermodynamic systems. Table S2. Formulas and data utilized for the economic evaluation. Conceptualization, M.N. ; methodology, M.N. ; software, M.N. ; validation, D.-L.C. ; formal analysis, D.-L.C. ; investigation, M.N. ; resources, M.N. ; data curation, M.N. ; writing--original draft preparation, M.N. ; writing--review and editing, D.-L.C. ; visualization, M.N. ; supervision, D.-L.C. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.