## 3 Results and Discussions
### Design of TCED Energy-Saving Processes  
As shown in Figure 2, two possibilities were identified for the heat recovery of the sensible heat from hot streams. The D3 water at 372.62 K can be mixed with B1 hot water at 380.7 K. Then, the resulting hot flow at 91.21 kmol/h and at 372.85 K, in Heater 1, could preheat the PC feed from 313.15 K to 327.10 K. In this context, the duty of Reboiler 1 (reboiler of PC) decreases from 3407 kWh to 3309 kWh, and its area decreases from 116 m\({}^{2}\) to 113 m\({}^{2}\). In other words, it was found that the energy saving for Reboiler 1 was around 2.9%. After Heater 1, the hot water stream reduces its temperature from 380.7 K to 323.15 K and can be directed towards a wastewater treatment plant.  
Also, in Figure 2, it can be observed that, in Heater 2, the sensible heat of the B3 hot solvent was recovered to preheat the EDC feed. The liquid feed (D1 flow at bubble point) can be partially vaporized. It is well known that a column with a partially vaporized feed will have a lower reboiler duty than a column with a boiling liquid feed. The results presented in Table 3 confirm the energy saving at the PC reboiler and the EDC reboiler by exploiting the sensible heat of the hot streams mentioned above. Moreover, the duty and area of the cooler will also decrease considerably.  
\begin{table}
\begin{tabular}{c c c c c} \hline
**Parameters** & & **SRC with PG** & **SRC with** & **SRC with** \\  & & **Solvent \({}^{*}\)** & **EG Solvent** & **DMSO Solvent** \\ \hline \multirow{3}{*}{B3 composition} & \multirow{3}{*}{molar} & Solvent & 100 & 100 & 100 \\  & & Water & 5 ppm & 5 ppm & 5 ppm \\  & & IPA & - & - & - \\ \hline NT3 & & & 17 & 15 & 16 \\ NF3 & & & 7 & 7 & 7 \\ RR3 & & & 1.9 & 0.6 & 1.4 \\ \hline Condenser 3, duty & kWh & 1928 & 1066 & 1599 \\ Condenser 3, area & m\({}^{2}\) & 38.70 & 21.74 & 32.77 \\ Water consumption to condenser 3 (a) & kg/h & 83,690.3 & 45,813.3 & 68,733.9 \\ Reboiler 3, duty & kWh & 2724 & 1514 & 1781 \\ Reboiler 3, area & m\({}^{2}\) & 94.11 & 65.00 & 66.65 \\ Steam consumption to reboiler 3 (b) & kg/h & 5592 & 3108 & 3656 \\ Cooler duty & kWh & 4418 & 1352 & 740 \\ Cooler area & m\({}^{2}\) & 101 & 29.7 & 16.6 \\ Water consumption to cooler a & kg/h & 189,954.02 & 58,110.33 & 31,791.5 \\ Diameter & m & 1.219 & 0.914 & 1.067 \\ \hline \end{tabular}  
* All data are from previous work [18]. (a) Inlet water temperature of 305.15 K, exit water temperature of 325.15 K.  
(b) Saturated steam at 3500 kPa.  
\end{table}
Table 2: _Cont._  
\begin{table}
\begin{tabular}{c c c c} \hline
**Values** & **PG Solvent \({}^{*}\)** & **EG Solvent** & **DMSO Solvent** \\ \hline Flowrate in B3, kmol/h & 569.81 & 209 & 133.8 \\ Temperature of B3, K & 464.93 & 474.9 & 468.9 \\ Temperature of B3 after Heater 2, K & 415.77 & 358.15 & 358.15 \\ D1 temperature before Heater 2, K & 355.86 & 355.86 & 355.86 \\ D1 temperature after Heater 2 & 386.25 & 358.36 & 358.36 \\  & & (vapor fraction of 1.00) & (vapor fraction of 0.66) \\ Reboiler 2 duty before heat recovery, kWh & 6639 & 3431 & 3205 \\ Reboiler 2 duty after heat recovery, kWh & 4664 & 2174 & 2522 \\ Reboiler 2 energy saving, \% & 29.75 & 36.64 & 21.31 \\ Cooler duty before heat recovery, kWh & 4418 & 1352 & 740 \\ Cooler duty after heat recovery, kWh & 2441 & 96.80 & 58.16 \\ Cooler energy saving, \% & 44.75 & 92.84 & 92.14 \\ \hline \end{tabular}  
* All data are from previous work [18].  
\end{table}
Table 3: Energy saving after heat recovery from hot streams.