## 4 Results and Discussion
### Selection of Solvents  
To select the appropriate solvent or mixture for the post-combustion CO\({}_{2}\) capture process, it was beneficial to combine the sensitivity analysis with the performance indices of \(R_{lost}\), \(C_{sol}\), \(\Delta\alpha\), \(Q_{rogen}\), and \(NEP\) at nominal conditions. In this context, a Pareto front of the sensitivity index \(\Omega_{3}(\zeta)\) at an appropriate \(\zeta\) for all the solvents with respect to the aforementioned performance criteria could be  
Figure 5: Sensitivity index \(\Omega_{3}(\zeta)\) versus the parametric variation magnitude coordinate \(\zeta\). implemented (Figures 6 and 7). The selected \(\zeta\)s were \(0.2\) and \(-0.15\) to include all the proposed mixtures. The minimization of the sensitivity index with respect to the minimization of \(R_{lost}\), \(C_{sol}\), \(\Delta\alpha\), \(Q_{green}\), and \(NEP\), along with the maximization of \(\Delta\alpha\), formed the respective Pareto fronts. Pareto optimal mixtures presented remarkably low sensitivity and good process performance from the nominal economic perspective. Figure 6: Pareto front between the sensitivity index \(\Omega_{3}(\zeta=0.2)\) and (**a**) \(R_{lost}\), (**b**) \(C_{sol}\), (**c**) \(\Delta\alpha\), (**d**) \(Q_{green}\), and (**e**) \(NEP\). Marks other than colored circles indicate undesirable solvents. Although some solvents exhibited a low \(R_{\mathit{lost}}\), such as AMP/PZ and MPA/MDEA, they exhibited high sensitivity under variable conditions. These mixtures were susceptible to exogenous changes, resulting in a higher overall cost of the process. Their use may demand higher expenses, either in capital costs or investments in advanced control systems to maintain the performance of the process at a high level. The developed Pareto fronts recommend solvents that had simultaneously low \(R_{\mathit{lost}}\) and \(\Omega_{3}(\zeta)\) in Figure 6a. Solvents that belonged to the Pareto front are represented with a cycle marker in a different color toward the left corner of Figure 6a. Solvents that are not part of Pareto front are represented with half-dashes of the same color since they belonged to the dominated set of solvents and should not be selected. AMP, DEA, and MDEA/DEA and both the phase-change solvents DEEA/MAPA and MCA formed the Pareto front combining both the minimization of two criteria and maintaining good nominal process performance in the corresponding index. Figure 6b illustrates the  
Figure 7: Pareto front between the sensitivity index \(\Omega_{3}(\zeta)=-0.15)\) and (**a**) \(R_{\mathit{lost}}\), (**b**) \(C_{\mathit{sol}}\), (**c**) \(\Delta\alpha\), (**d**) \(Q_{\mathit{regen}}\), and (**e**) \(\mathit{NEP}\). Marks other than colored circles indicate undesirable solvents. Pareto front between the sensitivity index and the solvent cost. The minimization of both indicators is desired. The optimal solvents were MEA, AMP, DEA, and MDEA/DEA. It is worth noting that three out of the four solvents were part of the previous Pareto front. This means that they maintained the process performance since they exhibited a tolerance against variations and they were simultaneously affordable with a low lost revenue from parasitic electricity. Figure 6c illustrates that DEEA/MAPA, MAPA, and MDEA/DEA combined flexibility in exogenous variations with high \(\Delta\alpha\). Note that MDEA/DEA continued to be part of the Pareto front. Higher regeneration energy means a higher cost and thus unprofitable plant units. AMP, DEA, MDEA/DEA, and both phase-change solvents DEEA/MAPA and MCA formed the Pareto front in Figure 6d. AMP, DEA, MDEA/DEA, and DEEA/MAPA constituted the Pareto front in Figure 6e. DEA and MDEA/DEA combined flexibility in exogenous variations with high energy efficiency performance. DEEA/MAPA was the phase-change solvent that exhibited the lowest net efficiency penalty among all solvents.