## 3 Implementation
### Controlled Variables and Disturbance Scenarios  
The selected controlled variables in Y included all the parameters that were used as process performance indices. These were the reboiler duty \(Q_{\mathit{t}gen}\), the net efficiency energy penalty \(\mathit{NEP}\), the cyclic capacity \(\Delta\alpha\), the solvent mass flow rate \(m_{\mathit{am}}\), the solvent purchase cost \(C_{\mathit{sol}}\), and the lost revenue from parasitic electricity \(R_{\mathit{lost}}\). \(Q_{\mathit{t}gen}\) indicates the energy consumed in the stripper to regenerate the solvent. \(\mathit{NEP}\) is also an indicator of regeneration energy but takes into account the reboiler temperature and the stripper pressure. A higher pressure facilitates solvent regeneration, hence \(\mathit{NEP}\) is a more inclusive indicator than \(Q_{\mathit{t}gen}\). \(\Delta\alpha\) indicates the difference between the rich and the lean stream that exits and enters the absorber, hence it is associated with the absorber size. A higher \(\Delta\alpha\) facilitates the reaction and the necessary absorber size may be smaller. \(m_{\mathit{am}}\) is an indicator of the solvent amount required to achieve the desired absorption. It is used as an indicator of solvent consumption, i.e., solvents of lower flow rates are desirable. On the other hand, its use assumes that all solvents would be of the same cost, hence \(C_{\mathit{sol}}\) is a more inclusive indicator as it accounts for the different solvent prices. Finally, \(R_{\mathit{lost}}\) indicates the revenue that is lost in a power plant due to the need to consume energy to capture the emitted CO\({}_{2}\), which would otherwise be sold to generate revenues. Parameter \(\mathit{NEP}\) was calculated through a correlation proposed in [PERSON] et al. (2013) for stripper pressures of 1 and 1.5 bar. The former pressure was considered for MCA due to the availability of thermodynamic data, whereas the latter pressure was used in all other solvents. Parameter \(R_{\mathit{lost}}\) was calculated for a 620 MW coal-fired power plant. All the other data are available in [PERSON] et al. (2013). The parameters in \(\boldsymbol{E}\) that are subjected to variations are the following:  
* \(\varepsilon_{1}=y_{\mathit{in}}^{CO_{2}}\) is the content of CO\({}_{2}\) in the flue gas that enters the process. The nominal value is \(\varepsilon_{1}(0)=15\) vol\(\%\). * \(\varepsilon_{2}=\alpha_{\mathit{lean}}\) is the CO\({}_{2}\) loading of the absorption-desorption process after the stripper. Its value depends on the selected solvents and their physico-chemical characteristics. The nominal values for each solvent were reported by [PERSON] et al. (2013). \(\alpha_{\mathit{lean}}\) can be adjusted by the reboiler duty in the stripper, which subsequently has an impact on the performance criteria. * \(\varepsilon_{3}=T_{1}\) is the temperature of the inlet stream that enters the heat exchanger after the absorber. The nominal temperature is set to \(\varepsilon_{3}(0)=40\)\({}^{\circ}\)C. This can be adjusted by the possible cooling effort in the absorber and the amine flow rate in the system. The aforementioned parameters are selected because their change may affect the performance of the process. From a practical perspective, change in the CO\({}_{2}\) content of the flue gas may be attributed to a random disturbance or variability in the quality of the fuel or the operating regime of the power plant. Disturbance scenarios also involve a decrease or increase in \(\alpha_{\mathit{lean}}\) and increase or decrease in the temperature of the inlet stream. These variations create inclinations in the operating process and help to understand potential disturbance rejection compensations that are necessary for each solvent. The starting point for every considered scenario constitutes the nominal, \"desired\" point, as calculated by [PERSON] et al. (2013). The latter corresponds to operation in which there is a desired constant CO\({}_{2}\) capture rate at 90% with the \(Q_{\mathit{t}gen}\) at its lowest value.