## 5 Conclusions  
Processes powered by surplus electricity that would have been curtailed prove to be favorable from an environmental point of view. In this study, the focus was on post-combustion CO\({}_{2}\) capturing from flue gas vented from a standard power plant. A novel CC model that can be coupled with an electrolysis stage was developed. Such functionality is useful when both the CO\({}_{2}\) as well as the hydrogen products are sent to a methanol reactor. Relying on renewable energy poses challenges to the mode of operation. The possibility of transient operation of a post-combustion amine carbon capture process was examined by building a steady-state model and optimizing the units to capture 90% of the flue gas feed using 30 wt% amine solvent. Additional design data were required, and control loops were implemented and tuned to be able to simulate the process in a dynamic state.  
The capture rate in the absorber was controlled through manipulation of the lean amine flow rate, while the required CO\({}_{2}\) flowrate was determined by manipulating the reboiler duty. The exiting CO\({}_{2}\) purity was kept constant above 98% by controlling the condenser duty and stripping column conditions. Through controller set point tracking and disturbance rejection scenarios, the controller performance was tested. The absorber unit experienced quick responses when manipulating the required capture. The temperature took around 3 min to adjust while the desired capture rate was reached accurately in 12 min. The desorber experienced the slowest response where the temperature adjusted after around 12 min when a flue gas disturbance was initiated. The reboiler duty and sump level stage took around 6 h to adjust to a new steady-state condition. The study proves the feasibility of operating the carbon capture stage dynamically to follow the intermittent hydrogen production profile to feed a subsequent methanol reactor. A complete integrated model of the various stages, including the power plant is required, to give a complete overview of the effect of the carbon capture plant on the process. Storage facilities should be taken into consideration while designing the flexible operation to allow for rapid CO\({}_{2}\) production when ramping up from shutdown state as the rich solvent would be sent directly to the desorber providing greater flexibility of operation.  
Figure 14: Desorber parameters during hydrogen tracking scenario.  
**Author Contributions:** Conceptualization, M.M.; methodology, M.M.; software, M.M.; writing--original draft preparation, M.M.; visualization, M.M. and C.V.; validation, M.M. and C.V.; writing--review and editing, C.V., M.B.F. and E.Z.; funding acquisition, E.Z.; supervision, E.Z. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by German Federal Ministry of Economic Affairs and Energy under funding code 03 EIV051A, KEROSyN100 project.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Acknowledgments:** The authors gratefully acknowledge the partners of the KEROSyN100 consortium.  
**Conflicts of Interest:** The authors declare no conflict of interest.  
**Nomenclature**  
MEA & monoethanolamine  
FGD & Flue Gas Desulfurization  
ICAO & International Civil Aviation Organization  
TRL & Technology Readiness Level  
PZJ & Power-to-Jet  
CCS-U & Carbon Capture Storage and Utilization  
DCC & Direct Contact Cooler  
HTU & Height of Transfer Unit  
HETP & Height Equivalent to Theoretical Plate  
\(\eta\) & Isentropic efficiency  
PV & Process controlled variable  
OP & Manipulated (control) variable  
SP & Set point  
PCC & Post Combustion CO\({}_{2}\) Capture  
CC & Carbon Capture  
Figure A4: Aspen Plus® steady-state model flow sheet.  
Figure A5: Aspen Plus® Dynamics control scheme as described in Section 3.3.3.