TY  - CONF
AU  - Marinković, Dalibor
AU  - Nikolić, Daliborka
AU  - Seidel, Carsten
AU  - Seidel-Morgenstern, Andreas
AU  - Kienle, Achim
AU  - Petkovska, Menka
PY  - 2024
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/7459
AB  - The continuous industrial chemical processes are typically designed through steady-state conditions. Nevertheless, there is evidence that processes can be intensified by applying optimized forced periodic operation. Possible improvements in reactor performances caused by the implementation of forced periodic operation (FPO) can be successfully evaluated by applying a nonlinear frequency response (NFR) analysis, before experimental investigation. In this study, we will present the results of two case studies based on heterogeneously catalyzed methanol synthesis in a continuous stirred tank reactor (CSTR). The first is an isothermal case, and the second is a more complicated and more realistic, non-isothermal case.
PB  - Stockholm, Sweden : Scanditale AB
C3  - Energy Proceedings
T1  - Evaluation of possible improvements of forced periodically operated reactor in which methanol synthesis takes place – based on the Nonlinear Frequency Response analysis
IS  - VI
VL  - 43
DO  - 10.46855/energy-proceedings-11025
ER  - 

@conference{
author = "Marinković, Dalibor and Nikolić, Daliborka and Seidel, Carsten and Seidel-Morgenstern, Andreas and Kienle, Achim and Petkovska, Menka",
year = "2024",
abstract = "The continuous industrial chemical processes are typically designed through steady-state conditions. Nevertheless, there is evidence that processes can be intensified by applying optimized forced periodic operation. Possible improvements in reactor performances caused by the implementation of forced periodic operation (FPO) can be successfully evaluated by applying a nonlinear frequency response (NFR) analysis, before experimental investigation. In this study, we will present the results of two case studies based on heterogeneously catalyzed methanol synthesis in a continuous stirred tank reactor (CSTR). The first is an isothermal case, and the second is a more complicated and more realistic, non-isothermal case.",
publisher = "Stockholm, Sweden : Scanditale AB",
journal = "Energy Proceedings",
title = "Evaluation of possible improvements of forced periodically operated reactor in which methanol synthesis takes place – based on the Nonlinear Frequency Response analysis",
number = "VI",
volume = "43",
doi = "10.46855/energy-proceedings-11025"
}

Marinković, D., Nikolić, D., Seidel, C., Seidel-Morgenstern, A., Kienle, A.,& Petkovska, M.. (2024). Evaluation of possible improvements of forced periodically operated reactor in which methanol synthesis takes place – based on the Nonlinear Frequency Response analysis. in Energy Proceedings
Stockholm, Sweden : Scanditale AB., 43(VI).
https://doi.org/10.46855/energy-proceedings-11025

Marinković D, Nikolić D, Seidel C, Seidel-Morgenstern A, Kienle A, Petkovska M. Evaluation of possible improvements of forced periodically operated reactor in which methanol synthesis takes place – based on the Nonlinear Frequency Response analysis. in Energy Proceedings. 2024;43(VI).
doi:10.46855/energy-proceedings-11025 .

Marinković, Dalibor, Nikolić, Daliborka, Seidel, Carsten, Seidel-Morgenstern, Andreas, Kienle, Achim, Petkovska, Menka, "Evaluation of possible improvements of forced periodically operated reactor in which methanol synthesis takes place – based on the Nonlinear Frequency Response analysis" in Energy Proceedings, 43, no. VI (2024),
https://doi.org/10.46855/energy-proceedings-11025 . .

TY  - JOUR
AU  - Seidel, Carsten
AU  - Nikolić, Daliborka
AU  - Felischak, Matthias
AU  - Petkovska, Menka
AU  - Seidel-Morgenstern, Andreas
AU  - Kienle, Achim
PY  - 2022
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/5267
AB  - Methanol synthesis from synthesis gas with heterogeneous Cu/ZnO/Al2O3 catalysts in an isothermal gradientless reactor is described. In a theoretical study, the potential of forced periodic operation (FPO) for improving reactor performance in terms of methanol production rate and methanol yield is explored. The approach is based on a detailed kinetic model and combines nonlinear frequency response (NFR) analysis with rigorous numerical multi-objective optimization. Optimal steady-state operation is compared with optimal forced periodic operation for a given benchmark problem with and without inert nitrogen in the feed. Further, the significant influence of the saturation capacity of the solid phase on the dynamic behavior in response to step changes and periodic input modulations is studied.
PB  - John Wiley and Sons Inc
T2  - Chemical Engineering and Technology
T1  - Forced Periodic Operation of Methanol Synthesis in an Isothermal Gradientless Reactor
DO  - 10.1002/ceat.202200286
ER  - 

@article{
author = "Seidel, Carsten and Nikolić, Daliborka and Felischak, Matthias and Petkovska, Menka and Seidel-Morgenstern, Andreas and Kienle, Achim",
year = "2022",
abstract = "Methanol synthesis from synthesis gas with heterogeneous Cu/ZnO/Al2O3 catalysts in an isothermal gradientless reactor is described. In a theoretical study, the potential of forced periodic operation (FPO) for improving reactor performance in terms of methanol production rate and methanol yield is explored. The approach is based on a detailed kinetic model and combines nonlinear frequency response (NFR) analysis with rigorous numerical multi-objective optimization. Optimal steady-state operation is compared with optimal forced periodic operation for a given benchmark problem with and without inert nitrogen in the feed. Further, the significant influence of the saturation capacity of the solid phase on the dynamic behavior in response to step changes and periodic input modulations is studied.",
publisher = "John Wiley and Sons Inc",
journal = "Chemical Engineering and Technology",
title = "Forced Periodic Operation of Methanol Synthesis in an Isothermal Gradientless Reactor",
doi = "10.1002/ceat.202200286"
}

Seidel, C., Nikolić, D., Felischak, M., Petkovska, M., Seidel-Morgenstern, A.,& Kienle, A.. (2022). Forced Periodic Operation of Methanol Synthesis in an Isothermal Gradientless Reactor. in Chemical Engineering and Technology
John Wiley and Sons Inc..
https://doi.org/10.1002/ceat.202200286

Seidel C, Nikolić D, Felischak M, Petkovska M, Seidel-Morgenstern A, Kienle A. Forced Periodic Operation of Methanol Synthesis in an Isothermal Gradientless Reactor. in Chemical Engineering and Technology. 2022;.
doi:10.1002/ceat.202200286 .

Seidel, Carsten, Nikolić, Daliborka, Felischak, Matthias, Petkovska, Menka, Seidel-Morgenstern, Andreas, Kienle, Achim, "Forced Periodic Operation of Methanol Synthesis in an Isothermal Gradientless Reactor" in Chemical Engineering and Technology (2022),
https://doi.org/10.1002/ceat.202200286 . .

TY  - JOUR
AU  - Nikolic, Daliborka
AU  - Seidel, Carsten
AU  - Felischak, Matthias
AU  - Milicic, Tamara
AU  - Kienle, Achim
AU  - Seidel-Morgenstern, Andreas
AU  - Petkovska, Menka
PY  - 2022
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4989
AB  - In this two-part paper a comprehensive study of the potential to improve performance criteria of a methanol synthesis reactor through forced periodical operations is presented. The study uses the Nonlinear Frequency Response method, a powerful analytical and approximate tool which gives an answer whether and under which conditions certain periodic operation would lead to improvement of process performance. To demonstrate the method, isothermal and isobaric methanol synthesis in a lab-scale CSTR is considered. In Part I, the analysis is performed for single input modulations. Partial pressures of each reactant in the feed stream and the total inlet volumetric flow-rate are considered as possible modulated inputs. The results show that modulations of single inputs essentially do not provide potential for significant improvements. In Part II, the study will be extended to analysis of periodic operations with simultaneous modulations of two inputs and conditions offering significant performance enhancements will be identified.
T2  - Chemical Engineering Science
T1  - Forced periodic operations of a chemical reactor for methanol synthesis - The search for the best scenario based on Nonlinear Frequency Response Method. Part I Single input modulations
VL  - 248
DO  - 10.1016/j.ces.2021.117134
ER  - 

@article{
author = "Nikolic, Daliborka and Seidel, Carsten and Felischak, Matthias and Milicic, Tamara and Kienle, Achim and Seidel-Morgenstern, Andreas and Petkovska, Menka",
year = "2022",
abstract = "In this two-part paper a comprehensive study of the potential to improve performance criteria of a methanol synthesis reactor through forced periodical operations is presented. The study uses the Nonlinear Frequency Response method, a powerful analytical and approximate tool which gives an answer whether and under which conditions certain periodic operation would lead to improvement of process performance. To demonstrate the method, isothermal and isobaric methanol synthesis in a lab-scale CSTR is considered. In Part I, the analysis is performed for single input modulations. Partial pressures of each reactant in the feed stream and the total inlet volumetric flow-rate are considered as possible modulated inputs. The results show that modulations of single inputs essentially do not provide potential for significant improvements. In Part II, the study will be extended to analysis of periodic operations with simultaneous modulations of two inputs and conditions offering significant performance enhancements will be identified.",
journal = "Chemical Engineering Science",
title = "Forced periodic operations of a chemical reactor for methanol synthesis - The search for the best scenario based on Nonlinear Frequency Response Method. Part I Single input modulations",
volume = "248",
doi = "10.1016/j.ces.2021.117134"
}

Nikolic, D., Seidel, C., Felischak, M., Milicic, T., Kienle, A., Seidel-Morgenstern, A.,& Petkovska, M.. (2022). Forced periodic operations of a chemical reactor for methanol synthesis - The search for the best scenario based on Nonlinear Frequency Response Method. Part I Single input modulations. in Chemical Engineering Science, 248.
https://doi.org/10.1016/j.ces.2021.117134

Nikolic D, Seidel C, Felischak M, Milicic T, Kienle A, Seidel-Morgenstern A, Petkovska M. Forced periodic operations of a chemical reactor for methanol synthesis - The search for the best scenario based on Nonlinear Frequency Response Method. Part I Single input modulations. in Chemical Engineering Science. 2022;248.
doi:10.1016/j.ces.2021.117134 .

Nikolic, Daliborka, Seidel, Carsten, Felischak, Matthias, Milicic, Tamara, Kienle, Achim, Seidel-Morgenstern, Andreas, Petkovska, Menka, "Forced periodic operations of a chemical reactor for methanol synthesis - The search for the best scenario based on Nonlinear Frequency Response Method. Part I Single input modulations" in Chemical Engineering Science, 248 (2022),
https://doi.org/10.1016/j.ces.2021.117134 . .

TY  - JOUR
AU  - Nikolic, Daliborka
AU  - Seidel, Carsten
AU  - Felischak, Matthias
AU  - Milicic, Tamara
AU  - Kienle, Achim
AU  - Seidel-Morgenstern, Andreas
AU  - Petkovska, Menka
PY  - 2022
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4973
AB  - The analysis of the potential to improve performance of a methanol synthesis reactor through forced periodical operations by Nonlinear Frequency Response method is presented. The methanol synthesis in an isothermal and isobaric lab-scale CSTR is considered. First, the analysis was performed for single input modulations (in Part I), which showed that significant improvements can't be achieved. Here, the study is extended to analysis of simultaneous modulations of two inputs. All possible input combi-nations (6 cases) are analysed and the optimal forcing parameters, maximizing the time-average metha-nol production, were determined. For all combinations the improvement is possible, but for some cases it is not significant. The highest improvement is predicted for simultaneous modulation of the inlet partial pressure of CO and the inlet volumetric flow rate. This case, for which it is possible to achieve up to 33.51 % of methanol production, is analysed it detail and optimized using multi-objective optimization.
T2  - Chemical Engineering Science
T1  - Forced periodic operations of a chemical reactor for methanol synthesis - The search for the best scenario based on Nonlinear Frequency Response Method. Part II Simultaneous modulation of two inputs
VL  - 248
DO  - 10.1016/j.ces.2021.117133
ER  - 

@article{
author = "Nikolic, Daliborka and Seidel, Carsten and Felischak, Matthias and Milicic, Tamara and Kienle, Achim and Seidel-Morgenstern, Andreas and Petkovska, Menka",
year = "2022",
abstract = "The analysis of the potential to improve performance of a methanol synthesis reactor through forced periodical operations by Nonlinear Frequency Response method is presented. The methanol synthesis in an isothermal and isobaric lab-scale CSTR is considered. First, the analysis was performed for single input modulations (in Part I), which showed that significant improvements can't be achieved. Here, the study is extended to analysis of simultaneous modulations of two inputs. All possible input combi-nations (6 cases) are analysed and the optimal forcing parameters, maximizing the time-average metha-nol production, were determined. For all combinations the improvement is possible, but for some cases it is not significant. The highest improvement is predicted for simultaneous modulation of the inlet partial pressure of CO and the inlet volumetric flow rate. This case, for which it is possible to achieve up to 33.51 % of methanol production, is analysed it detail and optimized using multi-objective optimization.",
journal = "Chemical Engineering Science",
title = "Forced periodic operations of a chemical reactor for methanol synthesis - The search for the best scenario based on Nonlinear Frequency Response Method. Part II Simultaneous modulation of two inputs",
volume = "248",
doi = "10.1016/j.ces.2021.117133"
}

Nikolic, D., Seidel, C., Felischak, M., Milicic, T., Kienle, A., Seidel-Morgenstern, A.,& Petkovska, M.. (2022). Forced periodic operations of a chemical reactor for methanol synthesis - The search for the best scenario based on Nonlinear Frequency Response Method. Part II Simultaneous modulation of two inputs. in Chemical Engineering Science, 248.
https://doi.org/10.1016/j.ces.2021.117133

Nikolic D, Seidel C, Felischak M, Milicic T, Kienle A, Seidel-Morgenstern A, Petkovska M. Forced periodic operations of a chemical reactor for methanol synthesis - The search for the best scenario based on Nonlinear Frequency Response Method. Part II Simultaneous modulation of two inputs. in Chemical Engineering Science. 2022;248.
doi:10.1016/j.ces.2021.117133 .

Nikolic, Daliborka, Seidel, Carsten, Felischak, Matthias, Milicic, Tamara, Kienle, Achim, Seidel-Morgenstern, Andreas, Petkovska, Menka, "Forced periodic operations of a chemical reactor for methanol synthesis - The search for the best scenario based on Nonlinear Frequency Response Method. Part II Simultaneous modulation of two inputs" in Chemical Engineering Science, 248 (2022),
https://doi.org/10.1016/j.ces.2021.117133 . .

TY  - JOUR
AU  - Felischak, Matthias
AU  - Kaps, Lothar
AU  - Hamel, Christof
AU  - Nikolic, Daliborka
AU  - Petkovska, Menka
AU  - Seidel-Morgenstern, Andreas
PY  - 2022
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4995
T2  - Chemical Engineering Journal
T1  - Analysis and experimental demonstration of forced periodic operation of an adiabatic stirred tank reactor: Simultaneous modulation of inlet concentration and total flow-rate (vol 410, 128197, 2021)
VL  - 430
DO  - 10.1016/j.cej.2021.132930
ER  - 

@article{
author = "Felischak, Matthias and Kaps, Lothar and Hamel, Christof and Nikolic, Daliborka and Petkovska, Menka and Seidel-Morgenstern, Andreas",
year = "2022",
journal = "Chemical Engineering Journal",
title = "Analysis and experimental demonstration of forced periodic operation of an adiabatic stirred tank reactor: Simultaneous modulation of inlet concentration and total flow-rate (vol 410, 128197, 2021)",
volume = "430",
doi = "10.1016/j.cej.2021.132930"
}

Felischak, M., Kaps, L., Hamel, C., Nikolic, D., Petkovska, M.,& Seidel-Morgenstern, A.. (2022). Analysis and experimental demonstration of forced periodic operation of an adiabatic stirred tank reactor: Simultaneous modulation of inlet concentration and total flow-rate (vol 410, 128197, 2021). in Chemical Engineering Journal, 430.
https://doi.org/10.1016/j.cej.2021.132930

Felischak M, Kaps L, Hamel C, Nikolic D, Petkovska M, Seidel-Morgenstern A. Analysis and experimental demonstration of forced periodic operation of an adiabatic stirred tank reactor: Simultaneous modulation of inlet concentration and total flow-rate (vol 410, 128197, 2021). in Chemical Engineering Journal. 2022;430.
doi:10.1016/j.cej.2021.132930 .

Felischak, Matthias, Kaps, Lothar, Hamel, Christof, Nikolic, Daliborka, Petkovska, Menka, Seidel-Morgenstern, Andreas, "Analysis and experimental demonstration of forced periodic operation of an adiabatic stirred tank reactor: Simultaneous modulation of inlet concentration and total flow-rate (vol 410, 128197, 2021)" in Chemical Engineering Journal, 430 (2022),
https://doi.org/10.1016/j.cej.2021.132930 . .

TY  - JOUR
AU  - Seidel, Carsten
AU  - Nikolic, Daliborka
AU  - Felischak, Matthias
AU  - Petkovska, Menka
AU  - Seidel-Morgenstern, Andreas
AU  - Kienle, Achim
PY  - 2021
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4938
AB  - Traditionally, methanol is produced in large amounts from synthesis gas with heterogeneous Cu/ZnO/Al2O3 catalysts under steady state conditions. In this paper, the potential of alternative forced periodic operation modes is studied using numerical optimization. The focus is a well-mixed isothermal reactor with two periodic inputs, namely, CO concentration in the feed and total feed flow rate. Exploiting a detailed kinetic model which also describes the dynamics of the catalyst, a sequential NLP optimization approach is applied to compare optimal steady state solutions with optimal periodic regimes. Periodic solutions are calculated using dynamic optimization with a periodicity constraint. The NLP optimization is embedded in a multi-objective optimization framework to optimize the process with respect to two objective functions and generate the corresponding Pareto fronts. The first objective is the methanol outlet flow rate. The second objective is the methanol yield based on the total carbon in the feed. Additional constraints arising from the complex methanol reaction and the practical limitations are introduced step by step. The results show that significant improvements for both objective functions are possible through periodic forcing of the two inputs considered here.
T2  - Processes
T1  - Optimization of Methanol Synthesis under Forced Periodic Operation
IS  - 5
VL  - 9
DO  - 10.3390/pr9050872
ER  - 

@article{
author = "Seidel, Carsten and Nikolic, Daliborka and Felischak, Matthias and Petkovska, Menka and Seidel-Morgenstern, Andreas and Kienle, Achim",
year = "2021",
abstract = "Traditionally, methanol is produced in large amounts from synthesis gas with heterogeneous Cu/ZnO/Al2O3 catalysts under steady state conditions. In this paper, the potential of alternative forced periodic operation modes is studied using numerical optimization. The focus is a well-mixed isothermal reactor with two periodic inputs, namely, CO concentration in the feed and total feed flow rate. Exploiting a detailed kinetic model which also describes the dynamics of the catalyst, a sequential NLP optimization approach is applied to compare optimal steady state solutions with optimal periodic regimes. Periodic solutions are calculated using dynamic optimization with a periodicity constraint. The NLP optimization is embedded in a multi-objective optimization framework to optimize the process with respect to two objective functions and generate the corresponding Pareto fronts. The first objective is the methanol outlet flow rate. The second objective is the methanol yield based on the total carbon in the feed. Additional constraints arising from the complex methanol reaction and the practical limitations are introduced step by step. The results show that significant improvements for both objective functions are possible through periodic forcing of the two inputs considered here.",
journal = "Processes",
title = "Optimization of Methanol Synthesis under Forced Periodic Operation",
number = "5",
volume = "9",
doi = "10.3390/pr9050872"
}

Seidel, C., Nikolic, D., Felischak, M., Petkovska, M., Seidel-Morgenstern, A.,& Kienle, A.. (2021). Optimization of Methanol Synthesis under Forced Periodic Operation. in Processes, 9(5).
https://doi.org/10.3390/pr9050872

Seidel C, Nikolic D, Felischak M, Petkovska M, Seidel-Morgenstern A, Kienle A. Optimization of Methanol Synthesis under Forced Periodic Operation. in Processes. 2021;9(5).
doi:10.3390/pr9050872 .

Seidel, Carsten, Nikolic, Daliborka, Felischak, Matthias, Petkovska, Menka, Seidel-Morgenstern, Andreas, Kienle, Achim, "Optimization of Methanol Synthesis under Forced Periodic Operation" in Processes, 9, no. 5 (2021),
https://doi.org/10.3390/pr9050872 . .

TY  - JOUR
AU  - Felischak, Matthias
AU  - Kaps, Lothar
AU  - Hamel, Christof
AU  - Nikolic, Daliborka
AU  - Petkovska, Menka
AU  - Seidel-Morgenstern, Andreas
PY  - 2021
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4927
AB  - It is well known, that forced periodic operation possesses the potential for process improvements. Nevertheless, only a small number of applications is reported, due to complex realization, limited predictability and high inertia of larger units. Nonlinear frequency response (NFR) analysis has proven to predict efficiently time-averaged performance of reactor effluent streams originating from forced periodic changes of one or several input(s). Focus of this paper was an experimental demonstration of forced periodic operation applied to the hydrolysis of acetic anhydride carried out in an adiabatic CSTR. Theoretical results provided a guideline for experiments exploiting simultaneous sinusoidal modulations of the anhydride inlet concentration and the total volumetric flow-rate. Influences of the forcing parameters (amplitudes and the phase difference) were also studied. Confirming the predictions of NFR analysis a significantly higher time-averaged product yields were experimentally achieved compared to conventional steady-state operation with simultaneous modulation of two inputs using an optimized phase shift.
T2  - Chemical Engineering Journal
T1  - Analysis and experimental demonstration of forced periodic operation of an adiabatic stirred tank reactor: Simultaneous modulation of inlet concentration and total flow-rate
VL  - 410
DO  - 10.1016/j.cej.2020.128197
ER  - 

@article{
author = "Felischak, Matthias and Kaps, Lothar and Hamel, Christof and Nikolic, Daliborka and Petkovska, Menka and Seidel-Morgenstern, Andreas",
year = "2021",
abstract = "It is well known, that forced periodic operation possesses the potential for process improvements. Nevertheless, only a small number of applications is reported, due to complex realization, limited predictability and high inertia of larger units. Nonlinear frequency response (NFR) analysis has proven to predict efficiently time-averaged performance of reactor effluent streams originating from forced periodic changes of one or several input(s). Focus of this paper was an experimental demonstration of forced periodic operation applied to the hydrolysis of acetic anhydride carried out in an adiabatic CSTR. Theoretical results provided a guideline for experiments exploiting simultaneous sinusoidal modulations of the anhydride inlet concentration and the total volumetric flow-rate. Influences of the forcing parameters (amplitudes and the phase difference) were also studied. Confirming the predictions of NFR analysis a significantly higher time-averaged product yields were experimentally achieved compared to conventional steady-state operation with simultaneous modulation of two inputs using an optimized phase shift.",
journal = "Chemical Engineering Journal",
title = "Analysis and experimental demonstration of forced periodic operation of an adiabatic stirred tank reactor: Simultaneous modulation of inlet concentration and total flow-rate",
volume = "410",
doi = "10.1016/j.cej.2020.128197"
}

Felischak, M., Kaps, L., Hamel, C., Nikolic, D., Petkovska, M.,& Seidel-Morgenstern, A.. (2021). Analysis and experimental demonstration of forced periodic operation of an adiabatic stirred tank reactor: Simultaneous modulation of inlet concentration and total flow-rate. in Chemical Engineering Journal, 410.
https://doi.org/10.1016/j.cej.2020.128197

Felischak M, Kaps L, Hamel C, Nikolic D, Petkovska M, Seidel-Morgenstern A. Analysis and experimental demonstration of forced periodic operation of an adiabatic stirred tank reactor: Simultaneous modulation of inlet concentration and total flow-rate. in Chemical Engineering Journal. 2021;410.
doi:10.1016/j.cej.2020.128197 .

Felischak, Matthias, Kaps, Lothar, Hamel, Christof, Nikolic, Daliborka, Petkovska, Menka, Seidel-Morgenstern, Andreas, "Analysis and experimental demonstration of forced periodic operation of an adiabatic stirred tank reactor: Simultaneous modulation of inlet concentration and total flow-rate" in Chemical Engineering Journal, 410 (2021),
https://doi.org/10.1016/j.cej.2020.128197 . .

TY  - JOUR
AU  - Vidakovic-Koch, Tanja
AU  - Milicic, Tamara
AU  - Živković, Luka
AU  - Chan, Hoon Seng
AU  - Krewer, Ulrike
AU  - Petkovska, Menka
PY  - 2021
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4842
AB  - The nonlinear frequency response analysis (NFRA) can be seen as an extension of electrochemical impedance spectroscopy. NFRA gives a full and detailed representation of the system response and can establish a connection between model parameters and the experimentally observed phenomena. In this article, different theoretical NFRA approaches and the most recent application examples are discussed. A simple electrochemical example is used to showcase the benefits and disadvantages of analyzing the system response by using different approaches. In addition, it was shown how to extract experimental harmonic values and analyze them.
T2  - Current Opinion in Electrochemistry
T1  - Nonlinear frequency response analysis: a recent review and perspectives
VL  - 30
DO  - 10.1016/j.coelec.2021.100851
ER  - 

@article{
author = "Vidakovic-Koch, Tanja and Milicic, Tamara and Živković, Luka and Chan, Hoon Seng and Krewer, Ulrike and Petkovska, Menka",
year = "2021",
abstract = "The nonlinear frequency response analysis (NFRA) can be seen as an extension of electrochemical impedance spectroscopy. NFRA gives a full and detailed representation of the system response and can establish a connection between model parameters and the experimentally observed phenomena. In this article, different theoretical NFRA approaches and the most recent application examples are discussed. A simple electrochemical example is used to showcase the benefits and disadvantages of analyzing the system response by using different approaches. In addition, it was shown how to extract experimental harmonic values and analyze them.",
journal = "Current Opinion in Electrochemistry",
title = "Nonlinear frequency response analysis: a recent review and perspectives",
volume = "30",
doi = "10.1016/j.coelec.2021.100851"
}

Vidakovic-Koch, T., Milicic, T., Živković, L., Chan, H. S., Krewer, U.,& Petkovska, M.. (2021). Nonlinear frequency response analysis: a recent review and perspectives. in Current Opinion in Electrochemistry, 30.
https://doi.org/10.1016/j.coelec.2021.100851

Vidakovic-Koch T, Milicic T, Živković L, Chan HS, Krewer U, Petkovska M. Nonlinear frequency response analysis: a recent review and perspectives. in Current Opinion in Electrochemistry. 2021;30.
doi:10.1016/j.coelec.2021.100851 .

Vidakovic-Koch, Tanja, Milicic, Tamara, Živković, Luka, Chan, Hoon Seng, Krewer, Ulrike, Petkovska, Menka, "Nonlinear frequency response analysis: a recent review and perspectives" in Current Opinion in Electrochemistry, 30 (2021),
https://doi.org/10.1016/j.coelec.2021.100851 . .

TY  - JOUR
AU  - Nikačević, Nikola
AU  - Todić, Branislav
AU  - Mandić, Miloš
AU  - Petkovska, Menka
AU  - Bukur, Dragomir B.
PY  - 2020
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4453
AB  - One-dimensional pseudo-homogenous dynamic reactor model, incorporating detailed Fischer-Tropsch kinetics, was applied in a theoretical analysis of forced periodic operations. A milli-scale fixed-bed reactor was analyzed, using design and operation parameters, obtained previously in a steady-state optimization. Dynamic optimization and NLP methods were utilized to obtain optimal values of amplitude(s), frequency and phase shift(s) of sine-wave variation of inputs, around the corresponding optimal steady-state values, which maximize the productivity of C5+ hydrocarbons. Inlet variables that were modulated are: coolant temperature, reactants molar ratio, mass flow rate and pressure. In addition to the single input forcing, simultaneous modulations of multiple inputs were also considered, with combinations of the listed inlet variables. Among the single input cases, periodic variation of the coolant temperature resulted in the highest relative improvement of C5+, productivity by 30%. Multiple inputs forcing showed additional potential for improvement, resulting in relative c(5+) productivity increase of 52% for synchronized modulation of the coolant temperature, reactants molar ratio and mass flow rate. However, the increase in C5+ productivity is accompanied with relative increase in methane selectivity of 22-33% (relative to the steady-state value). The results suggest that, in the case of multiple input variations with high amplitudes, modulation of the inlet reactants molar ratio mainly contributes to the increase of CO conversion (e.g. reaction rate), the coolant temperature forcing slightly increases selectivity towards the desirable higher hydrocarbons (C5+), while the variation of the inlet mass flow rate enables better reaction temperature control and prevents a thermal runway.
PB  - Elsevier, Amsterdam
T2  - Catalysis Today
T1  - Optimization of forced periodic operations in milli-scale fixed bed reactor for Fischer-Tropsch synthesis
EP  - 164
SP  - 156
VL  - 343
DO  - 10.1016/j.cattod.2018.12.032
ER  - 

@article{
author = "Nikačević, Nikola and Todić, Branislav and Mandić, Miloš and Petkovska, Menka and Bukur, Dragomir B.",
year = "2020",
abstract = "One-dimensional pseudo-homogenous dynamic reactor model, incorporating detailed Fischer-Tropsch kinetics, was applied in a theoretical analysis of forced periodic operations. A milli-scale fixed-bed reactor was analyzed, using design and operation parameters, obtained previously in a steady-state optimization. Dynamic optimization and NLP methods were utilized to obtain optimal values of amplitude(s), frequency and phase shift(s) of sine-wave variation of inputs, around the corresponding optimal steady-state values, which maximize the productivity of C5+ hydrocarbons. Inlet variables that were modulated are: coolant temperature, reactants molar ratio, mass flow rate and pressure. In addition to the single input forcing, simultaneous modulations of multiple inputs were also considered, with combinations of the listed inlet variables. Among the single input cases, periodic variation of the coolant temperature resulted in the highest relative improvement of C5+, productivity by 30%. Multiple inputs forcing showed additional potential for improvement, resulting in relative c(5+) productivity increase of 52% for synchronized modulation of the coolant temperature, reactants molar ratio and mass flow rate. However, the increase in C5+ productivity is accompanied with relative increase in methane selectivity of 22-33% (relative to the steady-state value). The results suggest that, in the case of multiple input variations with high amplitudes, modulation of the inlet reactants molar ratio mainly contributes to the increase of CO conversion (e.g. reaction rate), the coolant temperature forcing slightly increases selectivity towards the desirable higher hydrocarbons (C5+), while the variation of the inlet mass flow rate enables better reaction temperature control and prevents a thermal runway.",
publisher = "Elsevier, Amsterdam",
journal = "Catalysis Today",
title = "Optimization of forced periodic operations in milli-scale fixed bed reactor for Fischer-Tropsch synthesis",
pages = "164-156",
volume = "343",
doi = "10.1016/j.cattod.2018.12.032"
}

Nikačević, N., Todić, B., Mandić, M., Petkovska, M.,& Bukur, D. B.. (2020). Optimization of forced periodic operations in milli-scale fixed bed reactor for Fischer-Tropsch synthesis. in Catalysis Today
Elsevier, Amsterdam., 343, 156-164.
https://doi.org/10.1016/j.cattod.2018.12.032

Nikačević N, Todić B, Mandić M, Petkovska M, Bukur DB. Optimization of forced periodic operations in milli-scale fixed bed reactor for Fischer-Tropsch synthesis. in Catalysis Today. 2020;343:156-164.
doi:10.1016/j.cattod.2018.12.032 .

Nikačević, Nikola, Todić, Branislav, Mandić, Miloš, Petkovska, Menka, Bukur, Dragomir B., "Optimization of forced periodic operations in milli-scale fixed bed reactor for Fischer-Tropsch synthesis" in Catalysis Today, 343 (2020):156-164,
https://doi.org/10.1016/j.cattod.2018.12.032 . .

TY  - JOUR
AU  - Kaps, Lothar
AU  - Felischak, Matthias
AU  - Nikolić, Daliborka
AU  - Petkovska, Menka
AU  - Hamel, Christof
AU  - Seidel-Morgenstern, Andreas
PY  - 2020
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4407
AB  - Continuous chemical reactors are mostly operated under steady-state conditions. However, theoretical studies reveal that forced periodic operation (FPO) can lead to better performance. To predict and optimize FPO, the nonlinear frequency response (NFR) method provides an analytical approach. The presented work is focused on providing theoretical and experimental results devoted to demonstrating both the potential of forced periodic operation and the strength of the NFR method to identify suitable operating conditions. The hydrolysis of acetic anhydride is studied experimentally as a model reaction applying an adiabatic continuous stirred tank reactor (CSTR).
PB  - Wiley-VCH
T2  - Chemie Ingenieur Technik
T1  - Forced periodic reactor operation: Analysis of process and forcing parameters exploiting the nonlinear frequency response method
EP  - 1346
IS  - 9
SP  - 1346
VL  - 92
DO  - 10.1002/cite.202055082
ER  - 

@article{
author = "Kaps, Lothar and Felischak, Matthias and Nikolić, Daliborka and Petkovska, Menka and Hamel, Christof and Seidel-Morgenstern, Andreas",
year = "2020",
abstract = "Continuous chemical reactors are mostly operated under steady-state conditions. However, theoretical studies reveal that forced periodic operation (FPO) can lead to better performance. To predict and optimize FPO, the nonlinear frequency response (NFR) method provides an analytical approach. The presented work is focused on providing theoretical and experimental results devoted to demonstrating both the potential of forced periodic operation and the strength of the NFR method to identify suitable operating conditions. The hydrolysis of acetic anhydride is studied experimentally as a model reaction applying an adiabatic continuous stirred tank reactor (CSTR).",
publisher = "Wiley-VCH",
journal = "Chemie Ingenieur Technik",
title = "Forced periodic reactor operation: Analysis of process and forcing parameters exploiting the nonlinear frequency response method",
pages = "1346-1346",
number = "9",
volume = "92",
doi = "10.1002/cite.202055082"
}

Kaps, L., Felischak, M., Nikolić, D., Petkovska, M., Hamel, C.,& Seidel-Morgenstern, A.. (2020). Forced periodic reactor operation: Analysis of process and forcing parameters exploiting the nonlinear frequency response method. in Chemie Ingenieur Technik
Wiley-VCH., 92(9), 1346-1346.
https://doi.org/10.1002/cite.202055082

Kaps L, Felischak M, Nikolić D, Petkovska M, Hamel C, Seidel-Morgenstern A. Forced periodic reactor operation: Analysis of process and forcing parameters exploiting the nonlinear frequency response method. in Chemie Ingenieur Technik. 2020;92(9):1346-1346.
doi:10.1002/cite.202055082 .

Kaps, Lothar, Felischak, Matthias, Nikolić, Daliborka, Petkovska, Menka, Hamel, Christof, Seidel-Morgenstern, Andreas, "Forced periodic reactor operation: Analysis of process and forcing parameters exploiting the nonlinear frequency response method" in Chemie Ingenieur Technik, 92, no. 9 (2020):1346-1346,
https://doi.org/10.1002/cite.202055082 . .

TY  - JOUR
AU  - Živković, Luka
AU  - Milić, Viktor
AU  - Vidaković-Koch, Tanja
AU  - Petkovska, Menka
PY  - 2020
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4439
AB  - The dynamic optimization of promising forced periodic processes has always been limited by time-consuming and expensive numerical calculations. The Nonlinear Frequency Response (NFR) method removes these limitations by providing excellent estimates of any process performance criteria of interest. Recently, the NFR method evolved to the computer-aided NFR method (cNFR) through a user-friendly software application for the automatic derivation of the functions necessary to estimate process improvement. By combining the cNFR method with standard multi-objective optimization (MOO) techniques, we developed a unique cNFR-MOO methodology for the optimization of periodic operations in the frequency domain. Since the objective functions are defined with entirely algebraic expressions, the dynamic optimization of forced periodic operations is extraordinarily fast. All optimization parameters, i.e., the steady-state point and the forcing parameters (frequency, amplitudes, and phase difference), are determined rapidly in one step. This gives the ability to find an optimal periodic operation around a sub-optimal steady-state point. The cNFR-MOO methodology was applied to two examples and is shown as an efficient and powerful tool for finding the best forced periodic operation. In both examples, the cNFR-MOO methodology gave conditions that could greatly enhance a process that is normally operated in a steady state.
PB  - MDPI, Basel
T2  - Processes
T1  - Rapid Multi-Objective Optimization of Periodically Operated Processes Based on the Computer-Aided Nonlinear Frequency Response Method
IS  - 11
VL  - 8
DO  - 10.3390/pr8111357
ER  - 

@article{
author = "Živković, Luka and Milić, Viktor and Vidaković-Koch, Tanja and Petkovska, Menka",
year = "2020",
abstract = "The dynamic optimization of promising forced periodic processes has always been limited by time-consuming and expensive numerical calculations. The Nonlinear Frequency Response (NFR) method removes these limitations by providing excellent estimates of any process performance criteria of interest. Recently, the NFR method evolved to the computer-aided NFR method (cNFR) through a user-friendly software application for the automatic derivation of the functions necessary to estimate process improvement. By combining the cNFR method with standard multi-objective optimization (MOO) techniques, we developed a unique cNFR-MOO methodology for the optimization of periodic operations in the frequency domain. Since the objective functions are defined with entirely algebraic expressions, the dynamic optimization of forced periodic operations is extraordinarily fast. All optimization parameters, i.e., the steady-state point and the forcing parameters (frequency, amplitudes, and phase difference), are determined rapidly in one step. This gives the ability to find an optimal periodic operation around a sub-optimal steady-state point. The cNFR-MOO methodology was applied to two examples and is shown as an efficient and powerful tool for finding the best forced periodic operation. In both examples, the cNFR-MOO methodology gave conditions that could greatly enhance a process that is normally operated in a steady state.",
publisher = "MDPI, Basel",
journal = "Processes",
title = "Rapid Multi-Objective Optimization of Periodically Operated Processes Based on the Computer-Aided Nonlinear Frequency Response Method",
number = "11",
volume = "8",
doi = "10.3390/pr8111357"
}

Živković, L., Milić, V., Vidaković-Koch, T.,& Petkovska, M.. (2020). Rapid Multi-Objective Optimization of Periodically Operated Processes Based on the Computer-Aided Nonlinear Frequency Response Method. in Processes
MDPI, Basel., 8(11).
https://doi.org/10.3390/pr8111357

Živković L, Milić V, Vidaković-Koch T, Petkovska M. Rapid Multi-Objective Optimization of Periodically Operated Processes Based on the Computer-Aided Nonlinear Frequency Response Method. in Processes. 2020;8(11).
doi:10.3390/pr8111357 .

Živković, Luka, Milić, Viktor, Vidaković-Koch, Tanja, Petkovska, Menka, "Rapid Multi-Objective Optimization of Periodically Operated Processes Based on the Computer-Aided Nonlinear Frequency Response Method" in Processes, 8, no. 11 (2020),
https://doi.org/10.3390/pr8111357 . .

TY  - JOUR
AU  - Živković, Luka
AU  - Vidaković-Koch, Tanja
AU  - Petkovska, Menka
PY  - 2020
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4437
AB  - The Nonlinear Frequency Response (NFR) method is a useful Process Systems Engineering tool for developing experimental techniques and periodic processes that exploit the system nonlinearity. The basic and most time-consuming step of the NFR method is the derivation of frequency response functions (FRFs). The computer-aided Nonlinear Frequency Response (cNFR) method, presented in this work, uses a software application for automatic derivation of the FRFs, thus making the NFR analysis much simpler, even for systems with complex dynamics. The cNFR application uses an Excel user-friendly interface for defining the model equations and variables, and MATLAB code which performs analytical derivations. As a result, the cNFR application generates MATLAB files containing the derived FRFs in a symbolic and algebraic vector form. In this paper, the software is explained in detail and illustrated through: (1) analysis of periodic operation of an isothermal continuous stirred-tank reactor with a simple reaction mechanism, and (2) experimental identification of electrochemical oxygen reduction reaction.
PB  - MDPI, Basel
T2  - Processes
T1  - Computer-Aided Nonlinear Frequency Response Method for Investigating the Dynamics of Chemical Engineering Systems
IS  - 11
VL  - 8
DO  - 10.3390/pr8111354
ER  - 

@article{
author = "Živković, Luka and Vidaković-Koch, Tanja and Petkovska, Menka",
year = "2020",
abstract = "The Nonlinear Frequency Response (NFR) method is a useful Process Systems Engineering tool for developing experimental techniques and periodic processes that exploit the system nonlinearity. The basic and most time-consuming step of the NFR method is the derivation of frequency response functions (FRFs). The computer-aided Nonlinear Frequency Response (cNFR) method, presented in this work, uses a software application for automatic derivation of the FRFs, thus making the NFR analysis much simpler, even for systems with complex dynamics. The cNFR application uses an Excel user-friendly interface for defining the model equations and variables, and MATLAB code which performs analytical derivations. As a result, the cNFR application generates MATLAB files containing the derived FRFs in a symbolic and algebraic vector form. In this paper, the software is explained in detail and illustrated through: (1) analysis of periodic operation of an isothermal continuous stirred-tank reactor with a simple reaction mechanism, and (2) experimental identification of electrochemical oxygen reduction reaction.",
publisher = "MDPI, Basel",
journal = "Processes",
title = "Computer-Aided Nonlinear Frequency Response Method for Investigating the Dynamics of Chemical Engineering Systems",
number = "11",
volume = "8",
doi = "10.3390/pr8111354"
}

Živković, L., Vidaković-Koch, T.,& Petkovska, M.. (2020). Computer-Aided Nonlinear Frequency Response Method for Investigating the Dynamics of Chemical Engineering Systems. in Processes
MDPI, Basel., 8(11).
https://doi.org/10.3390/pr8111354

Živković L, Vidaković-Koch T, Petkovska M. Computer-Aided Nonlinear Frequency Response Method for Investigating the Dynamics of Chemical Engineering Systems. in Processes. 2020;8(11).
doi:10.3390/pr8111354 .

Živković, Luka, Vidaković-Koch, Tanja, Petkovska, Menka, "Computer-Aided Nonlinear Frequency Response Method for Investigating the Dynamics of Chemical Engineering Systems" in Processes, 8, no. 11 (2020),
https://doi.org/10.3390/pr8111354 . .

TY  - JOUR
AU  - Živković, Luka
AU  - Kandaswamy, Saikrishnan
AU  - Petkovska, Menka
AU  - Vidaković-Koch, Tanja
PY  - 2020
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4446
AB  - The intensification of an electrochemical process by forced periodic operation was studied for the first time using the computer-aided Nonlinear Frequency Response method. This method enabled the automatic generation of frequency response functions and the DC components (Faradaic rectification) of the cost (overpotential) and benefit (current density) indicators. The case study, oxygen reduction reaction, was investigated both experimentally and theoretically. The results of the cost-benefit indicator analysis show that forced periodic change of electrode potential can be superior when compared to the steady-state regime for specific operational parameters. When the electrode rotation rate is changed periodically, the process will always deteriorate as the dynamic operation will inevitably lead to the thickening of the diffusion layer. This phenomenon is explained both from a mathematical and a physical point of view.
PB  - Frontiers Media Sa, Lausanne
T2  - Frontiers in Chemistry
T1  - Evaluation of Electrochemical Process Improvement Using the Computer-Aided Nonlinear Frequency Response Method: Oxygen Reduction Reaction in Alkaline Media
VL  - 8
DO  - 10.3389/fchem.2020.579869
ER  - 

@article{
author = "Živković, Luka and Kandaswamy, Saikrishnan and Petkovska, Menka and Vidaković-Koch, Tanja",
year = "2020",
abstract = "The intensification of an electrochemical process by forced periodic operation was studied for the first time using the computer-aided Nonlinear Frequency Response method. This method enabled the automatic generation of frequency response functions and the DC components (Faradaic rectification) of the cost (overpotential) and benefit (current density) indicators. The case study, oxygen reduction reaction, was investigated both experimentally and theoretically. The results of the cost-benefit indicator analysis show that forced periodic change of electrode potential can be superior when compared to the steady-state regime for specific operational parameters. When the electrode rotation rate is changed periodically, the process will always deteriorate as the dynamic operation will inevitably lead to the thickening of the diffusion layer. This phenomenon is explained both from a mathematical and a physical point of view.",
publisher = "Frontiers Media Sa, Lausanne",
journal = "Frontiers in Chemistry",
title = "Evaluation of Electrochemical Process Improvement Using the Computer-Aided Nonlinear Frequency Response Method: Oxygen Reduction Reaction in Alkaline Media",
volume = "8",
doi = "10.3389/fchem.2020.579869"
}

Živković, L., Kandaswamy, S., Petkovska, M.,& Vidaković-Koch, T.. (2020). Evaluation of Electrochemical Process Improvement Using the Computer-Aided Nonlinear Frequency Response Method: Oxygen Reduction Reaction in Alkaline Media. in Frontiers in Chemistry
Frontiers Media Sa, Lausanne., 8.
https://doi.org/10.3389/fchem.2020.579869

Živković L, Kandaswamy S, Petkovska M, Vidaković-Koch T. Evaluation of Electrochemical Process Improvement Using the Computer-Aided Nonlinear Frequency Response Method: Oxygen Reduction Reaction in Alkaline Media. in Frontiers in Chemistry. 2020;8.
doi:10.3389/fchem.2020.579869 .

Živković, Luka, Kandaswamy, Saikrishnan, Petkovska, Menka, Vidaković-Koch, Tanja, "Evaluation of Electrochemical Process Improvement Using the Computer-Aided Nonlinear Frequency Response Method: Oxygen Reduction Reaction in Alkaline Media" in Frontiers in Chemistry, 8 (2020),
https://doi.org/10.3389/fchem.2020.579869 . .

TY  - JOUR
AU  - Nikolić-Paunić, Daliborka
AU  - Seidel-Morgenstern, Andreas
AU  - Petkovska, Menka
PY  - 2020
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4360
AB  - Nonlinear frequency response (NFR) method was used to evaluate the forced periodic operations and their potential for improving the system performance compared to steady-state operations. The NFR method was used to evaluate the time-average performances of forced periodically operated systems subjected to simultaneous periodic modulation of two-inputs of general waveforms. As an example, a forced periodically operated adiabatic CSTR with simple nth order reaction A - gt  v(p)P and square-wave modulation of two pairs of inputs were analyzed in detail. The theory is illustrated analyzing the hydrolysis of acetic acid anhydride performed in a laboratory scale adiabatic CSTR. The results showed that significant improvements could be achieved by simultaneous modulation of both pairs of inputs. Comparison with the results of numerical integration showed that the approximation using only the asymmetrical second order FRFs and the first three harmonics of the inputs provide very reliable predictions of the DC component.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Chemical Engineering Science
T1  - Nonlinear frequency response analysis of forced periodic operations with simultaneous modulation of two general waveform inputs with applications on adiabatic CSTR with square-wave modulations
VL  - 226
DO  - 10.1016/j.ces.2020.115842
ER  - 

@article{
author = "Nikolić-Paunić, Daliborka and Seidel-Morgenstern, Andreas and Petkovska, Menka",
year = "2020",
abstract = "Nonlinear frequency response (NFR) method was used to evaluate the forced periodic operations and their potential for improving the system performance compared to steady-state operations. The NFR method was used to evaluate the time-average performances of forced periodically operated systems subjected to simultaneous periodic modulation of two-inputs of general waveforms. As an example, a forced periodically operated adiabatic CSTR with simple nth order reaction A - gt  v(p)P and square-wave modulation of two pairs of inputs were analyzed in detail. The theory is illustrated analyzing the hydrolysis of acetic acid anhydride performed in a laboratory scale adiabatic CSTR. The results showed that significant improvements could be achieved by simultaneous modulation of both pairs of inputs. Comparison with the results of numerical integration showed that the approximation using only the asymmetrical second order FRFs and the first three harmonics of the inputs provide very reliable predictions of the DC component.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Chemical Engineering Science",
title = "Nonlinear frequency response analysis of forced periodic operations with simultaneous modulation of two general waveform inputs with applications on adiabatic CSTR with square-wave modulations",
volume = "226",
doi = "10.1016/j.ces.2020.115842"
}

Nikolić-Paunić, D., Seidel-Morgenstern, A.,& Petkovska, M.. (2020). Nonlinear frequency response analysis of forced periodic operations with simultaneous modulation of two general waveform inputs with applications on adiabatic CSTR with square-wave modulations. in Chemical Engineering Science
Pergamon-Elsevier Science Ltd, Oxford., 226.
https://doi.org/10.1016/j.ces.2020.115842

Nikolić-Paunić D, Seidel-Morgenstern A, Petkovska M. Nonlinear frequency response analysis of forced periodic operations with simultaneous modulation of two general waveform inputs with applications on adiabatic CSTR with square-wave modulations. in Chemical Engineering Science. 2020;226.
doi:10.1016/j.ces.2020.115842 .

Nikolić-Paunić, Daliborka, Seidel-Morgenstern, Andreas, Petkovska, Menka, "Nonlinear frequency response analysis of forced periodic operations with simultaneous modulation of two general waveform inputs with applications on adiabatic CSTR with square-wave modulations" in Chemical Engineering Science, 226 (2020),
https://doi.org/10.1016/j.ces.2020.115842 . .

TY  - CONF
AU  - Seidel, Carsten
AU  - Felischak, Matthias
AU  - Nikolić, Daliborka
AU  - Seidel-Morgenstern, Andreas
AU  - Petkovska, Menka
AU  - Kienle, Achim
PY  - 2020
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4412
AB  - Methanol is an essential primary chemical in the chemical industry. Further, there is a growing interest in using methanol also for chemical energy storage. Excess electrical wind or solar energy can be converted to hydrogen and react with CO and CO2 from biogas or waste streams to methanol. Suitable kinetic models are required for designing such processes. Established kinetics need to be extended to account for strongly varying input ratios of H2, CO, and CO2 in such applications leading to the need for dynamic process operation. Kinetic models for methanol synthesis accounting for dynamic changes of the catalyst morphology were proposed recently [1]. For the implementation and evaluation of the dynamic operation, a novel reactor concept, incorporating a micro-berty reactor, is established. The configuration allows the modulation of single and multiple input parameters simultaneously, such as partial pressure, total flow-rate, and total pressure. Periodic variation of the inputs results in fluctuating outputs. For the analysis of these changes, an online mass spectrometer (MS) and a micro-gas chromatograph (GC) are implemented for time-resolved concentration profiles, as well as the analysis of collected samples of multiple fluctuation periods. A set of dynamic experiments is determined by optimal experimental design that improves the parameter sensitivity by solving optimal control problems to identify an optimal parameter set. Additionally, it is analyzed what kind of additional measurement is required for further improvement of the identifiability of the kinetic model [2]. The nonlinear dynamic behavior of the methanol synthesis can be exploited by a forced periodic modulation of different feed streams and total flow-rate (separately of simultaneously) that result in improvements of the time-average output, in comparison to the steady-state process, concerning different objective functions. The nonlinear frequency response (NFR) analysis [3] is used to estimate suitable input variations and the corresponding optimal dynamic parameters (forcing frequency, amplitudes, and phase difference). The NFR method was already applied in various cases [4–6], and it represents promising starting points for rigorous dynamic optimization. The selection of the objective functions for single- and multi-objective optimization of forced periodic operations is critically discussed.
PB  - Max Planck Institute
C3  - 4th Indo-German Workshop on Advances in Materials, Reaction& Separation Processes, Berlin, Germany
T1  - Optimization of methanol synthesis under forced dynamic operation
UR  - https://hdl.handle.net/21.15107/rcub_technorep_4412
ER  - 

@conference{
author = "Seidel, Carsten and Felischak, Matthias and Nikolić, Daliborka and Seidel-Morgenstern, Andreas and Petkovska, Menka and Kienle, Achim",
year = "2020",
abstract = "Methanol is an essential primary chemical in the chemical industry. Further, there is a growing interest in using methanol also for chemical energy storage. Excess electrical wind or solar energy can be converted to hydrogen and react with CO and CO2 from biogas or waste streams to methanol. Suitable kinetic models are required for designing such processes. Established kinetics need to be extended to account for strongly varying input ratios of H2, CO, and CO2 in such applications leading to the need for dynamic process operation. Kinetic models for methanol synthesis accounting for dynamic changes of the catalyst morphology were proposed recently [1]. For the implementation and evaluation of the dynamic operation, a novel reactor concept, incorporating a micro-berty reactor, is established. The configuration allows the modulation of single and multiple input parameters simultaneously, such as partial pressure, total flow-rate, and total pressure. Periodic variation of the inputs results in fluctuating outputs. For the analysis of these changes, an online mass spectrometer (MS) and a micro-gas chromatograph (GC) are implemented for time-resolved concentration profiles, as well as the analysis of collected samples of multiple fluctuation periods. A set of dynamic experiments is determined by optimal experimental design that improves the parameter sensitivity by solving optimal control problems to identify an optimal parameter set. Additionally, it is analyzed what kind of additional measurement is required for further improvement of the identifiability of the kinetic model [2]. The nonlinear dynamic behavior of the methanol synthesis can be exploited by a forced periodic modulation of different feed streams and total flow-rate (separately of simultaneously) that result in improvements of the time-average output, in comparison to the steady-state process, concerning different objective functions. The nonlinear frequency response (NFR) analysis [3] is used to estimate suitable input variations and the corresponding optimal dynamic parameters (forcing frequency, amplitudes, and phase difference). The NFR method was already applied in various cases [4–6], and it represents promising starting points for rigorous dynamic optimization. The selection of the objective functions for single- and multi-objective optimization of forced periodic operations is critically discussed.",
publisher = "Max Planck Institute",
journal = "4th Indo-German Workshop on Advances in Materials, Reaction& Separation Processes, Berlin, Germany",
title = "Optimization of methanol synthesis under forced dynamic operation",
url = "https://hdl.handle.net/21.15107/rcub_technorep_4412"
}

Seidel, C., Felischak, M., Nikolić, D., Seidel-Morgenstern, A., Petkovska, M.,& Kienle, A.. (2020). Optimization of methanol synthesis under forced dynamic operation. in 4th Indo-German Workshop on Advances in Materials, Reaction& Separation Processes, Berlin, Germany
Max Planck Institute..
https://hdl.handle.net/21.15107/rcub_technorep_4412

Seidel C, Felischak M, Nikolić D, Seidel-Morgenstern A, Petkovska M, Kienle A. Optimization of methanol synthesis under forced dynamic operation. in 4th Indo-German Workshop on Advances in Materials, Reaction& Separation Processes, Berlin, Germany. 2020;.
https://hdl.handle.net/21.15107/rcub_technorep_4412 .

Seidel, Carsten, Felischak, Matthias, Nikolić, Daliborka, Seidel-Morgenstern, Andreas, Petkovska, Menka, Kienle, Achim, "Optimization of methanol synthesis under forced dynamic operation" in 4th Indo-German Workshop on Advances in Materials, Reaction& Separation Processes, Berlin, Germany (2020),
https://hdl.handle.net/21.15107/rcub_technorep_4412 .

TY  - CONF
AU  - Petkovska, Menka
AU  - Kienle, Achim
AU  - Nikolić, Daliborka
AU  - Seidel, Carsten
AU  - Felischak, Matthias
AU  - Seidel-Morgenstern, Andreas
PY  - 2020
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4411
AB  - We used the nonlinear frequency response (NFR) method in order to identify forced periodic conditions under which the acetic acid anhydride hydrolysis (chosen as a test reaction) can be favorably performed in a CSTR. Based on the results of the theoretical analysis, experimental investigations were performed using a lab-scale reactor exposed to two fluctuating inlet streams (water and acetic anhydride) with adjustable flow-rates, which enables modulation of the inlet reactant concentrations or/and total flow-rates in a flexible manner. The concentration of acetic acid formed is measured in the reactor online and used to monitor the process dynamics. Averaged values of the product outlet stream serve to validate the mean values predicted by NFR analysis and to evaluate the potential of this flexible forcing strategy. Recently we started to analyze both theoretically and experimentally the potential of applying a forced periodic operation to improve the methanol synthesis from CO, CO2 and H2 using the conventional Cu/ZnO/Al2O3 catalysts. This work is based on a recently published detailed model of this reaction, which is capable to quantify the rates under dynamic conditions (C. Seidel, A. Jörke, B. Vollbrecht, A. Seidel-Morgenstern, A. Kienle, Chem. Eng. Sci. 175 (2917) 130–138).
PB  - Max Planck Institute
C3  - 4th Indo-German Workshop on Advances in Materials, Reaction& Separation Processes, Berlin, Germany
T1  - Forced periodic reactor operation
UR  - https://hdl.handle.net/21.15107/rcub_technorep_4411
ER  - 

@conference{
author = "Petkovska, Menka and Kienle, Achim and Nikolić, Daliborka and Seidel, Carsten and Felischak, Matthias and Seidel-Morgenstern, Andreas",
year = "2020",
abstract = "We used the nonlinear frequency response (NFR) method in order to identify forced periodic conditions under which the acetic acid anhydride hydrolysis (chosen as a test reaction) can be favorably performed in a CSTR. Based on the results of the theoretical analysis, experimental investigations were performed using a lab-scale reactor exposed to two fluctuating inlet streams (water and acetic anhydride) with adjustable flow-rates, which enables modulation of the inlet reactant concentrations or/and total flow-rates in a flexible manner. The concentration of acetic acid formed is measured in the reactor online and used to monitor the process dynamics. Averaged values of the product outlet stream serve to validate the mean values predicted by NFR analysis and to evaluate the potential of this flexible forcing strategy. Recently we started to analyze both theoretically and experimentally the potential of applying a forced periodic operation to improve the methanol synthesis from CO, CO2 and H2 using the conventional Cu/ZnO/Al2O3 catalysts. This work is based on a recently published detailed model of this reaction, which is capable to quantify the rates under dynamic conditions (C. Seidel, A. Jörke, B. Vollbrecht, A. Seidel-Morgenstern, A. Kienle, Chem. Eng. Sci. 175 (2917) 130–138).",
publisher = "Max Planck Institute",
journal = "4th Indo-German Workshop on Advances in Materials, Reaction& Separation Processes, Berlin, Germany",
title = "Forced periodic reactor operation",
url = "https://hdl.handle.net/21.15107/rcub_technorep_4411"
}

Petkovska, M., Kienle, A., Nikolić, D., Seidel, C., Felischak, M.,& Seidel-Morgenstern, A.. (2020). Forced periodic reactor operation. in 4th Indo-German Workshop on Advances in Materials, Reaction& Separation Processes, Berlin, Germany
Max Planck Institute..
https://hdl.handle.net/21.15107/rcub_technorep_4411

Petkovska M, Kienle A, Nikolić D, Seidel C, Felischak M, Seidel-Morgenstern A. Forced periodic reactor operation. in 4th Indo-German Workshop on Advances in Materials, Reaction& Separation Processes, Berlin, Germany. 2020;.
https://hdl.handle.net/21.15107/rcub_technorep_4411 .

Petkovska, Menka, Kienle, Achim, Nikolić, Daliborka, Seidel, Carsten, Felischak, Matthias, Seidel-Morgenstern, Andreas, "Forced periodic reactor operation" in 4th Indo-German Workshop on Advances in Materials, Reaction& Separation Processes, Berlin, Germany (2020),
https://hdl.handle.net/21.15107/rcub_technorep_4411 .

TY  - JOUR
AU  - Brzić, Danica
AU  - Petkovska, Menka
PY  - 2019
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4211
AB  - In the present paper, the Nonlinear Frequency Response (NFR) analysis is applied for theoretical study of kinetics of adsorption governed by pore-surface diffusion. The concept of higher-order frequency response functions (FRFs) is used. Based on a nonlinear mathematical model for adsorption of pure gas and spherical adsorbent particles, the theoretical first-and second-order FRFs, which relate the adsorbate concentration in the particle to the surrounding pressure (F-1 (omega) and F-2 (omega,omega)), have been derived. The obtained FRFs have been simulated for different steady-state pressures and different ratios (between zero and one) of surface to pore diffusion coefficients. The results show that, unlike F-1 (omega), F-2 (omega,omega) exhibits features which unambiguously distinguish the pore-surface diffusion model from pure pore diffusion and micropore diffusion. Based on the characteristic features of F-1 (omega) and F-2 (omega,omega), a new methodology for direct estimation of the separate values of the pore and surface diffusion coefficients has been established.
PB  - Hindawi Ltd, London
T2  - Mathematical Problems in Engineering
T1  - Nonlinear Frequency Response Analysis as a Tool for Identification of Adsorption Kinetics: Case Study-Pore-Surface Diffusion Control
VL  - 2019
DO  - 10.1155/2019/7932967
ER  - 

@article{
author = "Brzić, Danica and Petkovska, Menka",
year = "2019",
abstract = "In the present paper, the Nonlinear Frequency Response (NFR) analysis is applied for theoretical study of kinetics of adsorption governed by pore-surface diffusion. The concept of higher-order frequency response functions (FRFs) is used. Based on a nonlinear mathematical model for adsorption of pure gas and spherical adsorbent particles, the theoretical first-and second-order FRFs, which relate the adsorbate concentration in the particle to the surrounding pressure (F-1 (omega) and F-2 (omega,omega)), have been derived. The obtained FRFs have been simulated for different steady-state pressures and different ratios (between zero and one) of surface to pore diffusion coefficients. The results show that, unlike F-1 (omega), F-2 (omega,omega) exhibits features which unambiguously distinguish the pore-surface diffusion model from pure pore diffusion and micropore diffusion. Based on the characteristic features of F-1 (omega) and F-2 (omega,omega), a new methodology for direct estimation of the separate values of the pore and surface diffusion coefficients has been established.",
publisher = "Hindawi Ltd, London",
journal = "Mathematical Problems in Engineering",
title = "Nonlinear Frequency Response Analysis as a Tool for Identification of Adsorption Kinetics: Case Study-Pore-Surface Diffusion Control",
volume = "2019",
doi = "10.1155/2019/7932967"
}

Brzić, D.,& Petkovska, M.. (2019). Nonlinear Frequency Response Analysis as a Tool for Identification of Adsorption Kinetics: Case Study-Pore-Surface Diffusion Control. in Mathematical Problems in Engineering
Hindawi Ltd, London., 2019.
https://doi.org/10.1155/2019/7932967

Brzić D, Petkovska M. Nonlinear Frequency Response Analysis as a Tool for Identification of Adsorption Kinetics: Case Study-Pore-Surface Diffusion Control. in Mathematical Problems in Engineering. 2019;2019.
doi:10.1155/2019/7932967 .

Brzić, Danica, Petkovska, Menka, "Nonlinear Frequency Response Analysis as a Tool for Identification of Adsorption Kinetics: Case Study-Pore-Surface Diffusion Control" in Mathematical Problems in Engineering, 2019 (2019),
https://doi.org/10.1155/2019/7932967 . .

TY  - JOUR
AU  - Kandaswamy, Saikrishnan
AU  - Sorrentino, Antonio
AU  - Borate, Shivangi
AU  - Živković, Luka
AU  - Petkovska, Menka
AU  - Vidaković-Koch, Tanja
PY  - 2019
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4078
AB  - Oxygen reduction reaction (ORR) was studied on a silver polycrystalline electrode in different NaOH concentrations with a help of rotating disc and rotating ring disc electrodes. Soluble reaction intermediate was detected at all alkaline concentrations, but its concentration increased with an increase of the level of impurities. ORR is not NaOH concentration dependent at low concentrations (0.1 and 1 M). In 11 M NaOH ORR onsets at more positive potentials in the region where underpotential silver oxide formation shows less reversible behaviour. The nonlinear frequency response analysis spectra show significant qualitative difference with NaOH concentration indicating a high capability of this method for kinetic mechanism investigations.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Electrochimica Acta
T1  - Oxygen reduction reaction on silver electrodes under strong alkaline conditions
VL  - 320
DO  - 10.1016/j.electacta.2019.07.028
ER  - 

@article{
author = "Kandaswamy, Saikrishnan and Sorrentino, Antonio and Borate, Shivangi and Živković, Luka and Petkovska, Menka and Vidaković-Koch, Tanja",
year = "2019",
abstract = "Oxygen reduction reaction (ORR) was studied on a silver polycrystalline electrode in different NaOH concentrations with a help of rotating disc and rotating ring disc electrodes. Soluble reaction intermediate was detected at all alkaline concentrations, but its concentration increased with an increase of the level of impurities. ORR is not NaOH concentration dependent at low concentrations (0.1 and 1 M). In 11 M NaOH ORR onsets at more positive potentials in the region where underpotential silver oxide formation shows less reversible behaviour. The nonlinear frequency response analysis spectra show significant qualitative difference with NaOH concentration indicating a high capability of this method for kinetic mechanism investigations.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Electrochimica Acta",
title = "Oxygen reduction reaction on silver electrodes under strong alkaline conditions",
volume = "320",
doi = "10.1016/j.electacta.2019.07.028"
}

Kandaswamy, S., Sorrentino, A., Borate, S., Živković, L., Petkovska, M.,& Vidaković-Koch, T.. (2019). Oxygen reduction reaction on silver electrodes under strong alkaline conditions. in Electrochimica Acta
Pergamon-Elsevier Science Ltd, Oxford., 320.
https://doi.org/10.1016/j.electacta.2019.07.028

Kandaswamy S, Sorrentino A, Borate S, Živković L, Petkovska M, Vidaković-Koch T. Oxygen reduction reaction on silver electrodes under strong alkaline conditions. in Electrochimica Acta. 2019;320.
doi:10.1016/j.electacta.2019.07.028 .

Kandaswamy, Saikrishnan, Sorrentino, Antonio, Borate, Shivangi, Živković, Luka, Petkovska, Menka, Vidaković-Koch, Tanja, "Oxygen reduction reaction on silver electrodes under strong alkaline conditions" in Electrochimica Acta, 320 (2019),
https://doi.org/10.1016/j.electacta.2019.07.028 . .

TY  - CONF
AU  - Felischak, Matthias
AU  - Nikolić, Daliborka
AU  - Petkovska, Menka
AU  - Hamel, Christof
AU  - Seidel-Morgenstern, Andreas
PY  - 2019
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4152
AB  - The classical design of continuous chemical reactors exploits steady-state operation, which is optimized and maintained by appropriate control systems. Nevertheless, it is well-known that the reactor performance can be enhanced by applying periodic regimes, like forced modulations of input parameters.The identification and evaluation of suitable periodic operation conditions is challenging. One approach that can be used is based on nonlinear frequency response (NFR) analysis. The focus of this work is the experimental analysis of shapes for two simultaneously imposed modulations (sinusoidal and square) in comparison to results predicted by the NFR method. The acetic anhydride hydrolysis was studied in an adiabatic CSTR exploiting a periodic operation mode, which was found to be superior to the corresponding steady-state operation.
C3  - German reaction Engineering Meeting (DECHEMA), Wuerzburg, Germany
T1  - Forced Periodic Operation: Effect of shapes for two simultaneously imposed modulations
UR  - https://hdl.handle.net/21.15107/rcub_technorep_4152
ER  - 

@conference{
author = "Felischak, Matthias and Nikolić, Daliborka and Petkovska, Menka and Hamel, Christof and Seidel-Morgenstern, Andreas",
year = "2019",
abstract = "The classical design of continuous chemical reactors exploits steady-state operation, which is optimized and maintained by appropriate control systems. Nevertheless, it is well-known that the reactor performance can be enhanced by applying periodic regimes, like forced modulations of input parameters.The identification and evaluation of suitable periodic operation conditions is challenging. One approach that can be used is based on nonlinear frequency response (NFR) analysis. The focus of this work is the experimental analysis of shapes for two simultaneously imposed modulations (sinusoidal and square) in comparison to results predicted by the NFR method. The acetic anhydride hydrolysis was studied in an adiabatic CSTR exploiting a periodic operation mode, which was found to be superior to the corresponding steady-state operation.",
journal = "German reaction Engineering Meeting (DECHEMA), Wuerzburg, Germany",
title = "Forced Periodic Operation: Effect of shapes for two simultaneously imposed modulations",
url = "https://hdl.handle.net/21.15107/rcub_technorep_4152"
}

Felischak, M., Nikolić, D., Petkovska, M., Hamel, C.,& Seidel-Morgenstern, A.. (2019). Forced Periodic Operation: Effect of shapes for two simultaneously imposed modulations. in German reaction Engineering Meeting (DECHEMA), Wuerzburg, Germany.
https://hdl.handle.net/21.15107/rcub_technorep_4152

Felischak M, Nikolić D, Petkovska M, Hamel C, Seidel-Morgenstern A. Forced Periodic Operation: Effect of shapes for two simultaneously imposed modulations. in German reaction Engineering Meeting (DECHEMA), Wuerzburg, Germany. 2019;.
https://hdl.handle.net/21.15107/rcub_technorep_4152 .

Felischak, Matthias, Nikolić, Daliborka, Petkovska, Menka, Hamel, Christof, Seidel-Morgenstern, Andreas, "Forced Periodic Operation: Effect of shapes for two simultaneously imposed modulations" in German reaction Engineering Meeting (DECHEMA), Wuerzburg, Germany (2019),
https://hdl.handle.net/21.15107/rcub_technorep_4152 .

TY  - CONF
AU  - Nikolić, Daliborka
AU  - Seidel, Carsten
AU  - Kienle, Achim
AU  - Seidel-Morgenstern, Andreas
AU  - Petkovska, Menka
PY  - 2019
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4159
AB  - In this work, the NFR method is implemented for evaluation of possible improvement for the reaction of methanol synthesis by hydrogenation of CO and CO2, using a standard Cu/ZnO/Al2O3 catalyst. For start, a forced periodically operated isothermal continuous-stirred tank reactor (CSTR) is considered. A simplified (lumped) kinetic model of methanol synthesis with 14 parameters which were estimated from the results of an extensive experimental investigation is used. The NFR method is performed for evaluation of possible increase of methanol production by modulating the mole fractions of CO and CO2 in the feed stream, as well as their simultaneous modulation. The necessary asymmetrical second order frequency response functions correlating the methanol production with the modulated inputs are derived and the forcing parameters leading to improvement of the reactor performance are determined. The results of the NFR analysis will further be used for rigorous optimisation of the forced periodic operations and planning the best experimental scenarios. The final step will be experimental investigation and confirmation on a laboratory scale reactor.
C3  - 2nd International Process Intensification Conference, Leuven, Belgium
T1  - Intensification of a chemical reactor for methanol synthesis through forced periodic operations- Evaluation based on Nonlinear Frequency Response Analysis
UR  - https://hdl.handle.net/21.15107/rcub_technorep_4159
ER  - 

@conference{
author = "Nikolić, Daliborka and Seidel, Carsten and Kienle, Achim and Seidel-Morgenstern, Andreas and Petkovska, Menka",
year = "2019",
abstract = "In this work, the NFR method is implemented for evaluation of possible improvement for the reaction of methanol synthesis by hydrogenation of CO and CO2, using a standard Cu/ZnO/Al2O3 catalyst. For start, a forced periodically operated isothermal continuous-stirred tank reactor (CSTR) is considered. A simplified (lumped) kinetic model of methanol synthesis with 14 parameters which were estimated from the results of an extensive experimental investigation is used. The NFR method is performed for evaluation of possible increase of methanol production by modulating the mole fractions of CO and CO2 in the feed stream, as well as their simultaneous modulation. The necessary asymmetrical second order frequency response functions correlating the methanol production with the modulated inputs are derived and the forcing parameters leading to improvement of the reactor performance are determined. The results of the NFR analysis will further be used for rigorous optimisation of the forced periodic operations and planning the best experimental scenarios. The final step will be experimental investigation and confirmation on a laboratory scale reactor.",
journal = "2nd International Process Intensification Conference, Leuven, Belgium",
title = "Intensification of a chemical reactor for methanol synthesis through forced periodic operations- Evaluation based on Nonlinear Frequency Response Analysis",
url = "https://hdl.handle.net/21.15107/rcub_technorep_4159"
}

Nikolić, D., Seidel, C., Kienle, A., Seidel-Morgenstern, A.,& Petkovska, M.. (2019). Intensification of a chemical reactor for methanol synthesis through forced periodic operations- Evaluation based on Nonlinear Frequency Response Analysis. in 2nd International Process Intensification Conference, Leuven, Belgium.
https://hdl.handle.net/21.15107/rcub_technorep_4159

Nikolić D, Seidel C, Kienle A, Seidel-Morgenstern A, Petkovska M. Intensification of a chemical reactor for methanol synthesis through forced periodic operations- Evaluation based on Nonlinear Frequency Response Analysis. in 2nd International Process Intensification Conference, Leuven, Belgium. 2019;.
https://hdl.handle.net/21.15107/rcub_technorep_4159 .

Nikolić, Daliborka, Seidel, Carsten, Kienle, Achim, Seidel-Morgenstern, Andreas, Petkovska, Menka, "Intensification of a chemical reactor for methanol synthesis through forced periodic operations- Evaluation based on Nonlinear Frequency Response Analysis" in 2nd International Process Intensification Conference, Leuven, Belgium (2019),
https://hdl.handle.net/21.15107/rcub_technorep_4159 .

TY  - JOUR
AU  - Mandić, Miloš
AU  - Dikić, Vladimir
AU  - Petkovska, Menka
AU  - Todić, Branislav
AU  - Bukur, Dragomir B.
AU  - Nikačević, Nikola
PY  - 2018
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3846
AB  - Dynamic performance of a milli-scale fixed bed reactor for Fischer-Tropsch synthesis (FTS) was studied using a dynamic pseudo-homogeneous 1D reactor model. The model uses detailed kinetics to describe the rates of FTS product formation. Dynamic responses of the process variables and main performance indicators, including productivity of C-5(+) hydrocarbons and CH4 selectivity, to input step changes, were analyzed. Total of 7 inlet variables were used in step-change-response analysis, with different magnitudes of change and for two initial steady-state conditions. Reactor simulations show highly nonlinear behavior due to phenomena coupling and fast dynamics due to system small scale and intensified rates within. In addition, reactor model shows instability related to thermal runaway with certain magnitudes of step change of coolant temperature and feed flow rate. The analysis outlines the effects of potential process disturbances on operation of milli-scale fixed bed reactor for FTS and provides general guidelines for control systems.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Chemical Engineering Science
T1  - Dynamic analysis of millimetre-scale fixed bed reactors for Fischer-Tropsch synthesis
EP  - 447
SP  - 434
VL  - 192
DO  - 10.1016/j.ces.2018.07.052
ER  - 

@article{
author = "Mandić, Miloš and Dikić, Vladimir and Petkovska, Menka and Todić, Branislav and Bukur, Dragomir B. and Nikačević, Nikola",
year = "2018",
abstract = "Dynamic performance of a milli-scale fixed bed reactor for Fischer-Tropsch synthesis (FTS) was studied using a dynamic pseudo-homogeneous 1D reactor model. The model uses detailed kinetics to describe the rates of FTS product formation. Dynamic responses of the process variables and main performance indicators, including productivity of C-5(+) hydrocarbons and CH4 selectivity, to input step changes, were analyzed. Total of 7 inlet variables were used in step-change-response analysis, with different magnitudes of change and for two initial steady-state conditions. Reactor simulations show highly nonlinear behavior due to phenomena coupling and fast dynamics due to system small scale and intensified rates within. In addition, reactor model shows instability related to thermal runaway with certain magnitudes of step change of coolant temperature and feed flow rate. The analysis outlines the effects of potential process disturbances on operation of milli-scale fixed bed reactor for FTS and provides general guidelines for control systems.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Chemical Engineering Science",
title = "Dynamic analysis of millimetre-scale fixed bed reactors for Fischer-Tropsch synthesis",
pages = "447-434",
volume = "192",
doi = "10.1016/j.ces.2018.07.052"
}

Mandić, M., Dikić, V., Petkovska, M., Todić, B., Bukur, D. B.,& Nikačević, N.. (2018). Dynamic analysis of millimetre-scale fixed bed reactors for Fischer-Tropsch synthesis. in Chemical Engineering Science
Pergamon-Elsevier Science Ltd, Oxford., 192, 434-447.
https://doi.org/10.1016/j.ces.2018.07.052

Mandić M, Dikić V, Petkovska M, Todić B, Bukur DB, Nikačević N. Dynamic analysis of millimetre-scale fixed bed reactors for Fischer-Tropsch synthesis. in Chemical Engineering Science. 2018;192:434-447.
doi:10.1016/j.ces.2018.07.052 .

Mandić, Miloš, Dikić, Vladimir, Petkovska, Menka, Todić, Branislav, Bukur, Dragomir B., Nikačević, Nikola, "Dynamic analysis of millimetre-scale fixed bed reactors for Fischer-Tropsch synthesis" in Chemical Engineering Science, 192 (2018):434-447,
https://doi.org/10.1016/j.ces.2018.07.052 . .

TY  - JOUR
AU  - Currie, Robert
AU  - Nikolić, Daliborka
AU  - Petkovska, Menka
AU  - Simakov, David
PY  - 2018
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3788
AB  - Nonlinear frequency response (NFR) analysis was applied on a Sabatier reactor. A substantial improvement in CO2 conversion was predicted under certain conditions. The NFR analysis prediction was validated using a kinetic flow reactor model. A comprehensive packed bed model was analyzed using NFR as a guidance.
T2  - The 25th International Symposium of Chemical Reaction Engineering (ISCRE 25), Florance, Italy
T1  - CO2 conversion enhancement in a periodically operated Sabatier reactor: Nonlinear frequency response analysis and simulation- based Study
SP  - P52
DO  - 10.1002/ijch.201700134
ER  - 

@article{
author = "Currie, Robert and Nikolić, Daliborka and Petkovska, Menka and Simakov, David",
year = "2018",
abstract = "Nonlinear frequency response (NFR) analysis was applied on a Sabatier reactor. A substantial improvement in CO2 conversion was predicted under certain conditions. The NFR analysis prediction was validated using a kinetic flow reactor model. A comprehensive packed bed model was analyzed using NFR as a guidance.",
journal = "The 25th International Symposium of Chemical Reaction Engineering (ISCRE 25), Florance, Italy",
title = "CO2 conversion enhancement in a periodically operated Sabatier reactor: Nonlinear frequency response analysis and simulation- based Study",
pages = "P52",
doi = "10.1002/ijch.201700134"
}

Currie, R., Nikolić, D., Petkovska, M.,& Simakov, D.. (2018). CO2 conversion enhancement in a periodically operated Sabatier reactor: Nonlinear frequency response analysis and simulation- based Study. in The 25th International Symposium of Chemical Reaction Engineering (ISCRE 25), Florance, Italy, P52.
https://doi.org/10.1002/ijch.201700134

Currie R, Nikolić D, Petkovska M, Simakov D. CO2 conversion enhancement in a periodically operated Sabatier reactor: Nonlinear frequency response analysis and simulation- based Study. in The 25th International Symposium of Chemical Reaction Engineering (ISCRE 25), Florance, Italy. 2018;:P52.
doi:10.1002/ijch.201700134 .

Currie, Robert, Nikolić, Daliborka, Petkovska, Menka, Simakov, David, "CO2 conversion enhancement in a periodically operated Sabatier reactor: Nonlinear frequency response analysis and simulation- based Study" in The 25th International Symposium of Chemical Reaction Engineering (ISCRE 25), Florance, Italy (2018):P52,
https://doi.org/10.1002/ijch.201700134 . .

TY  - CONF
AU  - Felischak, Matthias
AU  - Nikolić, Daliborka
AU  - Petkovska, Menka
AU  - Seidel-Morgenstern, Andreas
PY  - 2018
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3763
AB  - Theoretical evaluation of possible reactor improvement for periodic operation. Automated experimental setup was built, with a lab-scale CSTR and adjustable flow-rates, in which periodic operations can be conducted. The concept was implemented for the hydrolysis of acetic anhydride as a model reaction.
C3  - The 25th International Symposium of Chemical Reaction Engineering (ISCRE 25), Florance, Italy
T1  - Forced periodic reactor operation with simultaneous modulation of two inputs: Experimental investigation based on Nonlinear Frequency Response Analysis
UR  - https://hdl.handle.net/21.15107/rcub_technorep_3763
ER  - 

@conference{
author = "Felischak, Matthias and Nikolić, Daliborka and Petkovska, Menka and Seidel-Morgenstern, Andreas",
year = "2018",
abstract = "Theoretical evaluation of possible reactor improvement for periodic operation. Automated experimental setup was built, with a lab-scale CSTR and adjustable flow-rates, in which periodic operations can be conducted. The concept was implemented for the hydrolysis of acetic anhydride as a model reaction.",
journal = "The 25th International Symposium of Chemical Reaction Engineering (ISCRE 25), Florance, Italy",
title = "Forced periodic reactor operation with simultaneous modulation of two inputs: Experimental investigation based on Nonlinear Frequency Response Analysis",
url = "https://hdl.handle.net/21.15107/rcub_technorep_3763"
}

Felischak, M., Nikolić, D., Petkovska, M.,& Seidel-Morgenstern, A.. (2018). Forced periodic reactor operation with simultaneous modulation of two inputs: Experimental investigation based on Nonlinear Frequency Response Analysis. in The 25th International Symposium of Chemical Reaction Engineering (ISCRE 25), Florance, Italy.
https://hdl.handle.net/21.15107/rcub_technorep_3763

Felischak M, Nikolić D, Petkovska M, Seidel-Morgenstern A. Forced periodic reactor operation with simultaneous modulation of two inputs: Experimental investigation based on Nonlinear Frequency Response Analysis. in The 25th International Symposium of Chemical Reaction Engineering (ISCRE 25), Florance, Italy. 2018;.
https://hdl.handle.net/21.15107/rcub_technorep_3763 .

Felischak, Matthias, Nikolić, Daliborka, Petkovska, Menka, Seidel-Morgenstern, Andreas, "Forced periodic reactor operation with simultaneous modulation of two inputs: Experimental investigation based on Nonlinear Frequency Response Analysis" in The 25th International Symposium of Chemical Reaction Engineering (ISCRE 25), Florance, Italy (2018),
https://hdl.handle.net/21.15107/rcub_technorep_3763 .

TY  - JOUR
AU  - Petkovska, Menka
AU  - Nikolić-Paunić, Daliborka
AU  - Seidel-Morgenstern, Andreas
PY  - 2018
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3878
AB  - Nonlinear Frequency Response (NFR) method is a relatively new method which can be used for fast evaluation of possible process improvements through periodic operations. The method is analytical and approximate. Its main task is to give an answer whether periodic modulation of one or more process inputs can result in improved process performance. The method is explained in brief and an overview of the existing applications is given. The review covers simple reactions performed in isothermal and non-isothermal stirred tank reactors exposed to different modulated inputs (inlet concentration, flow-rate, inlet temperature, temperature of the heating/cooling medium). Processes with two simultaneously modulated inputs and different shapes of the periodic input are also considered. The results of the NFR method are compared with the results of numerical simulation and a critical evaluation of the method is given.
PB  - Wiley-VCH Verlag Gmbh, Weinheim
T2  - Israel Journal of Chemistry
T1  - Nonlinear Frequency Response Method for Evaluating Forced Periodic Operations of Chemical Reactors
EP  - 681
IS  - 6-7
SP  - 663
VL  - 58
DO  - 10.1002/ijch.201700132
ER  - 

@article{
author = "Petkovska, Menka and Nikolić-Paunić, Daliborka and Seidel-Morgenstern, Andreas",
year = "2018",
abstract = "Nonlinear Frequency Response (NFR) method is a relatively new method which can be used for fast evaluation of possible process improvements through periodic operations. The method is analytical and approximate. Its main task is to give an answer whether periodic modulation of one or more process inputs can result in improved process performance. The method is explained in brief and an overview of the existing applications is given. The review covers simple reactions performed in isothermal and non-isothermal stirred tank reactors exposed to different modulated inputs (inlet concentration, flow-rate, inlet temperature, temperature of the heating/cooling medium). Processes with two simultaneously modulated inputs and different shapes of the periodic input are also considered. The results of the NFR method are compared with the results of numerical simulation and a critical evaluation of the method is given.",
publisher = "Wiley-VCH Verlag Gmbh, Weinheim",
journal = "Israel Journal of Chemistry",
title = "Nonlinear Frequency Response Method for Evaluating Forced Periodic Operations of Chemical Reactors",
pages = "681-663",
number = "6-7",
volume = "58",
doi = "10.1002/ijch.201700132"
}

Petkovska, M., Nikolić-Paunić, D.,& Seidel-Morgenstern, A.. (2018). Nonlinear Frequency Response Method for Evaluating Forced Periodic Operations of Chemical Reactors. in Israel Journal of Chemistry
Wiley-VCH Verlag Gmbh, Weinheim., 58(6-7), 663-681.
https://doi.org/10.1002/ijch.201700132

Petkovska M, Nikolić-Paunić D, Seidel-Morgenstern A. Nonlinear Frequency Response Method for Evaluating Forced Periodic Operations of Chemical Reactors. in Israel Journal of Chemistry. 2018;58(6-7):663-681.
doi:10.1002/ijch.201700132 .

Petkovska, Menka, Nikolić-Paunić, Daliborka, Seidel-Morgenstern, Andreas, "Nonlinear Frequency Response Method for Evaluating Forced Periodic Operations of Chemical Reactors" in Israel Journal of Chemistry, 58, no. 6-7 (2018):663-681,
https://doi.org/10.1002/ijch.201700132 . .

TY  - CONF
AU  - Felischak, Matthias
AU  - Nikolić, Daliborka
AU  - Petkovska, Menka
AU  - Seidel-Morgenstern, Andreas
PY  - 2018
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3787
AB  - The classical design of continuously operated chemical reactors assumes that they are operated in a steady-state which is usually optimized and maintained by using appropriate control systems. Nevertheless, it has been known for quite some time that, in some cases, better performance can be achieved by applying a periodic regime exploiting forced modulations of one or more inputs to the reactor [1,2]. Finding out whether, at which conditions and to which extent periodic operation can be superior to the optimal steady-state is difficult. One approach that can be used is an approximate, analytical method called nonlinear frequency response (NFR) method [3].  The NFR method is based on the concept of higher order frequency response functions (FRFs) and applicable for weakly nonlinear systems [3]. Frequency response of a weakly nonlinear system, in addition to the basic harmonic, contains a non-periodic (DC) term and, theoretically, an infinite sequence of higher harmonics. The DC component of the output is responsible for the average performance of the periodically operated reactor, and its sign and value define whether, and to which extent, the periodic operation leads to process improvement. Using the NFR method, this DC component can be approximately estimated from a single asymmetrical second order FRF (for modulation of a single input) or from several single input and cross- asymmetrical second order FRFs (for multiple-input modulation). For the case of multiple modulated inputs, the optimal phase difference between the modulated inputs, which is an essential parameter, can be directly determined [4,5]. Promising parameters to be periodically modulated separately or simultaneously are clearly the reactant inlet concentrations, the flow-rates and the feed temperatures.   We used the NFR method in order to identify forced periodic conditions under which the acetic acid anhydride hydrolysis (chosen as a test reaction) can be favorably performed in a CSTR. Based on the results of the theoretical analysis, experimental investigations were performed using a lab-scale reactor exposed to two fluctuating inlet streams (water and acetic anhydride) with adjustable flow-rates, which enables modulation of the inlet reactant concentrations or/and total flow-rates in a flexible manner. The concentration of the acetic acid formed is measured in the reactor online and used to monitor the process dynamics. Averaged values of the product outlet stream serve to validate the mean values predicted by NFR analysis and to evaluate the potential of this flexible forcing strategy.
C3  - American Institute of Chemical Engineers Annual Meeting (AIChE Annual Meeting), Pittsburgh, USA
T1  - Forced periodic reactor operation with simultaneous modulation of two inputs: Nonlinear frequency response analysis  and experimental demonstration
UR  - https://hdl.handle.net/21.15107/rcub_technorep_3787
ER  - 

@conference{
author = "Felischak, Matthias and Nikolić, Daliborka and Petkovska, Menka and Seidel-Morgenstern, Andreas",
year = "2018",
abstract = "The classical design of continuously operated chemical reactors assumes that they are operated in a steady-state which is usually optimized and maintained by using appropriate control systems. Nevertheless, it has been known for quite some time that, in some cases, better performance can be achieved by applying a periodic regime exploiting forced modulations of one or more inputs to the reactor [1,2]. Finding out whether, at which conditions and to which extent periodic operation can be superior to the optimal steady-state is difficult. One approach that can be used is an approximate, analytical method called nonlinear frequency response (NFR) method [3].  The NFR method is based on the concept of higher order frequency response functions (FRFs) and applicable for weakly nonlinear systems [3]. Frequency response of a weakly nonlinear system, in addition to the basic harmonic, contains a non-periodic (DC) term and, theoretically, an infinite sequence of higher harmonics. The DC component of the output is responsible for the average performance of the periodically operated reactor, and its sign and value define whether, and to which extent, the periodic operation leads to process improvement. Using the NFR method, this DC component can be approximately estimated from a single asymmetrical second order FRF (for modulation of a single input) or from several single input and cross- asymmetrical second order FRFs (for multiple-input modulation). For the case of multiple modulated inputs, the optimal phase difference between the modulated inputs, which is an essential parameter, can be directly determined [4,5]. Promising parameters to be periodically modulated separately or simultaneously are clearly the reactant inlet concentrations, the flow-rates and the feed temperatures.   We used the NFR method in order to identify forced periodic conditions under which the acetic acid anhydride hydrolysis (chosen as a test reaction) can be favorably performed in a CSTR. Based on the results of the theoretical analysis, experimental investigations were performed using a lab-scale reactor exposed to two fluctuating inlet streams (water and acetic anhydride) with adjustable flow-rates, which enables modulation of the inlet reactant concentrations or/and total flow-rates in a flexible manner. The concentration of the acetic acid formed is measured in the reactor online and used to monitor the process dynamics. Averaged values of the product outlet stream serve to validate the mean values predicted by NFR analysis and to evaluate the potential of this flexible forcing strategy.",
journal = "American Institute of Chemical Engineers Annual Meeting (AIChE Annual Meeting), Pittsburgh, USA",
title = "Forced periodic reactor operation with simultaneous modulation of two inputs: Nonlinear frequency response analysis  and experimental demonstration",
url = "https://hdl.handle.net/21.15107/rcub_technorep_3787"
}

Felischak, M., Nikolić, D., Petkovska, M.,& Seidel-Morgenstern, A.. (2018). Forced periodic reactor operation with simultaneous modulation of two inputs: Nonlinear frequency response analysis  and experimental demonstration. in American Institute of Chemical Engineers Annual Meeting (AIChE Annual Meeting), Pittsburgh, USA.
https://hdl.handle.net/21.15107/rcub_technorep_3787

Felischak M, Nikolić D, Petkovska M, Seidel-Morgenstern A. Forced periodic reactor operation with simultaneous modulation of two inputs: Nonlinear frequency response analysis  and experimental demonstration. in American Institute of Chemical Engineers Annual Meeting (AIChE Annual Meeting), Pittsburgh, USA. 2018;.
https://hdl.handle.net/21.15107/rcub_technorep_3787 .

Felischak, Matthias, Nikolić, Daliborka, Petkovska, Menka, Seidel-Morgenstern, Andreas, "Forced periodic reactor operation with simultaneous modulation of two inputs: Nonlinear frequency response analysis  and experimental demonstration" in American Institute of Chemical Engineers Annual Meeting (AIChE Annual Meeting), Pittsburgh, USA (2018),
https://hdl.handle.net/21.15107/rcub_technorep_3787 .