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Forced periodically operated chemical reactors-evaluation and analysis by the nonlinear frequency response method

Periodične operacije hemijskih reaktora-evaluacija i analiza primenom metode nelinearnog frekventnog odziva.

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Author
Nikolić Paunić, Daliborka S.
Mentor
Petkovska, Menka
Committee members
Žižović, Irena
Nikačević, Nikola
Panić, Vladimir
Seidel-Morgenstern, Andreas
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Abstract
The conventional way to design and operate the processes in chemical engineering is to determine the optimal steady-state design and to operate as close as possible to that steady-state. Nevertheless, many investigations have proven that periodic operations, when one or more inputs are periodically modulated, can result with better process performances, especially for chemical reactors. The origin of improvement of the reactor performance lies in fact that for nonlinear systems, the periodic modulation of one or more inputs will cause the outputs to change periodically, as well, with the mean value which is, in general, different from their steady-state values. In this work, we propose and implement the nonlinear frequency response (NFR) method for fast and easy evaluation of possible reactor improvements throughout periodic modulations. The NFR method is a relatively new method, mathematically based on Volterra series, generalized Fourier transform and the concept of higher-order freq...uency response functions (FRFs). The change of the reactor performances caused by periodic operations can be evaluated from the DC (non-periodic) component of the frequency response of the reactor, if it is a weakly nonlinear system. The DC component can be calculated exactly as a sum of an indefinite series, with members which are proportional to the asymmetrical even order FRFs. Nevertheless, based on the NFR method, the DC component can be estimated only from the first, dominant term of this series, which is proportional to the asymmetrical second order frequency response function G2(ω,-ω). In that way, for analysis of possible improvements of forced periodically operated chemical reactors, it is enough to derive and analyze asymmetrical second order FRFs G2(ω,-ω). For this reason, the NFR method is essentially approximate...

Uobičajen način projektovanja procesa u hemijskom inženjerstvu podrazumeva određivanje optimalnog stacionog stanja i upravljanje procesom na način koji odezbeđuje da se uslovi održavaju što je moguće bliže tom optimalnom stacionarnom stanju. Ipak, mnoga istaživanja su pokazala da se performanse procesa, pogotovo hemijskih reaktora, mogu poboljšati ukoliko se jedan ili više ulaza periodično menja. Poboljšanje performansi hemijskih reaktora pri periodičnom režimu rada je posledica nelinearnosti sistema. Kod nelinearnih sistema, kada se periodično menja jedan ili više ulaza, izlazi iz sistema se takođe periodično menjaju, a njihova srednja vrednost se, u opštem slučaju, razlikuje od stacionarnih vrednosti. Methoda nelinearnog frekventnog odziva (NFO) je u ovom radu predložena i primenjena za brzo i lako određivanje mogućeg poboljšanja performansi reaktora primenom periodičnog režima rada. Metoda NFO je relativno nova metoda i ona je matematički bazirana na Voltera redovima, generalizovano...j Furijeovoj transformaciji i na konceptu frekventnih prenosnih funkcija (FPF) višeg reda. Uticaj periodičnih operacija na performanse reaktora se može odrediti preko DC komponente (neperiodičnog člana) frekventnog odziva nelinearnog sistema. DC komponenta se može tačno prikazati beskonačnim redom čiji su članovi proporcionalni asimetričnim FPF parnih redova. Medjutim, u predloženoj metodi NFO DC komponenta se procenjuje samo na osnovu svog dominantnog člana koji je proporcionalan asimetričnoj FPF drugog reda G2(ω,-ω), tako da je za analizu mogućeg poboljšanja performansi reaktora pri periodičnom režimu rada dovoljno izvesti i analizirati samo ovu funkciju. Zbog toga je metoda NFO po svojoj suštini približna. U ovom radu, metoda NFO je primenjena za procenu mogućeg poboljšanja (povećenja konverzije reaktanta ili prinosa proizvoda) pri periodičnoj promeni jednog ili dva...

Faculty:
University of Belgrade, Faculty of Technology and Metallurgy
Date:
09-06-2016
Keywords:
Nonlinear frequency response method / Metoda nelinearnog frekventnog odziva / Higher order frequency response functions / Volterra series / Periodically operated chemical reactors / Single input modulation / Two-input modulation / Forcing parameters / Isothermal CSTR / Non-isothermal CSTR / Adiabatic CSTR / Frekventne prenosne funkcije višeg reda / Volterra redovi / Periodične operacije hemijskih reaktora / Periodična promena jednog ulaza / Periodična promena dva ulaza / Parametri periodične promene / Izotermni PRIM / Neizotermni PRIM / Adijabatski PRIM
[ Google Scholar ]
Handle
https://hdl.handle.net/21.15107/rcub_nardus_6360
URI
http://eteze.bg.ac.rs/application/showtheses?thesesId=3686
https://nardus.mpn.gov.rs/handle/123456789/6360
https://fedorabg.bg.ac.rs/fedora/get/o:12496/bdef:Content/download
http://vbs.rs/scripts/cobiss?command=DISPLAY&base=70036&RID=48096783

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