1. MINLP synthesis of reactor networks in overall process schemes based on a concept of time-dependent economic regionsNataša Iršič Bedenik, Marcel Ropotar, Zdravko Kravanja, 2007, original scientific article Abstract: The design and optimization of reactor networks using the conventional conceptof attainable region is based on technological (conversion, selectivity, etc.), rather than, economical criteria (cost, profit, etc.). The solution from the economical point of view when the operating and investment costs cannot be neglected may not be optimal, not even in regard to the structure. In order to circumvent this deficiency, the conventional Concentration Attainable Region (CAR) is transformed into an Economic Region (ER) using economic optimization criteria. A novel concept for ER constructionis proposed for multi-D problems. One-parametric NLP or MINLP optimizations with reactor volume as a varying parameter are performed to construct trajectories in the ER. In this way the ER is aided by mathematical programming for 3D or more D problems in order to handle dimensions higher than 2 as degrees of freedom for the economic objective function. ER is attainable (EAR) only when the economic objective function is linear. The more the objective function is discontinuous, discrete, nonlinear and non-convex and the more its cost coefficients vary with time, the less the principles of AR can be applied to ER. However, economically optimal reactor systems always lie at the borders of ERs. Two important insights have been gained during the construction of different time-dependent ERs, which have been used in upgrading the MINLP approach to the synthesis of reactor networks in overall process schemes: (i) A reactor network superstructure has been reestablished based on economical optimization criteria and the principles of ER. (ii) Over a longer period, the performing of a stochastic multi-period MINLP synthesis is recommended, in order to consider the time variability and uncertainties of economic parameters. A special multi-period strategy is proposed to upgrade the efficiency of the MINLP synthesis.
Keywords: concentration attainable region, economic attainable region, discrete nonlinear region, MINLP
Published in DKUM: 01.06.2012; Views: 2289; Downloads: 158
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2. Priporočila 7. razvojne skupine za procesno tehnologijo za povečanje konkurenčnosti Slovenije : strateški dokument 7. razvojne skupine za Procesno tehnologijoZdravko Kravanja, Blaž Nardin, Boris Kuselj, Brane Širok, Damjan Krt, Igor Milavec, Iztok Žun, Jože Duhovnik, Slavko Dolinšek, Stanko Strmčnik, Bojan Bučar, Peter Glavič, Andreja Goršek, Franc Jelovčan, Vladimir Jovan, Željko Knez, Marijan Medič, Zoran Novak, Zorka Novak-Pintarič, Franc Pohleven, Marjana Simonič, Alojzij Sluga, Rihard Karba, Đani Juričić, Igor Škrjanc, Marko Munih, 2008, treatise, preliminary study, study Keywords: konkurenčnost, ciljni raziskovalni programi, procesna tehnologija, tehnološke platforme, napredne obdelovalno-izdelovalne tehnologije, trajnostni razvoj, Slovenija
Published in DKUM: 31.05.2012; Views: 2387; Downloads: 58
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3. Development of a mathematical model for the dynamic optimization of batch reactors, and MINLP synthesis of plug-flow reactors in complex networksMarcel Ropotar, Zdravko Kravanja, 2007, original scientific article Abstract: This paper describes the development of a robust and efficient reactor model suitable for representing batch and plugflow reactors (PFRs) in different applications. These would range from the nonlinear (NLP) dynamic optimization of a stand-alone batch reactor up to the mixed-integer nonlinear (MINLP) synthesis of a complex reactor network in overall process schemes. Different schemes for the Orthogonal Collocation on Finite Element (OCFE) and various model formulations, in the case of MINLP model, were studied in order to increase the robustness and efficiency of the model. A deterministic model for known kinetics was obtained for batch and PFR reactors and extended for uncertainties in process parameters and reaction kinetics when the kinetics is unknown. Different variations of the developed model were applied to certain problems, as examples. The first motivating example was the dynamic optimization of batch reactor and the second the MINLP synthesis of a process scheme for the production of allyl chloride. The NLP version of the model with moving finite elements was found to be the most efficient for representing a batch reactor in the dynamic optimization example, and PFR trains in the process synthesis example.
Keywords: batch reactor, orthogonal collocation, off-line optimization, on-line optimization, flexibility, uncertainty
Published in DKUM: 31.05.2012; Views: 2341; Downloads: 74
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4. NAČRTOVANJE IN SINTEZA KEMIJSKIH PROCESOV Z UPORABO UČINKOVITIH MODELNIH TEHNIK IN REŠITVENIH STRATEGIJMarcel Ropotar, 2009, dissertation Abstract: V doktorski disertaciji obravnavamo modelne tehnike in strategije za reševanje sinteznih problemov, kjer nastanejo zapleteni modeli, ki so težko rešljivi. Modeli so kombinatorično zahtevni, nelinearni in/ali nekonveksni, zato se kljub že razvitim metodam in algoritmom pogosto pojavijo potrebe po novih, učinkovitejših strategijah in metodah. V prvem delu predstavljamo alternativno formulacijo konveksne lupine, ki temelji na mešano celoštevilski transformaciji spremenljivk. Transformacija spremenljivk transformira spremenljivke z ničelno spodnjo mejo v spremenljivke z ne-ničelno spodnjo mejo. Tako izvajamo optimiranje v ožjem preslikanem dopustnem prostoru lokalnih spremenljivk, to je spremenljivk, ki pripadajo alternativnim procesnim enotam. To nam pri reševanju mešano celoštevilskih linearnih in nelinearnih optimizacijskih primerov (MILP in MINLP) omogoča uporabo ne-ničelnih spodnjih mej. Z uporabo ne-ničelnih spodnjih mej se izognemo deljenju z nič in drugim matematičnim singularnostim. Pogosto pa so ne-ničelne spodnje meje uporabne, kadar imamo opravka s spremenljivkami, kot sta temperatura in pretok, ki morata imeti ne-ničelne vrednosti tudi kadar procesna enota ni izbrana. S transformacijo spremenljivk smo i) pretvorili konvencionalno formulacijo konveksne lupine v alternativno formulacijo in ii) konvencionalni algoritem zunanje poenostavitve spremenili v alternativni algoritem OA. Alternativno formulacijo konveksne lupine smo primerjali s formulacijo veliki-M in konvencionalno formulacijo na treh sinteznih primerih in izvedli več različnih eksperimentov. Rezultati kažejo, da je alternativna formulacija v večini primerov najbolj učinkovita glede računalniškega časa, števila iteracij in vozlišč. Ugotovili smo, da izbor vrednosti spremenljivk, ko alternativa ni izbrana, zelo vpliva na učinkovitost alternativne formulacije; in da je najprimernejša in najenostavnejša izbira kar spodnja ne-ničelna meja. Alternativno formulacijo in alternativni algoritem smo vnesli v procesni sintetizer MIPSYN in pri tem zmodelirali nove logične povezovalne člene in sprogramirali nov preprocesor za zunanje poenostavitve.
Pogosto je dolg čas reševanja procesnih sinteznih problemov posledica zapletenih modelov reaktorjev. Zato smo za reaktorje, ki so opisani z diferencialnimi enačbami (šaržni, cevni) in jih rešujemo z metodo ortogonalne kolokacije končnih elementov, predlagali učinkovito numerično proceduro za reševanje. V sklopu procedure smo razvili model za dinamično optimiranje šaržnega reaktorja in preizkušali različne strategije in sheme, s katerimi smo povečevali robustnost modela. Nazadnje smo razvili še model za načrtovanje fleksibilnega šaržnega reaktorja, s katerim je mogoče tolerirati odstopanja procesnih parametrov. Pri reševanju motivacijskega primera šaržnega reaktorja se je kot najučinkovitejši izkazal model NLP s pomičnimi končnimi elementi. Ta model smo nato uporabili tudi za modeliranje niza elementov v cevnem reaktorju in izvedli sintezo MINLP študijske procesne sheme za proizvodnjo alilklorida ter z eno-parametričnim optimiranjem iz najboljših rešitev določili še ekonomsko območje.
S predlagano alternativno formulacijo, novimi strategijami in robustnimi modeli za optimiranje reaktorjev je mogoče lažje reševati zapletene sintezne probleme, procesni sintetizer MIPSYN pa je tako postal še učinkovitejše programsko orodje za sintezo procesov in reševanje drugih tehniških problemov.
Keywords: procesna sinteza, procesni sintetizer, konveksna lupina, transformacija spremenljivk, splošno disjunktno programiranje, zunanje poenostavite, NLP, MINLP, šaržni reaktor, cevni reaktor, ortogonalna kolokacija, diferencialno-algebrski sistem enačb
Published in DKUM: 02.12.2009; Views: 3771; Downloads: 341
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