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Case study on tubular reactor hot-spot temperature control for throughput maximization / Sadanand Singh in Industrial & engineering chemistry research, Vol. 47 N°19 (Octobre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N°19 (Octobre 2008) . - p. 7257–7263 Titre : Case study on tubular reactor hot-spot temperature control for throughput maximization Type de document : texte imprimé Auteurs : Sadanand Singh, Auteur ; Shivangi Lal, Auteur ; Nitin Kaistha, Auteur Année de publication : 2008 Article en page(s) : p. 7257–7263 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Tubular  reactor  Hot-spot  temperature  control  Gas-phase  alkylation Résumé : Auctioneering hot-spot temperature control of a highly exothermic cooled tubular reactor (constant coolant temperature) for cumene production via the irreversible gas-phase alkylation of benzene with propylene (A + B → C) is studied. Specifically, three control configurations are quantitatively evaluated for tightness of hot-spot temperature control and maximum achievable process throughput with reactor cooling duty as the bottleneck constraint. The configurations manipulate respectively the reactor cooling duty (CS1), the reactor inlet temperature (CS2), and the fresh propylene feed (CS3) for regulating the hot-spot temperature. Plantwide dynamic simulation results show that tightest hot-spot temperature control is achieved by the direct manipulation of the reactor cooling duty (CS1). Use of reactor inlet temperature as the manipulation handle (CS2) is not recommended due to large deviations in the reactor temperature profile for a throughput increase. Manipulating the fresh propylene feed rate (limiting reactant) as in CS3 provides loose but acceptable hot-spot temperature control. CS3 is most preferred for throughput maximization as the reactor is operated at the bottleneck constraint of maximum heat removal capacity. For the sample case study, the maximum achievable throughput increases by more than 7% by use of CS3 (over CS1). En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071287c [article] Case study on tubular reactor hot-spot temperature control for throughput maximization [texte imprimé] / Sadanand Singh, Auteur ; Shivangi Lal, Auteur ; Nitin Kaistha, Auteur . - 2008 . - p. 7257–7263. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N°19 (Octobre 2008) . - p. 7257–7263 Mots-clés : Tubular  reactor  Hot-spot  temperature  control  Gas-phase  alkylation Résumé : Auctioneering hot-spot temperature control of a highly exothermic cooled tubular reactor (constant coolant temperature) for cumene production via the irreversible gas-phase alkylation of benzene with propylene (A + B → C) is studied. Specifically, three control configurations are quantitatively evaluated for tightness of hot-spot temperature control and maximum achievable process throughput with reactor cooling duty as the bottleneck constraint. The configurations manipulate respectively the reactor cooling duty (CS1), the reactor inlet temperature (CS2), and the fresh propylene feed (CS3) for regulating the hot-spot temperature. Plantwide dynamic simulation results show that tightest hot-spot temperature control is achieved by the direct manipulation of the reactor cooling duty (CS1). Use of reactor inlet temperature as the manipulation handle (CS2) is not recommended due to large deviations in the reactor temperature profile for a throughput increase. Manipulating the fresh propylene feed rate (limiting reactant) as in CS3 provides loose but acceptable hot-spot temperature control. CS3 is most preferred for throughput maximization as the reactor is operated at the bottleneck constraint of maximum heat removal capacity. For the sample case study, the maximum achievable throughput increases by more than 7% by use of CS3 (over CS1). En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071287c

Economic plantwide control of a C4 isomerization process / Rahul Jagtap in Industrial & engineering chemistry research, Vol. 51 N° 36 (Septembre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 36 (Septembre 2012) . - pp. 11731–11743 Titre : Economic plantwide control of a C4 isomerization process Type de document : texte imprimé Auteurs : Rahul Jagtap, Auteur ; Nitin Kaistha, Auteur Année de publication : 2012 Article en page(s) : pp. 11731–11743 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Isomerization  process Résumé : Plantwide control system design for economically optimal operation over a large throughput range of a C4 isomerization process is considered. The steady-state process degrees of freedom (dofs; eight in total) are optimized for a given throughput (mode I) and maximum throughput (mode II). At maximum throughput, all of the steady-state dofs are exhausted in driving as many constraints (inequality/equality) active. For this process, it is possible to synthesize a simple decentralized plantwide control system (CS1) for tight control of all of the active constraints at maximum throughput with negligible back-off due to transients with satisfactory inventory regulation and process stabilization. A unique feature of CS1 is the location of the throughput manipulator (TPM) inside the plant (in contrast to that at the process feed) and its relocation due to input saturation in a split range arrangement. A comparison with the conventional structure (CS2) with TPM at the process feed and conventional overrides for handling constraints demonstrates the economic and dynamic superiority of CS1. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie3001293 [article] Economic plantwide control of a C4 isomerization process [texte imprimé] / Rahul Jagtap, Auteur ; Nitin Kaistha, Auteur . - 2012 . - pp. 11731–11743. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 36 (Septembre 2012) . - pp. 11731–11743 Mots-clés : Isomerization  process Résumé : Plantwide control system design for economically optimal operation over a large throughput range of a C4 isomerization process is considered. The steady-state process degrees of freedom (dofs; eight in total) are optimized for a given throughput (mode I) and maximum throughput (mode II). At maximum throughput, all of the steady-state dofs are exhausted in driving as many constraints (inequality/equality) active. For this process, it is possible to synthesize a simple decentralized plantwide control system (CS1) for tight control of all of the active constraints at maximum throughput with negligible back-off due to transients with satisfactory inventory regulation and process stabilization. A unique feature of CS1 is the location of the throughput manipulator (TPM) inside the plant (in contrast to that at the process feed) and its relocation due to input saturation in a split range arrangement. A comparison with the conventional structure (CS2) with TPM at the process feed and conventional overrides for handling constraints demonstrates the economic and dynamic superiority of CS1. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie3001293

Internal heat integration and controllability of double feed reactive distillation columns, 2. effect of catalyst redistribution / M. V. Pavan Kumar in Industrial & engineering chemistry research, Vol. 47 N°19 (Octobre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N°19 (Octobre 2008) . - p. 7304–7311 Titre : Internal heat integration and controllability of double feed reactive distillation columns, 2. effect of catalyst redistribution Type de document : texte imprimé Auteurs : M. V. Pavan Kumar, Auteur ; Nitin Kaistha, Auteur Année de publication : 2008 Article en page(s) : p. 7304–7311 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Catalyst  redistribution  Reactive  distillation  column Résumé : The effect of internal heat integration by catalyst redistribution on the controllability of an ideal and a methyl acetate reactive distillation (RD) column is studied. Conventional designs with feeds immediately above and below the reactive section are internally heat integrated by (a) extending the reactive section into the stripping section with catalyst redistribution, followed by (b) altering the feed tray locations. For the ideal RD system, only reactive section extension results in a design with a reboiler energy savings of 7.7%. The design obtained by reactive section extension followed by altered feed tray locations gives greater energy savings of 18.2%. For the methyl acetate system, simple reactive section extension with no change in the feed tray locations gives the most energy-efficient design with an energy savings of 39.7%. A comparison of the closed-loop performance of the two-point temperature control structures for the different designs demonstrates that temperature inferential control can be used to regulate the internally heat-integrated designs of both the ideal and methyl acetate systems. The controllability of the ideal RD column with full internal heat integration (both items (a) and (b) above) is found to be inferior to the conventional design. For the methyl acetate system, the controllability of the internally heat-integrated design is improved, relative to the conventional design. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071639f [article] Internal heat integration and controllability of double feed reactive distillation columns, 2. effect of catalyst redistribution [texte imprimé] / M. V. Pavan Kumar, Auteur ; Nitin Kaistha, Auteur . - 2008 . - p. 7304–7311. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N°19 (Octobre 2008) . - p. 7304–7311 Mots-clés : Catalyst  redistribution  Reactive  distillation  column Résumé : The effect of internal heat integration by catalyst redistribution on the controllability of an ideal and a methyl acetate reactive distillation (RD) column is studied. Conventional designs with feeds immediately above and below the reactive section are internally heat integrated by (a) extending the reactive section into the stripping section with catalyst redistribution, followed by (b) altering the feed tray locations. For the ideal RD system, only reactive section extension results in a design with a reboiler energy savings of 7.7%. The design obtained by reactive section extension followed by altered feed tray locations gives greater energy savings of 18.2%. For the methyl acetate system, simple reactive section extension with no change in the feed tray locations gives the most energy-efficient design with an energy savings of 39.7%. A comparison of the closed-loop performance of the two-point temperature control structures for the different designs demonstrates that temperature inferential control can be used to regulate the internally heat-integrated designs of both the ideal and methyl acetate systems. The controllability of the ideal RD column with full internal heat integration (both items (a) and (b) above) is found to be inferior to the conventional design. For the methyl acetate system, the controllability of the internally heat-integrated design is improved, relative to the conventional design. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071639f

Plantwide control for economic optimum operation of a recycle process with side reaction / Rahul Jagtap in Industrial & engineering chemistry research, Vol. 50 N° 14 (Juillet 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 14 (Juillet 2011) . - pp. 8571-8584 Titre : Plantwide control for economic optimum operation of a recycle process with side reaction Type de document : texte imprimé Auteurs : Rahul Jagtap, Auteur ; Nitin Kaistha, Auteur Année de publication : 2011 Article en page(s) : pp. 8571-8584 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Process  control Résumé : Plantwide control system design for the economically optimum operation of a recycle process with side reaction, consisting of a continuous stirred tank reactor (CSTR) followed by two distillation columns, is studied. The steady-state operating profit is maximized over a large throughput range for an existing design. As the throughput is increased, constraints progressively become active until maximum throughput is reached where all the steady-state degrees of freedom are exhausted. A strategy of moving the throughput manipulator to the next constraint to become active as the throughput is increased is used to improve the control of the active constraint. This minimizes the variability and hence the back-off in the active constraint variables for economically optimal operation. The plantwide control system (CS1) so obtained is quantitatively compared with three other more conventional control systems (CS2–CS4) in terms of the required back-off to avoid hard constraint violation for disturbances. Results show that the most economical operation is achieved using CS1 and the traditional practice of fixing throughput at the feed (CS4) gives the highest (up to 7%) economic loss. A simple switching scheme to transition from low to maximum throughput is also demonstrated. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24346898 [article] Plantwide control for economic optimum operation of a recycle process with side reaction [texte imprimé] / Rahul Jagtap, Auteur ; Nitin Kaistha, Auteur . - 2011 . - pp. 8571-8584. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 14 (Juillet 2011) . - pp. 8571-8584 Mots-clés : Process  control Résumé : Plantwide control system design for the economically optimum operation of a recycle process with side reaction, consisting of a continuous stirred tank reactor (CSTR) followed by two distillation columns, is studied. The steady-state operating profit is maximized over a large throughput range for an existing design. As the throughput is increased, constraints progressively become active until maximum throughput is reached where all the steady-state degrees of freedom are exhausted. A strategy of moving the throughput manipulator to the next constraint to become active as the throughput is increased is used to improve the control of the active constraint. This minimizes the variability and hence the back-off in the active constraint variables for economically optimal operation. The plantwide control system (CS1) so obtained is quantitatively compared with three other more conventional control systems (CS2–CS4) in terms of the required back-off to avoid hard constraint violation for disturbances. Results show that the most economical operation is achieved using CS1 and the traditional practice of fixing throughput at the feed (CS4) gives the highest (up to 7%) economic loss. A simple switching scheme to transition from low to maximum throughput is also demonstrated. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24346898

Plantwide control for throughput maximization / Rahul Kanodia in Industrial & engineering chemistry research, Vol. 49 N° 1 (Janvier 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 1 (Janvier 2010) . - pp. 210–221 Titre : Plantwide control for throughput maximization : a case study Type de document : texte imprimé Auteurs : Rahul Kanodia, Auteur ; Nitin Kaistha, Auteur Année de publication : 2010 Article en page(s) : pp. 210–221 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Plantwide  Control--Throughput--Maximization--Case  Study Résumé : The impact of the basic plantwide regulatory control structure on maximizing the throughput using an explicit optimizing controller is quantitatively evaluated for a simple process module. The module consists of the reaction A + B → C occurring in a continuously stirred tank reactor followed by a distillation column separating the product from the recycled unreacted reactants. The column vapor boilup hitting a maximum acts as the bottleneck constraint limiting the throughput due to column flooding. Through an evaluation of reasonable plantwide control structures, the location of the throughput manipulator, the composition analyzer for overall component inventory balancing and the “local” column reflux management policy are shown to significantly affect the maximum throughput. Quantitative results show that locating the throughput manipulator close to and where possible at the bottleneck constraint reduces the throughput derating necessary due to disturbances. Designing the plantwide regulatory control system to minimize the process variability propagated into the bottleneck constraint emerges as the key heuristic from the case study. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900366r [article] Plantwide control for throughput maximization : a case study [texte imprimé] / Rahul Kanodia, Auteur ; Nitin Kaistha, Auteur . - 2010 . - pp. 210–221. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 1 (Janvier 2010) . - pp. 210–221 Mots-clés : Plantwide  Control--Throughput--Maximization--Case  Study Résumé : The impact of the basic plantwide regulatory control structure on maximizing the throughput using an explicit optimizing controller is quantitatively evaluated for a simple process module. The module consists of the reaction A + B → C occurring in a continuously stirred tank reactor followed by a distillation column separating the product from the recycled unreacted reactants. The column vapor boilup hitting a maximum acts as the bottleneck constraint limiting the throughput due to column flooding. Through an evaluation of reasonable plantwide control structures, the location of the throughput manipulator, the composition analyzer for overall component inventory balancing and the “local” column reflux management policy are shown to significantly affect the maximum throughput. Quantitative results show that locating the throughput manipulator close to and where possible at the bottleneck constraint reduces the throughput derating necessary due to disturbances. Designing the plantwide regulatory control system to minimize the process variability propagated into the bottleneck constraint emerges as the key heuristic from the case study. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900366r