Documents disponibles écrits par cet auteur

Control and monitoring of a high recovery reverse osmosis desalination process / Charles W. McFall in Industrial & engineering chemistry research, Vol. 47 N°17 (Septembre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N°17 (Septembre 2008) . - p. 6698–6710 Titre : Control and monitoring of a high recovery reverse osmosis desalination process Type de document : texte imprimé Auteurs : Charles W. McFall, Auteur ; Alex Bartman, Auteur ; Panagiotis D. Christofides, Auteur Année de publication : 2008 Article en page(s) : p. 6698–6710 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Osmosis  desalination  process  Fault-tolerant  contro  Fault  detection  isolation  Lyapunov-based  control Résumé : Model-based control and monitoring such as feed-forward/feedback control, fault detection and isolation (FDI), and fault-tolerant control (FTC) techniques that utilize Lyapunov-based control laws are implemented on a high recovery reverse osmosis desalination plant model. A detailed mathematical model of a high recovery reverse osmosis plant is developed. This model incorporates the large spatial variations of concentration and flow rate that occur in membrane units during high recovery operation. Bounded nonlinear feedback and feed-forward controllers are developed and applied to this system. The application of these controllers with FDI and FTC is demonstrated in the context of a high recovery reverse osmosis process simulation. The first set of simulations demonstrates the ability to compensate for the effects of large time-varying disturbances in the feed concentration on specific process outputs with and without feed-forward control. The second set of simulations demonstrates the ability of FDI and FTC techniques to recover desired plant operation subject to actuator failures. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071559b [article] Control and monitoring of a high recovery reverse osmosis desalination process [texte imprimé] / Charles W. McFall, Auteur ; Alex Bartman, Auteur ; Panagiotis D. Christofides, Auteur . - 2008 . - p. 6698–6710. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N°17 (Septembre 2008) . - p. 6698–6710 Mots-clés : Osmosis  desalination  process  Fault-tolerant  contro  Fault  detection  isolation  Lyapunov-based  control Résumé : Model-based control and monitoring such as feed-forward/feedback control, fault detection and isolation (FDI), and fault-tolerant control (FTC) techniques that utilize Lyapunov-based control laws are implemented on a high recovery reverse osmosis desalination plant model. A detailed mathematical model of a high recovery reverse osmosis plant is developed. This model incorporates the large spatial variations of concentration and flow rate that occur in membrane units during high recovery operation. Bounded nonlinear feedback and feed-forward controllers are developed and applied to this system. The application of these controllers with FDI and FTC is demonstrated in the context of a high recovery reverse osmosis process simulation. The first set of simulations demonstrates the ability to compensate for the effects of large time-varying disturbances in the feed concentration on specific process outputs with and without feed-forward control. The second set of simulations demonstrates the ability of FDI and FTC techniques to recover desired plant operation subject to actuator failures. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071559b

Effect of thermodynamic restriction on energy cost optimization of RO membrane water desalination / Aihua Zhu in Industrial & engineering chemistry research, Vol. 48 N° 13 (Juillet 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 13 (Juillet 2009) . - pp. 6010–6021 Titre : Effect of thermodynamic restriction on energy cost optimization of RO membrane water desalination Type de document : texte imprimé Auteurs : Aihua Zhu, Auteur ; Panagiotis D. Christofides, Auteur ; Yoram Cohen, Auteur Année de publication : 2009 Article en page(s) : pp. 6010–6021 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Reverse  osmosis  membranes  Water  production Résumé : Advances in highly permeable reverse osmosis (RO) membranes have enabled desalting operations, in which it is practically feasible for the applied pressure to approach the osmotic pressure of the exit brine stream. However, energy cost remains a major contributor to the total cost of water produced by RO membrane desalination. Reduction of the overall cost of water production represents a major challenge and, in the present work, various elements of water production cost are evaluated from the viewpoint of optimization, with respect to various costs (energy, membrane area and permeability, brine management, and pressure drop), as well as the important thermodynamic cross-flow constraint, utilization of energy recovery devices, and operational feed and permeate flow rate constraints. More specifically, in the present study, an approach to the optimization of product water recovery at pressures that approach the osmotic pressure of the exit brine stream is presented via several simple RO process models that utilize highly permeable membranes. The results suggest that it is indeed feasible to refine RO processes to target for operation under the condition of minimum energy consumption, while considering the constraint imposed by the osmotic pressure, as specified by the thermodynamic cross-flow restriction. Although it is shown that multistage RO provides energy savings, this is at the expense of greater membrane area cost. Overall, as process costs above energy costs are added, the operational point for achieving minimum water production cost shifts to higher recoveries. Although the newer generation of RO membranes can allow high recovery operations at lower pressures, limitations due to mineral scaling and fouling impose additional constraints. The incorporation of these phenomena in the optimization approach is the subject of ongoing research. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800735q [article] Effect of thermodynamic restriction on energy cost optimization of RO membrane water desalination [texte imprimé] / Aihua Zhu, Auteur ; Panagiotis D. Christofides, Auteur ; Yoram Cohen, Auteur . - 2009 . - pp. 6010–6021. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 13 (Juillet 2009) . - pp. 6010–6021 Mots-clés : Reverse  osmosis  membranes  Water  production Résumé : Advances in highly permeable reverse osmosis (RO) membranes have enabled desalting operations, in which it is practically feasible for the applied pressure to approach the osmotic pressure of the exit brine stream. However, energy cost remains a major contributor to the total cost of water produced by RO membrane desalination. Reduction of the overall cost of water production represents a major challenge and, in the present work, various elements of water production cost are evaluated from the viewpoint of optimization, with respect to various costs (energy, membrane area and permeability, brine management, and pressure drop), as well as the important thermodynamic cross-flow constraint, utilization of energy recovery devices, and operational feed and permeate flow rate constraints. More specifically, in the present study, an approach to the optimization of product water recovery at pressures that approach the osmotic pressure of the exit brine stream is presented via several simple RO process models that utilize highly permeable membranes. The results suggest that it is indeed feasible to refine RO processes to target for operation under the condition of minimum energy consumption, while considering the constraint imposed by the osmotic pressure, as specified by the thermodynamic cross-flow restriction. Although it is shown that multistage RO provides energy savings, this is at the expense of greater membrane area cost. Overall, as process costs above energy costs are added, the operational point for achieving minimum water production cost shifts to higher recoveries. Although the newer generation of RO membranes can allow high recovery operations at lower pressures, limitations due to mineral scaling and fouling impose additional constraints. The incorporation of these phenomena in the optimization approach is the subject of ongoing research. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800735q

Energy consumption optimization of reverse osmosis membrane water desalination subject to feed salinity fluctuation / Aihua Zhu in Industrial & engineering chemistry research, Vol. 48 N° 21 (Novembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9581–9589 Titre : Energy consumption optimization of reverse osmosis membrane water desalination subject to feed salinity fluctuation Type de document : texte imprimé Auteurs : Aihua Zhu, Auteur ; Panagiotis D. Christofides, Auteur ; Yoram Cohen, Auteur Année de publication : 2010 Article en page(s) : pp. 9581–9589 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Reverse  osmosis  water  desalination  Feed  concentration  fluctuation  Time-varying  optimal  operation  strategy Résumé : We study the energy consumption optimization of a reverse osmosis water desalination process producing a constant permeate flow in the presence of feed concentration fluctuation. We propose a time-varying optimal operation strategy that can significantly reduce the specific energy consumption compared to time-invariant process operation. We present both computational and experimental results that demonstrate the effectiveness of the proposed optimal operation policy. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900729x [article] Energy consumption optimization of reverse osmosis membrane water desalination subject to feed salinity fluctuation [texte imprimé] / Aihua Zhu, Auteur ; Panagiotis D. Christofides, Auteur ; Yoram Cohen, Auteur . - 2010 . - pp. 9581–9589. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9581–9589 Mots-clés : Reverse  osmosis  water  desalination  Feed  concentration  fluctuation  Time-varying  optimal  operation  strategy Résumé : We study the energy consumption optimization of a reverse osmosis water desalination process producing a constant permeate flow in the presence of feed concentration fluctuation. We propose a time-varying optimal operation strategy that can significantly reduce the specific energy consumption compared to time-invariant process operation. We present both computational and experimental results that demonstrate the effectiveness of the proposed optimal operation policy. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900729x

Nonlinear model-based control of an experimental reverse-osmosis water desalination system / Alex R. Bartman in Industrial & engineering chemistry research, Vol. 48 N° 13 (Juillet 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 13 (Juillet 2009) . - pp. 6126–6136 Titre : Nonlinear model-based control of an experimental reverse-osmosis water desalination system Type de document : texte imprimé Auteurs : Alex R. Bartman, Auteur ; Panagiotis D. Christofides, Auteur ; Yoram Cohen, Auteur Année de publication : 2009 Article en page(s) : pp. 6126–6136 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Reverse-osmosis  membrane  water  desalination  system  Nonlinear  model-based  control  system Résumé : This work focuses on the design and implementation of a nonlinear model-based control system on an experimental reverse-osmosis (RO) membrane water desalination system to address large set-point changes and variations in feedwater salinity. A dynamic nonlinear lumped-parameter model is derived using first-principles, and its parameters are computed from experimental data to minimize the error between model predictions and experimental RO system response. This model then is used as the basis for the design of a nonlinear control system, using geometric control techniques. The nonlinear control system is implemented on the experimental RO system, and its set-point tracking and disturbance rejection capabilities are successfully evaluated. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900322x [article] Nonlinear model-based control of an experimental reverse-osmosis water desalination system [texte imprimé] / Alex R. Bartman, Auteur ; Panagiotis D. Christofides, Auteur ; Yoram Cohen, Auteur . - 2009 . - pp. 6126–6136. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 13 (Juillet 2009) . - pp. 6126–6136 Mots-clés : Reverse-osmosis  membrane  water  desalination  system  Nonlinear  model-based  control  system Résumé : This work focuses on the design and implementation of a nonlinear model-based control system on an experimental reverse-osmosis (RO) membrane water desalination system to address large set-point changes and variations in feedwater salinity. A dynamic nonlinear lumped-parameter model is derived using first-principles, and its parameters are computed from experimental data to minimize the error between model predictions and experimental RO system response. This model then is used as the basis for the design of a nonlinear control system, using geometric control techniques. The nonlinear control system is implemented on the experimental RO system, and its set-point tracking and disturbance rejection capabilities are successfully evaluated. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900322x

Plantwide fault isolation using nonlinear feedback control / Benjamin J. Ohran in Industrial & engineering chemistry research, Vol. 47 n°12 (Juin 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 n°12 (Juin 2008) . - p. 4220–4229 Titre : Plantwide fault isolation using nonlinear feedback control Type de document : texte imprimé Auteurs : Benjamin J. Ohran, Auteur ; Johnny Rau, Auteur ; Panagiotis D. Christofides, Auteur ; James F. Davis, Auteur Année de publication : 2008 Article en page(s) : p. 4220–4229 Note générale : Bibliogr. p. 4229 Langues : Anglais (eng) Mots-clés : Plantwide  fault  isolation;  Multiunit  chemical  process;  Nonlinear  model-based  control Résumé : Accurate detection and isolation of faults is a critical component of a reliable and efficient plantwide fault-tolerant control system. In a recent work (Ohran et al. AIChE J. 2008, 54, 223), we demonstrated that using a nonlinear controller to enforce a specific structure in the closed-loop system allows data-based detection and isolation of certain faults that would otherwise not be isolable using data-based techniques that do not impose the necessary closed-loop system structure. In this work, it is demonstrated through a multiunit chemical process example how this approach can be applied in a plantwide setting. By using nonlinear, model-based control laws to decouple certain states from faults of interest, unique fault responses in the state trajectories are obtained in the closed-loop system. On the basis of the unique responses, fault isolation becomes possible using data-based statistical process monitoring methods. The effectiveness of the method was tested through an extensive Monte Carlo simulation study of 500 runs for each of four fault scenarios and through comparison with a conventional (proportional−integral) feedback control law. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071548i [article] Plantwide fault isolation using nonlinear feedback control [texte imprimé] / Benjamin J. Ohran, Auteur ; Johnny Rau, Auteur ; Panagiotis D. Christofides, Auteur ; James F. Davis, Auteur . - 2008 . - p. 4220–4229. Bibliogr. p. 4229 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°12 (Juin 2008) . - p. 4220–4229 Mots-clés : Plantwide  fault  isolation;  Multiunit  chemical  process;  Nonlinear  model-based  control Résumé : Accurate detection and isolation of faults is a critical component of a reliable and efficient plantwide fault-tolerant control system. In a recent work (Ohran et al. AIChE J. 2008, 54, 223), we demonstrated that using a nonlinear controller to enforce a specific structure in the closed-loop system allows data-based detection and isolation of certain faults that would otherwise not be isolable using data-based techniques that do not impose the necessary closed-loop system structure. In this work, it is demonstrated through a multiunit chemical process example how this approach can be applied in a plantwide setting. By using nonlinear, model-based control laws to decouple certain states from faults of interest, unique fault responses in the state trajectories are obtained in the closed-loop system. On the basis of the unique responses, fault isolation becomes possible using data-based statistical process monitoring methods. The effectiveness of the method was tested through an extensive Monte Carlo simulation study of 500 runs for each of four fault scenarios and through comparison with a conventional (proportional−integral) feedback control law. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie071548i

Stochastic modeling and simultaneous regulation of surface roughness and porosity in thin film deposition / Gangshi Hu in Industrial & engineering chemistry research, Vol. 48 N° 14 (Juillet 2009) 

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