Modeling and simulation for control of the TEALARC liquified natural gas process / Finn Are Michelsen in Industrial & engineering chemistry research, Vol. 49 N° 16 (Août 2010)  

Public ISBD [article]  inIndustrial & engineering chemistry research > Vol. 49 N° 16 (Août 2010) . - pp. 7389–7397 Titre : Modeling and simulation for control of the TEALARC liquified natural gas process Type de document : texte imprimé Auteurs : Finn Are Michelsen, Auteur ; Ivar Johan Halvorsen, Auteur ; Berit Floor Lund, Auteur Année de publication : 2010 Article en page(s) : pp. 7389–7397 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Natural Gas Process Résumé : This article describes a dynamic, control relevant, mechanistic model of the TEALARC liquified natural gas process. The model is to be used for both steady-state and dynamic controllability analysis. The model therefore needs to be computationally light, but still include enough complexity such as to study the impact of capacity constraints on the control structure. Structured assumptions have been used to obtain simplified representations of gas/liquid flows and thermodynamic properties. The steady-state operating points of the dynamic model have been adapted to a given steady-state process design model. The paper demonstrates that the model is well suited for operability analysis. Steady-state and dynamic characteristics are illustrated. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901650e [article] Modeling and simulation for control of the TEALARC liquified natural gas process [texte imprimé] / Finn Are Michelsen, Auteur ; Ivar Johan Halvorsen, Auteur ; Berit Floor Lund, Auteur . - 2010 . - pp. 7389–7397. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 16 (Août 2010) . - pp. 7389–7397 Mots-clés : Natural Gas Process Résumé : This article describes a dynamic, control relevant, mechanistic model of the TEALARC liquified natural gas process. The model is to be used for both steady-state and dynamic controllability analysis. The model therefore needs to be computationally light, but still include enough complexity such as to study the impact of capacity constraints on the control structure. Structured assumptions have been used to obtain simplified representations of gas/liquid flows and thermodynamic properties. The steady-state operating points of the dynamic model have been adapted to a given steady-state process design model. The paper demonstrates that the model is well suited for operability analysis. Steady-state and dynamic characteristics are illustrated. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901650e

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Selection of optimal, controlled variables for the TEALARC LNG process / Finn Are Michelsen in Industrial & engineering chemistry research, Vol. 49 N° 18 (Septembre 2010)  

Public ISBD [article]  inIndustrial & engineering chemistry research > Vol. 49 N° 18 (Septembre 2010) . - pp. 8624–8632 Titre : Selection of optimal, controlled variables for the TEALARC LNG process Type de document : texte imprimé Auteurs : Finn Are Michelsen, Auteur ; Berit Floor Lund, Auteur ; Ivar Johan Halvorsen, Auteur Année de publication : 2010 Article en page(s) : pp. 8624–8632 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : LNG process Résumé : This article shows how controlled variables (CVs) of the regulatory control layer in a liquefied natural gas (LNG) plant can be chosen as linear combinations of measurements using self-optimizing control principles. By self-optimizing control, the CVs are chosen such that the set points of the CVs remain close to steady-state optimal despite disturbances, thus reducing the need for online reoptimization. Several methods for calculation of linear combinations within this framework are compared. Self-optimizing control design can also be used in the process design phase to place measurements by reducing a maximum candidate set of measurements to a best possible subset of measurements giving an acceptable loss. This article proposes a relatively simple method for successive selection (SS) of measurements and compares this approach to a more comprehensive branch-and-bound (BB) method for selection of measurements. The results indicate that, although the BB method gives lower average losses for very small subsets, the methods are comparable with respect to average losses for medium and large subsets, and the SS method outperforms the BB method in terms of computational load. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100081j [article] Selection of optimal, controlled variables for the TEALARC LNG process [texte imprimé] / Finn Are Michelsen, Auteur ; Berit Floor Lund, Auteur ; Ivar Johan Halvorsen, Auteur . - 2010 . - pp. 8624–8632. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 18 (Septembre 2010) . - pp. 8624–8632 Mots-clés : LNG process Résumé : This article shows how controlled variables (CVs) of the regulatory control layer in a liquefied natural gas (LNG) plant can be chosen as linear combinations of measurements using self-optimizing control principles. By self-optimizing control, the CVs are chosen such that the set points of the CVs remain close to steady-state optimal despite disturbances, thus reducing the need for online reoptimization. Several methods for calculation of linear combinations within this framework are compared. Self-optimizing control design can also be used in the process design phase to place measurements by reducing a maximum candidate set of measurements to a best possible subset of measurements giving an acceptable loss. This article proposes a relatively simple method for successive selection (SS) of measurements and compares this approach to a more comprehensive branch-and-bound (BB) method for selection of measurements. The results indicate that, although the BB method gives lower average losses for very small subsets, the methods are comparable with respect to average losses for medium and large subsets, and the SS method outperforms the BB method in terms of computational load. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie100081j

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The impact of process design decisions on operability and control of an LNG process / Finn Are Michelsen in Journal of natural gas science and engineering, Vol. 2 N° 4 (Septembre 2010)  

Public ISBD [article]  inJournal of natural gas science and engineering > Vol. 2 N° 4 (Septembre 2010) . - pp. 183–191 Titre : The impact of process design decisions on operability and control of an LNG process Type de document : texte imprimé Auteurs : Finn Are Michelsen, Auteur ; Ivar Johan Halvorsen, Auteur ; Berit Floor Lund, Auteur Année de publication : 2012 Article en page(s) : pp. 183–191 Note générale : Génie Chimique Langues : Anglais (eng) Mots-clés : Process design control Optimization Control structure Natural gas processing LNG Résumé : This paper describes a framework for integrated process and control structure design, and applies this framework to a Liquefied Natural Gas (LNG) process design. The overall aim of the work is to contribute to the methodological basis for improved design and operability of gas processing plants. Good operability means essentially that a plant can be operated easily, i.e. it can cope with unknown disturbances, offsets and other uncertainties with the smallest possible profit loss and without frequent shutdowns. This is obtained both through the design of the process itself and the design of the control system. There is a potential for improved operability of process plants, and thereby reduced profit loss, by considering these two aspects together. The main message is that this is handled by considering control structure design when process design changes are made. The main steps for developing an improved procedure for integrated process and control design are suggested. Such a procedure includes analyses of how altering key parameters in the process design affects the best possible control structure in the presence of defined disturbance scenarios. An important ingredient is the use of a dynamic, control relevant simulation model. The paper presents an analysis of how altering compressor size affects the choice of control structure for the Tealarc LNG process. This analysis has been carried out using a self-optimizing control methodology. ISSN : 1875-5100 En ligne : http://www.sciencedirect.com/science/article/pii/S1875510010000387 [article] The impact of process design decisions on operability and control of an LNG process [texte imprimé] / Finn Are Michelsen, Auteur ; Ivar Johan Halvorsen, Auteur ; Berit Floor Lund, Auteur . - 2012 . - pp. 183–191. Génie Chimique Langues : Anglais (eng) in Journal of natural gas science and engineering > Vol. 2 N° 4 (Septembre 2010) . - pp. 183–191 Mots-clés : Process design control Optimization Control structure Natural gas processing LNG Résumé : This paper describes a framework for integrated process and control structure design, and applies this framework to a Liquefied Natural Gas (LNG) process design. The overall aim of the work is to contribute to the methodological basis for improved design and operability of gas processing plants. Good operability means essentially that a plant can be operated easily, i.e. it can cope with unknown disturbances, offsets and other uncertainties with the smallest possible profit loss and without frequent shutdowns. This is obtained both through the design of the process itself and the design of the control system. There is a potential for improved operability of process plants, and thereby reduced profit loss, by considering these two aspects together. The main message is that this is handled by considering control structure design when process design changes are made. The main steps for developing an improved procedure for integrated process and control design are suggested. Such a procedure includes analyses of how altering key parameters in the process design affects the best possible control structure in the presence of defined disturbance scenarios. An important ingredient is the use of a dynamic, control relevant simulation model. The paper presents an analysis of how altering compressor size affects the choice of control structure for the Tealarc LNG process. This analysis has been carried out using a self-optimizing control methodology. ISSN : 1875-5100 En ligne : http://www.sciencedirect.com/science/article/pii/S1875510010000387

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