Documents disponibles écrits par cet auteur

An analysis of some unit-specific event-based models for the short-term scheduling of noncontinuous processes / Jie Li in Industrial & engineering chemistry research, Vol. 49 N° 2 (Janvier 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 2 (Janvier 2010) . - pp 633–647 Titre : An analysis of some unit-specific event-based models for the short-term scheduling of noncontinuous processes Type de document : texte imprimé Auteurs : Jie Li, Auteur ; Susarla, Naresh, Auteur ; Iftekhar A. Karimi, Auteur Année de publication : 2010 Article en page(s) : pp 633–647 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Noncontinuous  processes  Semicontinuous  processes  Finite  storage  Unit-specific. Résumé : Several event-based formulations for scheduling noncontinuous processes have been reported in the past decade. In fact, some unit-specific event-based models have proved more efficient than other models on several literature problems. Recently, Janak and Floudas [Comput. Chem. Eng. 2008, 32 (4−5), 913−955] and Shaik and Floudas [Ind. Eng. Chem. Res. 2009, 48 (6), 2947−2964] have shown that, without allowing tasks to occur over multiple events, some unit-specific event-based models may lead to suboptimal solutions. In this work, we present five examples, involving batch and semicontinuous processes, to study the performance of some recent variants of unit-specific event-based models. The first two examples involve batch plants with finite storage as a shared resource for which a recent unit-specific event-based model [Shaik, M. A.; Floudas, C. A. Comput. Chem. Eng. 2008, 32 (1−2), 260−274] gives trivial or suboptimal solutions, depending on the example and data. Our analysis confirms that assuming a single event point for each task is one cause for the observed performance. When the tasks are allowed to span multiple events using the recent unified model of Shaik and Floudas [Ind. Eng. Chem. Res. 2009, 48 (6), 2947−2964], the issue is resolved. Three more examples involving semicontinuous processes are considered, the solutions of which explore the limitations of a recent unit-specific event-based model [Shaik, M. A.; Floudas, C. A. Ind. Eng. Chem. Res. 2007, 46 (6), 1764−1779]. In addition, the task sequencing constraints in the later model may require further study to ensure generality. The five examples presented in this work can serve as test problems for future scheduling models. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801879n [article] An analysis of some unit-specific event-based models for the short-term scheduling of noncontinuous processes [texte imprimé] / Jie Li, Auteur ; Susarla, Naresh, Auteur ; Iftekhar A. Karimi, Auteur . - 2010 . - pp 633–647. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 2 (Janvier 2010) . - pp 633–647 Mots-clés : Noncontinuous  processes  Semicontinuous  processes  Finite  storage  Unit-specific. Résumé : Several event-based formulations for scheduling noncontinuous processes have been reported in the past decade. In fact, some unit-specific event-based models have proved more efficient than other models on several literature problems. Recently, Janak and Floudas [Comput. Chem. Eng. 2008, 32 (4−5), 913−955] and Shaik and Floudas [Ind. Eng. Chem. Res. 2009, 48 (6), 2947−2964] have shown that, without allowing tasks to occur over multiple events, some unit-specific event-based models may lead to suboptimal solutions. In this work, we present five examples, involving batch and semicontinuous processes, to study the performance of some recent variants of unit-specific event-based models. The first two examples involve batch plants with finite storage as a shared resource for which a recent unit-specific event-based model [Shaik, M. A.; Floudas, C. A. Comput. Chem. Eng. 2008, 32 (1−2), 260−274] gives trivial or suboptimal solutions, depending on the example and data. Our analysis confirms that assuming a single event point for each task is one cause for the observed performance. When the tasks are allowed to span multiple events using the recent unified model of Shaik and Floudas [Ind. Eng. Chem. Res. 2009, 48 (6), 2947−2964], the issue is resolved. Three more examples involving semicontinuous processes are considered, the solutions of which explore the limitations of a recent unit-specific event-based model [Shaik, M. A.; Floudas, C. A. Ind. Eng. Chem. Res. 2007, 46 (6), 1764−1779]. In addition, the task sequencing constraints in the later model may require further study to ensure generality. The five examples presented in this work can serve as test problems for future scheduling models. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801879n

Minimizing boil-off losses in liquefied natural gas transportation / M. M. Faruque Hasan 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. 9571–9580 Titre : Minimizing boil-off losses in liquefied natural gas transportation Type de document : texte imprimé Auteurs : M. M. Faruque Hasan, Auteur ; Alfred Minghan Zheng, Auteur ; Iftekhar A. Karimi, Auteur Année de publication : 2010 Article en page(s) : pp. 9571–9580 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Liquefied  natural  gas  Boil-off  losses  LNG  transportation Résumé : Natural gas (NG) is the cleanest fossil fuel, which is most popular and economical after crude oil. Liquefied natural gas (LNG) is the most economical way of transporting NG over long distances. Because of LNG transportation and storage at −163 °C, boil-off losses are an unavoidable reality. While these are significant, few systematic studies on boil-off exist in the literature. In this work, we perform rigorous, realistic, detailed, and extensive dynamic simulation of boil-off during various steps of LNG transportation, study the effects of various factors such as nitrogen content, tank pressure, ambient temperature, voyage length, etc., and analyze the results. On the basis of our simulations, we determine optimal heels for several scenarios of lean LNG transportation. Our analysis shows that heel can be reduced by up to 40% for a typical long voyage of 20 days, compared to the usual industrial practice of 5% of the cargo, and the reduction is significantly more for the shorter voyages. Our computations suggest savings of millions of dollars from heel optimization alone in LNG transportation. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801975q [article] Minimizing boil-off losses in liquefied natural gas transportation [texte imprimé] / M. M. Faruque Hasan, Auteur ; Alfred Minghan Zheng, Auteur ; Iftekhar A. Karimi, Auteur . - 2010 . - pp. 9571–9580. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9571–9580 Mots-clés : Liquefied  natural  gas  Boil-off  losses  LNG  transportation Résumé : Natural gas (NG) is the cleanest fossil fuel, which is most popular and economical after crude oil. Liquefied natural gas (LNG) is the most economical way of transporting NG over long distances. Because of LNG transportation and storage at −163 °C, boil-off losses are an unavoidable reality. While these are significant, few systematic studies on boil-off exist in the literature. In this work, we perform rigorous, realistic, detailed, and extensive dynamic simulation of boil-off during various steps of LNG transportation, study the effects of various factors such as nitrogen content, tank pressure, ambient temperature, voyage length, etc., and analyze the results. On the basis of our simulations, we determine optimal heels for several scenarios of lean LNG transportation. Our analysis shows that heel can be reduced by up to 40% for a typical long voyage of 20 days, compared to the usual industrial practice of 5% of the cargo, and the reduction is significantly more for the shorter voyages. Our computations suggest savings of millions of dollars from heel optimization alone in LNG transportation. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801975q

Nonisothermal pore diffusion model for a kinetically controlled pressure swing adsorption process / Mona Khalighi in Industrial & engineering chemistry research, Vol. 51 N° 32 (Août 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 32 (Août 2012) . - pp. 10659–10670 Titre : Nonisothermal pore diffusion model for a kinetically controlled pressure swing adsorption process Type de document : texte imprimé Auteurs : Mona Khalighi, Auteur ; Shamsuzzaman Farooq, Auteur ; Iftekhar A. Karimi, Auteur Année de publication : 2012 Article en page(s) : pp. 10659–10670 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Nonisothermal  Adsorption  process Résumé : A nonisothermal micropore diffusion model has been developed to simulate kinetically controlled pressure swing adsorption (PSA) processes. In this model, a dual-site Langmuir isotherm represents adsorption equilibrium and micropore diffusivity depends on adsorbate concentration in the solid phase according to the chemical potential gradient as the driving force for diffusion. The model has been validated with published experimental data for the kinetically controlled separation of propylene/propane on 4A zeolite. Its performance has also been extensively compared with that of a bilinear driving force (bi-LDF) model for the same system. The results clearly show that a nonisothermal micropore diffusion model with concentration-dependent diffusivity is comprehensive and complete for kinetically selective systems. The conditions under which the bi-LDF model predictions may significantly deviate from those of the pore diffusion model have also been discussed. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie3004539 [article] Nonisothermal pore diffusion model for a kinetically controlled pressure swing adsorption process [texte imprimé] / Mona Khalighi, Auteur ; Shamsuzzaman Farooq, Auteur ; Iftekhar A. Karimi, Auteur . - 2012 . - pp. 10659–10670. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 32 (Août 2012) . - pp. 10659–10670 Mots-clés : Nonisothermal  Adsorption  process Résumé : A nonisothermal micropore diffusion model has been developed to simulate kinetically controlled pressure swing adsorption (PSA) processes. In this model, a dual-site Langmuir isotherm represents adsorption equilibrium and micropore diffusivity depends on adsorbate concentration in the solid phase according to the chemical potential gradient as the driving force for diffusion. The model has been validated with published experimental data for the kinetically controlled separation of propylene/propane on 4A zeolite. Its performance has also been extensively compared with that of a bilinear driving force (bi-LDF) model for the same system. The results clearly show that a nonisothermal micropore diffusion model with concentration-dependent diffusivity is comprehensive and complete for kinetically selective systems. The conditions under which the bi-LDF model predictions may significantly deviate from those of the pore diffusion model have also been discussed. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie3004539

Preliminary synthesis of fuel gas networks to conserve energy and preserve the environment / M. M. Faruque Hasan in Industrial & engineering chemistry research, Vol. 50 N° 12 (Juin 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 12 (Juin 2011) . - pp. 7414-7427 Titre : Preliminary synthesis of fuel gas networks to conserve energy and preserve the environment Type de document : texte imprimé Auteurs : M. M. Faruque Hasan, Auteur ; Iftekhar A. Karimi, Auteur ; Cory Matthew Avison, Auteur Année de publication : 2011 Article en page(s) : pp. 7414-7427 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Fuel  gas Résumé : Many chemical plants produce a variety of hydrocarbon gases with fuel value. A fuel gas network (FGN) integrates and uses these fuel gases appropriately to make best use of them. FGNs are critical components of many chemical plants including liquefied natural gas (LNG) plants and refineries. However, a systematic approach to design and operate realistic FGNs is not currently available in the literature. We address the optimal synthesis of an FGN with many practical features such as auxiliary equipment (valves, pipelines, compressors, heaters/ coolers, etc.), nonisobaric and nonisothermal operation, nonisothermal mixing, nonlinear fuel-quality specifications, fuel/utility costs, disposal and treatment costs, and emission standards. We develop a nonlinear program (NLP) based on a novel superstructure that embeds plausible alternatives for heating/cooling, moving, mixing, and splitting. We successfully apply our model to three real-life case studies from the LNG and refinery industries to demonstrate that an FGN can save 40―50% of the total energy costs of a plant and reduce the fuel-from-feed or fuel-from-product consumptions by similar amounts. This work represents an important contribution toward conserving energy, preserving the environment, and improving plant economics using advanced techniques of process systems optimization. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24239057 [article] Preliminary synthesis of fuel gas networks to conserve energy and preserve the environment [texte imprimé] / M. M. Faruque Hasan, Auteur ; Iftekhar A. Karimi, Auteur ; Cory Matthew Avison, Auteur . - 2011 . - pp. 7414-7427. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 12 (Juin 2011) . - pp. 7414-7427 Mots-clés : Fuel  gas Résumé : Many chemical plants produce a variety of hydrocarbon gases with fuel value. A fuel gas network (FGN) integrates and uses these fuel gases appropriately to make best use of them. FGNs are critical components of many chemical plants including liquefied natural gas (LNG) plants and refineries. However, a systematic approach to design and operate realistic FGNs is not currently available in the literature. We address the optimal synthesis of an FGN with many practical features such as auxiliary equipment (valves, pipelines, compressors, heaters/ coolers, etc.), nonisobaric and nonisothermal operation, nonisothermal mixing, nonlinear fuel-quality specifications, fuel/utility costs, disposal and treatment costs, and emission standards. We develop a nonlinear program (NLP) based on a novel superstructure that embeds plausible alternatives for heating/cooling, moving, mixing, and splitting. We successfully apply our model to three real-life case studies from the LNG and refinery industries to demonstrate that an FGN can save 40―50% of the total energy costs of a plant and reduce the fuel-from-feed or fuel-from-product consumptions by similar amounts. This work represents an important contribution toward conserving energy, preserving the environment, and improving plant economics using advanced techniques of process systems optimization. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24239057

Robustness measures for operation schedules subject to disruptions / Badarinath Karri in Industrial & engineering chemistry research, Vol. 48 N° 20 (Octobre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 20 (Octobre 2009) . - pp. 9204–9214 Titre : Robustness measures for operation schedules subject to disruptions Type de document : texte imprimé Auteurs : Badarinath Karri, Auteur ; Rajagopalan Srinivasan, Auteur ; Iftekhar A. Karimi, Auteur Année de publication : 2010 Article en page(s) : pp. 9204–9214 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Operation  schedules  Robustness  Disruptions Résumé : Operation schedules are frequently subject to disruptions or uncertainties that render them suboptimal or even infeasible to implement. Among the approaches that address stochastics in schedules, preventive methods incorporate uncertainty in the scheduling model to develop an a priori robust solution, while reactive techniques seek to repair the schedule after a disruption has occurred. In this work, an alternate perspective to schedules subject to disruptions is propounded. We seek to quantify robustness of a given schedule. Given a schedule and information about the possible disruptions, we evaluate its robustness in terms of the outcome for each possible disruption scenario. The consequent action(s) required on the part of the planner/scheduler, such as complete rescheduling, schedule repair, or none, is then identified and serves as the basis to classify the scenario into tiers. Robustness metrics are proposed based on the distribution of the tiers. Malleability is an indicator of a schedule’s ability to provide the performance as in the nominal case. Brittleness is a measure of the schedule’s feasibility and reschedulability under disruptions. These metrics are independent of economic indicators such as profit that are typically objectives in scheduling algorithms and can therefore be used as additional criteria to compare schedules. The proposed framework is illustrated using a refinery crude oil scheduling problem. Further, sensitivity studies are conducted to identify critical resources and disruption classes. Such studies can directly help a planner/scheduler to choose the best schedule overall for implementation and take preventive measures to safeguard critical elements. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900505a [article] Robustness measures for operation schedules subject to disruptions [texte imprimé] / Badarinath Karri, Auteur ; Rajagopalan Srinivasan, Auteur ; Iftekhar A. Karimi, Auteur . - 2010 . - pp. 9204–9214. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 20 (Octobre 2009) . - pp. 9204–9214 Mots-clés : Operation  schedules  Robustness  Disruptions Résumé : Operation schedules are frequently subject to disruptions or uncertainties that render them suboptimal or even infeasible to implement. Among the approaches that address stochastics in schedules, preventive methods incorporate uncertainty in the scheduling model to develop an a priori robust solution, while reactive techniques seek to repair the schedule after a disruption has occurred. In this work, an alternate perspective to schedules subject to disruptions is propounded. We seek to quantify robustness of a given schedule. Given a schedule and information about the possible disruptions, we evaluate its robustness in terms of the outcome for each possible disruption scenario. The consequent action(s) required on the part of the planner/scheduler, such as complete rescheduling, schedule repair, or none, is then identified and serves as the basis to classify the scenario into tiers. Robustness metrics are proposed based on the distribution of the tiers. Malleability is an indicator of a schedule’s ability to provide the performance as in the nominal case. Brittleness is a measure of the schedule’s feasibility and reschedulability under disruptions. These metrics are independent of economic indicators such as profit that are typically objectives in scheduling algorithms and can therefore be used as additional criteria to compare schedules. The proposed framework is illustrated using a refinery crude oil scheduling problem. Further, sensitivity studies are conducted to identify critical resources and disruption classes. Such studies can directly help a planner/scheduler to choose the best schedule overall for implementation and take preventive measures to safeguard critical elements. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900505a

Scheduling gasoline blending operations from recipe determination to shipping using unit slots / Jie Li in Industrial & engineering chemistry research, Vol. 50 N° 15 (Août 2011) 

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Selection of liquefied natural gas (LNG) contracts for minimizing procurement cost / Rajab Khalilpour in Industrial & engineering chemistry research, Vol. 50 N° 17 (Septembre 2011) 

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Selection of Third-party service contracts for chemical logistics / Mukta Bansal in Industrial & engineering chemistry research, Vol. 47 n°21 (Novembre 2008) 

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Supply chain redesign—multimodal optimization using a hybrid evolutionary algorithm / P. K. Naraharisetti in Industrial & engineering chemistry research, Vol. 48 N° 24 (Décembre 2009) 

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Supply chain redesign / P. K. Naraharisetti in Industrial & engineering chemistry research, Vol. 48 N° 24 (Décembre 2009) 

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