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Vol. 48 N° 21 - Novembre 2009 [texte imprimé] . - 2010 . - p. 9355-9771 : ill. ; 28 cm. Chemical engineering Langues : Français (fre)
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Ajouter le résultat dans votre panierAlternating current electrospraying / Siddharth Maheshwari in Industrial & engineering chemistry research, Vol. 48 N° 21 (Novembre 2009)
Titre : Alternating current electrospraying Type de document : texte imprimé Auteurs : Siddharth Maheshwari, Auteur ; Nishant Chetwani, Auteur ; Hsueh-Chia Chang, Auteur Année de publication : 2010 Article en page(s) : pp. 9358–9368 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Electrospraying Résumé : Electrospraying has attracted the attention of many researchers, ranging from analytical chemists to physicists, not only because of the rich physics associated with it, but also due to its wide-ranging applicability. Therefore, considerable research has been devoted to exploring this interfacial phenomenon. However, there still are areas of electrospraying that have remained unexplored. Until recently, significantly less effort had been directed toward electrospraying with an alternating current (ac) electric field in comparison to electrospraying with direct current (dc) field. This article comes as an attempt to summarize the work done on ac electrospraying in the authors’ group. A classification of this behavior into different frequency domains is provided, with an underlying mechanism that leads to physical features distinct from dc electrospraying. Potential uses of ac electrospraying, which cannot be realized by its dc counterpart, are also discussed. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801841r
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9358–9368[article] Alternating current electrospraying [texte imprimé] / Siddharth Maheshwari, Auteur ; Nishant Chetwani, Auteur ; Hsueh-Chia Chang, Auteur . - 2010 . - pp. 9358–9368.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9358–9368
Mots-clés : Electrospraying Résumé : Electrospraying has attracted the attention of many researchers, ranging from analytical chemists to physicists, not only because of the rich physics associated with it, but also due to its wide-ranging applicability. Therefore, considerable research has been devoted to exploring this interfacial phenomenon. However, there still are areas of electrospraying that have remained unexplored. Until recently, significantly less effort had been directed toward electrospraying with an alternating current (ac) electric field in comparison to electrospraying with direct current (dc) field. This article comes as an attempt to summarize the work done on ac electrospraying in the authors’ group. A classification of this behavior into different frequency domains is provided, with an underlying mechanism that leads to physical features distinct from dc electrospraying. Potential uses of ac electrospraying, which cannot be realized by its dc counterpart, are also discussed. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801841r Exemplaires
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Titre : Hybrid modeling of methane reformers. 1. a metamodel for the effectiveness factor of a catalyst pellet with complex geometry Type de document : texte imprimé Auteurs : André Luis Alberton, Auteur ; Marcio Schwaab, Auteur ; Carlos Eduardo Fontes, Auteur Année de publication : 2010 Article en page(s) : pp. 9369–9375 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Methane steam reforming Effectiveness factors Computational fluid dynamic Résumé : In this work, effectiveness factors for methane steam reforming reactions were obtained by solving mass and heat balance equations inside catalytic pellets for different reaction conditions and catalytic pellet geometries with the help of CFD (computational fluid dynamic) techniques. CFD computations were performed for real particle geometries and real kinetic rate expressions as described in the technical literature. A linear correlation was found between the effectiveness factor and the area/volume ratio, which characterizes the methane steam reforming as a diffusion-controlled process. The slopes of the straight lines depend of the external reaction conditions, thermal conductivity, and effective diffusivity. On the basis of the CFD results, empirical metamodels were built to represent effectiveness factors for methane steam reforming reactions at different reaction conditions. The metamodels can be easily inserted into a reactor model for simulation of the full industrial process. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801830q
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9369–9375[article] Hybrid modeling of methane reformers. 1. a metamodel for the effectiveness factor of a catalyst pellet with complex geometry [texte imprimé] / André Luis Alberton, Auteur ; Marcio Schwaab, Auteur ; Carlos Eduardo Fontes, Auteur . - 2010 . - pp. 9369–9375.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9369–9375
Mots-clés : Methane steam reforming Effectiveness factors Computational fluid dynamic Résumé : In this work, effectiveness factors for methane steam reforming reactions were obtained by solving mass and heat balance equations inside catalytic pellets for different reaction conditions and catalytic pellet geometries with the help of CFD (computational fluid dynamic) techniques. CFD computations were performed for real particle geometries and real kinetic rate expressions as described in the technical literature. A linear correlation was found between the effectiveness factor and the area/volume ratio, which characterizes the methane steam reforming as a diffusion-controlled process. The slopes of the straight lines depend of the external reaction conditions, thermal conductivity, and effective diffusivity. On the basis of the CFD results, empirical metamodels were built to represent effectiveness factors for methane steam reforming reactions at different reaction conditions. The metamodels can be easily inserted into a reactor model for simulation of the full industrial process. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801830q Exemplaires
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Titre : Hybrid modeling of methane reformers. 2. modeling of the industrial reactors Type de document : texte imprimé Auteurs : Marcio Schwaab, Auteur ; André Luis Alberton, Auteur ; Carlos Eduardo Fontes, Auteur Année de publication : 2010 Article en page(s) : pp. 9376–9382 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Methane reformers Industrial reactors Résumé : The steam reforming of methane is the main route for industrial production of hydrogen, used afterward for energy generation and production of chemicals. However, modeling of industrial methane reformers is not an easy task, due to the complex geometries of the employed catalyst pellets. The complex geometries are required to improve the contact between the gas phase and the solid catalyst. In this work a one-dimensional pseudohomogeneous model with axial mass and heat dispersion is used to model the tubular industrial reactors. The effect of the complex catalyst geometry of the pellets is considered with the help of empirical metamodels developed a priori for the effectiveness factors, based on CFD modeling of heat and mass balances inside pellets with different shapes and subject to distinct reactions conditions. It is shown that the proposed model can be successfully applied for simulation and design of industrial reformers, allowing for analysis of the effects introduced by distinct catalyst geometries on the performances of industrial operations. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801831m
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9376–9382[article] Hybrid modeling of methane reformers. 2. modeling of the industrial reactors [texte imprimé] / Marcio Schwaab, Auteur ; André Luis Alberton, Auteur ; Carlos Eduardo Fontes, Auteur . - 2010 . - pp. 9376–9382.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9376–9382
Mots-clés : Methane reformers Industrial reactors Résumé : The steam reforming of methane is the main route for industrial production of hydrogen, used afterward for energy generation and production of chemicals. However, modeling of industrial methane reformers is not an easy task, due to the complex geometries of the employed catalyst pellets. The complex geometries are required to improve the contact between the gas phase and the solid catalyst. In this work a one-dimensional pseudohomogeneous model with axial mass and heat dispersion is used to model the tubular industrial reactors. The effect of the complex catalyst geometry of the pellets is considered with the help of empirical metamodels developed a priori for the effectiveness factors, based on CFD modeling of heat and mass balances inside pellets with different shapes and subject to distinct reactions conditions. It is shown that the proposed model can be successfully applied for simulation and design of industrial reformers, allowing for analysis of the effects introduced by distinct catalyst geometries on the performances of industrial operations. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801831m Exemplaires
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Titre : Alkylation of xylenes with isopropyl alcohol over acidic clay supported catalysts : efficacy of 20% w/w Cs2.5H0.5PW12O40/K-10 clay Type de document : texte imprimé Auteurs : Ganapati D. Yadav, Auteur ; Shashikant B. Kamble, Auteur Année de publication : 2010 Article en page(s) : pp. 9383–9393 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Xylenes Alkylation Isopropyl alcohol Résumé : The alkylation of xylenes with propylene or isopropyl alcohol (IPA) over solid acid catalysts results in the formation of isopropyl xylenes (dimethyl cumenes). However, the use of propylene as an alkylating agent at very high temperatures leads to coke formation, which results in deactivation of the catalyst. The present work covers evaluation of acidic clay-supported catalysts and sulfated zirconia. A variety of solid acid catalysts such as K-10 clay, sulfated zirconia, Filtrol-24, 20% w/w dodecatungstophosphoric acid (H3PW12O40, DTP) supported on K-10 clay, and 20% w/w cesium-substituted dodecatungstophosphoric acid (Cs2.5H0.5PW12O40, Cs-DTP) supported on K-10 clay under much milder conditions. The best catalyst to achieve maximum conversion and selectivity was determined to be 20% w/w Cs-DTP/K-10 clay. The reactions were conducted in the liquid phase at relatively low reaction temperatures (160−190 °C). The reaction was performed without using any solvent, and the process subscribes to the principles of green chemistry. The catalytic activity has the following order: 20% w/w Cs-DTP/K-10 clay (most active) > 20% w/w DTP/K-10 clay > Filtrol-24 > sulfated zirconia > K-10 clay (least active). The desired product could be efficiently obtained, with selectivities up to 95% at an isopropanol conversion of 98% after 2 h over 20% w/w Cs-DTP/K-10 clay. This process can be a replacement for the existing processes that are based on zeolites, where high temperature and pressure are required. A systematic investigation of the effects of various operating parameters was accomplished and a mathematical model is developed to describe the reaction pathway and validated against experimental results. An overall second-order kinetic equation was used to fit the data, under the assumption that all the species are weakly adsorbed on the catalytic sites. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800737v
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9383–9393[article] Alkylation of xylenes with isopropyl alcohol over acidic clay supported catalysts : efficacy of 20% w/w Cs2.5H0.5PW12O40/K-10 clay [texte imprimé] / Ganapati D. Yadav, Auteur ; Shashikant B. Kamble, Auteur . - 2010 . - pp. 9383–9393.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9383–9393
Mots-clés : Xylenes Alkylation Isopropyl alcohol Résumé : The alkylation of xylenes with propylene or isopropyl alcohol (IPA) over solid acid catalysts results in the formation of isopropyl xylenes (dimethyl cumenes). However, the use of propylene as an alkylating agent at very high temperatures leads to coke formation, which results in deactivation of the catalyst. The present work covers evaluation of acidic clay-supported catalysts and sulfated zirconia. A variety of solid acid catalysts such as K-10 clay, sulfated zirconia, Filtrol-24, 20% w/w dodecatungstophosphoric acid (H3PW12O40, DTP) supported on K-10 clay, and 20% w/w cesium-substituted dodecatungstophosphoric acid (Cs2.5H0.5PW12O40, Cs-DTP) supported on K-10 clay under much milder conditions. The best catalyst to achieve maximum conversion and selectivity was determined to be 20% w/w Cs-DTP/K-10 clay. The reactions were conducted in the liquid phase at relatively low reaction temperatures (160−190 °C). The reaction was performed without using any solvent, and the process subscribes to the principles of green chemistry. The catalytic activity has the following order: 20% w/w Cs-DTP/K-10 clay (most active) > 20% w/w DTP/K-10 clay > Filtrol-24 > sulfated zirconia > K-10 clay (least active). The desired product could be efficiently obtained, with selectivities up to 95% at an isopropanol conversion of 98% after 2 h over 20% w/w Cs-DTP/K-10 clay. This process can be a replacement for the existing processes that are based on zeolites, where high temperature and pressure are required. A systematic investigation of the effects of various operating parameters was accomplished and a mathematical model is developed to describe the reaction pathway and validated against experimental results. An overall second-order kinetic equation was used to fit the data, under the assumption that all the species are weakly adsorbed on the catalytic sites. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800737v Exemplaires
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Titre : Novel mesoporous nanocomposite WOx-silicate acidic catalysts : ethylene and diethylether from ethanol Type de document : texte imprimé Auteurs : Dilek Varisli, Auteur ; Timur Dogu, Auteur ; Gulsen Dogu, Auteur Année de publication : 2010 Article en page(s) : pp. 9394–9401 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Solid acid catalysts Ethylene Diethylether Ethanol Résumé : Solid acid catalysts are extensively used in a number of industrially important catalytic reactions. Here, water-insoluble novel mesoporous solid acid catalysts, with a unique structure composed of WOx nanorods and W nanoballs within an amorphous silicate lattice, were synthesized following a one-pot hydrothermal route, using silicotungstic acid (STA) as the active component. Surface area of these catalysts are more than 2 orders of magnitude higher than that of pure STA, and they showed very high activity for the simultaneous production of ethylene and diethylether (DEE), which is an attractive transportation fuel alternate, from a nonpetroleum feedstock, namely ethanol. Depending upon the operating conditions, ethylene or DEE selectivities approaching 1.0 or 0.8 were obtained, respectively. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8008154
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9394–9401[article] Novel mesoporous nanocomposite WOx-silicate acidic catalysts : ethylene and diethylether from ethanol [texte imprimé] / Dilek Varisli, Auteur ; Timur Dogu, Auteur ; Gulsen Dogu, Auteur . - 2010 . - pp. 9394–9401.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9394–9401
Mots-clés : Solid acid catalysts Ethylene Diethylether Ethanol Résumé : Solid acid catalysts are extensively used in a number of industrially important catalytic reactions. Here, water-insoluble novel mesoporous solid acid catalysts, with a unique structure composed of WOx nanorods and W nanoballs within an amorphous silicate lattice, were synthesized following a one-pot hydrothermal route, using silicotungstic acid (STA) as the active component. Surface area of these catalysts are more than 2 orders of magnitude higher than that of pure STA, and they showed very high activity for the simultaneous production of ethylene and diethylether (DEE), which is an attractive transportation fuel alternate, from a nonpetroleum feedstock, namely ethanol. Depending upon the operating conditions, ethylene or DEE selectivities approaching 1.0 or 0.8 were obtained, respectively. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8008154 Exemplaires
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Titre : Characterization of sonochemical reactor for physicochemical transformations Type de document : texte imprimé Auteurs : Sravan, Kumar S., Auteur ; A. Balasubrahmanyam, Auteur ; Shyam, Sundar P, Auteur Année de publication : 2010 Article en page(s) : pp. 9402–9407 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Sonochemical reactor Physicochemical transformations Résumé : Complete knowledge of the pressure field distribution in a sonochemical reactor should be known for an efficient utilization of acoustic energy emitted by the transducers for targeted physicochemical transformations using cavitation phenomena. This work deals with the identification of the active and passive regions in the sonochemical reactor based on the measured pressure field intensities. Iodine liberation experiments based on the decomposition of aqueous potassium iodide (KI) as a representative of cavitationally induced chemical transformation were carried out at various locations in the bath type reactor and compared with the measured pressure intensities in the reactor. Similarly, extraction of natural dye from the bark of Pterocarpus marsupium tree has also been carried out as a representative of cavitationally induced physical transformation (extraction) and compared with the measured pressure intensities. Both the transformations indicate a similar trend of variation in the degree of transformation when correlated with the local pressure and indicated the existence of an optima, which is at a plane (≈3λ/2) away from the transducer surface. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801467n
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9402–9407[article] Characterization of sonochemical reactor for physicochemical transformations [texte imprimé] / Sravan, Kumar S., Auteur ; A. Balasubrahmanyam, Auteur ; Shyam, Sundar P, Auteur . - 2010 . - pp. 9402–9407.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9402–9407
Mots-clés : Sonochemical reactor Physicochemical transformations Résumé : Complete knowledge of the pressure field distribution in a sonochemical reactor should be known for an efficient utilization of acoustic energy emitted by the transducers for targeted physicochemical transformations using cavitation phenomena. This work deals with the identification of the active and passive regions in the sonochemical reactor based on the measured pressure field intensities. Iodine liberation experiments based on the decomposition of aqueous potassium iodide (KI) as a representative of cavitationally induced chemical transformation were carried out at various locations in the bath type reactor and compared with the measured pressure intensities in the reactor. Similarly, extraction of natural dye from the bark of Pterocarpus marsupium tree has also been carried out as a representative of cavitationally induced physical transformation (extraction) and compared with the measured pressure intensities. Both the transformations indicate a similar trend of variation in the degree of transformation when correlated with the local pressure and indicated the existence of an optima, which is at a plane (≈3λ/2) away from the transducer surface. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801467n Exemplaires
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Titre : Transesterification of edible and nonedible vegetable oils with alcohols over heteropolyacids supported on acid-treated clay Type de document : texte imprimé Auteurs : Vijay V. Bokade, Auteur ; Ganapati D. Yadav, Auteur Année de publication : 2010 Article en page(s) : pp. 9408–9415 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Acid-treated clay Vegetable oil Transesterification Résumé : In the current work, the novelty of heteropolyacid on clay (K-10) for the transesterification of vegetable oil with lower and higher alcohols is presented. Methyl esters (biodiesel) and glycerol were produced by the transesterification of vegetable oil with methanol in the presence of dodecatungestophosphoric acid (DTPA) supported on K-10 clay. The transesterification consists of three consecutive reversible reactions. Diglycerides (DG) and monoglycerides (MG) are intermediate products. The optimal catalyst concentration was 5% w/w of oil. Detailed studies were done for optimization of the process parameters. The rate of transesterification in a batch reactor increased with temperature up to 170 °C. Higher temperatures did not reduce the time to reach maximum conversion. The study was also extended to reactions of different edible and nonedible oils with lower and higher alcohols. The conversion of TG, DG, and MG seemed to be a second-order mechanism for the forward and reverse reactions, where the reaction system could be described as a pseudo-heterogeneous catalyzed reaction. The reaction rate constants for the TG, DG, and MG transesterification reactions were 0.12−0.84 h−1 and were higher for the MG reaction than for the TG transesterification. The activation energies were 4.2, 26, and 7.4 kcal/mol for the TG, DG, and MG transesterification reactions, respectively. The proposed kinetic model fits the experimental results well. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801543k
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9408–9415[article] Transesterification of edible and nonedible vegetable oils with alcohols over heteropolyacids supported on acid-treated clay [texte imprimé] / Vijay V. Bokade, Auteur ; Ganapati D. Yadav, Auteur . - 2010 . - pp. 9408–9415.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9408–9415
Mots-clés : Acid-treated clay Vegetable oil Transesterification Résumé : In the current work, the novelty of heteropolyacid on clay (K-10) for the transesterification of vegetable oil with lower and higher alcohols is presented. Methyl esters (biodiesel) and glycerol were produced by the transesterification of vegetable oil with methanol in the presence of dodecatungestophosphoric acid (DTPA) supported on K-10 clay. The transesterification consists of three consecutive reversible reactions. Diglycerides (DG) and monoglycerides (MG) are intermediate products. The optimal catalyst concentration was 5% w/w of oil. Detailed studies were done for optimization of the process parameters. The rate of transesterification in a batch reactor increased with temperature up to 170 °C. Higher temperatures did not reduce the time to reach maximum conversion. The study was also extended to reactions of different edible and nonedible oils with lower and higher alcohols. The conversion of TG, DG, and MG seemed to be a second-order mechanism for the forward and reverse reactions, where the reaction system could be described as a pseudo-heterogeneous catalyzed reaction. The reaction rate constants for the TG, DG, and MG transesterification reactions were 0.12−0.84 h−1 and were higher for the MG reaction than for the TG transesterification. The activation energies were 4.2, 26, and 7.4 kcal/mol for the TG, DG, and MG transesterification reactions, respectively. The proposed kinetic model fits the experimental results well. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801543k Exemplaires
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Titre : Framework for engineering the collective behavior of complex rhythmic systems Type de document : texte imprimé Auteurs : Craig G. Rusin, Auteur ; István Z. Kiss, Auteur ; Hiroshi Kori, Auteur Année de publication : 2010 Article en page(s) : pp. 9416–9422 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Engineering framework Dynamic structures Résumé : We have developed an engineering framework which utilizes experiment-based phase models to tune complex dynamic structures to desired states; weak, nondestructive signals are employed to alter interactions among nonlinear rhythmic elements. In this manuscript, we present an integrated overview and discussion of our recent studies in this area. Experiments on electrochemical reactions were conducted using multielectrode arrays to demonstrate the use of mild model-engineered feedback to achieve a desirable system response. Application is made to the tuning of phase difference between two oscillators, generation of sequentially visited dynamic cluster patterns, engineering dynamically differentiated cluster states, and to the design of a nonlinear antipacemaker for the destruction of synchronization of a population of interacting oscillators. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801807f
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9416–9422[article] Framework for engineering the collective behavior of complex rhythmic systems [texte imprimé] / Craig G. Rusin, Auteur ; István Z. Kiss, Auteur ; Hiroshi Kori, Auteur . - 2010 . - pp. 9416–9422.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9416–9422
Mots-clés : Engineering framework Dynamic structures Résumé : We have developed an engineering framework which utilizes experiment-based phase models to tune complex dynamic structures to desired states; weak, nondestructive signals are employed to alter interactions among nonlinear rhythmic elements. In this manuscript, we present an integrated overview and discussion of our recent studies in this area. Experiments on electrochemical reactions were conducted using multielectrode arrays to demonstrate the use of mild model-engineered feedback to achieve a desirable system response. Application is made to the tuning of phase difference between two oscillators, generation of sequentially visited dynamic cluster patterns, engineering dynamically differentiated cluster states, and to the design of a nonlinear antipacemaker for the destruction of synchronization of a population of interacting oscillators. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801807f Exemplaires
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Titre : Heterogeneous cobalt−saponite catalyst for liquid phase air oxidation of p-cresol Type de document : texte imprimé Auteurs : Vikas S. Kshirsagar, Auteur ; Ajit C. Garade, Auteur ; Kashinath R. Patil, Auteur Année de publication : 2010 Article en page(s) : pp. 9423–9427 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Heterogeneous Co− saponite p-Cresol Résumé : Heterogeneous Co−saponite was found to be an efficient catalyst for the liquid phase oxidation of p-cresol under mild conditions. Divalent cobalt ions were found to be in both the tetrahedral and octahedral positions of the saponite clay. Studies on the effect of reaction parameters showed that the rate of reaction increased with increase in Co loading from 5 to 13% and then remained constant up to 30% of Co loading, while the rate of oxidation showed a first-order dependence on the partial pressure of oxygen up to 300 kPa. Results of oxidation experiments over Co−saponite, in an inert atmosphere, and the XPS studies suggest Mars−van Krevelen pathway operating, which involves lattice oxygen of Co−saponite in the liquid phase oxidation of p-cresol. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801941e
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9423–9427[article] Heterogeneous cobalt−saponite catalyst for liquid phase air oxidation of p-cresol [texte imprimé] / Vikas S. Kshirsagar, Auteur ; Ajit C. Garade, Auteur ; Kashinath R. Patil, Auteur . - 2010 . - pp. 9423–9427.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9423–9427
Mots-clés : Heterogeneous Co− saponite p-Cresol Résumé : Heterogeneous Co−saponite was found to be an efficient catalyst for the liquid phase oxidation of p-cresol under mild conditions. Divalent cobalt ions were found to be in both the tetrahedral and octahedral positions of the saponite clay. Studies on the effect of reaction parameters showed that the rate of reaction increased with increase in Co loading from 5 to 13% and then remained constant up to 30% of Co loading, while the rate of oxidation showed a first-order dependence on the partial pressure of oxygen up to 300 kPa. Results of oxidation experiments over Co−saponite, in an inert atmosphere, and the XPS studies suggest Mars−van Krevelen pathway operating, which involves lattice oxygen of Co−saponite in the liquid phase oxidation of p-cresol. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801941e Exemplaires
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Titre : Effect of flow structures on heat transfer in single and multiphase jet reactors Type de document : texte imprimé Auteurs : Sagar S. Deshpande, Auteur ; Channamallikarjun S. Mathpati, Auteur ; Sagar S. Gulawani, Auteur Année de publication : 2010 Article en page(s) : pp. 9428–9440 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Hot film anemometry Heat transfer Multiphase jet reactors Résumé : High frequency experimental measurements by hot film anemometry (HFA) of liquid velocities and temperature in the region of vapor−liquid (VL) and solid−liquid (SL) interfaces for two important reactor types, namely, condensation jet and jet loop reactors, have been studied for their heat transfer characteristics. An algorithm for flow structure identification has been devised from velocity data based on (i) zero crossings and (ii) continuous wavelet transform. The wavelet transform algorithm is especially found to be useful in accurately estimating both the age and size distributions of eddies near interfaces in a multiscale framework. Using these distributions, it is shown that the calculated values of heat transfer coefficients (HTC) at the SL and VL interfaces show remarkable correspondence with the HTC values obtained experimentally from instantaneous temperature measurements. For this purpose, a modified capacitance model has been proposed that takes into account the information about both the age and size distributions. The results obtained by the present methodology show the improvement possible for calculating the HTC at interfaces when compared with the earlier surface renewal models. It may therefore be used to study the interaction between flow dynamics and heat transfer behavior in chemical process equipment. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900052s
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9428–9440[article] Effect of flow structures on heat transfer in single and multiphase jet reactors [texte imprimé] / Sagar S. Deshpande, Auteur ; Channamallikarjun S. Mathpati, Auteur ; Sagar S. Gulawani, Auteur . - 2010 . - pp. 9428–9440.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9428–9440
Mots-clés : Hot film anemometry Heat transfer Multiphase jet reactors Résumé : High frequency experimental measurements by hot film anemometry (HFA) of liquid velocities and temperature in the region of vapor−liquid (VL) and solid−liquid (SL) interfaces for two important reactor types, namely, condensation jet and jet loop reactors, have been studied for their heat transfer characteristics. An algorithm for flow structure identification has been devised from velocity data based on (i) zero crossings and (ii) continuous wavelet transform. The wavelet transform algorithm is especially found to be useful in accurately estimating both the age and size distributions of eddies near interfaces in a multiscale framework. Using these distributions, it is shown that the calculated values of heat transfer coefficients (HTC) at the SL and VL interfaces show remarkable correspondence with the HTC values obtained experimentally from instantaneous temperature measurements. For this purpose, a modified capacitance model has been proposed that takes into account the information about both the age and size distributions. The results obtained by the present methodology show the improvement possible for calculating the HTC at interfaces when compared with the earlier surface renewal models. It may therefore be used to study the interaction between flow dynamics and heat transfer behavior in chemical process equipment. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900052s Exemplaires
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Titre : Analysis of multiple reactions on a bipolar electrode Type de document : texte imprimé Auteurs : V. A. Juvekar, Auteur ; Rajkumar S. Patil, Auteur ; Anand V. P. Gurumoorthy, Auteur Année de publication : 2010 Article en page(s) : pp. 9441–9456 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Bipolar electrolysis Multiple reactions Résumé : Open bipolar electrolysis is a useful technique for conducting electrolytic processes in low concentrations of electrolytes or in nonaqueous solutions. In bipolar electrolysis, both cathodic and anodic reactions occur on the same electrode. In this paper, we analyze the case of multiple reactions occurring in a bipolar manner on a single metal spheroid. Simulations are conducted for various cases involving two redox reactions. Effects of the parameters such as intensity of the imposed electric field, the Nernst potentials, exchange current densities, and transfer coefficients on the current density and the extent of coupling between the reactions have been investigated. The asymptotic cases of low and high imposed electric fields are also considered, for which simple analytic solutions are derived. Together, they cover a major operating region of practical importance. Some important insights into coupling of the reactions on the bipolar electrode have been obtained. These provide useful criteria for design of bipolar electrolytic systems. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900437n
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9441–9456[article] Analysis of multiple reactions on a bipolar electrode [texte imprimé] / V. A. Juvekar, Auteur ; Rajkumar S. Patil, Auteur ; Anand V. P. Gurumoorthy, Auteur . - 2010 . - pp. 9441–9456.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9441–9456
Mots-clés : Bipolar electrolysis Multiple reactions Résumé : Open bipolar electrolysis is a useful technique for conducting electrolytic processes in low concentrations of electrolytes or in nonaqueous solutions. In bipolar electrolysis, both cathodic and anodic reactions occur on the same electrode. In this paper, we analyze the case of multiple reactions occurring in a bipolar manner on a single metal spheroid. Simulations are conducted for various cases involving two redox reactions. Effects of the parameters such as intensity of the imposed electric field, the Nernst potentials, exchange current densities, and transfer coefficients on the current density and the extent of coupling between the reactions have been investigated. The asymptotic cases of low and high imposed electric fields are also considered, for which simple analytic solutions are derived. Together, they cover a major operating region of practical importance. Some important insights into coupling of the reactions on the bipolar electrode have been obtained. These provide useful criteria for design of bipolar electrolytic systems. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900437n Exemplaires
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Titre : Activity and selectivity behavior of 1,2-epoxyethylbenzne hydrogenation in carbon dioxide solvent Type de document : texte imprimé Auteurs : Chandrashekhar V. Rode, Auteur ; Norihito Hiyoshi, Auteur ; Eiichi Mine, Auteur Année de publication : 2010 Article en page(s) : pp. 9457–9460 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Epoxyethylbenzne hydrogenation Carbon dioxide Résumé : Catalytic hydrogenation of 1,2-epoxyethylbenzene to 2-phenylethanol over charcoal-supported noble metal in carbon dioxide was studied, and the results were compared with those in heptane and methanol. Charcoal-supported palladium and platinum (Pd/C and Pt/C) catalysts were active metal species for the hydrogenation in solvents. The order of activities over palladium and platinum was heptane En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8018559
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9457–9460[article] Activity and selectivity behavior of 1,2-epoxyethylbenzne hydrogenation in carbon dioxide solvent [texte imprimé] / Chandrashekhar V. Rode, Auteur ; Norihito Hiyoshi, Auteur ; Eiichi Mine, Auteur . - 2010 . - pp. 9457–9460.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9457–9460
Mots-clés : Epoxyethylbenzne hydrogenation Carbon dioxide Résumé : Catalytic hydrogenation of 1,2-epoxyethylbenzene to 2-phenylethanol over charcoal-supported noble metal in carbon dioxide was studied, and the results were compared with those in heptane and methanol. Charcoal-supported palladium and platinum (Pd/C and Pt/C) catalysts were active metal species for the hydrogenation in solvents. The order of activities over palladium and platinum was heptane En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8018559 Exemplaires
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Titre : Entrainer based reactive distillation for esterification of ethylene glycol with acetic acid Type de document : texte imprimé Auteurs : Suman Thotla, Auteur ; Seethamraju Srinivas, Auteur ; Sanjay M. Mahajani, Auteur Année de publication : 2010 Article en page(s) : pp. 9461–9470 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Entrainer Reactive distillation Acetic acid Résumé : In this paper, we study the potential of entrainer in reactive distillation involving high boiling reactants to decrease the reactive stage temperature and for separation of one of the products to enhance the conversion. Esterification of ethylene glycol with acetic acid in the presence of Amberlyst 36 with 1,2-dichloro ethane (EDC), as an entrainer, is chosen as the model reaction. The effect of different parameters on selectivity of diacetate of ethylene glycol (DAEG) in entrainer based reactive distillation (EBRD) has been studied both through experiments and simulations. The results show that, by using entrainer, it is possible to obtain close to 100% selectivity toward diester even with a stoichiometric mole ratio, which is otherwise not possible in a conventional reactor. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801886q
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9461–9470[article] Entrainer based reactive distillation for esterification of ethylene glycol with acetic acid [texte imprimé] / Suman Thotla, Auteur ; Seethamraju Srinivas, Auteur ; Sanjay M. Mahajani, Auteur . - 2010 . - pp. 9461–9470.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9461–9470
Mots-clés : Entrainer Reactive distillation Acetic acid Résumé : In this paper, we study the potential of entrainer in reactive distillation involving high boiling reactants to decrease the reactive stage temperature and for separation of one of the products to enhance the conversion. Esterification of ethylene glycol with acetic acid in the presence of Amberlyst 36 with 1,2-dichloro ethane (EDC), as an entrainer, is chosen as the model reaction. The effect of different parameters on selectivity of diacetate of ethylene glycol (DAEG) in entrainer based reactive distillation (EBRD) has been studied both through experiments and simulations. The results show that, by using entrainer, it is possible to obtain close to 100% selectivity toward diester even with a stoichiometric mole ratio, which is otherwise not possible in a conventional reactor. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801886q Exemplaires
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Titre : Oxidation of benzyl alcohol to benzaldehyde by tert-butyl hydroperoxide over nanogold supported on TiO2 and other transition and rare-earth metal oxides Type de document : texte imprimé Auteurs : Vasant R. Choudhary, Auteur ; Deepa K. Dumbre, Auteur Année de publication : 2010 Article en page(s) : pp. 9471–9478 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Benzyl alcohol Oxidation Résumé : Liquid-phase oxidation of benzyl alcohol to benzaldehyde by tertiary butyl hydroperoxide (at 95 °C) over nanogold supported on TiO2 and other transition-metal oxides (viz, MnO2, Fe2O3, CoOx, NiO, CuO, ZnO, and ZrO2) or rare-earth oxides (viz, La2O3, Sm2O3, Eu2O3, and Yb2O3) by the homogeneous deposition−precipitation (HDP) method has been investigated. The Au/TiO2 catalyst, prepared using the HDP method, showed high activity and selectivity in the reaction. The ZrO2-supported nanogold catalyst (HDP) also showed very good performance. The Au/TiO2 catalyst that was prepared using the deposition−precipitation (DP) method, however, showed poor catalytic activity, mostly because of its much-lower gold loading and/or lower Au3+/Au0 ratio. Irrespective of the catalyst preparation method, the catalytic activity increased as the gold loading increased. The gold deposition method strongly influenced the amount of gold that was deposited on TiO2, the gold particle size distribution, and also the surface Au3+/Au0 ratio; using the HDP method, the gold deposition was much larger, the gold particle size was smaller, the gold particle size distribution was much narrower, and the Au3+/Au0 ratio was higher. Both the metallic and ionic gold species (Au0 and Au3+) are present in the Au/TiO2 catalyst. However, the Au3+ species are mostly responsible for the high catalytic activity in the oxidation process. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801883d
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9471–9478[article] Oxidation of benzyl alcohol to benzaldehyde by tert-butyl hydroperoxide over nanogold supported on TiO2 and other transition and rare-earth metal oxides [texte imprimé] / Vasant R. Choudhary, Auteur ; Deepa K. Dumbre, Auteur . - 2010 . - pp. 9471–9478.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9471–9478
Mots-clés : Benzyl alcohol Oxidation Résumé : Liquid-phase oxidation of benzyl alcohol to benzaldehyde by tertiary butyl hydroperoxide (at 95 °C) over nanogold supported on TiO2 and other transition-metal oxides (viz, MnO2, Fe2O3, CoOx, NiO, CuO, ZnO, and ZrO2) or rare-earth oxides (viz, La2O3, Sm2O3, Eu2O3, and Yb2O3) by the homogeneous deposition−precipitation (HDP) method has been investigated. The Au/TiO2 catalyst, prepared using the HDP method, showed high activity and selectivity in the reaction. The ZrO2-supported nanogold catalyst (HDP) also showed very good performance. The Au/TiO2 catalyst that was prepared using the deposition−precipitation (DP) method, however, showed poor catalytic activity, mostly because of its much-lower gold loading and/or lower Au3+/Au0 ratio. Irrespective of the catalyst preparation method, the catalytic activity increased as the gold loading increased. The gold deposition method strongly influenced the amount of gold that was deposited on TiO2, the gold particle size distribution, and also the surface Au3+/Au0 ratio; using the HDP method, the gold deposition was much larger, the gold particle size was smaller, the gold particle size distribution was much narrower, and the Au3+/Au0 ratio was higher. Both the metallic and ionic gold species (Au0 and Au3+) are present in the Au/TiO2 catalyst. However, the Au3+ species are mostly responsible for the high catalytic activity in the oxidation process. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801883d Exemplaires
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Titre : Hydroformylation of 1,4-diacetoxy-2-butene using HRh(CO)(PPh3)3 tethered on alumina as a catalyst : kinetic study Type de document : texte imprimé Auteurs : Rashmi Chansarkar, Auteur ; Ashutosh A. Kelkar, Auteur ; Raghunath V. Chaudhari, Auteur Année de publication : 2010 Article en page(s) : pp. 9479–9489 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : 1,4-diacetoxy-2-butene Kinetic study Résumé : Hydroformylation of 1,4-diacetoxy-2-butene (DAB) was studied using [HRh(CO)(PPh3)3] complex catalyst tethered on alumina using phosphotungstic acid (PTA) as an anchoring agent, with the aim to understand the product distribution, selectivity, and intrinsic kinetics. It was observed that with the tethered heterogeneous catalyst a simultaneous hydroformylation followed by deacetoxylation steps was possible, which is relevant for combining two steps in the sequence of synthesis of vitamin-A intermediate [2-formyl-4-acetoxy butene (FAB)]. 31P cross-polarization magic angle spinning nuclear magnetic resonance (CP MAS NMR) and infrared (IR) instrumental techniques were found be the most effective techniques to establish the catalyst structure and true heterogeneity. On the basis of the spectroscopic evidence, we postulate the loss of a PPh3 group during tethering to give HRh(CO)(PPh3)2−PTA−Al2O3 as a heterogeneous complex catalyst. Experimental data on the concentration−time and CO/H2 consumption−time profiles were obtained and the effects of DAB concentration, CO partial pressure, H2 partial pressure, and catalyst loading were studied in a 50 mL stirred batch reactor over a temperature range of 338−358 K. The analysis of solid−liquid−gas mass transfer effects was investigated to ensure that the reaction was operating in the kinetic regime. Various models were developed, and the best model was chosen by a model discrimination procedure. The agreement between the model prediction and the experimental data was found to be excellent. The activation energies for the hydroformylation and deacetoxylation steps were found to be 42.5 and 80.2 kJ/mol. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900269z
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9479–9489[article] Hydroformylation of 1,4-diacetoxy-2-butene using HRh(CO)(PPh3)3 tethered on alumina as a catalyst : kinetic study [texte imprimé] / Rashmi Chansarkar, Auteur ; Ashutosh A. Kelkar, Auteur ; Raghunath V. Chaudhari, Auteur . - 2010 . - pp. 9479–9489.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9479–9489
Mots-clés : 1,4-diacetoxy-2-butene Kinetic study Résumé : Hydroformylation of 1,4-diacetoxy-2-butene (DAB) was studied using [HRh(CO)(PPh3)3] complex catalyst tethered on alumina using phosphotungstic acid (PTA) as an anchoring agent, with the aim to understand the product distribution, selectivity, and intrinsic kinetics. It was observed that with the tethered heterogeneous catalyst a simultaneous hydroformylation followed by deacetoxylation steps was possible, which is relevant for combining two steps in the sequence of synthesis of vitamin-A intermediate [2-formyl-4-acetoxy butene (FAB)]. 31P cross-polarization magic angle spinning nuclear magnetic resonance (CP MAS NMR) and infrared (IR) instrumental techniques were found be the most effective techniques to establish the catalyst structure and true heterogeneity. On the basis of the spectroscopic evidence, we postulate the loss of a PPh3 group during tethering to give HRh(CO)(PPh3)2−PTA−Al2O3 as a heterogeneous complex catalyst. Experimental data on the concentration−time and CO/H2 consumption−time profiles were obtained and the effects of DAB concentration, CO partial pressure, H2 partial pressure, and catalyst loading were studied in a 50 mL stirred batch reactor over a temperature range of 338−358 K. The analysis of solid−liquid−gas mass transfer effects was investigated to ensure that the reaction was operating in the kinetic regime. Various models were developed, and the best model was chosen by a model discrimination procedure. The agreement between the model prediction and the experimental data was found to be excellent. The activation energies for the hydroformylation and deacetoxylation steps were found to be 42.5 and 80.2 kJ/mol. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900269z Exemplaires
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Titre : Adsorption/desorption studies of 224-trimethylpentane in β-Zeolite and mesoporous materials using a tapered element oscillating microbalance (TEOM) Type de document : texte imprimé Auteurs : Kening Gong, Auteur ; Tiepan Shi, Auteur ; Palghat A. Ramachandran, Auteur Année de publication : 2010 Article en page(s) : pp. 9490–9497 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : 224-Trimethylpentane β -Zeolite Mesoporous materials Résumé : The facile desorption of C8 and heavier products from solid acid alkylation catalysts is essential to thwart catalyst deactivation by fouling. To better understand this phenomenon, a tapered element oscillating microbalance (TEOM) was employed to investigate the adsorption/desorption characteristics of 224-trimethylpentane (224-TMP), a proxy C8 alkylate product, on β-zeolite and mesoporous materials (T = 298−473 K, P224-TMP = 0−0.3 bar). It is found that the 224-TMP desorption rates from saturated β-zeolite (by helium purging) are characterized by a rapid initial “burst” of 224-TMP followed by a rather long desorption phase. Complementary experimental and modeling investigations using pelletized β-zeolites of known sizes indicate that the adsorption rate and initial desorption (during the burst phase) rate of 224-TMP are controlled by meso-/macropore diffusion resistance external to the β-zeolite crystals and that the long transient could be due to pore diffusion resistance within the β-zeolite crystals. In contrast, mesoporous silica materials provide facile pore accessibility for large alkylate molecules such as 224-TMP, as evidenced by complete desorption of 224-TMP even at mild temperatures. These insights provide guidance for rational engineering of stable solid acid alkylation catalysts. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900334g
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9490–9497[article] Adsorption/desorption studies of 224-trimethylpentane in β-Zeolite and mesoporous materials using a tapered element oscillating microbalance (TEOM) [texte imprimé] / Kening Gong, Auteur ; Tiepan Shi, Auteur ; Palghat A. Ramachandran, Auteur . - 2010 . - pp. 9490–9497.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9490–9497
Mots-clés : 224-Trimethylpentane β -Zeolite Mesoporous materials Résumé : The facile desorption of C8 and heavier products from solid acid alkylation catalysts is essential to thwart catalyst deactivation by fouling. To better understand this phenomenon, a tapered element oscillating microbalance (TEOM) was employed to investigate the adsorption/desorption characteristics of 224-trimethylpentane (224-TMP), a proxy C8 alkylate product, on β-zeolite and mesoporous materials (T = 298−473 K, P224-TMP = 0−0.3 bar). It is found that the 224-TMP desorption rates from saturated β-zeolite (by helium purging) are characterized by a rapid initial “burst” of 224-TMP followed by a rather long desorption phase. Complementary experimental and modeling investigations using pelletized β-zeolites of known sizes indicate that the adsorption rate and initial desorption (during the burst phase) rate of 224-TMP are controlled by meso-/macropore diffusion resistance external to the β-zeolite crystals and that the long transient could be due to pore diffusion resistance within the β-zeolite crystals. In contrast, mesoporous silica materials provide facile pore accessibility for large alkylate molecules such as 224-TMP, as evidenced by complete desorption of 224-TMP even at mild temperatures. These insights provide guidance for rational engineering of stable solid acid alkylation catalysts. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900334g Exemplaires
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Titre : Water-dispersed conductive polypyrroles doped with lignosulfonate and the weak temperature dependence of electrical conductivity Type de document : texte imprimé Auteurs : Chao Yang, Auteur ; Peng Liu, Auteur Année de publication : 2010 Article en page(s) : pp. 9498–9503 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Water-dispersed conductive polypyrroles Chemical oxidative polymerization Lignosulfonate Résumé : The water-dispersed conductive polypyrroles (PPys) were prepared via the chemical oxidative polymerization with lignosulfonate (LGS), an inexpensive byproduct from pulp processing industries, as a dopant and template for tuning the properties of polypyrrole nanoparticles. The lignosulfonate doped polypyrrole (PPy/LGS) nanoparticles were characterized with Fourier transform infrared (FTIR), UV−vis, thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), and electric conductivity. The diameters of the PPy/LGS nanoparticles decreased from 100 to 20 nm with the increasing LGS. Their electrical conductivities were affected markedly by the dopant amount added. The PPy/LGS have weakly temperature-dependent conductivity over the entire temperature interval from 283 to 423 K. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900189j
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9498–9503[article] Water-dispersed conductive polypyrroles doped with lignosulfonate and the weak temperature dependence of electrical conductivity [texte imprimé] / Chao Yang, Auteur ; Peng Liu, Auteur . - 2010 . - pp. 9498–9503.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9498–9503
Mots-clés : Water-dispersed conductive polypyrroles Chemical oxidative polymerization Lignosulfonate Résumé : The water-dispersed conductive polypyrroles (PPys) were prepared via the chemical oxidative polymerization with lignosulfonate (LGS), an inexpensive byproduct from pulp processing industries, as a dopant and template for tuning the properties of polypyrrole nanoparticles. The lignosulfonate doped polypyrrole (PPy/LGS) nanoparticles were characterized with Fourier transform infrared (FTIR), UV−vis, thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), and electric conductivity. The diameters of the PPy/LGS nanoparticles decreased from 100 to 20 nm with the increasing LGS. Their electrical conductivities were affected markedly by the dopant amount added. The PPy/LGS have weakly temperature-dependent conductivity over the entire temperature interval from 283 to 423 K. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900189j Exemplaires
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Titre : Preparation and characterization of hybrid hydrotalcite-sulfonated polyetheretherketone (SPEEK) cation-exchange membranes Type de document : texte imprimé Auteurs : Tae Wook Kim, Auteur ; Muhammad Sahimi, Auteur ; Theodore T. Tsotsis, Auteur Année de publication : 2010 Article en page(s) : pp. 9504–9513 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Direct methanol fuel cells Cost-effective membrane Hydrotalcite particles Sulfonated poly(ether ether ketone) Résumé : Direct methanol fuel cells (DMFCs) can be operated using liquid methanol directly as a fuel. However, DMFCs face two major technical hurdles, namely, slow anodic methanol oxidation kinetics and methanol crossover across the polymer electrolyte membrane. Commercial membranes, such as Nafion, are expensive and more than 40% of the methanol is often lost through crossover during fuel-cell operation. Therefore, our study’s long-term goal is to develop a new, cost-effective membrane with superior methanol barrier properties, and reasonable proton conductivity. As part of this effort, we have prepared composite membranes by incorporating hydrotalcite (HT) particles into sulfonated poly(ether ether ketone) (SPEEK). Their properties are strongly dependent on the degree of sulfonation of the polymer matrix, and on the weight fraction of HT particles present in the hybrid membrane. Some of these HT-SPEEK hybrid membranes exhibit good properties, with the addition of the HT filler increasing the proton conductivity, while simultaneously decreasing the methanol permeability. The log(C/P) performance index of some of these membranes (where C/P is the ratio of the proton conductivity of the membrane divided by its methanol permeability) is comparable to that of the commercially available Nafion membranes. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801839u
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9504–9513[article] Preparation and characterization of hybrid hydrotalcite-sulfonated polyetheretherketone (SPEEK) cation-exchange membranes [texte imprimé] / Tae Wook Kim, Auteur ; Muhammad Sahimi, Auteur ; Theodore T. Tsotsis, Auteur . - 2010 . - pp. 9504–9513.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9504–9513
Mots-clés : Direct methanol fuel cells Cost-effective membrane Hydrotalcite particles Sulfonated poly(ether ether ketone) Résumé : Direct methanol fuel cells (DMFCs) can be operated using liquid methanol directly as a fuel. However, DMFCs face two major technical hurdles, namely, slow anodic methanol oxidation kinetics and methanol crossover across the polymer electrolyte membrane. Commercial membranes, such as Nafion, are expensive and more than 40% of the methanol is often lost through crossover during fuel-cell operation. Therefore, our study’s long-term goal is to develop a new, cost-effective membrane with superior methanol barrier properties, and reasonable proton conductivity. As part of this effort, we have prepared composite membranes by incorporating hydrotalcite (HT) particles into sulfonated poly(ether ether ketone) (SPEEK). Their properties are strongly dependent on the degree of sulfonation of the polymer matrix, and on the weight fraction of HT particles present in the hybrid membrane. Some of these HT-SPEEK hybrid membranes exhibit good properties, with the addition of the HT filler increasing the proton conductivity, while simultaneously decreasing the methanol permeability. The log(C/P) performance index of some of these membranes (where C/P is the ratio of the proton conductivity of the membrane divided by its methanol permeability) is comparable to that of the commercially available Nafion membranes. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801839u Exemplaires
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Titre : Self-similar dynamics of a flexible ring polymer in a fixed obstacle environment : a coarse-grained molecular model Type de document : texte imprimé Auteurs : Balaji V. S. Iyer, Auteur ; Ashish K. Lele, Auteur ; Vinay A. Juvekar, Auteur Année de publication : 2010 Article en page(s) : pp. 9514–9522 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Flexible ring polymers Molecular model Résumé : In this contribution we concern ourselves with an interesting problem, namely, the dynamics of ideal flexible ring polymers constrained in an array of fixed obstacles. The fundamental issue in this problem is to understand how a topologically constrained polymer chain is able to relax its conformation in the absence of chain ends. The key physics was provided in an elegant scaling theory by Rubinstein and co-workers (Obukhov, S. P.; Rubinstein, M.; Duke, T. Dynamics of a Ring Polymer in a Gel. Phys. Rev. Lett. 1994, 73, 1263−1267). In this work we develop a coarse-grained mean-field model based on the physical arguments of the scaling theory and derive constitutive relations for rings in fixed obstacle and melt environments. The model is composed of three distinct steps. In the first step the dynamics of an arbitrary section of a ring chain is worked out based on fractal Blob−Spring (BS) dynamics, and the center of mass diffusion and the relaxation spectrum of this section are determined. In the second step the center of mass diffusion obtained using the BS dynamics is used to model the one-dimensional diffusion of the section in a topologically constrained environment. In the final step we invoke the idea of dynamic self-similarity and argue that the dynamics described in the first and the second step, for any arbitrary section of the chain, applies to all sections of the chain. The constitutive relation is obtained consequently as the superposition of dynamic response of all sections of the ring chain. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900535v
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9514–9522[article] Self-similar dynamics of a flexible ring polymer in a fixed obstacle environment : a coarse-grained molecular model [texte imprimé] / Balaji V. S. Iyer, Auteur ; Ashish K. Lele, Auteur ; Vinay A. Juvekar, Auteur . - 2010 . - pp. 9514–9522.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9514–9522
Mots-clés : Flexible ring polymers Molecular model Résumé : In this contribution we concern ourselves with an interesting problem, namely, the dynamics of ideal flexible ring polymers constrained in an array of fixed obstacles. The fundamental issue in this problem is to understand how a topologically constrained polymer chain is able to relax its conformation in the absence of chain ends. The key physics was provided in an elegant scaling theory by Rubinstein and co-workers (Obukhov, S. P.; Rubinstein, M.; Duke, T. Dynamics of a Ring Polymer in a Gel. Phys. Rev. Lett. 1994, 73, 1263−1267). In this work we develop a coarse-grained mean-field model based on the physical arguments of the scaling theory and derive constitutive relations for rings in fixed obstacle and melt environments. The model is composed of three distinct steps. In the first step the dynamics of an arbitrary section of a ring chain is worked out based on fractal Blob−Spring (BS) dynamics, and the center of mass diffusion and the relaxation spectrum of this section are determined. In the second step the center of mass diffusion obtained using the BS dynamics is used to model the one-dimensional diffusion of the section in a topologically constrained environment. In the final step we invoke the idea of dynamic self-similarity and argue that the dynamics described in the first and the second step, for any arbitrary section of the chain, applies to all sections of the chain. The constitutive relation is obtained consequently as the superposition of dynamic response of all sections of the ring chain. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900535v Exemplaires
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Titre : Multiobjective optimization of an industrial LPG thermal cracker using a first principles model Type de document : texte imprimé Auteurs : S. R. Nabavi, Auteur ; G.P. Rangaiah, Auteur ; A. Niaei, Auteur Année de publication : 2010 Article en page(s) : pp. 9523–9533 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Industrial liquefied petroleum gas Butane thermal cracker Propane Genetic algorithm Résumé : Thermal cracking of hydrocarbons in the presence of steam is the most important process for the production of ethylene and propylene, which are the raw materials for many petrochemicals. In this work, multiobjective optimization (MOO) of an industrial LPG (liquefied petroleum gas containing mainly propane and butane) thermal cracker is studied using the elitist nondominated sorting genetic algorithm adapted with the jumping gene operator, NSGA-II-aJG. A first principles model based on free radical mechanism for LPG thermal cracking is employed for optimization. Several bi- and triobjective optimization problems are solved; these problems involved maximization of annual ethylene/propylene production, selectivity and run length, and minimization of severity and total heat duty per year. Feed flow rate, steam ratio, inlet temperature, coil outlet temperature, and pressure are the decision variables. MOO of the LPG thermal cracker provides a range of optimal operating conditions and objective values, with the triobjective optimization giving more optimal solutions compared to those from the biobjective optimization for the objectives considered. With this detailed knowledge, a suitable operating point can be selected based on specific requirements in the particular plant. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801409m
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9523–9533[article] Multiobjective optimization of an industrial LPG thermal cracker using a first principles model [texte imprimé] / S. R. Nabavi, Auteur ; G.P. Rangaiah, Auteur ; A. Niaei, Auteur . - 2010 . - pp. 9523–9533.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9523–9533
Mots-clés : Industrial liquefied petroleum gas Butane thermal cracker Propane Genetic algorithm Résumé : Thermal cracking of hydrocarbons in the presence of steam is the most important process for the production of ethylene and propylene, which are the raw materials for many petrochemicals. In this work, multiobjective optimization (MOO) of an industrial LPG (liquefied petroleum gas containing mainly propane and butane) thermal cracker is studied using the elitist nondominated sorting genetic algorithm adapted with the jumping gene operator, NSGA-II-aJG. A first principles model based on free radical mechanism for LPG thermal cracking is employed for optimization. Several bi- and triobjective optimization problems are solved; these problems involved maximization of annual ethylene/propylene production, selectivity and run length, and minimization of severity and total heat duty per year. Feed flow rate, steam ratio, inlet temperature, coil outlet temperature, and pressure are the decision variables. MOO of the LPG thermal cracker provides a range of optimal operating conditions and objective values, with the triobjective optimization giving more optimal solutions compared to those from the biobjective optimization for the objectives considered. With this detailed knowledge, a suitable operating point can be selected based on specific requirements in the particular plant. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801409m Exemplaires
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Titre : Two-step reactive distillation process for cyclohexanol production from cyclohexene Type de document : texte imprimé Auteurs : Amit Katariya, Auteur ; Hannsjorg Freund, Auteur ; Kai Sundmacher, Auteur Année de publication : 2010 Article en page(s) : pp. 9534–9545 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Cyclohexanol Reactive distillation Cyclohexene Résumé : The present work deals with a novel and attractive alternative process route for the production of cyclohexanol by indirect hydration of cyclohexene using reactive distillation. The proposed two-step process comprises the esterification of cyclohexene with formic acid followed by the hydrolysis of the formed ester. The principle feasibility of this new process has recently been proved by means of residue curve analysis [Steyer et al. Ind. Eng. Chem. Res. 2008, 47, 9581−9587]. In the present contribution, detailed equilibrium stage simulations are performed to identify the optimum design and operating conditions for the coupled reactive distillation column scheme. The simulations reveal that it is possible to achieve almost complete conversion of cyclohexene to cyclohexanol with a comparatively low amount of catalyst. To the best of our knowledge, this is the first time that such an outstanding performance of a process for the production of cyclohexanol is reported. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801649v
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9534–9545[article] Two-step reactive distillation process for cyclohexanol production from cyclohexene [texte imprimé] / Amit Katariya, Auteur ; Hannsjorg Freund, Auteur ; Kai Sundmacher, Auteur . - 2010 . - pp. 9534–9545.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9534–9545
Mots-clés : Cyclohexanol Reactive distillation Cyclohexene Résumé : The present work deals with a novel and attractive alternative process route for the production of cyclohexanol by indirect hydration of cyclohexene using reactive distillation. The proposed two-step process comprises the esterification of cyclohexene with formic acid followed by the hydrolysis of the formed ester. The principle feasibility of this new process has recently been proved by means of residue curve analysis [Steyer et al. Ind. Eng. Chem. Res. 2008, 47, 9581−9587]. In the present contribution, detailed equilibrium stage simulations are performed to identify the optimum design and operating conditions for the coupled reactive distillation column scheme. The simulations reveal that it is possible to achieve almost complete conversion of cyclohexene to cyclohexanol with a comparatively low amount of catalyst. To the best of our knowledge, this is the first time that such an outstanding performance of a process for the production of cyclohexanol is reported. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801649v Exemplaires
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Titre : A neural network and a genetic algorithm for multiobjective scheduling of semiconductor manufacturing plants Type de document : texte imprimé Auteurs : O. Baez Senties, Auteur ; C. Azzaro-Pantel, Auteur ; L. Pibouleau, Auteur Année de publication : 2010 Article en page(s) : pp. 9546–9555 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Artificial neural network technique Multiobjective genetic algorithm Semiconductor manufacturing plants Résumé : Scheduling of semiconductor wafer fabrication system is identified as a complex problem, involving multiple objectives to be satisfied simultaneously (maximization of workstation utilization and minimization of waiting time and storage, for instance). In this study, we propose a methodology based on an artificial neural network technique, for computing the various objective functions, embedded into a multiobjective genetic algorithm for multidecision scheduling problems in a semiconductor wafer fabrication environment. A discrete event simulator, developed and validated in our previous works, serves here to feed the neural network. Six criteria related to both equipment (facility average utilization) and products (average cycle time (ACT), standard deviation of ACT, average waiting time, work in process, and total storage) are chosen as significant performance indexes of the workshop. The optimization variables are the time between campaigns and the release time of batches into the plant. An industrial size example is taken as a test bench to validate the approach. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8018577
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9546–9555[article] A neural network and a genetic algorithm for multiobjective scheduling of semiconductor manufacturing plants [texte imprimé] / O. Baez Senties, Auteur ; C. Azzaro-Pantel, Auteur ; L. Pibouleau, Auteur . - 2010 . - pp. 9546–9555.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9546–9555
Mots-clés : Artificial neural network technique Multiobjective genetic algorithm Semiconductor manufacturing plants Résumé : Scheduling of semiconductor wafer fabrication system is identified as a complex problem, involving multiple objectives to be satisfied simultaneously (maximization of workstation utilization and minimization of waiting time and storage, for instance). In this study, we propose a methodology based on an artificial neural network technique, for computing the various objective functions, embedded into a multiobjective genetic algorithm for multidecision scheduling problems in a semiconductor wafer fabrication environment. A discrete event simulator, developed and validated in our previous works, serves here to feed the neural network. Six criteria related to both equipment (facility average utilization) and products (average cycle time (ACT), standard deviation of ACT, average waiting time, work in process, and total storage) are chosen as significant performance indexes of the workshop. The optimization variables are the time between campaigns and the release time of batches into the plant. An industrial size example is taken as a test bench to validate the approach. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8018577 Exemplaires
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Titre : Tracking the dynamics of the supply chain for enhanced production sustainability Type de document : texte imprimé Auteurs : Puigjaner, Luis, Auteur ; José Miguel Lainez, Auteur ; Carlos Rodrigo Álvarez, Auteur Année de publication : 2010 Article en page(s) : pp. 9556–9570 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Chain design− planning model Scheduling formulation Résumé : One of the key components of enterprise-wide optimization (EWO) is decision-making coordination and integration at all decision levels. In this paper, a supply chain design−planning model, which translates a recipe representation to the supply chain environment, is coupled with a scheduling formulation so that decision levels integration is achieved. This approach enabled us to assess the impact of considering scheduling aspects of process operations in the design of a supply chain network. A comparison of the proposed scheme and the traditional hierarchical approach shows the significance of such integration. Moreover, the scheduling details enable the dynamics of the supply chain to be tracked. We show the degree to which a holistic decision-making model within a model predictive control framework is able to react to incidents occurring in the supply chain components, including disturbances arising from local monitoring, control, and diagnosis of incidents in real time. Finally, a decomposition technique is applied to reduce the computational burden associated with the monolithic model solution. Validation of the proposed approach and the resulting potential benefits are highlighted by a case study. Moreover, the results obtained from this particular case study are examined and discussed with respect to future work. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801973n
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9556–9570[article] Tracking the dynamics of the supply chain for enhanced production sustainability [texte imprimé] / Puigjaner, Luis, Auteur ; José Miguel Lainez, Auteur ; Carlos Rodrigo Álvarez, Auteur . - 2010 . - pp. 9556–9570.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9556–9570
Mots-clés : Chain design− planning model Scheduling formulation Résumé : One of the key components of enterprise-wide optimization (EWO) is decision-making coordination and integration at all decision levels. In this paper, a supply chain design−planning model, which translates a recipe representation to the supply chain environment, is coupled with a scheduling formulation so that decision levels integration is achieved. This approach enabled us to assess the impact of considering scheduling aspects of process operations in the design of a supply chain network. A comparison of the proposed scheme and the traditional hierarchical approach shows the significance of such integration. Moreover, the scheduling details enable the dynamics of the supply chain to be tracked. We show the degree to which a holistic decision-making model within a model predictive control framework is able to react to incidents occurring in the supply chain components, including disturbances arising from local monitoring, control, and diagnosis of incidents in real time. Finally, a decomposition technique is applied to reduce the computational burden associated with the monolithic model solution. Validation of the proposed approach and the resulting potential benefits are highlighted by a case study. Moreover, the results obtained from this particular case study are examined and discussed with respect to future work. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801973n Exemplaires
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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
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9571–9580[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 Exemplaires
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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
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9581–9589[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 Exemplaires
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Titre : Networked control of distributed energy resources : application to solid oxide fuel cells Type de document : texte imprimé Auteurs : Yulei Sun, Auteur ; Sathyendra Ghantasala, Auteur ; Nael H. El-Farra, Auteur Année de publication : 2010 Article en page(s) : pp. 9590–9602 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Distributed energy resources Ssolid oxide fuel cell Résumé : This paper presents a model-based networked control approach for managing distributed energy resources (DERs) over communication networks. As a model system, we consider a solid oxide fuel cell (SOFC) plant that communicates with the central controller over a bandwidth-constrained communication network that is shared by several other DERs. The objective is to regulate the power output of the fuel cell while keeping the communication requirements with the controller to a minimum in order to reduce unnecessary network utilization and minimize the susceptibility of the SOFC plant to possible communication disruptions in the network. Initially, a feedback control law is designed to regulate the power output of the SOFC plant at a desired set-point by manipulating the inlet fuel flow rate. Network utilization is then reduced by minimizing the rate of transfer of information between the fuel cell sensors and the central controller without sacrificing the desired stability or performance properties. To this end, a dynamic model of the SOFC plant is embedded in the controller to approximate the dynamics of the plant when measurements are not transmitted by the sensors, and the state of the model is updated using the actual state that is provided by the SOFC plant sensors at discrete time instances. When full-state measurements are not available, an appropriate state observer is included in the control structure to generate state estimates from the measured outputs, which are then used to update the model states. An explicit characterization of the maximum allowable transfer time between the sensor suite of the SOFC plant and the controller (i.e., the minimum allowable communication rate) is obtained under both state and output feedback control in terms of plant-model mismatch and the choice of control law. The characterization accounts for both stability and performance considerations. Finally, numerical simulations that demonstrate the implementation of the networked control architecture and its disturbance handling capabilities are presented. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9008869
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9590–9602[article] Networked control of distributed energy resources : application to solid oxide fuel cells [texte imprimé] / Yulei Sun, Auteur ; Sathyendra Ghantasala, Auteur ; Nael H. El-Farra, Auteur . - 2010 . - pp. 9590–9602.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9590–9602
Mots-clés : Distributed energy resources Ssolid oxide fuel cell Résumé : This paper presents a model-based networked control approach for managing distributed energy resources (DERs) over communication networks. As a model system, we consider a solid oxide fuel cell (SOFC) plant that communicates with the central controller over a bandwidth-constrained communication network that is shared by several other DERs. The objective is to regulate the power output of the fuel cell while keeping the communication requirements with the controller to a minimum in order to reduce unnecessary network utilization and minimize the susceptibility of the SOFC plant to possible communication disruptions in the network. Initially, a feedback control law is designed to regulate the power output of the SOFC plant at a desired set-point by manipulating the inlet fuel flow rate. Network utilization is then reduced by minimizing the rate of transfer of information between the fuel cell sensors and the central controller without sacrificing the desired stability or performance properties. To this end, a dynamic model of the SOFC plant is embedded in the controller to approximate the dynamics of the plant when measurements are not transmitted by the sensors, and the state of the model is updated using the actual state that is provided by the SOFC plant sensors at discrete time instances. When full-state measurements are not available, an appropriate state observer is included in the control structure to generate state estimates from the measured outputs, which are then used to update the model states. An explicit characterization of the maximum allowable transfer time between the sensor suite of the SOFC plant and the controller (i.e., the minimum allowable communication rate) is obtained under both state and output feedback control in terms of plant-model mismatch and the choice of control law. The characterization accounts for both stability and performance considerations. Finally, numerical simulations that demonstrate the implementation of the networked control architecture and its disturbance handling capabilities are presented. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9008869 Exemplaires
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Titre : Model migration for development of a new process model Type de document : texte imprimé Auteurs : Junde Lu, Auteur ; Yuan Yao, Auteur ; Furong Gao, Auteur Année de publication : 2010 Article en page(s) : pp. 9603–9610 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Data-based process models Model migration method Résumé : Data-based process models are usually developed by fitting input−output data collected on a particular process. The model built on one particular process becomes invalid with another similar process. Traditional data-based modeling methods have to completely rebuild a new process model on a similar process, leading to repetition of a large number of experiments, if process similarities between two similar processes are ignored. Effective use and extraction of these process similarities and migration of the existing process model to the new process can require a fewer number of experiments for the development of a new process model, resulting in savings of time, cost, and effort. In this paper, we present a model migration method that can quickly model a new process based on an existing base model and contrast information between the base model and the new process. The method developed involves a procedure of six steps: information extraction from the base model, initial design of experiments, slope/bias correction (SBC) to the base model, outlier detection and assessment, further design of experiments, and development of the new model by combining local difference models and the corrected base model. An example is provided to illustrate the new model development strategy for predicting injection molded part weight, taking advantage of an existing model. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8013296
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9603–9610[article] Model migration for development of a new process model [texte imprimé] / Junde Lu, Auteur ; Yuan Yao, Auteur ; Furong Gao, Auteur . - 2010 . - pp. 9603–9610.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9603–9610
Mots-clés : Data-based process models Model migration method Résumé : Data-based process models are usually developed by fitting input−output data collected on a particular process. The model built on one particular process becomes invalid with another similar process. Traditional data-based modeling methods have to completely rebuild a new process model on a similar process, leading to repetition of a large number of experiments, if process similarities between two similar processes are ignored. Effective use and extraction of these process similarities and migration of the existing process model to the new process can require a fewer number of experiments for the development of a new process model, resulting in savings of time, cost, and effort. In this paper, we present a model migration method that can quickly model a new process based on an existing base model and contrast information between the base model and the new process. The method developed involves a procedure of six steps: information extraction from the base model, initial design of experiments, slope/bias correction (SBC) to the base model, outlier detection and assessment, further design of experiments, and development of the new model by combining local difference models and the corrected base model. An example is provided to illustrate the new model development strategy for predicting injection molded part weight, taking advantage of an existing model. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8013296 Exemplaires
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Titre : A coupled strategy for the solution of NLP and MINLP optimization problems : benefits and pitfalls Type de document : texte imprimé Auteurs : Helder G. Silva, Auteur ; Romualdo L. R. Salcedo, Auteur Année de publication : 2010 Article en page(s) : pp. 9611–9621 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Nonlinear programming problems Mixed-integer nonlinear Stochastic optimizers Résumé : This paper presents a strategy for the solution of nonlinear programming (NLP) and mixed-integer nonlinear programming (MINLP) problems, based on the coupling of the equation-oriented simulator ASCEND IV with the stochastic optimizers MSGA and MSIMPSA. Both NLP and MINLP formulations of a reactive distillation example were explored. The results show that the connection between the two software blocks was successfully established. Despite the highly nonlinear behavior of the proposed example, the results presented generally agree with those previously obtained for the same case study using other approaches, namely, SIMOP, which is a FORTRAN 77-based NLP simulation tool developed for optimization problems. Increasing the column dimension or switching the vapor−liquid equilibrium (VLE) description to a nonideal situation, which produces nonlinear models with a much larger number of equations that must be solved simultaneously, show that the results deteriorate. This is attributed to the lack of user control over the subsystems’ structures (viz, tearing variables). This problem was partially circumvented through the application of a more elaborate scheme initialization for the column variables. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801613e
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9611–9621[article] A coupled strategy for the solution of NLP and MINLP optimization problems : benefits and pitfalls [texte imprimé] / Helder G. Silva, Auteur ; Romualdo L. R. Salcedo, Auteur . - 2010 . - pp. 9611–9621.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9611–9621
Mots-clés : Nonlinear programming problems Mixed-integer nonlinear Stochastic optimizers Résumé : This paper presents a strategy for the solution of nonlinear programming (NLP) and mixed-integer nonlinear programming (MINLP) problems, based on the coupling of the equation-oriented simulator ASCEND IV with the stochastic optimizers MSGA and MSIMPSA. Both NLP and MINLP formulations of a reactive distillation example were explored. The results show that the connection between the two software blocks was successfully established. Despite the highly nonlinear behavior of the proposed example, the results presented generally agree with those previously obtained for the same case study using other approaches, namely, SIMOP, which is a FORTRAN 77-based NLP simulation tool developed for optimization problems. Increasing the column dimension or switching the vapor−liquid equilibrium (VLE) description to a nonideal situation, which produces nonlinear models with a much larger number of equations that must be solved simultaneously, show that the results deteriorate. This is attributed to the lack of user control over the subsystems’ structures (viz, tearing variables). This problem was partially circumvented through the application of a more elaborate scheme initialization for the column variables. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801613e Exemplaires
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Titre : Handling inequality constraints in optimal control by problem reformulation Type de document : texte imprimé Auteurs : Rein Luus, Auteur Année de publication : 2010 Article en page(s) : pp. 9622–9630 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Optimal control Nonisothermal fed-batch reactor Heat constraint Résumé : Establishment of optimal control for systems, where constraints involve both control and state, is very difficult. In some problems the difficulty is reduced significantly by transforming the optimal control problem. For illustration, the optimal control of a nonisothermal fed-batch reactor with heat removal constraint is considered. Although there are only two control variables, the feed rate and the temperature, the heat removal rate constraint makes the optimal control problem very difficult. To parametrize the optimal control problem, the time interval is divided into P time stages of variable length, and piecewise constant control is used at each time stage. Establishment of the optimal control policy is very challenging owing to the low sensitivity, the heat removal constraint, and the need for a large number of time stages for adequate approximation. However, by reformulating the optimal control problem where heat generation, rather than temperature, is used as a control variable, we are able to get greater accuracy with a smaller number of time stages. The optimal control policy is established with iterative dynamic programming and checked with LJ-optimization procedure. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801806t
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9622–9630[article] Handling inequality constraints in optimal control by problem reformulation [texte imprimé] / Rein Luus, Auteur . - 2010 . - pp. 9622–9630.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9622–9630
Mots-clés : Optimal control Nonisothermal fed-batch reactor Heat constraint Résumé : Establishment of optimal control for systems, where constraints involve both control and state, is very difficult. In some problems the difficulty is reduced significantly by transforming the optimal control problem. For illustration, the optimal control of a nonisothermal fed-batch reactor with heat removal constraint is considered. Although there are only two control variables, the feed rate and the temperature, the heat removal rate constraint makes the optimal control problem very difficult. To parametrize the optimal control problem, the time interval is divided into P time stages of variable length, and piecewise constant control is used at each time stage. Establishment of the optimal control policy is very challenging owing to the low sensitivity, the heat removal constraint, and the need for a large number of time stages for adequate approximation. However, by reformulating the optimal control problem where heat generation, rather than temperature, is used as a control variable, we are able to get greater accuracy with a smaller number of time stages. The optimal control policy is established with iterative dynamic programming and checked with LJ-optimization procedure. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801806t Exemplaires
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Titre : Development of correlations for overall gas hold-up, volumetric mass transfer coefficient, and effective interfacial area in bubble column reactors using hybrid genetic algorithm-support vector regression technique : viscous newtonian and non-newtonian liquids Type de document : texte imprimé Auteurs : Prashant P. Gupta, Auteur ; Shamel S. Merchant, Auteur ; Akshay U. Bhat, Auteur Année de publication : 2010 Article en page(s) : pp. 9631–9654 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Genetic algorithm-support vector regression Overall gas hold-up Volumetric mass-transfer coefficient Effective interfacial area Résumé : The objective of this study was to develop hybrid genetic algorithm−support vector regression (GA-SVR)-based correlations for overall gas hold-up (ϵG), volumetric mass-transfer coefficient (kLa), and effective interfacial area (a) in bubble column reactors for gas−liquid systems employing viscous Newtonian and non-Newtonian systems as the liquid phase. The hybrid GA-SVR is a novel technique based on the feature generation approach using genetic algorithm (GA). In the present study, GA has been used for nonlinear rescaling of attributes. These, exponentially scaled, are eventually subjected to SVR training. The technique is an extension of conventional SVR technique, showing relatively enhanced results. For this purpose an extensive literature search was done. From the published literature, 1629 data points for viscous Newtonian and 845 data points for viscous non-Newtonian systems for ϵG, 500 data points for viscous Newtonian and 556 data points for viscous non-Newtonian systems for kLa, and 208 data points for viscous non-Newtonian systems for a, respectively, were collected. These data sets were collected spanning the years 1965−2007. Correlations were developed after taking into account all the parameters affecting ϵG, kLa, and a such as column and sparger geometry, gas−liquid properties, operating temperature, pressure, and superficial gas and liquid velocities. The correlations thus developed gave prediction accuracies of 0.994 and 0.999 and average absolute relative errors (AARE) of 3.75 and 1.65% for viscous Newtonian and non-Newtonian systems for ϵG, prediction accuracies of 0.983 and 0.998 and AARE of 8.62 and 1.91% for viscous Newtonian and non-Newtonian systems for kLa, and prediction accuracy of 0.999 and AARE of 1% for viscous non-Newtonian systems for a, respectively. These correlations also showed much improved results when compared with all the existing correlations proposed in literature. To facilitate their usage, all the hybrid GA-SVR-based correlations have been uploaded on the web link http://www.esnips.com/web/UICT-NCL. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801834w
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9631–9654[article] Development of correlations for overall gas hold-up, volumetric mass transfer coefficient, and effective interfacial area in bubble column reactors using hybrid genetic algorithm-support vector regression technique : viscous newtonian and non-newtonian liquids [texte imprimé] / Prashant P. Gupta, Auteur ; Shamel S. Merchant, Auteur ; Akshay U. Bhat, Auteur . - 2010 . - pp. 9631–9654.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9631–9654
Mots-clés : Genetic algorithm-support vector regression Overall gas hold-up Volumetric mass-transfer coefficient Effective interfacial area Résumé : The objective of this study was to develop hybrid genetic algorithm−support vector regression (GA-SVR)-based correlations for overall gas hold-up (ϵG), volumetric mass-transfer coefficient (kLa), and effective interfacial area (a) in bubble column reactors for gas−liquid systems employing viscous Newtonian and non-Newtonian systems as the liquid phase. The hybrid GA-SVR is a novel technique based on the feature generation approach using genetic algorithm (GA). In the present study, GA has been used for nonlinear rescaling of attributes. These, exponentially scaled, are eventually subjected to SVR training. The technique is an extension of conventional SVR technique, showing relatively enhanced results. For this purpose an extensive literature search was done. From the published literature, 1629 data points for viscous Newtonian and 845 data points for viscous non-Newtonian systems for ϵG, 500 data points for viscous Newtonian and 556 data points for viscous non-Newtonian systems for kLa, and 208 data points for viscous non-Newtonian systems for a, respectively, were collected. These data sets were collected spanning the years 1965−2007. Correlations were developed after taking into account all the parameters affecting ϵG, kLa, and a such as column and sparger geometry, gas−liquid properties, operating temperature, pressure, and superficial gas and liquid velocities. The correlations thus developed gave prediction accuracies of 0.994 and 0.999 and average absolute relative errors (AARE) of 3.75 and 1.65% for viscous Newtonian and non-Newtonian systems for ϵG, prediction accuracies of 0.983 and 0.998 and AARE of 8.62 and 1.91% for viscous Newtonian and non-Newtonian systems for kLa, and prediction accuracy of 0.999 and AARE of 1% for viscous non-Newtonian systems for a, respectively. These correlations also showed much improved results when compared with all the existing correlations proposed in literature. To facilitate their usage, all the hybrid GA-SVR-based correlations have been uploaded on the web link http://www.esnips.com/web/UICT-NCL. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801834w Exemplaires
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Titre : Design and scheduling of periodic multipurpose batch plants under uncertainty Type de document : texte imprimé Auteurs : Tânia Pinto-Varela, Auteur ; Ana Paula F. D. Barbosa-Povoa, Auteur ; Augusto Q. Novais, Auteur Année de publication : 2010 Article en page(s) : pp. 9655–9670 Note générale : Chemistry engineering Langues : Anglais (eng) Mots-clés : Multipurpose batch plants Scheduling Résumé : This work deals with the design of multipurpose batch plants under uncertainty. The model proposed by Pinto et al. [Comput. Chem. Eng. 2005, 29 (6), 1293−1303] for the detailed design of batch plants is extended to address the problem of uncertainty associated with production demand. Equipment choices, as well as plant topology and associated schedule, are defined simultaneously under an uncertain demand environment. Uncertainty is treated through a two-stage stochastic model leading to a mixed-integer linear programming (MILP) formulation, where profit is maximized and the expected value of perfect information (EVPI) is determined; the latter is estimated as the difference between the values of profit obtained for the wait-and-see and the here-and-now models. A scenario is set up where demand is represented by a discrete probability function and a cyclic operation considered, together with mixed storage policies and sharing of resources. Some illustrative examples are solved to show the model applicability and the EVPI are determined and analyzed. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900137p
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9655–9670[article] Design and scheduling of periodic multipurpose batch plants under uncertainty [texte imprimé] / Tânia Pinto-Varela, Auteur ; Ana Paula F. D. Barbosa-Povoa, Auteur ; Augusto Q. Novais, Auteur . - 2010 . - pp. 9655–9670.
Chemistry engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9655–9670
Mots-clés : Multipurpose batch plants Scheduling Résumé : This work deals with the design of multipurpose batch plants under uncertainty. The model proposed by Pinto et al. [Comput. Chem. Eng. 2005, 29 (6), 1293−1303] for the detailed design of batch plants is extended to address the problem of uncertainty associated with production demand. Equipment choices, as well as plant topology and associated schedule, are defined simultaneously under an uncertain demand environment. Uncertainty is treated through a two-stage stochastic model leading to a mixed-integer linear programming (MILP) formulation, where profit is maximized and the expected value of perfect information (EVPI) is determined; the latter is estimated as the difference between the values of profit obtained for the wait-and-see and the here-and-now models. A scenario is set up where demand is represented by a discrete probability function and a cyclic operation considered, together with mixed storage policies and sharing of resources. Some illustrative examples are solved to show the model applicability and the EVPI are determined and analyzed. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900137p Exemplaires
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Titre : Biomimicking altruistic behavior of honey bees in multi-objective genetic algorithm Type de document : texte imprimé Auteurs : Manojkumar Ramteke, Auteur ; Santosh K. Gupta, Auteur Année de publication : 2010 Article en page(s) : pp. 9671–9685 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Honey bees Biomimicking altruistic behavior Genetic algorithm Résumé : The altruistic behavior of honey bees provides an interesting contrast to natural selection in evolutionary biology. This is biomimicked in the framework of a multiobjective optimization algorithm, namely, genetic algorithm, GA, by exploiting the concept of elitism (preserving good parents). The effects of altruism and natural selection on the total fitness of the colony are compared. This basic algorithm is used for studying the evolution process. It is then modified to enhance the convergence rates of optimization problems and to simulate the carcinogenesis of cells using multiple queens, unlike in honeycombs, mimicking other species of hymenopterans, e.g., ants, wasps, etc. This algorithm provides a new approach for studying three problems, bee evolution, optimization, and cancer, and is used to understand conflicts in animal behavior, increase the speed of convergence of optimization problems, and for an improved understanding of the causes of cancer. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9004817
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9671–9685[article] Biomimicking altruistic behavior of honey bees in multi-objective genetic algorithm [texte imprimé] / Manojkumar Ramteke, Auteur ; Santosh K. Gupta, Auteur . - 2010 . - pp. 9671–9685.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9671–9685
Mots-clés : Honey bees Biomimicking altruistic behavior Genetic algorithm Résumé : The altruistic behavior of honey bees provides an interesting contrast to natural selection in evolutionary biology. This is biomimicked in the framework of a multiobjective optimization algorithm, namely, genetic algorithm, GA, by exploiting the concept of elitism (preserving good parents). The effects of altruism and natural selection on the total fitness of the colony are compared. This basic algorithm is used for studying the evolution process. It is then modified to enhance the convergence rates of optimization problems and to simulate the carcinogenesis of cells using multiple queens, unlike in honeycombs, mimicking other species of hymenopterans, e.g., ants, wasps, etc. This algorithm provides a new approach for studying three problems, bee evolution, optimization, and cancer, and is used to understand conflicts in animal behavior, increase the speed of convergence of optimization problems, and for an improved understanding of the causes of cancer. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9004817 Exemplaires
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Titre : Biomimicking altruistic behavior of honey bees in multi-objective genetic algorithm Type de document : texte imprimé Auteurs : Manojkumar Ramteke, Auteur ; Santosh K. Gupta, Auteur Année de publication : 2010 Article en page(s) : pp. 9671–9685 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Honey bees Biomimicking altruistic behavior Genetic algorithm Résumé : The altruistic behavior of honey bees provides an interesting contrast to natural selection in evolutionary biology. This is biomimicked in the framework of a multiobjective optimization algorithm, namely, genetic algorithm, GA, by exploiting the concept of elitism (preserving good parents). The effects of altruism and natural selection on the total fitness of the colony are compared. This basic algorithm is used for studying the evolution process. It is then modified to enhance the convergence rates of optimization problems and to simulate the carcinogenesis of cells using multiple queens, unlike in honeycombs, mimicking other species of hymenopterans, e.g., ants, wasps, etc. This algorithm provides a new approach for studying three problems, bee evolution, optimization, and cancer, and is used to understand conflicts in animal behavior, increase the speed of convergence of optimization problems, and for an improved understanding of the causes of cancer. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9004817
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9671–9685[article] Biomimicking altruistic behavior of honey bees in multi-objective genetic algorithm [texte imprimé] / Manojkumar Ramteke, Auteur ; Santosh K. Gupta, Auteur . - 2010 . - pp. 9671–9685.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9671–9685
Mots-clés : Honey bees Biomimicking altruistic behavior Genetic algorithm Résumé : The altruistic behavior of honey bees provides an interesting contrast to natural selection in evolutionary biology. This is biomimicked in the framework of a multiobjective optimization algorithm, namely, genetic algorithm, GA, by exploiting the concept of elitism (preserving good parents). The effects of altruism and natural selection on the total fitness of the colony are compared. This basic algorithm is used for studying the evolution process. It is then modified to enhance the convergence rates of optimization problems and to simulate the carcinogenesis of cells using multiple queens, unlike in honeycombs, mimicking other species of hymenopterans, e.g., ants, wasps, etc. This algorithm provides a new approach for studying three problems, bee evolution, optimization, and cancer, and is used to understand conflicts in animal behavior, increase the speed of convergence of optimization problems, and for an improved understanding of the causes of cancer. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9004817 Exemplaires
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Titre : Optimal moment sets for multivariate direct quadrature method of moments Type de document : texte imprimé Auteurs : Rodney O. Fox, Auteur Année de publication : 2010 Article en page(s) : pp. 9686–9696 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Direct quadrature method of moments Population balance equations Résumé : The direct quadrature method of moments (DQMOM) can be employed to close population balance equations (PBEs) governing a wide class of multivariate number density functions (NDFs). Such equations occur over a vast range of scientific applications, including aerosol science, kinetic theory, multiphase flows, turbulence modeling, and control theory, to name just a few. As the name implies, DQMOM uses quadrature weights and abscissas to approximate the moments of the NDF, and the number of quadrature nodes determines the accuracy of the closure. For nondegenerate univariate cases (i.e., a sufficiently smooth NDF), the N weights and N abscissas are uniquely determined by the first 2N non-negative integer moments of the NDF. Moreover, an efficient product−difference algorithm exists to compute the weights and abscissas from the moments. In contrast, for a d-dimensional NDF, a total of (1 + d)N multivariate moments are required to determine the weights and abscissas, and poor choices for the moment set can lead to nonunique abscissas and even negative weights. In this work, it is demonstrated that optimal moment sets exist for multivariate DQMOM when N = nd quadrature nodes are employed to represent a d-dimensional NDF with n = 1−3 and d = 1−3. Moreover, this choice is independent of the source terms in the PBE governing the time evolution of the NDF. A multivariate Fokker−Planck equation is used to illustrate the numerical properties of the method for d = 3 with n = 2 and 3. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801316d
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9686–9696[article] Optimal moment sets for multivariate direct quadrature method of moments [texte imprimé] / Rodney O. Fox, Auteur . - 2010 . - pp. 9686–9696.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9686–9696
Mots-clés : Direct quadrature method of moments Population balance equations Résumé : The direct quadrature method of moments (DQMOM) can be employed to close population balance equations (PBEs) governing a wide class of multivariate number density functions (NDFs). Such equations occur over a vast range of scientific applications, including aerosol science, kinetic theory, multiphase flows, turbulence modeling, and control theory, to name just a few. As the name implies, DQMOM uses quadrature weights and abscissas to approximate the moments of the NDF, and the number of quadrature nodes determines the accuracy of the closure. For nondegenerate univariate cases (i.e., a sufficiently smooth NDF), the N weights and N abscissas are uniquely determined by the first 2N non-negative integer moments of the NDF. Moreover, an efficient product−difference algorithm exists to compute the weights and abscissas from the moments. In contrast, for a d-dimensional NDF, a total of (1 + d)N multivariate moments are required to determine the weights and abscissas, and poor choices for the moment set can lead to nonunique abscissas and even negative weights. In this work, it is demonstrated that optimal moment sets exist for multivariate DQMOM when N = nd quadrature nodes are employed to represent a d-dimensional NDF with n = 1−3 and d = 1−3. Moreover, this choice is independent of the source terms in the PBE governing the time evolution of the NDF. A multivariate Fokker−Planck equation is used to illustrate the numerical properties of the method for d = 3 with n = 2 and 3. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801316d Exemplaires
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Titre : Adsorptive removal of fluoride by micro-nanohierarchal web of activated carbon fibers Type de document : texte imprimé Auteurs : Amit Kumar Gupta, Auteur ; Dinesh Deva, Auteur ; Ashutosh Sharma, Auteur Année de publication : 2010 Article en page(s) : pp. 9697–9707 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Activated carbon fibers Aluminum impregnated hierarchal web Chemical vapor deposition Résumé : This study describes the development of aluminum impregnated hierarchal web of carbon fibers for the removal of dissolved fluoride in water. Micrometer-sized activated carbon fibers (ACF) were used as a substrate to grow carbon nanofibers (CNF) by chemical vapor deposition (CVD) using Ni as a catalyst. The hierarchal web of micro-nanocarbon fibers (ACF/CNF) thus prepared was impregnated with aluminum (in its metallic state) and then tested for the adsorption of fluoride ions over the concentration range of 1−50 ppm in water under both batch and flow conditions. The adsorbent web showed significant adsorption of fluoride ions. In addition, the total fluoride uptake was observed to be larger on aluminum impregnated ACF/CNF web than on its parent material, the ACF alone impregnated with Al. Various analytical techniques including the scanning electron microscopy (SEM), Raman spectroscopy, and the elemental analyzer were employed to characterize the Al-impregnated ACF/CNF. The SEM images showed a complex 3D network of nanofibers uniformly deposited with Al. This study is a step in developing a general platform suitable for producing potable water that also specifically addresses the problem of fluoride removal. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801688k
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9697–9707[article] Adsorptive removal of fluoride by micro-nanohierarchal web of activated carbon fibers [texte imprimé] / Amit Kumar Gupta, Auteur ; Dinesh Deva, Auteur ; Ashutosh Sharma, Auteur . - 2010 . - pp. 9697–9707.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9697–9707
Mots-clés : Activated carbon fibers Aluminum impregnated hierarchal web Chemical vapor deposition Résumé : This study describes the development of aluminum impregnated hierarchal web of carbon fibers for the removal of dissolved fluoride in water. Micrometer-sized activated carbon fibers (ACF) were used as a substrate to grow carbon nanofibers (CNF) by chemical vapor deposition (CVD) using Ni as a catalyst. The hierarchal web of micro-nanocarbon fibers (ACF/CNF) thus prepared was impregnated with aluminum (in its metallic state) and then tested for the adsorption of fluoride ions over the concentration range of 1−50 ppm in water under both batch and flow conditions. The adsorbent web showed significant adsorption of fluoride ions. In addition, the total fluoride uptake was observed to be larger on aluminum impregnated ACF/CNF web than on its parent material, the ACF alone impregnated with Al. Various analytical techniques including the scanning electron microscopy (SEM), Raman spectroscopy, and the elemental analyzer were employed to characterize the Al-impregnated ACF/CNF. The SEM images showed a complex 3D network of nanofibers uniformly deposited with Al. This study is a step in developing a general platform suitable for producing potable water that also specifically addresses the problem of fluoride removal. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801688k Exemplaires
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Titre : Quantitative structure−property relationship (QSPR) prediction of liquid viscosities of pure organic compounds employing random forest regression Type de document : texte imprimé Auteurs : Remya Rajappan, Auteur ; Prashant D. Shingade, Auteur ; Ramanathan Natarajan, Auteur Année de publication : 2010 Article en page(s) : pp. 9708–9712 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Pure organic liquids Quantitative structure− property relationship Robust Random Forest regression algorithm Résumé : A quantitative structure−property relationship (QSPR) approach was used to develop a predictive model for viscosities of pure organic liquids using a set of 403 compounds that belong to diverse classes of organic chemicals. A pool of 116 descriptors that encode topostructural, topochemical, electrotopological, geometrical, and quantum chemical properties of the organic compounds was used to develop QSPR models, based on the robust Random Forest (RF) regression algorithm. The performance of the algorithm, in terms of correlation coefficients and mean square errors, was determined to be good. The capability of the algorithm to build models and select the most-informative features simultaneously is very useful for several quantitative structure−activity/property relationship tasks. The eight most-dominant features selected by the RF regression algorithm primarily contained predictors that encode characteristics of atoms and groups that form hydrogen bonds, as well as factors involving molecular shape and size. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8018406
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9708–9712[article] Quantitative structure−property relationship (QSPR) prediction of liquid viscosities of pure organic compounds employing random forest regression [texte imprimé] / Remya Rajappan, Auteur ; Prashant D. Shingade, Auteur ; Ramanathan Natarajan, Auteur . - 2010 . - pp. 9708–9712.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9708–9712
Mots-clés : Pure organic liquids Quantitative structure− property relationship Robust Random Forest regression algorithm Résumé : A quantitative structure−property relationship (QSPR) approach was used to develop a predictive model for viscosities of pure organic liquids using a set of 403 compounds that belong to diverse classes of organic chemicals. A pool of 116 descriptors that encode topostructural, topochemical, electrotopological, geometrical, and quantum chemical properties of the organic compounds was used to develop QSPR models, based on the robust Random Forest (RF) regression algorithm. The performance of the algorithm, in terms of correlation coefficients and mean square errors, was determined to be good. The capability of the algorithm to build models and select the most-informative features simultaneously is very useful for several quantitative structure−activity/property relationship tasks. The eight most-dominant features selected by the RF regression algorithm primarily contained predictors that encode characteristics of atoms and groups that form hydrogen bonds, as well as factors involving molecular shape and size. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8018406 Exemplaires
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Titre : Solid suspension and liquid phase mixing in solid−liquid stirred tanks Type de document : texte imprimé Auteurs : Madhavi V. Sardeshpande, Auteur ; Aparna R. Sagi, Auteur ; Vinay A. Juvekar, Auteur Année de publication : 2010 Article en page(s) : pp. 9713–9722 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Stirred tanks Catalytic reactions Crystallization Résumé : Stirred tanks are widely used in chemical process industries for catalytic reactions, dissolution of solids, crystallization, and so on. In designing and optimizing such processes, suspension quality of slurry is an important parameter. Suspension quality depends upon complex interactions of impeller generated flow, turbulence, and solid loading. Most of the earlier work on solid suspension focuses on identifying critical impeller speed for just suspension of solids (Njs). In this study, apart from Njs, aspects like cloud height and liquid phase mixing in solid−liquid suspensions were also studied. A new way of characterizing solid−liquid suspensions and liquid phase mixing using nonintrusive wall pressure fluctuation measurements has been developed. Systematic experimental data on Njs, cloud height, power consumption, mixing time, and circulation time over a range of solid volume fraction and impeller speeds have been presented here. The results and discussion presented here will have useful implications for designing solid−liquid stirred tanks. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801858a
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9713–9722[article] Solid suspension and liquid phase mixing in solid−liquid stirred tanks [texte imprimé] / Madhavi V. Sardeshpande, Auteur ; Aparna R. Sagi, Auteur ; Vinay A. Juvekar, Auteur . - 2010 . - pp. 9713–9722.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9713–9722
Mots-clés : Stirred tanks Catalytic reactions Crystallization Résumé : Stirred tanks are widely used in chemical process industries for catalytic reactions, dissolution of solids, crystallization, and so on. In designing and optimizing such processes, suspension quality of slurry is an important parameter. Suspension quality depends upon complex interactions of impeller generated flow, turbulence, and solid loading. Most of the earlier work on solid suspension focuses on identifying critical impeller speed for just suspension of solids (Njs). In this study, apart from Njs, aspects like cloud height and liquid phase mixing in solid−liquid suspensions were also studied. A new way of characterizing solid−liquid suspensions and liquid phase mixing using nonintrusive wall pressure fluctuation measurements has been developed. Systematic experimental data on Njs, cloud height, power consumption, mixing time, and circulation time over a range of solid volume fraction and impeller speeds have been presented here. The results and discussion presented here will have useful implications for designing solid−liquid stirred tanks. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801858a Exemplaires
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Titre : Investigation of the relationships between molecular structure, molecular descriptors, and physical properties Type de document : texte imprimé Auteurs : Inga Paster, Auteur ; Shacham, Mordechai, Auteur ; Neima Brauner, Auteur Année de publication : 2010 Article en page(s) : pp. 9723–9734 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Molecular Structures descriptors Quantitative structure property relations Résumé : The use of databases containing thousands of molecular descriptors, including 3-D descriptors, for predicting physical properties is discussed. It is shown that the use of 3-D descriptors for property prediction via quantitative structure property relations (QSPR) limits considerably their applicability, as 3-D structure files must be obtained from the same reliable source for all predictive and target compounds. A modified targeted QSPR (TQSPR) algorithm is presented, which includes a new technique for selecting training sets belonging to the homologous series of the target compound (if such compounds are available in the database). The method is employed for predicting seven properties for five homologous series. It is shown that most properties can be predicted on experimental error level, using training sets of 10 compounds and a maximum of 2 (non 3-D) descriptors. The exclusion of the 3-D descriptors enhances considerably the applicability of the TQSPRs, and the use of a small number of descriptors reduces the probability of “chance correlations”. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801318y
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9723–9734[article] Investigation of the relationships between molecular structure, molecular descriptors, and physical properties [texte imprimé] / Inga Paster, Auteur ; Shacham, Mordechai, Auteur ; Neima Brauner, Auteur . - 2010 . - pp. 9723–9734.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9723–9734
Mots-clés : Molecular Structures descriptors Quantitative structure property relations Résumé : The use of databases containing thousands of molecular descriptors, including 3-D descriptors, for predicting physical properties is discussed. It is shown that the use of 3-D descriptors for property prediction via quantitative structure property relations (QSPR) limits considerably their applicability, as 3-D structure files must be obtained from the same reliable source for all predictive and target compounds. A modified targeted QSPR (TQSPR) algorithm is presented, which includes a new technique for selecting training sets belonging to the homologous series of the target compound (if such compounds are available in the database). The method is employed for predicting seven properties for five homologous series. It is shown that most properties can be predicted on experimental error level, using training sets of 10 compounds and a maximum of 2 (non 3-D) descriptors. The exclusion of the 3-D descriptors enhances considerably the applicability of the TQSPRs, and the use of a small number of descriptors reduces the probability of “chance correlations”. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801318y Exemplaires
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Titre : Mixed convection heat transfer from a cylinder in power-law fluids : effect of aiding buoyancy Type de document : texte imprimé Auteurs : Avadhani T. Srinivas, Auteur Année de publication : 2010 Article en page(s) : pp. 9735–9754 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Mixed convection heat transfer Incompressible power-law fluids Isothermally heated horizontal cylinder Résumé : Mixed convection heat transfer from an isothermally heated horizontal cylinder immersed in incompressible power-law fluids is considered here in the steady flow regime when both the imposed flow and the buoyancy induced motion are in the same direction, i.e., the so-called buoyancy aiding configuration. Within the framework of the Boussinesq approximation, the suitable forms of the momentum and thermal energy equations for the power-law fluid model have been solved numerically using the finite volume based FLUENT (version 6.3) solver for the following ranges of conditions: the buoyancy parameter (Richardson number, 0 ≤ Ri ≤ 2), power-law index (0.2 ≤ n ≤ 1.8), Reynolds number (1 ≤ Re ≤ 40), and Prandtl number (1 ≤ Pr ≤ 100). In particular, the effects of these dimensionless parameters on the detailed local and global kinematics of flow and heat transfer characteristics such as streamline, vorticity, and pressure profiles, individual and total drag coefficients, and local and average Nusselt numbers have been presented. The wake size shows trends which are qualitatively similar to that seen in the pure forced convection (Ri = 0) regime, though it decreases with increasing Richardson number (Ri) and/or Prandtl number (Pr). The pressure coefficient decreases with the increasing values of Reynolds number (Re) and Prandtl number (Pr) and with decreasing Richardson number (Ri). It is, however, seen to be relatively insensitive to the value of power-law index (n). Both drag coefficients and average Nusselt number are augmented with the increasing buoyancy effects, Reynolds (Re) and, Prandtl (Pr) numbers. An increase in the shear-thinning tendency of the fluid enhances the drag and heat transfer, whereas both of these are generally reduced in shear-thickening fluids. Similarly, the fluid behavior also modulates the role of Richardson number (Ri); namely, the pressure forces dominate over the viscous forces in shear-thinning fluids and vice versa in shear-thickening fluids. Therefore, the buoyancy effects are found to be stronger in shear-thinning fluids and/or at low Reynolds numbers than that in shear-thickening and/or at high Reynolds numbers. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801892m
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9735–9754[article] Mixed convection heat transfer from a cylinder in power-law fluids : effect of aiding buoyancy [texte imprimé] / Avadhani T. Srinivas, Auteur . - 2010 . - pp. 9735–9754.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9735–9754
Mots-clés : Mixed convection heat transfer Incompressible power-law fluids Isothermally heated horizontal cylinder Résumé : Mixed convection heat transfer from an isothermally heated horizontal cylinder immersed in incompressible power-law fluids is considered here in the steady flow regime when both the imposed flow and the buoyancy induced motion are in the same direction, i.e., the so-called buoyancy aiding configuration. Within the framework of the Boussinesq approximation, the suitable forms of the momentum and thermal energy equations for the power-law fluid model have been solved numerically using the finite volume based FLUENT (version 6.3) solver for the following ranges of conditions: the buoyancy parameter (Richardson number, 0 ≤ Ri ≤ 2), power-law index (0.2 ≤ n ≤ 1.8), Reynolds number (1 ≤ Re ≤ 40), and Prandtl number (1 ≤ Pr ≤ 100). In particular, the effects of these dimensionless parameters on the detailed local and global kinematics of flow and heat transfer characteristics such as streamline, vorticity, and pressure profiles, individual and total drag coefficients, and local and average Nusselt numbers have been presented. The wake size shows trends which are qualitatively similar to that seen in the pure forced convection (Ri = 0) regime, though it decreases with increasing Richardson number (Ri) and/or Prandtl number (Pr). The pressure coefficient decreases with the increasing values of Reynolds number (Re) and Prandtl number (Pr) and with decreasing Richardson number (Ri). It is, however, seen to be relatively insensitive to the value of power-law index (n). Both drag coefficients and average Nusselt number are augmented with the increasing buoyancy effects, Reynolds (Re) and, Prandtl (Pr) numbers. An increase in the shear-thinning tendency of the fluid enhances the drag and heat transfer, whereas both of these are generally reduced in shear-thickening fluids. Similarly, the fluid behavior also modulates the role of Richardson number (Ri); namely, the pressure forces dominate over the viscous forces in shear-thinning fluids and vice versa in shear-thickening fluids. Therefore, the buoyancy effects are found to be stronger in shear-thinning fluids and/or at low Reynolds numbers than that in shear-thickening and/or at high Reynolds numbers. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801892m Exemplaires
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Titre : Modeling of freezing phenomena induced by chemical reactions Type de document : texte imprimé Auteurs : K. S. Gandhi, Auteur Année de publication : 2010 Article en page(s) : pp. 9755–9762 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Freezing Reactive solute Résumé : Spatial variations in the concentration of a reactive solute in solution are often encountered in a catalyst particle, and this leads to variation in the freezing point of the solution. Depending on the operating temperature, this can result in freezing of the solvent on a portion of catalyst, rendering that part of the active area ineffective. Freezing can occur by formation of a sharp front or a mush that separates the solid and fluid phases. In this paper, we model the extent of reduction in the active area due to freezing. Assuming that the freezing point decreases linearly with solute concentration, conditions for freezing to occur have been derived. At steady state, the ineffective fraction of catalyst pellet is found to be the same irrespective of the mode of freezing. Progress of freezing is determined by both the heat of reaction and the latent heat of fusion. Unlike in freezing of alloys where the latter plays a dominant role, the exothermicity of the reaction has a significant effect on freezing in the presence of chemical reactions. A dimensionless group analogous to the Stefan number could be defined to capture the combined effect of both of these. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9003514
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9755–9762[article] Modeling of freezing phenomena induced by chemical reactions [texte imprimé] / K. S. Gandhi, Auteur . - 2010 . - pp. 9755–9762.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9755–9762
Mots-clés : Freezing Reactive solute Résumé : Spatial variations in the concentration of a reactive solute in solution are often encountered in a catalyst particle, and this leads to variation in the freezing point of the solution. Depending on the operating temperature, this can result in freezing of the solvent on a portion of catalyst, rendering that part of the active area ineffective. Freezing can occur by formation of a sharp front or a mush that separates the solid and fluid phases. In this paper, we model the extent of reduction in the active area due to freezing. Assuming that the freezing point decreases linearly with solute concentration, conditions for freezing to occur have been derived. At steady state, the ineffective fraction of catalyst pellet is found to be the same irrespective of the mode of freezing. Progress of freezing is determined by both the heat of reaction and the latent heat of fusion. Unlike in freezing of alloys where the latter plays a dominant role, the exothermicity of the reaction has a significant effect on freezing in the presence of chemical reactions. A dimensionless group analogous to the Stefan number could be defined to capture the combined effect of both of these. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9003514 Exemplaires
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Titre : Identification of Markov Matrices of Milling Models Type de document : texte imprimé Auteurs : Jayanta Chakraborty, Auteur ; Doraiswami Ramkrishna, Auteur Année de publication : 2010 Article en page(s) : pp. 9763–9771 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Grinding mill Markov chain models Résumé : Detailed modeling of a grinding mill can be achieved through Markov chain models without involving lengthy computations. However, estimation of the key parameters of the model, elements of the Markov transition matrix, using observable quantities is not trivial. This powerful modeling tool can find wide applicability in operation and control of industrial mills if this set of parameters can be estimated using suitably observed quantities. In this study we model a complex multiregion mill using Markov chain and propose a general technique for estimation of the Markov transition matrix for breakage problems. This technique estimates the transition matrix from observed evolution of particle size distributions in various regions of the mill, based on extracting spectral information of the transition matrix from the data. It has been shown in this study that a specific grouping of states can lead to lower triangular block structure of the Markov transition matrix for a breakage problem. Detailed analysis of such a block matrix reveals that simple semilogarithmic plots of a set of observed quantities can be used in order to extract the spectral information of the transition matrix which in turn can be used to reconstruct the Markov matrix. A numerical example has been presented to illustrate various ideas which demonstrate that the proposed technique can be used successfully to estimate the Markov transition matrix very accurately from observations. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900456j#tfn1
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9763–9771[article] Identification of Markov Matrices of Milling Models [texte imprimé] / Jayanta Chakraborty, Auteur ; Doraiswami Ramkrishna, Auteur . - 2010 . - pp. 9763–9771.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9763–9771
Mots-clés : Grinding mill Markov chain models Résumé : Detailed modeling of a grinding mill can be achieved through Markov chain models without involving lengthy computations. However, estimation of the key parameters of the model, elements of the Markov transition matrix, using observable quantities is not trivial. This powerful modeling tool can find wide applicability in operation and control of industrial mills if this set of parameters can be estimated using suitably observed quantities. In this study we model a complex multiregion mill using Markov chain and propose a general technique for estimation of the Markov transition matrix for breakage problems. This technique estimates the transition matrix from observed evolution of particle size distributions in various regions of the mill, based on extracting spectral information of the transition matrix from the data. It has been shown in this study that a specific grouping of states can lead to lower triangular block structure of the Markov transition matrix for a breakage problem. Detailed analysis of such a block matrix reveals that simple semilogarithmic plots of a set of observed quantities can be used in order to extract the spectral information of the transition matrix which in turn can be used to reconstruct the Markov matrix. A numerical example has been presented to illustrate various ideas which demonstrate that the proposed technique can be used successfully to estimate the Markov transition matrix very accurately from observations. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900456j#tfn1 Exemplaires
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