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Détail de l'auteur
Auteur Dan Luss
Documents disponibles écrits par cet auteur
Affiner la rechercheInfluence of product adsorption on the operation of a reserve-flow reactor / Garg, Rohit in Aiche journal, Vol. 48 N°2 (Fevrier 2002)
in Aiche journal > Vol. 48 N°2 (Fevrier 2002) . - 334-345 p.
Titre : Influence of product adsorption on the operation of a reserve-flow reactor Type de document : texte imprimé Auteurs : Garg, Rohit, Auteur ; Garayhi, Abdul, Auteur ; Dan Luss Article en page(s) : 334-345 p. Note générale : Génie Chimique Langues : Anglais (eng) Mots-clés : Adsorption Surface Catalyseur Produit Réaction exothermique Réacteur d'inversion Ecoulement Concentration Alimentation Diluée Gamme Conditions de fonctionnement Paramètre Index. décimale : 660 Résumé : The adsorption on the catalyst surface of the product of an exothermic reaction in a reverse-flow reactor (RFR) may lead to large variations in the temporal effluent product concentration. Using a dilute reactant feed, the adsorbed product effluent concentration is low following each flow reversal, but it eventually exceeds the feed reactant concentration. The product adsorption may decrease the range of operating conditions (parameter values) for which the RFR can attain an ignited state. A cooled RFR may attain, for certain parameter values, complex dynamic states such as quasi-periodic and chaotic states. An increase in the adsorption capacity of the catalyst decreases the range of parameter values for which complex dynamic states exist. The desired period-1 operation of the RFR is more robust in the presence of product adsorption. Product adsorption may lead to surprising dynamic features, such as the coexistence of up to three stable quasi-periodic states for the same operating conditions.
L'adsorption sur la surface de catalyseur du produit d'une réaction exothermique dans un réacteur d'inversion d'écoulement (RFR) peut mener à de grandes variations de la concentration effluente temporelle de produit. En utilisant une alimentation diluée de réactif, la concentration effluente adsorbée de produit est basse suivant chaque inversion d'écoulement, mais elle excède par la suite la concentration en réactif d'alimentation. L'adsorption de produit peut diminuer la gamme des conditions de fonctionnement (les valeurs de paramètre) pour lesquelles le RFR peut atteindre un état mis à feu. Un RFR refroidi peut atteindre, pour certaines valeurs de paramètre, les états dynamiques complexes tels que les états quasi-périodiques et chaotiques. Une augmentation de la capacité d'adsorption du catalyseur diminue la gamme des valeurs de paramètre pour lesquelles les états dynamiques complexes existent. L'opération désirée de la période 1 du RFR est plus robuste en présence de l'adsorption de produit. L'adsorption de produit peut mener à étonner les dispositifs dynamiques, tels que la coexistence de jusqu'à trois états périodiques quasi d'écurie pour les mêmes conditions de fonctionnement.
DEWEY : 660.627.3 ISSN : 0001-1541 RAMEAU : Réacteurs à inversion de flux Réacteur d'écoulement En ligne : www.aiche.org, www.sciencedirect.com [article] Influence of product adsorption on the operation of a reserve-flow reactor [texte imprimé] / Garg, Rohit, Auteur ; Garayhi, Abdul, Auteur ; Dan Luss . - 334-345 p.
Génie Chimique
Langues : Anglais (eng)
in Aiche journal > Vol. 48 N°2 (Fevrier 2002) . - 334-345 p.
Mots-clés : Adsorption Surface Catalyseur Produit Réaction exothermique Réacteur d'inversion Ecoulement Concentration Alimentation Diluée Gamme Conditions de fonctionnement Paramètre Index. décimale : 660 Résumé : The adsorption on the catalyst surface of the product of an exothermic reaction in a reverse-flow reactor (RFR) may lead to large variations in the temporal effluent product concentration. Using a dilute reactant feed, the adsorbed product effluent concentration is low following each flow reversal, but it eventually exceeds the feed reactant concentration. The product adsorption may decrease the range of operating conditions (parameter values) for which the RFR can attain an ignited state. A cooled RFR may attain, for certain parameter values, complex dynamic states such as quasi-periodic and chaotic states. An increase in the adsorption capacity of the catalyst decreases the range of parameter values for which complex dynamic states exist. The desired period-1 operation of the RFR is more robust in the presence of product adsorption. Product adsorption may lead to surprising dynamic features, such as the coexistence of up to three stable quasi-periodic states for the same operating conditions.
L'adsorption sur la surface de catalyseur du produit d'une réaction exothermique dans un réacteur d'inversion d'écoulement (RFR) peut mener à de grandes variations de la concentration effluente temporelle de produit. En utilisant une alimentation diluée de réactif, la concentration effluente adsorbée de produit est basse suivant chaque inversion d'écoulement, mais elle excède par la suite la concentration en réactif d'alimentation. L'adsorption de produit peut diminuer la gamme des conditions de fonctionnement (les valeurs de paramètre) pour lesquelles le RFR peut atteindre un état mis à feu. Un RFR refroidi peut atteindre, pour certaines valeurs de paramètre, les états dynamiques complexes tels que les états quasi-périodiques et chaotiques. Une augmentation de la capacité d'adsorption du catalyseur diminue la gamme des valeurs de paramètre pour lesquelles les états dynamiques complexes existent. L'opération désirée de la période 1 du RFR est plus robuste en présence de l'adsorption de produit. L'adsorption de produit peut mener à étonner les dispositifs dynamiques, tels que la coexistence de jusqu'à trois états périodiques quasi d'écurie pour les mêmes conditions de fonctionnement.
DEWEY : 660.627.3 ISSN : 0001-1541 RAMEAU : Réacteurs à inversion de flux Réacteur d'écoulement En ligne : www.aiche.org, www.sciencedirect.com
in Industrial & engineering chemistry research > Vol. 51 N° 35 (Septembre 2012) . - pp. 11355–11366
Titre : Inlet cone effect on diesel particulate filter regeneration upon a rapid shift to idle Type de document : texte imprimé Auteurs : Mengting Yu, Auteur ; Dan Luss, Auteur Année de publication : 2012 Article en page(s) : pp. 11355–11366 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Diesel engine Résumé : The particulate matter (PM) emitted by a diesel engine is collected and then burned in a diesel particulate filter (DPF). A major technological challenge in the operation of the ceramic, often cordierite, filter is that a rapid shift to idle may create a local hot region with a temperature much higher than under stationary feed conditions. This excessive transient temperature rise may cause local melting or cracking of the ceramic filter. Almost all previous studies of temperature excursions during the DPF regeneration (combustion of the deposited PM) were of cases in which equal exhaust flow rate was fed to all the parallel inlet channels. The diesel engine exhaust pipe is sometimes connected to the DPF by a wide-angled cone (diffuser). This leads to a mal-distribution of the flow rate to the inlet channels and of the deposited PM. Simulations revealed that following a rapid shift to idle the highest regeneration temperature in a DPF fed by a cone exceeded that in one not fed by a cone and it may exceed the cordierite DPF melting temperature (1200 °C). Moreover, it may generate transient radial and axial temperature gradients several times higher than under stationary regeneration that may crack the cordierite DPF. The increase in the temperature gradient is especially large in the axial direction. One of the surprising findings is that the highest temperature attained following a step change to idle is not a monotonic function of the initial PM loading. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie300948c [article] Inlet cone effect on diesel particulate filter regeneration upon a rapid shift to idle [texte imprimé] / Mengting Yu, Auteur ; Dan Luss, Auteur . - 2012 . - pp. 11355–11366.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 51 N° 35 (Septembre 2012) . - pp. 11355–11366
Mots-clés : Diesel engine Résumé : The particulate matter (PM) emitted by a diesel engine is collected and then burned in a diesel particulate filter (DPF). A major technological challenge in the operation of the ceramic, often cordierite, filter is that a rapid shift to idle may create a local hot region with a temperature much higher than under stationary feed conditions. This excessive transient temperature rise may cause local melting or cracking of the ceramic filter. Almost all previous studies of temperature excursions during the DPF regeneration (combustion of the deposited PM) were of cases in which equal exhaust flow rate was fed to all the parallel inlet channels. The diesel engine exhaust pipe is sometimes connected to the DPF by a wide-angled cone (diffuser). This leads to a mal-distribution of the flow rate to the inlet channels and of the deposited PM. Simulations revealed that following a rapid shift to idle the highest regeneration temperature in a DPF fed by a cone exceeded that in one not fed by a cone and it may exceed the cordierite DPF melting temperature (1200 °C). Moreover, it may generate transient radial and axial temperature gradients several times higher than under stationary regeneration that may crack the cordierite DPF. The increase in the temperature gradient is especially large in the axial direction. One of the surprising findings is that the highest temperature attained following a step change to idle is not a monotonic function of the initial PM loading. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie300948c
in Industrial & engineering chemistry research > Vol. 51 N° 9 (Mars 2012) . - pp. 3791-3800
Titre : Inlet cone effect on particulate matter deposition and regeneration temperature in a diesel particulate filter Type de document : texte imprimé Auteurs : Mengting Yu, Auteur ; Dan Luss, Auteur Année de publication : 2012 Article en page(s) : pp. 3791-3800 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Diesel particulate Résumé : A diesel particulate filter (DPF) is used to remove particulate matter (PM) from the effluent of a diesel engine. A major technological challenge in the operation of the ceramic cordierite filter is to prevent formation of local high temperatures that can melt the DPF or generate a thermal stress that may cause cracking. Most previous studies of the temperature rise during the DPF periodic regeneration (combustion of the deposited PM) considered cases in which the inlet velocity to all the parallel channels was uniform. A wide-angled cone (diffuser) is sometimes used to connect the diesel engine exhaust pipe to the DPF leading to a nonuniform velocity to the inlet channels, with the highest attained at the DPF center. We used a PM deposition and regeneration computational model to investigate the impact of the inlet cone on the DPF behavior under stationary feed conditions. The cone led to mal-distribution of the deposited PM, with the highest thickness in the DPF center. The highest regeneration temperature when using an inlet cone may be quite higher than when it is absent. Moreover, the inlet cone can generate higher temperature gradients and the resulting thermal stresses may crack the ceramic support. The largest radial thermal gradients are encountered dose to the wall in the downstream section of DPF, shortly after the temperature inside the filter reaches its peak. The cone leads to a slightly faster regeneration than when it is not used. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie202226r [article] Inlet cone effect on particulate matter deposition and regeneration temperature in a diesel particulate filter [texte imprimé] / Mengting Yu, Auteur ; Dan Luss, Auteur . - 2012 . - pp. 3791-3800.
Chimie industrielle
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 51 N° 9 (Mars 2012) . - pp. 3791-3800
Mots-clés : Diesel particulate Résumé : A diesel particulate filter (DPF) is used to remove particulate matter (PM) from the effluent of a diesel engine. A major technological challenge in the operation of the ceramic cordierite filter is to prevent formation of local high temperatures that can melt the DPF or generate a thermal stress that may cause cracking. Most previous studies of the temperature rise during the DPF periodic regeneration (combustion of the deposited PM) considered cases in which the inlet velocity to all the parallel channels was uniform. A wide-angled cone (diffuser) is sometimes used to connect the diesel engine exhaust pipe to the DPF leading to a nonuniform velocity to the inlet channels, with the highest attained at the DPF center. We used a PM deposition and regeneration computational model to investigate the impact of the inlet cone on the DPF behavior under stationary feed conditions. The cone led to mal-distribution of the deposited PM, with the highest thickness in the DPF center. The highest regeneration temperature when using an inlet cone may be quite higher than when it is absent. Moreover, the inlet cone can generate higher temperature gradients and the resulting thermal stresses may crack the ceramic support. The largest radial thermal gradients are encountered dose to the wall in the downstream section of DPF, shortly after the temperature inside the filter reaches its peak. The cone leads to a slightly faster regeneration than when it is not used. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie202226r
in Industrial & engineering chemistry research > Vol. 51 N° 19 (Mai 2012) . - pp. 6686–6696
Titre : Modeling studies on lean NOx reduction by a sequence of LNT – SCR bricks Type de document : texte imprimé Auteurs : Arun S. Kota, Auteur ; Dan Luss, Auteur ; Vemuri Balakotaiah, Auteur Année de publication : 2012 Article en page(s) : pp. 6686–6696 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : NOx Selective catalytic reduction Résumé : Several experimental studies have been conducted to determine the NOx reduction by a series of LNT (lean NOx trap) and SCR (selective catalytic reduction) catalytic bricks. An important goal is to minimize the required precious metal loading in the LNT while keeping the NOx emission below a specified level. We present a mathematical model of this system using hydrogen as the reductant. Simulations are used to determine the influence of the architecture of the LNT–SCR bricks, nonuniform precious metal loading in the LNT bricks, and the cycle time at temperatures in the range of 200–350 °C. The simulations lead to the following observations: (a) Low temperature reduction is the limiting step in the optimization of precious group metal (PGM) loading in LNT. (b) The NOx conversion increases as the number of the sequential bricks (with total length fixed) increase and reaches an asymptotic limit. From a practical point of view, there is little incentive in using more than two sequential pairs. (c) Nonuniform precious metal loading of the LNT bricks results in only a minor improvement in the deNOx performance. (d) The cycle time has a significant impact on the NOx conversion. In the simulated example, the NOx conversion at low temperatures is increased by about 15–20% by reducing the cycle time by a factor of 2. (e) Even at low temperature operation, diffusional limitations in the washcoat are most likely to be important in the LNT but not in the SCR operation. The NOx conversion and ammonia selectivity are reduced when washcoat diffusion is dominant in the LNT. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie300190c [article] Modeling studies on lean NOx reduction by a sequence of LNT – SCR bricks [texte imprimé] / Arun S. Kota, Auteur ; Dan Luss, Auteur ; Vemuri Balakotaiah, Auteur . - 2012 . - pp. 6686–6696.
Industrial chemistry
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 51 N° 19 (Mai 2012) . - pp. 6686–6696
Mots-clés : NOx Selective catalytic reduction Résumé : Several experimental studies have been conducted to determine the NOx reduction by a series of LNT (lean NOx trap) and SCR (selective catalytic reduction) catalytic bricks. An important goal is to minimize the required precious metal loading in the LNT while keeping the NOx emission below a specified level. We present a mathematical model of this system using hydrogen as the reductant. Simulations are used to determine the influence of the architecture of the LNT–SCR bricks, nonuniform precious metal loading in the LNT bricks, and the cycle time at temperatures in the range of 200–350 °C. The simulations lead to the following observations: (a) Low temperature reduction is the limiting step in the optimization of precious group metal (PGM) loading in LNT. (b) The NOx conversion increases as the number of the sequential bricks (with total length fixed) increase and reaches an asymptotic limit. From a practical point of view, there is little incentive in using more than two sequential pairs. (c) Nonuniform precious metal loading of the LNT bricks results in only a minor improvement in the deNOx performance. (d) The cycle time has a significant impact on the NOx conversion. In the simulated example, the NOx conversion at low temperatures is increased by about 15–20% by reducing the cycle time by a factor of 2. (e) Even at low temperature operation, diffusional limitations in the washcoat are most likely to be important in the LNT but not in the SCR operation. The NOx conversion and ammonia selectivity are reduced when washcoat diffusion is dominant in the LNT. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie300190c
in Industrial & engineering chemistry research > Vol. 47 N°20 (Octobre 2008) . - P. 7509-7523
Titre : Transversal hot zones formation in catalytic packed-bed reactors Type de document : texte imprimé Auteurs : Ganesh A. Viswanathan, Editeur scientifique ; Moshe Sheintuch, Editeur scientifique ; Dan Luss, Editeur scientifique Année de publication : 2008 Article en page(s) : P. 7509-7523 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Hot zones Catalytic reactors Packed-bed reactors (PBRs) Résumé : Spatiotemporal patterns reported to form in the cross sections of packed-bed reactors (PBRs) may pose severe safety hazard when present next to the reactor wall. Understanding what causes their formation and dynamic features is essential for the rational development of design and control strategies that circumvent their generation. We review the current knowledge and understanding about the formation of these transversal temperature patterns. Simulations and model analysis revealed that the formation of the hot spots and their dynamics are sensitive to the assumed kinetic and reactor models. Under practical conditions, stable symmetry-breaking bifurcation to nonuniform states, from stable, stationary, transversally uniform states cannot be predicted by common PBR models with a rate expression that depends only on the surface temperature and concentration of the limiting reactant. However, analysis and simulations reveal that transient nonuniform transversal temperatures may emerge in an upstream moving traveling front under practical conditions. Microkinetic oscillatory reactions predict the formation of a plethora of intricate spatiotemporal temperature patterns and temperature front motions that are sensitive to the reactor operating conditions and properties such as diameter and initial conditions. The predicted temperature patterns may be rather intricate as a result of conjugation of several modes. The nonlinear coupling between the states at different axial positions, that is, the interaction among the local temperature and concentrations at different cross-sections of the bed, may explain the intricate conjugation of several modes and modulation of the observed spatiotemporal patterns. While some simulations predicted spatiotemporal pattern evolution in PBRs, there is a need to understand which reaction mechanisms may lead to their formation. Most previous simulations and analysis utilized two-dimensional reactor models. However, hot zones are three-dimensional structures, often very small, and difficult to detect in large reactors. A 3-D simulation, although tedious, is necessary to provide full information about the size, shape and dynamic features of small hot zones. Moreover, common PBR models may have to be modified to account for the impact of local states such as flow distribution and nonuniform packing. Verification of the various model predictions requires in situ measurements of 3-D hot zones. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8005726 [article] Transversal hot zones formation in catalytic packed-bed reactors [texte imprimé] / Ganesh A. Viswanathan, Editeur scientifique ; Moshe Sheintuch, Editeur scientifique ; Dan Luss, Editeur scientifique . - 2008 . - P. 7509-7523.
Chemical engineering
Langues : Anglais (eng)
in Industrial & engineering chemistry research > Vol. 47 N°20 (Octobre 2008) . - P. 7509-7523
Mots-clés : Hot zones Catalytic reactors Packed-bed reactors (PBRs) Résumé : Spatiotemporal patterns reported to form in the cross sections of packed-bed reactors (PBRs) may pose severe safety hazard when present next to the reactor wall. Understanding what causes their formation and dynamic features is essential for the rational development of design and control strategies that circumvent their generation. We review the current knowledge and understanding about the formation of these transversal temperature patterns. Simulations and model analysis revealed that the formation of the hot spots and their dynamics are sensitive to the assumed kinetic and reactor models. Under practical conditions, stable symmetry-breaking bifurcation to nonuniform states, from stable, stationary, transversally uniform states cannot be predicted by common PBR models with a rate expression that depends only on the surface temperature and concentration of the limiting reactant. However, analysis and simulations reveal that transient nonuniform transversal temperatures may emerge in an upstream moving traveling front under practical conditions. Microkinetic oscillatory reactions predict the formation of a plethora of intricate spatiotemporal temperature patterns and temperature front motions that are sensitive to the reactor operating conditions and properties such as diameter and initial conditions. The predicted temperature patterns may be rather intricate as a result of conjugation of several modes. The nonlinear coupling between the states at different axial positions, that is, the interaction among the local temperature and concentrations at different cross-sections of the bed, may explain the intricate conjugation of several modes and modulation of the observed spatiotemporal patterns. While some simulations predicted spatiotemporal pattern evolution in PBRs, there is a need to understand which reaction mechanisms may lead to their formation. Most previous simulations and analysis utilized two-dimensional reactor models. However, hot zones are three-dimensional structures, often very small, and difficult to detect in large reactors. A 3-D simulation, although tedious, is necessary to provide full information about the size, shape and dynamic features of small hot zones. Moreover, common PBR models may have to be modified to account for the impact of local states such as flow distribution and nonuniform packing. Verification of the various model predictions requires in situ measurements of 3-D hot zones. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8005726
