Documents disponibles écrits par cet auteur

Experimental optimization of an autonomous scaled-down methane membrane reformer for hydrogen generation / David S. A. Simakov in Industrial & engineering chemistry research, Vol. 49 N° 3 (Fevrier 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 3 (Fevrier 2010) . - pp. 1123–1129 Titre : Experimental optimization of an autonomous scaled-down methane membrane reformer for hydrogen generation Type de document : texte imprimé Auteurs : David S. A. Simakov, Auteur ; Moshe Sheintuch, Auteur Année de publication : 2010 Article en page(s) : pp. 1123–1129 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Experimental--optimization  --  autonomous--scaled-down  methane--membrane  reformer--hydrogen  generation Résumé : Hydrogen generation by methane steam reforming in a thermally coupled membrane reformer−combustor has been experimentally studied. The concentric three-compartment reactor indirectly couples methane steam reforming with catalytic methane combustion and with a Pd−Ag membrane, to provide extrapure hydrogen. The reactor can be independently operated at steady state with the enthalpy required for the steam reforming and for heat losses provided by methane oxidation. The study focuses on the experimental demonstration of two approaches for the optimization of hydrogen generation in terms of power output and process efficiency: increasing the membrane separation ability and recycling reformer products to the combustion section. Note de contenu : Bibiogr. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900938n [article] Experimental optimization of an autonomous scaled-down methane membrane reformer for hydrogen generation [texte imprimé] / David S. A. Simakov, Auteur ; Moshe Sheintuch, Auteur . - 2010 . - pp. 1123–1129. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 3 (Fevrier 2010) . - pp. 1123–1129 Mots-clés : Experimental--optimization  --  autonomous--scaled-down  methane--membrane  reformer--hydrogen  generation Résumé : Hydrogen generation by methane steam reforming in a thermally coupled membrane reformer−combustor has been experimentally studied. The concentric three-compartment reactor indirectly couples methane steam reforming with catalytic methane combustion and with a Pd−Ag membrane, to provide extrapure hydrogen. The reactor can be independently operated at steady state with the enthalpy required for the steam reforming and for heat losses provided by methane oxidation. The study focuses on the experimental demonstration of two approaches for the optimization of hydrogen generation in terms of power output and process efficiency: increasing the membrane separation ability and recycling reformer products to the combustion section. Note de contenu : Bibiogr. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900938n

Loop reactor design and control for reversible exothermic reactions / Roman Sheinman in Industrial & engineering chemistry research, Vol. 48 N° 11 (Juin 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 11 (Juin 2009) . - pp. 5185–5192 Titre : Loop reactor design and control for reversible exothermic reactions Type de document : texte imprimé Auteurs : Roman Sheinman, Auteur ; Moshe Sheintuch, Auteur Année de publication : 2009 Article en page(s) : pp. 5185–5192 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Loop  reactor  Exothermic  reaction  Methanol  VOC  combustion Résumé : The loop reactor, in the form composed of several units, with feed and exit ports switching, is investigated for a reversible exothermic reaction like the synthesis of methanol. Unlike applications of VOC combustion, which have been extensively investigated and experimentally tested, the maximal temperature here is limited by equilibrium conditions and the advantage gained is due to the effectively periodic boundary conditions that describe the system: due to the rotating nature of the system, the stream undergoes cooling as it leaves the system, which in turn yields increasing conversions at an extent that depends on the parameters. We show that the system exhibits the slow-switching asymptote and the complex many-domains pattern that was identified for the irreversible case. The dynamic features within these domains are analyzed. Conversions are comparable to those in the commercially applied reactor with interstage cooling. Control procedures are suggested and tested. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801333w [article] Loop reactor design and control for reversible exothermic reactions [texte imprimé] / Roman Sheinman, Auteur ; Moshe Sheintuch, Auteur . - 2009 . - pp. 5185–5192. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 11 (Juin 2009) . - pp. 5185–5192 Mots-clés : Loop  reactor  Exothermic  reaction  Methanol  VOC  combustion Résumé : The loop reactor, in the form composed of several units, with feed and exit ports switching, is investigated for a reversible exothermic reaction like the synthesis of methanol. Unlike applications of VOC combustion, which have been extensively investigated and experimentally tested, the maximal temperature here is limited by equilibrium conditions and the advantage gained is due to the effectively periodic boundary conditions that describe the system: due to the rotating nature of the system, the stream undergoes cooling as it leaves the system, which in turn yields increasing conversions at an extent that depends on the parameters. We show that the system exhibits the slow-switching asymptote and the complex many-domains pattern that was identified for the irreversible case. The dynamic features within these domains are analyzed. Conversions are comparable to those in the commercially applied reactor with interstage cooling. Control procedures are suggested and tested. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801333w

Prediction of 3D transversal patterns in packed - bed reactors using a reduced 2D model / Olga Nekhamkina in Industrial & engineering chemistry research, Vol. 49 N° 21 (Novembre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 10558-10564 Titre : Prediction of 3D transversal patterns in packed - bed reactors using a reduced 2D model : Oscillatory kinetics Type de document : texte imprimé Auteurs : Olga Nekhamkina, Auteur ; Moshe Sheintuch, Auteur Année de publication : 2011 Article en page(s) : pp. 10558-10564 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Kinetics  Two  dimensional  model  Fixed  bed  reactor  Prediction Résumé : We have recently showed the formation of transversal patterns in a 3D cylindrical reactor in which an exothermic first-order reaction of Arrhenius kinetics occurs with variable catalytic activity. Under these oscillatory kinetics, the system exhibits a planar front (1D) solution, with the front position oscillating in the axial direction, while in the 3D case, three types of transversal patterns can emerge: rotating fronts, oscillating fronts with superimposed transversal (nonrotating) oscillations, and mixed rotating-oscillating fronts. In the present study, we analyze the possible reduction of the 3D model to a 2D cylindrical shell model to predict patterns. We map bifurcation diagrams showing domains of different modes using the reactor radius (R) as a bifurcation parameter and show that the front divergence and the domains of the kn-mode pattern in the 3D model [corresponding to the transversal eigenfunction Jk(μknr) exp(ikθ), in which Jk is the Bessel function of the first kind] can be predicted by those of the one wave in the 2D model using the linear transformation R3D = μknR2D. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23447948 [article] Prediction of 3D transversal patterns in packed - bed reactors using a reduced 2D model : Oscillatory kinetics [texte imprimé] / Olga Nekhamkina, Auteur ; Moshe Sheintuch, Auteur . - 2011 . - pp. 10558-10564. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 10558-10564 Mots-clés : Kinetics  Two  dimensional  model  Fixed  bed  reactor  Prediction Résumé : We have recently showed the formation of transversal patterns in a 3D cylindrical reactor in which an exothermic first-order reaction of Arrhenius kinetics occurs with variable catalytic activity. Under these oscillatory kinetics, the system exhibits a planar front (1D) solution, with the front position oscillating in the axial direction, while in the 3D case, three types of transversal patterns can emerge: rotating fronts, oscillating fronts with superimposed transversal (nonrotating) oscillations, and mixed rotating-oscillating fronts. In the present study, we analyze the possible reduction of the 3D model to a 2D cylindrical shell model to predict patterns. We map bifurcation diagrams showing domains of different modes using the reactor radius (R) as a bifurcation parameter and show that the front divergence and the domains of the kn-mode pattern in the 3D model [corresponding to the transversal eigenfunction Jk(μknr) exp(ikθ), in which Jk is the Bessel function of the first kind] can be predicted by those of the one wave in the 2D model using the linear transformation R3D = μknR2D. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23447948

Transversal hot zones formation in catalytic packed-bed reactors / Ganesh A. Viswanathan in Industrial & engineering chemistry research, Vol. 47 N°20 (Octobre 2008) 

Public ISBD [article]  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