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Laser diagnostic investigation of the bubble eruption patterns in the freeboard of fluidized beds. 1. optimization of acetone planar laser induced fluorescence measurements / Georg Hartung in Industrial & engineering chemistry research, Vol. 47 n°15 (Août 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 n°15 (Août 2008) . - p. 5686–5697 Titre : Laser diagnostic investigation of the bubble eruption patterns in the freeboard of fluidized beds. 1. optimization of acetone planar laser induced fluorescence measurements Type de document : texte imprimé Auteurs : Georg Hartung, Auteur ; Christoph R. Müller, Auteur ; Johan Hult, Auteur ; John S. Dennis, Auteur Année de publication : 2008 Article en page(s) : p. 5686–5697 Note générale : Bibliogr. p. 5696-5697 Langues : Anglais (eng) Mots-clés : Freeboard  gas  --  mixing;  Acetone  PLIF;  Bubble  eruption  pattern Résumé : Here, the mixing of the freeboard gas with the gas of single bubbles and a continuous stream of bubbles is investigated using acetone planar laser induced fluorescence (PLIF), a technique only recently introduced to fluidized bed research [Solimene et al. Chem. Eng. Sci.2007, 62, 94]. Various improvements with respect to laser diagnostics are presented leading to optimal signals from acetone PLIF. The results obtained are compared with models presented in the literature. The observed bubble eruption pattern generally corresponds to the models proposed by Levy and Lockwood [ AIChE J.1983, 29, 889], Yórquez-Ramirez and Duursma [ Powder Technol.2001, 116, 76], and Solimene et al. [ Chem. Eng. Sci.2007, 62, 94]. No difference was observed between the eruption patterns of a single bubble compared to a continuous stream of bubbles. In contrast to the models of Yórquez-Ramirez and Duursma and Solimene et al., five different patterns of the release of gas at a dome formed by a rising bubble are observed. An explanation for the formation of a thin layer of acetone after the eruption of a bubbles is given. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0713543 [article] Laser diagnostic investigation of the bubble eruption patterns in the freeboard of fluidized beds. 1. optimization of acetone planar laser induced fluorescence measurements [texte imprimé] / Georg Hartung, Auteur ; Christoph R. Müller, Auteur ; Johan Hult, Auteur ; John S. Dennis, Auteur . - 2008 . - p. 5686–5697. Bibliogr. p. 5696-5697 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°15 (Août 2008) . - p. 5686–5697 Mots-clés : Freeboard  gas  --  mixing;  Acetone  PLIF;  Bubble  eruption  pattern Résumé : Here, the mixing of the freeboard gas with the gas of single bubbles and a continuous stream of bubbles is investigated using acetone planar laser induced fluorescence (PLIF), a technique only recently introduced to fluidized bed research [Solimene et al. Chem. Eng. Sci.2007, 62, 94]. Various improvements with respect to laser diagnostics are presented leading to optimal signals from acetone PLIF. The results obtained are compared with models presented in the literature. The observed bubble eruption pattern generally corresponds to the models proposed by Levy and Lockwood [ AIChE J.1983, 29, 889], Yórquez-Ramirez and Duursma [ Powder Technol.2001, 116, 76], and Solimene et al. [ Chem. Eng. Sci.2007, 62, 94]. No difference was observed between the eruption patterns of a single bubble compared to a continuous stream of bubbles. In contrast to the models of Yórquez-Ramirez and Duursma and Solimene et al., five different patterns of the release of gas at a dome formed by a rising bubble are observed. An explanation for the formation of a thin layer of acetone after the eruption of a bubbles is given. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0713543

Modeling reaction and diffusion in a spherical catalyst pellet using multicomponent flux models / Jin Yang Lim in Industrial & engineering chemistry research, Vol. 51 N° 49 (Décembre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 49 (Décembre 2012) . - pp. 15901–15911 Titre : Modeling reaction and diffusion in a spherical catalyst pellet using multicomponent flux models Type de document : texte imprimé Auteurs : Jin Yang Lim, Auteur ; John S. Dennis, Auteur Année de publication : 2013 Article en page(s) : pp. 15901–15911 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Catalyst  Multicomponent Résumé : This work presents the derivation and evaluation of a nonisothermal, steady-state model for a spherical pellet of catalyst, where the intraparticle diffusion is modeled by the Cylindrical Pore Interpolation Model (CPIM), a multicomponent flux model based on the Stefan-Maxwell equations, modified by a momentum balance. Since many reactions involve more than two chemical species and most industrial catalysts operate under diffusion-limited regimes, understanding intraparticle, multicomponent diffusion is crucial for the accurate modeling of reaction and diffusion within a catalyst pellet. The model was applied to the methanation reaction, where its industrial importance and high exothermicity makes it an ideal candidate as a concrete example. The profiles within the catalyst of composition, pressure, temperature, and rate of reaction were generated for various conditions. Several key dimensionless groups were identified in order to study the system over a large range of conditions and identify the important parameters. The predictions from the CPIM and the Dusty Gas Model (DGM) were compared. It was found that under most circumstances, only minor differences were observed between the predictions of the CPIM and the DGM. However, appreciable discrepancies were found when catalyst pellets, which had low thermal conductivities and contained pores of size such that values of both Knudsen and binary diffusivity were comparable, were reacted at low pressure. In summary, the work shows that the CPIM is well-suited to modeling multicomponent diffusion and reaction in pseudohomogenous catalyst pellets because (i) the assumptions used in the derivation are reasonable and explicit, (ii) an interpolation procedure allows diffusion to be modeled for the range from Knudsen diffusion through to continuum flow, and (iii) the equations can be presented in a compact form suitable for numerical solution. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie302528u [article] Modeling reaction and diffusion in a spherical catalyst pellet using multicomponent flux models [texte imprimé] / Jin Yang Lim, Auteur ; John S. Dennis, Auteur . - 2013 . - pp. 15901–15911. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 49 (Décembre 2012) . - pp. 15901–15911 Mots-clés : Catalyst  Multicomponent Résumé : This work presents the derivation and evaluation of a nonisothermal, steady-state model for a spherical pellet of catalyst, where the intraparticle diffusion is modeled by the Cylindrical Pore Interpolation Model (CPIM), a multicomponent flux model based on the Stefan-Maxwell equations, modified by a momentum balance. Since many reactions involve more than two chemical species and most industrial catalysts operate under diffusion-limited regimes, understanding intraparticle, multicomponent diffusion is crucial for the accurate modeling of reaction and diffusion within a catalyst pellet. The model was applied to the methanation reaction, where its industrial importance and high exothermicity makes it an ideal candidate as a concrete example. The profiles within the catalyst of composition, pressure, temperature, and rate of reaction were generated for various conditions. Several key dimensionless groups were identified in order to study the system over a large range of conditions and identify the important parameters. The predictions from the CPIM and the Dusty Gas Model (DGM) were compared. It was found that under most circumstances, only minor differences were observed between the predictions of the CPIM and the DGM. However, appreciable discrepancies were found when catalyst pellets, which had low thermal conductivities and contained pores of size such that values of both Knudsen and binary diffusivity were comparable, were reacted at low pressure. In summary, the work shows that the CPIM is well-suited to modeling multicomponent diffusion and reaction in pseudohomogenous catalyst pellets because (i) the assumptions used in the derivation are reasonable and explicit, (ii) an interpolation procedure allows diffusion to be modeled for the range from Knudsen diffusion through to continuum flow, and (iii) the equations can be presented in a compact form suitable for numerical solution. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie302528u

The Effect of addition of ZrO2 to Fe2O3 for hydrogen production by chemical looping / Wen Liu in Industrial & engineering chemistry research, Vol. 51 N° 51 (Décembre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 51 (Décembre 2012) . - pp. 16597–16609 Titre : The Effect of addition of ZrO2 to Fe2O3 for hydrogen production by chemical looping Type de document : texte imprimé Auteurs : Wen Liu, Auteur ; John S. Dennis, Auteur ; Stuart A. Scott, Auteur Année de publication : 2012 Article en page(s) : pp. 16597–16609 Note générale : Industrial chemistry Langues : Anglais (eng) Résumé : In this paper, a synthetic mixture of ZrO2 and Fe2O3 was prepared by coprecipitation for use in chemical looping and hydrogen production. Cycling experiments in a fluidized bed showed that a material composed of 30 mol % ZrO2 and 70 mol % Fe2O3 was capable of producing hydrogen with a consistent yield of 90 mol % of the stoichiometric amount over 20 cycles of reduction and oxidation at 1123 K. Here, the iron oxide was subjected to cycles consisting of nearly 100% reduction to Fe followed by reoxidation (with steam or CO2 and then air) to Fe2O3. There was no contamination by CO of the hydrogen produced, at a lower detection limit of 500 ppm, when the conversion of Fe3O4 to Fe was kept below 90 mol %. A preliminary investigation of the reaction kinetics confirmed that the ZrO2 support does not inhibit rates of reaction compared with those observed with iron oxide alone. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie302626x [article] The Effect of addition of ZrO2 to Fe2O3 for hydrogen production by chemical looping [texte imprimé] / Wen Liu, Auteur ; John S. Dennis, Auteur ; Stuart A. Scott, Auteur . - 2012 . - pp. 16597–16609. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 51 (Décembre 2012) . - pp. 16597–16609 Résumé : In this paper, a synthetic mixture of ZrO2 and Fe2O3 was prepared by coprecipitation for use in chemical looping and hydrogen production. Cycling experiments in a fluidized bed showed that a material composed of 30 mol % ZrO2 and 70 mol % Fe2O3 was capable of producing hydrogen with a consistent yield of 90 mol % of the stoichiometric amount over 20 cycles of reduction and oxidation at 1123 K. Here, the iron oxide was subjected to cycles consisting of nearly 100% reduction to Fe followed by reoxidation (with steam or CO2 and then air) to Fe2O3. There was no contamination by CO of the hydrogen produced, at a lower detection limit of 500 ppm, when the conversion of Fe3O4 to Fe was kept below 90 mol %. A preliminary investigation of the reaction kinetics confirmed that the ZrO2 support does not inhibit rates of reaction compared with those observed with iron oxide alone. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie302626x