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Effect of operating pressure on the extent of hysteresis in a trickle bed reactor / Zeljko Kuzeljevic 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. 7593-7599 Titre : Effect of operating pressure on the extent of hysteresis in a trickle bed reactor Type de document : texte imprimé Auteurs : Zeljko Kuzeljevic, Editeur scientifique ; Werner van der Merwe, Editeur scientifique ; Muthanna H. Al-Dahhan, Editeur scientifique Année de publication : 2008 Article en page(s) : P. 7593-7599 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Operating  pressure  Hydrodynamic  parameters Résumé : The dependence of hydrodynamic parameters, such as pressure drop, on the flow history of the bed is called hysteresis. This phenomenon is most commonly associated with changes of flow distribution and flow patterns with the flow history. Many studies have shown that increased operating pressure will affect flow distribution and wetting efficiency; however, there seems to be no study of the effect of the elevated operating pressure on the extent of hysteresis. In this study, an experimental investigation of the hysteresis in a high-pressure trickle bed has been performed. A hysteresis factor has been introduced to quantify the extent of hysteresis and was found to be a strong function of gas and liquid operating flow rates as well as the operating pressure. In the region of lower liquid velocities, hysteresis is present regardless of the operating pressure or gas velocity. In the region of higher liquid velocities, increases in both pressure and gas velocity will lower the extent of hysteresis. For the range of conditions considered in this study, the extent of hysteresis was uniquely determined by the pressure drop in the Levec mode, regardless of the operating pressure or velocities. The results are interpreted in terms of the phenomenological analysis of Al-Dahhan and Dudukovic (Al-Dahhan, M. H.; Dudukovic, M. P. Chem. Eng. Sci. 1994, 49, 5681−98), which relates operating pressure and gas velocity to the flow distribution and wetting efficiency in a trickle bed reactor. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800255p [article] Effect of operating pressure on the extent of hysteresis in a trickle bed reactor [texte imprimé] / Zeljko Kuzeljevic, Editeur scientifique ; Werner van der Merwe, Editeur scientifique ; Muthanna H. Al-Dahhan, Editeur scientifique . - 2008 . - P. 7593-7599. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N°20 (Octobre 2008) . - P. 7593-7599 Mots-clés : Operating  pressure  Hydrodynamic  parameters Résumé : The dependence of hydrodynamic parameters, such as pressure drop, on the flow history of the bed is called hysteresis. This phenomenon is most commonly associated with changes of flow distribution and flow patterns with the flow history. Many studies have shown that increased operating pressure will affect flow distribution and wetting efficiency; however, there seems to be no study of the effect of the elevated operating pressure on the extent of hysteresis. In this study, an experimental investigation of the hysteresis in a high-pressure trickle bed has been performed. A hysteresis factor has been introduced to quantify the extent of hysteresis and was found to be a strong function of gas and liquid operating flow rates as well as the operating pressure. In the region of lower liquid velocities, hysteresis is present regardless of the operating pressure or gas velocity. In the region of higher liquid velocities, increases in both pressure and gas velocity will lower the extent of hysteresis. For the range of conditions considered in this study, the extent of hysteresis was uniquely determined by the pressure drop in the Levec mode, regardless of the operating pressure or velocities. The results are interpreted in terms of the phenomenological analysis of Al-Dahhan and Dudukovic (Al-Dahhan, M. H.; Dudukovic, M. P. Chem. Eng. Sci. 1994, 49, 5681−98), which relates operating pressure and gas velocity to the flow distribution and wetting efficiency in a trickle bed reactor. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800255p

Hydrodynamic effects in scaled-down hydrocracking of iron-based fischer-tropsch wax / Werner van der Merwe ; Dylan Loudon ; Dieter Leckel in Industrial & engineering chemistry research, Vol. 47 n°24 (Décembre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 n°24 (Décembre 2008) . - p. 10086–10092 Titre : Hydrodynamic effects in scaled-down hydrocracking of iron-based fischer-tropsch wax Type de document : texte imprimé Auteurs : Werner van der Merwe, Auteur ; Dylan Loudon, Auteur ; Dieter Leckel, Auteur Année de publication : 2009 Article en page(s) : p. 10086–10092 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Hydrodynamic--Effects  Iron  Wax Résumé : Iron-based low-temperature Fischer−Tropsch (LTFT) wax was hydrocracked in upflow and downflow mode of operation using fixed-bed bench-scale and pilot-scale reactors. Heavy paraffin conversion was higher in the upflow mode whereby lower diesel selectivities were observed. It was also shown that the diesel properties are a function of the mode of operation. The results indicate the presence of macrokinetic (hydrodynamic) limitations on the overall hydrocracking rate that is present due to the comparatively low liquid superficial velocity. The higher hydrocracking efficiency in the upflow mode is likely due to complete particle wetting (compared to the partial wetting in the downflow mode) that enhances both external and internal mass transfer of the liquid phase reagent. The results highlight the danger of scaled-down reactors that might not be representative of industrial operation. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800894w [article] Hydrodynamic effects in scaled-down hydrocracking of iron-based fischer-tropsch wax [texte imprimé] / Werner van der Merwe, Auteur ; Dylan Loudon, Auteur ; Dieter Leckel, Auteur . - 2009 . - p. 10086–10092. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°24 (Décembre 2008) . - p. 10086–10092 Mots-clés : Hydrodynamic--Effects  Iron  Wax Résumé : Iron-based low-temperature Fischer−Tropsch (LTFT) wax was hydrocracked in upflow and downflow mode of operation using fixed-bed bench-scale and pilot-scale reactors. Heavy paraffin conversion was higher in the upflow mode whereby lower diesel selectivities were observed. It was also shown that the diesel properties are a function of the mode of operation. The results indicate the presence of macrokinetic (hydrodynamic) limitations on the overall hydrocracking rate that is present due to the comparatively low liquid superficial velocity. The higher hydrocracking efficiency in the upflow mode is likely due to complete particle wetting (compared to the partial wetting in the downflow mode) that enhances both external and internal mass transfer of the liquid phase reagent. The results highlight the danger of scaled-down reactors that might not be representative of industrial operation. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800894w