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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

Impact of internals on the gas holdup and bubble properties of a bubble column / Ahmed A. Youssef in Industrial & engineering chemistry research, Vol. 48 N° 17 (Septembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8007–8013 Titre : Impact of internals on the gas holdup and bubble properties of a bubble column Type de document : texte imprimé Auteurs : Ahmed A. Youssef, Auteur ; Muthanna H. Al-Dahhan, Auteur Année de publication : 2009 Article en page(s) : pp. 8007–8013 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Internals  Methanol  synthesis  Fischer-Tropsch  process  Gas  holdup  Bubble  column Résumé : Most industrial applications involving bubble columns require the addition of internals for heat exchanging. However, most academic research on bubble columns has been performed in hollow (empty) ones. Hence, the impact of internals on the hydrodynamics of a bubble column has been insufficiently studied in the open literature. Accordingly, this study focuses on investigating the effect of internals that mimic those used in methanol synthesis (5% covered cross-sectional area) and the Fischer−Tropsch (FT) process (22% covered cross-sectional area) on the local gas holdup, gas−liquid interfacial area, bubble chord length, and bubble velocity distributions. The investigations have been performed using a four point optical probe in an 8 in. diameter column. An air−water system was used with superficial gas velocities up to 20 cm/s. An increase in gas holdup and interfacial area was obtained upon insertion of the internals, although the impact of the less dense internals (5% covered area) was not significant. However, in the case of dense internals, the bubble chord length decreased, yielding a decrease in the bubble velocity. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900266q [article] Impact of internals on the gas holdup and bubble properties of a bubble column [texte imprimé] / Ahmed A. Youssef, Auteur ; Muthanna H. Al-Dahhan, Auteur . - 2009 . - pp. 8007–8013. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8007–8013 Mots-clés : Internals  Methanol  synthesis  Fischer-Tropsch  process  Gas  holdup  Bubble  column Résumé : Most industrial applications involving bubble columns require the addition of internals for heat exchanging. However, most academic research on bubble columns has been performed in hollow (empty) ones. Hence, the impact of internals on the hydrodynamics of a bubble column has been insufficiently studied in the open literature. Accordingly, this study focuses on investigating the effect of internals that mimic those used in methanol synthesis (5% covered cross-sectional area) and the Fischer−Tropsch (FT) process (22% covered cross-sectional area) on the local gas holdup, gas−liquid interfacial area, bubble chord length, and bubble velocity distributions. The investigations have been performed using a four point optical probe in an 8 in. diameter column. An air−water system was used with superficial gas velocities up to 20 cm/s. An increase in gas holdup and interfacial area was obtained upon insertion of the internals, although the impact of the less dense internals (5% covered area) was not significant. However, in the case of dense internals, the bubble chord length decreased, yielding a decrease in the bubble velocity. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900266q