Documents disponibles écrits par cet auteur

Effects of particle shape, density, and size on a distribution of phase holdups in a gas−liquid−solid circulating fluidized bed riser / S. A. Razzak in Industrial & engineering chemistry research, Vol. 49 N° 15 (Août 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 15 (Août 2010) . - pp 6998–7007 Titre : Effects of particle shape, density, and size on a distribution of phase holdups in a gas−liquid−solid circulating fluidized bed riser Type de document : texte imprimé Auteurs : S. A. Razzak, Auteur ; J-X. Zhu, Auteur ; S. Barghi, Auteur Année de publication : 2010 Article en page(s) : pp 6998–7007 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Fluidized  bed  Gas  liquid  solid. Résumé : Electrical resistance tomography and optical fiber probe were employed to study the effects of particle shape, size, and density on the distribution of phase holdups in the riser section (5.97 m tall) of a gas−liquid−solid circulating fluidized bed (GLSCFB) at four axial locations. Saline water was used as conductive liquid phase while air was the gas phase. Two different sizes of spherical shape glass beads and two different sizes of irregular shape lava rock particles were used as the solid nonconductive phase. Because of the tendency of gas bubbles to move in the central region of the riser, gas holdup was higher in this region and decreased gradually toward the wall region for all four types of particles. Consequently, liquid and solid holdups were lower in the central region compared to the wall region. Under the same auxiliary fluidization rate, larger particles had low solids circulation rate (low particle velocity) compared to smaller size particles due to less fluidization in the distribution region. Gas and solids holdups for the smaller particles were found higher compared to larger particles. Shape (sphericity) appeared to have minimum influence on the phase holdups. The decreasing hydrostatic pressure on rising gas bubbles resulted in gas bubble expansion leading to higher concentration of solid particles in wall regions at higher axial locations. The particle size and shape appeared to have a direct impact on gas bubble breakage and coalescence, and in turn also on phase holdup distributions at different heights along the riser. Solids holdup decreased with increasing liquid velocity at all axial locations for all types of particles. The nonuniformity of solids holdup in the central region decreased as the flow structure was developing along the riser. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901704d [article] Effects of particle shape, density, and size on a distribution of phase holdups in a gas−liquid−solid circulating fluidized bed riser [texte imprimé] / S. A. Razzak, Auteur ; J-X. Zhu, Auteur ; S. Barghi, Auteur . - 2010 . - pp 6998–7007. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 15 (Août 2010) . - pp 6998–7007 Mots-clés : Fluidized  bed  Gas  liquid  solid. Résumé : Electrical resistance tomography and optical fiber probe were employed to study the effects of particle shape, size, and density on the distribution of phase holdups in the riser section (5.97 m tall) of a gas−liquid−solid circulating fluidized bed (GLSCFB) at four axial locations. Saline water was used as conductive liquid phase while air was the gas phase. Two different sizes of spherical shape glass beads and two different sizes of irregular shape lava rock particles were used as the solid nonconductive phase. Because of the tendency of gas bubbles to move in the central region of the riser, gas holdup was higher in this region and decreased gradually toward the wall region for all four types of particles. Consequently, liquid and solid holdups were lower in the central region compared to the wall region. Under the same auxiliary fluidization rate, larger particles had low solids circulation rate (low particle velocity) compared to smaller size particles due to less fluidization in the distribution region. Gas and solids holdups for the smaller particles were found higher compared to larger particles. Shape (sphericity) appeared to have minimum influence on the phase holdups. The decreasing hydrostatic pressure on rising gas bubbles resulted in gas bubble expansion leading to higher concentration of solid particles in wall regions at higher axial locations. The particle size and shape appeared to have a direct impact on gas bubble breakage and coalescence, and in turn also on phase holdup distributions at different heights along the riser. Solids holdup decreased with increasing liquid velocity at all axial locations for all types of particles. The nonuniformity of solids holdup in the central region decreased as the flow structure was developing along the riser. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901704d

(Gas)-liquid-solid circulating fluidized bed reactors / Arnab Atta 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. 7876–7892 Titre : (Gas)-liquid-solid circulating fluidized bed reactors : characteristics and applications Type de document : texte imprimé Auteurs : Arnab Atta, Auteur ; S. A. Razzak, Auteur ; K. D. P. Nigam, Auteur Année de publication : 2009 Article en page(s) : pp. 7876–7892 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Circulating  fluidized  beds  Gas-solid  circulating  fluidized  beds  Gas-liquid-solid  circulating  fluidized  beds Résumé : Accepting considerable advantages of circulating fluidized beds (CFBs) over the conventional fluidized beds, there has been numerous studies on CFBs concentrating primarily on the development of gas−solid circulating fluidized beds (GSCFBs). However a substantial amount of research has also been devoted to other two types of CFBs, namely liquid−solid and gas−liquid−solid circulating fluidized beds (LS and GLSCFBs). In this effort, an attempt has been made to summarize and review the research and progresses made on the last two types of CFBs since the highlighting of their hydrodynamics and potential applications in various industries by Zhu et al. [Can. J. Chem. Eng. 2000, 78, 82−94]. The issues associated with its hydrodynamics, scale-up, and design have been discussed with a re-emphasis on its potential application for various cost-effective processes. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900163t [article] (Gas)-liquid-solid circulating fluidized bed reactors : characteristics and applications [texte imprimé] / Arnab Atta, Auteur ; S. A. Razzak, Auteur ; K. D. P. Nigam, Auteur . - 2009 . - pp. 7876–7892. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7876–7892 Mots-clés : Circulating  fluidized  beds  Gas-solid  circulating  fluidized  beds  Gas-liquid-solid  circulating  fluidized  beds Résumé : Accepting considerable advantages of circulating fluidized beds (CFBs) over the conventional fluidized beds, there has been numerous studies on CFBs concentrating primarily on the development of gas−solid circulating fluidized beds (GSCFBs). However a substantial amount of research has also been devoted to other two types of CFBs, namely liquid−solid and gas−liquid−solid circulating fluidized beds (LS and GLSCFBs). In this effort, an attempt has been made to summarize and review the research and progresses made on the last two types of CFBs since the highlighting of their hydrodynamics and potential applications in various industries by Zhu et al. [Can. J. Chem. Eng. 2000, 78, 82−94]. The issues associated with its hydrodynamics, scale-up, and design have been discussed with a re-emphasis on its potential application for various cost-effective processes. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900163t

Radial distributions of phase holdups and phase propagation velocities in a three-phase gas-liquid-solid fluidized bed (GLSCFB) riser / S. A. Razzak in Industrial & engineering chemistry research, Vol. 48 N°1 (Janvier 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N°1 (Janvier 2009) . - P. 281-289 Titre : Radial distributions of phase holdups and phase propagation velocities in a three-phase gas-liquid-solid fluidized bed (GLSCFB) riser Type de document : texte imprimé Auteurs : S. A. Razzak, Editeur scientifique ; J.-X. Zhu, Editeur scientifique ; S. Barghi, Editeur scientifique Année de publication : 2009 Article en page(s) : P. 281-289 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Radial  Distributions  Gas−Liquid−Solid  Fluidized  Bed Résumé : Electrical resistance tomography (ERT) and fiber optic were applied to investigate phase holdups and phase propagation velocities in a gas−liquid−solid circulating fluidized bed (GLSCFB). Since ERT is applicable only to conductive phase(s), e.g. the liquid phase in this study, a fiber optic probe was employed simultaneously to quantify all three phases. Saline water was used as the conductive and continuous phase. Glass beads and lava rocks constitute the solid phase and air as the gas phase. Glass beads were transparent and spherical in shape; however, lava rock particles were irregular in shape and opaque, which affected the signals obtained from the optical fiber probe. An empirical model was developed to measure the gas holdup using optical fiber probe data. Gas holdup was higher in the central region and decreased radially, while opposite trend was observed with solid holdup due to the drag forces imposed on solid particles by the gas and liquid flow in the riser. By applying cross-correlation between the data obtained at two different levels in the riser, nonconductive phase propagation velocity was obtained. The propagation velocity was higher in the central region compared to the wall region and increased with increasing liquid superficial velocity. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800299w [article] Radial distributions of phase holdups and phase propagation velocities in a three-phase gas-liquid-solid fluidized bed (GLSCFB) riser [texte imprimé] / S. A. Razzak, Editeur scientifique ; J.-X. Zhu, Editeur scientifique ; S. Barghi, Editeur scientifique . - 2009 . - P. 281-289. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N°1 (Janvier 2009) . - P. 281-289 Mots-clés : Radial  Distributions  Gas−Liquid−Solid  Fluidized  Bed Résumé : Electrical resistance tomography (ERT) and fiber optic were applied to investigate phase holdups and phase propagation velocities in a gas−liquid−solid circulating fluidized bed (GLSCFB). Since ERT is applicable only to conductive phase(s), e.g. the liquid phase in this study, a fiber optic probe was employed simultaneously to quantify all three phases. Saline water was used as the conductive and continuous phase. Glass beads and lava rocks constitute the solid phase and air as the gas phase. Glass beads were transparent and spherical in shape; however, lava rock particles were irregular in shape and opaque, which affected the signals obtained from the optical fiber probe. An empirical model was developed to measure the gas holdup using optical fiber probe data. Gas holdup was higher in the central region and decreased radially, while opposite trend was observed with solid holdup due to the drag forces imposed on solid particles by the gas and liquid flow in the riser. By applying cross-correlation between the data obtained at two different levels in the riser, nonconductive phase propagation velocity was obtained. The propagation velocity was higher in the central region compared to the wall region and increased with increasing liquid superficial velocity. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800299w