Documents disponibles écrits par cet auteur

Direct quadrature method of moments for the mixing of inert polydisperse fluidized powders and the role of numerical diffusion / Luca Mazzei in Industrial & engineering chemistry research, Vol. 49 N° 11 (Juin 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp 5141–5152 Titre : Direct quadrature method of moments for the mixing of inert polydisperse fluidized powders and the role of numerical diffusion Type de document : texte imprimé Auteurs : Luca Mazzei, Auteur ; Daniele L. Marchisio, Auteur ; Paola Lettieri, Auteur Année de publication : 2010 Article en page(s) : pp 5141–5152 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Numerical  diffusion Résumé : Computational fluid dynamics (CFD) is extensively employed to investigate dense fluidized suspensions. Most mathematical models assume that the powder is monodisperse or is formed by few solid phases of particles with constant size. Real powders, nevertheless, are polydisperse, with their particle size distribution continuously changing in time and space. To account for this important feature, models have to include a population balance equation (PBE), which needs to be solved along with the customary fluid dynamic transport equations. The recently developed direct quadrature method of moments (DQMOM) permits solving PBEs in commercial CFD codes at relatively low computational cost. This technique, nevertheless, still needs testing in the context of dense multiphase flows. In this work we implement DQMOM within the CFD code Fluent to study the mixing of two polydisperse fluidized suspensions initially segregated. Each node of the quadrature represents a distinct solid phase advected with its own velocity. Simulating this apparently simple system highlights a problem related to the numerical solution of the DQMOM transport equations: these do not feature diffusive terms, but the numerical diffusion generated by the finite-volume integration method alters the model predictions, leading to wrong results. To solve this, the PBE needs to account for diffusion: this yields source terms in the transport equations of the quadrature weights and nodes that ensure the latter are correctly predicted. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901116y [article] Direct quadrature method of moments for the mixing of inert polydisperse fluidized powders and the role of numerical diffusion [texte imprimé] / Luca Mazzei, Auteur ; Daniele L. Marchisio, Auteur ; Paola Lettieri, Auteur . - 2010 . - pp 5141–5152. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp 5141–5152 Mots-clés : Numerical  diffusion Résumé : Computational fluid dynamics (CFD) is extensively employed to investigate dense fluidized suspensions. Most mathematical models assume that the powder is monodisperse or is formed by few solid phases of particles with constant size. Real powders, nevertheless, are polydisperse, with their particle size distribution continuously changing in time and space. To account for this important feature, models have to include a population balance equation (PBE), which needs to be solved along with the customary fluid dynamic transport equations. The recently developed direct quadrature method of moments (DQMOM) permits solving PBEs in commercial CFD codes at relatively low computational cost. This technique, nevertheless, still needs testing in the context of dense multiphase flows. In this work we implement DQMOM within the CFD code Fluent to study the mixing of two polydisperse fluidized suspensions initially segregated. Each node of the quadrature represents a distinct solid phase advected with its own velocity. Simulating this apparently simple system highlights a problem related to the numerical solution of the DQMOM transport equations: these do not feature diffusive terms, but the numerical diffusion generated by the finite-volume integration method alters the model predictions, leading to wrong results. To solve this, the PBE needs to account for diffusion: this yields source terms in the transport equations of the quadrature weights and nodes that ensure the latter are correctly predicted. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901116y

Effect of mixing and other operating parameters in sol-gel processes / Daniele L. Marchisio in Industrial & engineering chemistry research, Vol. 47 N°19 (Octobre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N°19 (Octobre 2008) . - p. 7202–7210 Titre : Effect of mixing and other operating parameters in sol-gel processes Type de document : texte imprimé Auteurs : Daniele L. Marchisio, Auteur ; Federica Omegna, Auteur ; Antonello A. Barresi, Auteur Année de publication : 2008 Article en page(s) : p. 7202–7210 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Sol-gel  process  Titanium  dioxide  synthesis  Thermal  treatments Résumé : In this work the effect of mixing on a sol−gel process is quantitatively investigated. Titanium dioxide synthesis from titanium tetra-isopropoxide is used as a test reaction. Solutions of titanium alkoxide in isopropyl alcohol and water in isopropyl alcohol are mixed in a special mixing device (i.e., vortex reactor) at different mixing rates, and the effect of mixing is quantified and compared with the effect of the other relevant operating parameters, namely the water to alkoxide, acid to alkoxide ratios, and alkoxide initial concentration. Dynamic light scattering, specific surface area measurement through nitrogen adsorption, X-ray diffraction, and field emission scanning electron microscopy are employed to determine particle size distribution, morphology, and crystallite size of the different particulate products (i.e., sols, gels, powders) obtained before and after thermal treatments under different synthesis conditions. A factorial design is used to plan the experimental campaign and results show that the role of mixing cannot be neglected. Moreover results show that mixing can be actively used to control the final product characteristics and must be taken into account when a process is transferred from the laboratory to the industrial scale. Eventually a scale-up criterion based on our previous work will be discussed. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800217b [article] Effect of mixing and other operating parameters in sol-gel processes [texte imprimé] / Daniele L. Marchisio, Auteur ; Federica Omegna, Auteur ; Antonello A. Barresi, Auteur . - 2008 . - p. 7202–7210. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N°19 (Octobre 2008) . - p. 7202–7210 Mots-clés : Sol-gel  process  Titanium  dioxide  synthesis  Thermal  treatments Résumé : In this work the effect of mixing on a sol−gel process is quantitatively investigated. Titanium dioxide synthesis from titanium tetra-isopropoxide is used as a test reaction. Solutions of titanium alkoxide in isopropyl alcohol and water in isopropyl alcohol are mixed in a special mixing device (i.e., vortex reactor) at different mixing rates, and the effect of mixing is quantified and compared with the effect of the other relevant operating parameters, namely the water to alkoxide, acid to alkoxide ratios, and alkoxide initial concentration. Dynamic light scattering, specific surface area measurement through nitrogen adsorption, X-ray diffraction, and field emission scanning electron microscopy are employed to determine particle size distribution, morphology, and crystallite size of the different particulate products (i.e., sols, gels, powders) obtained before and after thermal treatments under different synthesis conditions. A factorial design is used to plan the experimental campaign and results show that the role of mixing cannot be neglected. Moreover results show that mixing can be actively used to control the final product characteristics and must be taken into account when a process is transferred from the laboratory to the industrial scale. Eventually a scale-up criterion based on our previous work will be discussed. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800217b

Enzymatic hydrolysis of lignocellulosic biomasses via CFD and experiments / Danilo Carvajal in Industrial & engineering chemistry research, Vol. 51 N° 22 (Juin 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 22 (Juin 2012) . - pp. 7518–7525 Titre : Enzymatic hydrolysis of lignocellulosic biomasses via CFD and experiments Type de document : texte imprimé Auteurs : Danilo Carvajal, Auteur ; Daniele L. Marchisio, Auteur ; Samir Bensaid, Auteur Année de publication : 2012 Article en page(s) : pp. 7518–7525 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Enzymatic  Hydrolysis  Biomasses Résumé : The time evolution of the rheological properties of pretreated Arundo slurries has been estimated, during enzymatic hydrolysis for bioethanol production, by computational fluid dynamics simulations in conjunction with experimental tests on a laboratory scale anchor reactor with different solid concentrations (18.5 and 27.5% w/w) and stirring velocities (50–200 rpm). The simulations were carried out with Fluent 6.2 using the moving reference frame approach and the Herschel–Bulkley rheological model. Great care was taken in the development of the computational grid and in the solution of the numerical issues. The identification of the rheological parameters was successful and the results are consistent with other works published in the literature on similar systems. The next steps of this work will involve the use of these results to design new continuous reactors for enzymatic hydrolysis and their scale up to a pilot and industrial level. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201673t [article] Enzymatic hydrolysis of lignocellulosic biomasses via CFD and experiments [texte imprimé] / Danilo Carvajal, Auteur ; Daniele L. Marchisio, Auteur ; Samir Bensaid, Auteur . - 2012 . - pp. 7518–7525. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 22 (Juin 2012) . - pp. 7518–7525 Mots-clés : Enzymatic  Hydrolysis  Biomasses Résumé : The time evolution of the rheological properties of pretreated Arundo slurries has been estimated, during enzymatic hydrolysis for bioethanol production, by computational fluid dynamics simulations in conjunction with experimental tests on a laboratory scale anchor reactor with different solid concentrations (18.5 and 27.5% w/w) and stirring velocities (50–200 rpm). The simulations were carried out with Fluent 6.2 using the moving reference frame approach and the Herschel–Bulkley rheological model. Great care was taken in the development of the computational grid and in the solution of the numerical issues. The identification of the rheological parameters was successful and the results are consistent with other works published in the literature on similar systems. The next steps of this work will involve the use of these results to design new continuous reactors for enzymatic hydrolysis and their scale up to a pilot and industrial level. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201673t