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chemical engineering research and design 8 6 ( 2 0 0 8 ) 1369–1381

Contents lists available at ScienceDirect

Chemical Engineering Research and Design
journal homepage: www.elsevier.com/locate/cherd

Deagglomeration processes in high-shear devices
Jerzy Bałdyga a,∗ , Łukasz Makowski a , Wojciech Orciuch a , Caroline Sauter b , Heike P. Schuchmann b
a b

´ Faculty of Chemical andProcess Engineering, Warsaw University of Technology, ul. Warynskiego 1, 00-645 Warsaw, Poland Institute of Food Process Engineering, University of Karlsruhe (TH), Germany

a b s t r a c t
Methods of modeling, results of simulations and comparisons of model predictions with experimental data are presented for formulation of nano-suspensions by breaking up micron size nano-particle clusters inhigh-shear devices. An in-line rotor–stator, a high-pressure nozzle disintegrator and an ultrasonic device are considered; in particular, performance of the ultrasonic device is compared with results obtained previously for an in-line rotor–stator [J. Bałdyga, W. Orciuch, Ł. Makowski, K. Malik, G. Ozcan-Taskin, W. Eagels, and G. Padron, 2008. Dispersion of nanoparticle clusters in a rotor–stator mixer.Ind. Eng. Chem. Res. 47, 3652–3663] and the high-pressure nozzle [J. Bałdyga, W. Orciuch, Ł. Makowski, M. Malski-Brodzicki, and K. Malik, 2007. Break up of nano-particle cluster in high-shear devices. Chem. Eng. Process. 46 (9), 851–861]. A recently developed breakage model has been applied in our previous work [J. Bałdyga, W. Orciuch, Ł. Makowski, K. Malik, G. Ozcan-Taskin, W. Eagels, and G.Padron, 2008. Dispersion of nanoparticle clusters in a rotor–stator mixer. Ind. Eng. Chem. Res. 47, 3652–3663] to interpret erosive dispersion of agglomerates in the rotor–stator mixer. This paper deals with devices that generate much higher hydrodynamic stresses than that generated in the rotor–stator mixer. To interpret such high shear processes a model of breakage based on rapture mechanism isapplied together with the population balance to account for effects of breakage on agglomerate size distribution. High stresses are generated in part by cavitation and this effect is included in modeling. Effects of suspension structure on suspension rheology and resulting flow pattern are included in modeling by coupling constitutive rheological equations with population balances and CFD. Thepopulation balance equations are solved using QMOM that is linked directly to the k– model of the CFD code FLUENT. Results of deagglomeration in the ultrasonic device are compared with experimental data. © 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Keywords: Agglomerates; High-pressure nozzle disintegrator; Ultrasonic device; Rotor–stator mixer

1.Introduction

Suspensions consisting of nanoparticles and nanoparticle clusters have large potential for nanomaterials to be formulated into numerous products including scratch/abrasionresistant transparent coatings, nano-fluids (magnetic and highly conductive), polishing slurries and environmental catalysts. Shear flows of such suspensions occur in many technical applications. To obtain suspensionof controlled rheology and consisting of particles of controlled size, very often large agglomerates need to be broken in high shear flows and stabilized afterwards if necessary. The high shear flows can be generated in many devices including ones considered in this

paper: high-pressure nozzle disintegrator, ultrasonic device and rotor–stator mixers. In this work we are interested in both:experimental investigations and modelling of disintegration of Aerosil 200 V agglomerates in the systems mentioned above. Depending on shear level and related method of shear generation, the breakage kernels based either on rupture or erosion mechanism will be formulated and applied. The population balance modeling will be used to account for effects of breakage and restructuring of aggregates on their...
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