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Titre du document / Document title

The effect of bulk concentration gradient on fluid-solid reaction rate

Auteur(s) / Author(s)

PEREZ-TELLO M. (1) ; HONG YONG SOHN (1 2) ; RAJAMANI R. K. (2) ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

(1) Department of Chemical and Fuels Engineering, University of Utah, 135 S. 1460E. Rm 412, Salt Lake City, Utah 84112-0114, ETATS-UNIS
(2) Department of Metallurgical Engineering, University of Utah, 135 S 1460E, Rm 412, Salt Lake City, Utah 84112-0114, ETATS-UNIS

Résumé / Abstract

Considerable attention has been paid to the development of mathematical models to describe fluid-solid reaction systems as they play a significant role in many chemical, metallurgical, and other engineering areas. This work is aimed at examining one of the assumptions generally made in the mathematical modeling of fluid-solid reaction systems: namely, that the bulk concentration of the fluid reactant is uniform around the solid surface. This is a reasonable assumption under well-mixed conditions of the fluid phase. However, under certain conditions, concentration gradients in the axial direction in the fluid near the surface may be present; a packed bed is an example of such a case. It is of interest to investigate how large the concentration gradient should be before the assumption of a uniform bulk concentration around a pellet to cause a significant error. The effect of a fluid concentration gradient has been studied for a catalytic reaction on the external surface of a nonporous sphere. Petersen et al. (1964) found that external concentration gradients do not significantly affect the overall reaction rate except for the case of a second-order reaction when the reactant concentration drops from its maximum value to zero over the distance of a particle diameter, which is a rather unlikely situation in practice. Similar results were obtained by Acrivos and Chambré (1957), who recommended the use of this approximation with caution when a series of consecutive reactions takes place. In many fluid-solid reactions, the reaction progresses towards the interior of the pellet as the solid reactant near the external surface is consumed, leaving behind either a porous solid product or inert solid matrix. Although it is generally believed that a bulk concentration gradient does not significantly affect the behavior of most noncatalytic fluid-solid reactions of industrial relevance, no formal verification of this statement has yet been provided in the literature. In this work, the validity of this hypothesis is tested for a simple fluid-solid reaction configuration.

Revue / Journal Title

Chemical engineering science    ISSN  0009-2509   CODEN CESCAC 

Source / Source

1999, vol. 54, no6, pp. 803-806 (7 ref.)

Langue / Language

Anglais

Editeur / Publisher

Elsevier, Kidlington, ROYAUME-UNI  (1951) (Revue)

Mots-clés anglais / English Keywords

Liquid solid reaction

;

Gas solid reaction

;

Kinetics

;

Conversion rate

;

Medium effect

;

Concentration gradient

;

Modeling

;

Kinetic model

;

Mathematical model

;

Numerical simulation

;

Monte Carlo method

;

Random walk model

;

Theoretical study

;

Mots-clés français / French Keywords

Réaction liquide solide

;

Réaction gaz solide

;

Cinétique

;

Taux conversion

;

Effet milieu

;

Gradient concentration

;

Modélisation

;

Modèle cinétique

;

Modèle mathématique

;

Simulation numérique

;

Méthode Monte Carlo

;

Modèle marche aléatoire

;

Etude théorique

;

Mots-clés espagnols / Spanish Keywords

Reacción líquido sólido

;

Reacción gas sólido

;

Cinética

;

Factor conversión

;

Efecto medio

;

Gradiente concentración

;

Modelización

;

Modelo cinético

;

Modelo matemático

;

Simulación numérica

;

Método Monte Carlo

;

Modelo marcha aleatoria

;

Estudio teórico

;

Localisation / Location

INIST-CNRS, Cote INIST : 7538, 35400007477368.0070

Nº notice refdoc (ud4) : 1698347



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