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Gassolid reaction model for a
shrinking spherical particle with
unreacted shrinking core
BY : ARPIT THUMAR
DISHANK ZALA
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outline
INTRODUCTION
HETROGENOUS REACTION MODEL:
1) shrinking particle model
2) unreacted shrinking core model
REACTION KINETICS
VALIDATION OF MODEL:
1) BY NUMERICAL METHOD
2) BY EXPERIMENTAL DATA
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RESULTS:
1) Movement of reaction fronts2) Diminishing point of unreacted
core
3) Effective range of the model
CONCLUSIONS
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ABSTRACT:
Gassolid reaction model for a shrinking
spherical particle with unreacted shrinking core.
PaperBY : Shunji Homma, Shinji Ogata, Jiro Koga,
Shiro Matsumoto
(Department of Applied Chemistry, SaitamaUniversity, 255
Shimo-Okubo, Sakura-ku,
Saitama 338-8570, Japan)
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Introduction
A heterogeneous reaction model is developed torepresent the
gassolid reaction consisting oftwo-step reactions:
formation of a solid intermediate on the core ofunreacted
solid.
consumption of the solid intermediate.
The model successfully represents thefluorination of uranium
dioxide where uraniumhexafluoride gas is produced through
uranylfluoride as a solid intermediate.
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HETROGENOUS REACTION MODEL:
1) Shrinking particle model:
Reactions are confined at the surface of the
particle and the size of the particle is reduced
by gasification of the products or flaking off
the solid products.
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Shrinking particle model
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2)Unreacted shrinking core model :
Applied when the reactant is converted to
another solid material leaving behind theunreacted solid.
The converted material, which is sometimescalled ash, is
regarded as porous and inertsubstance, so that the gas reactants
candiffuse from the external surface of theparticle to the surface
of the unreacted core.
Thus, the unreacted core shrinks as thereaction proceeds, but
the overall particle sizebasically remains constant.
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Unreacted shrinking core model
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Chemical reaction by which the converted
solid material is consumed, also causes the
reduction of the particle size.
In this case, both the unreacted core and the
particle itself shrink with different speeds, so
that two moving surfaces, reaction fronts,
must be taken into account in the reactionmodel.
