INTEC   05402
INSTITUTO DE DESARROLLO TECNOLOGICO PARA LA INDUSTRIA QUIMICA
Unidad Ejecutora - UE
artículos
Título:
Mass Transfer Limitations in Slurry Photocatalytic Reactors: Experimental Validation
Autor/es:
BALLARI, M.; ALFANO, O.M.; CASSANO, A.E.
Revista:
CHEMICAL ENGINEERING SCIENCE
Editorial:
PERGAMON-ELSEVIER SCIENCE LTD
Referencias:
Año: 2010 vol. 65 p. 4931 - 4942
ISSN:
0009-2509
Resumen:
In the present
work the existente of mass transfer limitations in slurry, photocatalytic reactors
is studied. Experimental validation is made in a flat plate reactor that is part
of a recycling system. The reactor is described with a mathematical model previously
developed [Ballari et al., 2008a. Chemical Engineering Journal 136, 50], considering
a transient, two-dimensional mass balance (TDM). The complete reactor model was
developed to show the existence of these effects, which result from the occurrence
of concentration gradients in reaction space. They develop when these reactors are
operated under some operating conditions whose effects should be always analyzed
before assuming the validity of existence of perfect mixing in reaction space. Dichloroacetic
acid (DCA) was the adopted model compound. To solve TDM, a kinetic expression for
DCA acid was determined before under well mixed conditions [Ballari et al., 2009.
Industrial and Engineering Chemistry Research 48(4), 1847]. The studied variables
are flow rate, catalyst loading, and irradiation rates. The experimental data agree
quite well when they are interpreted in terms of the two-dimensional model (TDM)
regardless of the operating mode. The perfect mixing model (PMM), normally employed
to describe this and other types of slurry photoreactors, does not have the same
level of universal application; i.e. it is restricted to perfect mixing, but in
many cases far simpler to use. However, it can be concluded that when the photocatalytic
reaction is not fast, employing catalyst loadings below 1gL1, irradiation
rates at the reactor wall below 1x10x-6 Einstein cm-2 s-1
and good mixing operation (Re41700) it will be always safe to assume that mass
transport limitations in the bulk of the fluid are non existent. In a typical batch
reactor the above flow conditions are equivalent to very intense mixing. If the
catalyst concentration is in creased, the mixing conditions should be improved in
the same proportion. Within limits, higher solid loadings can be compensated with
lower irradiation rates[Ballarietal.,2008a. Chemical Engineering Journal 136, 50].
In addition, with the validated model, additional simulations are shown, operating
the reactor under different virtual reactor thicknesses to widen amplitude of the
reached conclusions. These findings Hill be useful in kinetic studies to prevent
incursion in certain ranges of experimental conditions that could lead to erroneous
interpretation of the obtained kinetic data.