Environmental Engineering Reference
In-Depth Information
d
dd
+
e
i
Slope
=
2
R
d a
R 2
(varying particle size)
Figure C.8
We can use a correlation to obtain the parameter k p :
d p k p
D AB =
60 Re 1 / 2 Sc 1 / 3
Sh
=
2
.
0
+
0
.
,
where
D i q
β .
If we now perform experiments where we vary the particle size, we can generate the plot
in Figure C.8.
A value for
D AB =
δ a will allow us to calculate k a . Likewise, we can obtain D i from the value
of
δ i .
C.2.3 Example C.3: first-order reactions in chromatography
Pulse analysis of chromatography experiments is proposed for a bed packed with solid
catalyst particles of uniform diameter. A first-order irreversible reaction occurs at the
surface of the spherical particles. How may such a procedure be carried out? (a) Show
main steps in the mathematical analysis.
What if the particles are porous? (b) Write an expression for the zeroth moment of an
output pulse for this case.
Solution to part (a)
First-order reaction at surface of particles in a packed column.
Reactant balance:
2 c
c
t =− v
c
D
3
R
(1
α
) k p
t +
z 2
,
mass transfer to particle surface
( c
c s )
α
where c s is the concentration at the surface of the particle.
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