
354 Green Chemical Engineering
where L
0
is the equivalent length of the catalyst pellet that is equal to L for slab, R/2 for
cylinder and R/3 for sphere. Consider a catalyst pellet (Figure 4.25) of some regular shape
in contact with the gas stream containing reactant A at concentration C
Ag
.
The ux of A from the bulk gas to the surface of the pellet is
Nk
AgAg AS
(4.217)
where
k
g
: gas lm mass transfer coefcient
Equating Equations 4.216 and 4.217, we get
NkCC kLC
AgAg AS po AS
()
(4.218)
Solving Equation 4.218 for C
AS
, we get
C
k
kkL
C
AS
g
gpo
Ag
=
+
ηρ
(4.219)
Substituting Equation 4.219 for C
AS
into Equation 4.216, we get the global rate equation ...