Page 184 - Elements of Chemical Reaction Engineering 3rd Edition

1 56 Isothermal Reactor Design Chap. 4

Simplifying yields

(4-24)

1 I
where

(4-25)

For tubular packed-bed reactors we are more interested in catalyst weight
rather than the distance z down the reactor. The catalyst weight up to a dis-
tance of z down the reactor is

W = (1 -+)A,z X Pc

weight of volume of density of
[ catalyst ] = [ solids [sdidcatalys~ (4-26)

where A, is the cross-sectional area. Tbe bulk density of the catdyst, pb (mass
of catalyst per volume of reactor bed), is just the product of the solid density,
pc , the fraction of solids, (1 - $) :
Pb = pc (l - 4)

Using the relationship between z and W [Equation (4-26)] we can change
our variables to express the Ergun equation in terms of catalyst weight:
Use this form for
multiple reactions dP
and membrane (4-27)
reactors

Further simplification yields
Lety=P/Po
(4-28)

where

(4-29)