Page 228 - Elements of Chemical Reaction Engineering 3rd Edition

200 isothermal Reactor Design Chap. 4

Case 2 Inert gas is bubbled through the reactor

In this case we assume the reaction product is carried off by either “boil
off” or an inert gas being bubbled through the reactor. When gas is bubbled
-through the reactor, we assume vapor-liquid equilibrium and that the mole
fractions in the gas and liquid are related by Raoult’s law,

(4-86)

where P,, is the vapor pressure of D. We now set either the boil off rate by
setting the heat flux to the reactor or set the molar flow rate at which an inert
is bubbled through the reactor, FI.
The molar flow rate of D in the gas phase is

Assuming only D evaporates (see the CD-ROM for the situation when this is
nd the case) the total molar gas flow rate is the inert gas molar flow rate plus
the molar flow rate of the evaporating species, in this case species D, is
F,= F,+F,= F,-i-y,F,

The molar flow rate of D leaving the liquid is

(4-87)

This equation is now coupled with all the mole balances, e.g.,

-
dNA -I -k(NANB -NcND)
dt V

and solved with an ODE solver.

4.8 Recycle Reactors
Recycle reactors are used when the reaction is autocatalytic, or when it is pec-
essary to maintain nearly isothermal operation of the reactor or to promote a