Page 137 - Elements of Chemical Reaction Engineering 3rd Edition

Sec. 3.!5 Reactions with Phase Change 109

Equating Equations (E3-10.1) and (E3-10.2) gives

XC
0.158 = - (E3-, 10.3)
3 - x,
Solving for X, yields

Before condensation begins: For X < Xc there is no condensation and one can use
the basic equations for 6 and e to calculate the concentrations; Le.,

(E3-10.4)

1 -X
= '.'(l- 033x1 (E3-10.5)

2- 2x - 2C.4,(1-X)
'' = 1 - 0.33X) - (1-10.33x) (E3-10.6)

Because the temperature and pressure are constant, the total concentration is con-
stant.
Z,RTo - '"
PO.
P
,c = - = - - (E3-10.7)
ZRT
The reaction rate is first-order in A and in B for X < X,:
I c I
(E3- 10.8)

After condensatioh begins: For X > Xc the partial pressure of D is equal to the
vapor pressure (PD = P"). The volumetric flow rate is related to the total molar flow
rate through thae ideal gas equation of state:
-rA will be a
different function (E3-I 0.9)
of conversion FT = CTV
befoye and after
condensation FTO = 'TO UO (E3- 10.10)
Then, taking the ratio of Equation (E3-10.9) to Equation (E3-10.10) and rearrang-
ing, we have