
160 Green Chemical Engineering
Consider the PFR followed by the CSTR, the rate equation for the rst-order reaction is
x
Af
x
A1
V
C
A0
A
= 0
V
k
()
rk
AA
1
Space time τ for the PFR is
τ=
−
()
=− −
∫
C
dx
rx k
x
AO
A
AA
x
A
Af
()
ln
1
1
1
A
k
1
1=−
Space time τ for the CSTR is
τ=
−
(
)
=
−
Cx x
rx
AO Af A
AAf
Af A
Af
()
()
1
C
A0
X
A
X
Af
X
A1
PFR
= Area AB
OADE =
C
D
E
0
A
B
τ
x
A1
is calculated
such that area OADE = area
ABCD
C
A0
CSTR
τ
–r
A
(x
A
)
1
FIGURE 3.15
Graphical method for calculation of x
Af
for CSTR followed by PFR.