Biomedical Engineering Reference
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C 0 B 0 /2
of B at the end of the reaction (90% conversion), C B ¼
1 mol/L. We can
either solve the problem by direct mole balance and integration (with an automatic inte-
grator) or find out how the concentration is to vary with conversion before we can follow
the same steps as we did in part 1.
To aid the solution of the problem, we resketched the PFR feeding scheme diagram as
shown in Fig. E5-7.2 and a blowout of the differential section between V and V
(1
0.9)
¼
d V in
Fig. E5-7.3 . Both concentration of A and volumetric rate Q are changing in the reactor but
not independently from each other. We thus need to figure out how these two are related.
þ
V V +
d
V
F A0
Q A
C A0 Q 0
f Ae
Q ,
C B
C Ae ,
C B
B0
Q B
FIGURE E5-7.2 A sketch of the distributed feed PFR.
V
V + d V
Q + d Q
C A , Q
C A + d C A ,
C B
C B
d Q
B0
FIGURE E5-7.3 A sketch of a differential volume (section) in the middle of the distributed PFR.
1. Mole balance on A:
F A j V F A j d V þ r A d V ¼ 0 0
d F A ¼ r A d V
(E5-7.9)
2. Assuming that the density of the B stream is the same as the density of the A stream, as
well as to the mixture, mole balance on B:
F B j V F B j d V þ r B d V þ C 0 B 0 d Q ¼ 0
(E5-7.10)
Since C B ¼
constant and from stoichiometry, r B ¼
r A , we obtain
r A d V þðC 0 B 0 C B Þ
d Q
Z
¼ 0
(E5-7.11)
C 0 B 0 C B d Q ¼
d F A ¼F A 0 d f A
(E5-7.12)
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