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2-18
P2-9 (f)
Real rates would not give that shape. The reactor volumes are absurdly large.
P2-10
Problem 2-10 involves estimating the volume of three reactors from a picture. The door on the
side of the building was used as a reference. It was assumed to be 8 ft high.
The following estimates were made:
CSTR
PFR
Length of one segment = 23 ft
P2-11 No solution necessary.
P2-12 (a)
The lightly shaded area on the left denotes the CSTR while the darker shaded area denotes the
P2-12 (b)
Calculate the necessary amount of catalyst to reach 80 % conversion using a single CSTR by
determining the area of the shaded region in the figure below.
P2-12 (c)
The CSTR catalyst weight necessary to achieve 40 % conversion can be obtained by calculating
the area of the shaded rectangle shown in the figure below.
2-20
P2-12 (d)
The catalyst weight necessary to achieve 80 % conversion in a PBR is found by calculating the
area of the shaded region in the figure below.
P2-12 (e)
The amount of catalyst necessary to achieve 40 % conversion in a single PBR can be found from
calculating the area of the shaded region in the graph below.
2-21
P2-12 (f)
P2-12 (g)
For different (-rA) vs. (X) curves, reactors should be arranged so that the smallest amount of
CDP2-A (a)
Over what range of conversions are the plug-flow reactor and CSTR volumes identical?
We first plot the inverse of the reaction rate versus conversion.
2-22
i.e.
CSTR
A
A
A
A
A
PFR V
r
XF
dX
r
F
r
dX
V=
!
=
"
!
=
"!
=0
5.0
0
0
5.0
0
CDP2-A (b)
What conversion will be achieved in a CSTR that has a volume of 90 L?
For now, we will assume that conversion (X) will be less that 0.5.
CSTR mole balance:
CDP2-A (c)
This problem will be divided into two parts, as seen below:
2-23
CDP2-A (d)
What CSTR reactor volume is required if effluent from the plug-flow reactor in part (c) is fed to a
CSTR to raise the conversion to 90 %
CDP2-A (e)
If the reaction is carried out in a constant-pressure batch reactor in which pure A is fed to
the reactor, what length of time is necessary to achieve 40% conversion?
2-24
Combine:
dt
dX
NVr AA 0
=
From the stoichiometry of the reaction we know that V = Vo(1+eX) and e is 1. We insert
this into our mole balance equation and solve for time (t):
After integration, we have:
CDP2-A (f)
Plot the rate of reaction and conversion as a function of PFR volume.
The following graph plots the reaction rate (-rA) versus the PFR volume:
2-25
CDP2-A (g)
Critique the answers to this problem.
The rate of reaction for this problem is extremely small, and the flow rate is quite large. To obtain
CDP2-B Individualized solution
CDP2-C (a)
CDP2-C (b)
CDP2-C (c)
CDP2-C (d)
2-27
2-28
CDP2-C (e)
CDP2-D
2-29
CDP2-D (a)
CDP2-D (b)
CDP2-D (c)
CDP2-D (d)
2-30
CDP2-D (e)
CDP2-D (f)
CDP2-D (g)
CDP2-D (h)
CDP2-E
CDP2-F (a)
Find the conversion for the CSTR and PFR connected in series.
X
-rA
1/(-rA)
0
0.2
5
2-32
CDP2-F (b)
2-33
CDP2-F (c)
CDP2-F (d)
2-34
CDP2-F (e)
CDP2-F (f)
CDP2-F (g) Individualized solution
