Gazi University
Faculty of Engineering and Architecture
Department of Chemical Engineering
ChE 341 Chemical Reaction Engineering
Dr. Çiğdem GÜLDÜR
Assist. Dolunay Eslek
PROBLEM SET-3
1. Reactant A decomposes with stoichiometry A
R and with the rate dependent
only on CA. The following data on this aqueous decomposition are obtained in a mixed flow
reactor in terms of concentration of A mole/L:CA0=100mole/L, Volumetric flow rate:5L/sec.
CA0
200
CA
100
(sec) 14
190
90
25
180
80
29
170
70
30
160
60
29
150
50
27
140
40
24
130
30
19
120
20
15
110
10
12
101
1
20
a)What PFR volume is necessary to achieve 40% conversion?
b)What CSTR volume is necessary to achieve 40% conversion?
c)What CSTR volume must be added to raise the conversion in part (a) to 90% conversion?
d)What PFR volume must be added to raise the conversion in part (a) to 90% conversion?
e)Which type of reactor would you prefer to achieve 80% conversion of A in a single reactor
or reactor combinations?
2. We are planning to operate flow reactors to convert A into R. This is a liquid reaction, the
stoichiometry is A
R, and the rate of reaction as a function of concentration is given
in table below.
CA(mol/L)
-rA(mol/L.min)
0.1
0.1
0.2
0.3
0.3
0.5
0.4
0.6
0.5
0.5
0.6
0.25
0.7
0.10
0.8
0.06
1.0
0.05
1.3
2.0
0.045 0.042
a)What size of CSTR is needed for 75% conversion of feed stream of 1000mol A/hr at
CA0=1.2mol/L?
b) What size of CSTR is needed for 75% conversion of feed stream of 1000mol A/hr at
CA0=1.2mol/L?
c)Repeat part (a) with the modification that the feed rate is doubled, thus 2000mol A/hr at
CA0=1.2mol/L are to be treated .
3. We are planning to operate a batch reactor to convert A into R. This a liquid reaction , the
stoichiometry is A
R, and the rate of reaction is given in Table.
a) What space time is needed for the concentration to drop from CA0 =1.3 mol/L to
CAf =0.3mol/L?
b) What size of plug flow reactor is needed for 75% conversion of feed stream of 1000 mol
A/hr at CA0 =1.2 mol/L.
CA(mol/L)
-rA(mol/L.min)
0.1
0.1
0.2
0.3
0.3
0.5
0.4
0.6
0.5
0.5
0.6
0.25
0.7
0.10
0.8
0.06
1.0
0.05
1.3
2.0
0.045 0.042
4. An isothermal PFR is used for the gas phase reaction A
2B+C. The feed, flowing
at 2.0L/s, contains 50% molA and 50% mol inert species. The rate is first order with respect
to A; the rate constant is 2.0s-1.
a) Determine the reactor volume required for 80% conversion of A?
b) What the volumetric flow rate at the exit of the reactor, if xA=0.8?
c) What volume of CSTR would be needed to achieve the same conversion?
5. The irreversible reaction A+B
C+D is carried out isothermally in two flow reactors
in series, first reactor (V1=10L) is CSTR and second one (V2=40L) is PFR. Inlet
concentrations of A and B are 0.01 mol/L and 0.7 mol/L, respectively. The concentration of
product C at the exit of the first reactor is 0.002 mol/L. The reaction is first order with respect
to B. Find the concentration of C at the exit of the plug flow reactor?
6. The following gas phase reaction takes place in three CSTR is connected in series .
A+B
C ; -rA= kCACB
The volume of the first and second reactors are V1=1L and V2=2L. At the inlet of the first
reactor the volumetric flow rate is 0= 0.4 L/s and CA0=CB0=1 mol/L.Reactor operates at
25oC and the reaction rate is 2.6310-3L/mol.s at that temperature. At the exit of the third
reactor overall conversion of A is expected to be 0.95. By using graphical method determine
the outlet conversions from first and second reactor and the volume of the third reactor.
7. Constant density liquid phase reaction
A
B+C
has the rate law,
-rA=k1(CA)1/2/(1+k2CA)
k1=10(mol/m3)0.5h-1 k2=16m3/mol
FA0=100 mol/hr, CA0=0.25mol/m3
What system (i.e. type and arrangement) of ideal flow reactor(s), either one alone or two in
series, would you recommend for continuous processing of a feed pure A if,
a) 50% conversion of A is desired
b) 90% conversion of A is desired
c) What reactor size(s) should be used for part(b)?
8. A first order reaction is to be treated in series of two mixed reactors. Show that the total
volume of the reactors is minimum when the reactors are equal in size.
9. A liquid phase reaction A+2B
C is to be conducted into two equal –sized CSTRs.
The reaction is first order with respect to both A and B with kA=6.010--2Lmol-1s-1. The
volumetric feed rate is 25 L.min-1, CA0=0.1 molL-1 and CB0=0.2 molL-1; 75% conversion of A
desired.
a) The CSTRs are arranged in series . What is the volume of each?
b) The CSTRs are arranged in parallel. What is the volume of each, if the volumetric flow rate
through each reactor is equal?
10. The liquid phase reaction A
B+C takes place in series of three CSTRs with an
overall conversion (xA) of 0.90. One of the reactors developes a leak and is removed from the
series. The throughput (V) is then reduced in order to keep the overall conversion at 0.90. ıf
the original throughput was 250Lmin-1, what is the new thrughput? Assume: (i) steady-state
operation;(ii) the reactors are of equal volume and operate at the same temperature ;(iii) the
reaction is first order in A.
11. Determine the reactor configuration and the minimum total volume for the reaction
A+B
products with the rate law
-rA= k1CA/(K2+CA+CB)
The desired fractinal conversion is 0.85.
Data:
k1= 0.25 molL-1min-1
CA0=CB0=0.25 mol/L-1
K2=0.50 molL-1
0=5.0 Lmin-1
12. Problems 6.1, 6.3, 6.5, 6.7
The textbook: Levenspiel O., “Chemical Reaction Engineering”,3rd ed.(1999).
Solve problem 11 as your homework on 8th of November, 2008.