TUTORIAL JAN 2019
REACTION ENGINEERING (CKB 20104)
REACTION ENGINEERING (CKB 20104)
TUTORIAL 2
CHAPTER 2: CONVERSION AND REACTOR SIZING
1. Given equal molar of gas mixture A and B enters the reactor at 250 dm 3/s and 125C. Calculate the
initial concentration and molar flow rate of A if
(a) The initial partial pressure of A is 250 kPa (Ans 0.076 mol/dm3, 19.0 mol/s)
(b) The total pressure of the system is 1500 kPa. (Ans 0.2266 mol/dm3, 56.65 mol/s)
2. A mixture of 30 mol% SO2 at 10 mol/s of O2 and the balance air is charged to a flow reactor in which
SO2 is oxidized to form SO3.
O + 2SO → 2SO
2
2
3
Given the total initial pressure of the system as 15.0 atm and temperature of 230 C. Assume air
contains 79 mol% of N2 and the balance O2.
(a) Calculate the initial concentration of O2 and the initial volumetric flow rate. (Ans 0.053 mol/dm3,
188.68 dm3/s)
(b) Calculate the % conversion of O2 if given the outlet flowrate of O2 as 5.55 mol/s. (Ans 44.5%)
3. A mixture consists of 3.5M pure A enters the reactor at a rate of 10.0 dm3/s.
Conversion, X
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.85
–rA (mol/dm3.s)
0.053
0.052
0.050
0.045
0.040
0.033
0.025
0.018
0.013
0.01
By using the data above, calculate the total reactor volumes for all the schemes below
(a) Scheme A: PFR → CSTR if given the intermediate conversion as 35% and the final conversion as
75%. (Ans: 1151.51 dm3)
(b) Scheme B: CSTR → PFR if given the intermediate conversion as 35% and the final conversion as
75%. (Ans: 815.52 dm3)
(c) Single CSTR with final conversion of 75% (Ans: 1693.55dm3)
(d) Single PFR with final conversion of 75% (Ans: 789.05 dm3)
State the conclusion from the answers on which configuration should be selected for the reaction.
1
DR. KELLY 2019
TUTORIAL JAN 2019
REACTION ENGINEERING (CKB 20104)
4. The adiabatic exothermic irreversible gas-phase reaction 2A + B → 2C is to be carried out in a flow
reactor for an equimolar feed of A and B. A Levenspiel plot for this reaction is shown in Figure 1.
Figure 1 Levenspiel plot
(a) Calculate the PFR volume necessary to achieve 50% conversion. (Ans 150,000m3)
(b) Calculate the CSTR volume necessary to achieve 50% conversion. (Ans 50,000m3)
(c) Determine the volume of second CSTR added in series to the first CSTR (part ii) necessary to
achieve overall conversion of 80%. (Ans 150,000m3)
(d) Determine the PFR volume that must be added in series to the first CSTR (part ii) to raise the
conversion to 80%. (Ans 90,000m3)
2
DR. KELLY 2019
TUTORIAL JAN 2019
REACTION ENGINEERING (CKB 20104)
5. The gas-phase reaction is given as follows
A ® B +C
The irreversible reaction is carried out isothermally in a flow reactor. The inlet gas mixture consists of
45 mol% of inert and the balance A. The reaction is conducted at 40.0 C. The partial pressure of the
inert is 5 atm. The Levenspiel plot for the reaction is given as follows.
22
20
18
16
14
12
10
8
6
4
2
0
0
0.1
0.2
0.3
0.4
0.5
0.6
Conversion, X
0.7
0.8
0.9
(a) Determine the volume of a single continuous stirred tank reactor required to achieve 60%
conversion of reactant A with initial rate of 10 dm3/s. Subsequently, calculate the volume of a
second plug flow reactor added in the series to the first continuous stirred tank reactor necessary to
achieve an overall conversion of 80%. Calculate the outlet molar flow rate from the plug flow
reactor. (Ans: 12.14 dm3, 6.23 dm3, 0.476 mol/s)
(b) Determine the space time of a single plug flow reactor required to achieve 30% conversion of
reactant A. Subsequently, calculate the space time of a second continuous stirred tank reactor
added in the series to the first plug flow reactor necessary to achieve an overall conversion of 70%.
(Ans: 0.2142s, 1.19s)
(c) Determine the inlet molar flow rate of a 10dm 3 single plug flow reactor and a 10dm 3 single
continuous stirred tank reactor to achieve final conversion of 50%. (Ans: 5.2174mol/s,
2.8571mol/s)
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DR. KELLY 2019
TUTORIAL JAN 2019
REACTION ENGINEERING (CKB 20104)
6. The irreversible gas phase reaction consisting of A and B mixture is to be carried out isothermally in a
constant pressure batch reactor. The inlet is at 250oC, 1013 kPa, with 35 mol% B initially. All calculations
are done based on A as the basis of calculations. Laboratory data taken under identical condition are as
follows.
Conversion, X
0
0.2
0.4
0.6
–rA (dm .min/mol)
0.01
0.005
0.002
0.001
3
(a) Determine the volume of a plug flow reactor required to achieve 50% conversion of A with the rate
of 2 dm 3/min. Subsequently calculate the volume of a second CSTR connected in series to take the
effluent from the first plug flow reactor (PFR) above in part (a) to achieve 60% total conversion
(based on species A fed to the PFR). (Ans: 42.70dm3, 30.0 dm3)
(b) Determine the space time of a single continuous stirred tank reactor required to achieve 30%
conversion of reactant A. Subsequently, calculate the space time of a second plug flow reactor
added in the series to the first reactor necessary to achieve an overall conversion of 50%. (Ans:
12.86min, 14.76min)
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DR. KELLY 2019