Simulation of a Continuous Stirred Tank Reactor

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Swansea University 2021
EG-208 Process DesigŶ & SiŵulatioŶ
AssigŶŵeŶt 2
Weighting: 75% of Final Module Mark
Issue Date: 26th April 2021
Deadline Date: Monday 10th of May @ 13:00 BST
Submission: Via CANVAS
Type of Assignment: Individual submission
General Guidance:
This assignment comprises of three parts.
Part 1 – Simulation of a continuous stirred tank reactor (25 Marks)
Part 2 – Simulation of a binary distillation column (35 Marks)
Part 3 – Refinery Exercise with mistakes (15 Marks)
A submission point for each Part of the assignment will be made available on CANVAS.
Details of what should be submitted for each part are provided with the guidance for each part and
will be stated clearly on the CANVAS Submission point. Each submission point will allow you 3 attempts
to upload the necessary files.
Please read the guidance for each part of the assignment carefully.
Academic Misconduct
You can work in your study groups to discuss the tasks in this assignment. But the documents and
simulation files you submit for assessment must be your own individual work.
Do not share your simulation files with each other. If you do, you will run the risk of being detected
and reported for academic misconduct.
Late Submission
Please note the College of Engineering has a ZERO Tolerance policy on late submission.
Be aware that CANVAS can sometimes report a submission LATE if it is submitted on the deadline. You
are therefore advised to ensure you submit your work before the deadline.
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Swansea University 2021
Part 1: Simulation of a Continuous Stirred Tank Reactor (CSTR)
This component of the assignment is worth 25 Marks. You will utilize your knowledge of reactor design
to determine the necessary volume in a CSTR to achieve 95% conversion of the limiting reactant. You
will then verify your calculations using a simulation constructed in UNISIM or ASPEN HYSYS, and
discuss the results.
Relevant Theory
The behaviour of a CSTR is often modelled as an ideal perfectly mixed reactor. The model of a CSTR is
often used to simplify engineering calculations
A basic flowsheet for a CSTR unit is presented in Figure 1.
Figure 1: Basic flowsheet for a CSTR
Assuming perfect or ideal mixing, the steady-state material balance for the CSTR reactor can be
expressed as follows:
�஺0ܺ + �஺ܸ = Ͳ
FA0 -= Molar flow of key component A,
X = Conversion of reactant A
rA = Reaction rate
V = Volume of reactor.
The concentration, CA, of component A in the exit stream can be given by,
ሻ − ܺ0ሺͳ஺ܥ = ஺ܥ
The reaction rate to the n
th order with respect to component A can be expressed as,
஺ܥ�− = ஺�

The rate constant, k, is provided by the Arrhenius Equation:
−�ܣ = �

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Swansea University 2021
A = Pre-exponential factor
E = Activation energy, J mol-1
R = Ideal gas constant, 8.314 J mol-1 K-1
T = Temperature, K
Problem Description
A CSTR reactor, operating isothermally at 3.5 atmospheres and 50 °C, is being used to continuously
produce triethylamine by reacting ethanol with diethylamine. This is a liquid phase reaction that takes
ܦ + ܥ → ܤ + ܣ
Where A = Ethanol, B, = diethylamine, C = water, and D = triethylamine.
The reaction is second order with respect to ethanol.
The feed to the CSTR consists of 50 kmol hr-1 of ethanol, 50 kmol hr-1 of diethylamine, and 100 kmol
hr-1 of water.
Task – Determining the required reactor volume
Your task for Part 1 of the assignment is to perform hand calculations to determine the required
volume of the CSTR that will achieve 95% conversion of ethanol. You are then required to build a
simulation using either UNISIM or ASPEN HYSYS to verify your hand calculations.
Table 1 contains data for the constants in the Arrhenius equation, and values for molar densities that
you will require.
Table 1: Data required for calculations.
Activation energy, E 1×104
J mol-1
Pre-exponential factor, A 4775 L mol-1 hr-1
Molar density of ethanol 16.6 mol L-1
Molar density of diethylamine 9.178 mol L-1
Molar density of water 54.86 mol L-1
Submission of work
For Part 1 you will produce a simulation file and a PDF document containing your hand calculations, a
written summary of the steps you performed to build up your simulation, and a discussion of the
simulation results. Further explanation is provided below.
Hand Calculations
Your hand calculations must be presented clearly, and the logic behind each calculation step clearly
shown. Your solution must be clearly typed up and the equation editor should be used to present any
You should clearly state the volume of the reactor required and specify the units.
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Swansea University 2021
You are required to use either the application UNISIM or ASPEN HYSYS to create your simulation.
Ensure you have selected a suitable unit system for your simulation case. When specifying the
reaction, be mindful of the inputs you provide on the Stoichiometry, Basis and Parameters tabs.
In your written summary of how you built up the simulation, you should clearly state the fluid package
/ thermodynamic model used and your justification for using it. Your written summary needs to clearly
explain how you inputted the reaction details into the simulation package. You should clearly
summarize the parameters used in your CSTR simulation. You are free to utilize screen shots from the
software in your summary as required.
You must clearly discuss whether the simulation verifies your hand calculations. If there are
discrepancies between the simulation and the hand calculation, discuss whether they are within
acceptable error and if not, what further steps would you suggest.
You well be expected to submit a copy of your UNISIM Casefile or ASPEN HYSYS simulation file for
Mark Breakdown:
Hand calculations: 7 Marks
Simulation File: 13 Marks
Written presentation of hand calculations, summary, and discussion of simulation results: 5 marks
[TOTAL for Part A: 25 Marks]
Files to be submitted for Assessment of Part 1
A single PDF file that contains the following:
• Your hand calculations, with the relevant calculation steps presented in a clear and logical
• A summary of how you built up the simulation file and specified your CSTR Reactor.
• A comparison and discussion of the simulation result with those of your hand calculations.
A copy of your simulation file for consideration. This must be either a UNISIM (.usc) casefile or an
ASPEN HYSYS (.hsc) casefile.
It is recommended that your name your files as student number_part1 e.g.
PDF file →012345678_part1.pdf
UNISIM file → 012345678_part1.usc
ASPEN HYSYS file → 012345678_part1.hsc
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Swansea University 2021
Part 2: Simulation of a binary distillation column
Problem Description
A saturated liquid consisting of 40 mol% Cumene (C9H12) in 60% Benzene (C6H6) is fed continuously at
a rate of 20 kmol h-1 to a distillation column. The distillation column is expected to produce two
product streams. One stream should contain 99 mol% Cumene, while the other product stream should
contain 98 mol% benzene. The column operates with a total condenser and partial reboiler, under a
system pressure of 1.75 bar absolute. The condenser operates such that the reflux is returned as a
saturated liquid to the column.
Figure 2: A continuous distillation column
Task – Determining suitable reflux ratio & number of stages.
For Part 2 you are required to perform hand calculations to determine:
• The number of ideal stages in the column.
• Location of the stage on which the feed should be introduced.
• Determine a suitable reflux ratio which provide stages.
You are then expected to verify your hand calculations by:
• Simulating the separation in ASPEN PLUS using the DSTWU Column; which performs shortcut
distillation calculations.
• Simulating the separation in ASPEN PLUS using the RadFrac Column; which performs a
rigorous plate to plate calculations.
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Swansea University 2021
Hand Calculations
Obtaining the Vapour Liquid Equilibria Data.
Before you can perform the necessary hand calculations, you must first acquire the relevant Vapour
Liquid Equilibria (VLE) Data from ASPEN PLUS and export the data into EXCEL.
To obtain the necessary VLE data, use the ͞Property AŶalysis Tools͟ iŶ A“PEN PLU“ to geŶerate VLE
based on the NRTL property method.
Once you have generated your VLE data, Export/Copy Paste the data into EXCEL to enable you to
utilize the data in your hand calculations.
[Generation & Export of VLE data to EXCEL – 2 Marks]
Determining the minimum number of ideal stages.
Determine the minimum number of ideal stages for the desired separation using a graphical approach,
and then verify the value using the Fenkse Equation.
Fenske Equation
�௠�௡ =
log {ቀ


[Determine minimum number of ideal stages graphically – 1 marks]
[Verification with Fenske Equation – 1 marks]
Determining the minimum reflux ratio
Determine the minimum reflux ratio using a graphical approach, and then verify the value using the
Underwood Equation.
Underwood Equation
�௠�௡ =
∝ −ͳ [
ሺͳ − �஽஺ሻ
ሺͳ − �ி஺ሻ
[Determine minimum reflux ratio graphically – 1 marks]
[Verification with Underwood Equation – 1 marks]
Determining number of ideal stages in column & feed location.
Choose a suitable reflux ratio and determine the number of ideal stages and the location of the feed
tray using the McCabe Thiele Method. For the same reflux ratio use the Gilliland Correlation to
determine the number of ideal stages, and the Kirkbride Equation to determine the location of the
feed tray. Compare and discuss the values obtained from the Gilliland and Kirkbride shortcut
equations, with those obtained from the McCabe Thiele Method.
Gilliland Correlation
� − �௠�௡
� + ͳ = Ͳ.͹ͷ ቆͳ − (� − �௠�௡
� + ͳ )
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Swansea University 2021
Kirkbride Equation
ln (
) = Ͳ.ʹͲ͸ lnቌ(�஻

�஺,�௡ �
�஻,�௡ ஽ ቇ
[Apply McCabe-Thiele Method – 2 marks]
[Apply Gilliland correlation – 1 Marks]
[Apply Kirkbride Equation – 1 Marks]
[Comparison & Discussion – 10 marks]
N = number of stages in column, (the reboiler is considered a stage in UNISIM)
Nmin = minimum number of stages in column
XA = mole faction of most volatile component
XB = mole fraction of least volatile component
α = average relative volatility of component A with respect to component B
D = Distillate product molar flow in kmol h-1
W = Bottom product molar flow in kmol h-1
Subscripts F, D, W refer to feed, distillate and bottom product respectively.
[Total Marks for Hand Calculations in Part B: 20 Marks]
Verification – Simulation using ASPEN PLUS
You will now try to use ASPEN PLUS to simulate the simulation, firstly using the DSTWU shortcut
column that utilizes the Winn – Underwood – Gilliland shortcut method, and the RadFrac column that
performs rigorous plate to plate calculations. You should use the same simulation file you created to
obtain the VLE data using the Property Analysis Tools. This will ensure the same VLE data is used for
your simulations.
You will simulate both columns in the same ASPEN PLUS file, an example of the resulting flowsheet is
shown in Figure. 3. It is recommended that you simulate the DSTWU column first, and then add the
RadFrac column afterwards.
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Swansea University 2021
Figure 3: Example of expected ASPEN PLUS flowsheet
Briefly summarize how you specified the DSTWU and RadFrac columns to simulate the separation.
Please Note: When specifying the RadFrac column on the Configuration Tab, you do not need to click
the ͞DesigŶ aŶd speĐify ĐoluŵŶ iŶterŶals͟ ďuttoŶ.
Compare and discuss the results from the two simulated distillation columns with those of your hand
calculations. Are the values in agreement?
[Specifying DSTWU and RadFrac Columns – 5 marks]
[Written summary of simulation specification, results comparison, and discussion – 10 marks]
[Total Marks for ASPEN Simulation in Part B: 15 Marks]
[TOTAL for Part B: 35 Marks]
Files to be submitted for Assessment of Part 2
A single PDF file that contains the following:
• Summary of your hand calculations presented in a clear and logical manner.
• Your discussion and comparison of the values between the graphical and analytical hand
calculation techniques.
• A brief summary of how you specified the DSTWU and RadFrac columns in your ASPEN PLUS
• Your comparison and discussion of the simulation results with those of your hand
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Swansea University 2021
A copy of your ASPEN PLUS (.apw) simulation file for consideration.
It is recommended that your name your files as student number_part2 e.g.
PDF file →012345678_part2.pdf
ASPEN PLUS file → 012345678_part2.apw

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Swansea University 2021
Part 3: Refinery Exercise with Mistakes
For part 3 you have two tasks to complete, Task 3A and Task 3B. Task 3A involves identifying errors
in a supplied UNISIM Simulation File. Task 3B requires you to submit a copy of the simulation
exercise from either Week 31 or Week 32.
Part 3A: Refinery Exercise with Mistakes
Download from canvas the following UNISIM Simulation file from CANVAS. The file will be located on
the same CANVAS page as this guidance document.
Refinery Exercise with MISTAKES.usc
It is version of the Refinery column simulation exercise from Week 24 and will form your starting basis
for this task. However, there are errors in the simulation file.
Your task is to identify and analyse these errors. You expected to rectify the errors that you find so
that the simulation should then work correctly and converge to solution.
The complete simulation is similar to the Week 24 class exercise but different in some ways. You are
only permitted to use the version of the simulation file provided on CANVAS to complete this task. If
you submit the version you generated in Week 24, you will lose marks.
For correctly identifying the mistakes and getting a complete successful simulation you will get a
maximum of 10 marks. Partial marks may be awarded depending on the level of success in identifying
these errors.
You need to maintain discipline in saving your work, you also need to think about the order in which
you rectify the mistakes, if you do it in an incorrect order then other mistakes may be difficult to
[Part 3A – 10 Marks]
Part 3B: Aspen Plus Simulation
You are required to upload one of the following class exercises carried out with ASPEN. We will be
looking for specific data and constants that confirm you have successfully performed the exercise.
You must include in your submission: Either
(1) A copy of your simulation on Modelling Solid Processes from Week 31
(2) A copy of your simulation on Modelling Fluidized Bed Reactor from Week 32
[Part 3B – 5 Marks]
[Total Marks for Part 3 – 15 Marks]
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Swansea University 2021
Files to be submitted for Assessment of Part 3
Two Simulation files should be submitted for consideration in Part 3:
• A copy of your corrected UNISIM (.usc) Simulation file for Part 3A
• A copy of your ASPEN PLUS (.apw) file for the Week 31 or Week 32 Exercise.
It is recommended that your name your files as student number_part3 e.g.
UNISIM file →012345678_part3A.usc
ASPEN PLUS file → 012345678_part3B.apw
[Total Marks for Assignment 2 – 75 Marks]
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