Episode 52 : Flow sheeting Case Study A Standard Test Problem for Flowsheeting The Cavett Problem * A typical flowsheeting problem from the petroleum industry * The flowsheet consists of mixers and TP-flash units * The mixture consists of ethane, propane, 1- butane, n-butane, i-pentane, n-pentane * The problem is interesting because tear-stream convergence is not easy and process is very sensitive to changes to the condition of operation SAJJAD KHUDHUR ABBAS Ceo , Founder & Head of SHacademy Chemical Engineering , Al-Muthanna University, Iraq Oil & Gas Safety and Health Professional – OSHACADEMY Trainer of Trainers (TOT) - Canadian Center of Human Development

1. SAJJAD KHUDHUR ABBAS
Ceo , Founder & Head of SHacademy
Chemical Engineering , Al-Muthanna University, Iraq
Oil & Gas Safety and Health Professional – OSHACADEMY
Trainer of Trainers (TOT) - Canadian Center of Human
Development
Episode 52 : Flow sheeting
Case Study

2. A Standard Test Problem for Flowsheeting
The Cavett Problem
* A typical flowsheeting problem from the
petroleum industry
* The flowsheet consists of mixers and TP-flash
units
* The mixture consists of ethane, propane, 1-
butane, n-butane, i-pentane, n-pentane
* The problem is interesting because tear-stream
convergence is not easy and process is very
sensitive to changes to the condition of operation

3. Cavett Problem : Process Flowsheet

4. Cavett Problem : Problem Definition
T=311.12, P=13.609
T=322.22, P=10.207
T=307.78, P=5.444
T=302.78, P=2.722
ethane
propane
1-butane
n-butane
i-pentane
n-pentane

5. Solution Statistics: Solve mass balance & then energy balance - mass balance converged in 3
iterations. Note that there were 2 tear-streams

6. Solution Statistics: Solve mass balance & then energy balance - energy balance converged in 1
iteration. Note that there were 2 tear-streams

7. Steady State Simulation Results: Stream Summary

8. Tutorial Outline
The objective of the tutorial is not an attempt to make the participant an
expert in process simulation or in the software used in the tutorial. The
objective is to illustrate and highlight what is available currently and how
they can be used to solve practical problems. Currently, large collections of
computational tools (commercial or academic) are available and ready to be
used. Many practical problems can be solved more efficiently through their
use. The lecture and the tutorial are aimed at providing participants with
sufficient background information so that when they come across process
simulation problem that may require the use of a process simulator, they will
be able to start without too much extra training.
* Introduction to the software: ICAS - Integrated Computer Aided System
* Problem Description: Mass balance, mass & energy balance, use of the
integrated system concept (flowsheet analysis, properties prediction,
separation technique identification, …)

9. ICAS: TOOLS (Use only the underlined features)
* Integrated Option/Stand-alone tools
Integrated Option
Modeling, simulation, toolbox (properties utilities,
synthesis, modeling, solvent design,
data/parameter estimation)
Stand-alone
ProPred, ProCamd, ModGen/MoT, CAPSS, Data

10. Use of ICAS
Getting Started (when the PC is ready for use)
1. Double click on the ICAS icon
2. Click once on the ICAS icon
on the ICAS starting screen
ICAS Starting Screen
ICAS starting screen shows various tools that
can be selected to solve any problem. The ICAS
icon takes the user to the ICAS main screen
from which problems can be solved in an
integrated manner. In this workshop we will
work from ICAS main screen only (see also
On-line Help).

11. Problem Description
We take the case of the reaction
i-C4 + MeOH = MTBE ; 1-C4 is inert
One stream containing i-C4 & 1-C4 and
another stream containing methanol,
enters the reactor. There is 50%
conversion of methanol. The effluent from
the reactor is separated in a split
fractionator. MeOH and MTBE all go
down while the two butenes go up. The
butene-stream is purged 20% and the
remaining is recycled back to the mixer
Perform steady state mass balance only (as
the first step) - please follow the

12. Problem Solution Steps
Problem Definition in ICAS (use of thermo-utilities)
1. Enter the ICAS main screen
2. Draw a stream or flowsheet
3. Select the compounds in the mixture (if
compounds are not available in the database, use
ProPred to estimate properties)
4. Define the stream (stream specification page)
5. Select calculation options
6. Select thermo-model options
7. Start the computations

13. Draw the flowsheet by using the drawing tools
Drawing tools

14. Explanation of the tool-bar icons (see also on-line help)
Synthesis
Start
simulation
Select
compounds
Choice of balance equations
and flowsheet decomposition
Simulation task
definition and
selection

15. The next step is to specify the compounds. Click on the ICON on the tool-bar for adding compounds.
You will enter the databank of your choice. Click on the compound to see their pure component
properties. Click on PROPRED for their prediction (if necessary).

16. On return to the ICAS main screen, double click on the input stream. The mixture
specification screen appears. Give T, P & x. Click on the first ICON on the left

17. Before the calculations can be started, thermo-models must be selected. A
selection is shown on the screen below. Click OK to return.

18. From ICAS main screen, click on the reactions icon to select a predefined reaction. Note that a
stoichiometric model is being selectd.

19. Details of the model can be viewed by clicking on the lower tool-bar reaction icon

20. Double click on tank (CSTR) to enter the reactor module. Click on the reactions ICON to specify
the conversion. Note that from the ICAS main screen, the MTBE reaction must be chosen first
Reaction
ICON on
ICAS main
screen
Reaction ICON on
the tank module

21. Double click on one of the streams going out of the splitter to define the split factors. Set these
variables as known. Also, check the “split factor” box

22. Repeat the same procedure for the divider by double clicking on the purge stream

23. Click on the icon for flowsheet decomposition and the recycle loop will be shown within the red
boundary together with the dotted line for the tear stream (stream 3)
Click here for flowsheet decomposition
Click here for
choosing the balance
option (mass balance
only -in this example)

24. After flowsheet decomposition, the simulation task needs to be defined and then from the predefined
tasks, one or more is selected (as shown in the figure)
Simulation
task selection
Define simulation task
Choose default options

25. Final step is to choose the method of solution and then to start the simulation, click on the run
icon (as indicated on the figure)
Choose the
default options
Click here to run the
simulation problem

26. We can continue to proceed forward with
generating different alternatives, performing
steady state simulation and then analyzing
the results to check if our design objectives
have been satisfied.
If solvents are needed, the tool CAMD can be
used to find a solvent. If a new compound is
to be introduced, ProPred can be used to
predict the properties of this compound.
Finally, if a new model is needed, MoDef can
be used to generate a new model.

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