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TRANSCRIPT
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SISTEM DINAMIK
CSTR HEAT EXCHANGE MODEL
Disusun Oleh :
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Introduction
A CSTR (Continuous Stirred-Tank Reactor) is a chemical
reaction vessel in which an impeller continuously stirs the contents
ensuring proper mixing of the reagents to achieve a specific output.Useful in most all chemical processes, it is a cornerstone to the
Chemical Engineering toolkit. Proper knowledge of how to
manipulate the equations for control of the CSTR is tantamount to
the successful operation and production of desired products.
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Assumptions
Perfect mixing
The agitator within the CSTR will create an environment of perfect mixing
within the vessel. Exit stream will have same concentration and temperature
as reactor fluid.
Single, 1st order reaction
To avoid confusion, complex kinetics are not considered in the following
modeling.
Parameters specified
We assume that the necessary parameters to solve the problem have been
specified.
Volume specified
In a control environment, the size of the vessel is usually already specified.
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Mass Balance
From our energy and material balances coursework, we know that
the general equation for a mass balance in any system is as follows:
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Energy Balance
From our thermodynamics coursework, we know that the general
equation for an energy balance in any system is as follows:
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You are contracted by DTK Chemical to control the operationof their 3000 L jacketed CSTR. They desire to create chemicalB from chemical A at an optimal conversion. What is the
temperature at which the optimal conversion is achieved?
Some information about the process:
A B is a first order, irreversible reaction.
Feed stream temperature = 400 K
Coolant temperature = 350 K
Heat of reaction = -200 J/mol
Inlet concentration of A = 9 mol/L
Inlet flow rate = 4 kg/s
Density of A = 1000 g/L
UA of the heat exchanger = 7 kcal/s
Rate constant = 1.97x1020 s-1
Activation energy = 166 kJ/mol
Overall change in Heat capacity = 1 kcal/kg-K.
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https://controls.engin.umich.edu/wiki/index.php/File:CSTRforExample1.jpg -
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Steps for Modeling CSTR Heat Exchange Problem :
From CSTR Heat Exchange problem given, we usedPowersim Studio Enterprise 2005 for modeling.
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Mass Balances
Energy Balances
Eulers Methods
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Change Model into PowerSIM Studio Enterprise 2005
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No Variable Values Units1 CAO 9 Mol/L
2 CAO, 2 9 Mol/L
3 t For CAO, 2 s
4 t 1 s
5 Cp 1000 J/Kg.K
6 E 166000 J/mol
7 M 4 Kg/s
8 k0 1.97E+20 S-1
9 UA 7000 J/s
10 T0 400 K
11 T0, 2 400 K12 t for T0 s
13 Tc 350 K
14 Tc , 2 350 K
15 V 3000 L
16 1 Kg/L
17 HRx -200 J/mol
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Modeling using Powersim Studio Enterprise 2005
CSTR HEAT
EXCHANGE MODEL
CA
T
C rate in
T rate in
C rate out
m rho CA0 k0 gE
Delta Cp T0 Cp Delta Hrxn
V
T rate out
UATCT rate cooler
R
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12:00 AM 12:20 AM 12:40 AM 1:00 AM1
2
3
4
5
6
7
8
9
mol/l
CA
CA vs Time
Result from Modeling is shown graph
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12:00 AM 12:20 AM 12:40 AM 1:00 AM
360
370
380
390
400
K
T
T vs Time
Result from Modeling is shown graph
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The Result is Shown in Table Below
Time CA (mol/l) T (K)
12:00 AM
12:20 AM
12:40 AM
1:00 AM
1:20 AM
1:40 AM2:00 AM
9.00
5.14
6.18
6.29
6.31
6.316.31
400.00
368.76
368.38
368.38
368.38
368.38368.38
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From using Powesim Studio Enterprise 2005,we see that the optimal conversion occurs at 368.38 K.
This comes from inputting all of the given information
from the problem statement into the Powersim sheet,and then reading off the value for the optimal
temperature.