Sistem Dinamika

7/31/2019 Sistem Dinamika

1/16

SISTEM DINAMIK

CSTR HEAT EXCHANGE MODEL

Disusun Oleh :


2/16

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.


3/16

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.


4/16

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:


5/16

Energy Balance

From our thermodynamics coursework, we know that the general

equation for an energy balance in any system is as follows:


6/16

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.


7/16
https://controls.engin.umich.edu/wiki/index.php/File:CSTRforExample1.jpg


8/16

Steps for Modeling CSTR Heat Exchange Problem :

From CSTR Heat Exchange problem given, we usedPowersim Studio Enterprise 2005 for modeling.


9/16

Mass Balances

Energy Balances

Eulers Methods


10/16

Change Model into PowerSIM Studio Enterprise 2005


11/16

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


12/16

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


13/16

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


14/16

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


15/16

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


16/16

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.

Documents

Sistem Dinamika