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TABLE OF CONTENT 1 CONTENT PAGE ABSTRACT / SUMMARY 2 INTRODUCTION 3 AIMS / OBJECTIVE 4 THEORY 4 – 7 PROCEDURE 8 APPARATUS 9 RESULTS 9 – 10 CALCULATION - DISCUSSION 11 CONCLUSION 11 RECOMMENDATION 12 REFERENCES 12 APPENDICES 13

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Page 1: cstr series

TABLE OF CONTENT

1

CONTENT PAGE

ABSTRACT / SUMMARY 2

INTRODUCTION 3

AIMS / OBJECTIVE 4

THEORY 4 – 7

PROCEDURE 8

APPARATUS 9

RESULTS 9 – 10

CALCULATION -

DISCUSSION 11

CONCLUSION 11

RECOMMENDATION 12

REFERENCES 12

APPENDICES 13

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ABSTRACT / SUMMARY

In this experiment, a continuous stirred tank reactor ( CSTR ) in series are used to determine

the concentration response to a step change and pulse input and also to determine the effect of

residence time on the response curve.

Firstly the deionised water are filled in the both two tanks with the sodium chloride are being

diluted in the tank one. Than the deionised water from the tank two are flow through to fill up

the three reactors. The flow rates of the deionised water were set up to 150 mL/min to prevent

the overflow of the deionised water in the reactors. After 10 minutes the initial readings of the

conductivity were taken after the reading are stable. After that, the diluted sodium chloride

was flow through the tank after the valve was set up to position 2. The readings of the

conductivity are taken for every 3 minutes by the programme set up in the computer. The

readings were recorded until the conductivity was closed to each other for every reactor. The

graph of the conductivity versus time was plotted. From the graph we can determine the effect

of the step change and pulse input to the concentration.

But during the experiment, there were not enough time to run experiment B to determine the

concentration response to the pulse input. Therefore only experiment A was conducted.

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INTRODUCTION

In the majority of industrial chemical process, a reactor is the key item of equipment in which

raw materials undergo a chemical change to form desired product. The design and operation

of chemical reactors is thus crucial to the whole success of the industrial operation.

Reactors can widely form, depending on the nature of the feed materials and the products.

Understanding non-steady behavior of process equipment is necessary for design and

operation of automatic control systems. One particular type of process equipment is the

continuous stirred tank reactor. In this reactor, it is important to determine the system

response to a change in concentration. This response of concentration versus time is an

indication of the ideality of the system.

The Armfield Stirred Tank Reactors in Series unit is designed to follow the dynamics of the

perfectly mixed multi-stage process. Dynamic behaviour can be studied as can multi-stage

chemical reaction. Bench mounted and self-contained, the unit requires only to be connected

to a single phase electrical supply for operation. A self-contained bench mounted small scale

unit fitted with three continuous stirred reactors in series which are fed from two 5 litre tanks.

Each reactor is fitted with a conductivity probe.

There are three reactor vessels connected in series, each containing a propellor agitator driven

by a variable speed electric motor. Two reagent vessels and two variable speed feed pumps

feed reagents into the first reactor in line. For certain experiments the feed can be connected

to the third reactor and a dead-time coil, also positioned on the vacuum formed plinth. Each

reactor and the exit port of the dead-time coil are fitted with accurate conductivity probes for

monitoring the process.

Conductivity is displayed on a digital meter on the console through a selector switch and all

four probes can be connected to the optional Armfield data logging accessory CEX-304IFD.

A dead-time residence coil can also be attached to the exit of the last reactor in the series.

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AIMS / OBJECTIVES

1. To determine the concentration response to a step change.

2. To determine the concentration response to a pulse input.

THEORY

General Mole Balance Equation

Assumptions

1) Steady state therefore

2) Well mixed therefore rA is the same throughout the reactor

Rearranging the generation

In terms of conversion

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Reactors in Series

Given -rA as a function of conversion, , -rA = f(X), one can also design any sequence of reactors in series provided there are no side streams by defining the overall conversion at any point.

Mole Balance on Reactor 1

Mole Balance on Reactor 2

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Given -rA = f(X) the Levenspiel Plot can be used to find the reactor volume

Tracer Analysis on the Transient Behaviors of Continuous Stirred-Tank in Series.

Unlike the above, the tracer analysis will help to understand the transient behaviors of

the continuous stirred tank reactor in series by having a step input or pulse of tracer

component such as salts. The conductivity measurement will indicate the progression of the

tracer throughout the stirred tank in series.

CO

C1 C2

C3

Figure 5

Effect of Step Change In Input Concentration to the Concentration of Solute In Stirred Tank

Reactors In Series

When a step change of solute concentration is introduced at the feed of tank 1, the tank in

series will experience a transient behaviour as of Figure 8 below. The response will be

dependent on the residence time of each reactor in series.

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Concentration Concentration

Time Time

Effect of Pulse in Input Concentration to the Concentration of solute in Stirred Tank in Series

When a pulse input of solute concentration is introduced at the feed of tank 1, the transient

behaviour will be different than the step change input due to the diminishing concentration

from the input after pulsing.

Concentration Concentration

Time Time

7

Reactor 1

Reacto 2

Reactor 3

Reactor 1

Reactor 2

Reactor 3

Figure 7b: Transient response of

tank in series to the step input.

Figure 7a: Step change input.

Figure 8b: Transient response of

tank in series to the pulse input

Figure 8a: Pulse Input

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PROCEDURE

Experiment 1: The Effect of Step Change Input

In this experiment a step-change input would be introduced and the progression of the tracer

will be monitored via the conductivity measurements in all the three reactors.

1. Tank 1 and tank 2 was filled up with 20 L feeds deionizer water.

2. 300g of Sodium Chloride was dissolved in tank 1until the salts dissolve entirely and

the solution is homogenous.

3. Three way valve (V3) was set to position 2 so that deionizer water from tank 2 will

flow into reactor 1.

4. Pump 2 was switched on to fill up all three reactors with deionizer water.

5. The flow rate (Fl1) was set to 150 ml/min by adjusting the needles valve (V4). Do not

use too high flow rate to avoid the over flow and make sure no air bubbles trapped in

the piping. The stirrers 1, 2 and 3 were switched on.

6. The deionizer water was continued pumped for about 10 minute until the conductivity

readings for all three reactors were stable at low values.

7. The values of conductivity were recorded at t0.

8. The pump 2 was switched off after 5 minutes. The valve (V3) was switched to

position 1 and the pump 1 was switched on. The timer was started.

9. The conductivity values for each reactor were recorded every three minutes.

10. Record the conductivity values were continued until reading for reactor 3 closed to

reactor 1.

11. Pump 2 was switched off and the valve (V4) was closed.

12. All liquids in reactors were drained by opening valves V5 and V6.

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APPARATUS

1. Distillation water

2. Sodium Chloride

3. Continuous reactor in series

4. Stirrer system

5. Feed tanks

6. Waste tank

7. Dead time coil

8. Computerize system

9. Stop watch

RESULTS

To pump 2 : QT 1 = 0.1067 QT 2 = 0.1527 QT 3 = 0.1970

Pump 1

FT = 146.5 mL/min TT 1 = 27.0 OC TT 2 = 26.8 OC TT 3 = -32768.0 OC

Time ( min ) QT 1 QT 2 QT 3

0.0 7.7719 1.2739 0.1793

3.0 11.5004 4.0231 0.6426

6.0 12.9816 6.4715 2.2078

9.0 15.4442 8.9308 3.5687

12.0 16.2334 10.9438 5.8778

15.0 17.0967 12.9659 7.3891

18.1 16.9719 14.3561 9.4644

21.0 17.9182 15.2452 10.8577

24.0 18.0460 15.9972 12.5270

27.3 18.1791 16.6403 13.4500

30.0 18.3528 17.2690 14.4642

33.0 18.3725 17.7711 15.1951

36.0 18.3405 17.8413 15.9128

39.0 18.4571 17.7821 16.4161

42.0 18.3813 17.8184 16.7385

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45.0 18.5741 18.1963 17.0200

48.2 18.3229 18.2163 17.2865

51.5 18.6512 18.1130 17.5490

54.0 18.6701 18.1007 17.3895

57.0 18.5045 18.1445 17.7519

60.0 18.6446 18.3991 17.8575

63.0 18.6980 18.3931 17.8899

66.0 18.6720 18.2124 17.7821

69.3 18.7292 18.3855 17.8241

72.0 18.6759 18.3532 18.0746

75.0 18.6205 18.6024 18.1296

0 10 20 30 40 50 60 70 800

2

4

6

8

10

12

14

16

18

20

Conductivity ( mS/cm ) vs. Time ( min )

QT 1QT 2QT 3

Time ( min )

Cond

uctiv

ity (m

S/cm

)

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DISCUSSION

From the conducted experiment, the conductivity versus time graph was plotted as shown

above. From the graph we are going to determine the effect of the step change to the

concentration. From the graph we can see that the concentration in the reactor 1 are higher at

the initial compared to the reactors 2 and reactors 3. This is because the diluted sodium

chloride enters the reactor 1 first and then reactor 2 bypass with the deionised water

containing from the deionised water flow into the reactors. That is why the concentration of

decreased as the diluted sodium chloride flow bypass through reactor 1 to reactor 3 because of

the deionised water still containing in the reactors as it was not fully removed in the third

reactor.

As the time increased, the concentration of the three reactors almost become constant, that is

at the 75 minutes after the valve was switched to position 2 that is at QT 1 is 18.6205, QT 2 is

18.6024 and also QT 3 is 18.1296. According to the graph, the concentration at reactor 1 that

is the inlet concentration of sodium chloride diluted were not constantly increased may be

because of the flow rate of the inlet that is not constant at 150 mL/min.

During the data was recorded, there were some problems occur to the computer that recorded

the data. The computer was stuck and thus it recorded not accurately for every 3 minutes.

Because of the data recorded are not accurate, the result also are affected and the graph are

not so smooth.

CONCLUSION

as the conclusion, we can say that a step change in input affected the concentration at the

reactor. It can be seen from the graph plotted to the theory that the graph is almost the same.

But because of the error during the data recorded, there are some different of the graph for all

reactors as it does not smooth compared to the theory. From the results, sometimes the time

recorded is less than 3 minutes and sometimes more than 3 minutes. So, it will affect the

readings. From the theory, we should get the nearly value of conductivity for the reactor 1 and

3. Therefore from the experiment conducted at 75 minutes, we got QT 1 = 18.6202 mS/cm

and QT 3 = 18.1296 mS/cm. So, we get the step change in input concentration to the

concentration of solute in stirrer reactor in series is proportional to the time.

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RECOMMENDATION

1. Make sure that there are no air bubbles in the piping.

2. Check the tank 1 and 2 before start the experiment to make sure that it full with

deionised water and sodium chloride to make sure that our experiment run properly.

3. Make sure that the reactor and turbine are cleaned properly. Flush the system with

deionised water until no trances of salt are detected.

4. When we are doing the experiment the program that used to record the data was not

function. This causes us a high error in reading the data. My recommendation is to

make sure better maintainers of the apparatus.

REFERENCES

1. http://www.solution.com.my/pdf/BP107(A4).pdf retrieved on 13 February 2011.

2. http://en.wikipedia.org/wiki/Chemical_reactor retrieved on 13 February 2011.

3. Elements of Chemical reaction Engineering, Fourth Edition H. Scott Fogler, Pearson

International Edition, 2006 Pearson Education, Inc.

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APPENDICES

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