cstr series
TRANSCRIPT
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
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.
2
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.
3
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
4
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
5
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.
6
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
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.
8
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
9
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
)
10
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.
11
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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