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UNIVERSITI TEKNOLOGI MARAFAKULTI KEJURUTERAAN KIMIA
CHEMICAL ENGINEERING LABORATORY III(CHE574)
No. Title Allocated Marks (%) Marks
1 Abstract/Summary 5
2 Introduction 5
3 Aims 5
4 Theory 5
5 Apparatus 5
6 Methodology/Procedure 10
7 Results 10
8 Calculations 10
9 Discussion 20
10 Conclusion 5
11 Recommendations 5
12 Reference / Appendix 5
13 Supervisor’s grading 10
TOTAL MARKS 100
Checked by :
Date :
NAME AND STUDENT NO : NUR SYAFIQAH BINTI FADALY (2012662222)GROUP : EH 220 4AEXPERIMENT : TUBULAR FLOW REACTOR (BP 101-B) DATE PERFORMED : 6/05/2014SEMESTER : 4PROGRAMME / CODE : CHE 574SUBMIT TO : DR JEFRI JAAPAR
TABLE OF CONTENT
Page
1 ABSTRACT 3
2 INTRODUCTION 4
3 OBJECTIVE 5
4 THEORY 5
5 APPARATUS 6
6 PROCEDURE 7
7 RESULT AND CALCULATION 9
8 DISCUSSION 21
9 CONCLUSION 22
10 RECOMMENDATION 22
11 REFERENCES 23
12 APPENDICES
2
1 ABSTRACT
This experiment has been conducted on 6th May 2014. The experiment is conducted to
achieve the objective that has been considered which is to examine the effect of pulse input and
step change input in tubular flow reactor and to construct the residence time distribution function
by using tubular machine. Based on the experiment, two experiment were conducted which is
pulse input experiment and step change input experiment. In the pulse input experiment, the flow
rate was set up at 700 m3s-1 and let it for one minute before reading taken every 30 seconds until
the conductivity reading is 0.0. In the other hand, the step change input experiment, the
conductivity were observe every 30 seconds until the reading at Q2 is constant.
3
2 INTRODUCTION
A tubular reactor is a vessel through which flow is continuous, usually at steady state,
and configured so that conversion of the chemicals and other dependent variables are functions
of position within the reactor rather than of time. Flow in tubular reactors can be laminar , as
with viscous fluids in small-diameter tubes, and greatly deviate from ideal plug-flow behavior, or
turbulent, as with gases.
In an ideal plug flow reactor, a pulse of tracer injected at the inlet would not undergo any
dispersion as it passed through the reactor and would appear as a pulse at the outlet. The degree
of dispersion that occurs in a real reactor can be assessed by following the concentration of tracer
versus time at the exit. This procedure is called the stimulus-response technique.
High temperature reactions Residence Time Distribution (RTD) analysis is a very
efficient diagnosis tool that can be used to inspect the malfunction of chemical reactors.
Residence time distributions are measured by introducing a non-reactive tracer into the system at
the inlet. The concentration of the tracer is changed according to a known function and the
response is found by measuring the concentration of the tracer at the outlet. The selected tracer
should not modify the physical characteristics of the fluid (equal density, equal viscosity) and the
introduction of the tracer should not modify the hydrodynamic conditions. In general, the change
in tracer concentration will either be a pulse or a step.
The residence time distribution of a real reactor deviated from that of an ideal reactor,
depending on the hydrodynamics within the vessel. A non-zero variance indicates that there is
some dispersion along the path of the fluid, which may be attributed to turbulence, a non-
uniform velocity profile, or diffusion. If the mean of the curve arrives earlier than the
expected time it indicates that there is stagnant fluid within the vessel. If the residence time
distribution curve shows more than one main peak it may indicate channeling, parallel paths to
the exit, or strong internal circulation.
4
3 OBJECTIVE
To examine the effect of a pulse input and step change input in a tubular flow reactor.
To construct a residence time distribution (RTD) function for the tubular flow reactor
4 THEORY
A tubular reactor is a vessel through which flow is continuous, usually at steady state,
and configured so that conversion of the chemicals and other dependent variables are functions
of position within the reactor rather than of time. In the ideal tubular reactor, the fluids flow as
if they were solid plugs or pistons, and reaction time is the same for all flowing material at any
given tube cross section. Tubular reactors resemble batch reactors in providing initially high
driving forces, which diminish as the reactions progress down the tubes. Tubular reactor are
often used when continuous operation is required but without back-mixing of products and
reactants.
Flow in tubular reactors can be laminar, as with viscous fluids in small-diameter tubes,
and greatly deviate from ideal plug-flow behavior, or turbulent, as with gases .Turbulent flow
generally is preferred to laminar flow, because mixing and heat transfer are improved. For slow
reactions and especially in small laboratory and pilot-plant reactors, establishing turbulent flow
can result in inconveniently long reactors or may require unacceptably high feed rates.
Tubular reactor is specially designed to allow detailed study of important process. The
tubular reactor is one of three reactor types which are interchangeable on the reactor service unit.
the reactions are monitored by conductivity probe as the conductivity of the solution changes
with conversion of the reactant to product. This means that the inaccurate and inconvenient
process of titration, which was formally used to monitor the reaction progress, is no longer
necessary.
5
The residence-time of an element of fluid leaving a reactor is the length of time spent by
that element within the reactor. For a tubular reactor, under plug-flow conditions, the residence-
time is the same for all elements of the effluent fluid. (K. G. Denbigh) The procedure would be
to carry out experiments with tubular reactor at varying feed rates, measuring the extent of
reaction of the stream leaving the reactor. One possible method might to add ‘inert’ gas to the
acetaldehyde vapor in such quantity that the change in density between entry and exit of the
reactor could be neglected. In that case, the batch reactor time and the residence-time would both
be equal to the space-time.
5 APPARATUS
1. Tubular flow reactor (BP 101-B)2. Deionized water3. 0.025M sodium chloride, NaCl4. Ethyl acetate
6
6 PROCEDURE
6.1 General start-up procedures
1. All valves are initially closed except valve V7.
2. 20 liter of 0.025M sodium chloride, NaCl is prepared.
3. The feed tank B2 is filled with the NaCl solution.
4. The power is turned on for the control panel.
5. The water de-ionizer is connected to the laboratory water supply. Valve V3 is opened and
feed tank B1 is filled with the deionized water. Valve V3 is closed.
6. Valves V2 and V10 are opened. Pump P1 is switched on. P1 flow controller is adjusted to
obtain a flow rate of approximately 700 mL/min at flow meter F1-01. The conductivity
display is observed at low value then valve V10 is closed and pump P1 is switched off.
7. Valves V5 and V12 are switched on. Pump P2 is switched on. P2 flow controller is
adjusted to obtain a flow rate of approximately 700 mL/min at flow meter F1-02. Valves
V12 is closed and pump P2 is switched off.
6.2 Experiment 1: Pulse input in a tubular flow reactor
1. The general start-up procedure is performed.
2. Valve V9 is opened and pump P1 is switch on.
3. Pump P1 flow controller is adjusted to give a constant flow rate of de-ionized water into
the reactor R1 at approximately 700 ml/min at Fl-01.
4. Let the de-ionized water to continue flowing through the reactor until the inlet (Ql-01)
and outlet (Ql-02) conductivity values are stable at low levels. Both conductivities values
are recorded.
5. Valve V9 is closed and pump P1 is switch off.
6. Valve V11 is opened and Pump P2 is switch on. The timer is started simultaneously.
7. Pump P2 flow controller is adjusted to give a constant flow rate of salt solution into the
reactor R1 at 700 ml/min at Fl-02.
7
8. Let the salt solution to flow for 1 minute, then reset and restart the timer. This will start
the time at the average pulse input.
9. Valve V11 is closed and pump P2 is switch off. Then, open valve V9 quickly and
pumpP1 is switch on.
10. Make sure that the de-ionized water flow rate is always maintained at 700 ml/min by
adjusting P1 flow controller.
11. Both the inlet (Ql-01) and outlet (Ql-02) conductivity a value at regular intervals of
30seconds is start recorded.
12. The conductivity values is continue recording until all readings are almost constant and
approach the stable low level values.
6.3 Experiment 2: Step change input in a tubular flow reactor
1. The general start-up procedure is performed.
2. Valve V9 is opened and pump P1 is switch on.
3. Pump P1 flow controller is adjusted to give a constant flow rate of de-ionized water into
the reactor R1 at approximately 700 ml/min at Fl-01.
4. Let the de-ionized water to continue flowing through the reactor until the inlet (Ql-01)
and outlet (Ql-02) conductivity values are stable at low levels. Both conductivities values
are recorded.
5. Valve V9 is closed and pump P1 is switch off.
6. Valve V11 is opened and Pump P2 is switch on. The timer is started simultaneously.
7. Both the inlet (Ql-01) and outlet (Ql-02) conductivity a value at regular intervals of
30seconds is start recorded.
8
8. The conductivity values is continue recording until all readings are almost constant.
7 RESULT AND CALCULATION
Experiment 1: Pulse Input in a Tubular Flow Reactor
Flow rate = 700 mL/min (De-ionized water)
Time (min) Conductivity(mS/cm)
Inlet Outlet
0.0 0.0 0.0
0.5 0.3 0.0
1.0 0.0 0.8
1.5 0.0 1.9
2.0 0.0 1.1
2.5 0.0 0.2
3.0 0.0 0.0
3.5 0.0 0.0
9
0 0.5 1 1.5 2 2.5 3 3.5 40
0.20.40.60.81
1.21.41.61.82
Oulet Conductivity (mS/cm) VS Time (min)
Time (min)
Oul
et C
ondu
ctivi
ty (m
S/cm
)
∫0
∞
C ( t ) dt= Area under the graph
Area = (t 1-t 2) [ f (t1 )+ f (t 2)2 ]
For time (0.5-1.0) minutes
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (1.0– 0.5)[ 0+0.8
2 ]= 0.1 g .min ¿m3
For time (1.0 – 1.5) minutes
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (1.5– 1.0)[ 0.8+1.9
2 ]= 0.675 g .min ¿m3
For time (1.5 – 2.0) minutes
10
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (2.0– 1.5)[ 1.9+1.1
2 ]= 0.75g .min ¿m3
For time (2.0 – 2.5) minutes
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (2.5– 2.0)[ 1.1+0.2
2 ]= 0.325 g .min ¿m3
For time (2.5 – 3.0) minutes
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (3.0– 2.5)[ 0.2+0.0
2 ]= 0.005 g .min ¿m3
So the total area or ∫0
4
C ( t ) dt= ( 0.1+ 0.675 + 0.75 + 0.325 + 0.005) = 1.855
g.min/m3
E ( t )= C( t)
∫0
∞
C (t )dt
For t = 0, C(t) = 0.0
E( t)=0 /1.855=0
For t = 0.5, C(t) = 0.0
E( t)=0 /1.855=0
For t = 1.0, C(t) = 0.8
E( t)=0.8 /1.855=0.431267
11
For t = 1.5, C(t) = 1.9
E( t)=1.9/1.855=1.02425
For t = 2.0, C(t) = 1.1
E( t)=1.1/1.855=0.59299
For t = 2.5, C(t) = 0.2
E( t)=0.2/1.855=0.1078167
For t = 3.0, C(t) = 0.0
E( t)=0 /1.855=0
For t = 3.5, C(t) = 0.0
E( t)=0 /1.855=0
Time(min) Conductivity Oulet E(t)
0.0 0.0 0.0
0.5 0.0 0.0
1.0 0.8 0.4313
1.5 1.9 1.0242
2.0 1.1 0.5930
2.5 0.2 0.1078
3.0 0.0 0.0
3.5 0.0 0.0
Residence time distribution (RTD) function for plug flow reactor
12
0 0.5 1 1.5 2 2.5 3 3.5 40
0.2
0.4
0.6
0.8
1
1.2
E(t) VS Time(min)
Time(min)
E(t)
For time (0 – 0.5)minutes = 0
For time (0.5 -1.0)minutes
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (1– 0.5)[ 0.4313
2 ]= 0.107825
For time (1 – 1.5) minutes
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (1.5– 1)[ 0.4313+1.0242
2 ] = 0.363875
For time (1.5 – 2.0 )minutes
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (2 – 1.5)[ 1.0242+0.593
2 ] = 0.4043
For time (2.0 – 2.5) minutes
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (2.5 – 2)[ 0.593+0.1078
2 ]= 0.1752
For time (2.5 -3.0) minutes
Area = (t 2−t 1¿[ E (t1+t 2 )2 ] = (3– 2.5)[ 0.1078
2 ]=0.02695
13
For time (3 -3.5) minutes = 0
∫0
∞
E ( t ) dt= Total area under the graph = (0.107825 + 0.363875 + 0.4043 +
0.1752 + 0.02695 ) =1.07815
Residence time ,tm=¿ ∫0
∞
tE ( t )dt= 3.5(1.07815)= 3.773525
Time(min) Oulet Conductivity (mS/cm)
E(t) tE(t) (t-tm)2E(t)dt
(t-tm)3E(t)dt
0.0 0.0 0.0 0.0 0.0 0.0
0.5 0.0 0.0 0.0 0.0 0.0
1.0 0.8 0.4313 0.4313 3.3177 -9.2019
1.5 1.9 1.0242 1.5363 5.2940 -12.0360
2.0 1.1 0.5930 1.1860 1.8652 -3.3080
2.5 0.2 0.1078 0.2695 0.1748 -0.2227
3.0 0.0 0.0 0.0 0.0 0.0
3.5 0.0 0.0 0.0 0.0 0.0
∑ =2.1563 =3.4231 =10.6517 =-25.0926
Mean residence time, tm=¿ ∫0
∞
tE ( t )dt=¿3.4231
Second moment, variance ,σ 2 = ∫0
∞
(t−tm)2 E(t) dt
= 10.6517
14
Third moment, skewness, s3= 1
σ32 ∫
0
∞
(t−tm)3E(t) dt
=1
(3.2637)32 ¿-25.0926) = -4.2558
Experiment 2: Step Change Input in a Tubular Flow Reactor
Flow rate = 700 mL/min (De-ionized water)
Time (min) Conductivity(mS/cm)
Inlet Outlet
0.0 0.0 0.0
0.5 3.7 0.0
1.0 4.0 0.0
1.5 4.2 0.0
2.0 4.2 0.0
2.5 4.2 1.0
3.0 4.2 2.3
3.5 4.3 2.6
4.0 4.2 2.6
4.5 4.3 2.6
15
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
0.5
1
1.5
2
2.5
3
Oulet Conductivity (mS/cm) VS Time (min)
time (min)
Oul
et C
ondu
ctivi
ty (m
S/cm
)
Calculation
∫0
∞
C (t ) dt= Area under the graph
Area = (t 1-t 2) [ f (t1 )+ f (t 2)2 ]
For time (0.5-1.0) – (1.5-2.0) minutes
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (1.0– 0.5)[ 0+0.0
2 ]= 0 g .min ¿m3
For time (2.0 – 2.5) minutes
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (2.5– 2.0)[ 0+1
2 ]= 0.25 g .min ¿m3
For time (2.5 – 3.0) minutes
16
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (3.0– 2.5)[ 1.0+2.3
2 ]= 0.825 g .min ¿m3
For time (3.0 – 3.5) minutes
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (3.5– 3.0)[ 2.3+2.6
2 ]= 1.225 g .min ¿m3
For time (3.5 – 4.0) minutes
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (4.0– 3.5)[ 2.6+2.6
2 ]= 1.3 g .min ¿m3
For time (4.0 – 4.5) minutes
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (4.5– 4.0)[ 2.6+2.6
2 ]= 1.3 g .min ¿m3
So the total area or ∫0
4
C ( t ) dt= ( 0.25 + 0.825 + 1.225 + 1.3)) = 4.9 g.min/m3
E ( t )= C( t)
∫0
∞
C (t )dtFor t = 0, C(t) = 0.0
E( t)=0 /4.9=0
For t = 0.5, C(t) = 0.0
E( t)=0 /4.9=0
For t = 1.0, C(t) = 0.0
E( t)=0 /4.9=0
17
For t = 1.5, C(t) = 0
E( t)=0 /4.9=0
For t = 2.0, C(t) = 0
E( t)=0 /4.9=0
For t = 2.5, C(t) = 1.0
E( t)=1.0/ 4.9=0.204
For t = 3.0, C(t) = 2.3
E( t)=2.3 /4.9=0.469
For t = 3.5,4.0,4.5 C(t) = 2.6
E( t)=2.6 /4.9=0.5306
Time(min) Conductivity Oulet E(t)
0.0 0.0 0.0
0.5 0.0 0.0
1.0 0.0 0.0
1.5 0.0 0.0
2.0 0.0 0.0
2.5 1.0 0.204
3.0 2.3 0.469
18
3.5 2.6 0.5306
4.0 2.6 0.5306
4.5 2.6 0.5306
Residence time distribution (RTD) function for plug flow reactor
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
0.1
0.2
0.3
0.4
0.5
0.6
Y-Values
Time (min)
E(t)
For time (0 – 0.5) – (1.5-2.0) = 0
For time (2.0 – 2.5) minutes
Area = (t 2−t 1¿[ E(t 1+ t2)2 ] = (2.5 – 2)[ 0+0.204
2 ]= 0.051
For time (2.5 -3.0) minutes
Area = (t 2−t 1¿[ E (t1+t 2 )2 ] = (3– 2.5)[ 0.204+0.469
2 ]=0.16825
For time (3 -3.5) minutes
19
Area = (t 2−t 1¿[ E (t1+t 2 )2 ] = (3.5– 3)[ 0.469+0.5306
2 ]=0.2499
For time (3.4-4.0) & (4.0-4.5) minutes
Area = (t 2−t 1¿[ E (t1+t 2 )2 ] = (4.0-3.5)[ 0.5306+0.5306
2 ]=0.2653
∫0
∞
E ( t ) dt= Total area under the graph =
(0.2653+0.2653+0.2499+0.16825+0.051) =0.99975
Residence time ,tm=¿ ∫0
∞
tE ( t )dt= 4.5(0.99975)= 4.498875
Time(min) Oulet Conductivity (mS/cm)
E(t) tE(t) (t-tm)2E(t)dt
(t-tm)3E(t)dt
0.0 0.0 0.0 0.0 0.0 0.0
0.5 0.0 0.0 0.0 0.0 0.0
1.0 0.0 0.0 0.0 0.0 0.0
1.5 0.0 0.0 0.0 0.0 0.0
2.0 0.0 0.0 0.0 0.0 0.0
2.5 1.0 0.204 0.51 0.2038 -0.4073
3.0 2.3 0.469 1.407 0.378 -0.5666
3.5 2.6 0.5306 1.8571 0.2493 -0.249
4.0 2.6 0.5306 2.1224 0.066 -0.0652
4.5 2.6 0.5306 2.3877 0.00358 3.77 x 10-10
∑ 11.1 0.99975 8.2842 0.90068 -1.321
20
Mean residence time, tm=¿ ∫0
∞
tE ( t )dt=¿8.2842
Second moment, variance ,σ 2 = ∫0
∞
(t−tm)2 E(t) dt
= 0.90068
Third moment, skewness, s3= 1
σ32 ∫
0
∞
(t−tm)3E(t) dt
=1
(0.949)32 ¿-1.321) = -1.4289
8 DISCUSSION
Firstly, the objectives that need to be achieve for this tubular reactor experiment is to
examine the effect of a pulse input and step change in a tubular reactor and also to construct the
residence time distribution (RTD) function for the tubular flow reactor at the end of the
experiment. The experiment was run at the 700 mL/min of flow rate. While the experiment is
running, the conductivity for the inlet and outlet of the solution had been recorded at the period
of time where until the conductivity of the solution is constant. For a tubular reactor, the flow
that through the vessel is continuous, usually at the steady state and also configured thus the
conversion of the chemicals and other dependent variables are functions of position within the
reactor rather than of time.
For this experiment, we are examined the effects of flow for two types of reaction which
are in pulse input and step change. The flow rate of solution is kept constant at 700ml/min. For
these types of experiments, the graph of outlet conductivity versus times had been plotted. Based
on graph of pulse input, the outlet conductivity that had been plotted is 1.9 mS/cm at time of 1.5
minutes which are the highest value. After that, the conductivity decreases within the time and
comes to be constant at the time of 3 minutes. From the result, it showed that it results was not
21
differ from the theory that recorded that the conductivity is reaching zero at time of 4 minutes.
Thus, the experiment 1 is a success.
In addition, for the graph of step change the outlet conductivity is increase within the
time by started at time of 2.5 minutes which it inlet conductivity is 4.2 mS/min and then
undergoes some increment until at minutes 4.0 which the outlet conductivity is 2.6 mS/min.
There are differences between both of the graph where the outlet conductivity for step change is
increase smoothly compare to pulse input where the outlet conductivity is increase at the same
period of times and then it became decrease into the constant value.
Next experiment, to construct the residence time distribution (RTD) function for the
tubular flow reactor for pulse input and also step change. The residence time distribution is
plotted based on exit time (E(t)) versus time from the data that had been recorded in the table. From the graph,
it can be concluded that the residence time distribution is depends on the outlet conductivity.
9 CONCLUSION
From the experiment, we able to examine the effect of the pulse input and step change in
a tubular flow reactor and we also can differentiate both of the effect. Besides, we also able to
construct the residence time distribution (RTD) function for the tubular flow reactor. The
conductivity for inlet and outlet after 3 minutes for pulse input are both 0.00 mS/ while for the
step change is 4.2 mS/min and 2.3 mS/min respectively. The distribution of exit time, E(t) is
calculated for each 30 second until 4 minutes interval. The graphs for both pulse input and step
change experiments are plotted.
RECOMMENDATION
There are a few recommendations during conducting this experiment. First, all valves
should be properly placed before the experiment started. Secondly, the volume of sample
collected must be accurate throughout the experiment to avoid error during calculation. Next,
22
the flow rates should be constantly monitored so that it remains constant throughout the
experiment. Titration should be conducted carefully. It should be immediately stopped when
the indicator turned light pink. Titration should be repeat if the solution turns dark pink.
11 REFERENCES
Levenspiel O., “Chemical Reaction Engineering”, John Wiley (USA), 1972
Fogler H.S., “Elements of Chemical Reaction Engineering, 3rd Ed.”, Prentice Hall (USA), 1999
Astarita G., “Mass Transfer with Chemical Reaction”, Elsevier, 1967
23