Continuous Stirred Tank Reactor (Cstr) (2)
-
Upload
bedirtupak -
Category
Documents
-
view
5.617 -
download
11
Transcript of Continuous Stirred Tank Reactor (Cstr) (2)
UNIVERSITI TEKNOLOGI MARA
FAKULTI KEJURUTERAAN KIMA CHEMICAL ENGINEERING LABORATORY III
(CHE575)
NAME : RM SYIBLI MILASI B R MUHAMAD FAKIH
STUDENT NO. : 2004624828
EXPERIMENT : CONTINUOUS STIRRED TANK REACTOR (CSTR)
DATE PERFORMED : 17TH JANUARY 2006
SEMESTER :DISEMBER 2005 – APRIL 2006
PROGRAMME / CODE :Bachelor of Engineering (Hons.) in Chemical Engineering/ EH220
No. Title Allocated marks % Marks %
1 Abstract/Summary 5
2 Introduction 5
3 Aims/Objectives 5
4 Theory 5
5 Procedures 3
6 Apparatus 5
7 Results 20
8 Calculations 10
9 Discussions 20
10 Conclusions 10
11 Recommendations 5
12 References 5
13 Appendices 2 TOTAL 100
Remarks:
Checked by: Rechecked by:DR.RUZITAH
TABLE OF CONTENTS
PK.FKK.PPM.MANUAL MAKMAL CHE565
ABSTRACT/SUMMARY…………………………….….3
INTRODUCTION…………………………………..........4
OBJECTIVES……………………………………………4
THEORY……………………………………………......4-6
PROCEDURES………………………………………...7-8
APPARATUS…………………………………………….9
RESULTS……………………………………………10-15
SAMPLE OF CALCULATIONS………………………16
DISCUSSION……………………………………….17-18
CONCLUSION………………………………………….19
RECOMMENDATION………………………………….19
REFERENCES………………………………………….20
APPENDICES…………………………………………...20
Summary
Our experiment was to observe the order of the saponification reaction and also to
find the rate constant. At first we mix the Ethyl Acetate and Naoh with equal volume.
Then we start the experiment by mixing them using continuous stirred tank reactor. After
5 minutes we will take a sample of solution and mixed with HCL. Then we titrate it with
0.1M NaoH. The amount of Naoh been used in that titration was been taken in the result.
We repeat the same procedure for the next sample that been taken after 10, 15, 20 and 25
minutes.
For the second experiment we do the same procedure as the first but we increase
the temperature. We take 3 different temperatures that was 60°C, 45°C and 30 °C. When
the all the result has been taken, calculation was made and we plot a graph based on that
result. By the graph we can determine the rate of the reaction.
INTRODUCTION
Reactor is one of the most important parts in industrial sector. Reactor is
equipment that changes the raw material to the product that we want. A good reactor will
give a high production and economical. One of criteria to choose or to design a good
reactor is to know the effectiveness of the reactor itself. There a many types of reactor
depending on the nature of the feed materials and products. One of the most important we
need to know in the various chemical reaction was the rate of the reaction.
By studying the saponification reaction of ethyl acetate and sodium hydroxide to
form sodium acetate in a batch and in a continuous stirred tank reactor, we can evaluate
the rate data needed to design a production scale reactor.
A stirred tank reactor (STR) may be operated either as a batch reactor or as a
steady state flow reactor (CSTR). The key or main feature of this reactor is that mixing is
complete so that properties such as temperature and concentration of the reaction mixture
are uniform in all parts of the vessel. Material balance of a general chemical reaction
described below.The conservation principle requires that the mass of species A in an
element of reactor volume dV obeys the following statement:
(Rate of A into volume element) - (rate of A out of volume element) + (rate of A
produced within volume element) = (rate of A accumulated within vol. element)
OBJECTIVES
EXPERIMENT A: BATCH STIRRED TANK REACTOR EXPERIMENT
1. To determine the order saponification reaction.2. To determine the reaction rate constant.
EXPERIMENT B: EFFECT TEMPERATURE ON REACTION RATE CONSTANT
1. To determine the effect temperature on reaction rate constant, k for batch reaction.2. To determine the activation energy of saponification.
THEORY
IDEAL STIRRED-TANK REACTOR
A stirred-tank reactor (STR) may be operated either as a batch reactor or as a
steady-state flow reactor (better known as Continuous Stirred-Tank Reactor (CSTR)).
The key or main feature of this reactor is that mixing is complete so that properties such
as temperature and concentration of the reaction mixture are uniform in all parts of the
vessel. Material balance of a general chemical reaction is described below.
The conservation principle required that the mass of species A in an element of reactor
volume ∆V obeys the following statement:
Rate of
A
Rate of
A Rate of A Rate of A
into - out of + produced = Accumulated
volume volume
within
volume
within
volume
element element element Element
BATCH STIRRED-TANK REACTOR (BSTR)
In batch reactions, there are no feed or exit streams and therefore equation (1) can be
simplified into:
Rate of A Rate of A
produced = accumulated
within
volume
within
volume
element element
The rate of reaction of component A is defined as:
-rA = 1/V (dNA/dt) by reaction = [moles of A which appear by reaction]
[unit volume] [unit time]
By this definition, if A is a reaction product, the rate is positive; whereas if it is a reactant
which is consumed, the rate is negative.
Rearranging equation (3),
(-rA) V = NAO dXA
dt
Integrating equation (4) gives,
t = NAO ∫ dXA__
(-rA)V
where t is the time required to achieve a conversion XA for either isothermal or non-
isothermal operation.
CA
EFFECT OF TEMPERATURE ON RATE OF REACTION
As we increase the temperature the rate of reaction increases. This is because, if
we heat a substance, the particles move faster and so collide more frequently. That will
speed up the rate of reaction. Collisions between molecules will be more violent at higher
temperatures. The higher temperatures mean higher velocities. This means there will be
less time between collisions. The frequency of collisions will increase. The increased
number of collisions and the greater violence of collisions result in more effective
collisions. The rate for the reaction increases. Reaction rates are roughly doubled when
the temperature increases by 10 degrees Kelvin.
In any single homogenous reaction, temperature, composition and reaction rate
are uniquely related. They can be represented graphically in one of three ways as shown
in figure 8 below:
C r3
r2
r1
figure 8
1/-r
A
Area = t
T
PROCEDURES
EXPERIMENT A:
1. The overflow tube in the reactor is being adjusted to give a desired working
volume (2.5liters). The pump P1 was switched on to start on pumping 1.25 liters
of 0.1M ethyl acetate form the feed tank into reactor. The pump P1 stopped.
2. Then the pump P2 was switch on and starts to pump another 1.25 liters of the
0.1M NaOH into the reactor. When the 2.5 liters volume is reached, then the
pump P2 were being stopped. The stirrer then being switches on and the speed
was set in the mid range (180rpm). The time is being observed. The start time are
recorded.
3. 10ml of the 0.25M HCL were quickly measured in a flask.
4. After 1 minute of reaction, sampling valve V7 opened to collect 50ml sample.
10ml of the 0.25M HCL are immediately added into the sample. The HCL quench
the reaction between ethyl acetate and sodium hydroxide.
5. The mixture was titrated with the 0.1M NaOH to evaluate the amount of un-
reacted HCL. This had provided us with the information to determine the amount
NaOH in feed solution which has reacted.
EXPERIMENT B:
1. The overflow tube in the reactor is being adjusted to give a desired working
volume (2.5liters). The pump P1 was switched on to start on pumping 1.25 liters
of 0.05M ethyl acetate form the feed tank into reactor. The pump P1 stopped.
2. Then the pump P2 was switch on and starts to pump another 1.25 liters of the
0.05M NaOH into the reactor. The heater was switched on and the temperature
was set to be 30°c when the heater is fully immersed. The cooling water being
run. The pump P2 was being stopped when the 2.5 liters of volume are reached.
The stirrer then being switches on and the speed was set in the mid range
(180rpm). The time is being observed. The start time are recorded.
3. 10ml of the 0.25M HCL were quickly measured in a flask.
4. After 1 minute of reaction, sampling valve V7 opened to collect 50ml sample.
10ml of the 0.25M HCL are immediately added into the sample. The HCL quench
the reaction between ethyl acetate and sodium hydroxide.
5. The mixture was titrated with the 0.1M NaOH to evaluate the amount of un-
reacted HCL. This had provided us with the information to determine the amount
NaOH in feed solution which has reacted.
6. Steps 4 and 5 were repeated for reaction times of 5, 10, 15, 20 and 25.
7. The experiment was repeated for reaction temperatures 30°C, 35°C and 45°C.
8. The graph ln(CB/CA) vs. t and ln k vs. 1/T were plotted.
9. The activation energy was found from the ln k vs. 1/T graph.
APPARATUS
1. Continuous stirred tank reactor ( Model BP:100)
2. Stopwatch
3. Beaker
4. Pipet
5. Volumetric cylinder
6. Solution : 0.1 NaOH
0.1 Ethyl acetate
0.25 HCl
Sodium hydroxide
RESULTS
EXPERIMENT A
Tim
e(m
in)
Vol
ume
of ti
trat
ing
NaO
H(m
l)
Vol
ume
of q
uenc
hing
H
Cl u
nrea
cted
with
N
aOH
in S
ampl
e(m
l)
Vol
ume
of H
Cl
reac
ted
with
NaO
H in
S
ampl
e(m
l)
Mol
e of
HC
l rea
cted
w
ith N
aOH
in s
ampl
e
Mol
e of
NaO
H
unre
acte
d in
sam
ple
Con
cent
ratio
n of
N
aOH
unr
eact
ed w
ith
Eth
yl A
ceta
te(M
)
Ste
ady
Sta
te fr
actio
n co
nver
sion
of
NaO
H,X
a
Con
cent
ratio
n of
N
aOH
rea
cted
with
E
thyl
Ace
tate
(M)
Mol
e of
NaO
H
reac
ted
with
Eth
hyl
Ace
tate
in
Sam
ple(
ml)
Con
cetr
atio
n of
Eth
yl
Ace
tate
rea
cted
with
N
aOH
(M)
Con
cent
ratio
n of
E
thyl
Ace
tate
U
nrea
cted
(M)
1/C
a
1
14.2
5.68
4.32
1.08
1.08 0.
0216
0.78
4
0.07
84
3.92
0.07
84
0.02
16
46.2
963
5
17.7
4
7.09
6
2.90
4
0.72
6
0.72
6
0.01
452
0.85
48
0.08
548
4.27
4
0.08
548
0.01
452
68.8
7052
10 19.2
7.68
2.32
0.58
0.58 0.
0116
0.88
4
0.08
84
4.42
0.08
84
0.01
16
86.2
069
15 19.2
7.68
2.32
0.58
0.58 0.
0116
0.88
4
0.08
84
4.42
0.08
84
0.01
16
86.2
069
20 19.4
7.76
2.24
0.56
0.56 0.
0112
0.88
8
0.08
88
4.44
0.08
88
0.01
12
89.2
8571
25 19.5
7.8
2.2
0.55
0.55 0.
011
0.89
0.08
9
4.45
0.08
9
0.01
1
90.9
0909
EXPERIMENT B
Temperature = 30°C
Tim
e(m
in)
Vol
ume
of ti
trat
ing
NaO
H(m
l)
Vol
ume
of q
uenc
hing
H
Cl u
nrea
cted
with
N
aOH
in S
ampl
e(m
l)
Vol
ume
of H
Cl
reac
ted
with
NaO
H in
S
ampl
e(m
l)
Mol
e of
HC
l rea
cted
w
ith N
aOH
in s
ampl
e
Mol
e of
NaO
H
unre
acte
d in
sam
ple
Con
cent
ratio
n of
N
aOH
unr
eact
ed w
ith
Eth
yl A
ceta
te(M
)
Ste
ady
Sta
te fr
actio
n co
nver
sion
of
NaO
H,X
a
Con
cent
ratio
n of
N
aOH
rea
cted
with
E
thyl
Ace
tate
(M)
Mol
e of
NaO
H
reac
ted
with
Eth
hyl
Ace
tate
in
Sam
ple(
ml)
Con
cetr
atio
n of
Eth
yl
Ace
tate
rea
cted
with
N
aOH
(M)
Con
cent
ratio
n of
E
thyl
Ace
tate
U
nrea
cted
(M)
1/C
a
1 19 7.6
2.4
0.6
0.6 0.
012
0.88
0.08
8
4.4
0.08
8
0.01
2
83.3
3333
5
19.5
7.8
2.2
0.55
0.55 0.
011
0.89
0.08
9
4.45
0.08
9
0.01
1
90.9
0909
10 19.4
7.76
2.24
0.56
0.58 0.
0112
0.88
8
0.08
88
4.44
0.08
88
0.01
12
89.2
8571
15 19.3
7.72
2.28
0.57
0.57 0.
0114
0.88
6
0.08
86
4.43
0.08
86
0.01
14
87.7
193
20 19.5
7.8
2.2
0.55
0.55 0.
011
0.89
0.08
9
4.45
0.08
9
0.01
1
90.9
0909
25 19.8
7.92
2.08
0.52
0.52 0.
0104
0.89
6
0.08
96
4.48
0.08
96
0.01
04
96.1
5385
Temperature = 45°C
Tim
e(m
in)
Vol
ume
of ti
trat
ing
NaO
H(m
l)
Vol
ume
of q
uenc
hing
H
Cl u
nrea
cted
with
N
aOH
in S
ampl
e(m
l)
Vol
ume
of H
Cl
reac
ted
with
NaO
H in
S
ampl
e(m
l)
Mol
e of
HC
l rea
cted
w
ith N
aOH
in s
ampl
e
Mol
e of
NaO
H
unre
acte
d in
sam
ple
Con
cent
ratio
n of
N
aOH
unr
eact
ed w
ith
Eth
yl A
ceta
te(M
)
Ste
ady
Sta
te fr
actio
n co
nver
sion
of
NaO
H,X
a
Con
cent
ratio
n of
N
aOH
rea
cted
with
E
thyl
Ace
tate
(M)
Mol
e of
NaO
H
reac
ted
with
Eth
hyl
Ace
tate
in
Sam
ple(
ml)
Con
cetr
atio
n of
Eth
yl
Ace
tate
rea
cted
with
N
aOH
(M)
Con
cent
ratio
n of
E
thyl
Ace
tate
U
nrea
cted
(M)
1/C
a
1 19 7.6
2.4
0.6
0.6 0.
012
0.88
0.08
8
4.4
0.08
8
0.01
2
83.3
3333
5 19 7.6
2.4
0.6
0.6 0.
012
0.88
0.08
8
4.4
0.08
8
0.01
2
83.3
3333
10 20 8 2 0.5
0.5
0.01 0.
9
0.09 4.
5
0.09
0.01 10
0
15 20 8 2 0.5
0.5
0.01 0.
9
0.09 4.
5
0.09
0.01 10
0
20 20 8 2 0.5
0.5
0.01 0.
9
0.09 4.
5
0.09
0.01 10
0
25 20 8 2 0.5
0.5
0.01 0.
9
0.09 4.
5
0.09
0.01 10
0
Temperature = 60°C
Tim
e(m
in)
Vol
ume
of ti
trat
ing
NaO
H(m
l)
Vol
ume
of q
uenc
hing
H
Cl u
nrea
cted
with
N
aOH
in S
ampl
e(m
l)
Vol
ume
of H
Cl
reac
ted
with
NaO
H in
S
ampl
e(m
l)
Mol
e of
HC
l rea
cted
w
ith N
aOH
in s
ampl
e
Mol
e of
NaO
H
unre
acte
d in
sam
ple
Con
cent
ratio
n of
N
aOH
unr
eact
ed w
ith
Eth
yl A
ceta
te(M
)
Ste
ady
Sta
te fr
actio
n co
nver
sion
of
NaO
H,X
a
Con
cent
ratio
n of
N
aOH
rea
cted
with
E
thyl
Ace
tate
(M)
Mol
e of
NaO
H
reac
ted
with
Eth
hyl
Ace
tate
in
Sam
ple(
ml)
Con
cetr
atio
n of
Eth
yl
Ace
tate
rea
cted
with
N
aOH
(M)
Con
cent
ratio
n of
E
thyl
Ace
tate
U
nrea
cted
(M)
1/C
a
1 20 8 2 0.5
0.5
0.01 0.
9
0.09 4.
5
0.09
0.01 10
0
5 22 8.8
1.2
0.3
0.3 0.
006
0.94
0.09
4
4.7
0.09
4
0.00
6
166.
6667
10 21 8.4
1.6
0.4
0.4 0.
008
0.92
0.09
2
4.6
0.09
2
0.00
8
125
15 22 8.8
1.2
0.3
0.3 0.
006
0.94
0.09
4
4.7
0.09
4
0.00
6
166.
6667
20 21.4
8.56
1.44
0.36
0.36 0.
0072
0.92
8
0.09
28
4.64
0.09
28
0.00
72
138.
8889
25 20.7
8.28
1.72
0.43
0.43 0.
0086
0.91
4
0.09
14
4.57
0.09
14
0.00
86
116.
2791
GRAPH
EXPERIMENT A
ghraph 1/Ca vs t
0102030405060708090
100110
0 5 10 15 20 25 30
t,min
1/C
a ,
M
EXPERIMENT B
Temperature = 30°C
30C
828486889092949698
0 10 20 30
t
1/C
a
Temperature = 40°C
Chart Title
70
75
80
85
90
95
100
105
0 5 10 15 20 25 30
t
1/C
ae
Temperature = 60°C
Chart Title
0
40
80
120
160
200
0 5 10 15 20 25 30
t
1/C
ae
SAMPLE OF CALCULATION
Volume of quenching HCl = (0.1/0.25) x 20 = 8
Unreacted with Naoh in sample
Volume of HCl reacted with = 10 - 8 = 2
NaoH in sample
Mole of HCl reacted with = 0.25x 2 = 0.5
Naoh in sample
Reaction rate (k) = (82-58)/(15-1) = 1.7
Activation energy from the graph
-Ea = (8.3142)x (-0.39+1.05)/(3.14-3.3)(10^-3)
Ea = 33 kj/mol
Activation energy from equation
ln (k2/k1) = E/R (1/T1-1/T2).
ln (0.65/0.35) /(1.556x106-4) = E/(8.3142)
E = 34.29 kj/mol
Discussion
Batch Stirred Tank Reactor is one of the reactors that widely used in industrial.
Batch stirred Tank reactor is a closed system. For this experiment we used liquid that
have a constant density. For that it is a constant-volume Batch reactor.
For experiment A we want to know the order of the reaction and the value of rate
constant (k) and for experiment B we want to know the effect of the temperature on rate
constant and find the value of the activation energy.
Experiment A: Batch Stirred Tank Reactor
In this experiment, we use room temperature that was 27oC to operate the batch
stirred tank reactor. From the result it seems that the volume of titrating NaOH will
increase when time increasing. After we have plotted the graph, it seems that the reaction
was second order. This was proven by the graph 1/Ca vs t that gives us a straight line that
has a positive slope. We can say that our reaction was elementary.
Based on the equation 1/Ca = kt + 1/Cao we can found the reaction rate from the
slope. After we calculate the value of the slope from the graph the value of k was 1.7.
Experiment B: Effect of temperature on Reaction rate constant, k
From the Arrheniu’s equation k=koe–E/RT it shows that temperature has an effect to
the reaction rate constant. To prove that we made experiments that used 3 different
temperatures 30°C, 45°C and 60°C.
We prove it by finding the value of reaction rate for every temperature and
compare it. For the 30°C we get the value of k was 0.35, for 45°C we get 0.8 and for
60°C we get 0.2.
Based on the equation, we will get an increasing value of rate constant when the
temperature is increase. For our experiment we get the result that satisfied the equation
except for the 60°C this happen because of readings error at time 5 to 15 minutes.
Because of that error we get a zigzag graph that gives us a low rate constant that did not
satisfied the equation. Because of that we neglect the value of k at 60°C.
After we have plotted the graph we can find the value of the activation energy.
Arrheniu’s law says that for a reaction that have same concentration, but at two different
temperatures the value of the activation energy is constant. This can be indicates by the
equation ln (k2/k1) = E/R (1/T1-1/T2).
The activation energy for this experiment can be calculated on two ways. First is
using the equation above, second by finding the value of the slope of the graph ln k vs
1/T. The value of the activation energy is the value of the slope based on the equation
ln k = (Ea/R)(1/t).
Graph to find the activation Energy.
lnk vs 1/T
-1.2
-1
-0.8
-0.6
-0.4
-0.2
0
3.14 3.3
1/T
ln k Series1
Using the equation we get the value of the activation energy was 34 kj/mol and
from the graph we get 33 kj/mol. This two value has a very small different. It shows that
we can calculate the activation energy using either ways. Its also show that our graph is
correct.
Conclusions
After all experiment has been done we have find some points that make our
conclusions.
Our 1st conclusions were that this equation is elementary and it is 2nd order. We
conclude this by the graph 1/Ca versus t(time) that has been plotted in experiment A. we
get straight line graph that has a positive slope value. We can write the reaction rate for
this equation that is –ra = kCaCb.
Our second conclusions that the value of k is dependent on temperature and the
rate constant will only constant for a constant temperature. When the temperatures
increase the value of reaction rate also increase. This satisfied the Arrehinu’s equation
k=koe–E/RT
We also conclude that activation energy is constant for reactions that have a same
concentration but different temperatures. This has been proven by the equation ln (k2/k1)
= E/R (1/T1-1/T2) and the graph that we have plotted. We get almost the same value.
Recommendations
After we have finished this experiment, we find that are several factors in this
experiment that can be fixed to make sure that the experiment runs better. This is some of
my recommendation for this experiment:
For experiment B the readings should be taken at least 4 different temperatures.
Not 3 temperatures only. When we take 4 different temperatures we can get a
better graph for findings the activation energy.
The Arrheniu’s equation should be provided in the summary of theory to make
sure the students more understand about the activation energy and not only by
following the instruction only.
Reference
Levenspiel, O, Chemical Reaction Engineering, John Wiley, 1972
Robert H.Perry, Don W.Green, Perry’s Chemical Engineers’ Handbook,
McGraw Hill,1998.
Smith,J.M, Chemical Engineering Kinetics, McGraw Hill, 1981.
Appendics
C r1 r1
r2 r2
r3 r3
r1
r2
r3
T
r
T
r
C