1) ABSTRACT A tubular reactor is a vessel through which flow is continuous, usually at steady state, and configures so that conversion of the chemicals and other dependent variables are functions of position within the reactor rather than of time This e!periment is conducted to achieve the ob"ective that has been considered which are to e!amine the effect of pulse input and step change input in tubular flow reactor and to construct the residence time distribution functi function on by using using tubula tubularr machin machine e Based Based on the e!perim e!periment, ent, two e!perim e!periment ent were were conducted which is pulse input e!periment and step change input e!periment #n the pulse input e!periment, the flow rate was set up at $%% m & s'1 and let it for one minute before reading ta(en every &% seconds until the conductivity reading is %% n the other hand, the step change input e!periment, the conductivity were observe every &% seconds until the reading at *+ is constant for & times Result show that when the outlet conductivity increases at some period of time, it will then decrease into a constant value #n conclusion, both e!periment had been done successfully, successfully, abiding stated theories
1
+) #TR-.CT#
A tubular reactor is a vessel through which flow is continuous, usually at steady state, and configures so that conversion of the chemicals and other dependent variables are functions of position within the reactor rather than of time /low in tubular reactors can be laminar, as with viscous fluids in small'diameter tubes, and greatly deviate from ideal plug'flow behaviour, or turbulent, as with gases There are tubular flow reactors applications which are large'scale reactions, fast reactions, homogeneous or heterogeneous reactions, continuous production, and high'temperature reactions As for an ideal plug flow reactor, a pulse of tracer in"ected 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 the following the concentration of tracer versus time at the e!it This procedure is called the stimulus'response techni0ue igh temperature reactions Residence Time -istribution 2RT-) analysis is 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 (nown 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 and the introduction of the tracer should not modify the hydrodynamic conditions #n general, the change in tracer concentration will either be a pulse or a step
&) B34CT#54
&1
4!periment 1 • •
To e!amine the effect of a pulse input in a tubular flow reactor To construct a residence time distribution 2RT-) function for the tubular flow reactor
2
&+
4!periment + • •
To e!amine the effect of a step change input in a tubular flow reactor To construct a residence time distribution 2RT-) function for the tubular flow reactor
6) T4R7 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 #n 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 re0uired but without bac('mi!ing of products and reactants /low 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 mi!ing and heat transfer are improved /or slow reactions and especially in small laboratory and pilot'plant reactors, establishing turbulent flow can result in inconveniently long reactors or may re0uire 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 The residence'time
of an element of fluid leaving a reactor is the length of time
spent by that element within the reactor /or a tubular reactor, under plug'flow conditions, the residence'time is the same for all elements of the effluent fluid 28 9 -enbigh)
3
The procedure would be to carried out e!periments with tubular reactor at varying feed rates, measuring the e!tent of reaction of the stream leaving the reactor ne possible method might to add :inert; gas to the acetaldehyde vapour in such 0uantity that the change in density between entry and e!it of the reactor could be neglected #n that case, the batch reactor time and the residence'time would both be e0ual to the space'time .sing the result of e!periment, apply e0uation below to determine n and k 2< wil bw (nown from the stoichiometry)
M f =various values of feed rate τ= space-time from e!periment, it should be able to draw a curve of τ against xout , the slope of which according to the first e0uation, should be
Ta(ing the logarithm of both sides of e0uation, we can obtain
So, n and k can be obtained from the intercept and slope of the appropriate log'log plot This approach is that the e!periments be isothermal 2k and T outside the integral in the first e0uation) #f the reactor is not isothermal, then the first e0uation must be written as
=here T in is the temperature of the feed into the reactor
4
Therefore, when the effect of wall heat transfer and of velocity gradient operates simultaneously they might, under rather special circumstance, give rise to a more comple! (ind of temperature profile owever, the most commonly observed profiles obtained with e!othermic reactions in e!ternally cooled reactors The reason why the elementary design method is erroneous when the transverse gradients are appreciable arises from the e!treme sensitivity of reaction rate to changes of temperature
>) A??ARAT.S A- @AT4R#A • • •
Tubular flow reactor -eionied water Sodium chloride solution 2aCl)
) ?RC4-.R4
1
9eneral Start'.p ?rocedure 1 All valves are ensured closed e!cept for valve 5$ + The following solutions are preparedD Tan( B1D -eionied water • Tan( B+D %%>@ sodium chloride solution 2aCl) • & The power for control panel was turned on 6 =ater "ac(et B6 and pre'heater B> was filled with clean water 5alves 51& and 5E were opened ?ump ?& was switched on to circulate the water through pre'heater B> > Stirrer motor @1 was switched on and the speed was set to about +%% rpm 5alves 5+ and 51% were opened ?ump ?1 was switched on ?1 was ad"usted to flowrate of $%% mFmin at flow meter /#'%1 5alve 51% was closed and pump ?1 was switched off $ 5alves 5 and 51+ were opened ?ump ?+ was switched on ?+ was ad"usted to flowrate of 1%% mFmin at flow meter /#'%+ 5alve 51+ was closed and pump ?+ was switched off E The unit is ready for e!periment
+
4!perimental procedure 5
+1
4!periment 1D ?ulse #nput in a Tubular /low Reactor
1 The general start'up procedure was performed as in 1 + 5alve 5G was opened and pump ?1 was switched on & ?ump ?1 flow controller was ad"usted to give a constant flow rate of deionied water into the reactor R1 at appro!imately $%% mFmin at /1'%1 6 The deionied water continued to flow through the reactor until the inlet 2*#'%1) and outlet 2*#'%+) conductivity values were stable at low levels Both conductivity values were recorded > 5alve 5G was closed and pump ?1 was switched off 5alve 511 was opened and pump ?+ was switched on The timer was set simultaneously $ ?ump ?+ was flow controller was ad"usted to give a constant flow rate of salt solution into the reactor R1 at $%% mFmin at /#'%+ E The salt solution was allowed to flow for 1 minute and the timer was reset and restarted G 5alve 511 was closed and pump ?+ was switched off 5alve 5G was 0uic(ly opened and pump ?1 was switched on 1% The deionied water flowrate was made sure always maintained at $%% mFmin by ad"usting ?1 flow controller 11 Both the inlet 2*#'%1) and outlet 2*#'%+) conductivity values were recorded at regular intervals of &% seconds 1+ Conductivity values were recorded until all readings were constant and approach stable low level values
++
4!periment +D Step Change #nput in a Tubular /low Reactor
1 The general start'up procedure was performed as in 1 + 5alve 5G was opened and pump ?1 was switched on & ?ump ?1 flow controller was ad"usted to give a constant flow rate of deionied water into the reactor R1 at appro!imately $%% mFmin at /#'%1 6 The deionied water was allowed to flow through the reactor until the inlet 2*#'%1) and outlet 2*#'%+) conductivity values are stable at low levels Both conductivity values were recorded > 5alve 5G was closed and pump ?1 was switched off 5alve 511 was opened and pump ?+ was switched on The timer was set simultaneously
6
$ Both the inlet 2*#'%1) and outlet 2*#'%+) conductivity values were recorded at regular intervals of &% seconds E The conductivity values were ta(en down until all readings are almost constant
&
9eneral Shut'-own ?rocedure 1 Both pumps ?1 and ?+ were switched off 5alves 5+ and 5 were closed + The heaters were switched off & Cooling water was (ept to circulate through the reactor while the stirrer motor is switched on to allow the water "ac(et to cool down to room temperature 6 The power for the control panel was switched off
7
$) R4S.T A- CAC.AT# 4!periment 1D ?ulse #nput in a Tubular /low Reactor Time 2min)
Conductivity 2msFcm) #nlet utlet
C2t)
42t)
2
Tm
σ
s& 2min&)
2min) 2min)
%> 1% 1> +% +> &% &> 6% 6>
%% %% %% %% %% %% %% %% %%
Time, t
utlet Conductivity, C2t) %% 1$ +% +1 %$ %+ %% %% %%
%> 1% 1> +% +> &% &> 6% 6>
%% 1$ +% +1 %$ %+ %% %% %%
%% 1$ +% +1 %$ %+ %% %% %%
%%%%% %6+> %>%%$ %>+>$ %1$>+ %%>%1 %%%%% %%%%% %%%%%
42t)
1%%%%
t42t)
%%%%% %6+> %>%%$ %>+>$ %1$>+ %%>%1 %%%%% %%%%% %%%%% Table $1 Result of
8
%%%%% %6+> %$>11 1%>16 %6&E% %1>%& %%%%% %%%%% %%%%% e!periment 1
%$&1
11$$
2t'tm)+42t)
2t'tm)&42t)
%%%%% %%%%% %1+>+ %>+>$ %&G6+ %+%%6 %%%%% %%%%% %%%%%
%%%%% %%%%% %%+ %>+>$ %>G1& %6%%E %%%%% %%%%% %%%%%
Conductivity vs Time 2.5 2 1.5 Conductivity
Conductivity vs Time 1 0.5 0 0.5
1
1.5
2
2.5
3
3.5
4
4.5
Time
/igure $1 9raph of Conductivity vs Time
E(t) vs Time 0.6 0.5 0.4 E(t)
0.3
E(t) vs Time
0.2 0.1 0 0.5
1
1.5
2
2.5
3
3.5
4
Time
/igure $+ 9raph of 42t) vs Time
9
4.5
4!periment +D Step Change #nput in Tubular /low Reactor Time 2min) %% %> 1% 1> +% +> &% &> 6% 6> >% >> %
Conductivity 2msFcm) #nlet utlet %% %% +E %% &% %% &1 %% &1 %E &1 1E &1 1G &1 1G &1 1G &1 +% &1 +% &1 +% &1 +%
t 2min)
C 2t)
%% %> 1% 1> +% +> &% &> 6% 6> >% >> %
%% %% %% %% %E 1E 1G 1G 1G +% +% +% +%
42t) 2min'1)
C2t)
42t)
%% %% %% %% %E 1E 1G 1G 1G +% +% +% +%
%%%%% %%%%% %%%%% %%%%% %1%%% %++>% %+&$> %+&$> %+&$> %+>%% %+>%% %+>%% %+>%%
t42t)
tm 2min)
61&&6
2t'tm)
%%%%% %%%%% '61&&6 %%%%% %%%%% '&&&6 %%%%% %%%%% '&1&&6 %%%%% %%%%% '+&&6 %1%%% %+%%% '+1&&6 %++>% %>+> '1&&6 %+&$> %$1+> '11&&6 %+&$> %E&1& '%&&6 %+&$> %G>%% '%1&&6 %+>%% 11+>% %& %+>%% 1+>%% %E %+>%% 1&$>% 1& %+>%% 1>%% 1E Table $+ Result of e!periment +
10
2
3
σ
s
2min+)
2min&)
16%>1
'%6%G
2t'tm)+42t)
2t'tm)&42t)
%%%%% %%%%% %%%%% %%%%% %6>>1 %%%& %&%>1 %%G>& %%%6+ %%&& %1E$$ %6G %E$1%
%%%%% %%%%% %%%%% %%%%% '%G$1% '%GE%> '%&6>E '%%%6 '%%%% %%1+& %1+$ %&E1 1+>G
Conductivity vs Time 2.5 2 1.5 Conductivity
Conductivity vs Time 1 0.5 0 0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
Time
/igure $& 9raph of Conductivity vs Time
E(t) vs Time 0.3 0.25 0.2 E(t)
0.15
E(t) vs Time
0.1 0.05 0 0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Time
/igure $+ 9raph of 42t) vs Time
11
5.5
6
Sample of calculation 4!periment 1D ?ulse input in tubular flow reactor Residence time distribution function, E (t)
H1 I G I E ∞
∫ C ( t ) dt = 3h [ C + 4 C + 2 C 0
1
2
+ 4 C 3 + 2 C4 + ….. + 4C N-1 + CN ]
0
where, h =
h=
tN - t0 N
t N - t0 N
=
4.5 - 0 = 0.56 8
4.5
(0.0) + 4 ( 1.7 ) + 2 ( 2.0 ) + 4 ( 2.1 ) + 2 ( 0.7 ) + 4 ( 0.2 ) = 3.9947 g.!" # ∫ C ( t ) dt = 0.56 [ ] 3 + 2(0)+ 4(0)+2(0) 0
&
At time I % minute, C 2t) I %% $ ( t ) =
C(t ) 2.75
∫ C ( t ) dt 0
$ ( t ) =
0.0 = 0.0 3.9947 %.!" #
Mean residence time, tm ∞
∫ 0
h $ ( t ) d& = [ $0 + 4 $1 + 2 $2 + 4 $3 + 2$ + ….. + 4 $ N-1 + $N ] 3
12
4.5
t =
∫ t$ ( t ) dt 0
[
0.56 (0.00) +4 ( 0.4256 ) + 2 ( 0.5007 ) + 4 ( 0.5257 ) + 2 ( 0.1752 ) + 3 4 ( 0.0501 ) + 2(0) + 4(0) + 2(0)
=
]
I 1%%%% min
Second moment, variance, σ 2 ∞
∫ ( t- t
2
' =
2
) $(t) dt
0
4.5
'
=∫ ( t- t ) 2 $ ( t ) dt
2
0
'
2
=
[
0.56 (0.0) +4 ( 0 ) + 2 ( 0.1252 ) + 4 ( 0.5257 ) + 2 ( 0.3942 ) + 3 4 ( 0.2004 ) + 2(0) + 4(0) + 2(0)
]
I %$&1 min +
' = 0.8580 !"
Third moment, skewness, s 3 t −t m
¿ ¿ ¿
∞
∫¿ 0
1 ( 0.56 ) [ 0 + 4 ( 0 ) + 2 ( 0.0626 ) + 4 ( 0.5257 ) + 2 ( 0.5913 ) +4 ( 0.4008 )+ 2 ( 0 )+ 4 ( 0 )+ 2 ( 0 ) ] 3
I
I %G&>G min & 1
∞
∫
3 2 0
σ
1
3
( t −t m ) E ( t ) dt
I
0.8580
3 2
x ( 0.9359 )
13
S& I 11$$ min &
4!periment +D Step Change input in tubular flow reactor Residence Time Distribution unction, E(t)
H 1 I 1& I 1+ X N
∫ C ( t ) dX
h 3
!
X 0
[ C 0 + 4 C 1+2 C 2+ 4 C 3+ 2 C 4 + … + 4 C N −1+C N ]
t N − t
0
=here, h I
t N −t
0
hI
N
=
N
6.00− 0.00 I %> 12
2. ves are achieved successfully. edure
¿
6.00
[ 0 + 4 ( 0 ) + 2 ( 0 ) + 4 ( 0 ) +2 ( 0.8 ) + 4 (1.8 )+ 2 ( 1.9 ) + 4 ( 1.9 ) +2 ( 1.9 )+ 4 ( 2.0 )+2 ( 2.0 ) + 4 ( 2.0 ) + 2 ( 2.0 ) ∫ C ( t ) dt = 0.5 3 0
IE g min F m & At time I %%% min, C2t) I %%
C ( t ) E ( t ) = 6.00
∫ C ( t ) dt 0
E ( t ) =¿
0.0 8
I %%%%%
14
Mean Residence Time, t m ∞
∫ E ( t ) dX 0
h
!
[ E0 +4 E1 +2 E 2+ 4 E3 +2 E4 + … +4 E
N −1
3
+ E ] N
2.00
tm I
∫ tE ( t ) dt 0
2. vesareachieved successfully . edure
¿
6.00
[ 0 + 4 ( 0 ) + 2 ( 0 ) + 4 ( 0 ) +2 ( 0.2 ) + 4 ( 0.5625 ) + 2 ( 0.7125 )+ 4 ( 0.8313 ) + 2 ( 0.95 ) + 4 ( 1.125 ) + 2 (1.2 ∫ tE ( t ) dt = 0.5 3 0
I 61&&6 min
Second moment, "ariance,σ 2 ∞
∫ ( t −tm ) E ( t ) dt 2
+
J I
0
( t −tm )2=¿ 2%%%%% K 61&&6) + I 1$%E>
At t I %%% min and t m I 61&&6 min, ∞
∫ ( t −tm ) E ( t ) dt 2
0
I
0.5 [ 0 + 4 ( 0 )+ 2 ( 0 ) + 4 ( 0 ) +2 ( 0.4551 ) + 4 ( 0.6003 )+ 2 ( 0.3051 ) + 4 ( 0.0953 ) + 2 ( 0.0042 )+ 4 ( 0.0336 )+ 2 ( 0.1877 ) 3
∞
∫ ( t −tm ) E ( t ) dt 2
0
I
1.4051 min
+
J+ I 16%>1 min + J I 11E>6 min
15
Third moment, Skewness, s 3 ∞
∫ ( t −tm ) E ( t ) dt 3
&
s I1FJ
&F+
0
I 6.00
1
0.5 [ 0 + 4 ( 0 )+ 2 ( 0 )+ 4 ( 0 )+2 (−0.9710 ) +4 (−0.9805 )+ 2 (−0.3458 ) + 4 (−0.0604 ) + 2 (−0.0006 )+ ∫ / 3 1.1854 3 2
0
∞
∫ ( t −tm ) E ( t ) dt =−0.4096 3
1FJ &F+
0
min&
E) -#SC.SS#
/irstly, the ob"ectives that need to be achieve for this tubular reactor e!periment is to e!amine the effect of a pulse input and step change in a tubular reactor and also to construct the residence time distribution 2RT-) function for the tubular flow reactor at the end of the e!periment The e!periment was run at the $%% mFmin of flowrate =hile the e!periment 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 /or 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 /or this e!periment, we e!amine the effects of flow for two types of reaction which are in pulse input and step change The flowrate of solution is (ept constant at $%% mFmin /or these types of e!periment, 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 mSFcm at time of + minutes which are the highest value After that, the conductivity is decrease within the time and comes to be constant at the time of &> minutes /rom the result, it shows that the result did not differ from the theory that recorded that the conductivity is reaching ero at time of 6 minutes Thus, e!periment 1 is a succeess 16
#n addition, for the graph of step change the outlet conductivity is increase within the time by started at time of +% minutes which it inlet conductivity is &1 mSFmin and then undergoes some increment until at minute % which the outlet conductivity is +% mSFmin The construction of the residence time distribution 2RT-) function for the tubular flow reactor for pulse input and also step change is done after that The residence time distribution is plotted based on e!it time 242t)) versus time from the data that had been recorded in the table /rom the graph plotted, it is almost same with the graph that is stated at the theory /rom the graph, it can be concluded that the residence time distribution is depends on the outlet conductivity The other & data that had been obtained and calculated are mean residence time, t m variance 2second moment), J+ and s(ewness 2third moment), s& that recorded 1%%%%, %$&1 and 11$$ respectively The s(ewness for the pulse input give a positive value and it called positive s(ew Compared of the step change, the graph is almost same to the outlet conductivity versus time which the residence time distribution 2RT-) is increase within the time /or the step change, the mean residence time distribution that calculated is 61&&6 minutes The other + data that are calculated which are variance 2second moment), J + and s(ewness 2third moment), s& are 16%>1 and '%6%G respectively The s(ewness gives a negative value and it is called negative s(ew compare to pulse input
G) CC.S# /or both e!periment, all ob"ectives are achieved successfully /or the first e!periment, the effect of a pulse input is e!amined and a RT- for tubular flow is constructed Same goes for e!periment two where the effect of a step change input in tubular flow reactor is recognised and a RT- was also constructed
1%) R4C@@4-AT# 17
•
• • • •
4ach e!periment must perform general start'up and shut'down procedure to ma(e sure the e!periment runs smoothly pen and close the valve carefully according to the procedure given @a(e sure there is no lea(age at the e0uipment /low rate of the reactant must remain constant throughout the e!periment @a(e sure the inlet and outlet conductivity are stable before starting the e!periment
11) R4/4R4C4 •
evenspiel, ctave 21GGG) Chemical Reaction 4ngineering 2&rd ed) 3ohn =iley
•
L Sons auman, 4 Bruce 2+%%6) MResidence Time -istributionsM andboo( of #ndustrial
•
@i!ingD Science and ?ractice =iley #nterscience pp 1K1$ Tubular /low Reactor Static @i!er 2nd) Retrieved April +G, +%1>, from httpDFFwwwstami!co'usacomFtubular'flow'reactors 28 9 -enbigh, Chemical Reactor TheoryD An #ntroduction, 61'6>)
18
1+) A??4-#N
19
