Tubular Flow Reactor Report

7/17/2019 Tubular Flow Reactor Report

http://slidepdf.com/reader/full/tubular-flow-reactor-report 1/19

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 andstep change input in tubular flow reactor and to construct the residence time distribution

function by using tubular machine Based on the e!periment, two e!periment 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, 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 functionsof 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 gasesTurbulent 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) C2t) 42t) Tm

2min)σ

2

2min)

s&

2min&)#nlet utlet

%> %% %% %% %%%%%

1%%%% %$&1 11$$

1% %% 1$ 1$ %6+>

1> %% +% +% %>%%$

+% %% +1 +1 %>+>$

+> %% %$ %$ %1$>+

&% %% %+ %+ %%>%1

&> %% %% %% %%%%%

6% %% %% %% %%%%%

6> %% %% %% %%%%%

Time, t utlet

Conductivity,

C2t)

42t) t42t) 2t'tm)+42t) 2t'tm)&42t)

%> %% %%%%% %%%%% %%%%% %%%%%

1% 1$ %6+> %6+> %%%%% %%%%%

1> +% %>%%$ %$>11 %1+>+ %%+

+% +1 %>+>$ 1%>16 %>+>$ %>+>$

+> %$ %1$>+ %6&E% %&G6+ %>G1&

&% %+ %%>%1 %1>%& %+%%6 %6%%E

&> %% %%%%% %%%%% %%%%% %%%%%

6% %% %%%%% %%%%% %%%%% %%%%%

6> %% %%%%% %%%%% %%%%% %%%%%

Table $1 Result of e!periment 1

8



0.5 1 1.5 2 2.5 3 3.5 4 4.5

0

0.5

1

1.5

2

2.5

Conductivity vs Time


Time

Conductivity

/igure $1 9raph of Conductivity vs Time

0.5 1 1.5 2 2.5 3 3.5 4 4.5

0

0.1

0.2

0.3

0.4

0.5

0.6

E(t) vs Time

E(t) vs Time

Time

E(t)

/igure $+ 9raph of 42t) vs Time

9



4!periment +D Step Change #nput in Tubular /low Reactor

Time

2min)

Conductivity

2msFcm)

C2t) 42t) tm

2min)

σ 2

2min+)

s3

2min&)#nlet utlet

%% %% %% %% %%%%%

61&&6 16%>1 '%6%G

%> +E %% %% %%%%%

1% &% %% %% %%%%%

1> &1 %% %% %%%%%

+% &1 %E %E %1%%%

+> &1 1E 1E %++>%

&% &1 1G 1G %+&$>

&> &1 1G 1G %+&$>

6% &1 1G 1G %+&$>

6> &1 +% +% %+>%%

>% &1 +% +% %+>%%>> &1 +% +% %+>%%

% &1 +% +% %+>%%

t 2min) C 2t) 42t) 2min'1) t42t) 2t'tm) 2t'tm)+42t) 2t'tm)&42t)

%% %% %%%%% %%%%% '61&&6 %%%%% %%%%%

%> %% %%%%% %%%%% '&&&6 %%%%% %%%%%

1% %% %%%%% %%%%% '&1&&6 %%%%% %%%%%

1> %% %%%%% %%%%% '+&&6 %%%%% %%%%%+% %E %1%%% %+%%% '+1&&6 %6>>1 '%G$1%

+> 1E %++>% %>+> '1&&6 %%%& '%GE%>

&% 1G %+&$> %$1+> '11&&6 %&%>1 '%&6>E

&> 1G %+&$> %E&1& '%&&6 %%G>& '%%%6

6% 1G %+&$> %G>%% '%1&&6 %%%6+ '%%%%

6> +% %+>%% 11+>% %& %%&& %%1+&

>% +% %+>%% 1+>%% %E %1E$$ %1+$

>> +% %+>%% 1&$>% 1& %6G %&E1

% +% %+>%% 1>%% 1E %E$1% 1+>G

Table $+ Result of e!periment +

10



0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

0

0.5

1

1.5

2

2.5



Time

Conductivity

/igure $& 9raph of Conductivity vs Time

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

0

0.05

0.1

0.15

0.2

0.25

0.3

E(t) vs Time

E(t) vs Time

Time

E(t)

/igure $+ 9raph of 42t) vs Time

11



Sample of calculation

4!periment 1D ?ulse input in tubular flow reactor

Residence time distribution function, E (t)

H1 I G

I E

∫0

∞

C (t ) dt =h

3[ C0 + 4C1 + 2C2 + 4C3 + 2C4 + ….. + 4CN-1 + CN ]

where, h = tN - t0

N

h =tN - t0

N =

4.5 - 0

8= 0.56

∫0

4.5

C ( t ) dt =0.56

3 [ (0.0) + 4 (1.7 ) + 2 (2.0 ) + 4 (2.1 ) + 2 (0.7) + 4 (0.2)+ 2(0)+ 4(0)+2(0) ] = 3.9947 g.!" #

&

At time I % minute, C 2t) I %%

$ (t ) =C ( t )

∫0

2.75

C ( t ) dt

$ (t ) = 0.03.9947 %.!" #

= 0.0

Mean residence time, tm

∫0

∞

$ (t )d& =h

3[ $0 + 4 $1+ 2 $2 + 4 $3 + 2$ + ….. + 4 $N-1 + $N ] t =∫

0

4.5

t$ ( t )dt

12



=0.56

3 [ (0.00) +4 (0.4256 ) + 2 (0.5007 ) + 4 (0.5257 ) + 2 (0.1752 ) + 4 (0.0501 ) + 2(0) + 4(0) + 2(0) ] I 1%%%% min

Second moment, variance, σ2

'2 =∫

0

∞

( t- t )2$(t) dt

'2=∫

0

4.5

( t- t)2$ ( t )dt

'2=

0.56

3 [ (0.0) +4 (0 ) + 2 (0.1252 ) + 4 (0.5257 ) + 2(0.3942 ) + 4 (0.2004 ) + 2(0) + 4(0) + 2(0) ] I %$&1 min+

' = 0.8580 !"

Third moment, skewness, s3

t −t m

¿¿¿

∫0

∞

¿

I 13 (0.56 ) [0+4 (0 )+2 (0.0626 )+4 (0.5257 )+2 (0.5913 )+4 (0.4008 )+2 (0 )+4 (0 )+2 (0 ) ]

I %G&>G min&

1

σ

3

2

∫0

∞

(t −t m )3 E ( t ) dt I

1

0.85803

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 0

X N

C ( t )dX !h

3 [ C 0+4 C 1+2 C 2+4 C 3+2C 4+…+4 C N −1+C N ]

=here, h I

t N −t 0

N

h I

t N −t 0

N =

6.00−0.00

12 I %>

2. ves are achieved successfully. edure¿

∫0

6.00

C (t ) dt =0.5

3 [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 )

IE g min F m&

At time I %%% min, C2t) I %%

E ( t )= C (t )

∫0

6.00

C (t ) dt

E ( t )=¿ 0.0

8 I %%%%%

14



Mean Residence Time, tm

∫0

∞

E( t )dX !h

3 [ E0+4 E1+2 E2+4 E3+2 E4+…+4 E N −1+ E N ]

tm I ∫0

2.00

tE ( t )dt

2. vesare achieved successfully . edure¿

∫0

6.00

tE ( t ) dt =0.5

3 [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

I 61&&6 min

Second moment, "ariance,σ2

J+ I ∫0

∞

( t −tm )2 E ( t ) dt

At t I %%% min and tm I 61&&6 min, (t −tm )2=¿ 2%%%%% K 61&&6)+ I 1$%E>

∫0

∞

( t −tm )2 E ( t ) dt I

0.5

3

[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 )

∫0

∞

( t −tm )2 E ( t ) dt I 1.4051min +

J+ I 16%>1 min+

J I 11E>6 min

15



Third moment, Skewness, s3

s&I1FJ &F+ ∫0

∞

( t −tm )3 E (t ) dt

I

1

1.18543/2 ∫

0

6.000.5

3 [0+4 (0 )+2 (0 )+4 (0 )+2 (−0.9710 )+4 (−0.9805 )+2 (−0.3458 )+4 (−0.0604 )+2 (−0.0006 )+

1FJ &F+ ∫0

∞

( t −tm )3 E (t )dt =−0.4096 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, tm

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 minutesThe 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

http://www.stamixco-usa.com/tubular-flow-reactors

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1+) A??4-#N

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Tubular Flow Reactor Report