Tubular Plug Fow Reactor

7/23/2019 Tubular Plug Fow Reactor

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Abstract

The objective of this experiment is to determine the eect of a pulse

input in a tubular ow reactor and to construct a residence time distribution

(RTD) function for the tubular ow reactor. So there was two experiment

were conducted which are pulse input and step chane in a tubular ow

reactor (!"#$#). The dierences between these experiment is either for a

short interval (%impulse function&) or at a selected instant' a sudden chane

from one feed to the other is made for a continuous period (%step function&)

and the concentration chanes with time in each vessel is measured. n this

experiment the procedure are same except for pulse input' there is a step

where is at constant owrate of salt at $$ ml*min was allowed to ow for #minute then' the timer is started. The readin of conductivit+ is ta,en for

time interval -$ seconds. or step chane' the conductivit+ were ta,en after

-$ seconds also until the readin is constant at - times.

#



Introduction

Tubular Reactor

/ tubular reactor is a vessel throuh which ow is continuous' usuall+

at stead+ state' and con0ured 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 uids ow as if the+ were solid

plus or pistons' and reaction time is the same for all owin material at an+

iven tube cross section. Tubular reactors resemble batch reactors in

providin initiall+ hih drivin forces' which diminish as the reactions

proress down the tubes. low in tubular reactors can be laminar' as with

viscous uids in small1diameter tubes' and reatl+ deviate from ideal plu1

ow behavior' or turbulent' as with ases. Turbulent ow enerall+ is

preferred to laminar ow' because mixin and heat transfer are improved.

or slow reactions and especiall+ in small laborator+ and pilot1plant reactors'

establishin turbulent ow can result in inconvenientl+ lon reactors or ma+

re2uire unacceptabl+ hih feed rates.

Tubular reactors are often used when continuous operation is re2uired

but without bac,1mixin of products and reactants. The Tubular Reactor is

speciall+ desined to allow detailed stud+ of this important process. t is one

of three reactor t+pes which are interchaneable on the Reactor Service 3nit'

the others bein 4ontinuous Stirred Tan, Reactor and !atch Reactor.

Reactions are monitored b+ conductivit+ probe as the conductivit+ of the

solution chanes with conversion of the reactants to product. This means

that the inaccurate and inconvenient process of titration' which was formall+

used to monitor the reaction proress' is no loner necessar+.

The bac, mixin created b+ turbulence and diusion in a tubular reactor

produces a conversion which is lower than predicted b+ the plu1ow model.

Since bac, mixin is not as extensive as in a stirred tan,' conversion in a

tubular reactor is often hiher than conversion in a 4STR.The tubular ow

5

http://en.wikipedia.org/wiki/Plug_flow_reactor_model

http://en.wikipedia.org/wiki/Steady_state

http://en.wikipedia.org/wiki/Laminar

http://en.wikipedia.org/wiki/Turbulent

http://en.wikipedia.org/wiki/Steady_state

http://en.wikipedia.org/wiki/Laminar

http://en.wikipedia.org/wiki/Turbulent

http://en.wikipedia.org/wiki/Plug_flow_reactor_model



reactor application are for lare scale reaction' fast reactions' homoenous

or heteroeneous reactions' continuous production and hih temperature

reactions.

6ih temperature reactions residence time distribution (RTD) anal+sisis a ver+ e7cient dianosis tool that can be used to inspect the malfunction

of chemical reactors. Residence time distributions are measured b+

introducin a non1reactive tracer into the s+stem inlet. The concentration of

the tracer is chaned accordin to a ,nown function and the response is

found b+ measurin the concentration of the tracer at the outlet. The

selected tracer should not modif+ the ph+sical characteristics of the uid

(e2ual densit+' e2ual viscosit+) and the introduction of the tracer should not

modif+ the h+drod+namic conditions. n eneral' the chane in tracer

concentration will either be a pulse or step.

The residence time distribution of real reactor deviated from that of an

ideal reactor' dependin on the h+drod+namics within the vessel. / non18ero

variance indicates that there is some dispersion alon the path of the uid'

which ma+ be attributed to turbulence' a non1uniform velocit+ pro0le' or

diusion. f the mean of the 9(t) curve arrive earlier than the expected time(t) it indicates that there is stanant uid within the vessel. f the residence

time distribution shows more than one main pea, it ma+ indicates

channelin' parallel paths to the exit' or stron internal circulation.

-



Objective

Experiment 1: Pulse Input In A Tubular Flow Reactor

#. To examine the eect of a pulse input in a tubular owreactor

5. To construct a residence time distribution (RTD) function for

the tubular ow reactor.

Experiment 2: tep !"an#e Input In A Tubular Flow

Reactor$

#. To examine the eect of a step chane input in a tubular ow

reactor

5. To construct a residence time distribution (RTD) function for

the tubular ow reactor

T"eor%

/ tubular reactor is a vessel throuh ow is continuous' usuall+ at

stead+ state' and con0ured 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 uid ows as if the+ were solids

plus or pistons' and reaction time is the same for followin material at an+

iven tube section. Tubular reactors resemble batch reactors in providin

initiall+ hih drivin forces' which diminish as the reaction proress down the

tubes. Tubular reactor are often used when continuous operation is re2uired

but without bac,1mixin of products and reactants.

low in tubular reactors can be laminar' as with viscous uids in small in

small diameter tubes and reatl+ deviate from ideal plu ow behavior' or

:



turbulent' as with ases turbulent ow enerall+ is preferred to laminar ow'

because mixin and heat transfer are improved. or slow reaction and

especiall+ in small laborator+ and pilot plant reactors' establishin turbulent

ow can result inconvenientl+ lon reactors or ma+ re2uire unacceptabl+

hih feed rates.

Tubular reactor is speciall+ desined to allow detailed stud+ important

process. The tubular reactor is one of three reactor t+pes which are

interchaneable on the reactor service unit. The reaction are monitored b+

conductivit+ probe as the conductivit+ of the solution chanes with

conversion of the reactant to the product. This means that the inaccurate

and inconvenient process of titration' which was formall+ used to monitor the

reaction proress is no loner necessar+. The residence time of an element

of uid leavin a reactor is the lenth of time spent b+ that element within

the reactor. or a tubular ow reactor' under plu ow reactor conditions'

the residence time is the same for all of the element.

;ass balance

or a time element <t and a volume of element <=' the mass balance for

species >i? is iven b+ the followin e2uation@

A/4/ B v <t C A/4/ B v <v <t C r/ <=<t E $

Fhere A/ @ volumetric owrate of reactant / to the reactor ' G*s

4/ @ concentration of reactant /' mol*G

t/@ rate of disappearance of reactant /' mol*G.s

the conversion H is de0ned as'

HE (initial concentration 1 0nal concentration)

The s+stem is stead+ state so'

C A/<4/ C I/ <v E $

J



d4/*d=E 1d4/*r/

at the entrance @

=E$

4/E4/o

/t the exit@

=E=R (Total reactor volume)

4/E4/ (exit conversion)

1=R*A/E Kd4/*r/

;ean residence time' tm E ∫0

∞

t ( E )dt

Second moment' =ariance' L5 E ∫

0

∞

(t −tm ) ᴧ 2 ( E )t dt

Third moment' S,ewness' s- E #* L-*5 ∫0

∞

(t −tm ) ᴧ 3 ( E )t dt

M



Apparatus

The iure #.$@ The Tubular low Reactor !"#$#

Tubular ow reactor (!"#$#)' deioni8ed water' sodium h+droxide and eth+l

acetate.



Procedure:

#. The eneral start1up procedure were performed.5. =alve =N was opened and pump "# was switched on.-. "ump "# ow controller was adjusted to ive a constant ow rate of

de1ioni8ed water into the reactor R# at approximatel+ $$ml*min at T1

$#.:. The de1ioni8ed water was allowed to continue owin throuh the

reactor until the inlet (A1$#) and outlet (A1$5) conductivit+ values are

stable at low levels. !oth conductivit+ were recorded.J. =alve =N was closed and pump "# was switch o.M. =alve =## was opened pump "5 was switch on. The timer was started

simultaneousl+.

. "ump "5 ow controller was adjusted to ive a constant ow rate ofde1ioni8ed water into the reactor R# at approximatel+ $$ml*min at T1

$5.O. The salt solution was allowed to ow for # minute' then reset and

restart the timer. This will start the averae pulse input.N. =alve =## and pump "5 was switched on. =alve =N was opened and

pump "# was switched on.#$. ;a,e sure de1ioni8ed water into the reactor R# at approximatel+

$$ml*min at b+ adjustin the ow controller T1$#.

##. The inlet (A1$#) and outlet (A1$5) conductivit+ values were

recorded at interval -$ seconds.#5. (A1$#) and outlet (A1$5) conductivit+ values were recorded until

the+ are value almost constant and approachin low levels values.

.

O



Procedure:

#. The eneral start1up procedure were performed.5. =alve =N was opened and pump "# was switched on.-. "ump "# ow controller was adjusted to ive a constant ow rate of

de1ioni8ed water into the reactor R# at approximatel+ $$ml*min at T1

$#.:. The de1ioni8ed water was allowed to continue owin throuh the

reactor until the inlet (A1$#) and outlet (A1$5) conductivit+ values are

stable at low levels. !oth conductivit+ were recorded.J. =alve =N was closed and pump "# was switch o.M. =alve =## was opened pump "5 was switch on. The timer was started

simultaneousl+.

. The inlet (A1$#) and outlet (A1$5) conductivit+ values were recordedat interval -$ seconds.

O. (A1$#) and outlet (A1$5) conductivit+ values were recorded until the+

are value almost constant and approachin low levels values.

N



Result

"ulse input experiment

TimePutletcond. 9(t) t9(t) L5 S-

$.$$ $.$$ $.$$$$ $.$$$$ $.$$$$ $.$$$$

$.$$ #.J$ $.-J$ $.$$$$ 5-.-:O5 1#O:.5-55

$.J$ #.$ $.O$$$ $.:$$$ :-.MN# 1-55.N:O

#.$$ #.:$ $.J$ $.J$ -M.NM 15J-.JJO#

#.J$ $.:$ $.:J$$ $.MJ$ #O.-O$ 1##.::5

5.$$ $.#$ $.#5J$ $.5J$$ :.--: 15J.JJ$5

5.J$ $.$$ $.$$$$ $.$$$$ $.$$$$ $.$$$$

Summation 5.J5J$ 5.#$$$ #5M.JJO- 1N$-.-M-5$5


∞

t ( E )dt

Second moment' =ariance' L5 E ∫

0

∞

(t −tm ) ᴧ 2 ( E )t dt

Third moment' S,ewness' s- E #* L-*5 ∫0

∞

(t −tm ) ᴧ 3 ( E )t dt

#$



$.$$ $.J$ #.$$ #.J$ 5.$$ 5.J$ -.$$$.$$

$.5$

$.:$

$.M$

$.O$

#.$$

#.5$

#.:$

#.M$

#.O$

outlet conductivit+ aainst time

time

outlet conductivit+

$.$$ $.J$ #.$$ #.J$ 5.$$ 5.J$ -.$$$

$.#$.5

$.-

$.:

$.J

$.M

$.

$.O

$.N

E&t' a#ainst time

Time

9(t)

##



T"e result (or step c"an#e experiment

Time Putlet 4(t) 9(t) tm L5 S-

$.$$ $.$$$ $.$$$$ $.$$$$ $.$$$$ $.$ $.$$.J$ $.$$$ $.$$$$ $.$$$$ $.$$$$ $.$ $.$#.$$ $.$$$ $.$$$$ $.$$$$ $.$$$$ $.$ $.$#.J$ $.J$$ $.5J$$ $.#5J$ $.$#O# $.$ $.$5.$$ #.J$$ $.J$$ $.J$$$ $.$NMM $.5 $.-5.J$ #.N$$ $.NJ$$ $.OJ$$ $.5$J- $.: #.$-.$$ 5.#$$ #.$J$$ #.$$$$ $.5ONN $. #.N-.J$ 5.-$$ #.#J$$ #.#$$$ $.-5$ #.$ -.-

:.$$ 5.:$$ #.5$$$ #.#J$ $.:J:# #.: J.#:.J$ 5.:$$ #.5$$$ #.5$$$ $.J5# #.O .-J.$$ 5.J$$ #.5J$$ #.55J$ $.JN#O 5.- #$.#J.J$ 5.J$$ #.5J$$ #.5J$$ $.MM:- 5.O #-.M.$$ 5.M$$ #.-$$$ #.5J$ $.-N# -.: #.N

Summation#$.-J$

$ N.$$$ -.NJ5N #:.M M$.M

$.$$ #.$$ 5.$$ -.$$ :.$$ J.$$ M.$$ .$$$.$$$

$.J$$

#.$$$

#.J$$

5.$$$

5.J$$

-.$$$

Putlet conductivit+ aainst Time

Time

Putlet conductivit+

#5



$.$$ #.$$ 5.$$ -.$$ :.$$ J.$$ M.$$$.$$$

$.#$$

$.5$$

$.-$$

$.:$$

$.J$$

$.M$$

$.$$

$.O$$

9(t) aainst time

Time

9(t)

ample calculation

or pulse input

∫0

∞

C (t ) dt =areaunder the graph

/rea E (t51t#)Bf(t)# f(t)5B*5

or time (#.$1#.J) minutes

E (t51t#)Bf(t)# f(t)5B*5

E (#.J C #.$) B #. #.:B*5

E $.J

or time (5.$1#.J) minutes

(#.J C #.$) B #.: $.:B*5

∫0

∞

E (t )dt =areaunder the graph

E 5.#J

#-



Residence time' tm E ∫0

∞

tE (t ) dt

E .ON$M min


∞

tE (t )dt E M.JM5J min

S,ewness E 1O.#$#J

or step chane

∫0

∞

C (t ) dt =areaunder the graph

/rea E (t51t#)Bf(t)# f(t)5B*5

or time (#.J C 5.$) minutes

E (t51t#)Bf(t)# f(t)5B*5

E (#.J C 5.$) B $.J #.JB*5

E $.J$$$

or time (5.$1#.J) minutes

(#.J C #.$) B #.: $.:B*5

∫0

∞

E (t )dt =areaunder the graph

E 5.#J

Residence time' tm E ∫0

∞

tE (t ) dt

E .ON$M min

#:




∞

tE (t )dt E M.JM5J min

S,ewness E 1O.#$#J

or step chane'

So based on result' area is #$.-J example of calculation at 5.$$ min

tmE (t x 9(t))*area

E (5.$$ x $.J )*#$.-J

E$.$NMM min

L5E ((t1 tm)59(t))*area

E ((51$.$NMM )5x $.J)* #$.-J

E $.5

S- E ((t1 tm)-9(t))*area

E ((51$.$NMM)-x $.J)* #$.-J

E $.-

#J



)iscussion

The objective of this experiment is to determine the eect of pulse

input and step chane in a tubular reactor and also to construct the

residence time distribution (RTD) function for tubular reactor at the end of

the experiment. !+ referrin to formula =R*A/E Kd4/*r/ ' the raph was 9(t)

C 4(t) * ∫0

∞

t ( E )dt in order to plot the 9(t) aainst time. Then' the 9 (t) was

plotted as a function of time. This is the residence time distribution (RTD)

function for the plu ow reactor.

Pn the other hand' we use the raphical method to determine 9(t) for

step input. !+ application of numerical method which is called trape8oidal

method' in 0ndin the area under the curve. or application of this method'

there man+ error ma+ occur while tr+in the to 0nd the dierentiation of

conductivit+. Fhen comparin the RTD function plot between experiment #

and 5' we can see the dierentiation based on raphs constructed above.

The most important parameters that characteri8e a curve raph are the

mean time which indicates when the wave of tracer passes the measurin

point and the variances which indicates how much tracer has spread out

durin the measurin time. /s we compare the pulse input and the step

chane' we can see that the pulse input iven hiher mean time but lower

variances. So we can conclude that the time' for a short interval (%impulse

#M



function&) or at a selected instant' a sudden chane from one feed to the

other is made for a continuous period (%step function&) and the concentration

chanes with time in each vessel is measure and pulse input poses input

process was faster than step chane.

This can be seen in result tabulated above and these formula was used

mean residence time' tm E ∫0

∞

t ( E )dt ' second moment' variance' L5 E

∫0

∞

( t −tm ) ᴧ 2 ( E )t dt . /s this experiment need to calculate the area under the

raph in order to et the result so the s,ewness of the raph need to be

calculated also. The s,ewness of the raph is about the s+mmetr+

distribution of the raph. So this formula was used' Third moment'

S,ewness' s- E #* L-*5 ∫0

∞

(t −tm ) ᴧ 3 ( E )t dt . or pulse input ' mean residence

time M.JM5J min' variance #5M.JJO- ' s,ewness of the raph 1O.$#$J . or

step chane ' mean residence time -.NJ5N min ' variance #:.M' s,ewness of

the raph M$.M. The result of this experiment miht not become ood result

due to errors had occurs durin conductin the experiment.

The advantaes of usin the Tubular plu ow reactor are it has hih

volumetric unit conversion' it can run for a lon period of time with

maintenance and the heat transfer can be optimi8ed b+ usin tube parallel

while the advantaes of usin this reactor are the temperatures are di7cult

to control' variabilit+ of products which mean the input product miht be the

same as the operatin cost.

!onclusion

#



rom the experiment' the eect of the pulse input and he step chane

in tubular ow reactor can be dierentiate. !esides' we also can construct

the residence time distribution (RTD) function for tubular ow reactor. The

dierences between these experiment is either for a short interval (%impulse

function&) or at a selected instant' a sudden chane from one feed to the

other is made for a continuous period (%step function&) and the concentration

chanes with time in each vessel was measured. rom the result' pulse input

poses input process was faster than step chane. or pulse input' mean

residence time M.JM5J min' variance #5M.JJO- ' s,ewness of the raph

1O.$#$J . or step chane' mean residence time -.NJ5N min' variance #:.M'

s,ewness of the raph M$.M. The raph for outlet conductivit+' 4 (t) aainst

time and distribution of exit time' 9(t) aainst time was plotted. The raph

plotted almost the same as stated in the theor+' 9(t) is depends on the value

4(t).

#O



Recommendation

n order to et the accurate result' the procedure should be followed

accuratel+. The pump and the valve should be opened simultaneousl+' for

example valve ## and pump 5 should be opened simultaneousl+. or time

ta,en b+ stopwatch' the time cannot be stopped inaccurate time because

the data miht not consistent. The experiment should be handle at the

stable or unsha,en place. ;a,e sure that there is no lea,ae in the

experiment.

Re(erences

1$ H. Scott Fogler, Element of Chemical Reaction, 4th edition, Pearson, United States of

America.

5. Steven 4. 4hapra' Ra+mond ". 4anale' Qumerical ;ethod for

enineers ;craw 6ill' sixth edition' /merica' Qew or,.-. https@**www.oole.com.m+*wsUrdEsslV2

#N

https://www.google.com.my/?gws_rd=ssl#q

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APPE*)I+

5$



The tubular ow reactor used in the pilot plant.

The students are recordin the data of the experiments.

5#

Documents

Tubular Plug Fow Reactor