Docslide.net Plug Flow Reactor 562e624f0b2e1

8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1

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1.0 Abstract

The conduction of this experiment is based on a few targets, namely to carry out

saponification reaction between Sodium Hydroxide, NaOH and Ethyl Acetate, Et(A!, to

determine the effect of residence time to the reaction"s extent of con#ersion and lastly to

e#aluate the reaction rate constant of this particular saponification reaction$ To achie#e these

targets, an experiment is finely designed so much so that these targets can be finely met$ Such

experiment in#ol#es using a unit called SO%TE& 'lug low )eactor (*odel+ ' -.-!,

commonly /nown as '), as well as some common laboratory apparatus for titration process$

To put it simply, the two solutions Sodium Hydroxide, NaOH and Ethyl Acetate, Et(Ac! were

reacted in the ') and the product is then analysed by the method of titration to determine

how well did the reaction go$ Hence, the experiment was conducted and the results shows that

the amount of con#ersion of Sodium Hydroxide, NaOH is almost unchanged as residence

time increases$ urther details can be obtained in the results and discussion sections$


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2.0 Introduction

Type of chemical reactors remains a highly discussed sub0ect in chemical process industries

worldwide$The reactor is of course, the place where chemical reactions ta/e place$ Hence it isarguably the single most important part of any chemical process design$ The design of a

reactor must be finely tuned so that its mechanisms suit the necesseties of the process that is

to be carried$ 1epends on the nature of the materials in both the feed and of course the

products, the reactors may ta/e a wide range of forms$ This is why full comprehension of a

reactor of a particular design as well as its wor/ing mechanisms is #ery much #ital to actually

conduct a particular chemical process$

2n this experiment, the 'lug low )eactor (*odel+ '-.-! is used as it has been properly

designed for students" experiment on chemical reactions in li3uid phase under isothermal and

adiabatic conditions$ 2ncluded in the unit is a 0ac/eted plug flow reactor4 indi#idual reactantfeed tan/s and pumps, temperature sensors and conducti#ity measuring sensor$ y using this

particular unit, students will be capable to conduct the typical saponification reaction between

ethyl acetate and sodium hydroxide among the others reaction$

3.0 Objectives

This experiment is conducted to study the effects of residence time on a reaction by using a

'lug low )eactor$ Also, reaction rate constant is also to be determined by saponificationreaction between Sodium Hydroxide, NaOH and Ethyl Acetate, Et(Ac!$

4.0 Theory

4.1 Rate of Reaction and Rate Law

Simply put, rate of reaction can be roughly defined as the rate of disappearance of reactants or

the rate of formation of products$ 5hen a chemical reaction is said to occur, a

reactant(or se#eral! diminishes and a product(or se#eral! produced$ This is what constitutes a

chemical reaction$ or example +

aA+bB→

cC +dD

where A and represent reactants while and 1 represent products$ 2n this reaction, A and

is being diminished and and 1 is being produced$ )ate of reaction, concerns itself with how

fast the reactants diminish or how fast the product is formed$ )ate of reaction of each species

corresponds respecti#ely to their stoichiometric coefficient$ As such +

−r A

a

=

−rB

b

=

rC

c

=

r D

d


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The negati#e sign indicates reactants$

A usual e3uation for r A is +

−r A=kC Aα C B β

where

/ 6 rate constant

A 6 concentration of A species

6 concentration of species

7 6 stoichiometric coefficient of A

8 6 stoichiometric coefficient of

4.2 onversion

Ta/ing species A as the basis, the reaction expression can be di#ided through the

stoichiometric coefficient of species A, hence the reaction expression can be arranged as

follows +

A+

b

aB+

c

aC +

d

a D

on#ersion is an impro#ed way of 3uantifying exactly how far has the reaction mo#ed, or

how many moles of products are formed for e#ery mole of A has consumed$ on#ersion 9A is

the number of moles of A that ha#e reacted per mole of A fed to the system$ As seen below +

X A=molesof Areacted

moles of A fed

4.3 !"u# $"ow Reactors

This reactor also /nown as tubular flow reactor whic is usually used in industry

complementary to ST)$ 2t consists of a cylindrical pipe and is usually operated at steady

state$ or analytical purposes, the flow in the system is considered to be highly turbulent and

may be modeled by that of a plug flow$ Therefore, there is no radial #ariation in concentration

along the pipe$

2n a plug flow reactor, the feed enters at one end of a cylindrical tube and the product stream

lea#es at the other end$ The long tube and the lac/ of pro#ision for stirring pre#ent complete


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mixing of the fluid in the tube$ Hence the properties of the flowing stream will #ary from one

point to another$

2n an ideal tubular flow reactor, which is called plug flow reactor, specific assumptions aremade regarding the extent of mixing+

-$ no mixing in the axial direction

:$ complete mixing in the radial direction

;$ a uniform #elocity profile across the radius$

Tubular reactors are one type of flow reactors$ 2t has continuous inflow and outflow of

materials$ 2n the tubular reactor, the feed enters at one end of a cylindrical tube and the

product stream lea#es at the other end$ The long tube and the lac/ stirring pre#ent complete

mixing of the fluid in the tube$

4.4 Residence Ti%e &istribution $unction

)esidence Time 1istribution is a characteristic of the mixing that occurs in the chemical

reactor$ There is no axial mixing in a plug flow reactor, ') and this omission can be seen in

the )esidence Time 1istribution, )T1 which is exhibited by this class of reactors$ The

continuous stirred tan/ reactor ST) is thoroughly mixed and its )T1 is hugely different as

compared to the )T1 of ')$

'.0 A((aratus)*ateria"s

The unit used in this experiment is SO%TE& 'lug low )eactor (*odel+ '-.-!


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SOLTEQ Plug Flow Reactor (Model: BP101)

'lug low )eactor (*odel+ '-.-! is used as it has been properly designed for students"

experiment on chemical reactions in li3uid phase under isothermal and adiabatic conditions$

2ncluded in the unit is a 0ac/eted plug flow reactor4 indi#idual reactant feed tan/s and pumps,

temperature sensors and conducti#ity measuring sensor$

Apart from that, there were also some laboratory apparatus in#ol#ed such as +

• burette

• conical flas/

• measuring cylinder

• ph indicator

• bea/ers

Among the chemicals used are +

• .$- * Sodium Hydroxide, NaOH

• .$- * Ethyl Acetate, Et(Ac!

• .$- * Hydrochloric Acid, Hl

• 1e6ionised water

+.0 *ethodo"o#y)!rocedures

+.1 ,enera" -tartu( !rocedures

-$ All the #al#es are ensured closed except


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:$ The following solutions are prepared+

:. liter of NaOH (.$-*!

:. liter of Et(Ac! (.$-*!

- liter of H% (.$:@*! for 3uenching

;$ eed tan/ - was filled with NaOH while feed tan/ : was filled with the Et(Ac!$

=$ The water 0ac/et = was filled with water and pre6heater @ was filled with clean water$

@$ The power for the control panel was turned on$

$


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-$ The burette was filled up with .$- * NaOH solution$

:$ -. m% of .$:@ * Hl was poured in a flas/$

;$ @. m% samples that were collected from the experiment at e#ery controlled flow rate (;..,

:@., :.., -@., -.. and @. m%Cmin! were added into the -.m% Hl to 3uench the

saponification reaction$

=$ ; drops of phenolphthalein were dropped into the mixture of sample and Hl$

@$ The mixture then was titrated with NaOH until it turns light pin/$

$ The amount of NaOH titrated was recorded$

.0 Resu"ts

)eactor


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-.. -.. @ $? @$@ .$:

@. @. @ @$? =$? .$:

Table :)esidence Time,

D, (min!

on#ersion, 9,

(!

)eaction )ate onstant,/

(%$molCmin!

)ate of )eaction, 6r A

(mol$%Cmin!

$? @.$ -$@;@ ;$?=B x -.6;

>$.... @.$= -$:?.- ;$-:= x -.6;

-.$.... @.$: -$..>. :$=BBB x -.6;

-;$;;;; @.$: .$?@. -$>?=B x -.6;

:.$.... @.$= .$@.>- -$:@.. x -.6;

=.$.... @.$= .$:@=. $:=>> x -.6=

.0 -a%("e of a"cu"ations

.1 Residence Ti%e

or flow rates of ;.. mlCmin +

)esidence Time,

τ = Reactor volume ( L ) ,V

Total flow rate

( L

mi

), v

0

Total flow rate,


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9unreacted

9unreacted FCocetratio of %a&! ureacted

cocetratio%a&!

F0.0494

0.1

F .$=B=

9reacted

9reacted F - 6 9unreacted

F - 6 .$=B= F .$@.

on#ersion for flow rate ;..m%Cmin

.$@. x -.. F @.$ placed in Table :

Hence, at flow rate ;..m%Cmin of NaOH in the reactor, about @.$ of NaOH is reacted with

Et(Ac!$ Other con#ersions were calculated by the same way, and #arying the flow rates$

.3 Reaction Rate onstant

k =v0

V T'RC A& ( X

1− X )



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k = 0.6

(4)(0.1) ( 0.506

1−0.506 ) F -$@;@%$molCmin placed inTable :

Other )eaction )ate onstants were calculated by the same way, and #arying the flow rates$

.4 Rate of Reaction rA

6r A F / (A.!: (-69!:


6r A F -$@;@ (.$-!: (-6.$@.!:

F ;$?=B x -.6; mol$%Cmin placed in Table :

Other )ate of )eactions were calculated by the same way, and #arying the flow rates$

5 10 15 20 25 30 35 40 45

40

42

44

46

48

50

52

54

56

58

60

Conversion vs Residence Time

Residence Time, min

Conversion, %

igure -


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5.0 &iscussions

'lug low )eactor(')! is a type of reactor that consists of a cylindrical pipe and is usually

operated at steady state$ 2n a plug flow reactor, the feed enters at one end of a cylindrical tube

and the product stream lea#es at the other end$ The long tube and the lac/ of pro#ision for

stirring pre#ent complete mixing of the fluid in the tube$ Hence the properties of the flowing

stream will #ary from one point to another$ The fluid in ') is considered to be thin, unmixed

layer of #olume segments or "plugs", hence the name$

igure : + courtesy of wi/ipedia$com

As seen in figure :, the solution in the tube is treated as a series of layers of #olume segments

that are unmixed with the segment before and after it$ %i/e a series of plugs, stac/ed together

in a pipe$

2n this particular experiment, the solutions used are NaOH and Et(Ac!$ These two solutions

reacts together in the ') to complete saponification reaction$ The main ob0ecti#e of this

particular experiment is to study the effect of residence time on the performance of this

reactor, the ')$ To do that, of course, residence times ha#e to be manipulated throughout

the experiment, and the effects of each one is studied$ )esidence time, in this particular

experiment, is #aried by the means of changing the flow rates of the feed solutions$ This is

shown by the formula +


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11.0 Reco%%endations

-$ 2t is better to time the sample well so that time6wasting in ta/ing samples can be reduced or,

if possible, a#oided$

:$ All #al#es should be properly placed before the experiment started$

;$ low rates should be constantly monitored so that it remains constant throughout the

reaction, as needed$

=$ Titration should be immediately stopped when the indicator turned pin/$

@$ 'umps should ne#er be run dry$

12.0 References

-$ ogler, H$S (:..!$ Elements of hemical )eaction Engineering (;rd Edition!$ 'rentice

Hall$

:$ %e#enspiel, O$ (-BBB!$ hemical )eaction Engineering (;rd Edition!$ Iohn 5iley$

;$ %aboratory *anual Tubular low )eactor$

=$ The 'lug low ()etrie#ed from http+CCwww$/onferenslund$seCpC%-$pdf on ->th October

:.-;!

@$ )eaction Jinetics ()etrie#ed from http+CCsm/;ae$files$wordpress$comC:..?C-.Crea/si6

/ineti/$pdf on the ->th October :.-;!


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13.0 A((endi/

Docslide.net Plug Flow Reactor 562e624f0b2e1

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