Upload
muhamad-baihakhi-shamsudin
View
237
Download
0
Embed Size (px)
Citation preview
8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1
1/15
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$
8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1
2/15
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
8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1
3/15
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
8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1
4/15
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+ '-.-!
8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1
5/15
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
8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1
6/15
:$ 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$
$
8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1
7/15
-$ 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
8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1
8/15
-.. -.. @ $? @$@ .$:
@. @. @ @$? =$? .$:
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;
=.$.... @.$= .$:@=. $:=>> x -.6=
.0 -a%("e of a"cu"ations
.1 Residence Ti%e
or flow rates of ;.. mlCmin +
)esidence Time,
τ = Reactor volume ( L ) ,V
Total flow rate
( L
mi
), v
0
Total flow rate,
8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1
9/15
8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1
10/15
9unreacted
9unreacted FCocetratio of %a&! ureacted
cocetratio%a&!
F0.0494
0.1
F .$=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 )
or flow rates of ;.. mlCmin +
8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1
11/15
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!:
or flow rates of ;.. mlCmin +
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 -
8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1
12/15
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 +
8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1
13/15
8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1
14/15
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 :.-;!
8/18/2019 Docslide.net Plug Flow Reactor 562e624f0b2e1
15/15
13.0 A((endi/