School of Chemical Engineering & Advanced Materials Module title: Engineering Practice (CME2121) Laboratory experiment: Continuous Stirred Tan Tan !eactor
"roup no#: 2$ "roup members: %arren Tang (1&'1'2) ac*ueline Tan (1&'12'') Tan +i ,iu (1&'1222) Submission %ate: anuary 2'1-
Summary
Safety .a/ard identi0ication is important be0ore starting any experiment# Te a/ards ill be circled out and recorded don# Tese3 along it te C4S.. 0orm and !is 5ssessment 0orm are to be assessed as sessed and 6eri0ied 6eri0ie d by b y te lab tecnician3 be0ore deciding eter it is sa0e to carry carr y on it te experiment# Hazard Identification and Mitigation
S/N
Wor Activity
!y"e of Hazard
Spill3 7ire
#ossi$le conse%uences to user if not mitigated
'
Preparation o0 solutions
8nalation98ngestio n to user
(
4peration o0 PC3 e*uipment
Electrical
)
Ensure all drain points are closed
Electrical soc3 Spills3 electrical possible inalation a/ard o0 6apor 0umes
*
5dding9!e0illing solution into CST! tan
Spills
8rritation to sin3 electrical soc to user
+
Taing readings using te probes
Spills3 electrical a/ard
8rritation to sin3 electrical soc
Electric Soc to user
Table Table 1#1: Te identi0ied a/ards a/ar ds 0or te CST! experiment#
Refer to Appendix G for detailed Risk Assessment Assessment table.
is Controls
Ensure tat proper PPE suc as glo6es are orn and a6oid contact o li*uids to be andled near tem Cec tat drain points are closed be0ore commencing experiment Ensure pouring and introduction o0 material into tan is done sloly Ensure no exposed ires and ensure glo6es are orn#
is Assessment
Te to solutions used 0or tis experiment are Sodium .ydroxide and Etyl 5cetate# Taing tem togeter ill 0orm sodium acetate# Sodium ydroxide is an irritant and a/ardous in te case o0 sin contact# 8t is easily soluble in ater oe6er it is ygroscopic in nature3 in ic it generates eat upon contact it ater# 8n te case o0 a spill3 use appropriate tools suc as acetic acid to neutrali/e and dispose o0 it3 and a6oid ater contact at all costs# Etyl 5cetate is a clear3 colourless li*uid tat is 0lammable in nature# Prolonged exposure to tis cemical may cause irritation to te eyes and respiratory tract# Te 6apours gi6en o00 are denser tan air3 ence it is at a ris o0 tra6elling to an ignition source and 0lasbac# 8n te e6ent o0 a spill3 use a non;combustible absorbent to absorb te residue and dispose o0 it# Te e*uipm e*uipment ent as operate operated d under under 1atm (atmosp (atmosper eric ic pressur pressure) e) and at room room temper temperatu ature re (2-degC)# is Estimation Matri,
Severity of Harm
High
Medium
Low
Severe
High
High
Medium
Moderate
High
Medium
Medium/Low
Minor
Medium/Low
Low
Low
Efectively Zero
Efectively Zero
Efectively Zero Table Table 1#2: !is estimation esti mation matrix
Negligible
Negligible Efectively Zero Efectively Zero Efectively Zero Efectively Zero
!a$le of Contents Cont ents 1# 8ntroduction 8ntroduction and Teoretical Teoretical
# E*uipment#########=##############=############## E*uipment#########=##############=##############=####################### =############################################## ###########################=##############=###> ####=##############=###> !esults =################=################=############# =################=################=################=###############=##### ###=###############=#################=########### ############=#########################& ##############& -# %iscussion %iscussion ============ ================== =========== =========== ======##### ########## Conclusion Conclusion====== ============ =========== =========== ============ ======== == $# %ata and Error 5nalysis= 5nalysis======= ============ ============ ========#=== ==#====##$ =##$ ?# !e0erences==== !e0erences========== ============ ============ ============ ========### ==####? #? @# omenclature omenclature ============ ===============## ===##====== ============ ========@ ==@ 1'# 5ppendix===============================1'
'- Introduct Introduction ion and !heoretical !heoretical .acground .acground '-' EAC!IN CS! EAC!IN IN CS
Continuous Stirred Tan !eactor (CST!) is te most 0undamental continuous reactor used in cemical processes# %uring te operation3 reactants are 0ed continuously into te reactor and te contents o0 te tan are assumed to be ell mixed by te agitator# Te products are ten remo6 remo6ed ed cont contin inuo uous usly ly 0rom 0rom te te reacto reactor# r# Te Te CST! CST! is comm common only ly used used in indu industr strial ial processing3 mainly in omogenous li*uid;pase 0lo reactions ere agitation is re*uired# 8n tis experiment3 te reaction occurring itin te reactor is saponi0ication ic is gi6en by te 0olloing 0irst order reaction: a4. A a
.>C244C2.-
B
.2C44a
A
C2.-4.
A
B
c
A
d
b
Te reactants are Sodium ydroxide (a) and Etyl 5cetate (b)3 react to 0orm Sodium 5cetate (c) and Etyl Etyl 5lcoo 5lcooll (d)#
Te reaction reaction as carried carried out at constant constant temperatu temperature3 re3 6olume3 6olume3
0lo rate and concentration o0 reagents under per0ect mixing in CST! to acie6e steady state and optimal con6ersion#
'-( CNCEN!A!INS 0 EACH S#ECIES
Te con6ersion tat is associated it te solution conducti6ity can be acie6ed troug te use o0 0olloing e*uations: Te inlet concentration o0 eac reactant is calculated by te 0olloing e*uations:
[ a]
0=
F a F a+ F b
× [ a ]µ
(1)
[ b]
0=
F b F a+ F b
× [ b ]µ
(2)
Te outlet concentration o0 te species is as 0ollos:
[ c ] =[ b ] X b 1
0
(>)
[ a]
1
=[ a ]0− [ b ] 0 X 0
(&)
for [ b ] 0< [ a ] 0
[ c ] =[ a ] X a 1
[ a]
1
(-)
0
=[ a ]0 1− X a
(
)
()
for [ a ] 0< [ b ] 0 ote tat te e*uations to use depends on ic reactant is limiting reagent#
'-) CN12C!I3I!4
Te e*uations (>)3 (&)3 (-) and () are combined to gi6e an e*uation tat sol6es 0or , a 0rom a measured 6alue o0 conducti6ity# Te conducti6ity o0 te solution is used to obtain con6ersion itin te reactor# 7rom te reaction3 te conducti6ity o0 te mixture is contributed by sodium ydroxide (a) and sodium acetate (c)# Tere is no conducti6ity 0or etyl acetate and etyl alcool as te contents do not contain ions# Te conducti6ities o0 pure solutions (a) and (c) it teir concentrations are gi6en by:
[
(
k a =0.195 1+ 0.0184 T − 294
) ]∗[ a ]
k c = 0.07 [ 1 + 0.0284 ( T −294 ) ] ∗[ c ]
($)
(?)
WhenT > 294 Te conducti6ity o0 mixture is determined by te sum o0 e*uations $ and ?:
k =k a + k c
'-* CN3ESIN AN1 A!E CNS!AN!
sing te 0olloing e*uations to obtained te optimal con6ersion:
(@)
X a , 1=
k 1−0.195 [ 1+ 0.0184 ( T −294 ) ] [ a ] 0
{0.070 [ 1 + 0.0284 ( T −294 ) ]−0.195 [ 1 + 0.0184 ( T −294 ) ] } [ a ] 0
(1') E*uation 1' is 0ormed by manipulating te e*uations $3 ? and @# Te concentration terms is ritten in terms o0 con6ersion3 , a and , b depending on ic reactant is te limiting reagent#
d ( V [ [ a ]1 ) dt
= F [ a ] − F [ [ a ] −Vk [ [ a ] [ b ] 0
1
1
(11)
1
Since te continuous reactor runs under steady state condition3 tere is no cange to te 6olume and ence3 te e*uation 11 is rearrange to 0ind te rate constant D#
F ( [ a ]0 −[ a ] 1 ) k = V [ a ]1 [ b ] 1
(12)
(- E,"erimental 1esign and Method Continuous Stirred Tan !eactor (CST!) as used to conduct pilot scale experiment on te reaction o0 sodium ydroxide and etyl acetate# Te 0lo rates ere cosen to be >2ml9min3 -2ml9min and $2ml9min 0or bot te pump settings# 5t 0lo rate >2ml9min3 te conducti6ity and temperature ere recorded at e6ery > minutes inter6al and at -2ml9min and $2ml9min3 te readings ere taen don at e6ery 1 minute inter6al# Eac run too about >' minutes 0or at least 1' readings#
(-' #E#AA!IN 0 S!C5 S62!INS S!C5 S62!INS
5s te conducti6ity sensor sould not be exposed to concentrations tat exceed '#'-M o0 a4. and '#1M o0 .>C244C2.-3 te reagent concentrations o0 '#'>M and '#'-M 0or a4. and .>C244C2.- are used respecti6ely# Te a4. and .>C244C2.- stoc soluti solutions ons ere prepared prepared by adding adding 2#&g o0 a4. a4. solids solids and @#$ml @#$ml o0 .>C244 .>C244C2. C2.solutions it te deionised ater into 2L 6olumetric 0las# Similarly3 te .>C244C2.stoc solution as made by trans0erring @#$ml o0 .>C244C2.- solution it deionised ater into 2L 6olumetric 0las#
(-( S!A!72# E8#EIMEN!
5t te start o0 te experiment3 te taps 0or te 0eed tans and CST! ere closed to pre6ent leaage o0 solutions# Ten3 2L o0 eac sodium ydroxide and etyl acetate solutions ere poured into te respecti6e res pecti6e tans# ext3 te de0ault readings 0or conducti6ity and temperature ere recorded by placing placing te probe and termocoup termocouple le into te 0eed tans 0or measurement# measurement# 4nce te readings ere taen don3 te probe and termocouple as placed bac into te reactor# Te main poer as sitced on 0olloed by te pumps 5 and < as ell as te impeller# Te temperature control as turned on only a0ter te solution as 0illed up te termocouple# Ten3 te pumps ere adusted to desired 0lo rates tat ad acie6ed a minimum o0 1' readings per run as te temperature reaced >' oC# Eac reading as recorded at an inter6al o0 at least 1 minute inter6al 0or te system to reac steady;state# Te procedure is repeated 0or oter 0lo rates# 7eed tans ere re0illed it reactant solutions tice#
(-) SH2!1WN E92I#MEN!
50ter collecting all te experiment data3 te pumps and impeller sitces ere turned o00 0ollo by te main poer sitc# Te recorded data ill be used 0or discussion on te discrepancies beteen te publised 6alues and experimental 6alues#
)- E%ui"ment [Insert Picture here]
Te reactor is made up o0 se6eral components: i)
To 0ee 0eed tan ans: To sto store te solu soluttion ions#
ii) ii)
To peris peristal taltic tic pum pumps ps 5 and and <: To To pum pump p te ce cemi mical calss into into te rea reacto ctorr it it indi6 indi6id idual ual manu manual al speed controls#
iii) iii)
!eact !eactor or 6esse 6essel: l: Con Consis sistt o0 o0 impel impeller ler tat tat ens ensur uree goo good d mixi mixing ng o0 reacta reactant nts# s#
i6) i6)
Ter Termo moco coup uple le:: To To cont contro roll te te reac reacto torr tem tempe pera ratu ture re##
6)
Cond Conduc ucti ti6i 6ity ty prob probe: e: To mea measu sure re te te solu soluti tion on cond conduc ucti ti6i 6ity ty##
6i) 6i)
.ot9 .ot9Co Cold ld Fa Fater cir circul culati ation on:: 7luid 7luid ta tatt 0los 0los tro troug ug eati eating ng9co 9cooli oling ng coil coils# s#
6ii) 6ii)
Cond Conduc ucti6 ti6ity ity mete meter: r: To To disp display lay te te cond conduc ucti6 ti6ity ity meas measur ured ed by te te prob probee
6iii) 6iii)
Tempera emperature ture meter: meter: To To display display te temp temperat erature ure measu measured red by by te te termo termocou couple ple
*- esu esult ltss
+- 1iscus 1iscussio sion n +-) A!E A!E CNS!AN! 5
Te rate constants are calculated by te 0olloing e*uation:
F ( [ a ] 0−[ a1 ] ) k = V [ a ] 1 [ b ]1 No- of runs 56erage 56erage 7lo rate
(L9s) Average !em"erature :oC; !em"erature !ate Constant3
(-#>#1)
un '
un (
un )
'#'''->>
'#'''?-@
'#''11?
>2#@
>>#&
>2#>
(L9mol# s) '#'1'#'2? Table -#>#1: Experimental rate constant at 6arious a6erage 0lo rates
'#'-'$
Refer to appendix C for detail calculation of rate constant constant k. Source
Smith et al- <ef=
!ate Constant3 (L9mol# s) '#11 Table -#>#2: !ate constant at steady state extracted 0rom te literature
Te experimental rate constants are obtained troug te calculation using te e*uation -#># 7rom 7rom table table -#>#13 -#>#13 an increas increasing ing trend o0 experim experimenta entall rate rate consta constants nts is obser6 obser6ed ed as te a6erage 0lo rates increase# %uring steady;state3 te experimental rate constants are expected to be constant 0or te > runs oe6er3 te 6alues de6iate 0rom eac oter due to se6eral experiment errors# Te 0luctuation o0 0lo rates could be due to te inconsistent o0 peristalsis pumps as it migt a00ect te actual set point o0 0lo rates# Te inaccurate 0lo rates ill indirectly a00ect te concentrations ic in turn cause te rate constants to de6iate#
.oe6er3 te teoretical rate constant only depends on te temperature tere0ore3 te 6alue is more reliable# 5ccording to te literature3 te teoretical rate constant is abstracted to be '#11 L9mol#s at steady state# Te teoretical rate constant is correlated to temperature and te relationsip is represented repres ented by 5rrenius la: − Ea
k = Ae RT
(-#>#2)
Te exponential term tat consists o0 te ratio o0 acti6ation energy E to te a6erage inetic energy as signi0icant in0luence on te rate constant# 5s te rate constant depends on te temperature3 it can be in0er tat ig temperature and lo acti6ation energy 0a6our larger rate constant3 and tus increase te rate o0 reaction# Teoretically3 te rate constant can be deri6ed by 5rrenius la# Te de6iation beteen te experimental 6alue and teoretical 6alue is due to te di00erent e*uations (-#>#1 and -#>#2) being used# Te experimental 6alue is calculated based on te concentrations ereas te teoretical 6alue is deri6ed based on temperature#
+-' +-'
Nomenclature 7a
Golume 0eed rate o0 sodium ydroxide
L9s
7b
Golume 0eed rate o0 etyl acetate
L9s
HIJK
Sodium ydroxide concentration in 7eed Gessel
mol9L
HbJ K
Etyl acetate concentration in 7eed Gessel
mol9L
T
Temperature
D
G
Golume o0 te reactor
L
i
umber o0 moles o0 species i in te reactor
moles
6i
Stoiciometric Coe00icient
;
ri
!eaction rate
;
!esidence Time
s
!ate Constant
L9mol#s
5
Pre;Exponential 0actor
;
Ea
5cti6ation energy
9mol
!
"as Constant
9mol#D
''- A""end A""endi, i, A> A> E,"e E,"erim riment ental al 1esig 1esign n Calc Calcula ulatio tion n ''-' CA6C26A!IN 0 !HE 0 !HE MASS 0 NAH #E66E! 0 S!C5 0 S!C5 S62!IN S62!IN
Molar Concentration Concentration of NaOH = 0.03 mol / Molec!lar "ei#ht of NaOH =40 # / mol Ma$$ of NaOH %ellet =40 × 0.03 × 2=2.4 #
11.2 CA6C26A!IN 0 !HE 0 !HE 362ME 0 H)C(C(H+ 0 S!C5 0 S!C5 S62!IN S62!IN
3 C 2 OOC 2 2 H 5 5 =0.05 mol / Molar Concentration Concentration of H 3 3 C 2 OOC 2 H 5 5 =88 # / mol Molec!lar "ei#ht of H 3
Concentr Concentrationof ationof H 3 C 2 OOC 2 H 5 $ol!tion=0.05 × 88 =4.4 # / &en$it' of H 3 3 C 2 2 OOC 2 H 5 5 $ol!tion =0.901 # / Vol!meof H 3 C 2 OOC 2 H 5 =
4.4 ma$$ × 2 =9.76 ml = den$it' 0.901
''''- A""endi, .> esults ''-' AW AW 1A!A A!A !ime :min;
Conductivity :mS/cm;
!em"erature : C;
un ' 0lo?rate :ml/min; #um" A> )( #um" .> )(
' > @ 12 11? 21 2& 2$ >'
>#$2 >#> >#>@ >#2 >#2' >#1$ >#1> >#1' >#12 >#'$ >#'$
!ime :min;
Conductivity :mS/cm;
!em"erature : C;
un ( 0lo?rate :ml/min; #um" A> +( #um" .> +'
2#' >1#1 >'# >'#1 2@#@ >'#>'#2 >'#' >'#>'#2 >'#'
' 1 2 > & $ ? @ 1'
Table 11#1: !a %ata
''-( CNCEN!A!IN 0 A 3ES2S !IME
>#'? >#1>#1 >#1 >#1>#1> >#1' >#'? >#'$ >#'> >#'>
!ime :min;
Conductivity :mS/cm;
!em"erature : C;
un ) 0lo?rate :ml/min; #um" A> @( #um" .> @
2@#? >'#>'#$ >'#$ >'# >'#& >'#> >'#> >'#2 >'#1 >'#'
' 1 2 > & $ ? @ 1' 11 12 1> 1& 1-
>#'2 >#'>#' >#'>#'$ >#'& >#'> >#'1 2#@@ 2#@$ 2#@& 2#@> 2#@> 2#@ 2#@ 2#@-
>'#' 2@#@ >'#1 >'#>'#$ >'#>'#>'#> >'#2 >'#1 >'#' 2@#? 2@#@ 2@# 2@# 2@#-
'(- A""endi, A""endi, C> Sam"le Calculations '(-' CA6C26A!E !HE CNCEN!A!IN 0 S#ECIES IN 0EE1 3ESSE6S
8nitial conducti6ity o0 sodium ydroxide ydroxide (a4.): $#->mS9cm '#''$-> S9cm 8nitial Temperature (T') 2#& C 2@@#&D °
Concentration o0 a4.:
= '#1@-H1 + '#'1?&(T − 2@&)JH aJ '#''$-> = '#1@-H1 + '#'1?&(2@@#& − 2@&)JH aJ H aJ = '#'>- mol 9 L k a
µ
µ
µ
Concentration o0 etyl acetate in 0eed 6essel: '#'-mol9L'#'-mol9dm >
HbJ µ = '#'- mol 9 dm >
0lo? rates un ' Pump 5 (a4.) Pump < (Etyl acetate) un ( Pump 5 (a4.) Pump < (Etyl acetate) un ) Pump 5 (a4.) Pump < (Etyl acetate) Table 12#1: 56erage 0lo rates#
ml9min >2 >2
L9s '#'''->> '#'''->>
56erage (L9s)
-2 -1
'#'''?$ '#'''?-'
'#'''?-@
$2 $'
'#''12' '#''11$
'#''11@
'#'''->>
'(-( CA6C26A!IN 5 3A62E 5 3A62E AN1 CN3ESIN 0 2N 0 2N ' H aJ' F a F b
=
F a
+ F
F a
× HaJ
µ
b
= '#'''->> L 9 s = '#'''->> L 9 s =
'#'''->>
× '#'>- = '#'1$-mol 9 L '#'''->> + '#'''->> '#'''->> F b × HbJ µ = × '#'- = '#'2-mol 9 L HbJ' = '#'''->> + '#'''->> F a + F b H aJ'
= H aJ' X H aJ1 = H aJ' (1 − X ) k = '#'$H1 + '#'2?&(T − 2@&)JH c J k = '#1@-H1 + '#'1?&(T − 2@&)JH aJ L = '#'$H1 + '#'2?&(T − 2@&)J M = '#1@-H1 + '#'1?&(T − 2@&)J k = L H aJ' X k = M H aJ' (1 − X ) = M H aJ' − M H aJ' X k = k + k k = L H aJ' X + M H aJ' − M H aJ' X T = >'#1?°C + 2$> = >'>#1? K Hc J1
a
a
c
a
c
a
a
a
c
a
a
a
k
= >#'@?
X a
=
=
mS m S cm
a
1S
×
1''' mS k − M H aJ'
LH aJ'
= '#''>'@?
S cm
− M H aJ' '#''>'@? − '#1@-H1 + '#'1?&(>'>#1? − 2@&)J × ('#'1$-)
('#'$H1 + '#'2?&(>'>#1? − 2@&)J) × ('#'1$-) − ('#1@-H1 + '#'1?&(>'>#1? − 2@&)J) × ('#'1$-)
= '#>&& N '#>&
= HaJ' (1 − X ) = '#'1$-(1 − '#>&&) = '#'111mol 9 L HbJ1 = HbJ' − HaJ' X = '#'2- − ('#'1$- × '#>&&) = '#'1?2 mol 9 dm > F H aJ' − H aJ1 k = H aJ1HbJ1 '#'''->> '#'1$- − '#'111 = '#'111 × '#'1?2 1 = '#'1- L 9 mol • s HaJ1
a
a
'(-) CA6C26A!IN 5 3A62E 5 3A62E AN1 CN3ESIN 0 2N 0 2N ( H aJ' F a F b
=
F a
+ F
F a
× H aJ
µ
b
= '#'''?$ L 9 s = '#'''?- L 9 s
H aJ'
=
HbJ'
=
'#'''?$
'#'''?$ + '#'''?= '#'1$$mol 9 L F b F a
+ F
× HbJ = µ
b
× '#'>'#'''?-
'#'''?$ + '#'''?-
× '#'-
= '#'2&$mol 9 L k − M H aJ' X = LH aJ' − M H aJ' a
=
'#''>'2 − '#1@-H1 + '#'1?&(>'>#1? − 2@&)J × ('#'1$$)
('#'$H1 + '#'2?&(>'>#1? − 2@&)J) × ('#'1$$) − ('#1@-H1 + '#'1?&(>'>#1? − 2@&)J) × ('#'1$$)
= '#>$-= HaJ' (1 − X ) = '#'1$$(1 − '#>$--) = '#'11'>mol 9 L HbJ1 = HbJ' − H aJ' X = '#'2&$ − ('#'1$$ × '#>$--) = '#'1?'mol 9 dm > F H aJ' − H aJ1 k = H aJ1HbJ1 '#'''?-?- '#'1$$ − '#'11'> = '#'11'> × '#'1?' 1 = '#'2?2 L 9 mol • s H aJ1
a
a
'(-* CA6C26A!IN 5 3A62E 5 3A62E AN1 CN3ESIN 0 2N 0 2N ) HaJ' F a F b
=
F a
+ F
F a
× H aJ
µ
b
= '#''12' L 9 s = '#''11$ L 9 s
HaJ'
=
HbJ'
=
'#''12'
× '#'>-
'#''12' + '#''11$ = '#'1$$2mol 9 L F b F a
+ F
× HbJ = µ
b
'#''11$
'#''12' + '#''11$
× '#'-
= '#'2&$mol 9 L k − M H aJ' X = LH aJ' − M H aJ' a
=
'#''2@& − '#1@-H1 + '#'1?&(>'2#? − 2@&)J × ('#'1$$2)
('#'$H1 + '#'2?&(>'2#? − 2@&)J) × ('#'1$$2) − ('#1@-H1 + '#'1?&(>'2#? − 2@&)J) × ('#'1$$2)
= '#&2>? HaJ1 = H aJ' (1 − X ) = '#'1$$2(1 − '#&2>?) = '#'1'21mol 9 L HbJ1 = HbJ' − H aJ' X = '#'2&$ − ('#'1$$2 × '#&2>?) = '#'1$1@mol 9 dm > F H aJ' − H aJ1 k = H aJ1HbJ1 '#''11?- '#'1$$2 − '#'1'21 = '#'1'21 × '#'1$1@ 1 = '#'-'$1 L 9 mol • s a
a
Te obecti6es are to understand te limitations in assuming ideal CST! bea6iour and o tese can be minimised by controlling te operating conditions# 5lso3 issues related to te scale up o0 a CST! and de6iations 0rom te ideal CST! ill be in6estigate 0rom te experiment#