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I N S T R U C T O R :
E N G R . C A R E S S A M A R I E F R I A L - D E J E S U S
Chapter 9:Temperature and Pressure Effects
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Reactor design vs. T
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Reactor design vs. P
Constant volume batch reactor and ideal gas
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Finding the best reactor design based on T&P
3step procedure:
!st:Effects on the e"uilibrium composition# rate ofreaction and product distribution due to changes in
operating T and P .o Reactions sensitive to specific range of T and P $%rrhenius e"n
'nd:Effect of heat effects of chemical reactions on thetemperature of the reacting mi(ture
o
$e.g. Emulsification# e(othermic reaction ma) cause a runa*a)reaction if this e(ceeds a specific range of operating temperature
3rd:Economic considerationso Efficienc) $+ptimum reaction design vs. Cost
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,ingle Reactions
Concerned solel) on: Conversion level Reactor stabilit)
-ote: Product distribution is irrelevant.
From thermod)namics:
!. eat liberated or absorbed for a given e(tent ofreaction and#
'. /a(imum possible conversion
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eats of Reaction from Thermod)namics
eat of reaction# 0r -ature of the reacting s)stem %mount of material reacting and# Temperature and pressure of the reacting s)stem
or
1ata from tabulated heats of formation# 0f or heats of
combustion# 0c of the reacting materials
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eats of Reaction from Thermod)namics
2T! $usuall) 'oC
Reaction:
0r :heat transferred to the reacting s)stem *hen a
moles of % disappear to produce r moles of and s
moles of , *ith the s)stem at the sametemperature and pressure e!"re and a!terthe #han$e.
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eats of Reaction and Temperature
4) the of conservation of energ)
5n terms of enthalpies
5n terms of specific heats
*here
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eats of Reaction and Temperature
6hen
*e obtain
*here
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0r at various temperatures
E(ample 9.!
7asphase reaction at 'oC
6hat is the 0r at !8'oC 5s the reaction e(othermic
at that temperature
%verage Cp values bet*een 'oC and !8'oC are
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0r at various temperatures
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E"uilibrium constants from Thermod)namics
Real systems do not necessarily achieve the conversion by calculationsbased on thermodynamics. These are only suggested attainablevalues.
Revie* on 7ibbs free energ)
*here: f : fugacit) of the component at e"uilibrium conditions
f o: fugacit) of the component at the selected standard state temp T
∆G o: standard free energ) of a reacting compound $usuall) tabulated
: thermod)namic e"uilibrium constant
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E"uilibrium constants from Thermod)namics
,uggested standard states in choosing the follo*ingcomponents
7ases ; pure component at ! atm# at *hich pressure
ideal gas behavior is closel) appro(imated,olid ; pure solid component at unit pressure
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E"uilibrium constants from Thermod)namics
Revie*# the e"uilibrium constant
*here
%lso#
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E"uilibrium constants from Thermod)namics
7as reactions: 2! atm f o=po=1atm
For an) component 5 of an ideal gas
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E"uilibrium constants from Thermod)namics
For a solid component ta>ing part in a reaction ?ariation in fugacit) and pressure are small. Therefore#
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E"uilibrium Conversion
E"uilibrium composition E"uilibrium constant Changes in temperature
From thermod)namics# rate of change:
5ntegrating# 0r is constant
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E"uilibrium Conversion
6hen variation in 0r needs to be considered#
integrating
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E"uilibrium Conversion at 1ifferent Temperatures
E(ample 9.'
$a4et*een 8oC and !88oC determine the e"uilibrium conversionfor the elementar) a"ueous reaction
Present the results in the form of a plot of temperature versusconversion.
$b6hat restrictions should be placed on the reactor operatingisothermall) if *e are to obtain a conversion of @A or higher
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E"uilibrium Conversion at 1ifferent Temperatures
,olution: 6ith
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E"uilibrium Conversion at 1ifferent Temperatures
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E"uilibrium Conversion at 1ifferent Temperatures
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E"uilibrium Conversion
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E"uilibrium Conversion
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7eneral 7raphical 1esign Procedure
For an) single homogeneous reaction
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7eneral 7raphical 1esign Procedure
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7eneral 7raphical 1esign Procedure
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7eneral 7raphical 1esign Procedure
Reactor siBe for a given dut) and temperatureprogression:
!. 1ra* the reaction path on the % vs T plot.
'. Find the rates at various % along this path.3. Plot the lD$r % versus % curve for this path.
. Find the area under this curve $?DF %+.
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7eneral 7raphical 1esign Procedure
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7eneral 7raphical 1esign Procedure
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Construction of the $;riiT
E(ample 9.3 $p.'!@# inetics# find the rate e(pression for thisreaction and prepare the conversiontemperature
chart *ith reaction rate as parameter.
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Construction of the $;riiT Chart
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Construction of the $;riiT Chart
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Construction of the $;riiT Chart
%t tH! min# THGoC# % H8.!# %eH8.9
%t tH!8 min# TH'oC# % H8.G8# %eH8.99
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Construction of the $;riiT Chart
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Construction of the $;riiT Chart
6hat if e(ample 9.3 used a C,TR rather than a 4R
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Construction of the $;riiT Chart
%t tH! min# THGoC# % H8.!# %eH8.9
%t tH!8 min# TH'oC# % H8.G8# %eH8.99
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+ptimum Temperature Progression
Progression *hich minimiBes %&F AO for a given
conversion of reactant
5sothermal or nonisothermal
4R# PFR or series of C,TR 5deal for estimation of the real s)stem
5n an) t)pe of reactor: At any composition, it illalays be at the temperature here the rate isma!imum.
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+ptimum Temperature Progression
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eat Effects
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eat Effects
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%diabatic +perations
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%diabatic +perations
Enthalp) of entering feed:
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%diabatic +perations
Enthalp) of leaving feed:
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%diabatic +perations
Energ) absorbedDreleased b) the reaction:
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%diabatic +perations
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%diabatic +perations
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%diabatic +perations
For complete conversion:
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%diabatic +perations
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%diabatic +perations
6hen$
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,iBe of Reactor for %diabatic +perations
Plug flo* Tabulate the rate vs. % along the %+< Prepare the !D$r% vs % plot and integrate.
C,TR Jse the rate at the conditions *ithin the reactor
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,iBe of Reactor for %diabatic +perations
PFR
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,iBe of Reactor for %diabatic +perations
C,TR
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%diabatic +perations
Finding the best adiabatic operations ,hifting the operating line $changing the inlet temp to rates of
highest mean value.
For endothermic Hstarting at the highest allo*able tempFor e(othermic locating the locus of ma(imum rates *ith minimum ?DF %+
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%diabatic +perations
Finding the best reactor t)pe /inimiBes the ?DF %+ from % vs T
Plug flo* ; if rate progressivel) decreases *ith conversion$endothermic reaction and close to isothermal e(othermic reaction behavior
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%diabatic +perations
Finding the best reactor t)pe /inimiBes the ?DF %+ from % vs T
E(othermic reactions *ith large temp rise during reaction:
/i(ed flo* ; for small $pure gaseous reactantsPlug flo* ; for large $gas much inerts# or li"uid s)stems
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-onadiabatic +perations
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-onadiabatic +perations
6ith relativel) negligible difference of heat capacities
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-onadiabatic +perations
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E(othermic in C,TR
C,TR
%t lo* temp# rate is lo*# is lo*.
%t high temp# rises and approaches e"uilibrium.4e)ond e"iulibrium temp# decreases.
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E(othermic in C,TR
C,TR
%t lo* temp# rate is lo*# is lo*.
%t high temp# rises and approaches e"uilibrium.
4e)ond e"uilibrium temp# decreases.
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E(othermic in C,TR
5rreversible Reactions
insufficient heat liberated. -ot selfsustaining. Conversion is negligible.
more than enough heat liberated.
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E(othermic in C,TR
Reversible e(othermic reactions
,pecific range of temperature to maintain conversion
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Performance for the +ptimal Temperature Progression
Jsing the optimal temperature progression in a plug flo*reactor for the reaction of E(amples 9.' and 9.3#
$a calculate the space time and volume needed for 8Aconversion of a feed of " A, = 1### mol$min here % Ao = &
mol$liter.$b plot the temperature and conversion profile along the
length of the reactor.
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Performance for the +ptimal Temperature Progression
4asis: molD<
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Performance for the +ptimal Temperature Progression
1ra* the locus of ma(imum rates.
Ta>e note of the 9oC ma(imumallo*able temperature and 8Afeed conversion needed.
Ra(graph)
ra Xa 1/ra A
0.10 0.40 0.80 2.50 0.19
0.20 0.80 0.70 1.25 0.05
0.29 1.18 0.65 0.85 0.07
0.45 1.82 0.55 0.55 0.06
0.83 3.33 0.40 0.30 0.03
2.25 9.00 0.27 0.11
0.40
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Performance for the +ptimal Temperature Progression
9.88 8.'@ 8.!! 8.8Ra(grap
h) ra Xa 1/ra A
0.10 0.40 0.80 2.50 0.19
0.20 0.80 0.70 1.25 0.05
0.29 1.18 0.65 0.85 0.07
0.45 1.82 0.55 0.55 0.06
0.83 3.33 0.40 0.30 0.03
2.25 9.00 0.27 0.11
0.40
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Performance for the +ptimal Temperature Progression
9.88 8.'@ 8.!! 8.8Ra(grap
h) ra Xa 1/ra A
0.10 0.40 0.80 2.50 0.19
0.20 0.80 0.70 1.25 0.05
0.29 1.18 0.65 0.85 0.07
0.45 1.82 0.55 0.55 0.06
0.83 3.33 0.40 0.30 0.03
2.25 9.00 0.27 0.11
0.40
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Performance for the +ptimal Temperature Progression
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Performance for the +ptimal Temperature Progression
9.88 8.'@ 8.!! 8.8Ra(grap
h) ra Xa 1/ra A
0.10 0.40 0.80 2.50 0.19
0.20 0.80 0.70 1.25 0.05
0.29 1.18 0.65 0.85 0.07
0.45 1.82 0.55 0.55 0.06
0.83 3.33 0.40 0.30 0.03
2.25 9.00 0.27 0.11
0.40
!8A increments# %reaH8.8 %rea at % from 8.'@ to 8. is 8.83.
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Performance for the +ptimal Temperature Progression
+ ti C,TR Fl R t P f
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+ptimum C,TR Flo* Reactor Performance
% concentrated a"ueous %solution of the previous e(amples $C %+ H molDliter# "A, = 1### mol$min' is to be (#) converted in a mi!ed floreactor.
$a 6hat siBe of reactor is needed
$b 6hat is the heat dut) if feed enters at 'LC and product is to be
*ithdra*n at this temperature-ote that
+ ti C,TR Fl R t P f
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+ptimum C,TR Flo* Reactor Performance
4asis: molD<
+ ti C,TR Fl R t P f
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+ptimum C,TR Flo* Reactor Performance
C,TR operating point atpoint C.
+ ti C,TR Fl R t P f
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+ptimum C,TR Flo* Reactor Performance
%di b ti PFR P f
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%diabatic PFR Performance
Find the siBe of adiabatic plug flo* reactor to react thefeed of E(ample 9. $F %oH !888 molDmin and % Ao = &
mol$liter' to (#) conversion.
%di b ti PFR P f
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%diabatic PFR Performance
4asis: molD<
%di b ti PFR P f
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%diabatic PFR Performance
%diabatic PFR Performance
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%diabatic PFR Performance
%diabatic PFR Performance
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%diabatic PFR Performance
CSTR 'FR Opt(mum
!@'8 < '888 < 8' <
E( 9. E( 9.G E( 9.
%diabatic PFR *ith Rec)cle
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%diabatic PFR *ith Rec)cle
Ta>e the problem E(ample 9.G but no* allo* rec)cleto product stream.
$E(. 9.G:Find the siBe of adiabatic plug flo* reactor toreact the feed of E(ample 9. $F %oH !888 molDmin
and % Ao = & mol$liter' to (#) conversion.
%diabatic PFR *ith Rec)cle
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%diabatic PFR *ith Rec)cle
%diabatic PFR *ith Rec)cle
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%diabatic PFR *ith Rec)cle
/ultiple Reactions
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/ultiple Reactions
Reactor siBeProduct distribution
/anipulate temp:
+btain desirable product distribution
/a(imum desired product in a reactor *ith given
space time.
Product 1istribution and Temperature
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Product 1istribution and Temperature
Product 1istribution and Temperature
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Product 1istribution and Temperature
A high temperature favors the reaction of higher *,a lo temperature favors the reaction of loer *.
Product 1istribution and Temperature
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Product 1istribution and Temperature
For parallel reactions
5f E! M E' : high T
5f E! N E' : lo* T
Product 1istribution and Temperature
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Product 1istribution and Temperature
For series reactions
5f E! M E' : high T
5f E! N E' : lo* T
Product 1istribution and Temperature
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Product 1istribution and Temperature
For seriesparallel reactions
Construction of the $;riiT Chart
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Construction of the $ ri i T Chart
Jsing E(cel for
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Construction of the $;riiT Chart
/a>e sure to install ,olver in )our E(cel,et up e"uations
,et range $e.g. T
Jse ,olver
/a>e chart $tip: onl) use the data needed
Jsing E(cel for7raphing the +ptimum Path
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7raphing the +ptimum Path
Jsing the generate chart# find the ma(imum pointsfor each rates
/a>e another set of table for these data
7enerate curve from these data $ %
vs T
Compute for the !D$ri vs % data
7enerate curve from these data $!D$ri vs %
Jsing E(cel for7raphing the %diabatic +perating
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7raphing the %diabatic +perating e other lines in thegraph $trial and error to find the desired %+<
depending on the reactor scheme.
Jsing E(cel for7raphing the %diabatic +perating
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7raphing the %diabatic +perating