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8/10/2019 1-ITK-330 Introduction & Basic Concepts
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ITK-330
Chemical Reaction EngineeringIntroduction
Dicky Dermawanwww.dickydermawan.net78.net
http://www.dickydermawan.net78.net/mailto:[email protected]:[email protected]://www.dickydermawan.net78.net/8/10/2019 1-ITK-330 Introduction & Basic Concepts
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Introduction:Traditional Process Scheme
Chemical ReactorPretreatment Post treatment
Recycle
UtilityIncl. Waste
Treatment
Raw Material
Product
Waste
By product
PROCESS
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References
Fogler HS, Elements of Chemical Reaction
Engineering, 4thed., Prentice (1999)
Levenspiel O, Chemical Reaction
Engineering, 2nded., Wiley (1972)
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Material Covered by ITK-330
Fundamental understanding:
Mole Balance
Conversion & Reactor Sizing Rate Laws & Stoichiometry
Isothermal Reactor Design
More on..
Multiple Reaction
Steady State Heat Effect
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How 2 Master CRE
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What will be important in the near future
CD Tour
Intro 2 Auxiliary: Computer Program
MathCAD
Polymat
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Basic Concepts
ITK-330
Chemical Reaction Engineering
Dicky Dermawan
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1Mole Balance
In Out + Generation = Accumulation
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Reactor Performance Equation
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Using Performance Equations:
Sample Problem P1 12C
The gas phase reaction: A B+C
Is carried out isothermally in a 20 L constant-volume batch reactor. Twenty
moles of pure A is initially placed in the reactor. The reactor is well mixed.
a. If the reactor is first order: -rA= k.CAwith k = 0.865 min-1
, calculate thetime necessary to reduce the number of moles of A in the reactor to 0.2
mol
b. If the reaction is second order:
-rA= k.CA2with k = 2 L.mol-1.min-1
calculate the time necessary to consume 19.0 mol of A
c. If the temperature is 127oC, what is the initial total pressure? What is the
final total pressure assuming the reaction goes to completion?
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2Conversion & Reactor Sizing
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Conversion & Reactor Sizing:
Batch Systems
Batch reactor performance equation
fedAofNumber
consumed)(reactedAofNumberAofConversion
Moles of A consumed = Moles of A fedMoles of A IN the reactor
0A
A0AA
N
NNX
)X1(NN 0AA
dXNdN 0AA
Vrdt
dNA
A Vrdt
dXN A0A
dX
Vr
1Nt
A
0A
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Conversion & Reactor Sizing:
Flow Systems
PFR performance equation
unit timeperfedAofNumber
unit timeperconsumed)(reactedAofNumberAofConversion
0A
A0AA
F
FFX
)X1(FF
0AA
dXFdF 0AA
AA r
dV
dF
AA r
dV
dXF 0
dX
r
1FV
A
0APFR
CSTR performance equation
A
A0A
CSTR r
FF
V
A0ACSTR r
X
FV
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Reactor Sizing:
LevenspielsPlot
2
1
X
X A
0APFR dXr
1FV
A
12
0ACSTR r
XX
FV
In order to size a reactor, all we need is the reactor type and
relationship betweenrAand X
In using these design equations, nothing needs to be assumed onwhen, where, or how the reaction is carried out
but the actual shape of the curve depends on these
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Reactor in Series
2
1
X
X A
0APFR dX
r
1FV
A
120ACSTR
r
XXFV
P f E ti i t f
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Performance Equations in term of
Conversion
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Application of the concept:
Sample Problem P2 6B
The exothermic reaction: A B+C
was carried out adiabatically and the following data recorded:
The entering molar flowrate of A was 300 mol/min
a. What are the PFR and CSTR volumes necessary to achieve 40% conversion?
b. Over what range of conversions would the CSTR and PFR volumes be
identical?c. What is the maximum conversion that can be achieved in a 10.5 L CSTR?
d. What conversion can be achieved if A 7.2 L PFR is followed in series by a 2.4 LCSTR?
e. What conversion can be achieved if a 2.4 L CSTR is followed in series by a 7.2L
f. Plot the conversion and rate of reaction a function of PFR reactor volume up toa volume of 10 L
X 0 0.2 0.4 0.5 0.6 0.8 0.9
-rA [mol/(L.min] 10 16.67 50 50 50 12.5 9.09
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Assignment:
For the irreversible gas-phase reaction: A 2 B
the following correlation was determined from laboratory data (the initialconcentration of A is 0.2 gmol/L):
The volumetric flow rate is 0,5 m3/h.a. Over what range of conversions are the plug-flow reactor and CSTR
volumes identical?b. What conversion will be achieved in a CSTR that has a volume of 90 L
c. What plug-flow reactor volume is necessary to achieve 70%conversion?
d. What CSTR reactor volume is required if effluent from the plug-flowreactor in part (c) is fed to a CSTR to raise the conversion to 90%?
e. If the reaction is carried out in a constant-pressure batch reactor in
which pure A is fed to the reactor, what length of time is necessary toachieve 40 % conversion?
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3Rate Law & Stoichiometry
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Consideration..
Reactor sizing can be carried out when the function
is available
This function, as depicted in Levenspiel Plot, is specifically
dependent of reactor type & reaction conditions (temperature
profile, pressure, reactant ratio) and therefore limiting its use
From kinetic point of view:
Since (batch) or (continue), and, from the
definitions of conversion (batch) or
(continue), therefore
Substitution of intoresults , which, on specific temperature profile
gives
The functions can be derived using the concept of
stoichiometry
)X(rr AA
,...)C,C(fn)T(kr BAA
)X(gN 1A )X(gF 2AV
NC AA
AA
FC
)X(gCA
)X(gC jj
,...)C,C(fn)T(kr BAA )X,T(rr AA
)X(rr AA
....),X(gC),X(gC BBAA
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Stoichiometric Table
Taking A as basis
Consider DdcCbBaA
DCBA ad
a
c
a
b
Species Initially
(mol)
Change
(mol)
Remaining
(mol)
A0AN XN 0A XNNN 0A0AA
B0BN XN 0Aa
b XNNN 0Aab
0BB
C0CN XN 0Aa
c XNNN 0AaC
0CC
D0DN XN 0Aa
d XNNN 0Aad
0DD
I (inerts)0IN 0 0II NN
Totals0TN XNNN 0A0TT
1ab
ac
ad
Xy1
N
XNN
N
N0A
0T
0A0T
0T
T
X1N
N
0T
T
0Ay
T
j
j N
N
y
Batch Systems
NC
j
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Expressing Concentrations
For Constant Volume Systems
)X1(CCV
XNN
V
NC 0AA
0
0A0AA
A
)X
a
b(CC
V
XNa
bN
V
XNa
bN
V
NC B0AB
0
0A0AB
0
0A0BB
B
0A
0j
jN
N
)Xa
c(CC C0AC
)Xa
d(CC D0AD
I0AI CC
)X(CC jj0Aj
VC
j
j
Batch Systems
E i C t ti
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Expressing ConcentrationsFor Ideal Gas:
T
T
P
P
X1
X1CC
)X1(T
T
P
PV
)X1(N
V
NC 0
00AA
0
00
0AAA
T
T
P
P
X1
Xab
CC
)X1(T
T
P
PV
XabN
)X1(T
T
P
PV
XNabN
V
NC 0
0
B
0AB
0
00
B0A
0
00
0A0BB
B
T
T
P
P
X1
Xa
c
CC
0
0
C
0AC
T
T
P
P
X1
Xa
d
CC 0
0
D
0AD
T
T
P
P
X1CC 0
0
I0AI
T
T
P
P
X1
X
CC
0
0
jj
0Aj
V
NC
j
j RT
pC
V
NTRNVp AA
AAA
0T
T
0
0
000T00
T
N
N
T
T
P
P
VVTRNVP
TRNVP
X1TT
P
P
VV0
0
0
RT
PyC AA
Thus
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For Flow Systems
V
FN
Thus
T
j
jF
Fy 1
ab
ac
ad 0Ay
X1
F
F
0T
T
0A
0j
j F
F
For Constant Flow
Systems )X(C)X(FF
C jj0A0
jj0Aj
j
RT
PyC
j
j
X1
T
T
P
P
0
00
For Ideal Gas Systems
T
T
P
P
X1
XC
T
T
P
P
)X1(
)X(FFC 0
0
jj
0A
0
0
0
jj0jj
j
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Example of Expressing
rA=rA(X)
Consider 2 SO2+ O2> 2 SO3The rate law:rA= k.CSO2.CO2
Taking SO2as basis: SO2+1/2 O2> SO3
TT
PP
X1X1CC
)X1(T
T
P
P)X1(FFC 0
00,SOSO
0
00
0,SOSOSO 22
22
2
T
T
P
P
X1
X2
1
CC)X1(
T
T
P
P
X2
1F
F
C0
0
O
0,SOO
0
00
O0,SOO
O
2
22
22
2
2
21
2111
rA= =rA(X)
rA= k.CSO2.CO2
2
0
2
0
2
O2
0,SOAT
T
P
P
X1
X2
1X1
Ckr
2
2
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Example 3-8
Calculating the Equilibrium Conversion
The elementary gas-phase reversible decomposition of nitrogen tetroxide,
N2O4, to nitrogen diokside, NO2,
N2O42 NO2
Is to be carried out at constant temperature & pressure.The feed consists of pure N2O4at 340 K and 2 atm.
The concentration equilibrium constant at 340 K is 0.1 mol/L
a. Calculate the equilibrium conversion of N2O4in a constant volume batch
reactor
b. Calculate the equilibrium conversion of N2O4in a flow reactor
c. Express the rate of reaction solely as a function of conversion for a flow
system and for a batch system
Explain why is the equilibrium conversion in (a) & (b) are different
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P3-14B
Reconsider the decomposition of nitrogen tetroxide in Example
3-8. The reaction is to be carried out in PFR and also in a
constant-volume batch reactor at 2 atm and 340 K.
Only N2O4and an inert I are to be fed to the reactors.
Plot the equilibrium conversion as a function of inert mole
fraction in the feed for both a constant-volume batchreactor and a plug flow reactor