ITK-330Chemical Reaction Engineering

Introduction

Dicky Dermawanwww.dickydermawan.net78.net

dickydermawan@gmail.com

Introduction:Traditional “Process” Scheme

Chemical ReactorPretreatment Post treatment

Recycle

UtilityIncl. Waste Treatment

Raw Material Product

Waste

By product

PROCESS

References

Fogler HS, Elements of Chemical Reaction Engineering, 4th ed., Prentice (1999)

Levenspiel O, Chemical Reaction Engineering, 2nd ed., Wiley (1972)

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

Score & Grading 20 4 all homework & quiz 25 4 1st midterm exam 25 4 2nd midterm exam 30 4 final term examination

A 4 74.5 ++ B 4 59.5 ++ C 4 49.5 ++ D 4 39.5 ++

How 2 Master CRE

What will be important in the near future

CD Tour

Intro 2 Auxiliary: Computer Program MathCAD Polymat

Basic ConceptsBasic Concepts

ITK-330ITK-330Chemical Reaction Chemical Reaction

EngineeringEngineering

Dicky Dermawan

11Mole BalanceMole Balance

In – Out + Generation = In – Out + Generation = AccumulationAccumulation

Reactor Performance EquationReactor Performance Equation

Using Performance EquationsUsing Performance Equations::Sample Problem Sample Problem P1-12CP1-12C

The gas phase reaction: A The gas phase reaction: A B+C B+C

Is carried out isothermally in a 20 L constant-volume batch reactor. Twenty 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.moles of pure A is initially placed in the reactor. The reactor is well mixed.

a.a. If the reactor is first order: -rIf the reactor is first order: -rAA = k.C = k.CAA with k = 0.865 min with k = 0.865 min-1-1, calculate the , calculate the

time necessary to reduce the number of moles of A in the reactor to 0.2 time necessary to reduce the number of moles of A in the reactor to 0.2 molmol

b.b. If the reaction is second order:If the reaction is second order:

-r-rAA = k.C = k.CAA22 with k = 2 L.mol with k = 2 L.mol-1-1.min.min-1-1

calculate the time necessary to consume 19.0 mol of Acalculate the time necessary to consume 19.0 mol of A

c.c. If the temperature is 127If the temperature is 127ooC, what is the initial total pressure? What is the C, what is the initial total pressure? What is the final total pressure assuming the reaction goes to completion?final total pressure assuming the reaction goes to completion?

22Conversion & Reactor SizingConversion & Reactor Sizing

Conversion & Reactor Sizing:Conversion & Reactor Sizing:Batch SystemsBatch Systems

Batch reactor performance equationBatch reactor performance equation

fedA ofNumber

consumed)( reactedA of NumberA of Conversion

Moles of A consumed = Moles of A fed – Moles of A IN the reactorMoles of A consumed = Moles of A fed – Moles of A IN the reactor

0A

A0AA N

NNX

)X1(NN 0AA

dXNdN 0AA

Vrdt

dNA

A Vrdt

dXN A0A

dXVr

1Nt

A0A

Conversion & Reactor Sizing:Conversion & Reactor Sizing:Flow SystemsFlow Systems

PFR performance equationPFR performance equation

unit timeper fedA ofNumber

unit timeper consumed)( reactedA of NumberA of Conversion

0A

A0AA F

FFX

)X1(FF 0AA

dXFdF 0AA

AA r

dV

dF AA r

dV

dXF 0

dXr

1FV

A0APFR

CSTR performance CSTR performance equationequation

A

A0ACSTR r

FFV

A

0ACSTR r

XFV

Reactor Sizing:Reactor Sizing:Levenspiel’s PlotLevenspiel’s Plot

2

1

X

X A0APFR dX

r

1FV

A

120ACSTR r

XXFV

In order to size a reactor, all we need is the reactor type In order to size a reactor, all we need is the reactor type andand

relationship between –rrelationship between –rAA and X and X

In using these design equations, nothing needs to be In using these design equations, nothing needs to be assumed on when, where, or how the reaction is carried assumed on when, where, or how the reaction is carried

outout ……but the actual shape of the curve depends on but the actual shape of the curve depends on these these

Reactor in SeriesReactor in Series

2

1

X

X A0APFR dX

r

1FV

A

120ACSTR r

XXFV

Performance Equations in term of Performance Equations in term of ConversionConversion

Application of the conceptApplication of the concept::Sample Problem Sample Problem P2-6BP2-6B

The exothermic reaction: A The exothermic reaction: A B+C B+Cwas carried out adiabatically and the following data recorded:was carried out adiabatically and the following data recorded:

The entering molar flowrate of A was 300 mol/minThe entering molar flowrate of A was 300 mol/mina.a. What are the PFR and CSTR volumes necessary to achieve 40% conversion?What are the PFR and CSTR volumes necessary to achieve 40% conversion?b.b. Over what range of conversions would the CSTR and PFR volumes be Over what range of conversions would the CSTR and PFR volumes be

identical?identical?c.c. What is the maximum conversion that can be achieved in a 10.5 L CSTR?What is the maximum conversion that can be achieved in a 10.5 L CSTR?d.d. What conversion can be achieved if A 7.2 L PFR is followed in series by a 2.4 L What conversion can be achieved if A 7.2 L PFR is followed in series by a 2.4 L

CSTR?CSTR?e.e. What conversion can be achieved if a 2.4 L CSTR is followed in series by a 7.2 What conversion can be achieved if a 2.4 L CSTR is followed in series by a 7.2

L L f.f. Plot the conversion and rate of reaction a function of PFR reactor volume up to Plot the conversion and rate of reaction a function of PFR reactor volume up to

a volume of 10 La 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

Assignment:Assignment:

For the irreversible gas-phase reaction: A For the irreversible gas-phase reaction: A 2 B 2 Bthe following correlation was determined from laboratory data (the the following correlation was determined from laboratory data (the

initial concentration of A is 0.2 gmol/L): initial concentration of A is 0.2 gmol/L):

  The volumetric flow rate is 0,5 mThe volumetric flow rate is 0,5 m33/h. /h. a. Over what range of conversions are the plug-flow reactor and a. Over what range of conversions are the plug-flow reactor and

CSTR volumes identical? CSTR volumes identical? b. What conversion will be achieved in a CSTR that has a volume of b. What conversion will be achieved in a CSTR that has a volume of

90 L? 90 L? c. What plug-flow reactor volume is necessary to achieve 70% c. What plug-flow reactor volume is necessary to achieve 70%

conversion? conversion? d. What CSTR reactor volume is required if effluent from the plug-d. What CSTR reactor volume is required if effluent from the plug-

flow reactor in part (c) is fed to a CSTR to raise the conversion to flow reactor in part (c) is fed to a CSTR to raise the conversion to 90%? 90%?

e. If the reaction is carried out in a constant-pressure batch reactor 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 in which pure A is fed to the reactor, what length of time is necessary to achieve 40 % conversion? necessary to achieve 40 % conversion?

33Rate Law & Rate Law &

StoichiometryStoichiometry

Consideration…..Consideration…..

Reactor sizing can be carried out when the function Reactor sizing can be carried out when the function is available is available

This function, as depicted in Levenspiel Plot, is specifically This function, as depicted in Levenspiel Plot, is specifically dependent of reactor type & reaction conditions (temperature dependent of reactor type & reaction conditions (temperature profile, pressure, reactant ratio) and therefore limiting its useprofile, pressure, reactant ratio) and therefore limiting its use

From kinetic point of view:From kinetic point of view:

Since (batch) or (continue), and, from the definitions Since (batch) or (continue), and, from the definitions of conversion (batch) or (continue), of conversion (batch) or (continue), therefore therefore

Substitution of into Substitution of into results , which, on specific temperature profile givesresults , which, on specific temperature profile gives

The functions can be derived using the concept of The functions can be derived using the concept of stoichiometrystoichiometry

)X(rr AA

,...)C,C(fn)T(kr BAA

)X(gN 1A )X(gF 2A V

NC A

A

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

Stoichiometric TableStoichiometric Table

Taking A as basisTaking A as basis

ConsiderConsider D d cC bBaA

D C BA ad

ac

ab

Species Initially (mol)

Change (mol)

Remaining (mol)

A 0AN XN 0A XNNN 0A0AA

B 0BN XN 0Aa

b XNNN 0Aab

0BB

C 0CN XN 0Aa

c XNNN 0AaC

0CC

D 0DN XN 0Aa

d XNNN 0Aad

0DD

I (inerts) 0IN 0

0II NN

Totals 0TN XNNN 0A0TT

1ab

ac

ad

Xy1N

XNN

N

N0A

0T

0A0T

0T

T

X1N

N

0T

T

0Ay

T

jj N

Ny

Batch SystemsBatch Systems

Expressing ConcentrationsExpressing Concentrations

For Constant Volume SystemsFor Constant Volume Systems

)X1(CCV

XNN

V

NC 0AA

0

0A0AAA

)Xa

b(CC

V

XNa

bN

V

XNa

bN

V

NC B0AB

0

0A0AB

0

0A0BB

B

0A

0jj N

N

)Xa

c(CC C0AC

)Xa

d(CC D0AD

I0AI CC

)X(CC jj0Aj

V

NC j

j

Batch SystemsBatch Systems

Expressing ConcentrationsExpressing ConcentrationsFor Ideal Gas:For Ideal Gas:

T

T

P

P

X1

X1CC

)X1(TT

PP

V

)X1(N

V

NC 0

00AA

0

00

0AAA

T

T

P

P

X1

Xab

CC)X1(

T

T

P

PV

Xa

bN

)X1(T

T

P

PV

XNab

N

V

NC 0

0

B

0AB

0

00

B0A

0

00

0A0BB

B

T

T

P

P

X1

Xac

CC 0

0

C

0AC

T

T

P

P

X1

Xad

CC 0

0

D

0AD

T

T

P

P

X1CC 0

0

I0AI

T

T

P

P

X1

XCC 0

0

jj0Aj

V

NC j

j RT

pC

V

NTRNVp A

AA

AA

0T

T

0

00

00T00

T

N

N

T

T

P

PVV

TRNVP

TRNVP

X1T

T

P

PVV

0

00

RT

PyC A

A

Thus…Thus…

For Flow SystemsFor Flow Systems

V

FN

Thus…Thus…T

jj F

Fy 1a

bac

ad 0Ay

X1F

F

0T

T

0A

0jj F

F

For Constant FlowFor Constant FlowSystemsSystems )X(C

)X(FFC jj0A

0

jj0Ajj

RT

PyC j

j

X1

T

T

P

P

0

00

For Ideal Gas SystemsFor Ideal Gas Systems

T

T

P

P

X1

XC

TT

PP

)X1(

)X(FFC 0

0

jj0A

0

00

jj0jjj

Example of ExpressingExample of Expressing–r–rAA=r=rAA(X)(X)

Consider 2 SOConsider 2 SO22 + O + O22 > 2 SO > 2 SO33

The rate law: The rate law: –r–rAA = k.C = k.CSO2SO2.C.CO2O2

Taking SOTaking SO22 as basis: SO as basis: SO22 +1/2 O +1/2 O22 > SO > SO33

T

T

P

P

X1

X1CC

)X1(TT

P

P

)X1(FFC 0

00,SOSO

0

00

0,SOSOSO 22

22

2

T

T

P

P

X1

X21

CC)X1(

TT

P

P

X21

FF

C 0

0

O

0,SOO

0

00

O0,SOO

O

2

22

222

2

21

2111

––rrAA = =r = =rAA(X)(X)

––rrAA = k.C = k.CSO2SO2.C.CO2O2

2

0

2

02

O2

0,SOA T

T

P

P

X1

X21

X1Ckr

2

2

Example 3-8Example 3-8Calculating the Equilibrium ConversionCalculating the Equilibrium Conversion

The elementary gas-phase reversible decomposition of nitrogen tetroxide, The elementary gas-phase reversible decomposition of nitrogen tetroxide, NN22OO44, to nitrogen diokside, NO, to nitrogen diokside, NO22,,

NN22OO44 2 NO 2 NO22

Is to be carried out at constant temperature & pressure.Is to be carried out at constant temperature & pressure.

The feed consists of pure NThe feed consists of pure N22OO44 at 340 K and 2 atm. at 340 K and 2 atm.

The concentration equilibrium constant at 340 K is 0.1 mol/LThe concentration equilibrium constant at 340 K is 0.1 mol/L

a.a. Calculate the equilibrium conversion of NCalculate the equilibrium conversion of N22OO44 in a constant volume batch in a constant volume batch

reactorreactor

b.b. Calculate the equilibrium conversion of NCalculate the equilibrium conversion of N22OO44 in a flow reactor in a flow reactor

c.c. Express the rate of reaction solely as a function of conversion for a flow Express the rate of reaction solely as a function of conversion for a flow system and for a batch systemsystem and for a batch system

Explain why is the equilibrium conversion in (a) & (b) are differentExplain why is the equilibrium conversion in (a) & (b) are different

P3-14P3-14BB

Reconsider the decomposition of nitrogen tetroxide in Reconsider the decomposition of nitrogen tetroxide in Example 3-8. The reaction is to be carried out in PFR and 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.also in a constant-volume batch reactor at 2 atm and 340 K.

Only NOnly N22OO44 and an inert I are to be fed to the reactors. and an inert I are to be fed to the reactors.

Plot the equilibrium conversion as a function of inert mole Plot the equilibrium conversion as a function of inert mole fraction in the feed for both a constant-volume batch fraction in the feed for both a constant-volume batch reactor and a plug flow reactorreactor and a plug flow reactor