1-itk-330 introduction & basic concepts

8/10/2019 1-ITK-330 Introduction & Basic Concepts

1/28

ITK-330

Chemical Reaction EngineeringIntroduction

Dicky Dermawanwww.dickydermawan.net78.net

[email protected]
http://www.dickydermawan.net78.net/mailto:[email protected]:[email protected]://www.dickydermawan.net78.net/


2/28

Introduction:Traditional Process Scheme

Chemical ReactorPretreatment Post treatment

Recycle

UtilityIncl. Waste

Treatment

Raw Material

Product

Waste

By product

PROCESS


3/28

References

Fogler HS, Elements of Chemical Reaction

Engineering, 4thed., Prentice (1999)

Levenspiel O, Chemical Reaction

Engineering, 2nded., Wiley (1972)


4/28

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


5/28


6/28

How 2 Master CRE


7/28

What will be important in the near future

CD Tour

Intro 2 Auxiliary: Computer Program

MathCAD

Polymat


8/28

Basic Concepts

ITK-330

Chemical Reaction Engineering

Dicky Dermawan


9/28

1Mole Balance

In Out + Generation = Accumulation


10/28

Reactor Performance Equation


11/28

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?


12/28

2Conversion & Reactor Sizing


13/28

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


14/28

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


15/28

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


16/28

Reactor in Series

2

1

X

X A

0APFR dX

r

1FV

A

120ACSTR

r

XXFV

P f E ti i t f


17/28

Performance Equations in term of

Conversion


18/28

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


19/28

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?


20/28

3Rate Law & Stoichiometry


21/28

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


22/28

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


23/28

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


24/28

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


25/28

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


26/28

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


27/28

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


28/28

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

1-itk-330 introduction & basic concepts

Documents